# Reg. Chemistry ~ Gases Test ~ 1997 - 1998

I. Multiple Choice Questions - Choose the best answer for each question.

1.)  A 15.0 liter gas sample is heated from 29 oC to 67 oC at constant pressure conditions.
Under these conditions, which of the following statements is correct?
(A) the number of moles of gas increases
(B) the number of moles of gas decreases
(C) the volume decreases
(D) the volume increases
(E) none of the above are correct

2.)  A sample of CO2 gas occupies 3.0 L at 35 oC and 1.0 atm.  What is the new volume if
the temperature and pressure are changed to 48 oC and 1.5 atm?
(A) 3.0 L            (B) 1.9 L            (C) 4.7 L            (D) 4.3 L            (E) 2.1 L

3.)  If 10.7 liters of a gas at 35.0 oC has its temperature increased to 50.0 oC, what is the
new volume?
(A) 7.3 L            (B) 10.2 L            (C) 11.2 L            (D) 15.9 L

4.)  In the ideal gas equation, the ideal gas constant (R) is equal to
(A) n T          (B) P V             (C) P V T           (D)    n             (E)   V T
P V                n T                      n                    P V T                 n P

5.)  Boyle's Law relates pressure and volume.  What is the equation for Boyle's Law?
(A) P1 V1 = P2 V2            (B) P1 = P2           (C) P1 + V1 =         (D) P V = n R T
V1      V2                          P2 + V2

6.)  If 0.50 moles of helium are placed inside a 1.50 L container at 77 K, what is the pressure
exerted by the helium gas?
(A) 0.48 atm                (B) 1.2 atm                (C) 2.1 atm
(D) 3.7 atm                  (E) 4.5 atm

7.)  In order to solve a problem using the ideal gas equation, how many values must be given
to solve the problem?
(A) 1            (B) 2            (C) 3            (D) 4            (E) 5

8.)  Which of the following is/are constant in the equation for Boyle's Law?
(I) Pressure            (II) Volume            (III) Moles            (IV) Temperature
(A) I only                    (B) II and III only            (C) I and IV only
(D) I, II, and IV only    (E) III and IV only

9.)  If a gas at 2.9 atm and 34 oC has its pressure decreased to 2.4 atm, what is the new
temperature of the gas?
(A) 147 K            (B) 254 K            (C) 147 oC            (D) 254 oC            (E) 28 oC

10.)  How do you convert from degrees Celsius to Kelvins?
(A) add 100            (B) subtract 173            (C) subtract 273
(D) subtract 100      (E) add 273

11.)  The quantity of a gas is measured in
(A) Kelvins            (B) Liters            (C) Atmospheres            (D) Moles

12.)  The average kinetic energy of the molecules of a gas is determined by the __ of the gas.
(A) quantity                (B) mass            (C) pressure
(D) temperature          (E) volume

II.  Solve each of the following problems.  (You must show your work!)

1.)  A 5.00 liter container is filled with N2 gas at a pressure of 3.00 atm and 250 oC.  What
is the volume of the container that is used to hold the same gas at STP (standard
temperature and pressure)?

2.)  What volume of N2 gas at 0.947 atm and 23 oC is required to react with 7.35 liters of H2
gas at the same temperature and pressure?        N2  +    H2  -->    NH3

3.)  How many liters of O2 gas at STP are evolved when 3.25 grams of KNO3 decomposes to
KNO2 and O2?            KNO3  -->    KNO2  +    O2

4.)  What is the volume of 0.55 moles of an ideal gas that is at 1.03 atm and 94 oC?

5.)  If a gas has an initial pressure of 1.45 atm and an initial volume of 23.0 liters, what is its
final volume if the pressure is increased to 2.43 atm?

6.)  a.)  In an experiment, a student is to determine the molar mass of an unknown gas.
During the experiment, the student measures the following data:
The mass of the gas is 0.65 grams.  The pressure is 1.07 atm.  The volume is
350 mL.  The temperature is 21.5 oC.  What is the molar mass of the gas?

b.)  Later, it is revealed that the unknown gas is propane (C3H8).  What is the student's
percent error?