CHEM 141 Gas Law Spots
Practice problems from Chapt. 5 Tro: (recommended additional problems, do not turn in)
41, 43, 45, 47, 49, 53, 55, 57, 59, 61, 63, 65, 69, 71, 73, 75, 77, 79, (**highly recommended)
1.
Consider the following container that has been charged with 3 different gases represented by triangles,
squares and circles. You may assume that each shape represents one mole of a particular gas. The
temperature of the container and its volume remain constant throughout the filling process. Fill in the
blanks for each requested pressure. **Extensive CALCULATIONS are NOT NEEDED**
4
Pressure of
Total Pressure:
: 4 atm
2
Pressure of
:
Pressure of
:
Pressure of
:
Pressure of
:
Pressure of
:
Total Pressure:
Total Pressure:
2. In NASCAR racing, tire pressure is an important factor for the handling of the racecar. If the inside
pressure of a racing tire is 1.80 atm at a temperature of 20C. What will the pressure in the tire be, if after
10 laps, the temperature of the tire increases to 57C? (20 pts)
3.
Sulfur, S, forms a number of molecular (and ionic) compounds with Fluorine, F. One of these molecular
compounds, SFn, produced 41.95 mL of gas at 50C and 820 torr when a 0.250 g sample of SFn was
vaporized (ie. heated to form a gas)
(a) What is the molecular weight of this compound? (15 pts)
(b) What is the likely molecular formula for this compound? (10 pts)
4.
An unknown metal M reacts with excess hydrobromic acid according to the following equation
2 M (s) + 6 H+ (aq) -----→ 2 M3+ (aq) + 3H2 (g)
If 198.56 mL of hydrogen gas is collected at 27C and 760 mmHg when 0.300 g of M (s) are treated with
excess HBr (aq) (mol. wt. 80.912 g/mol), what is the identity of M (s)? (Hint: to identify M you will need
to find its atomic weight; g M/mol M)
5.
A 0.500 g sample of an unknown transition metal chloride (MClx) was treated with an excess of aqueous
silver nitrate producing 1.51 g of silver chloride. In a second experiment 0.200 g of the compound was
heated to 150°C causing the compound to evaporate. The resulting gas occupied a volume of 50.0 mL
with a pressure of 0.732 atm.
(a)
What is the molecular weight of the unknown compound? (10 pt)
(b)
What is the identity and molecular formula of this transition metal chloride (assume it contains only one
metal atom per formula unit)? (20 pt)
6.
An empty 2.0 L soda bottle is tightly capped at 22C and 0.90 atm. If the bottle is placed in a water bath at
95C, what is the pressure in the bottle after it warms up?
7. When hydrogen sulfide (H2S, MM = 34.08 g/mol ) gas is bubbled into a solution of sodium hydroxide
(NaOH, 40.00 g/mol), sodium sulfide (Na2S, 78.04 g/mol) and water (18.02 g/mol) are produced according
to the balanced chemical equation shown below?
H2S + 2 NaOH --------->
Na2S + 2 H2O
(a) Assuming the reaction goes to completion, how many grams of sodium sulfide are formed if 1.25 L of
hydrogen sulfide at a pressure of 1.4 atm and a temperature of 25C is bubbled into a solution containing
0.750 L of a 0.05 M NaOH (aq) solution?
(c) If only 0.400g of sodium sulfide was recovered, what is the percent yield of this reaction (5 pts)
8.
Chlorine gas reacts with acidic aqueous solutions of sulfite ion to produce sulfate and chloride ions
according to the following balanced equation
Cl2 (g)
+
SO32- (aq)
+
H2 O 
2 Cl1-(aq)
+
SO42- (aq)
+ 2 H+
In an experiment 10 L of chlorine was bubbled through a reaction flask at 0°C and 760 mm Hg containing
100 mL of a 0.45 M solution of sodium sulfite. The resulting solution was then treated with an excess of
aqueous silver nitrate.
(a)
How many grams of silver chloride are expected to be recovered from the reaction?
(b)
If 11.45 g of silver chloride were actually obtained form the reaction, what is the percent yield of the
reaction?
9. A sealed syringe has 25.0 mL of nitrogen, N2 (B.P. = -196C) at 23C and 732 mm Hg pressure. The
syringe is placed in a water bath at 92C and the volume of the gas expands to 27.5 mL. What is the
pressure of the gas after it is placed in the bath.
10. Zinc metal is an active metal and will readily dissolve when placed in acidic solutions. For example zinc
metal reacts with hydrochloric acid to form hydrogen gas and aqueous zinc chloride.
a) Write a balanced chemical equation for this reaction including phases for all species. What type of reaction
is this?
b) Calculate the mL of hydrogen gas produced at 26.0C and 0.930 atm when 6.00 grams of zinc are placed in
a 250 mL flask containing 75.0 mL of 1.65 M hydrochloric acid.