(a) Define 'formula unit' of an ionic compound. What is the formula unit of (i) sodium chloride, and (ii) magnesium chloride ?
(b) Calculate the formula masses of the following compounds :
(i) Calcium chloride , (ii) Sodium carbonate
(Given : Atomic masses : `Ca = 40 u , Cl = 35.5 u , Na = 23 u , C = 12 u , O = 16 u`)

Answer

(a) (i) NaCl (or `Na^(+)Cl^(-)`) , (ii) `MgCl_(2)` (or `Mg^(2+)2Cl^(-)`) , (b) (i) 111 u , (ii)`106 u`