Gases Worksheet – Final Review!!!
Name ______________________________
You should be familiar with all of the initial gas laws we have studied…this sheet will extend our practice to
using the following concepts in gas law problems: molarity conversions; STP (yuck); limiting reactant gas
stoichiometry (that was a mouthful); and density related to the elegant “dirt-pile” equation! Good Luck!
Practice Calculation Section before the actual gas law problems begin: [answers follow]
i.
Molarity Problem: How many moles of hydrochloric acid are contained in a 450. mL sample if the
concentration is 1.25 M? [0.563 moles]
ii.
STP Problem: Determine the volume of neon gas in a balloon if the balloon contains 10.7 g of the
gas at STP. [11.9 L]
iii.
Dirt-Pile: You are given 25.5 g of gas which occupies 15.8 L. The pressure is 1.05 atm and the
temperature is 17.6 ˚C. What is the molar mass of the unknown gas? [36.6 g/mol]
iv.
Limiting Reactant: Not to be cruel…but we practiced enough of these in earlier units…if you can’t
find an example for review then your DILL and notes must have been eaten by your dog!
1. A gas is generated by reacting solutions of sulfuric acid with sodium bicarbonate (you should review the
chemical equations unit if you are unsure of the reaction). The following amounts of reactants are used
in the chemical reaction: 45.5 g of sodium bicarbonate and 250. mL of a 0.250 M sulfuric acid solution.
a) Write the balanced chemical equation.
b) Determine the limiting reactant.
c) Determine the volume of gas produced in this reaction if the temperature of the container is kept at a
steady 18.5 ˚C and the pressure is held at 755 mmHg.
d) What volume would this gas occupy if the conditions were adjusted to STP?
__________________________________________________________________________________________
2. A sample of gas has a mass of 78.8 g. The molar mass of the gas is 150. g/mol and it is maintained under
STP conditions. What volume will this gas occupy?
__________________________________________________________________________________________
3. A chemist synthesized a gaseous compound of chlorine and oxygen and finds its density is 7.71 g/L at
36.5 C and 2.88 atm. Calculate its molar mass…and if you are feeling rather intelligent and don’t mind
a challenge…determine its molecular formula. If you choose to do the molecular formula…guess and
check can yield the correct answer but a simple straightforward analysis will also succeed and is better
suited to someone of your intelligence level and mathematical prowess!
__________________________________________________________________________________________
4. A 0.13 g sample of an unknown gas is collected over water at 30.0 C. It is found that this gas displaced
85.0 mL of water in the container at an atmospheric pressure of 750. mmHg (the vapor pressure of water
at this temperature is 31.82 mmHg). Calculate the molar mass of this gas.