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How many grams of NaOH must be dissolved in
one litre of solution to give it a pH value of 11?

Option: 1

0.04


Option: 2

0.08


Option: 3

0.4


Option: 4

4


Answers (1)

best_answer

\\\mathrm{Given } \mathrm{\: pH} \text { of solution }=11\\\begin{array}{l}{\mathrm{\: \: pH}=-\log \left[\mathrm{H}^{+}\right]} \\ {\: \: 11=-\log \left[\mathrm{H}^{+}\right]} \\\ {\left[\mathrm{H}^{+}\right]=10^{-11} \mathrm{M}} \\ {\mathrm{\: \: Kw}=\left[\mathrm{H}^{+}\right]\left[\mathrm{OH}^{-}\right]=1 \times 10^{-14}} \\\\ {\left[\mathrm{OH}^{-}\right]=\frac{1 \times 10^{-14}}{10^{-11}}=1 \times 10^{-3} \mathrm{M}} \\ {\text { Strength }=\text { Molarity } \times \text { mol. weight }} \\ {=10^{-3} \times 40} \\ {=0.04 \mathrm{g} / \text { litre. }}\end{array}
Therefore, option(1) is correct

Posted by

Gautam harsolia

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