Gas Laws

SAMPLE PROBLEM 6
Chlorine gas is collected by water displacement at a temperature
of 19°C. The total volume is 1.45 L at a pressure of
156.5 kPa. Assume that no chlorine gas dissolves in the water.
What is the volume of chlorine corrected to STP?
SOLUTION
1. ANALYZE
• What is given in the the total initial volume, pressure,
problem? and temperature; the fact that the
gas was collected by water displacement;
and the final temperature and
pressure of the chlorine
• What are you asked to find? the volume of chlorine at STP
Items Data
Total original volume, V 1
Total original pressure, P total
Original temperature, t 1
Original Kelvin temperature, T 1
132 Chapter 11
1.45 L
156.5 kPa
19°C
Vapor pressure of water at 19°C, 2.19 kPa
Pressure of collected Cl 2, P 1
New volume, V 2
New pressure, P 2
New temperature, t 2
New Kelvin temperature, T 2
P H2O
(19 273) K 292 K
? kPa
? mL
101.3 kPa
0°C
273 K
2. PLAN
• What steps are needed to Use Dalton’s law of partial prescalculate
the volume of the sures to determine the pressure of
chlorine at STP? the chlorine alone in the container.
Use the combined gas law to solve
for the new volume.
P 1 given
P total from table
P H2O vapor
Calculate the volume of chlorine at STP using the following equation.
P 1V 1
T 1
P 2V 2
T 2