Name
Date
Pd
Unit 2 Worksheet 3 – PVTn Problems
On each of the problems below, start with the given P, V, T, or n; then make a decision as to how a
change in P, V, T, or n will affect the starting quantity, and then multiply by the appropriate factor.
Draw particle diagrams of the initial and final conditions.
1. A sample of gas occupies 150 mL at 25 ˚C. What is its volume when the temperature is
increased to 50˚C? (P and n = constant)
Initial
Final
Effect
P
----
T
298K
323K

V
150mL
?

n
----
V2  150 mL 
323 K
 163mL  160 mL
298 K
2. The pressure in a bicycle tire is 105 psi at 25˚C here in Fresno. You take the bicycle up to
Huntington, where the temperature is – 5˚C. What is the pressure in the tire? (V and n =
constant)
Initial
Final
Effect
P
105psi
?

T
298K
268K

V
----
n
----
P2  105 psi 
268 K
 94.4 psi
298 K
3. What would be the new pressure if 250 cm3 of gas at standard pressure is compressed to a
volume of 150 cm3 ? ( T, n
= constant)
Initial
Final
Effect
P
1atm
?

Modeling Chemistry
T
----
V
250cm3
150cm3

n
----
250 cm3
 1.7 atm
150 cm3
or 1300 mmHg
or 170 kPa
or 25 psi
P2  1atm 
1
U2 ws 3 v2.1
4. What would be the new volume if 250 cm3 of gas at 25˚C and 730 mm pressure were changed to
standard conditions of temperature and pressure? (__n__= constant)
P
Initial
Final
Effect
730mmHg
760mmHg

T
298K
273K

V
250cm3
?
 
P T
n
----
V2  250cm3 
730 mmHg 273 K

 220cm3
760 mmHg 298 K
5. Sam’s bike tire contains 15 units of air particles and has a volume of 160mL. Under these
conditions the pressure reads 13 psi. The tire develops a leak. Now it contains 10 units of air
and has contracted to a volume of 150mL). What would the tire pressure be now?
Initial
Final
Effect
P
13psi
?
 
V n
T
----
V
160mL
150mL

n
15u
10u

P2  13 psi 
160 mL 10u

 9.2 psi
150 mL 15u
6. A closed flask of air (0.250L) contains 5.0 “bobs” of particles. The pressure probe on the flask
reads 93 kPa. A student uses a syringe to add an additional 3.0 “bobs” of air through the stopper.
Find the new pressure inside the flask.
Initial
Final
Effect
P
93kPa
?

T
----
V
----
n
5bobs
8bobs

P2  93kPa 
8bobs
 150 kPa
5bobs
7. A 350 mL sample of gas has a temperature of 30˚C and a pressure of 1.20 atm. What
temperature would needed for the same amount of gas to fit into a 250 mL flask at standard
pressure?
Initial
Final
Effect
P
1.2atm
1atm

Modeling Chemistry
T
303K
?
 
P V
V
350mL
250mL

n
----
T2  303 K 
2
1atm 250 mL

 180 K
1.2atm 350 mL
U2 ws 3 v2.1
8. A 475 cm3 sample of gas at standard temperature and pressure is allowed to expand until it
occupies a volume of 600. cm3. What temperature would be needed to return the gas to standard
pressure?
Initial
Final
Effect
P
----
T
273K
?

V
475cm3
600cm3

n
----
T2  273 K 
600cm3
 345 K
475cm3
9. The diagram below left shows a box containing gas molecules at 25˚C and 1 atm pressure. The
piston is free to move.
In the box at right, sketch the arrangement of molecules and the position of the piston at standard
temperature and pressure. Does the volume decrease significantly? Why or why not?
273 K
298 K
V2  0.92 V1
V2  V1 
Modeling Chemistry
The volume will decrease
by about 10%.
3
U2 ws 3 v2.1