Neutralization of 18.5 g of saturated monobasic acid required a solution containing 10 g of sodium hydroxide.

Neutralization of 18.5 g of saturated monobasic acid required a solution containing 10 g of sodium hydroxide. Determine the molecular formula of the acid

Given:
m (CnH2nO2) = 18.5 g
m (NaOH) = 10 g

To find:
CnH2nO2 -?

1) CnH2nO2 + NaOH => CnH2n-1O2Na + H2O;
2) n (NaOH) = m / M = 10/40 = 0.25 mol;
3) n (CnH2nO2) = n (NaOH) = 0.25 mol;
4) M (CnH2nO2) = m / n = 18.5 / 0.25 = 74 g / mol;
5) M (CnH2nО2) = Mr (CnH2nО2) = Ar (C) * N (C) + Ar (H) * N (H) + Ar (O) * N (O) = 12 * n + 1 * 2n + 16 * 2 = (14n + 32) g / mol;
74 = 14n + 32;
n = 3;
6) C3H6O2.

Answer: Unknown substance – C3H6O2.