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Honors Chemistry - Unit 2 Dimensional Analysis, SI, Density and Gas Laws

Vocab Quiz: Thursday, August 9 Dimensional Analysis Quiz: Wednesday, August 8 Gas Laws Quiz: Tuesday, August 14 EQs and Problem Set Due: Friday, August 17

Test Date: Friday, August 17

Vocabulary:

temperature weight mass precision

density length volume accuracy

significant figures SI units percent error Ideal Gas Law

standard atmospheric pressure standard temperature STP Combined Gas Law

Boyle’s Law Charles’ Law molar volume

Formulas/constants to be memorized:

metric conversions *percent error *density

(* = formula found in notes, memorize for test)

Refer to Reference Pack for all formulas

Boyle’s law (P1 V1 = P2 V2) Charles’ law (V1/T1 = V2/T2) Gay-Lussac’s law (P1/T1 = P2/T2)

Combined gas law Dalton’s law Ideal gas law Molar volume Molecular mass Determination

Conversions that do NOT have to be memorized:

1 lb = 453.6 g 1 mile = 1.609 km 1 L = 1.0567 qts 1 oz = 28.35 g

1 m = 39.37 in = 3.2808 ft = 1.0936 yd 4 qts = 1 gal 3 tsp = 1 T 1 oz = 29.57 mL

16 T = 1 c

STANDARDS & OBJECTIVES:

• Be able to apply the concept of significant digits.

• Memorize the metric system; be able to do both pure metric conversions and English-metric conversion. (You will be given English-metric conversions).

• Be able to calculate percent error from lab data.

• Use factor label (dimensional analysis) to solve math problems and conversions.

• Be able to manipulate and solve density problems.

• Be able to explain the difference between accuracy and precision and weight and mass.

• Be able to use the above vocabulary properly.

Laboratory Safety, Equipment, Scientific Method

• Understand labeling of chemicals and products.

• Be able to collect, assimilate, and draw conclusions from scientific data.

• Be able to follow the steps to write a pre-lab and lab report.

• Memorize or be able to locate on reference pack the values for STP.

• Memorize and be able to apply the gas laws: Boyle’s, Charles, Dalton’s law of partial pressure, combined gas law, Gay-Lussac’s, and Graham’s. (some laws in the packet) You do not need to know the names. (Chm.2.1.5)

• Be able to use molar volume of a gas at STP in problems. (Chm.2.1.5)

• Be able to apply the ideal gas law. (Chm.2.1.5)

• Use the gas constant R = .0821 L-atm/mol-K. (Chm.2.1.5)

The following SI System Units must be memorized:

|SI System |

|Unit |Symbol |Meaning |Conversion Factor |

| | | |(Examples) |

|mega |M |million – 1,000,000 |1 ML = 1,000,000 L |

|kilo |k |thousand – 1,000 |[pic] ; [pic] |

|hecto |h |hundred – 100 |[pic]; [pic] |

|deca |da |ten – 10 |[pic]; [pic] |

|deci |d |tenth – 1/10 |[pic]; [pic] |

|centi |c |hundredth – 1/100 |[pic]; [pic] |

|milli |m |thousandth – 1/1000 |[pic]; [pic] |

|micro |μ |millionth – 1/1,000,000 |[pic] |

|nano |n |billionth – 1/1,000,000,000 |[pic] |

|pico |p |trillionth – 1/1,000,000,000,000 |[pic] |

Base units – volume: L – liter; distance: m – meter; mass: g – gram; time: s – second

Scientific Notation Notes & Practice

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Scientific Notation Notes & Practice

Convert Number (long form) to Scientific Notation (Standard Form)

a.) Move the decimal point to the right of the first nonzero digit. Count the number of places you moved the decimal point.

b.) Multiply the number from step a.) times 10 raised to + or - the number of places you moved the decimal point.

(Use + if you moved the decimal to the left.)

(Use - if you moved the decimal to the right.)

o Example: 5280 5.280 x 103

✓ You Try:

1102 = __________________ 47449 = __________________

➢ Scientific Notation to Regular Notation (Long Form)

a.) If the exponent on 10 is positive ("+"), move the decimal to the right the same number of places as the exponent. Add zeros as necessary.

b.) If the exponents on 10 is negative ("-"), move the decimal point to the left the same number of places as the exponent. Add zeros as necessary.

o Example: 3.2 x 105 320,000

✓ You Try:

46 x 104 = __________________ 5 x 10-8 = __________________

Scientific Notation Practice:

1. Express the following in Scientific Notation -

|0.000 03 cm |j) 6 000 000.01 L |

|8 000 000 g |k) 0.000 065 cm |

|55 000 000 m |l) 6500 X 107 km |

|0.002 g |m) 1 000 eggs |

|301 X 1021 m |n) 6.18 L |

|0.000 007 m |o) 0.000 000 078 46 ns |

|65 000 km |p) 22 400 s |

|0.004 03 g |q) one billion |

|0.000 3 kg |r) 364 min |

2. Convert the following to standard form –

|a) 3.3 X 105 |m) 2.3 X 10-3 |

|b) 5.06 X 10-2 |n) 0.007 6 X 104 |

|c) 6.9 X 100 |o) 0.007 6 X 10-2 |

|d) 4.19 X 10-3 |p) 5 X 103 |

|e) 8.0 X 103 |q) 7.8 X 104 |

|f) 3.010 X 10-2 |r) 3.81 X 10-4 |

|g) 5.08 X 103 |s) 4.04 X 107 |

|h) 2.73 X 10-4 |t) 6.09 X 10-9 |

|i) 8.180 X 105 |u) 7.2 X 104 |

|j) 1.007 X 10-2 |v) 1.3 X 10-5 |

|k) 6.915 X 102 |w) 1.0 X 10-5 |

|l) 2.3 X 103 | |

Significant Figures Notes & Practice

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4 Rules for Significant Figures:

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Examples & Practice:

Determine the number of significant figures in the following numbers.

1. 0.02 _________ 5. 5,000 _________ 9. 0.1020 _________

2. 0.020 _________ 6. 5,000.0 _________ 10. 10,001 ________

3. 501 _________ 7. 6,051.00 ________

4. 501.0 _________ 8. 0.0005 _________

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Examples & Practice

Perform the following operations expressing the answer in the correct number of significant figures.

1. 1.35 x 2.467 = ___________ 6. 0.15 + 1.15 + 2.051 = __________

2. 1,035 / 42 = ___________ 7. 150 / 4 = _________

3. 12.01 + 35.2 + 6 = __________ 8. 505 – 450.25 = ___________

4. 55.46 – 28.9 = _________ 9. 1.252 x 0.115 x 0.012 = __________

5. 0.021 x 3.2 x 100.1 = __________

Steps to Solving Dimensional Analysis Problems

Example: How many seconds are there in a year?

1. Don’t Panic! Dimensional analysis is a tool to make hard problems easier. Dimensional analysis is just a fancy way of saying you’re converting from one unit to another.

2. Read the problem carefully to determine what information is given and what question is being asked. In our example, we are given 1 year and asked, “How many seconds?”

3. Ask yourself, “What do I know?” In our example, the question would be, “What do I know about time?” I know that there are 60 seconds in 1 minute, 60 minutes in 1 hour, 24 hours in one day, and 365 days in one year.

4. Write down these relationships as conversion factors.

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5. Write down your given and multiply it by the conversion factor that has those units in the denominator. We want those units to cancel, and that can only happen if one is in the numerator and the other is in the denominator. We use lines to help us organize the information. A vertical line means multiply and a horizontal line means divide.

1 yr 365 days

1yr

6. Check to see if the units in the top right-hand section are the units asked for in the problem. If they are not, you need to use more conversion factors until they are. We are looking for seconds.

1yr 365 days 24 hrs 60 min 60 s

1 yr 1 day 1 hr 1 min

Example: Cynthia is turning 17 years old. Her mother promised her a birthday present of either 1 penny for every minute she had lived (for exactly 17 years, and not considering any leap years) or a brand new $35,000 sports car. Which present should Cynthia choose?

The unwritten question is, “How many dollars would Cynthia have if her mom gave her 1 dollar for every minute she’s been alive?” My starting value could be 17 years, 1 penny, 1 minute, or $35,000. I can see that 1 penny is given in relationship to 1 minute, so that is a conversion factor. $35,000 is what I’m going to compare my answer to in order to decide which present to choose, so that leaves 17 years. I also know that 100 pennies is equal to 1 dollar, 1 year is equal to 365 days, 1 day is equal to 24 hrs, and 1 hr is equal to 60 minutes. I can now write my conversion factors.

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I will consistently choose my conversion factors so that my units cancel, and I move step by step from my starting value to my desired ending unit.

17 yrs 365 days 24 hrs 60 min 1 penny 1 dollar

1 yr 1 day 1 hr 1 min 100 pennies

Cynthia could buy two sports cars!! I think she should take the penny per minute option. ☺

Try these easy examples on your own:

1) How many centimeters are in 6.00 inches? (2.54 cm = 1 inch)

2) Express 24.0 cm in inches.

3) How many minutes are in 83 days?

4) How many seconds are in 36 days?

Dimensional Analysis (Factor Label Method) Notes and Practice

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Conversions Practice Sheet

Metric Conversions

1. 8.5 dg to kg ____________ 4. 65 hm to m ____________

2. 0.23 kg to cg ____________ 5. 1.2 L to ml ____________

3. 876 cg to mg ____________ 6. 87 hg to kg ____________

Other Conversions

7. 13 km to miles ____________ 10. .72 L to gallons _________

8. 8.35 g to oz. ____________ 11. 2760 ft. to miles________

9. 280 g to lbs. ____________ 12. 27.3 m to ft. __________

Factor Label Method

13. 60 miles/hr to km/hr ___________

14. 8.2 g/ml to kg/L ___________

15. 0.82 lbs/gallon to g/ml __________

16. 24 km/hr to miles/hr __________

Conversion practice: Show ALL work!!

As you read the following, work the conversion problems using the factor label method. You may use your notes, but remember the metric conversions must be memorized for the test.

Last fall I took a trip to Europe. In Europe (as in most all of the world, except the US) the metric system is used. Luckily, I remembered my chemistry factor label method and got along just fine. When I arrived in France (bonjour); I took a taxi to my hotel which was 25 km away. The hotel room cost $53.25. In the snack shop I bought a carton of milk that was 650 ml. I also grabbed a 14 g chocolate snack. After snacking, I took the elevator to the top of my 48 ft. tall motel. The bell hop carried my 47 pound suitcase at a rate of 10 cents/kg. Finally, I arrived in my room and ran a bath with 124 L of water. After all traveling is dirty business.

1. How far did I travel to the motel in miles?

2. How many nickels would it have taken to pay my hotel bill?

3. How many kg was my suitcase?

4. How many oz. of milk did I drink?

5. What was the charge for the bellhop to carry my suitcase?

6. How many oz. of water did the bath have?

7. How many lbs. was the chocolate snack?

8. How many km tall was the motel?

Percent Error:

percent error = │[pic]│ X 100

Percent Error Practice:

1. A student measures the mass and volume of a substance and calculates its density as 1.25 g/mL. The correct, or accepted, value of the density is 1.30 g/mL. What is the percent error of the student’s measurements?

2. A handbook gives the density of calcium as 1.54 g/cm3. What is the percent error of a density calculation of 1.25 g/cm3 based on the lab measurements?

3. What is the percent error of a length measurement of 0.229 cm if the correct value is 0.225 cm?

Accuracy & Precision:

✓ accuracy: how close a measurement comes to the true/actual value

✓ precision: how close a series of measurements are to one another; reproducibility

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Accuracy & Precision Practice:

1. Bruce’s three measurements are 19 cm, 20 cm, and 22 cm. Calculate the average value of his measurements and express the answer with the correct number of significant figures.

2. Pete’s three measurements are 20.9 cm, 21.0 cm, and 21.0 cm. Calculate the average value of his measurements and express the answer with the correct number of significant figures.

3. Whose measurements are more precise?

4. The actual length of the object is 20.0 cm. Whose measurements are more accurate?

5. What is the percent error of Pete’s average measurement?

6. What is the percent error of Bruce’s average measurement?

Review - Scientific Notation / Error Analysis / Significant Figures

1. Johnny measured the melting point of aluminum. He found it to be 665.5 ºC. The actual melting point of aluminum is 660.3 ºC. What was his percent error?

2. Expand the number 4.35 x 10-6. __________________________

3. How many significant figures are in the following?

a. 717 _______ b. 0.150 _______ c. 0.0750 _______ d. 5000 _______ e. 50. _______

4. Put the number 0.250 into scientific notation. (Use the correct number of sig figs.) __________________

5. Jill measured the room to be 2.65 x 102 m wide and 3.50 x 103 m long. Express the area of this room in scientific notation. Use correct sig figs and units. (meters x meters = m2)

6. Perform the following operations. Find the calculator answer, then round your answer to reflect the correct number of sig figs. Express your answers in scientific notation.

Calculator Answer Rounded Answer

a. 2.8 x 10-3 / 6.32 x 10-5 _______________________ _______________________

b. (3.02 x 103) x (5.9 x 104) _______________________ _______________________

7. Perform the following operations, first giving the calculator answer, then rounding to the correct number of sig figs. Use the correct units. (For example, m times m equals m2, ft. – ft. = ft., g ÷ mL = g/mL)

Calculator Answer Rounded Answer

a. 56 m x 19.3 m ____________________ ____________________

b. 0.13 s x 90 s ____________________ ____________________

c. 76.33 ft. – 9 ft. ____________________ ____________________

d. 4.73 g ÷ 19.71 mL ____________________ ____________________

Convert the following. (SHOW ALL WORK!!)

Write the appropriate equalities, use dimensional analysis, and show all work.

1) 4600 ng to dg

2) 975 g to kg

3) 25 cs to s

4) 285 μm to m

5) 0.0005 kg to mg

6) 4568 m to km

Density Practice Problems

• Show your work, and round your answers using sig fig rules!!!

• Use the correct units. Density = g/mL or g/cm3 mass = g volume = mL or cm3

1. A cube of gold that is 2.00 cm on each side has a mass of 154.4 grams. What is the density of the gold in g/cm3? Hint: Find the volume of the cube first (l x w x h).

2. A shiny, gold colored bar of metal weighs 57.3 grams and has a volume of 4.7 cm3. Is the metal bar gold?

3. What is the volume of pure sulfur if its mass is 130 grams, and the density is 2.07 g/mL?

4. What is the mass in grams of 63,200 mL of alcohol if the density is 0.79 g/mL?

Chemistry Lab-Density

• Use UNITS on everything!

• Use the proper number of significant digits!

• Show all work in the spaces provided at the bottom of the page!

Data Table

|Metal sample (element symbol or name) | |

|Mass (2 decimal places, g) | |

|Initial volume of water (1 decimal place, mL) | |

|Final volume of water (1 decimal place, mL) | |

|Calculations | |

|Volume of metal sample (1 decimal place, mL) | |

|Density of metal (g/mL) | |

|Percent Error (%) | |

Accepted (theoretical/literature) value of density:

Copper: 8.96 g/mL Tin: 7.31 g/mL Lead: 11.35 g/mL Steel: 7.88 g/mL Aluminum: 2.7 g/mL

SHOW ALL WORK! Put your final answers in the calculations table.

GRAPHING PRACTICE

Gas Law Guided Inquiry Activity

* Graph each set of data

* Write the equation for straight line.

PRESSURE VS. TEMPERATURE ** Vol = 1.00L and mass = 1.50 g of O2 constant

(atm) (oC) K

.9869 0 _____

1.085 25.0 _____

1.184 50.0 _____

1.283 75.0 _____

1.382 100.0 _____

Identify the relationship between pressure and temperature as shown on your graph. _________________

GRAPH PAPER

VOLUME VS. TEMPERATURE** Pressure = 1.00 atm and Mass = 0.037 g O2 constant

(mL) (°C) K

17.0 -100.0 _____

26.0 0.0 _____

30.0 50.0 _____

36.0 100.0 _____

40.0 150.0 _____

Identify the relationship between volume and temperature as shown on your graph. _________________

GRAPH PAPER

PRESSURE VS. VOLUME (mL) Temperature 25 oC and mass = 0.0379 g O2 constant

(mm Hg) (mL)

760 29.0

960 23.0

1160 19.0

1360 16.2

1500 14.7

1650 13.3

Identify the relationship between pressure and volume. ______________________

How can you modify the graph to get a straight line?

Create a calculation and graph the new points showing a straight line for the data using a different color.

GRAPH PAPER

Gas Laws Notes

Gases: 4 measureable quantities:

| |Volume |Temperature |Pressure |Number of moles |

|Variable | | | | |

|Unit(s) | | | | |

We will assume the gases are ideal gases: gases that follow model behavior; gases are most likely to act ideally when the pressure is low and the temp is high (this is when gases can move freely without being attracted to each other).

STP?

Gas Pressure conversions: in packet- 1 atm = 101.3 kPa = 760 mm Hg = 760 torr (all equivalent) Pressure = force over area

Example: Convert 720 torr to kPa

You try: Convert 1.8 atm to mm Hg

GAS LAWS – Must be Memorized You Do NOT have to know the name.

Boyle’s Law V varies inversely with P P1 V1 = P2 V2

inversely proportional Graph of P vs V:

EX. If 1.0 L of a gas at 1.2 atm is allowed to expand to 5.0 L, what is the new pressure?

You try: A sample of O2 gas has a volume of 150 ml when its pressure is 720 mm Hg, what will the volume be if the pressure is increased to 750 mm Hg?

Charles law: V varies directly with the Kelvin temperature V1/T1 = V2/T2

T must be in Kelvin Directly proportional Graph of V vs T:

Ex: A helium filled balloon has a volume of 2.75 L at 20.0 0C . The volume of the balloon decreases to 2.46 L after it was placed outside on a cold day. What is the outside temperature?

You try: A sample of neon occupies a volume of 752 ml at 25 0 C. What volume will the gas occupy at 50. 0C?

Gay-Lussac’s Law: P varies directly with Kelvin Temperature P1/T1 = P2/T2

Like which other law? ____________________

Example: Before a trip from Greensboro to NY, the pressure in a tire is 1.8 atm at 20 0C. At the end of the trip the pressure gauge reads 1444 mm Hg. What is the new temperature in the tire?

You try: If the pressure of a gas at 25 0C is 3.2 atm – what would the pressure be at 55 0C?

Combined gas law: P1V1 = P2V2 T in K!!!

T1 T2

Ex: a 700. ml gas sample at STP is compressed to a volume of 200. ml, and the temperature is increased to 30.0 0C. What is the new pressure of the gas ?

You try: If 282.4 ml of a gas at 25 0C and 1.3 atm is cooled to 20. 0C and 780 mm Hg. What is the new volume?

Dalton’s law of Partial Pressure: pressure of each gas in a mixture is called the partial pressure of that gas. Total Pressure = sum of partial pressures

PT = P1 + P2 + P3 etc

Example: A 10.0L container of nitrogen and helium gases has a total pressure of 3.2 atm, if the helium’s partial pressure is 1.1 atm – what is the partial pressure of the nitrogen gas?

You try: The total pressure inside a balloon containing helium, hydrogen and oxygen is 12.2 atm – if helium’s partial pressure is 1.0 atm and hydrogen’s partial pressure is 3.0 atm– what is the partial pressure of the oxygen?

GAS LAW PROBLEMS:

Work the following problems and identify the gas law used; be sure your answer includes units!

1. A gas occupies a volume of 35.9 ml at a temperature of 22.0 C. What volume will the same gas occupy at a temperature of 28.0 C?

2. At a pressure of 780 mm Hg and 24.2 C a gas has a volume of 350.0 ml. What will the volume of this gas be under standard conditions (1 atm and 273 K)?

3. A gas occupies a volume of 24.8 ml at 725 torr. What will the pressure of the gas be at 22.5 ml?

4. At 25 0C the pressure of a gas is 1.7 atm. At what temperature will the pressure be 2.3 atm?

5. If 45.0 ml of a gas is under 1.3 atm of pressure; at what pressure will the volume be 60.0 ml?

6. A gas at a temperature of 67.5 C and a pressure of 882 torr occupies a volume of 242.2 ml. What will the volume of the gas be at 840 torr and 80.0 C?

7. A mixture of gases has a pressure of 12.2 atm; if the first gas has a pressure of 2.2 atm and the second gas has a pressure of 3.2 atm – what is the pressure of the remaining gas?

8. If 2.1 mol of a gas has a volume of 1.5 L; what will the volume of 2.7 mol of the same gas under the same conditions be?

Ideal Gas Law notes

PV = nRT

Must use the following units with the ideal gas law!

P = atm V = L T = K n = moles

R = gas constant 0.0821 L-atm/mol- K (in packet!)

Example: What is the pressure exerted by a 12.0 g sample of Nitrogen gas (N2) in a 10.0 L container at 25 0C?

You try: What is the volume of 15.0 mol of a gas at a pressure of 120 kPa and a temperature of 55 0C?

Gas Stoichiometry Notes Most of this is review!

Molar Volume 1 mol of any gas at STP has a volume of 22.4 L

1 mol = conversion factor (only to be used at STP)

22.4 L

Ex. How many moles of sulfur dioxide (SO2) are there in 98.0 ml at STP?

Worksheet Ideal Gas Law

Remember: PV = nRT

Must use atm, L, moles and K R = .0821 L-atm/mol-K

1. How many moles of oxygen will occupy a volume of 2.5 liters at 1.2 atm and 25 0C ?

2. What volume will 2.0 moles of nitrogen occupy at 720 torr and 20.0 0C?

3. What pressure will be exerted by 25 g of CO2 at a temperature of 25 0C and a volume of 500. ml?

4. At what temperature will 5.00 g of Cl2 exert a pressure of 900. torr at a volume of 750. ml?

5. How many moles of nitrogen gas will occupy a volume of 347 ml at 6680 torr and 27 0C?

6. Find the number of grams of CO2 that exerts a pressure of 785 torrs at a volume 32.5 L and a temperature of 32 0C.

7. How many moles of nitrogen gas will occupy a volume of 347 ml at 6680 torr and 27 0C?

8. What volume will 454 grams of hydrogen occupy at 1.05 atm and 25 0C? (Remember hydrogen is diatomic!)

9. Find the number of grams of CO2 that exerts a pressure of 785 torrs at a volume 32.5 L and a temperature of 32 0C.

10. An elemental gas has a mass of 10.3 g. If the volume is 58.4 L and the pressure is 758 torrs at a temperature of 2.5 0C, what is the gas (Hint find the molar mass!)

WORKSHEET IDEAL GAS LAW

1. How many moles of helium gas are there in 23 L of helium at STP?

2. What is the volume of 1.5 g of PCl gas at 545 mm Hg and 55 C?

3. How many moles of iodine gas are there in 550 ml of gas at 2.1 atm and 27 C?

Gas Review worksheet covering whole unit!

1. A cylinder of argon gas contains 50.0 L of Ar at 18.4 atm and 127 °C. How many moles of argon are in the cylinder?

2. A gas sample is at 27 °C. If the temperature is raised to 77 °C and the initial pressure was 1500 mmHg, what is the final pressure?

3. A sample of helium was compressed from a volume of 0.5 L to 0.25 L where the pressure is 500 mmHg. What was the original pressure?

4. A hot air balloonist puts 125,000 Liters of air into their balloon at 27 0C. When they heat the air to 200 °C at constant pressure, what is the final volume of the air in the balloon?

5. When measured at STP, a quantity of gas has a volume of 500 L. What volume will it occupy at 0°C and 93.3 kPa?

6. A mixture of gases contains helium with a pressure of 2.5 atm and carbon dioxide with a pressure of 4.5 atm – what is the total pressure of the container?

7. A 3.10 mL bubble of methane gas forms at the bottom of a bog where the temperature is 12oC and the pressure is 8.5 atm. The bubble rises to the surface where the temperature is 35oC and the pressure is 1.18 atm. What is the new volume of the methane bubble?

8. What is the volume of 12.5 moles of argon gas with a pressure of 3.3 atm at 25 0C.

Practice sheet #2 gas unit

Show all work – include units on the answer

1. Convert the following pressure units: A. 1.3 atm to kPa: _______________

B. 795 mm Hg to atm: _______________

2. Sketch the graph of the following pairs of variables:

|[pic] |[pic] |[pic] | |

3. A metal tank contains three gases: oxygen, helium, and nitrogen. If the partial pressures of the three gases in the tank are 35 atm of O2, 5 atm of N2, and 25 atm of He, what is the total pressure inside of the tank?

4. On hot days, you may have noticed that potato chip bags seem to “inflate”, even though they have not been opened. If I have a 250 mL bag at a temperature of 19°C, and I leave it in my car which has a temperature of 60°C, what will the new volume of the bag be?

5. If I have an unknown quantity of gas at a pressure of 1.2 atm, a volume of 31 L, and a temperature of 87°C, how many moles of gas do I have?

6. If I have 2 moles of oxygen gas at a temperature of 67°C, and a volume of 8.89 L, what is the pressure of the gas?

7. At STP how many liters are in 2.5 moles of carbon dioxide gas?

8. How hot will a 2.3 L balloon have to get to expand to a volume of 4.0 L? Assume that the initial temperature of the balloon is 25°C.

9. If I have 4 moles of a gas at a pressure of 5.6 atm and a volume of 12 L, what is the temperature?

GASES TEST REVIEW

PRACTICE PROBLEMS: Work without your notes!

1. If 259 ml of oxygen gas is at 112 kPa, what will the volume be at standard pressure?

2. A vessel with a pressure of 12.0 atm contains a mixture of helium and oxygen; if the helium exerts a pressure of 2.0 atm what is the partial pressure of oxygen?

3. What is the volume of a gas at 273 K, if it had a volume of 22.8 ml at 48 C?

4. If a 25 ml of sulfur dioxide is at 37 C and 90.2 kPa, what will the temperature be if the volume becomes 19.6 ml and the pressure is 760 torr.

5. What is the volume of 4 moles of chlorine gas at STP?

6. What is the pressure exerted by 1.32 moles of gas in an 18 L vessel at 27 C?

7. A 759 ml vessel contains 0.0945 mol of a gas at 98.6 kPa. What is the temperature of the gas?

8. What volume of hydrogen gas at STP will be produced from 0.45 moles of magnesium reacting with an excess amount of hydrochloric acid?

Test Review – Unit 2 – Honors Chemistry

Be sure to look over all info in your packet - don’t forget to review vocabulary, elements, & SI units!

Convert the following:

1. 397.2 kg to dg 2. 52.3 mL to L 3. 675 hm to miles

4. 59.3 dam/s to m/hr 5. 6.5 dg to dag

How many significant figures in each of the following?

6. 670 mm 7. 0.020 L 8. 653 kg 9. 10.0 m

10. 30. sec 11. 5050 hrs. 12. 0.01010 cm 13. 27.010 mg

14. In lab, you find the mass of a beaker to be 6.3 g; the correct mass is 6.1 g. What is your percent error?

Unit 2 PROBLEM SET:

• Follow the instructions for the cover page for Problem Sets.

• Show your work on all problems. Credit will not be given without work.

• Include units on your answers.

1. Perform the following calculations with correct significant figures:

A. 5.6531 x 2.005 = B. (5.04 – 8.23 + 22.654 + 91.0) / 3.1416 =

2.54

2. In an experiment each student needs to weigh out 1.84 g of Copper (Cu) wire. If we only have a spool of wire that weighs 50.0 g, how many students can do the experiment?

3. A dental amalgam consists of 26.0 g Ag, 10.8 g Sn, 2.4 g Cu, and 0.8 g of Zn. How much silver is in a 15.0 g sample of the amalgam?

4. You have a recipe for chili that serves ten (10) and calls for 2 teaspoons of chili powder. If you are making a batch of chili that serves 600, how many teaspoons of chili powder do you need? How many cups of chili powder is that?

5. Eggs are shipped from a poultry farm in trucks. The eggs are packed in cartons of one dozen eggs each; the cartons are placed in crates that hold 20 cartons each. The crates are stacked in the trucks, 5 crates across, 25 crates deep, and 25 crates high. How many eggs are in 5 truckloads?

6. The population of San Francisco is 750 000 in an area of 49 square miles. What is the population density in San Francisco? Express your answer in people per acre. (1 mi2 = 640 acres)

7. How many grams of glycerin, density 1.25 g/cm3, will a 125 mL flask hold?

8. What is the density of cork if a cube measuring 1.50 cm on a side has a mass of 1.0 g?

9. What is one every day application of one or more of the gas laws. Be specific and illustrate your example. (You may draw, cut out a picture, download a graphic, etc.)

10. How many moles of gas occupy 75 L at a pressure of 125.2 kPa and a temperature of 19º C?

11. A balloon is filled with 35.0 L of helium in the morning when the temperature is 20º C. By noon the temperature has risen to 45º C. What is the new volume of the balloon?

12. A helium balloon with an internal pressure of 1.0 atm and a volume of 4.5 L at 20º C is released. What volume will the balloon occupy at an altitude where the pressure is 0.600 atm and the temperature is -20º C?

13. A gas canister can tolerate internal pressures u to 210 atm. If a 2.0 L canister holding 3.5 moles of gas is heated to 1350 º C, will the canister explode? Perform the calculations and explain your answer.

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If the decimal is ABSENT

Start at the Atlantic.

Come to the first real digit and count all remaining digits

Ex.

a. 42500 _________

b. 620350 ________

c. 3625___________

If the decimal is PRESENT

Start at the Pacific.

Come to the first real digit and count all remaining digits

Ex.

a. 32.02 _________

b. 0.00235 _______

c. 75.620 ________

Limit and round to the least number of sig figs in any of the values.

23.0 cm x 432 cm x 19 cm = 188,784 cm3

The answer is expressed as 190,000 cm3 since 19 cm has only two sig figs.

Limit and r6=JKLWXjm‰œÜîðø & ' 8 9 : ; òäÙÍÁµ¬£š£?‰ƒ?|ƒ|ƒ|?riƒr‰ƒ`WNh"h6[pic]¼CJh"h÷E CJh"hã?rCJh"hp7ÀCJh"hL‰5?CJ

hUfV5?CJhÙBùCJ

hHº5?CJh"h"5?CJh÷E 5?CJaJhíHË5?CJaJh"5?CJaJh"h÷E 5?CJaJh"h"5?CJaJh"h#½5?CJaJhound your answer to the least number of decimal places in any of the numbers that make up your answer.

123.25 mL + 46.0 mL + 86.257 mL = 255.507 mL

The answer is expressed as 255.5 mL since 46.0 mL has only one decimal place.

= 3.15 x 107 s in 1 yr

= $89,352

Practice Problems:

Using the Factor Label Method, solver the following problems:

1. 3 hrs = _________ sec

2. 0.035 mg = _________ cg

3. 5.5 kg = _________lbs

4. 2.5 yds. = ________in

5. 1.3 yrs = _______ hrs.

6. 35 mL = _______ dL

7. 950 g = _______kg

8. 1,000 L = ________ kL

9. 0.005 kg = ________ Dag

10. 0.075 m = _________ cm

Final – Initial Volume = Volume of metal

Density calculation of m/V

Percent Error

In Chemistry, temperature should most often be reported in Kelvin (K). Convert the given temperature in °C to temperature in K.

273K + x°C = _______ K

Ex. 33°C to ______ K 273 + 33 = 306 K

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