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A weak base BOH is tirated against 0.1 M...

A weak base BOH is tirated against 0.1 M of HCl solution. The following table indicates the volumes of HCl added and pH of solution.

From this data the `pK_b` of base may be.

A

`4.74`

B

` 4.3`

C

` 4.9 `

D

` 4.5`

Text Solution

Verified by Experts

The correct Answer is:
A
`pOH =pK_b +log ""( S)/(B) `
` 14- 10.04 = pK_b +log ""( 0.1 xx 5 )/( 40 B -0.1 xx 5) `
` rArr 3.96 =pK_b +log ""( 0.5 )/( 40 B -0.5 ) ......(1) `
` 14- 9, 14 =pK_b +log"" ( 0.1 xx 20)/( 40 B -0.1 xx 20 ) `
` rArr 4.86 = pK_b +log ""( 2)/(40B - 2) ....(2) `
` 0.9 = log"" ( 2)/( 40 B-2) xx ( 40 B -0.5 )/( 0.5 ) `
` 8 = 4xx ( 40 B-0.5)/( 40 B -2) rArr 80 B -4 =40 B -0.5`
` 40 B =3.5 rArr B =(3.5)/(40) `
substituting in (1)
` 4.86 =pKb+ log"" (2)/(3.5-2 ) rArr pK_b =4.74`
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