Question

# A) A gas mixture with a total pressure of 760 mmHgcontains each of the following gases...

A)

A gas mixture with a total pressure of 760 mmHgcontains each of the following gases at the indicated partial pressures: 124 mmHg CO2, 216 mmHg Ar, and 177 mmHg O2. The mixture also contains helium gas.

What is the partial pressure of the helium gas?

B) A sample of gas has a mass of 0.560 g . Its volume is 116 mL at a temperature of 87 ∘C and a pressure of 769 mmHg .

Find the molar mass of the gas.

A)

total pressure = sum of individual pressure

760 mmHg = p(CO2) + p(Ar) + p (O2) + p(He)

760 mmHg = 124 mmHg + 216 mmHg + 177 mmHg + p(He)

p(He) = 243 mmHg

B)

Given:

P = 769.0 mm Hg

= (769.0/760) atm

= 1.0118 atm

V = 116.0 mL

= (116.0/1000) L

= 0.116 L

T = 87.0 oC

= (87.0+273) K

= 360 K

find number of moles using:

P * V = n*R*T

1.0118 atm * 0.116 L = n * 0.0821 atm.L/mol.K * 360 K

n = 3.971*10^-3 mol

mass(solute)= 0.560 g

use:

number of mol = mass / molar mass

0.004 mol = (0.560 g)/molar mass

molar mass = 141 g/mol

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