CHEMISTRY 20 - Science with Mr. Dan



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|CHEMISTRY 20 |

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|Notes and problems |

|Unit 4: Acids and Bases |

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|[pic] |

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|pH = -log [H3O+(aq)] |

|pOH = -log [OH-(aq)] |

|pH + pOH = 14 |

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|Prepared by Daniel Veraart |

|CIS Abu Dhabi |

Chemistry 20

Day 29

Date: ________________________ Name: __________________________

Empirical Definitions of Acids and Bases:

ACIDS

Names for acids refer to aqueous solutions of the pure substance.

For example: HCl(g) is called hydrogen chloride while the aqueous HCl(aq) is hydrochloric acid.

The most common acids are given on P.11 of your booklet. There are two types of acids:

1. Strong acid: The first 6 acids of the table: HCl , HBr , HI, H2SO4, HNO3 and HClO4.

2. Weak acids: All the other acids of the table. (CH3COOH , HOOCCOOH , …).

To find if an acid is strong or weak, we can check the conductivity of the solution

- If the solution conducts electricity greatly ( Strong acid

- If the solution conducts electricity slightly ( Weak acid

BASES: The common bases are positive ions bonded to hydroxide ions (OH-). When bases dissolve in water, they dissociate to produce a metallic ion and the hydroxide ion.

Properties of acids and bases

|Properties |Acids |Bases |

|Taste | | |

|Color with litmus | | |

|Reaction with metals | | |

|PH | | |

|Neutralize what? | | |

|Conductivity | | |

|Color with phenolphtalein | | |

|Color with bromothymol blue | | |

|Feel | | |

Common Acids and bases:

|ACIDS |

|Products |Acids in the product |

| |Acetic acid = CH3COOH |

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| |Salicylic acid = C6H4(OH)COOH |

| |Carbonic acid = H2CO3 |

| |Phosphoric acid = H3PO4 |

| |Citric acid = C6H8O7 |

| |Ascorbic acid = C6H8O6 |

|BASES |

|Products |Bases in the product |

| |Sodium hydroxide = NaOH |

| |Magnesium hydroxide = Mg(OH)2 |

| |Ammonia = NH3 |

The pH

Chemistry 20

Homework 29

Date: ________________________ Name: __________________________

Exercices

1. Classify the following solutions as acids, bases or neutral.

a) bleach, pH = 12.4: _______ b) urine, pH = 6.0 : ________ c) coffee, pH = 5.0: _______

d) sugar water, pH = 7.0 : _______ e) egg white, pH = 7.8 : ________

2. Which of the following substance would turn litmus red?

A. Water B. Ammonia C. Pop D. Bleach

3. Mr. Clean probably has a pH

A. of 7 B. of 0 C. lower than 7 D. greater than 7

4. The pH of blood is 7.4 and the pH of urine is 5.4. Which of the following statement is true?

A. Blood is more basic than urine B. Blood is more acidic than urine

C. Both blood and urine would turn red litmus blue D. Both blood and urine are examples of acids.

5. A teacher gives you an unknown substance, how could you identify if this substance is acidic, basic or neutral?

A. By tasting it

B. By testing if the substance is corrosive

C. By putting the substance in water and testing it with an universal indicator

D. By looking at the substance, acids are colourless solutions while bases are white solids

6. Which of the following properties does not apply to a base?

A. pH greater than 7 B. React with magnesium

C. Turn red litmus blue D. Can be neutralised with vinegar

7. When a pool manager tested the water with blue litmus, it turned pink. In order to neutralize the water in the pool, the pool manager should add

A. hydrochloric acid diluted (acid) B. sodium carbonate diluted (base)

C. distilled water (neutral) D. chlorine (disinfectant)

8. After using an oven cleaner, some people rinse the oven with a dilute solution of vinegar. What is the purpose of the vinegar rinse?

A. To change the smell of the oven B. To clean what the oven cleaner wasn’t able to clean

C. To produce a salt D. To neutralize the oven cleaner that remains in the oven

9. Which of the following properties does not apply to an acid?

A. pH greater than 7 B. Sour taste

C. Turn blue litmus red D. Can be neutralised with baking soda

10. Hydrogen is produced when magnesium reacts with

A. CH3OH(aq) B. C2H5OH(aq) C. CH3COOH(aq) D. C6H12O6(aq)

11. An acidic solution

A. does not conduct electricity B. reacts with zinc

C. neutralizes CH3COOH(aq) D. taste bitter

12. Which of the following substance would turn litmus blue?

A. Water B. Hydrochloric acid C. Lemon juice D. Bleach

Use the following information to answer the next two questions

13. The basic solution is

A. Solution 1 B. Solution 2 C. Solution 3 D. Solution 4

14. The student made an error in its observation for

A. Solution 1 B. Solution 2 C. Solution 3 D. Solution 4

15. True or False. Justify the false statements.

A. _________: Soap is an example of base.

B. _________: Lemon juice tastes bitter.

C. _________: A solution of vinegar has a pH of approximately 0.

D. _________: A solution of baking soda taste bitter because it’s pH is lower than 7.

E. _________: The solution we find in a car battery would react with magnesium.

F. ________: Aspirin is an acid and would then turn bromothymol blue to yellow.

G. _______: Litmus paper can help you finding the exact pH a solution.

H. ________: Many household cleaners would react with magnesium.

I. ________: A pH of 9 is more acidic than a pH of 5.

J ________: A solution with a pH of 5.2 is considered very acidic.

K. ________ : Concentrated acids and bases are corrosive.

L. _______: A solution of vinegar is a strong acid.

M. _______: A solution with a pH of 4 is more acidic than a solution with a pH of 2.

Launch Lab

The colour of your breath

Introduction: Bromothymol blue is an acid-base indicator used to test if a substance is neutral, basic or acidic. In this lab, we will try to find out if your breath is neutral, basic or acidic.

Materials:

- Bromothymol blue - NaOH(aq) - Straw -Erlenmayer

- Stopwatch

Procedure:

1. Add 100 mL of distilled water in the Erlenmayer flask. Add five drops of bromothymol blue. Record the color.

2. Add drops of NaOH(aq), swirling the solution after each addition, until the solution turns blue (it might be after one drop).

3. Start the stopwatch. Using the straw, blow into the solution (pick the student with the worst breath) until the solution changes color.

4. Record how long it takes for a color change to occur.

5. Repeat steps 2, but hold your breath for 30-45 s before step 3.Record time to change color.

Analysis:

1. Make a table of observations.

2. Based on your prior knowledge, what type of substance was produced when you blew into the solution. Explain your answer.

3. How did holding your breath for 30-45 seconds affect your observations, if at all?

Chemistry 20

Day 34

Date: ________________________ Name: __________________________

|How can we measure the pH? |

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|We can measure the pH of a solution using a pH meter or a universal indicator. |

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|pH meter: Electronic device used to measured with precision the pH of a solution. |

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|Universal indicator: A universal indicator is a mixture of several indicators that turns a different colour for each number on |

|the pH scale. It is usually sold as a roll of paper and is cheaper than a pH meter. |

Lab #2

Finding the pH of acids and bases

Problem: Using a pH meter and a universal indicator to find the pH of 10 solutions.

Design: Test all solutions for the pH with the pH-meter and the universal indicator. Record observations in the table below.

|Solution |pH with pH-meter |pH with universal indicator |

|Tide | | |

|Cream of tartar | | |

|Aspirin | | |

|Baking soda | | |

|Antacid | | |

|Vinegar | | |

|Drain cleaner | | |

|Rubbing alcohol | | |

|Ammonia | | |

Lab #3

Purple cabbage as a Universal indicator

Problem: Using purple cabbage as a universal indicator

Design: Prepare 11 solutions with pH between 2 to 12 and add cabbage solution to them.

Keep a sample of each solution. Test the 4 unknown solutions for the pH. Record observations in the tables below.

|PH |Color of solution |

|2 | |

|3 | |

|4 | |

|5 | |

|6 | |

|7 | |

|8 | |

|9 | |

|10 | |

|11 | |

|12 | |

|Solution |Color of solution |pH of the solution |

|1 | | |

|2 | | |

|3 | | |

|4 | | |

Chemistry 20

Day 30

Date: ________________________ Name: __________________________

Acids and Bases in Solution

Svante Arrhenius (1859-1927) was one of pioneer in the study of acids and bases. He won a Nobel prize in 1913 for Chemistry for his work.

Arrhenius’s explanation of the properties of acids and bases is the Arrhenius’s theory of acids and bases.

|Arrhenius Theory of Acids and Bases |

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|An Arrhenius acid is a substance that ionizes to form hydrogen ion (H+) concentration in aqueous solution. |

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|Ex. : HCl(g) ( HCl(aq) ( H+(aq) + Cl-(aq) |

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|An Arrhenius base is a substance that dissociates to produce hydroxide ion (OH-) in aqueous solution. |

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|Ex. : NaOH(s) ( NaOH(aq) ( Na+(aq) + OH-(aq) |

The hydrogen ion is really only a proton (with no electron). If such a particle comes near polar water molecules, it is likely to bond strongly to it and become what we call a hydronium ion.

H+(aq) + H2O(l) ( H3O+(aq)

Using the Arrhenius theory, we could infer that acids must contain a source of H+(aq) and bases must contain a source of OH-(aq).

Examples

Classify the following solutions as acidic, basic, or neutral.

a) HNO3(aq) : ____________ b) Ca(OH)2(aq) : ____________

c) HBr(aq) : ____________ d) LiOH(aq) : ____________

e) NaCO3(aq) : ____________ f) NH3(aq) : ____________

Does the Arrhenius theory successfully predict acidic or basic properties in all cases?

New and improved Arrenius’ definitions

Evidence from the examples above indicates the limited ability of Arrhenius's theory to predict acidic or basic properties of a substance in aqueous solution.

Only four substances followed the definition: HNO3 (aq), HBr (aq), Ca(OH)2 (aq) and LiOH(aq)

The other substances did not follow that definition; therefore, the Arrhenius’s definitions of acids and base needed to be revised.

| A modified Arrhenius theory |

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|An Arrhenius acid reacts with water to produce hydronium ions H3O+(aq) in aqueous solutions. |

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|Examples: HCl(aq) + H2O(l) ( H3O+(aq) + Cl-(aq) |

|CH3COOH(aq) + H2O(l) ( H3O+(aq) + CH3COO-(aq) |

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|An Arrhenius base dissociates or reacts with water to produce hydroxide ions OH-(aq) in aqueous solutions. |

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|Examples: NaOH(s) ( Na+(aq) + OH-(aq) |

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Example #1: Ammonia is a base because of the reaction of ammonia with water that produces the hydroxide ion.

NH3(aq) + H2O(l) ( NH4+(aq) + OH-(aq)

Example #2: Sodium carbonate in water produce a basic solution:

First, sodium carbonate dissociate: Na2CO3(s) ( 2 Na+(aq) + CO32-(aq)

Second, the carbonate ion reacts with water: CO32-(aq)+ H2O(l) ( OH-(aq) + HCO3-(aq)

Example #3: Sodium hydrogen sulfate in water produces an acidic solution:

First, sodium hydrogen sulfate dissociate: NaHSO4(s) ( Na+(aq) + HSO4-(aq)

Second, the hydrolysis: HSO4-(aq)+ H2O(l) ( H3O+(aq) + SO42-(aq)

Example #4: Carbon dioxyde in water produces an acidic solution:

First, carbon dioxyde reacts with water: CO2(s) + H2O(l) ( H2CO3(aq)

Second: H2CO3(aq)+ H2O(l) ( H3O+(aq) + HCO3-(aq)

Exercises:

1. Explain why the following substances are considered as acids or bases (According to Arrhenius)

a) Na3PO4(s), produces a solution with a pH = 11 when dissolved in water.

b) NH4Cl(s) produces a very weak acidic solution when dissolved in water.

c) Baking soda produces a very weak basic solution when dissolved in water.

d) Nitric acid is a very acidic solution.

Chemistry 20

Homework 30

Date: ________________________ Name: __________________________

Exercises:

1. Write a chemical equation to show how the following acids would react in water, according to the modified Arrhenius theory of acids and bases.

a) HCl(aq)

b) NH4Cl(aq)

c) NaHSO4(aq)

d) H2SO3(aq)

2. Write a chemical equation to show how the following bases would dissociate or react in water, according to the modified Arrhenius theory of acids and bases.

a) Ca(OH)2(aq)

c) Na3PO4(s)

b) NaS2 (aq)

c) LiOH(aq)

Chemistry 20

Day 31

Date: ________________________ Name: __________________________

Strong and Weak Acids and Bases

According to the modified Arrhenius theory of acids and bases, all acids produce hydronium ions in water and all bases produce hydroxide ions in water. Not all acids, however ionize to the same degree.

|Strong acid |

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|Strong acid: An acid that ionizes nearly 100% in water. |

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|For example: HCl(g) + H2O(l) ( H3O+(aq) + Cl-(aq) (100% reaction) |

|Weak acid |

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|Weak acid: An acid that reacts very little in water. Only a small percentage of the acid molecule form ions in water. |

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|For example: CH3COOH(g) + H2O(l) (( H3O+(aq) + CH3COO-(aq) (1% reaction) |

Notice the double arrow-headed equilibrium arrow in the equation above. This arrow indicates that the solution is in equilibrium.

( The acid molecules are constantly reacting with water to form the ions and

the ions are constantly reacting to form the acid molecules and water.

|Strong base |

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|Strong base: A strong base dissociate completely into ions in water. All oxides and hydroxides of alkali metals and Earth alkali metals are strong bases. |

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|For example: NaOH(s) ( Na+(aq) + OH-(aq) (100% reaction) |

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|Weak base |

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|Weak base: A weak base is a substance that reacts very little in water to produce a very small amount of hydroxide ions. |

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|For example: NH3(g) + H2O(l) (( NH4+(aq) + OH-(aq) (1% reaction) |

[pic]

Only about 1% of ammonia molecules react in water to produce OH-(aq). In a 0.10 mol/L solution of ammonia, the concentration of OH-(aq) is only about 0.0010 mol/L.

Chemistry 20

Homework 31

Date: ________________________ Name: __________________________

Exercises:

1. Classify the following as neutral ionic, molecular, strong acid, weak acid, strong base or weak base.

a) C6H5COOH: ______________ b) HF : ______________

c) NH3 : _____________ d) Na2CO3 : ________________

e) KOH : ___________________ f) Mg(OH)2 : _________________

g) NaCl : ____________________ h) Na3PO4 : __________________

i) HCl: ____________________ j) NH4Cl(aq) : __________________

k) NaHSO4(aq) : ________________ l) HNO3(aq) : __________________

Chemistry 20

Day 32

Date: ________________________ Name: __________________________

Communicating concentration: pH and pOH

In 1909 a chemist, Soren Sorenson, developed a simplified system for referring to the degree of acidity of a solution. He used the term pH for power of hydrogen. pH refers to the concentration of hydronium ions in solution.

[H3O+(aq)] ranges from about 10.0 mol/L down to 1.0 x 10-15 mol/L in common aqueous solutions. A range on the order of a quadrillion to one can only be expressed by using logarithm. Expressed as a numerical value without units, the pH can be calculated using the following formula:

pH = - ( log10 [H3O+(aq)] )

If you know the pH of a solution, you can calculate the [H3O+(aq)] using the following formula:

[H3O+(aq)] = 10-pH

Although pH is used in most applications, in some applications it may be convenient to describe hydroxide ion concentration in a similar way. The definition of pOH follows the same format and the same rule as for pH

pOH = - ( log10[OH-(aq)] )

[OH-(aq)] = 10-pOH

The mathematics of logarithms allows us to express a simple relationship between pH and pOH

pH + pOH = 14

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|Summary : Formulas to be memorized |

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|pH = - ( log10 [H3O+(aq)] ) |

|[H3O+(aq)] = 10-pH |

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|pOH = - ( log10[OH-(aq)] ) |

|[OH-(aq)] = 10-pOH |

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|pH + pOH = 14 |

Examples :

1. Calculate the pH of a sample of acid rain in which [H3O+(aq)] = 1.2 x 10-4 mol/L

2. Find [H3O+(aq)] in a bottle of pop that has a pH of 2.1

3. Find the pH of a 0.0060 mol/L KOH solution

4. Find [OH-(aq)] in solution with a pH of 12.9

6. A student dissolves 1.55 g of NaOH in 500 mL of water. What is the pH of the solution?

7. A student want to prepare a 1.00 L of a solution with a pH =1.4 . What volume of concentrated (12.4 mol/L) hydrochloric acid must be used?

Chemistry 20

Homework 32

Name: ____________________________ Date: __________________________

Exercises

1. Find the pH of the following solutions

a) Solution with [H3O+(aq)] = 1.00 x 10-6 mol/L : pH = _________

b) Solution with [H3O+(aq)] = 1.50 x 10-2 mol/L : pH = _________

c) Solution with [OH-(aq)] = 1.00 x 10-6 mol/L : pH = _________

d) Solution with [H3O+(aq)] = 0.00150 mol/L : pH = _________

2. Find the pH of lime juice if [H3O+(aq)] = 0.0120 mol/L? _____________

3. Find the pH of blood if [OH-(aq)] = 2.6 x 10-7 mol/L? ______________

4. Find the pH of a solution made of 1.00 g of KOH in 1.00 L of water? Show your work.

5. Classify the following substances from the least acidic to the most acidic.

Solution A : pH = 6 Solution B : [H3O+(aq) ] = 1.0 x 10-4 mol/L

Solution C : [OH-(aq)] = 1 x 10-13 mol/L Solution D : pH 9

________ ________ ________ _________

Least Most

7. What mass of potassium hydroxide is contained in 500 mL of solution that has a pH of 11.5? Show your work.

8. A student make a solution in which [H3O+(aq)] = 1.0 x 10-3 mol/L. This solution would

A. be green in bromothymol blue B. be pink in phenolphtalein

C. turn litmus red D. have a pOH of 3

9. Hydrogen is produced when magnesium reacts with

A. CH3OH(aq) B. C2H5OH(aq) C. CH3COOH(aq) D. C6H12O6(aq)

10. A student wants to clean the spill of a car battery. Which household substance should be used?

A. Water B. Vinegar C. Lemon juice D. Baking soda

11. Which of the following substance is a base

A. HOOCCOOH(aq) B. Ba(OH)2 (aq) C. CH3OH(aq) D. NH4+(aq)

12. What is the pH of a 0.0010 mol/L LiOH (aq) solution?

A. 3.0 B. 7.0 C. 10 D. 11

13. An acidic solution

A. does not conduct electricity B. reacts with zinc

C. neutralizes CH3COOH(aq) D. taste bitter

14. A 0.0300 mol/L HCl(aq) has a pH of

A. 2.48 B. 2.00 C. 1.52 D. 0.480

15. If the pH of a solution is 8.0 ,

A. [H3O+(aq)] > [OH-(aq)] B. [OH-(aq)] > 1.0 x 10-7 mol/L

C. [OH-(aq)] = 1.0 x 10-8 mol/L D. [H3O+(aq)] = 8,0 mol/L

16. A student find the pH of a fruit juice to be 2.4 . The [H3O+(aq)] of this juice is

A. 4.0 x 10-3 mol/L B. 2.5 x 10-8 mol/L C. 3.8 x 10-1 mol/L D. 2.5 x 10-18 mol/L

17. A sodium hydrogen carbonate solution has a pH of 8.0 , [OH-(aq)] is

A. 1.0 x 10-13 mol/L B. 1.0 x 10-8 mol/L C. 1.0 x 10-6 mol/L D. 1.0 x 10-5 mol/L

Chemistry 20

Day 33

Date: ________________________ Name: __________________________

Acid-Base Indicators

|Acid-Base Indicators |

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|Acid-base indicators are substances, which have one color in acidic solutions and another color in basic solutions. |

|The color change for each indicator is related to specific pH values |

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|List of indicators : Data booklet P. 10 |

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|Indicators can be use to find: |

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|1. the approximate pH of a solution. |

|2. the equivalence point for the neutralization reaction. |

Example #1: Complete the following table : Find the color of the following indicators .

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|pH of solutions |Bromothymol |Methylorange |Phenolphtalein |Cresol red |Thymol blue |

| |Blue | | | | |

|1 | | | | | |

|2 | | | | | |

|3 | | | | | |

|4 | | | | | |

|5 | | | | | |

|6 | | | | | |

|7 | | | | | |

|8 | | | | | |

|9 | | | | | |

|10 | | | | | |

|11 | | | | | |

|12 | | | | | |

|13 | | | | | |

Example #2:

A solution is yellow with methylorange and red with methyl red. What is the approximate pH of this solution?

Example #3:

|Colors of an acid with different indicators. |

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|Test tubes Indicator Color |

|1 Orange IV Yellow |

|2 Methyl orange Yellow |

|3 Bromocresol green Blue |

|4 Methyl red Orange |

|5 Bromothymol blue Yellow |

The approximate pH of the solution is between ______________________

Example #4:

Four unknown solutions labelled I, II, III and IV were tested and these data were obtained:

Indicator I II III IV

Thymol blue green yellow green orange

Methyl orange yellow orange yellow red

Thymolphtalein colorless colorless blue colorless

The acidic solution(s) is/are _________________

Lab #6

pH of solutions

Problem : Find the pH of 4 solutions using only indicators.

Design: Find the approximate pH using the following indicators:

Acidic range: Bromophenol blue – Methyl red

Neutral range: Bromothymol blue

Basic range: Phenol red – Phenolphtalein.

Compare with the real pH given by your teacher.

Questions

1. Make a table of observation.

Lab #7

Prepare solutions with specific pH

Problem : To prepare an acidic and a basic solution with a specific pH from a potassium hydroxide and a 0.6 mol/L HCl solution.

Materials : - Scale - Volumetric flask - Solid KOH 0.6 mol/L HCl

Design:

Calculate the mass of solid potassium hydroxide needed to make a solution with a specific pH given by your teacher. Add the solid to a known volume of water. Mix and record the pH with a pH-meter.

pH = __________ Volume = _________

Calculate the volume of 0.6 mol/L HCl needed to make a solution with a specific pH given by your teacher. Add the acid to a known volume of water. Mix and record the pH with a pH-meter.

pH = __________ Volume = _________

Questions

1. Calculate the mass of base needed.

2. Calculate the volume of 0.6 mol/L HCl needed.

3. Make a table of observations.

4. Calculate the percent of error for each solution.

Chemistry 20

Homework 33

Name: _____________________ Date: _________________

2. If we add a base to a solution,

A. [H3O+(aq)] decreases and pH increases B. [H3O+(aq)] decreases and pH decreases

C. [H3O+(aq)] increases and pH increases D. [H3O+(aq)] increases and pH decreases

3. Phenolptalein would be pink in which of the following solutions?

A. [OH-(aq)] = 1.0 x 10-3 mol/L B. [H3O+(aq)] = 1.0 x 10-4 mol/L

C. [H3O+(aq)] = 1.0 x 10-5 mol/L D. [OH-(aq)] = 1.0 x 10-11 mol/L

4. If a solution easily conducts electricity and turns blue litmus red, the solution is probably

A. HNO 3(aq) B. NaCl (aq) C. Ba(OH) 2(aq) D. CH3COOH (aq)

|Colors of an acid with different indicators. |

|Test tubes Indicator Color |

|1 Orange IV Yellow |

|2 Methyl orange Yellow |

|3 Bromocresol green Blue |

|4 Methyl red Orange |

|5 Bromothymol blue Yellow |

5. The approximate pH of the solution is between

A. 3.0 and 4.0 B. 4.0 and 5.0 C. 5.0 and 6.0 D. 6.0 and 7.0

6. A student make a solution in which [H3O+(aq)] = 1.0 x 10-3 mol/L. This solution would

A. be green in bromothymol blue B. be pink in phenolphtalein

C. turn litmus red D. have a pH of 4

7. The indicator bromothymol blue would be green in a solution with

A. pH = 1 B. pH = 7 C. pH = 10 D. pH = 14

Use the following information to answer the following question

|Colour of an unknown solution with different indicators |

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|Methyl violet is Blue Phenol Red is Red |

|Indigo carmine is Blue Phenolphtalein is colorless |

8. The approximate pH of the solution is _______

9. Four unknown solutions were tested with different indicators.

Solution Observations

1 Methyl orange was orange

2 Thymolphtalein and indigo carmine were blue

3 Litmus was blue and phenolphtalein was colourless

4 Bromocresol green was blue and bromothymol blue was yellow

The solutions from the most basic to the most acidic are respectively:

, , , ______

Chemistry 20

Day 39

Date: _____________________ Name: _________________________

Chemical analysis by titration

Titration is a common experimental design in chemistry used to determine the concentration of a substance in solution.

Titration involves the carefully measured and controlled addition of a solution from a buret into a measured volume of a sample solution until the reaction is judged to be completed.

Buret: A buret is a precisely marked glass cylinder with a stopcock at one end. It measures a volume of reacting solution.

The solution in the buret known as the titrant is added to the sample until the reaction is complete.

An indicator is used in all acid-base titration. The color change of the indicator indicates the end of the reaction.

|Some Definitions |

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|Titration: It’s a progressive transfer of a solution from a buret into a measured volume of a sample solution. It is used to determine the|

|concentration of a solution. |

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|Endpoint: The completion of the reaction is indicated by a sudden color change of an indicator. This is referred as the endpoint of the |

|titration. |

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|Equivalence point: The measured quantity of titrant added when the endpoint occurs is called the equivalence point. |

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|Standard solution: Solution used in the buret. Standard solutions are solutions with precisely known concentrations. |

A titration analysis should involve several trials, using different samples of the unknown solution to improve the reliability of the answer. A typical requirement is to repeat measurements until three trial results within 0.2 mL (and then take the average).

Titration is a good example of a chemical technology that is reliable, economical and simple to use.

Lab #11

Titration Analysis of Vinegar

Problem: What is the concentration of acetic acid (CH3COOH(aq)) in a sample of vinegar? You will determine the amount of acetic acid in white vinegar titration with a solution of NaOH whose concentration is known. The indicator will be phenolphthalein

Materials: Buret Strirrer Erlen-mayer

Graduated cylinder Waste beaker Scale

Sodium hydroxide

Vinegar

Procedure:

1. Prepare 100 mL of a standard 1.00 mol/L solution of NaOH(aq).

2. Fill the buret with the standard solution.

3. Add 25 mL of vinegar to the Erlen-mayer. Add 10 drops of phenolphthalein.

4. Start the titration until the indicator changes color.

5. The titration is repeated until three consistent results are obtained (within 0.2 mL)

If you read the label on the vinegar bottle, the concentration of acetic acid is given in

percent (by weight) and not in molarity. But since we have calculated the mass of acetic

acid, we can calculate the mass percent if we know the mass of vinegar we used in the

titration. Vinegar is mainly water (with a little acetic acid in it), so we'll assume that the

vinegar has the same density as pure water, that is, 1.0 mL of acetic acid has the

mass of 1.0 grams.

Mass percent = 100% x (mass of acetic acid/mass of vinegar)

Observations:

| |Titration #1 |Titration #2 |Titration #3 |Titration #4 |

| | | | |(if needed) |

|Volume of Vinegar | | | | |

|Molarity of NaOH | | | | |

|Initial Buret Reading | | | | |

|Final Buret Reading | | | | |

|Volume of NaOH Added | | | | |

Questions

1. What mass of sodium hydroxide is required to make 100 mL of the standard solution.

2. Calculate using stoichiometry the concentration of acetic acid in the sample.

3. Calculate your percent of error.

Calculations page

Chemistry 20

Day 34

Date: _____________________ Name: _________________________

Acid Base Stoichiometry

An acid-base titration problem is essentially a stoichiometric problem between an acid and a base. An acid-base titration is a complete chemical reaction between an acid and a base. The products of an acid-base titration are always the same: Water and a salt.

| The four steps of stoichiometric calculations |

| |

|Write a balanced chemical equation for the reaction and determine the two substances involved in the reaction, the given and the unknown will |

|often be the acid and the base. |

| |

|2. Find the number of moles of the given substance using the following formulas: |

| |

|n = m (If a mass is given) n = C . V (If a solution is given) |

|M |

| |

|3. Find the molar ratio between the given and unknown substances using the chemical equation. This will give you the number of moles of the |

|unknown substance. |

| |

|Number of moles = Unknown |

|Given |

| |

|4. Answer the question by using the number of moles found in step #3 and one of the following formulas: |

| |

|m = n.M or C = n / V or V = n / C or V = nRT/P |

Examples:

1. A student titrates 25.0 mL of NaOH solution with 0.100 mol/L HCl until the endpoint was reached. These are the result recorded by the student:

Initial buret reading: 0.600 mL

Final buret reading: 16.3 mL

Find the concentration of NaOH in this solution.

2. During a titration, 5.00 g of NaOH solid are neutralized with 150 mL of H2SO4(aq) . What was the concentration of the acid?

3. 50.0 mL of a Mg(OH)2(aq) solution is titrated with 22.4 mL of a 0.100 mol/L HCl until the endpoint is reached. Find the concentration of Mg(OH)2(aq) .

4. 1.59 g of sodium carbonate solid was added to an Erlenmayer flask and titrated with diluted HCl(aq). The titration evidence collected is shown below

Trial 1 2 3 4

Final buret reading 13.3 26.0 38.8 13.4

Initial buret reading 0.2 13.3 26.0 0.6

The concentration of the diluted HCl(aq) Is ___________ mo/L.

Chemistry 20

Homework 34

Name: ____________________________ Date: __________________________

Exercises

1. 10.0 mL of 0.400 mol/L KOH(aq) were used to titrate 40.0 mL of HCl(aq).

Find the concentration of the HCl(aq).

2. Lise needed 2.23 g of NaOH(s) to neutralize a 50.0 mL sample of sulfuric acid. What was the molar concentration of the acid?

3. If 22.4 mL of a 0.100 mol/L HBr(aq) solution are required to neutralize a 0.200 mol/L Ca(OH)2(aq) solution, what volume of base was used?

4. A student wants to find the concentration of the vinegar from the cafeteria. The student decides to titrate 10.0 mL of vinegar with a 0.0100 mol/L Ca(OH)2(aq). The following data were collected :

|Trial |Initial reading (mL) |Final reading (mL) |

|1 |0.4 |15.4 |

|2 |15.4 |28.4 |

|3 |28.4 |31.2 |

|4 |31.2 |44.3 |

What is the concentration of vinegar?

5. If 2.00 g of an unknown acid (HA) neutralizes completely 45.0 mL of a 0.347 mol/L NaOH(aq) solution, find the molar mass of the acid.

Chemistry 20

Day 35

Date: _____________________ Name: _________________________

Chemical analysis by titration

Titration is a common experimental design in chemistry used to determine the concentration of a substance in solution.

Titration involves the carefully measured and controlled addition of a solution from a buret into a measured volume of a sample solution until the reaction is judged to be completed.

Buret: A buret is a precisely marked glass cylinder with a stopcock at one end. It measures a volume of reacting solution.

The solution in the buret known as the titrant is added to the sample until the reaction is complete.

An indicator is used in all acid-base titration. The color change of the indicator indicates the end of the reaction.

|Some Definitions |

| |

|Titration: It’s a progressive transfer of a solution from a buret into a measured volume of a sample solution. It is used to determine the|

|concentration of a solution. |

| |

|Endpoint: The completion of the reaction is indicated by a sudden color change of an indicator. This is referred as the endpoint of the |

|titration. |

| |

|Equivalence point: The measured quantity of titrant added when the endpoint occurs is called the equivalence point. |

| |

|Standard solution: Solution used in the buret. Standard solutions are solutions with precisely known concentrations. |

A titration analysis should involve several trials, using different samples of the unknown solution to improve the reliability of the answer. A typical requirement is to repeat measurements until three trial results within 0.2 mL (and then take the average).

Titration is a good example of a chemical technology that is reliable, economical and simple to use.

Interpreting pH curves

For many acid-base reactions the appearance of the products resembles that of the reactants, so you cannot directly observe the progress of a reaction. Also, acids cannot easily be distinguished from bases except by measuring pH.

The pH values and changes provide important information about the nature of acids and bases, the properties of conjugate acid-base pairs and indicators, and the stoichiometric relationships in acid-base reactions. A graph showing the continuous change of pH during an acid-base reaction is called a pH or titration curve for the reaction.

What is a titration curve?

Titration curve : It’s a graph of pH vs volume of substance added.

This graph shows the fast change in the pH when the equivalence point is reached.

There are two types of titration curve:

1. Titration curve for the titration of a strong acid with a strong base.

2. Titration curve for the titration of a strong base with a strong acid

|Two types of titration curves |

| |

|1. Titration curve for the titration of a strong acid with a strong base: |

| |

|pH |

| |

| |

| |

| |

| |

| |

| |

| |

| |

| |

| |

| |

|Volume of base added |

| |

| |

|Characteristics of the curve: ____________________________________________ |

| |

|____________________________________________ |

| |

| |

|2. Titration curve for the titration of a strong base with a strong acid: |

| |

|pH |

| |

| |

| |

| |

| |

| |

| |

| |

| |

| |

| |

| |

|Volume of acid added |

| |

| |

| |

|Characteristics of the curve: ____________________________________________ |

| |

|____________________________________________ |

| |

| |

Examples:

1. It takes 83 mL of a 0.45 mol/L sodium hydroxide solution to neutralize 235 mL of hydrochloric acid solution. What is the concentration of the hydrochloric acid solution?

pH+

Volume of acid./base added

Chemistry 20

Homework 35

Name: ____________________________ Date: __________________________

Exercises

1. It takes 38 mL of 0.75 M NaOH solution to completely neutralize 155 mL of a sulfuric

acid solution (H2SO4). What is the concentration of the H2SO4 solution? Do not forget to complete a titration curve.

pH+

Volume of acid./base added

2. You are titrating an acid into a base to determine the concentration of the base. The

endpoint of the neutralization is reached but the stopcock on the buret sticks slightly

and allows a few more drops of acid to fall into the solution. How will this affect your

calculations for the concentration of the base?

3. It takes 12.5 mL of a 0.30 M HCl solution to neutralize 285 mL of NaOH solution. What

is the concentration of the NaOH solution? Do not forget to complete a titration curve.

pH+

Volume of acid./base added

4. Lulu Labwrecker carefully pipets 25.0 mL of 0.525 M NaOH into a test tube. She places

the test tube into a small beaker to keep it from spilling and then pipets 75.0 mL of

0.355 M HCl into another test tube. When Lulu reaches to put this test tube of acid into

the beaker along with test tube of base she accidentally knocks the test tubes together

hard enough to break them and their respective contents combine in the bottom of the

beaker. Is the solution formed from the contents of the two test tubes acidic or basic?

What is the pH of the resulting solution?

PROJECT ON STOICHIOMETRY

|Create a power point presentation with the following parts |

|Description of the chosen reaction and problem |

|Description of one of the chemical involved in the reaction (Properties-Production-Usage- 3 Interesting facts) |

|Stoechiometric calculations |

|Material + Procedure + pictures (or video) of the experiment. |

|Table of observations, Percent of error, References |

| |4 |3 |2 |1 |

| |-Good chemical equation | | | |

|Stoichiometric |-Good answer |3 out of 4 points covered and |2 out of 4 covered and correct|1 out of 4 covered and correct|

|Calculations |-All scientific convention |correct | | |

| |- All 4 steps | | | |

|Other parts of the |All 5 parts are included |4 out of 5 parts covered and |3 out of 5 parts covered and |2 out of 5 parts covered and |

|project |Details are correct |correct |correct |correct |

|X2 | | | | |

| |-Pictures (video) present | | | |

|Presentation |-Animation |3 out of 4 points covered |2 out of 4 points covered |1 out of 4 points covered |

|Quality |-Grammar/Spelling | | | |

| |-Overall quality | | | |

| |- Physical properties are included | | | |

|Description of chemical|- Usage is included |3 out of 4 points covered |2 out of 4 points covered |1 out of 4 points covered |

| |- Production is included | | | |

| |- Facts are included | | | |

TOTAL = /20

Examples of reactions for the stoichiometry project

Single replacement:

Example: Mg(s) + HCl(aq) (

Zn(s) + H2SO4(aq) (

Cu(s) + AgNO3(aq) (

Neutralization:

Example: Vinegar + Baking soda ( Gas produced

H2SO4(aq) + KOH(aq) (

Aspirin or other commercial acids with KOH(aq) (

Precipitation:

Example: Na2CO3(aq) + CaCl2(aq) (

KI(aq) + Pb(NO3)2(aq) (

Combustion:

Example: CH3OH(aq) + O2(g) (

C25H52(aq) + O2(g) (

Chem 20 Project Working sheets

Part A: Research

1. Write a balanced equation of your reaction.

___________________________________________________________________

2. Choose one of the chemicals involved in the reaction and answer the following questions.

a) Chemical chosen: __________________________

b) Find the following physical properties: Phase at room temperature: __________

Melting point: _________

Boiling point: _________

Density: _________

c) A short description of what this chemical is used for.

___________________________________________________________________________

___________________________________________________________________________

d) A short description of how this chemical is produced.

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

e) List 3 interesting facts about the chemical.

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

f) Which references did you used to find the information about the chemical?

______________________________________________________________________

3. State your problem. (Reaction and quantity f reactants used)?

_______________________________________________________________

_______________________________________________________________

4. Calculate the amount of products that should be produced (stochiometric calculations).

Step #1: ________________________________________________________________

Step #2: ________________________________________________________________

Step #3: ________________________________________________________________

Step #4: ________________________________________________________________

Part B: Experiment

1. Make a list of material.

2. Write a short procedure.

3. Make a table of observation.

4. Calculate the percent of error by using the following formula:

Chemistry 20

Day 42

Date: _____________________ Name: ________________________

Introduction to organic chemistry

The nature of Organic Chemistry has changed greatly since 1828. Before that time the scientific philosophy known as "Vitalism" maintained that Organic Chemistry was the chemistry of living systems.

It maintained that Organic Compounds could only be produced within living matter while Inorganic compounds were synthesized from non-living matter.

Even the word "organic" comes from the same root as the word "organism" or "organ". However people like Professor Wohler beginning in 1828 determined that it was indeed possible to synthesize organic compounds from those compounds that were considered inorganic.

One of the first organic compounds synthesized from basically inorganic compounds was the compound Urea which is a metabolic product of urine. Since then many millions of Organic compounds have been synthesized.

Organic Chemistry has developed into a branch of Chemistry that focuses upon the carbon containing compounds.

|Definitions |

| |

|Organic chemistry: Study of the molecular compounds of carbon. |

| |

|Organic compounds: Organic compounds are those based on the element carbon. |

|They contain carbon and hydrogen and have a carbon-hydrogen bond. |

| |

|Exceptions: Compounds that contains the ions : CO32- , CN- , HCO3- are not organic compounds |

| |

|Inorganic compounds : All the other compounds |

| |

| |

|Chemists usually represent organic compounds using a condensed structural diagram showing only the carbon-carbon bonds. |

| |

|Example: Butane (C4H10) is represented: CH3 - CH2 - CH2 - CH3 |

There are actually two different ways of representing the molecule of C4H10.

1. As butane: CH3 - CH2 - CH2 - CH3

2. As methylpropane CH3 - CH2 - CH3

|

CH3

These substances have the same molecular formula C4H10 , but two different structures; these two substances are know as isomers of C4H10 .

|Isomers |

| |

|Isomers: Substances with the same molecular formula but different structures. |

| |

|Examples: C4H10 has 2 isomers C5H12 has 3 isomers |

|C10H22 has 75 isomers C20H42 has 366 319 isomers |

Examples: using the molecular model, draw the condensed structural diagram of all the isomers of the molecules below.

a) C2H3Cl3 b) C5H12

b) C2H2Br2O d) C3H6O2

Functional groups in Organic Compounds

Organic Chemistry is the largest branch and fastest growing branch of Chemistry. Generally Organic Chemistry is manageable by classifying organic compounds into "families".

Each family consists of compounds that have a chemically active center of the molecule called the family's "functional group". All members of a particular family have similar Chemistry because their functional group is the center of Chemical activity.

|Functional groups |

| |

|Functional groups are characteristics arrangements of atoms within a molecule. |

| |

|Chemists divide organic compounds into families, classifying them according to functional groups. |

| |

|Functional groups are largely responsible for properties of the compound. |

| |

|The properties of ethanol are largely determined by the presence of the –OH group of atoms which is known as the hydroxyl group. |

| |

|The properties of organic acids are largely determined by the presence of the –COOH group of atoms which is known as the carboxyl group. |

Classifying Organic Compounds

Organic chemists divide carbon compounds into families, classifying them according to functional groups.

These groups help to explain many of the chemical properties of organic compounds.

The table on the next page lists families of organic compounds, each of which you will study in this unit.

In the general formula

R represents any chain of carbon and hydrogen toms.

X represents a halogen atom.

|Family name |General formula |Example |

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Chemistry 20

Homework #42

Name: ____________________________ Date: __________________________

Exercises

1. Match the following compounds to the families listed below. You can use the same family more than once.

1 = Acids 2 = Alcohols 3 = Aldehydes 4 = Alkane

5 = Alkene 6 = Alkyne 7 = Alkyl halide 8 = Esters

9 = ketone

O

||

a) CH3 - CH2OH - CH3 : _____ b) CH3 - CH - CH2 – C - CH3 : ____

c) CH3 - CH - CH2- CH=O : _____ d) CH3 – CH2 - COO -CH2 - CH2 - CH3 : _____

|

CH3

e) CH3 -CH2 -CH2-CH2 – COOH : _____ f) CH(C-CH2-CH3 : _____

CH3 CH3

| |

g) CH3-CH-CH-CH-CH3 : _____ h) CH3-CH2-C-CH=CH2 : _____

| | |

CH3 CH3 C2H5

F

|

i) CH3 - CH2 - CH2 - C - CH2 - CH2 - CH3 : _____ j) CH3COOCH3 : _____

|

CH2 - CH3

k) CH3CHO : _________ l) HCOOH : _______ m) CH3OH : ______

n) CH3-CH2OH-CH2-CH3 : ______ o) CH2-CH3 -CH-CH3

| : _____

CH2-CH3

2. The compound with the formula C4H10O could be classified as

A. ketone B. alcohol C. ester D. aldehyde

3. The compound with the formula C4H8 could be classified as

A. Alkane B. Alkene C. Alkyne D. Alcohol

4. The compound with the formula C4H8O2 could be classified as

A. ketone B. alcohol C. ester D. aldehyde

5. Which of the following compound would have a triple bond

A. C3H8 B. C3H6 C. C3H4 D. C3H14

Chemistry 20

Day 43

Date: ____________________ Name: _________________________

Hydrocarbons

|Important information |

| |

|Coal, crude oil, oil sands, heavy oil and natural gas are the primary sources of hydrocarbons. |

|Petroleum is a complex mixture of hundreds of thousands of compounds. The differences in boiling points of the compounds making up |

|petroleum enable the separation of these compounds in a process called fractional distillation. |

|Refining is the technology that includes separating complex mixtures into purified components. |

A fractional distillation tower

[pic]

Fractional distillation petroleum

|Boiling point range of fraction (°C) |Carbon atoms per molecule |Fraction |Applications |

|Below 30 |1 to 5 |Gases |Fuels for cooking and heating homes |

|30 to 90 |5 to 6 |Ether |Dry cleaning, solvents, camping fuel |

|30 to 200 |5 to 12 |Gasoline |Automotive gasoline |

|175 to 275 |12 to 16 |Kerosene |Diesel, jet engines |

|250 to 375 |15 to 18 |Fuel oil |Furnace oil |

|Over 350 |16 to 22 |Heavy gas oil |Lubricating oils |

|Over 400 |18 and up |Grease |Lubricating greases |

|Over 450 |20 and up |Waxes |Candles,… |

|Over 500 |26 and up |Residues |Asphalt and tar |

Alkanes

The IUPAC(international Union of Physics and Chemistry) rules will be used for naming all organic compounds. In this system, the following stems for naming organic compounds containing up to 12 carbons in a straight chain are used.

|# of carbons |Stem name |Branch name |Branch Structure |

|1 |Meth |Methyl |- CH3 |

|2 |Eth |Ethyl |- C2H5 or -CH2-CH3 |

|3 |Prop |Propyl |- C3H7 or -CH2-CH2-CH3 |

|4 |But |Butyl |- C4H9 or -CH2-CH2-CH2-CH3 |

|5 |Pent |Pentyl |- C5H11 |

|6 |Hex |X |X |

|7 |Hept |X |X |

|8 |Oct |X |X |

|9 |Non |X |X |

|10 |Dec |X |X |

|11 |Unodec |X |X |

|12 |Dedec |X |X |

|Definition |

| |

|Hydrocarbons whose structural formula indicates only single carbon to carbon bonds are called alkanes. |

| |

|Alkanes have a general formula of CnH2n+2 |

| |

|All carbon-carbon bonds in alkanes are single bonds; this means the maximum number of hydrogen atoms are bonded to each |

|carbon, and the molecule is said to be saturated. |

|Notes |

| |

|The simplest member of the alkane series is methane CH4(g), which is the main constituent of the natural gas sold for home |

|heating. |

| |

|Each member of the alkane family have the suffix “ane” . |

| |

|Example: CH4(g) : methane C2H6(g) : ethane C3H8(g) : propane C4H10(g) : butane C5H12(l) : pentane C6H14(l) : |

|hexane C7H16(g) : heptane C8H18(l) : octane C9H20(l) : nonane C10H22(l) : decane C11H24(l) : unodecane |

| Rules to name alkanes |

| |

|Name the longest continuous chain of carbon atoms in the molecule by naming the stem for the appropriate number of carbon atoms plus the |

|suffix “ane”. |

|For branched chain alkanes, number the carbon atoms of the longest continuous chain starting at the end closest to the branching. |

|Locate the branch by the number of the carbon atom to which it is attached on the main chain. |

|Name the branch. The position and name of the alkyl branches are given first in the overall name. The location of each group is indicated |

|by the lowest possible numbers. |

|If more than one of the same alkyl groups are present as branches, use di – tri- tetra |

Examples:

1. Name the following compounds.

CH3

|

CH3-CH-CH2-CH3 : _________________________________________________________

CH2 - CH3

|

CH3-CH2-C-CH2 -CH2 -CH3 : ____________________________________________________

|

CH3

CH3

|

CH3-CH-CH2-CH-CH2 -CH -CH3 : ____________________________________________

| |

CH3 CH2 - CH3

CH3 CH2 -CH3

| |

CH3-CH2-CH-CH2-CH-CH -CH2 -CH3 : ________________________________________________

|

CH2-CH2-CH3

CH2-CH3

|

CH3-CH-CH2-CH-CH2-CH3 : ________________________________________________

|

CH2 -CH3

2. Write the condensed structural diagram for the following compounds.

a) 2-methyl butane b) 3,3-diethyl pentane c) 2,3,4-trimethyl 3,5-diethyl heptane

| Shortcut |

| |

|Many shortcuts can be used to simplify larger molecules. The two simple shortcut used in chem 20 are: |

| |

|1. Use the molecular formula for some parts of the molecule. |

| |

|CH2-CH3 C2H5 |

|| | |

|Example: CH3-CH-CH- CH2- CH2- CH3 becomes CH3-CH- CH-C3H7 |

|| | |

|CH2-CH3 C2H5 |

| |

|2. Use of brackets within the chain when the same group is repeated. |

| |

|Example: CH3-CH2-CH2- CH2-CH3 becomes CH3-(CH2)3-CH3 |

Examples:

1. Name the following compounds.

CH3- CH-C2H5 : _________________________________________________________

CH3-(CH2)4 -CH3 : ____________________________________________________

CH3- CH-(CH2)3 - CH3 : ____________________________________________

|

C2H5

2. Write the structural formula of the following compound. Use as many shortcuts as you can.

3,4-diethyl 8,8-dimethyl nonane

Chemistry 20

Homework # 43

Date: ____________________ Name: _________________________

1. Name each of the following compounds.

a) CH3-CH2-CH-CH2-CH3 b) CH3-CH2- CH-CH3

| |

CH3 CH2-CH3

_____________________________ _________________________________

CH3 C2H5

| |

c) CH3-CH-CH-CH-CH3 d) CH3-CH2-C-CH2-CH3

| | |

CH3 CH3 C2H5

_____________________________ _________________________________

CH3 C2H5 CH3 CH3 CH3

| | | | |

e) CH3-CH-CH2-C–(CH2)3-CH3 f) CH - C - CH

| | | |

C3H7 CH3 CH3 CH3

_____________________________ _________________________________

g) C2H5- CH-CH2-CH-CH2-CH3 h) CH3-CH-CH3

| | |

CH3 C2H5 C3H7

_____________________________ _________________________________

C2H5 CH3

| |

i) CH3-CH2-CH2-C-CH2-CH-CH3 j) CH3-CH2-CH-(CH2)3-CH3

| |

C3H7 CH3

_____________________________ _________________________________

g) CH3- CH2 – CH - (CH2)3 – CH - C2H5

|

CH3

__________________________________________________________

2. Draw the condensed structural diagram for the following compounds.

a) 3-ethyl hexane b) 2,4-dimethyl heptane

c) 3,4-diethyl-3-methyl hexane d) 2-methyl butane

e) 2,2,3,3 tetramethyl pentane f) 3,4-dimethyl-3-ethyl octane

3. Draw the structural diagram and name 4 isomers of C6H14

Chemistry 20

Day 44

Date: ______________________ Name: __________________________

Alkenes and Alkynes

Analysis reveals that hydrocarbons containing double or triple bonds are minor constituents in natural gas and petroleum. However, these compounds are often formed during cracking reactions and are valuable components of gasoline. Hydrocarbons containing double or triple bonds are important in the petrochemical industry because they are starting materials for the manufacture of many derivatives.

Hydrocarbons with carbon-carbon double bonds are member of the alkene family.

Hydrocarbons with carbon-carbon triple bonds are member of the alkyne family.

| Definitions |

| |

|Alkenes all contains at least one carbon-carbon double bond and Alkynes all contains at least one carbon-carbon triple bond. |

|Alkenes have a general formula of CnH2n (Two less hydrogen atoms/double bond) |

|Alkynes have a general formula of CnH2n-2 (Four less hydrogen atoms/double bond) |

| Saturated or unsaturated? |

| |

|Hydrocarbons that do not contain the maximum number of hydrogen atoms possible are said to be unsaturated with hydrogen. Alkenes and |

|alkynes are, therefore, unsaturated compounds. |

| Rules to name alkenes and alkynes |

| |

|Name the longest continuous chain of carbon atoms that include the double bond using “ene”. Indicate the position of the double bond with the number |

|of the carbon that precedes the bond. |

|Branches on alkenes molecules are indicated and named as they are on alkane molecules. |

|If more than one double bond is present, indicate the positions of all double bonds with numbers and place a multiplier in the suffix. |

| |

|To name the alkynes, the same rules apply except that the name of the longest chain that include the triple bond ends with "yne" |

Examples:

a) CH2 = CH - CH3 : _______________________ b) CH2 = CH - CH2 - CH3 : ________________________

c) CH3 - CH = CH - CH3 : ____________________ d) CH(CH :

e) CH3-C(C-CH3 : _______________________ f) CH(C-C-CH2-C-(CH3)2 : ________________________

|

C2H5

g) CH3-CH2-C=CH2 : ________________________ h) CH2=CH-C=CH-CH2-CH3 :______________________

| |

CH3 CH2 - CH3

2. Draw the structural formula and name all the isomers of C5H10

Chemistry 20

Homework #44

Name: ____________________________ Date: __________________________

Exercises

1. Name each of the following compounds.

CH3

|

a) CH3-C=CH-C-CH2-CH3 b) CH2=CH-C-(CH2)2-CH3

| |

C2H5 C3H7

_____________________________ _________________________________

c) CH2=CH-CH–(CH2)2-CH3 d) CH(C-CH2-CH3

|

CH = CH2

_____________________________ _________________________________

C4H9 C2H5

| |

e) CH2=CH-CH2-CH-C2H5 f) CH3-CH2-CH-C(C-CH3

_____________________________ _________________________________

2. Draw the condensed structural diagram for the following compounds.

a) 2,4-dimethyl pent-1-ene b) 3-methyl-4-ethyl hex-2-ene

c) 4,4-diethyl hex-1-yne d) 2-methyl prop-1-ene

e) 3-methyl pent-1,3-diene f) 5-ethyl-4-propyl hept-2-yne

g) hept-2,5- diene j) 4-propyl oct-4-ene

3. Draw the structural diagram and name 4 isomers of C6H10

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The pH Scale

Chemists have developed a scale that classifies how acidic or basic substances are. This pH scale classifies substances from 0 to 14.

• Acids have a pH of less than 7.

• Bases have a pH greater than 7.

• Substances that fall in the middle of the scale are neutral.

As you get closer to 0, the substances get more acidic. As you move toward 14 on the scale, the substances get more basic.

Note: A change of 1 in the pH scale represent a change of 10X the concentration.

Example: A pH of 4 is 10X more acidic than a ph of 5

A pH of 12 is 10X more basic than a pH of 11

[pic]

A student records the following observation when testing 4 solutions:

Reaction with magnesium Bromothymol blue

Solution 1 No reaction Blue

Solution 2 Gas produced Yellow

Solution 3 No reaction Green

Solution 4 No reaction Yellow

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