When hydrochloric acid is added to cobalt nitrate solution at room temperature, the following reaction takes place and the reaction mixture becomes blue. On cooling the mixture it becomes pink. On the basis of this information mark the correct answer.

$[C o (H_{2} O)_{6}]^{3^{+}} (a q)      p i n k + 4 C l^{-} (a q) ⇋ [C_{o} C l_{4}]^{2^{-}} (a q)      b l u e + 6 H_{2} O (l)$

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Solution

The correct option is A
On cooling the reaction is moving in backward direction.Thus backward reaction is exothermic.
Hence forward reaction is endothermic~i.e. $△ H > o .$

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Similar questions

[C o (H_{2} O)_{6}]^{3 +} (a q) + 4 C l)^{-} (a q) ⇌ [C o C l_{4}]^{2 -} (a q) + 6 H_{2} O (l)

{[C o (H_{2} O)_{5}]}_{2}^{3 +} (p i n k) (a q) + 4 C l^{-} (a q) ⇌ [C o C l_{4}]^{2 -} (b l u e) (a q) + 6 H_{2} O (l)

[C o (H_{2} O)_{6}]_{(a q)}^{3 +} + 4 C l_{(a q)}^{-} ⇌ [C o C l_{4}]_{(a q)}^{2 -} + 6 H_{2} O_{(l)}

C O (H_{2} O)_{6}^{2 +} (a q) + 4 C l^{⊝} (a q) ⇌ C o C l_{4}^{2 -} (a q) + 6 H_{2} O (l)

(Δ_{f} G^{0} (H)_{(a q)}^{+} = 0)

H_{2} O (l) ⟶ H^{+} (a q) + O H^{-} (a q); Δ H = 57.32 k J

H_{2} (g) + \frac{1}{2} O_{2} (g) ⟶ H_{2} O (l); Δ H = - 286.20 k J

O H^{-}

25^{o} C

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