(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)

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Solution

(a). The simplest combination of ions that produces an electrically neutral unit, is called ‘formula unit’ of the ionic compound.
Formula unit of sodium chloride – NaCl
Formula unit of magnesium chloride – MgCl2
(b).
(i). Formula Mass of Calcium chloride (CaCl2) = 1xCa + 2xCl = (40+71) u = 111 u
(ii). Formula Mass of Sodium carbonate (Na2CO3) = 2xNa + 1xC + 3xO= (2×23 + 1×12 + 3×16) u = 106 u

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Similar questions

Q. (a) Define 'formula unit' of an ionic compound. What is the formula unit of (i) sodium chloride, and (ii) magnesium chloride ?
(b) Calculate he 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)

Calculate the formula masses of the following compounds:
(i) Sodium oxide, $N a_{2} O$
(ii) Aluminium oxide, $A l_{2} O_{3}$
(Given: Atomic masses : Na = 23 u; O = 16 u; Al = 27 u)

Q. Write the formulae of the following compounds, showing the steps involved.

(a) sodium oxide
(b) magnesium nitrate
(c) magnesium sulphate
(d) aluminium chloride

Q. A unit cell of sodium chloride has four formula units. The edge length of the unit cell is

0.564

nm. What is the density of sodium chloride?

[N a = 23, C l = 35.5]

Calculate Formula Unit mass for Zinc Oxide, Sodium Oxide, Sodium Chloride, Magnesium Carbonate, Copper Sulphate, Sodium Carbonate, Ammonium Hydroxide.

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