Question

Calculate the molar mass of the following substances

(a) Ethyne $C_2{H}_2$

(b) Sulphur molecule $S_8$

(c) Phophorous molecule $P_4$

(d) Nitric acid $HN{O}_3$

(e) Hydrochloride acid $HCl$.

Answer 1

(a) Molar mass of $C_2{H}_2=(2\times \text{atomic mass of C})+(2\times \text{atomic mass of H}$)

$=2\times 12+2\times 1=26u$

(b) Molar mass of $S_8=(8\times \text{atomic mass of S}$)

$=8\times 32=256u$

(c) Molar mass of $P_4=(4\times \text{atomic mass of P}$)

$=4\times 31=124u$

(d) Molar mass of $HCl=\left(\text{atomic mass of H}\right)+(\text{atomic mass of Cl}$)

$=1+35.5=36.5u$

(e) Molar mass of $HN{O}_3=\left(\text{atomic mass of H}\right)+\left(\text{atomic mass of N}\right)+(3\times \text{atomic mass of O}$)

$=1+14+3\times 16=63u$