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Given Delta(i)H^(Theta)(HCN) = 45.2 kJ m...

Given `Delta_(i)H^(Theta)(HCN) = 45.2 kJ mol^(-1)` and `Delta_(i)H^(Theta)(CH_(3)COOH) = 2.1 kJ mol^(-1)`. Which one of the following facts is true?

A

`pK_(a)(HCN) =pK_(a)(CH_(3)COOH)`

B

`pK_(a)(HCN) gtpK_(a)(CH_(3)COOH)`

C

`pK_(a)(HCN) ltpK_(a)(CH_(3)COOH)`

D

`pK_(a)(HCN) =((45.50)/(2.1))pK_(a)(CH_(3)COOH)`

Text Solution

Verified by Experts

The correct Answer is:
B
`HCN` has greater heat of ionization, and is a weak acid. Thus it has high `pK_(a)` value.
Remember : Smaller the `pK_(a)` value, stronger the acid.
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