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The equilibrium equations and K(a) value...

The equilibrium equations and `K_(a)` values for three acids are given at `25^(@)C:`
`HA(aq)" "+" "H_(2)OhArrH_(3)O^(+)(aq)" "+" "A^(-)(aq),K_(a)=2xx10^(-5)`
`HB(aq)" "+" "H_(2)OhArrH_(3)O^(+)(aq)" "+" "B^(-)(aq),K_(a)=4xx10^(-6)`
`HC(aq)" "+" "H_(2)OhArrH_(3)O^(+)(aq)" "+" "C^(-)(aq),K_(a)=1xx10^(-4)`
The pH of 0.2 M aqueous HA solution is

A

`3.70`

B

`2.70`

C

`1.70`

D

`2.35`

Text Solution

Verified by Experts

The correct Answer is:
B
`H^(+)=sqrt(K_(a)xxC)=sqrt(2xx10^(-5)xx0.2)`
`[H^(+)]=2xx10^(-3)`
`pH=2.7`
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