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JAMB Chemistry 2015 Paper

Question : 54

Total: 64

what is the pH of 0.00lmoldm³ solution of sodium hydroxide

Solution:

Concept:

Sodium hydroxide is a strong base, so its pH is calculated using

\mathrm{pOH}

and the relationship

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

Explanation:

For

0.001\ \mathrm{mol\,dm^{-3}}

\mathrm{NaOH}

, complete ionization gives

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

Calculate

\mathrm{pOH}

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

Use the water equilibrium relation:

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

\mathrm{pH} = 14 - 3 = 11

Answer:

D. 11

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