5 Steps to a 5 AP Chemistry

15.A steel tank containing argon gas has additional
argon gas pumped into it at constant tempera-
ture. Which of the following is true for the gas in
the tank?

(A) There is no change in the number of gas

atoms.

(B) There is an increase in the volume of the gas.

(C) There is a decrease in the pressure exerted by

the gas.

(D) The gas atoms travel with the same average

speed.

(E) The gas atoms are separated by a greater

average distance.

16.2 N 2 O 5 (s) → 4NO 2 (g) +O 2 (g)

A 2 L evacuated flask has a 0.2 mol sample of

N 2 O 5 (s) sealed inside it. The flask is heated to

decompose the solid and cooled to 300 K. The

N 2 O 5 (s) is completely decomposed according to

the balanced equation above. What is the nearest

value to the final total pressure of the gases in the

flask? (The value of the gas constant, R, is 0.082 L

atm mol−^1 K−^1 .)

(A) 0.6 atm

(B) 6 atm

(C) 0.05 atm

(D) 1.2 atm

(E) 3 atm

17.A glass container is filled, at room temperature,
with equal numbers of moles of H 2 (g), O 2 (g),
and NO 2 (g). The gases slowly leak out through
a pinhole. After some of the gas has effused,
which of the following is true of the relative
values for the partial pressures of the gases
remaining in the container?

(A) H 2 <NO 2 <O 2

(B) NO 2 < H 2 < O 2

(C) H 2 =NO 2 =O 2

(D) O 2 <NO 2 <H 2

(E) H 2 <O 2 <NO 2

18.Choose the gas that probably shows the greatest

deviation from ideal gas behavior.

(A) He

(B) O 2

(C) SF 4

(D) SiH 4

(E) Ar

19.Determine the formula for a gaseous silane

(SinH 2 n+ 2 ) if it has a density of 5.47 g per L at

0 °C and 1.00 atm.

(A) SiH 4

(B) Si 2 H 6

(C) Si 3 H 8

(D) Si 4 H 10

(E) Si 5 H 12

20.Which of the following best explains why a hot-

air balloon rises?

(A) The heating of the air causes the pressure

inside the balloon to increase.

(B) The cool outside air pushes the balloon

higher.

(C) The temperature difference between the

inside and outside air causes convection

currents.

(D) Hot air has a lower density than cold air.

(E) Cooler air diffuses more slowly than the

warmer air.

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