Q.

The pH of aqueous solution of NH4CN (Kaof HCN is 9.2×1010 & Kb of NH4OH is 1.8 ×105)

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a

7

b

< 7

c

14

d

> 7

answer is A.

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Detailed Solution

 HCN is a weak acid & NH4OH is a weak base. While NH4CN is a salt of weak acid & weak base.

Therefore, pH = 7 +12(pKa- pKb)

= 7 + 12 [(-logKa) - (-logKb)]

= 7 + 12[9.04 - 4.74]

= 7 + 2.15 = 9.15

Hence, the correct option is option (A) > 7.

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