Consider the following statements: (a) The pH of a mixture containing 400 mL of 0.1 MH_(2)SO_(4) and 400 mL of 0.1 M NaOH will be approximately 1.3. (b) Ionic product of water is termperature dependent. ( c) A monobasic acid with K_(a) = 10^(-5) has a pH =5. The degree of dissociation of this acid is 50% (d) The Le Chatelier's principle is not applicable to common-ion effect.

Consider the following statements: (a) The pH of a mixture containing

1.	Consider the following statements: (a) The pH of a mixture containing 400 mL of 0.1 MH_(2)SO_(4) and 400 mL of 0.1 M NaOH will be approximately 1.3. (b) Ionic product of water is termperature dependent. ( c) A monobasic acid with K_(a) = 10^(-5) has a pH =5. The degree of dissociation of this acid is 50% (d) The Le Chatelier's principle is not applicable to common-ion effect.
Answer» a and b a,b and c b and c a,b and d Solution :`underset("40 m mol excess")(H_(2)SO_(4)) + underset("40 m mol limiting reagent")(2NaOH) to Na_(2)SO_(4) + 2H_(2)O` After reaction `"20 m mol020 m mol40 m mol"` Total VOLUME = 400+400 = 800 mmol Number of moles of `H_(2)SO_(4)=20` m mol Number of moles of `H^(+)` ion = `2 xx 20` m mol = 40 m mol `[H^(+)] = 40/800 = 0.05` M `pH=-logH^(+)] =-log(0.05) =2-log 5=2-0.7 = 1.3` pH=1.3 (B) `K_(omega) = [H^(+)][OH^(-)]` As T increases, `K_(omega)` also increases (c ) pH=5 and `K_(4)=10^(-5)` `rArr -log[H^(+)]=5` `[H^(+)]=10^(-5)` Weak monobasic acid 'HA' having concentration 'C' `{:(,HA(aq), H^(+)(aq)+,A^(-1)(aq)),("At t=0",C,0,0),("At equilibrium",C-Calpha,Calpha,Calpha):}` `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)=1 rArr alpha=1-alpha` `alpha = 1/2` `% alpha = 1/2 xx 100 = 50%`