A 1.90 mol sample of N 2 gas is confined in a 45.9 liter container at 21.5 °C. I

Question

A 1.90 mol sample of N2 gas is confined in a 45.9 liter container at 21.5 °C.

If the amount of gas is decreased to 0.950 mol, holding the volume and temperature constant, the pressure will decreasebecause:

Choose all that apply.

With fewer molecules in the container, the molecules have lower average speeds.

With fewer molecules per unit volume, the molecules hit the walls of the container less often.

With lower average speeds, on average the molecules hit the walls of the container with less force.

As the average speed increases, the number of molecule-wall collisions decreases.

None of the Above

A 1.52 mol sample of Xe gas is confined in a 37.8 liter container at 29.7 °C.

If 1.52 mol of He gas is added holding the volume and temperature constant, the average molecular speed of the total system will

not enough information to answer the question

remain the same

decrease

increase

A mixture of methane and carbon dioxide gases, at a total pressure of 950 mm Hg, contains 3.04 grams of methane and5.24 grams of carbon dioxide. What is the partial pressure of each gas in the mixture?

PCH4 =  mm Hg
PCO2 =  mm Hg

A mixture of carbon dioxide and xenon gases contains carbon dioxide at a partial pressure of 428 mm Hg and xenon at a partial pressure of 560 mm Hg. What is the mole fraction of each gas in the mixture?

XCO2 =
XXe =

A mixture of methane and carbon dioxide gases, in a 6.92 L flask at 69 °C, contains 4.57 grams of methane and 7.87grams of carbon dioxide. The partial pressure of carbon dioxide in the flask is  atm and the total pressure in the flask is  atm.

A mixture of carbon dioxide and xenon gases is maintained in a 8.28 L flask at a pressure of 4.00 atm and a temperature of 65 °C. If the gas mixture contains 22.8 grams of carbon dioxide, the number of grams of xenon in the mixture is  g.

Explanation / Answer

1) A 1.90 mol sample of N2 gas is confined in a 45.9 liter container at 21.5 °C.
If the amount of gas is decreased to 0.950 mol, holding the volume and temperature constant, the pressure will decreasebecause:
Choose all that apply.

With fewer molecules in the container, the molecules have lower average speeds. FALSE --> Temperature is same

With fewer molecules per unit volume, the molecules hit the walls of the container less often. TRUE

With lower average speeds, on average the molecules hit the walls of the container with less force. FALSE --> average speed is the same due to temperature

As the average speed increases, the number of molecule-wall collisions decreases. FALSE

None of the Above FALSE

2) A 1.52 mol sample of Xe gas is confined in a 37.8 liter container at 29.7 °C.
If 1.52 mol of He gas is added holding the volume and temperature constant, the average molecular speed of the total system will

not enough information to answer the question FALSE

remain the same TRUE, speed is dependant of temperature. We are speaking of AVERAGE speed!

decrease FALSE

increase FALSE

3) A mixture of methane and carbon dioxide gases, at a total pressure of 950 mm Hg, contains 3.04 grams of methane and5.24 grams of carbon dioxide. What is the partial pressure of each gas in the mixture?

PCH4 =  mm Hg
PCO2 =  mm Hg

Convert to moles -->

MW CO2 = 44 g/gmol

MW CH4 = 16 g/gmol

Calculate moles with Moles = Mass/MW

Mol CO2 = 5.24/44 = 0.119

Mol CH4 = 3.04/16 = 0.19

Total mol = 0.119 + 0.19 = 0.309

Fractions --> mol i / total mol

X CO2 = 0.119/0.309 = 0.385

X CH4 = 0.19/0.309 = 0.615

Partial Pressure --> Pi = Xi*PT

P CO2 = X CO2 * 950 mm Hg = 0.385*950 = 366 mmHG

P CH4 = X CH4 * 950 mm Hg = 0.615*950 = 584 mm HG

4) A mixture of carbon dioxide and xenon gases contains carbon dioxide at a partial pressure of 428 mm Hg and xenon at a partial pressure of 560 mm Hg. What is the mole fraction of each gas in the mixture?

XCO2 =
XXe =

Total Pressure = Pi+Py = 428 + 560 = 988 mm HG

Fraction = Pi/PT

XCO2 = 428/988 = 0.433

XXe = 560/988 = 0.566

5) A mixture of methane and carbon dioxide gases, in a 6.92 L flask at 69 °C, contains 4.57 grams of methane and 7.87grams of carbon dioxide. The partial pressure of carbon dioxide in the flask is  atm and the total pressure in the flask is  atm.

PV = nRT

P = nRT/V = n*0.082*(69+273)/6.92 = 4.05*n

n = nCO2 + nCH4

MW CH4 = 16

MW CO2 = 44

Calculate amount of moles

mol CH4 = mass/MW = 4.57/16 = 0.286

mol CO2 = mass/MW = 7.87/44 = 0.178

Total Mol =0.286 + 0.178 = 0.464

RECALL

P = nRT/V = n*0.082*(69+273)/6.92 = 4.05*n

Calculate Partial pressure for each

P CH4 = 4.05*0.286 = 1.16 atm

P CO2 = 4.05*0.464 = 1.879 atm

6 ) A mixture of carbon dioxide and xenon gases is maintained in a 8.28 L flask at a pressure of 4.00 atm and a temperature of 65 °C. If the gas mixture contains 22.8 grams of carbon dioxide, the number of grams of xenon in the mixture is  g.

PV = nRT

CO2 + Xe

V = 8.28 L

P = 4 atm

T = 65 + 273 = 338 K

mass CO2 = 22.8 grams

MW CO2 = 44

Mol CO2 = 22.8/44 = 0.518 mol CO2

PV = nRT

n = PV/RT = 4*8.28/(0.082*338) = 1.195 mol (total mol)

since nt = nco2 + nxe

nt = 0.518 + nxe = 1.195

1.195-0.518 = 0.67 mol of Xenon

Sinc e MW Xe = 131.3 g/gmol

Mass Xe = Mol Xe * MW XE = 0.67*131.3 = 87.97 g of XE

Mass Xe = 87.97 g

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