The standard enthalpy of formation of FeO & Fe 2 O 3 is − 65 kCal mol − 1 and − 197 kCal mol − 1 respectively. A mixture of two oxides contains FeO & Fe 2 O 3 in the mole ratio 2 : 1. If by ox

Question

The standard enthalpy of formation of FeO & Fe 2 ​ O 3 ​ is − 65 kCal mol − 1 and − 197 kCal mol − 1 respectively. A mixture of two oxides contains FeO & Fe 2 ​ O 3 ​ in the mole ratio 2 : 1. If by oxidation, it is changed into a 1 : 2 mole ratio mixture, how much of thermal energy (in Kcal) will be released per mole of the initial mixture ?

TestHub · Accepted Answer

Initial mixture ratio FeO : Fe₂O₃ = 2 : 1

Take 3 mol initial mixture:

$2 F e O + F e_{2} O_{3}$

Final ratio = 1 : 2, total Fe atoms conserved:

$F e O + 2 F e_{2} O_{3}$

Reaction:

$F e O + \frac{1}{4} O_{2} \to \frac{1}{2} F e_{2} O_{3}$

Energy released:

$Δ H = \frac{( - 197 ) - 2 ( - 65 )}{2} = - 33.5 k c a l$

For 3 mol initial mixture, FeO converted = 1 mol, so heat released:

$= \frac{33.5}{2.5} = 13.4 k c a l m o l^{- 1}$

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