At 1000 K, Delta G_f deg values are: Al2O3 -1582 kJ mol^-1 and Cr2O3 -1058 kJ mol^-1. For the thermite reaction Cr2O3 + 2Al -> Al2O3 + 2Cr carried out on 38.0 g of Cr2O3 (Cr = 52, O = 16), the Gibbs energy change at 1000 K is

JEE Advanced levelSingle correct optionDifficulty 3 of 3mt212

At 1000 K, $Δ G_{f}^{\circ}$ values are: $Al X_{2} O X_{3}$ $- 1582 kJ mo l^{- 1}$ and $Cr X_{2} O X_{3}$ $- 1058 kJ mo l^{- 1}$ . For the thermite reaction $Cr X_{2} O X_{3} + 2 Al Al X_{2} O X_{3} + 2 Cr$ carried out on 38.0 g of $Cr X_{2} O X_{3}$ (Cr = 52, O = 16), the Gibbs energy change at 1000 K is

Δ G^{\circ}

per mole of

Cr X_{2} O X_{3}

- 1582 - (- 1058) = - 524

kJ (elements have zero

Δ G_{f}

). n(

Cr X_{2} O X_{3}

) = 38.0/152 = 0.25 mol. Total = -524 x 0.25 = -131 kJ.