Consider the acid equilibrium for acetic acid (K_a = 1.76 times 10^-5 at 25 degr

Question

Consider the acid equilibrium for acetic acid (K_a = 1.76 times 10^-5 at 25 degree C). CH_3CO_2 (aq) + H_2O (l) doubleheadarrow CH_3CO_^-2(aq) + H_3O^+ (Aq) (HOAc) (OAc^-) The reaction is exothermic as written. For the reaction, give a plus, minus or zero for the following changes. No explanation need be provided. Delta U_tot delta U_ theta delta H_ sigma delta U_wt delta _r S degree delta S_ theta delta S_tot delta _rG degree ________ ____________ ____________ ______________ __________ ___________ ___________ __________ (Extra space provided for your convenience.)

Explanation / Answer

Note that

dH = dU + dPV

dPV = 0, since liquid and aquoeus solution have constant P and V, therefore

dH = negative, so dU total = negative

dUsurroundings = positive, since heat is released by sytem

dHsigma = negative, since exothermic

dUwt = 0, no work is performed

dSrxn = the entropy must increase in the system since more aqueous solution is produced

dSsurorundings = must increase, since entropy dpends on heat, and this is exothermic

dStotal = this is favoured slightly, acutally, the HOAc is much more favoured, so entropy of universe is negative

dGrxn = positive, since this does not favors the products

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