Question

1. what is the molar mass of air, assuming it is 78% nitrogen, 21% oxygen, and 1% argon by volume. (avogadros law: the volumes of gases at the same pressure and temperature contain the same number of moles)

Explanation:

Step1: Find molar mass of each component

Molar mass of \(N_2\) is \(2\times14 = 28\space g/mol\), molar mass of \(O_2\) is \(2\times16=32\space g/mol\), molar mass of \(Ar\) is \(40\space g/mol\).

Step2: Calculate weighted - average molar mass

Using the formula \(M=\sum_{i}x_iM_i\) (where \(x_i\) is the mole fraction and \(M_i\) is the molar mass of component \(i\)).
Since by Avogadro's Law, volume fraction = mole fraction.
\(M=(0.78\times28)+(0.21\times32)+(0.01\times40)\)
\(M = 21.84+6.72 + 0.4\)

Answer:

\(29\space g/mol\)