Question

If one gram of sulphur contains x atoms, calculate the number of atoms in one gram of oxygen element.

(Atomic masses : S = 32 u ; O = 16 u)

Answer 1

Given:

1g  sulphur contains x atoms
We know that equal moles of all substances contain equal number of molecules (1 mole of all substances contains 6.022 × 10²³ molecules).

Therefore, the ratio of molecules in sulphur and oxygen will be the same as their ratio of moles.
Therefore, 1g of S = 1/32 moles of S
Now, 1/32 moles of S contain x molecules (given). Since equal number of molecules are present in equal moles of all substances, 1/32 moles of oxygen will also contain x number of molecules.

Number of moles in 1g of oxygen:

1 mole of O = 16g

16g  O = 1 mole of O

Therefore, 1g  O₂ = 1/16 moles of O₂

We have already stated that 1/32 moles of oxygen contain x molecules; therefore,1/16 mole of oxygen will contain = x × 32 / 16 = 2x molecules Hence, 1 gram  oxygen consists of 2x the number of sulphur molecules.