Question

A deep-sea diver uses a gas cylinder with a volume of 10.0 L and a content of 51.0 g of O2 and 33.5 g of He.

Calculate the partial pressure of each gas and the total pressure if the temperature of the gas is 16 ∘C.

Express the pressures in atmospheres to three significant digits separated by commas.

Answer 1

1) Calculate partial pressure of O2

Molar mass of O2 = 32 g/mol

mass(O2)= 51.0 g

use:

number of mol of O2,

n = mass of O2/molar mass of O2

=(51 g)/(32 g/mol)

= 1.594 mol

Given:

V = 10.0 L

n = 1.5938 mol

T = 16.0 oC

= (16.0+273) K

= 289 K

use:

P * V = n*R*T

P * 10 L = 1.5938 mol* 0.08206 atm.L/mol.K * 289 K

P = 3.7798 atm

2) Calculate partial pressure of He

Molar mass of He = 4.003 g/mol

mass(He)= 33.5 g

use:

number of mol of He,

n = mass of He/molar mass of He

=(33.5 g)/(4.003 g/mol)

= 8.369 mol

Given:

V = 10.0 L

n = 8.3687 mol

T = 16.0 oC

= (16.0+273) K

= 289 K

use:

P * V = n*R*T

P * 10 L = 8.3687 mol* 0.08206 atm.L/mol.K * 289 K

P = 19.8467 atm

3) Calculate total pressure

Ptotal = P(O2) + P(He)

= 3.78 atm + 19.8 atm

= 23.6 atm

3.78, 19.8, 23.6 atm