Calculate the molar mass of the following substances.
$(a)$ Ethyne,$(C_2H_2)$
$(b)$ Sulphur molecule,$(S_8)$

Define the atomic mass unit.

In a reaction,$5.3 \, g$ of sodium carbonate reacted with $6 \, g$ of acetic acid. The products were $2.2 \, g$ of carbon dioxide,$0.9 \, g$ of water,and $8.2 \, g$ of sodium acetate. Show that these observations are in agreement with the law of conservation of mass.
$\text{Sodium carbonate} + \text{Acetic acid} \to \text{Sodium acetate} + \text{Carbon dioxide} + \text{Water}$

What is the mass of :
$(a)$ $0.2$ mole of oxygen atoms?
$(b)$ $0.5$ mole of water molecules?

Give the names of the elements present in the following compounds:
$(a)$ Quick lime
$(b)$ Hydrogen bromide
$(c)$ Baking powder
$(d)$ Potassium sulphate

Calculate the molar mass of the following substances.
$(a)$ Phosphorus molecule,$P_4$ (Atomic mass of phosphorus $= 31$)
$(b)$ Hydrochloric acid,$HCl$
$(c)$ Nitric acid,$HNO_3$