Question

Find the average molar mass of a mixture of 10 mol N2, 4 mol Ar and 7 mol He.

Group of answer choices a) 29.1 g/mol b)16.4 g/mol c)22.3 g/mol d)37.6 g/mol e)7.9 g/mol

Answer 1

Step 1:

Molar mass of N2 = 28.02 g/mol

use:

mass of N2,

m = number of mol * molar mass

= 10 mol * 28.02 g/mol

= 280.2 g

Step 2:

Molar mass of Ar = 39.95 g/mol

use:

mass of Ar,

m = number of mol * molar mass

= 4 mol * 39.95 g/mol

= 159.8 g

Step 3:

Molar mass of He = 4.003 g/mol

use:

mass of He,

m = number of mol * molar mass

= 7 mol * 4.003 g/mol

= 28.02 g

Step 4:

Total mass = 280.2 g + 159.8 g + 28.02 g

= 468.02 g

Total number of mol = 10 mol + 4 mol + 7 mol

= 21 mol

Average molar mass = total mass / total mol

= 468.02 g / 21 mol

= 22.3 g/mol

Answer: c