Question

Ka for a weak acid is 5 × 10–7 and its concentration is 0.2 M, the pH of the solution will be​

Answer 1

Answer:

Ph=4.1945

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Answer 2

Given :

Ka for weak acid = 5 × 10–7 

Concentration, C = 0.2 M

To find :

pH of the solution

Calculation :

• pH ( For weak acid ) is given by formula

$1/2 \times [ \: log_{10} Ka ) - log_{10}C) ]$

• Substituting values of Ka and C in above formula

pH = 1/2× [ log(5 × 10^-7) - log(2×10^-1) ]

pH = 1/2× [ log5 + log10^-7 - log2 - log10^-1 ]

= 1/2× [ log5 - 7 - log2 + 1 ]

= 1/2× [ log5 - log2 - 6 ]

• We know that, log5 = 0.698 and log2 = 0.301

pH = 1/2× [ 0.698 - 0.301 - 7 ]

pH = −3.3015