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CHAPTER 5 BASIC HOMEWORK:

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Question 1

What is the pressure in atm of 383 mmHg?
Correct

 

Explanation

1 atm = 760 mmHg


1/ 760  = X/ 383

X= 0.5039

 

Question 2

What is the pressure in torr of 1.47 atm?

Correct

 

Explanation

760 torr = 1 atm


760 /1 = X / 1.47

X= 1117.2

 

Question 3

What is the pressure in atm of a gas where n = 0.16 mol, V = 13.76 L, and T = 28.4oC?
Correct

 

Explanation

PV=nRT

28.4oC= 301.55 K

R=0.08206

P(13.76) = (0.16)(0.08206)(301.55)

P=0.2877

 

Question 4

What is the temperature in K of an ideal gas where P = 728 torr, n = 0.0271 mol, and V = 476.5 mL?
Correct

 

Explanation

PV=nRT

(728/760)(.4765)=(0.0271)(0.08206)T

=205.24

 

Question 5

How many moles of an ideal gas produce a pressure of 744 torr and a volume of 2.30 L at 285 K?

Correct

 

Explanation

PV=nRT

(744/760)(2.30L) = n (0.08206)(285)

n=0.0962744

 

Question 6

If the mass of the gas in the preceding problem is 33.1 g, what is the molar mass or molecular weight of the gas?
Correct

 

Explanation

33.1 g / X MM = 0.0962744

X=  343.81

 

Question 7

At a fixed temperature and number of moles, the initial volume and pressure of a helium gas sample are 238 mL and 685 torr, respectively. What is the final volume in mL, if the final pressure is 66.3 torr?
Correct

 

Explanation

P1V1 = P2V2

238(685) = 66.3 X

X=2458.974

 

Question 8

At a fixed temperature and number of moles of nitrogen gas, its volume and pressure are 196 mL and 687 torr, respectively. What is the final pressure in torr, if the final volume is 290 mL?

Correct

 

Explanation

196(687)= 290 X

X=464.317

 

Question 9

At a fixed pressure and number of moles, the initial volume and temperature of an air sample are 491 mL and 270 K, respectively. What is the final volume in mL, if the final temperature is 481 K?
Correct

 

Explanation

V1/T1 = V2/T2

491/270 = X/481

874.707407

 

Question 10

To what temperature in K must a variable volume container of helium gas be cooled to obtain a final volume of 0.255 L? The initial volume and temperature are 2.86 L and 332 K, respectively. The pressure and number of moles are fixed.

Correct

 

Explanation

2.86/332 = 0.255 / X

X=29.601

 

Question 11

A balloon filled with air and having no leak initially has a volume of 27.5 L, a pressure of 732 torr, and a temperature of 287 K. What is the final volume in L, if the final pressure is 489 torr and the final temperature is 244 K?

Correct

 

Explanation

P1V1/T1 = P2V2/T2

(732)(27.5)/287 = (489)T/244

T=34.997

 

Question 12

What is the total pressure if a container contains 59 torr of He gas, 234 torr of N2 gas, and 44 torr of Ar gas?
Correct

 

Explanation

59 + 234 + 44 = 337

 

Question 13

Oxygen gas is collected over water. The total pressure (the O2 pressure + the water vapor pressure) is 735 torr. The temperature of the water is such that the water vapor pressure is 44 torr. What is the partial pressure of the oxygen gas in torr?

Correct

 

Explanation

735 - 44 = 691

 

Question 14

What volume in L of chlorine at 30oC and 702 torr is required to react completely with 4.48 g aluminum:

2Al(s) + 3Cl2(g) → 2AlCl3(s)
Correct

 

Explanation

Procedure: g Al --> mol Al --> mol Cl2. Next solve for V in PV = nRT. Did you remember to convert torr to atm and C to K?


4.48 g Al / 26.981 MM  = 0.166 mol Al

0.166 mol Al  * 3 mol Cl2/ 2 mol Al = 0.24906 mol Cl2


PV= nRT

(702/760)V= (0.24906)(0.08206)(303.15)

V = 6.54

Question 15

 

The pressure on a balloon holding 411 mL of an ideal gas is increased from 211 torr to 1.00 atm. What is the new volume of the balloon (in mL) at constant temperature? 

Correct

 

Explanation

  


 (211torr) (411 mL) = (760torr) (V2)

  V2 = (211 torr x 411 mL) / (760 torr) = 114 mL 

Question 16

 

A sample of hydrogen gas (H2) is in a 2.07 L container at 531 torr and 24 C. Express the pressure of hydrogen in atm after the volume has changed to 1.30 L and the temperature is raised to 155 C.

Correct

 

Explanation

 

V1 = 2.07 L

P1 = 531 torr --> 0.699 atm

T1 = 24C --> 297 K


V2 = 1.30 L

T2 = 155C --> 428 K


P2: { (2.07 L x  0.699 atm) x (428 K) } / {(297K) x (1.3 L) } = 1.60

Question 17

 

A sample of methane gas (CH4) at 29.1 C is either heated or cooled. The pressure increases from 1.52 atm to 3.61 atm, and the volume of the sample changes from 1.83 L to 4.04 L. To what temperature, in C, was the methane heated or cooled? 

Correct

 

Explanation

 


P1: 1.52 atm 

V1: 1.83 L

T1: 29.1 --> 302.1 K


P2: 3.61 atm

V2:  4.04L


T2: (1.52 atm x 1.83 L) / (3.61 atm x  4.04L x 302.1 K) = 6.313E-4


T2: 1/ 6.313E-4 = 1583K - 273= 1310C