Question.
Calculate the molar mass of the following substances
(a) Ethyne, $\mathrm{C}_{2} \mathrm{H}_{2}$
(b) Sulphur molecule, $S_{8}$
(c) Phosphorus molecule, $\mathrm{P}_{4}$ (atomic mass of phosphorus $=31$ )
(d) Hydrochloric acid, $\mathrm{HCl}$
(e) Nitric acid, $\mathrm{HNO}_{3}$
Calculate the molar mass of the following substances
(a) Ethyne, $\mathrm{C}_{2} \mathrm{H}_{2}$
(b) Sulphur molecule, $S_{8}$
(c) Phosphorus molecule, $\mathrm{P}_{4}$ (atomic mass of phosphorus $=31$ )
(d) Hydrochloric acid, $\mathrm{HCl}$
(e) Nitric acid, $\mathrm{HNO}_{3}$
Solution:
(a) Molar mass of ethyne, $\mathrm{C}_{2} \mathrm{H}_{2}=2 \times 12+2 \times 1=26 \mathrm{~g}$
(b) Molar mass of sulphur molecule,
$\mathrm{S}_{\mathrm{g}}=8 \times 32=256 \mathrm{~g}$
(c) Molar mass of phosphorus molecule,
$P_{4}=4 \times 31=124 \mathrm{~g}$
(d) Molar mass of hydrochloric acid,
$\mathrm{HCl}=1+35.5=36.5 \mathrm{~g}$
(e) Molar mass of nitric acid.
$\mathrm{HNO}_{3}=1+14+3 \times 16=63 \mathrm{~g}$
(a) Molar mass of ethyne, $\mathrm{C}_{2} \mathrm{H}_{2}=2 \times 12+2 \times 1=26 \mathrm{~g}$
(b) Molar mass of sulphur molecule,
$\mathrm{S}_{\mathrm{g}}=8 \times 32=256 \mathrm{~g}$
(c) Molar mass of phosphorus molecule,
$P_{4}=4 \times 31=124 \mathrm{~g}$
(d) Molar mass of hydrochloric acid,
$\mathrm{HCl}=1+35.5=36.5 \mathrm{~g}$
(e) Molar mass of nitric acid.
$\mathrm{HNO}_{3}=1+14+3 \times 16=63 \mathrm{~g}$
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