Question

A student finds a container of gases in the laboratory classroom with a total pressure reading of 655 mmHg. The label on the container describes the contents as 5.00 g of carbon dioxide gas and 3.75 g of helium gas. Calculate the partial pressure of carbon dioxide in the container in mmHg.

Answer 1

Molar mass of CO2 = 1*MM(C) + 2*MM(O)

= 1*12.01 + 2*16.0

= 44.01 g/mol

Molar mass of He = 4.003 g/mol

n(CO2) = mass of CO2/molar mass of CO2

= 5.0/44.01

= 0.1136

n(He) = mass of He/molar mass of He

= 3.75/4.003

= 0.9368

n(CO2),n1 = 0.1136 mol

n(He),n2 = 0.9368 mol

Total number of mol = n1+n2

= 0.1136 + 0.9368

= 1.0504 mol

Partial pressure of each components are

p(CO2),p1 = (n1*Ptotal)/total mol

= (0.1136 * 655)/1.0504

= 71 mmHg

p(He),p2 = (n2*Ptotal)/total mol

= (0.9368 * 655)/1.0504

= 585 mmHg

for CO2 , p = 71 mmHg

for He , p = 585 mmHg