A solution calorimeter has a heat capacity of 94.82 J/K. It contains 100.0 mL of

Question

A solution calorimeter has a heat capacity of 94.82 J/K. It contains 100.0 mL of a solution that is 3.0 M in H2SO4 and 0.02500 M in Fe2+. This solution has a heat capacity density of 0.232 J K-1 mL-1. 0.07900g of powdered KMnO4 (FW = 158.034 g/mol) was introduced into the calortimeter giving a resulting Temperature change of + 2.44K. The reaction taking place is:

KMnO4 (s) + 5 Fe 2+ (aq) + 8 H+ (aq) ---> Mn2+ (aq) + 5 Fe 3+ (aq) + K (aq) + 4 H2O (l)

Determing the standard enthalpy of reaction for this reaction.

Explanation / Answer

DE = - Z*DT*(mol.wt/wt of sub.)

       = - 94.82*(2.44)*(158.034/0.079)

       = -462821.173 J

DH = DE+PDV = DE+nRT

no.of moles change = 0 (because no reactent and product in the gaseous state)

DH = -462821.173 J or -462.821 Kj

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