Question

Each of the two flasks contain 2.0 g of gas at the same temperature and pressure. One flask contains oxygen and the other hydrogen.

1. Which sample contains the greater number of molecules?
2. If the hydrogen sample contains N molecules, how many molecules are present in oxygen sample?

Answer 1

i. 16 g of oxygen gas has = 6.023 × 10²³ molecules

2 g of oxygen gas will have = `(6.023 xx 10^23)/(16 xx 2)`

= 0.75 × 10²³

1 g of hydrogen has = 6.023 × 10²³ molecules

2 g of hydrogen gas will have = `(6.023 xx 10^23 xx 2/1)`

= 12.05 × 10²³

So, hydrogen gas has a greater number of molecules.

ii. Amount of hydrogen and oxygen gases is the same = 2 g

So, for oxygen, 32 g of gas has = N molecules

Then, 2 g of gas has = `N/32 xx 2`

= 16

∴ No. of molecules of oxygen is `N/16`.