Question

Density of dry air containing only N2 and O2 is 1.15g/L at 740 mmhg and 300K. What is the percentage composition of N2 by weight in the air?

(Answer: 70.02%)

Explanation required !!!

Answer 1

Answer:

Given that there is only N2 and O2 in air,

So density = 1.15 g/l

Density of mixture is =  $\bold{\frac{x_{1} d_{1}+x_{2} d_{2}}{x_{1}+x_{2}}}$

Where, $x_{1}$ = percentage of gas 1

           $d_{1}$ = density of gas 1,

Similarly, $x_{2}, d_{2}$ percentage and density of gas 2 respectively.

We are given that,

$\begin{aligned} 1.15 &=\frac{x d_{N_{2}}+(100-x) d_{O_{2}}}{100} \\ 115 &=x d_{N_{2}}+(100-x) d_{O_{2}} \end{aligned}$

Now we have to take out dN2 and dO2 at 740 mm Hg pressure and 300K temperature. Therefore, we will use the formula,

PM = dRT;

d = PM/RT

Put R = 0.0821 and P = 740/760

Answer 2

Answer:

(Answer: 70.02%)

Density of dry air containing only N2 and O2 is 1.15g/L at 740 mmhg and 300K. What is the percentage composition of N2 by weight in the air? (Answer: 70.02%)