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Consider the following statements I.The pH |
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Answer» I and II After reaction20 mmol020 mmol40 mmol Total volume =400+400=800mmol Number of moles of `H_92)SO_(4)=20mmol` Number of moles of `H^(+)` ion =`2xx20m` mol=40m mol` [H^(+)]=40/800=0.05` `pH=-log[H^(+)]=-log(0.05)=2-log(5)=2-0.7=1.3` pH=1.3 II.`K_(w)=[H^(+)][OH^(-)]` As T increases, `K_(w)` also increases III.pH=5 and `K_(a)=10^(-5)` `implies-log[H^(+)]=5` Weak monobasic acid ‘HA’ having concentration ‘C’ `HA(aq) to H^(+)(aq) + A^(-1)(aq)` At t=0C00 At equilibirium`C-CalphaCalphaCalpha` `K_(a)=([H^(+)][A^(-1)])/([HA])=(CALPHA)/(C(1-alpha))` `alpha to `degree of dissociation `therefore K_(a)=(Calpha^(2))/(1-alpha)=10^(-5) ` … (1) (given) `[H^+)]=Calpha=10^(-5)`… (2) From EQUATION (1) & (2) `alpha/(1-alpha)=1impliesalpha=1-alpha implies alpha=1/2` `% alpha=1/2 xx100=50%` IV. It is applicable |
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