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JAMB Chemistry 2018 Paper

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Question : 5

Total: 87

What is the PH of 0.00 1 moldm

^3

solution of the sodium hydroxide

14
13
12
11

Solution:

Concept:

Sodium hydroxide is a strong base, so it fully dissociates. Determine

\mathrm{pOH}

first, then use

\mathrm{pH} + \mathrm{pOH} = 14

.

Explanation:

[\mathrm{NaOH}] = 0.001 \, \mathrm{mol\,dm^{-3}}

Since

\mathrm{NaOH} \to \mathrm{Na^+} + \mathrm{OH^-}

,

[\mathrm{OH^-}] = 0.001 = 10^{-3} \, \mathrm{mol\,dm^{-3}}

\mathrm{pOH} = -\log_{10}[\mathrm{OH^-}] = -\log_{10}(10^{-3}) = 3

\mathrm{pH} = 14 - \mathrm{pOH} = 14 - 3 = 11

Answer:

\mathrm{pH} = 11

, which is option D.

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