116 ❯ STEP 4. Review the Knowledge You Need to Score High
- A reaction produces a gaseous mixture of carbon
dioxide, carbon monoxide, and water vapor. After
one experiment, the mixture was analyzed and
found to contain 0.60 mole of carbon dioxide,
0.30 mole of carbon monoxide, and 0.10 mole of
water vapor. If the total pressure of the mixture
was 0.80 atm, what was the partial pressure of the
carbon monoxide?
(A) 0.080 atm
(B) 0.34 atm
(C) 0.13 atm
(D) 0.24 atm - A sample of methane gas was collected over
water at 35°C. The sample had a total pressure
of 756 mm Hg. Determine the partial pressure
of the methane gas in the sample. The vapor
pressure of water at 35°C is 41 mm Hg.
(A) 760 mm Hg
(B) 41 mm Hg
(C) 715 mm Hg
(D) 797 mm Hg - A student has three identical 2.0 L flasks (A, B,
and C) all at 298 K. Each flask has an 8.0 g sample
of gas sealed inside. Flask A contains methane,
CH 4 ; flask B contains hydrogen, H 2 ; and flask C
contains helium, He. Rank the three flasks in
order of decreasing pressure.
(A) A > B > C
(B) B > C > A
(C) C > A > B
(D) All three flasks are at the same pressure. - An ideal gas sample weighing 1.28 g at 127°C
and 1.00 atm has a volume of 0.250 L. Determine
the molar mass of the gas.
(A) 322 g/mole
(B) 168 g/mole
(C) 0.00621 g/mole
(D) 80.5 g/mole - Increasing the temperature of an ideal gas from
50 °C to 75°C at constant volume will cause
which of the following to increase for the gas?
(A) the average molecular mass of the gas
(B) the average distance between the molecules
(C) the average speed of the molecules
(D) the density of the gas
12. If a sample of CH 4 effuses at a rate of 9.0 moles
per hour at 35°C, which of the following gases
will effuse at approximately twice the rate under
the same conditions?
(A) CO
(B) He
(C) O 2
(D) F 2
13. A steel tank containing argon gas has additional
argon gas pumped into it at constant temperature.
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.
14. Choose the gas that probably shows the greatest
deviation from ideal gas behavior under a given
set of conditions.
(A) He
(B) O 2
(C) SF 4
(D) SiH 4
15. Determine the formula for a gaseous silane
(SinH2n+ 2 ) if it has a density of 5.47 g/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
16. 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 moving outside air pushes the balloon
higher.
(C) The temperature difference between the
inside and outside air causes convection cur-
rents.
(D) Hot air has a lower density than cold air.