chapter 12 gases. what is the pressure of the gas in the bulb? 1. p gas = p h 2. p gas = p atm 3. p...

Chapter 12Gases

What is the pressure of the gas in the bulb?

1. Pgas = Ph

2. Pgas = Patm

3. Pgas = Ph + Patm

4. Pgas = Ph - Patm

5. Pgas = Patm - Ph

If 250 mL of NO is placed in a flask with O2, what volume of O2 is needed for complete reaction?

1. 100 mL2. 125 mL3. 200 mL4. 250 mL5. Cannot be determined from the given information.

2 NO (g) + O2 (g) 2 NO2 (g)

If an equal mass of each gas is put into a separate balloon, which will have the greatest

volume? Assume that they are all the same temperature

and pressure.1. He

2. H2

3. N2

4. Ne

5. O2

If equal masses of CH4, C2H6, and C3H8 are placedin a flask, which of the following is true?

1. PCH4 = PC2H6

= PC3H8

2. PCH4 ~ PC2H6

~ PC3H8

3. PCH4 > PC2H6

> PC3H8

4. PCH4 < PC2H6

< PC3H8

5. None of the above

Arrange the gases according to increasing molecular speed.

1. He (25) < He (100) < Ne (25) < Ne (0)2. He (25) < He (100) < Ne (0) < Ne (25)3. Ne (0) < Ne (25) < He (25) < He (100) 4. Ne (25) < Ne (0) < He (100) < He (25)5. Ne (0) < He (25) < Ne (25) < He (100)

He (25°C) He (100°C) Ne (25°C) Ne (0°C)

If a mixture of gas A and gas B is moved from flask 1 to flask 2, which of the following is true:

1. PA, PB, and Ptot decrease

2. PA, PB, and Ptot increase

3. PA and PB decrease, Ptot remains the same

4. PA, PB, and Ptot remain the same

5. PA and PB remain the same, Ptot decreases

flask 1 flask 2

A gas initially at 2.0 atm is in an adjustable volume container of 10. L in volume. If the pressure is decreased to 0.50 atm, what is the new volume?

1. 40. L2. 20. L3. 10. L4. 5.0 L

Correct Answer:

PV

1constant

constantPV

Thus,

2.00 atm(10. L) = 0.50 atm (Vfinal)Vfinal = 2.00 atm(10. L)/0.50 atm =

40. L

1. 40. L2. 20. L3. 10. L4. 5.0 L

Assuming pressure is held constant, to what volume will a balloon initially at 1.0 L change if its temperature is decreased from 300 K to 75 K?

1. 1.0 L2. 2.0 L3. 0.25 L4. 4.0 L

Correct Answer:

TV constant

constantT

V

Thus,1.0 L/300 K = (Vfinal)/75 K

Vfinal = 75 K/(1.0 L)300 K = 0.25 L

1. 1.0 L2. 2.0 L3. 0.25 L4. 4.0 L

At standard temperature and pressure, how many moles of gas are present in a box with a volume of 112 L?

1. 1.00 moles2. 2.00 moles3. 5.00 moles4. 0.200 moles

Correct Answer:

L 22.41

atm 1.000

K 273.15KL·atm/mol· 0.08206mol 1

P

nRTV

nRTPV

Thus, at STP

22.41 L = 112 L1.00 mol n

n = 5.00 moles

1. 1.00 moles2. 2.00 moles3. 5.00 moles4. 0.200 moles

At standard temperature and pressure, a hot-air balloon is filled with helium only to a volume of 4480 L. How many grams of helium are needed to fill the balloon?

1. 200. g2. 400. g3. 800. g4. 50.0 g

Correct Answer:

At STP

22.41 L = 4480 L1.00 mol n

n = 200. moles

Since MW(He) is 4.0 g/molMass = (200. g)(4.0 g/mol) = 800. g

1. 200. g2. 400. g3. 800. g4. 50.0 g

A gas sample occupies a volume of 4.00 L at 20°C. The temperature at which the gas would double itsvolume is

1. 10°C2. 40°C3. 288°C4. 313°C

Correct Answer:

constantT

V

The temperature scale is absolute, however;

Vinitial/ (Vfinal) = Tfinal/ (Tinitial) 2 = Tfinal/ 293 K

Tfinal = 586 K, or 313°C

1. 10°C2. 40°C3. 288°C4. 313°C

N2(g) + 3 H2(g) 2 NH3(g)

At STP, 16 L of N2 and 48 L of H2 are mixed. Assuming all the reactants are consumed, how many L of NH3 will be produced?

1. 8.0 L2. 16 L3. 24 L4. 32 L5. 64 L

Correct Answer:

According to Avogadro’s law, mole ratios in the chemical equation will be volume ratios under identical conditions. Because the reactants are in a stoichiometric 3:1 volume ratio, the product will have stoichiometric equivalence. Thus,

(16 L N2)(2 mol NH3/1 mol N2) = 32 L NH3

)(constant TP,nV

1. 8.0 L2. 16 L3. 24 L4. 32 L5. 64 L

A container holds a mixture of oxygen, neon, and helium gases whose partial pressures are 150 torr, 300 torr, and 450 torr, respectively. The mole fraction of neon is

1. 0.172. 0.333. 0.504. 0.67

totali PP i

Correct Answer:

Xi = Pi/Ptotal

Xi = (300 torr)/(150 + 300 + 450)

torr

Xi = 300 torr/900 torr = 0.33

totali PP i1. 0.172. 0.333. 0.504. 0.67

A sample of He gas initially at STP is compressed to a smaller volume at constant temperature. What effect does this have on the rms speed of the atoms?

1. Increases

2. Decreases

3. No effect

Correct Answer:

The rms speed is directly proportional to the square root of the temperature, which does not change in this example.

M

RTu

3

1. Increases

2. Decreases

3. No effect

An unknown gas effuses at half the rate of helium. This gas is likely to be which of the following?

1. H2

2. CH4

3. Ne4. O2

5. Ar

1

2

M

M

2

1

r

r

Correct Answer:

(r1/2)2 =M2/M1

M2= (r1/r2)2M1

M2= (2/1)2(4.0 g/mol) = 16.0 g/mol

Therefore it could be CH4

1. H2

2. CH4

3. Ne4. O2

5. Ar

Real gases deviate from ideal behavior at __________ and _________.

1. High temperature; low pressure

2. Low temperature; high pressure

3. High temperature; high pressure

4. Low temperature; low pressure

Correct Answer:

At low temperature and high pressure, intermolecular forces increase as the molecules get closer together.

1. High temperature; low pressure

2. Low temperature; high pressure

3. High temperature; high pressure

4. Low temperature; low pressure

chapter 12 gases. what is the pressure of the gas in the bulb? 1. p gas = p h 2. p gas = p atm 3. p...

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