Q. $S(g)+\frac32O_2(g)\to SO_3(g)+2x\text{ kcal}$; $SO_2(g)+\frac12O_2(g)\to SO_3(g)+y\text{ kcal}$. The heat of formation of $SO_2(g)$ is given by :
A) $x+y$ kcal
B) $y-2x$ kcal
C) $\frac{2x}y$ kcal
D) $2x+y$ kcal
Explanation
[Solution by Dr. Abubacker] Subtract the second equation from the first: $S+O_2\to SO_2+(2x-y)$ kcal, i.e. $\Delta H=-(2x-y)=y-2x$ kcal. So the heat of formation of $SO_2$ is $y-2x$ kcal. Answer (2).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.