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The progress of the reaction given below, CH_(3)COOC_(2)H_(5)+H_(2)Ooverset(H^(+))(to)CH_(3)COOH+C_(2)H_(5)OH can be followed by measuring the concentration of acid (HCl acid used as catalyst plus acetic acid formed during the reaction) by means of alkali titration. Find the volume of alkali (NaOH) needed for the end point that will increase with time. |
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Answer» Solution :`{:(,CH_(3)COOC_(2)H_(5),+,H_(2)O,overset(H^(+))(to),CH_(3)COOH,+,C_(2)H_(5)OH),("At t=0",a,,"excess",,0,,0),("At t=t",a-x,,"constant",,x,,x),("At t=oo",0,,,,a,,a):}` If `V_(0)`, `V_(t)` and `V_(oo)` are the volumes of `NaOH` solution needed for the end point of titration of the reaction mixture at zero time, time `t` and at infinity, i.e. after completion of the reaction-the CONDITION being achieved by HEATING the reaction mixture for some time, then `V_(0) prop ["acid catalyst"]` `V_(t) prop ["acid catalyst"]+x` `V_(oo) prop ["acid catalyst"]+a` `:.V_(00)-V_(t) prop a-x` `V_(prop)-V_(0) prop a` (since concentration of `HCl` acid acting as catalyst will remain constant). The above reaction which is of first order (actually pseudo unimolecular) will, therefore obey following equation. `k=(2.303)/(t)log.(V_(oo)-V_(0))/(V_(oo)-V_(t))` |
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