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The ester, ethyl acetate is formed by the reaction between ethanol and acetic acid and equilibrium is represented as: `CH_(3)COOH_((l))+C_(2)H_(5)OH_((l))hArrCH_(3)COOC_(2)H_(5_((aq)))+H_(2)O_((l))` (`a`) Write the concentration ratio (reaction quotient), `Q_(e)`, for this reaction. Note that water is not in excess and is not a solvent in this reaction. (`b`) At `293 K`, if one starts with `1.00 "mole"` of acetic acid and `0.180` of ethanol, there is `0.171 "mole"` of ehtyl acetate in the final equilibrium mixture. Calculate the equilibrium constant. (`c`) Starting with `0.500 "mole"` of ethanol and `1.000 "mole"` of acetic acid and maintaining it at `293 K`, `0.214 "mole"` of ethyl acetate is found after some time. Has equilibrium been reached? |
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Answer» Correct Answer - (i) `[CH_(3)COOC_(2)H_(5)][H_(2)O]//[CH_(2)COOH][C_(2)H_(5)OH]` (ii) `3.92` , (iii) value of `Q_(c)` is less than `K_(c)` therefore equilibrium is not attained. (i) Reaction quotient, `Q_(c) = ([CH_(3)COOC_(2)H_(5)][H_(2)O])/([CH_(3)COOH][C_(2)H_(5)OH])` (ii) Let the volume of the reaction mixture be V. Also, here we will consider that water is a solvent and is present in excess. The given reaction is : `{:(,CH_(3)COOH_((l)),+,C_(2)H_(5)OH_((l)),harr,CH_(3)COOC_(2)H_(5(l)),,H_(2)O_((l))),("Initial conc.",1/(V)M,,(0.18)/(V)M,,0,,0),("At equilibrium",(1-0.171)/(V),,(0.18-0.171)/(V),,(0.171)/(V)M,,(0.171)/(V)M),(,=(0.829)/(V)M,,=(0.009)/(V) M,,,,):}` Therefore, equilibrium costant for the given reaction is : `K_(c) = ([CH_(3)COOC_(2)H_(5)][H_(2)O])/([CH_(3)COOH][C_(2)H_(5)OH])` `= ((0.171)/(V)xx (0.171)/(v))/((0.829)/(V) xx (0.009)/(V)) = 3.919` `= 3.92` (approximately) (iii)Let the volume of the reaction mixture be V. `{:(,CH_(3)COOH_((l)),+,C_(2)H_(5)OH_((l)),harr,CH_(3)COOC_(2)H_(5(l)),+,H_(2)O_((l))),("Initial conc.",(1.0)/(V)M,,(0.5)/(V)M,,0,,0),("After some time",(10-0.214)/(V),,(0.5-0.214)/(V),,(0.214)/(V)M,,(0.214)/(V)M),(,=(0.786)/(V)M,,=(0.286)/(V)M,,,,):}` Therefore, the reaction quotient is, `Q_(c) = ([CH_(3)COOC_(2)H_(5)][H_(2)O])/([CH_(3)COOH][C_(2)H_(5)OH])` `= ((0.214)/(V)xx (0.214)/(V))/((0.786)/(V) xx (0.286)/(V))` `= 0.2037` `= 0204` (approximately) Since `Q_(c) lt K_(c)` equilibrium has not been reached. |
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