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Question: Approximate pH of 0.1 M aqueous H2S solution when K1 and K2 for H2S at 25oC are 1×10–7 and 1.3 × 10–...

Approximate pH of 0.1 M aqueous H2S solution when K1 and K2 for H2S at 25oC are 1×10–7 and 1.3 × 10–13 respectively :

A

4

B

5

C

6

D

8

Answer

4

Explanation

Solution

pH of 0.1 M H2S solution can be derived by :

H2S ⇌\rightleftharpoons H+ + HS– ; K1 = 1 ×10–7

1×10−7×0.1\sqrt { 1 \times 10 ^ { - 7 } \times 0.1 }

= 10−8\sqrt { 10 ^ { - 8 } } = 10–4

∴\therefore pH = 4