Question

In a compound, Na, S, H and O are presen The percentage of Na, S and H are 14.28% 9.92%, 6.20% respectively. Determine th molecular formula of compound. If a H-atoms are present in H₂O form  compound then give its crystallized formula when its molar mass is 322 g.

Answer 1

% of O = 100 - (% of Na + % of S + % of H) 

= 100 - (14.28 + 9.92 + 6.20) = 100 - 30.40 = 69.60 

So, empirical formula of compound = Na₂H₂OO₁₄ 

Empirical formula mass = 23 × 2 + 32 + 20 + 14 × 16 

46 + 32 + 20 + 224 

= 322 g 

Molar mass of compound = 322 g

\(n = \frac{\text{Molar} \ \text{mass}}{\text{Empirical}\ \text{formula}\ \text{mass}}\) 

\( = \frac{322}{322} = 1\)

Molecular formula of compound is Na₂SH₂OO₁₄. The formula of crystallized compound will be Na₂SO₄10H₂O.