CHEM-121_Written Assignment 6 - Thomas Edison State College...

Thomas Edison State College
General Chemistry I with Labs (CHE-121)
Section no.: OL009
Semester and year: Feb2019
Written Assignment 6: Gases
Answer all assigned questions and problems, and show all work.
1 A gas occupying a volume of 725 mL at a pressure of 0.970 atm is allowed to expand at
constant temperature until its pressure reaches 0.541 atm. What is its final volume?
(5 points)
(Reference: Chang 5.19)
T is constant
P
1
V
1
= P
2
V
2
→ V
2
= P
1
V
1
/ P
2
= (7.25 x 0.970) / 0.541 = 1.3 L
2 The volume of a gas is 5.80 L, measured at 1.00 atm. What is the pressure of the gas in
mmHg if the volume is changed to 9.65 L? (The temperature remains constant.) (5 points)
(Reference: Chang 5.21)
V
1
= 5.80 L V
2
= 9.65 L
P
1
= 1 atm P
2
= P
1
V
1
/ V
2
= (5.80 x 1) / 9.65 = 0.60 atm = 0.60 x 760 = 456 mmHg
3 Why is the density of a gas much lower than that of a liquid or solid under atmospheric
conditions? What units are normally used to express the density of gases? (5 points)
(Reference: Chang 5.30)
Because gas molecules have a weak intermolecular interaction strength, and have large space
between them.
Normal units for gas density: g/L
4 A sample of nitrogen gas kept in a container of volume 2.3 L and at a temperature of 32°C
exerts a pressure 4.7 atm. Calculate the number of moles of gas present.