1.

The K_(a)value for HCN is 10^(-9) . What is the pH of 0.5 M HCN solution ?

Answer»

SOLUTION :`K_(a)=10^(-9)`
c=0.4 M`
pH=-log[H^+]`
`[H^+]=sqrt(k_axxc)`
`=sqrt(10^(-9)xx0.4)`
`=2XX10^(-5)`
`THEREFORE pH=-log(2xx10^(-5))`
`=5-log2`
`=5-0.3010`
`=4.699`.


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