JEE Main & Advanced Chemistry Thermodynamics / रासायनिक उष्मागतिकी Sample Paper Topic Test - Thermo Chemistry (Thermodynamics)

The enthalpies of formation of \[A{{l}_{2}}{{O}_{3}}\] and \[C{{r}_{2}}{{O}_{3}}\] 1596 kJ and - 1134 kJ respectively. \[\Delta H\] for the reaction \[2Al+C{{r}_{2}}{{O}_{3}}\to 2Cr+A{{l}_{2}}{{O}_{3}}\]

A) - 2730 kJ

B) - 462 kJ

C) - 1365 kJ

D) + 2730 kJ

Correct Answer: B

Solution :

[b] \[2Al+\frac{3}{2}{{O}_{2}}\to A{{l}_{2}}{{O}_{3}},\Delta H=-1596\text{ }kJ\]	...(i)
\[2Cr+\frac{3}{2}{{O}_{2}}\to C{{r}_{2}}{{O}_{3}},\Delta H=-1134\text{ }kJ\]	...(ii)
By (i) - (ii)
\[2Al+C{{r}_{2}}{{O}_{3}}\to 2Cr+A{{l}_{2}}{{O}_{3}},\Delta H=-462kJ.\]