Question

Calculate the molecular mass of the following substances:

(a) Ethyne $\left(C_2{H}_2\right)$

(b) Sulphur molecule $\left(S_8\right)$

(c) Phosphorus molecule $\left(P_4\right)$

(d) Hydrochloric acid $\left(HCl\right)$

(e) Nitric acid $\left(HN{O}_3\right)$

Answer 1

(a) Ethyne $\left(C_2{H}_2\right)$
Molecular mass of ethyne $\left(C_2{H}_2\right)$ = 2 x 12 + 2 x 1 = 26 u

(b) Sulphur molecule $\left(S_8\right)$
Molecular mass of sulphur molecule $\left(S_8\right)$
= 8 x 32 = 256 u

(c) Phosphorus molecule $\left(P_4\right)$
Molecular mass of phosphorus molecule $\left(P_4\right)$ = 4 x 31 = 124 u

(d) Hydrochloric acid $\left(HCl\right)$
Molecular mass of hydrochloric acid, $\left(HCl\right)$ = 1 + 35.5 = 36.5 u

(e) Nitric acid $\left(HN{O}_3\right)$
Molecular mass of nitric acid $\left(HN{O}_3\right)$ = 1 + 14 + 3 x 16 = 63 u