Question

n
14. If dry air is consider to have only nitrogen
and oxygen and it is found to have average
molecular mass 28.84. What is the
composition of dry air?
(A) N2 – 79%; O2 -21%
(B) N2-84%; 02-16%
a
(C) N2-81%; 02-19%
(D) N2 -90%; 02-10%​

Answer 1

Explanation:

the process is given in the above attachment...hope it helps u..

Answer 2

Answer:

The composition of dry air is 79% of nitrogen and 21% of oxygen.

Explanation:

Given dry air have only nitrogen and oxygen

Average molecular mass 28.84

Let the percentage of nitrogen in dry air is $x$.

And hence the percentage of oxygen  is $100-x$.

Average molecular mass is given by the average of individual molecular mass and their percentages in the molecule, i.e.,

$\frac{(x~molecular~ mass)( x\%)+(y~molecular ~mass)( y\%)}{100}$

Hence, average molecular mass of dry air is

$\frac{(N_2~ mol.~ mass )(N_2\%)+(O_2~mol. ~mass)(O_2\%)}{100}$

$\implies 28.84=\frac{(28)(x)+(32)(100-x)}{100}$

$\implies 2884=28x+3200-32x$

$\implies 4x=316\implies x=\frac{316}{4} =79$

Therefore the percentage of nitrogen is 79%.

And percentage of  oxygen is $100 - 79 = 21\%$

Hence, the composition of dry air is 79% of nitrogen and 21% of oxygen.