Chapter 11 Homework Problems – 20 points

Ideal Gas Law/Gases and the Mole

 

Ideal Gas Law Problems:  PV=nRT 

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 H2S gas is at STP, what would its volume be in Liters? (first convert g to mole)

131 L

6.  If 50.0 g of NO2 gas is at STP, what would its volume be in Liters? (first convert g to mole)

24.3 L

 

Ideal Gas Law Problems with molecular mass:  PV = (mass/molar mass) RT

JUST A GENTLE REMINDER….. REMEMBER YOUR DIATOMIC GASES

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 SO3 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

Combined Gas Law Problems:  P1V1T2 = P2V2T1

12.  If 500. mL of hydrogen gas were collected over water at 20oC 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 27oC 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 20oC and 98.0 kPa?  111 mL

 

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

 

16.  If  oxygen gas were collected over water at 10oC originally and then it was heated up to 30oC, 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 10oC (which is 1.2 kPa for water at 10oC).  You will not need to know the vapor pressure of water at 30oC.  104 mL

Stoichiometry and Gas Laws:  MASS-GAS

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 H2SO4 to produce Na2SO4 in the following reaction.  Which reactant is the limiting reactant?  How many grams of Na2SO4 will be produced (maximum)?

NaOH is limiting reactant.  35.5 g   produced

 

                2NaOH (aq)  + H2SO4 (aq) -----ŕ  Na2SO4 (aq)  +  2H2O(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 Br2 gas will be formed (maximum)

NaBr is limiting reactant.  0.121 moles produced.

2NaBr (aq)  +  Cl2 (g)   ------ŕ  2NaCl (aq)  +  Br2 (g)

 

Density and Gas Law Problems: Old gas density (in g/mL) x (P2/P1) x (V1/V2) x (T1/T2) = 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 30oC to 50oC, what would the new density of the gas be.  Assume the volume remains constant.

17.5 g/mL

Grahm’s Law Problems:  VA/VB =   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