Question

The molecular weight of a compound is 329 g/mol and contains 1 mole of Na per mole of molecules. If the compound contains 12.8% nitrogen and 9.8% sulphur how many nitrogen and sulphur atoms are present per atom of sodium :

• A. 2 and 1
• B. 1 and 3
• C. 1 and 2
• D. 3 and 1

Answer 1

The correct option is D 3 and 1

The molecular weight of the compound is 329 g/mol and contains 1 mole of Na.
The compound contains 12.8% nitrogen and 9.8% sulphur.

Thus, 329 g of the compound contains $\frac{12.8}{100}\times 329=42g$ nitrogen and $\frac{9.8}{100}\times 329=32.2g$ sulphur.

The atomic masses of N and S are 14 g/mol and 32 g/mol.

Thus, 329 g of the compound contains $\frac{42}{14}=3mol$ nitrogen and $\frac{32.2}{32}=1mol$ sulphur.

Thus, 3 nitrogen and 1 sulphur atoms are present per atom of sodium.