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Chemistry Question on Acids and Bases

The dissociation constant of a weak base is 1×10−5 {1 \times 10^{-5}} at 25?C. The pH of its 0.1 M solution at the same temperature.will be .

A

11

B

3

C

6

D

13

Answer

11

Explanation

Solution

By Ostwald dilution law ,
[OH−]{[OH^-]} in weak base= KbC\sqrt{K_bC}
??????????????? ??????????????????????? = 1×10−5×0.1\sqrt{1 \times 10^{-5} \times 0.1}
??????????????? ??????????????????????? = 1×10−3M1 \times 10^{-3} M
??????? pOH=−log[OH−]=−log(1×10−3) {pOH = -log[OH^-] = -log(1 \times 10^{-3}) }
??????? pOH=3⇒pH+pOH=14 {pOH = 3 \Rightarrow pH + pOH = 14 }
⇒  pH=14−3=11\Rightarrow \:\: { pH= 14 - 3 = 11}