CHM 2045 Module Six Sample Exam Part E: Answers

Module Six Part E Gas Law Problems                            10 points

Boyle’s Law

1.  A sample of a gas has a volume of 100 mL when measured at 25 oC and

760 mmHg.  What volume will the gas occupy at 25 oC and 380 mmHg?

V1P1=V2P2

100 mL      X        760 mmHg      =      200 mL  (answer)

1                      380 mmHg

Charles Law

2. The volume of a gas is 100.0 mL at 27 oC.  At what temperature in degrees Celsius would the volume of the gas be 200.0 mL, assuming the pressure remains constant.

V1  =  V2                V2 T1__      =     T2

T1      T2                    V1

200.0 mL x 300 K    =   600 K (answer)

100.0 mL

Dalton’s Law of Partial Pressures

3. The volume of hydrogen collected over water is 200 mL at 25 oC and 763.8 torre.  Calculate the dry volume in milliliters of 200 mL of hydrogen gas collected over water at 25 oC at 760 torre pressure with the temperature remaining constant.  (The partial pressure of water vapor at 25 oC is 23.8 torre.)

Ptotal =  PH2 dry  + PH2O         PH2 dry  =  763.8 torre – 23.8 torre  =  740.0 torre

V1P1=V2P2

200 mL  x   740 torre       =   194.8 mL (Answer)

760 torre

Ideal Gas Equation-Combined Gas Laws

5. Calculate the number of moles of nitrogen gas in a 5.00 L cylinder at 27 oC and 4 atm pressure. R = 0.0821 L atm/ K mole ) How much does this volume of gas weigh?

PV = nRT

4 atm x 5.00 L                            =    0.813 mol

300 K  x 0.08205 L atm/Kmol

.813 mol x 28.0 g/mol = 22.8 g (answer)

Kotz Paper and Pencil Homework:

Boyles Law:               Questions 5, 6 p 580

Charles Law:              Questions 7, 8 p 580

Combined Gas Law:  Questions 9-14 p 580-16

Dalton’s  Law:            Questions 37-40 p582

Ideal Gas Behavior and Gas Law: Questions 17-22 p 581