**Chapter 11
Homework Problems – 20 points**

**Ideal Gas
Law/Gases and the Mole**

1. If you had 50.0 L
of hydrogen gas, how many moles of gas
would you have under STP conditions?** **

**2.23 mol.**

2. If you had 1.00 L of nitrogen gas, how many moles of gas would you have under STP conditions?

**0.0446 mol.**

3. If you had 6.5 L of oxygen gas, how many moles of gas would you have under STP conditions?

**0.29 mol**

4. If 4.0 moles of bromine gas is at STP, what would its volume be in Liters?

**90. L**

5. If 200.0 g of H_{2}S
gas is at STP, what would its volume be in Liters? (first convert g to mole)

6. If 50.0 g of NO_{2}
gas is at STP, what would its volume be in Liters? (first convert g to mole)

**24.3 L**

** **

7. At STP, 1.5 L of Chlorine gas was contained. How many grams of Chlorine gas do you have?

**4.75 g**

8. At STP, 0.070 L
of SO_{3} gas was contained.
How many grams of this gas do you have?

**0.25 g**

9. What is the molecular mass of a compound if it has a volume of 0.3 L and a mass of 0.855 g at STP?

**63.8 g/mole**

10. What is the molecular mass of a compound if it has a volume of 0.250 L and a mass of 0.179 g at STP?

**16.0 g/mole**

11. What is the molecular mass of a compound if it has a volume of 0.400 L and a mass of 2.28 g at STP?

**128 g/mole**

12. If 500. mL of
hydrogen gas were collected over water at 20^{o}C and 120 kPa, what
would the volume be if you changed the conditions to STP? **551
mL**

13. If 250. mL of oxygen gas were collected over water at 27^{o}C
and 95.0 kPa, what would the volume be if you changed the conditions to
STP? **213 mL**

14. If 100. mL of chlorine gas were collected over water at
STP , what would the volume be if you changed the conditions to 20^{o}C
and 98.0 kPa? **111 mL**

15. If 140. mL of hydrogen gas were collected over water at
15^{o}C and 110 kPa , what would the volume be if you changed the
conditions to 40^{o}C and 94.5 kPa?
**177 mL**

16. If oxygen gas were collected over water at 10^{o}C
originally and then it was heated up to 30^{o}C, what would its new
volume in mL be if it had an original volume of 100 mL. The initial pressure of the gas was 15.0 psi
and the final pressure of the gas was 105 kPa.
You can assume that the partial pressure of the water on the gas only
affected it originally. That means the
original pressure of the gas is the gas pressure plus the water vapor pressure
at 10^{o}C (which is 1.2 kPa for water at 10^{o}C). You will not need to know the vapor pressure
of water at 30^{o}C. **104 mL**

REMEMBER: TAKE VOLUMES GIVEN TO YOU AND PUT THEM IN THE PV=nRT EQUATION BEFORE BEGINNING. YOU ARE SOLVING FOR n (Number of moles)

** ASSUME STP CONDITIONS UNLESS
OTHERWISE STATED**

17. 4.00 g of zinc (oxidation number: +2) react with hydrochloric acid. How many LITERS of hydrogen gas are liberated? Assume you have an excess amount of HCl. (this is a single displacement rxn)

**1.37 L**

18. An excess amount of Chlorine gas reacts with 20.0 g of Potassium bromide. How many L of Bromine gas are liberated? (this is a single displacement rxn)

**1.88 L**

19. If you have 10.0 L of hydrogen gas, how many grams of copper (II) oxide are going to be required to react with the hydrogen to produce product? (this is a single displacement rxn)

**35.5 g**

20. If you have 5.00 g of dihydrogen monoxide, how many Liters of oxygen can be produced from this decomposition reaction?

**3.11 L**

21. If you have 5.00 L of oxygen and react it with Aluminum to produce Aluminum Oxide (in a synthesis reaction), how many grams of aluminum are required to react with the oxygen?

**8.04 g**

** **

**Stoichiometry and Gas
Laws: GAS-GAS**

**REMEMBER: IF AMOUNTS ARE GIVEN AS VOLUMES, YOU CAN GO
DIRECTLY TO THE MOLE/MOLE RATIO SO LONG AS YOU ARE COMPARING GAS TO GAS SO LONG
AS THE TEMPERATURE AND PRESSURES REMAIN CONSTANT.**

** ASSUME STP CONDITIONS UNLESS
OTHERWISE STATED**

22. How many Liters of hydrogen gas are required to completely react with 0.075 L of oxygen gas to produce dihydrogen monoxide?

**0.150 L**

23. How many Liters of Chlorine gas are required to produce 0.050 L of hydrogen chloride gas when hydrogen and chlorine are mixed together to make hydrogen chloride gas?

**0.025 L**

Stoichiometry and Gas Laws and limiting reagents:

24. 20.0g of NaOH
react with 30.0 g of H_{2}SO_{4} to produce Na_{2}SO_{4}
in the following reaction. Which
reactant is the limiting reactant? How
many grams of Na_{2}SO_{4} will be produced (maximum)?

2NaOH
(aq) + H_{2}SO_{4} (aq)
-----ŕ Na_{2}SO_{4} (aq) + 2H_{2}O(l)

25. 3.00 L of
Chlorine gas react with 25.0 g of NaBr in the following reaction. Which reactant is the limiting
reactant? How many moles of Br_{2}
gas will be formed (maximum)

NaBr is limiting reactant. 0.121 moles produced.

2NaBr (aq) + Cl_{2}
(g) ------ŕ 2NaCl (aq)
+ Br_{2} (g)

**Density and Gas Law
Problems:** **Old gas density (in g/mL)
x (P _{2}/P_{1}) x (V_{1}/V_{2}) x (T_{1}/T_{2})
= new gas density (in g/mL)**

26. If the original density of a gas were 20.0 g/mL and the pressure was increased from 14.7 psi to 18.0 psi and the volume were decreased from 100 mL to 50 mL, what would the new density of the gas be. Assume the temperature remains constant.

**49 g/mL**

27. If the original
density of a gas were 55.0 g/mL and the pressure was decreased from 14.7 psi to
5.00 psi and the temperature was increased from 30^{o}C to 50^{o}C,
what would the new density of the gas be.
Assume the volume remains constant.

**17.5 g/mL**

**Grahm’s Law
Problems: V _{A}/V_{B}
= _{} Remember: Smaller is A. Bigger is B.**

28. Compare the velocity of oxygen to hydrogen

hydrogen if 4 times as fast.

29. Compare the velocity of Krypton to Oxygen

**oxygen is 1.62 times
as fast**

30. Compare the velocity of Chlorine to Oxygen

**oxygen is 1.49 times as
fast**

** **