Question

how many molecules of O2 are present in 1 litre air containing 80% volume of O2 at STP

Answer 1

1 litre of air contains 80% OO22 by volume. So OO22is 0.8 L.

At STP, 1 mole of OO22 occupies 22.4 L. Hence , we can find how many moles occupy 0.8 L by n=0.822.4=0.0357n=0.822.4=0.0357 .

1 mole contains avagadro number(6.023×10236.023×1023) of particles. So, 0.0357 moles contains 0.0357×6.023×1023=2.15×10230.0357×6.023×1023=2.15×1023 molecules

Answer 2

Answer:

Answer: 2.15x 10^22 molecules.

Explanation:

▪️ Correct question should be: how many molecules of oxygen are present in 1 litre of air containing 80% of O2.

First, we will have to find amount of energy in one oxygen.

Therefore,

➡️ Amount of oxygen present in 1 litre air is = 80% *1000 ml

➡️ (80/100)*1000

=800ml

▪️ We know that, 1 mole of STp occupies 22.4 litre

It is equal to = 22400ml of O2 gas contains 6.022x 10^23 molecules

So,

➡️ 1ml of O2 gas Contains =6.022x10^23/22400

According to question, we have to find 800ml molecules.

Therefore,

800ml contains =(6.022x 10^23/22400) *800

=> 2.15 x 10^22

▪️ Hence, molecules present in 1 litre air containing 80% volume of at STP is 2.15x 10^22 molecules.