JEE Main 2017 · 8 Apr · Shift 1 · Chemistry Q38

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Addition of sodium hydroxide solution to a weak acid (HA) results in a buffer of pH 6. If ionisation constant of HA is $10^{-5}$ , the ratio of salt to acid concentration in the buffer solution will be :

4 : 5

1 : 10

10 : 1

5 : 4

Answer and worked solution

Official answer: C

$\text{pH}=pK_a+\log\dfrac{[\text{salt}]}{[\text{acid}]}$ : $6=5+\log\dfrac{[\text{salt}]}{[\text{acid}]}$ , so the ratio is 10 : 1.

Topics:Buffer solutions

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JEE Main 2017 · 8 Apr · Shift 1, Chemistry question 38