Name an alkali used in alkaline batteries.

  1. No.vi. Name an alkali used in alkaline batteries.

Answer. Potassium hydroxide is used in alkaline batteries.

  1. No. i. Why pure water is not a strong electrolyte?

Answer. Water is not a strong electrolyte because it ionizes very slightly into its ions.

H2O   H+ + OH

The concentration of ions is very small i.e.

[H+] = [OH] = 1.0 x 10-7M

  1. No. ii. HCl and H2SO4 are strong acids. While their solutions are equimolar, they have different pH value as calculated in problem 10.1 and 10.3. Why they have different pH values?

Answer. 0.01M HCl pH value is 2 while that of 0.01M H2SO4 pH value is 1.7. Although both of these acids completely ionize, but the concentration of H+ is double in case of sulphuric acid than that of hydrochloric acid. Such as

HCl (aq)    H+ (aq) + CI-

H2SO4 (aq)    2 H+ (aq) + SO2-4(aq)

pH of an acid depends upon H+ concentration. As sulphuric acid produces more H+ ions its pH Value is less than that of hydrochloric acid.

  1. No.iii .Why ionic-product constant of water is temperature dependent?

Answer. Ionic product constant (Kw) of water is product of equilibrium constant (Kc) and molar concentration of water [H2O]. Such as;

Kc [H2O] = [H+] [OH] Or  Kw = [H+] [OH]

As this equation shows ionic- product of water is product of H+ and OH- ions. More is

concentration of ions. More will be the ionic product. As we know ionization depends upon temperature it increases with increasing of temperature. Therefore, ionic product constant also increases with increasing of temperature and vice versa

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