Explain giving reasons why:
(i) Ionic solids conduct electricity in molten state, but not in solid state.
(ii) Solution of sodium chloride has no effect on litmus, but a solution of zinc chloride turns blue litmus red.

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Solution

(i) To conduct electricity ions of a substance should be free to move to oppositely charged electrodes. In solid state of a substance(ionic compound) ions are not free to move but in molten(liquid) state they are free to move.
(ii) Sodium chloride is salt of strong acid and a strong base so it does not undergo hydrolysis when dissolved in water and solution remains neutral. Zinc chloride is a salt of strong acid and weak base so its $Z n^{2 +}$ ions combine with $O H^{-}$ ions of water(cationic hydrolysis) forming less dissociated $Z n (O H)_{2}$ . Concentration of $H^{+}$ ions increases and solution becomes acidic and turns blue litmus red.
$N a C l + H_{2} O ⇌ N a^{+} + C l^{-} + H^{+} + O H^{-}$
$Z n C l_{2} + 2 H_{2} O ⇌ Z n (O H)_{2} + 2 H^{+} + 2 C l^{-}$ .

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Q. A solution of potassium chloride has no effect on litmus whereas, a solution of zinc chloride turns the blue litmus red. Give a reason.

Hydrogen chloride solution in water turns blue litmus red, and conducts electricity, while in toluene does not. Explain why.

Explain why :

(a) anhydrous HCl is a poor conductor while aqueous HCl is an excellent conductor.
(b) when the stopper of a bottle full of hydrogen chloride gas is opened there are fumes in the air.
(c) a solution of hydrogen chloride in water turns blue litmus red and conducts electricity, while a solution of the same gas in toluene :
(i) has no effect on litmus, and
(ii) does not conduct electricity.
(d) thick white fumes are formed when a glass rod dipped in $N H_{4} O H$ is brought near the mouth of a bottle full of HCl gas.
(e) dry hydrogen chloride gas does not affect a dry strip of blue litmus paper but it turns red in the presence of a drop of water.

(f) hydrogen chloride gas is not collected over water.

Explain, why (or give reasons for)
(i) In the laboratory preparation of hydrogen chloride from sodium chloride, the gas can be obtained below 200°C or above. But the lower temperature is preferred.
(ii) Hydrogen chloride is not collected over water.
(iii) Hydrochloric acid cannot be concentrated above 22.2% by boiling.
(iv) HCl gas does not conduct electricity, but hydrochloric acid conducts electricity.
(v) Only a very dilute solution of hydrogen chloride in water can be concentrated by boiling the solution while a very concentrated solution would become less concentrated when boiled.
(vi) When the stopper of a bottle full of HCl gas is opened there are fumes in the air.
(vii) A solution of HCl gas in water turns blue litmus red and conducts electricity, while HCl gas dissolves in toluene and it has no effect on litmus and does not conduct electricity.
(viii) An aqueous solution of chlorine is acidic in nature.

Q. Explain why solid sodium chloride does not conduct electricity but in the molten state it does?

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Explain giving reasons why:(i) Ionic solids conduct electricity in molten state, but not in solid state.(ii) Solution of sodium chloride has no effect on litmus, but a solution of zinc chloride turns blue litmus red.

Explain giving reasons why:
(i) Ionic solids conduct electricity in molten state, but not in solid state.
(ii) Solution of sodium chloride has no effect on litmus, but a solution of zinc chloride turns blue litmus red.