Question

In place of iron(III) oxide in the thermite reaction in the previous problem, chromium(III) oxide can be used in its place, generating chromium metal and aluminum oxide as products. Calculate DrxnH and DrxnS for this thermite-type reaction. Assume standard conditions

Answer 1

Thermite reacti on: 2A1 (s) + Cr203(s) Stan dard enthalpy change of the reaction is Al203(s)2C s) maH (products)-naH° (reactants) 2x AH xAH AH 'f(A40,) 2xAHHAN)+ ) +1XAH0) (2 molx 0 kJ/mol) (2 mol x 0 kJ/mol) +(1 molx-1675.7 kJ/mol) +(1molx 134.7 kJmol) = -541 kJ Thermite reacti on: 2A1 (s) Cr2O3 (s) Standard entropy change of the reacti on is m (products)-nS (reactants) Al203(s)2C s) (2x()1x) (2x6)1 ) 2 molx 23.62 Jm ol. K) (1 mol x50.92 J/mol K) (2 mol x 28.33 J/mol K) +(1molx 81.17 J/m ol.K) = 39.67 kJK