Question 1 A sample of O 2 gas is placed in a flexible container with a volume o

Question

Question 1

A sample of O2 gas is placed in a flexible container with a volume of 2.0 L at 298 K. If the pressure is held constant, what will happen to the volume when the temperature is decreased to 250 K, and why?

The volume will increase because the gas particles are moving faster and colliding with the walls of the container more frequently.

The volume will increase because the gas density has increased.

The volume will not change because temperature and volume are unrelated.

The volume will decrease because the size of the gas particles has decreased.

The volume will decrease because the gas particles are moving more slowly and colliding with the walls of the container less frequently.

1 points   

Question 2

A student has samples of five gases. If the temperature of these samples is the same, which gas will have particles with the slowest average velocity?

N2

H2

O2

CO2

Ar

1 points   

Question 3

A gas mixture has a pressure of 10.0 atm and is composed of N2 gas, O2 gas, and Ar gas. If the N2 gas has a pressure of 5.0 atm and the O2 gas has a pressure of 3.0 atm, what is the pressure of the Ar gas?

2.0 atm

3.0 atm

5.0 atm

8.0 atm

10.0 atm

1 points   

Question 4

What is the density (g/L) of propane (C3H8) at STP (1 atm, 273 K)?

0.65 g/L

44.1 g/L

3.41 g/L

1.97 g/L

1.13 g/L

1 points   

Question 5

An unknown gas effuses through a porous barrier at a rate that is 0.752 times the rate of Ar (g) under the same conditions. Which of the following is the unknown gas?

H2 (g)

N2 (g)

O2 (g)

Cl2 (g)

He (g)

The volume will increase because the gas particles are moving faster and colliding with the walls of the container more frequently.

The volume will increase because the gas density has increased.

The volume will not change because temperature and volume are unrelated.

The volume will decrease because the size of the gas particles has decreased.

The volume will decrease because the gas particles are moving more slowly and colliding with the walls of the container less frequently.

Explanation / Answer

1) Given pressure is constant

so according to charles law

Volume is proportional to temperature

as temp is decreased , volume should also be decreased

so the answer is The volume will decrease because the gas particles are moving more slowly and colliding with the walls of the container less frequently.

2) average velocity = sqrt ( 8RT / pi x M )

so the gas with higher molar mass will have slowest average velocity

so the answer is C02

3) total pressure = pN2 + p02 + pAr

10 = 5 + 3 + pAr

pAr= 2

pressure of argon gas is 2 atm

4)

PM= dRT

d= PM / RT

d= 1 x 44 / 0.0821 x 273

d = 1.97 g/ L

5) for effusion

r2/r1 = sqrt ( M1/M2 )

0.752 = sqrt ( Mar / M2)

0.752 = sqrt ( 40 / M2)

M2 = 70.73

molar mass of unknown gas is 70.73 g

so the answer is Cl2

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