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Question

Chemistry Question on Acids and Bases

The concentration of hydronium ions in a cup of black coffee is 1.3×10−5M1.3 \times 10^{-5} M. What will be the pHpH of the coffee?

A

4.89

B

3.89

C

2.2

D

None of these

Answer

4.89

Explanation

Solution

Given, [H3O+]=1.3×10−5\left[H_{3} O^{+}\right]=1.3 \times 10^{-5} ∵pH=−log⁡[H3O+]\because p H=-\log \left[H_{3} O^{+}\right] =−log⁡(1.3×10−5)=-\log \left(1.3 \times 10^{-5}\right) =−(log⁡1.3+log⁡10−5)=-\left(\log 1.3+\log 10^{-5}\right) =−0.1139+5=-0.1139+5 ∴pH=4.886≈4.89\therefore p H=4.886 \approx 4.89