proportionalTo do List

Gas Laws Practice Test

Solutio n Set

1. A Which ofthe following conditions would cause a gas to deviate most from idealbehavior?

A) -200oC and 50 atm; B)STP; C)200 K and 500 psi; D)2000oC and 500 mmHg.

(low T&high P)

2. F Which ofthe following gases would have the greatest average kinetic energy,assuming that allgases are at the same average temperature?

A)helium; B)xenon; C)carbon dioxide; D)ammonia; E)carbon monoxide;

F)all gases have the same average kinetic energy at a given temperature.

3. E Assume that you have 2.0 moles of gas at a certain temperature,pressure,and volume. If both thepressure and absolute temperature are tripled,what will be the final volume?

A)nine times as great as the initial volume; B)nine times less than the initial voume;

C) three times as great as the initial volume; D) three times less than the initial voume;

E) there will be no change in volume; F)final volume will be greater,but not nine times greater.

4. C One way to increase the average speed of the molecules ofan ideal gas is to:

A)decrease the temperature; B)expand the gas against a piston; C) increase the pressureby increasing the number of molecules in a confined volume(a container that has a fixed volume);

D)expanding the gas into a vacuum.

5. A Density is a characteristic property for any gas,but the temperature and pressure must also bespecified because:

A)density increases with increasing pressure at a given temperature;

B)density decrease s with increasing pre ssure at a given temp erature;

C)density increases with increasing temperature at a given pre ssure;

D)density increases with decreasing pres sure and increased temperature.

6. E Which ofthe following would cause an increase inthe pressure ofa gaseous system?

A)container is made larger,with temperature and moles constant;

B)additional amount of the gas is added,with volume and temperature kept constant;

C) temperature is decreased,with moles and volume constant;

D)another gas is added to the system,with volume and temperature kept constant;

E)both B and D would increase pressure.

7. C What is the relationship ofthe mass ofa gaseous molecule compared to its velocity,assuming thattemperature,pressure,and volume are kept constant?

A) inversely proportional; B)directly proportional; C) inversely proportional to the squareroot; D)directly proportional to the square of the velocity.

8. E At extemely highpressures,which of the following molecules would be expected to show themost deviation from ideal behavior?

A)neo n; B)hydro ge n; C)argo n; D)o xyge n; E)d initro ge n pe nto xide;

F)all would deviate equally.

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9. B What is the molecular weight ofa gas if 0.3350 grams in a 30.0 ml container exerts a pressure of

20.3 psi at a temperature of-20.0?

A)88.6; B) 168; C) 127; D)32.7; E)355; F)22.9

MW=gRT/PV=[(0.3350 g)(0.0821)(253 K)] / [(20.3 psi/14.7 psi)(0.0300 liters)]

MW=167.96g/mol

10. B How many seconds will it take for 750 ml of xenon gas to effuse from an effusion chamber if ittakes 23.3 seconds for 750 ml of nitrogen gas to effuse?

A)71.4; B)50.5; C) 109; D) 10.8; E)4.69; F)23.3

=> Time Xen on/23.3 = 131.3/28.0

TimeXenon=50.5 sec.

11. E A sample of gas is put into a container that has a movable piston. Initially the volume is 4.00 literswhenthe pressure is 60.0 cm Hg and the temperature is 50.0the pressure is tripled(up to 180.0 cm Hg)and the temperature is also tripled(up to 150.0)?

A)0.444; B)36.0; C)4.00; D)8.85; E) 1.75; F)2.85

V1 P1 /T1 =V2 P2 /T2

V2 = [(4.00 liters)(60.0 cm)/ (323 K) ] / [(423 K)/(180.0 cm)] = 1.75 liters

12. A A three-gas system composed of neon,helium,and oxygen gas exerts a total pressure of 990.0 torr.Ifthe combined number of moles ofboth helium and neon is 10.0 moles,and the mass ofoxygenis 160.0 grams,what is the partialpressure exerted bythe oxygen gas?

A)330; B) 155; C) 165; D)660; E)495; F)990noxygen=160.0 g/32.0 g/mol=5.00 moles

Poxygen= 990.0 torr(5.00 mol/15.0 mol)=330.0 torr

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13. C A student uses a manometer to determine the pressure of a confined gas in the lab. The barometershows that the atmosphe ric pressure is 28.80 inches Hg. The height ofthe mercury at the closedend of the manometer is 8.85 inches lower than the height of mercury at the open end.What isthe pressure of the confined gas (in atmospheres)?

A)597; B)225; C) 1.26; D)0.667; E) 1.33; F)0.963

Pgas=Patm+Ph=28.80 in.Hg+8.85 in.Hg =37.65 in.Hg = 1.26 atm.

14. D What is the density of bromine vapor(in grams/liter)at 775?

A)70.1; B)0.0556; C)3.38; D) 1.38; E)2.99; F) 1.72.

D= g/V=MWx P/RT

D= [(159.8 g/mol)(75.5 kPa/101.3 kPa)] / [(0.0821)(1048 K)]

D= 1.38 g/lite r

15. D 775 ml ofa gas is collected over water at a temperature of 23.0pressure of 12.20 psi.What would be the volume(in ml)of the dry gas at STP?

(Equilibrium vapor pressure ofwater vapor at 23.0.)

A)682; B)415; C)521; D)563; E)329; F)619.

V1 P1 /T1 =V2 P2 /T2

V2 = [(775 ml)(12.20 psi-0.62 psi)/(296 K) ] / [(273 K)/ (14.7 psi)] = 563 ml

16. B What is the density(in grams per liter)of sulfur dichloride vapor at STP conditions?

A) 1.24; B)4.60; C)22.4; D) 103.1; E)3.84; F)0.896

103.1 g/mol x 1 mol /22.4 liters = 4.60 g/liter

17. 82.8% A student reacts 1.50 moles of solid aluminum metal with an excess of 6.0 M sulfuric acid at

55.

What is the percent yield of this reaction? The aqueous vapor pressure at 55atmospheres. The other product is aluminum sulfate,but you knew that!

2 Al(s) +3 H2SO4(aq) --> 3 H2(g) + Al2(SO4)3(s)

1.50 mol Al x[3 mol H2 /2 mol Al ]=2.25 moles H2

V=nRT/P = [(2.25 mol)(0.0821)(328 K)] / [(0.445-0.045 atm)]V= 151 liters (theoretically) %yield=125/151 x 100=82.8%