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How many moles of `Ca(OH)_(2)` must be dissolved to produce 250 mL of an aqueous solution of pH `10.65`, assuming completer dissociation ? |
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Answer» Let a mole of `Ca(OH)_(2)` be dissolved in 250 mL. solution to have `pH= 10.65` `[Ca(OH)_(2)]=(axx1000)/(250)=4a M` `{:(("Complete ionization"), Ca(OH)_(2)rarr,Ca^(2+)+,2OH^(-)),("Intial moles", 4a,0,0),("Final moleas", 0,4a, 2xx4aM):}` `:. [OH^(-)]= 8aM` `[H^(+)]=(10^(-14))/(8a)` `.: pH= -llog[H^(+)]` `:. 10.65= -log(10^(-14))/(8a)` `(10^(-14))/(8a)=2.238xx10^(-11)` `:. a=5.85xx10^(-5)`mole |
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