Question

In the reaction:

Ca(OH)2 (aq) + 2HCl (aq) —> CaCl2 (aq) + 2H2O (l)

a) What is the mole ratio of OH- to Ca^2+?

b) What is the experimental formula?

Answer 1

Ca(OH)₂ being a strong electrolyte ionizes as,

Ca(OH)₂ (aq) Ca²⁺ (aq) + 2 HO^- (aq)

This means on ionization of 1 molecule of ca(OH)2 there is formaation of 1Ca²⁺ (aq) and 2 HO^- (aq)

So Mole ratio of HO- to Ca²⁺ (aq) is 2 : 1.

b) In experiment there used a monoprotic acid HCl. The mole ratio of HCl to Ca(OH)2 is 2 : 1.

In this Acid base reaction there is formation of 2 H2O molecules this indicates presence of 2HO- ions.

Also there is formation of 1 CaCl2 molecule from 1 Ca(OH)2 molecules which indicates presence of 1 Ca2+.

Hence experimentaly also mole ratio of Ho^- to Ca²⁺ is 2 : 1.

And hence experimental formula is also Ca(OH)2.

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