Question

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

Answer 1

1 litre contains 80% oxygen i.e. 800ml oxygen.
22.4 l oxygen contains Na molecules of O2
So, no. of molecules in.0.8 l oxygen will be 0.8Na/22.4 = 2.15*10^22 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.