NOTES: ACIDS, BASES AND NEUTRALIZATION
Ch 19: ACIDS, BASES AND NEUTRALIZATION
ACIDS:
substances that give H+ (a proton) to water
pH < 7
[H+] > [OH-] [ ] means “the molarity of..”
Review: formula writing for acids
binary acids: hydro_stem of nonmental__ ic acid
e.g.: HCl _hydrochloric acid_ HBr ___ hydrobromic acid __
H2S __ hydrosulfuric acid __ H3N ____ hydronitric acid ____
ternary acids: “ate becomes ic” and “ite becomes ous”
_ate ( _ic
e.g. sulfuric acid (sulfate) ______ H2SO4_____________________
nitric acid (nitrate) ______ HNO3_____________________
HC2H3O2 _______acetic acid_________
_ite ( _ous
e.g. sulfurous acid (sulfite) _______ H2SO3_________________
nitrous acid (nitrite) _______ HNO2____________________
H3PO3 _______phosphorous acid ________
Strong Acids:
HCl – hydrochloric acid
HBr – hydrobromic acid
HI – iodic acid
HNO3 – nitric acid
H2SO4 – sulfuric acid
HClO4 – perchloric acid
Weak Acids:
e.g. vinegar (acetic acid, HC2H3O2)
Dissociation of Strong Acids Dissociate 100% into positive and negative ions
HCl ( H+ + Cl-
H2SO4 ( 2 H+ + SO42-
Dissociation of Weak Acids
HC2H3O2 (
Weak acids do not dissociate completely. Instead they form an equilibrium. A double arrow is used to show this.
HC2H3O2 [pic] H+ + C2H3O2-
BASES
substances that dissociate to form OH- ions, or remove H+ from water to make OH- ions
pH > 7
[OH-] > [H+]
STRONG BASES: Dissociate 100% into positive and negative ions
Group I and II hydroxides Sr(OH)2, Ba(OH)2
NaOH
Ba(OH)2
WEAK BASES:
NH3
Dissociation of Strong Bases
NaOH ( Na+ + OH-
Ba(OH)2 ( Ba+2 + 2 OH-
Dissociation of Weak Bases
NH3 + H2O [pic] NH4+ + OH-
Weak bases take hydrogen ions (H+) from water, leaving OH- which makes the solution basic. This is an equilibrium.
Dissociation of Water:
H2O [pic] H+ + OH- water itself ionizes into H+ and OH-, but only to a very small extent. All water based solutions have H+ and OH-. If there is more H+ the solution is acidic. If there is more OH- it is basic.
pH
pH = -log [H+] pOH = -log[OH-]
If [H+] = 10-3 M, pH = 3 pOH = 14 - pH
pH + pOH = 14 [H+] x [OH-] = 1.0 x 10-14 M
Acids: pH < 7 Bases: pH > 7 Neutral: pH = 7
[pic]
|solution |acid or base? |[H+] |[OH-] |pH |pOH |
| | | | | | |
|0.010 M HCl |acid |0.01 M |10-12 M |2 |12 |
| | |(10-2 M) | | | |
| | | | | | |
|0.00010 M HNO3 |acid |0.0001 M |10-10 M |4 |10 |
| | |(10-4 M) | | | |
| | | | | | |
|1 x 10-6 M HI |acid |10-6 M |10-8 M |6 |8 |
| | | | | | |
|0.0010 M NaOH |base |10-11 M |0.001 M |11 |3 |
| | | | | | |
|Windex |base |10-12 M |0.01 M |12 |2 |
| | | | | | |
|lemon juice |acid |0.001 M |10-11 M |3 |11 |
| | |(10-3 M) | | | |
| | | | | | |
|sprite |acid |0.0001 M |10-10 M |4 |10 |
| | |(10-4 M) | | | |
| | | | | | |
|ammonia |base |10-12 M |0.01 M |12 |2 |
| | | | | | |
|milk |acid |10-6 M |10-8 M |6 |8 |
PROPERTIES OF ACIDS & BASES: MINI LAB
Safety: Acids and Bases are caustic. If you spill an acid in lab, neutralize with baking soda before cleaning up with water. If you spill a base in lab, neutralize with a weak vinegar solution before cleaning up with water. If you spill and acid OR base on your skin, flush with plenty of water (DO NOT neutralize…….why?).
1. Conductivity
i. Clean and dry a well plate thoroughly.
ii. Add 5 drops of each solution into the well plate.
iii. Use your conductivity tester to test whether or not each solution conducts electricity. Be sure to clean off the tester with distilled water after each solution!
iv. Record observations in the chart below:
|Solution |Conducts? Yes or No? To what extent? |
|alcohol | |
|distilled water | |
|hydrochloric acid | |
|sodium hydroxide | |
|Gatorade | |
a) Use your textbook to define the term electrolyte:
A compound that conducts an electric current when it is in an aqueous solution or is melted.
b) What do solutions need to conduct electricity?
1. Charged particles……
2. ….that can move!
c) What ions are in a solution of hydrochloric acid? ______ H+ + Cl-_______________
d) What ions are in a solution of sodium hydroxide? ______ Na+ + OH-_______________
e) Why do you think Gatorade conducts electricity if it is not an acid or a base?
It contains electrolytes.____________________________________________
2. Reactivity with Metals
i. Measure out 10 mL of hydrochloric acid using a graduated cylinder.
ii. Pour the hydrochloric acid into a small beaker.
iii. Add a piece of zinc to hydrochloric acid and observe.
iv. Record observations in the below.
v. Remove zinc with forceps and rinse with water.
vi. Clean out graduated cylinder and beaker.
vii. Repeat steps 1-4 using sodium hydroxide instead of hydrochloric acid.
viii. Remove zinc with forceps and rinse with water. Return zinc to zinc beaker
ix. Clean out graduated cylinder and beaker.
|Reaction |Observations |
|hydrochloric acid and solid zinc | |
|sodium hydroxide and solid zinc | |
a) Write the formula for hydrochloric acid: __HCl___________________________________
b) Write the formula for sodium hydroxide: ___NaOH________________________________
c) Write a balanced reaction for the reaction you observed:
_______ Zn + 2 HCl ( ZnCl2 + H2__________________________
d) What type of reaction is this? _______single replacement_____________________
e) Given 3.5 g of zinc, what volume of hydrogen gas would form at STP?
3.5 g Zn x 1 mol Zn x 1 mol H2 x 22.4 L H2 = 1.2 L H2
65.4 g Zn 1 mol Zn 1 mol H2
3. Exploring with Indicators
1. Add 5 drops of each solution into a clean well plate. Be sure you identify for yourself which well contains which solution.
2. Test each well using pH paper. Match the color of the pH paper to the scale and record readings in the data table below.
3. Test each well using the red litmus paper. Record observations in the data table below.
4. Test each well using the blue litmus paper. Record observations in the data table below.
5. Add one drop of phenolphthalein into each well. Record observations in the data table below.
6. Clean and dry well plate thoroughly.
7. Add 5 drops of each solution into a clean well plate. Be sure you identify for yourself which well contains which solution.
8. Add one drop of universal indicator into each well. Record observations in the data table below.
9. Clean and dry the well plate thoroughly.
|solution |pH paper |red litmus |blue litmus |phenolphthalein |universal indicator |
|A | | | | | |
|B | | | | | |
|C | | | | | |
|D | | | | | |
|E | | | | | |
Other properties of Acids and Bases:
Common household acids include citrus, vinegar, and yogurt. Based on your experience with these items, acids taste __________sour__________________.
Common household bases include bleach, soap, and baking soda. Based on your experience with these items, bases taste ______bitter_____________________. Bases feel ____slippery______ to the touch.
Both acids and bases are ____caustic__________. If you spill acid in lab, you should neutralize it with __baking soda_____ before cleaning up. If you spill a base in lab, you should neutralize it with _____vinegar_______ before cleaning up.
a) Use the pH (from your data) of the unknown solutions to complete the pH chart below:
|solution |acid or base? |[H+] |[OH-] |pH |pOH |
| | | | | | |
|A | | | | | |
| | | | | | |
|B | | | | | |
| | | | | | |
|C | | | | | |
| | | | | | |
|D | | | | | |
| | | | | | |
|E | | | | | |
b) What volume of 0.01 M HCl is needed to completely react with 2 g magnesium ribbon?
RXN: ______ Mg + 2 HCl ( MgCl2 + H2_____________________________
2 g Mg x 1 mol Mg x 2 mol HCl = 0.165 mol HCl
24.3 g Mg 1 mol Mg
M = mol so volume = mol = 0.165 = 16.5 mL HCl
L M 0.01
c) A student spills 5 mL of sulfuric acid on the lab table. To neutralize the acid, he pours sodium hydroxide on it and forms sodium sulfate and water. If the initial pH of the sulfuric acid is 2, what mass of water was formed?
RXN: ____ H2SO4 + 2 NaOH ( Na2SO4 + 2 H2O ____________
pH = 2 , so M = 0.01 M
M = mol so mol = M x Volume = 0.01 x 0.005 = 0.00005 mol H2SO4
L
0.00005 mol H2SO4 x 2 mol H2O x = 18 g H2O = 0.0018 g H2O
1 mol H2SO4 1 mol H2O
Based on the information you discovered in this lab, complete the following properties chart:
|PROPERTY |ACIDS |BASES |
|conductivity |yes |yes |
|reacts with metals |yes |no |
|pH |7 |
|red litmus |no effect |turns blue |
|blue litmus |turns red |no effect |
|phenolphthalein |turns colorless |turns pink |
|universal indicator |turns red |turns blue |
|taste |sour |bitter |
|texture | |slippery |
|spills |neutralize with baking soda |neutralize with vinegar |
NEUTRALIZATION REACTIONS (always double replacement)
acid + base ( salt (ionic compound) + water
H-A + B-OH ( A-B + H-OH
Example: sodium hydroxide + hydrochloric acid (
+1 -1 +1 -1 +1 -1
NaOH + HCl ( NaCl + H2O (HOH)
potassium hydroxide + nitric acid (
+1 -1 +1 -1 +1 -1
KOH + HNO3 ( KNO3 + H2O
lithium hydroxide + sulfuric acid (
+1 -1 +1 -2 +1 -2
2 LiOH + H2SO4 ( Li2SO4 + 2 H2O
barium hydroxide + phosphoric acid (
+2 -1 +1 -3 +2 -3
3 Ba(OH)2 + 2 H3PO4 ( Ba3(PO4)2 + 6 H2O
acetic acid + sodium hydroxide (
+1 -1 +1 -1
HC2H3O2 + NaOH ( NaC2H3O2 + H2O
TITRATION
A method of finding the molarity of an unknown solution by reacting it with a solution of known molarity.
# H’s in solution = # OH’s in solution
(# H in Acid) x (Macid) x (Vacid) = (# OH in Base) x (Mbase) x (Vbase)
Titration Problems:
a. What volume of 0.15 M sodium hydroxide solution is needed to react with 12.2 mL of 0.350 M hydrochloric acid?
(# H in Acid) x (Macid) x (Vacid) = (# OH in Base) x (Mbase) x (Vbase)
1 x 12.2 x 0.350 = 1 x 0.15 x V
V = 28.5 mL
b. What volume of 0.250 M nitric acid is needed to react with 20.5 mL of 0.10 M lithium hydroxide?
(# H in Acid) x (Macid) x (Vacid) = (# OH in Base) x (Mbase) x (Vbase)
1 x V x 0.250 = 1 x 0.10 x 20.5
V = 8.2 mL
c. Find the molarity of an unmarked hydrochloric acid solution if 14.51 mL of the solution reacts completely with 12.24 mL of 0.030 M sodium hydroxide solution.
(# H in Acid) x (Macid) x (Vacid) = (# OH in Base) x (Mbase) x (Vbase)
1 x 14.51 x M = 1 x 0.030 x 12.24
M = 0.025 M
d. Find the molarity of a nitric acid solution if 10.4 mL of the solution is needed to react with 25.0 mL of 0.45 M barium hydroxide.
(# H in Acid) x (Macid) x (Vacid) = (# OH in Base) x (Mbase) x (Vbase)
1 x 10.4 x M = 25 x 0.45 x 2 (2 because Ba(OH)2 has two hydroxides)
M = 2.16 M
HW: ACIDS AND BASES PREVIEW
Use your textbook or the Internet to find the answers to the following questions.
1. What is an acid? __A compound that produces H+ ions in solution__________________
______________________________________________________________________________
2. What is a base? ____ A compound that produces OH- ions in solution ____________________
______________________________________________________________________________
3. What is the pH of an acid? __less than 7______ of a base? ___ greater than 7__
4. What does a concentrated acid feel like on the skin? ____burning/pain!________
5. What does a concentrated base feel like on the skin? _____slimy/slippery_______
6. Fill in the table below
| |Acidic |Basic |
|2 foods |vinegar |coffee |
| |lemon |vegetables |
|2 household items other than food |batteries |Windex |
| |plant food (some, not all) |bleach |
7. Do acids and bases conduct electricity? ____yes – they are electrolytes______________________
8. Acids and bases are said to be corrosive or caustic. What does this mean? ____________________
___ capable of burning, degrading, or destroying living tissue__________________________
9. A __neutralization____ reaction occurs when an acid and a base react with each other. The products of this type of reaction are _salt (ionic compound)__ and _____water______.
10. What does it mean if an acid is strong? Give 2 examples of strong acids. ____________________
Strong acids dissociate completely (100%) in water and have a low pH. Examples: hydrochloric (HCl), nitric (HNO3) and sulfuric (H2SO4)_______________________________
11. What does it mean if an acid is weak? Give 2 examples of weak acids. Weak acids dissociate partially ( ................
................
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