Q. 4 moles each of $SO_{2}\ and\ O_{2}$ gases are allowed to react to form $SO_{3}$ in a closed vessel. At equilibrium 25% of $O_{2}$ is used up. The total number of moles of all the gases at equilibrium is
A) 6.5
B) 7.0
C) 8.0
D) 2.0
Explanation
(a)
$2SO_{2}\ \ \ \ + \ \ \ O_{2}\ \ \ \ \ \rightleftharpoons \ \ \ 2SO_{3}$
Initially 4 4 0
At equili. 4(1-0.25) 4(1-0.25) $0.25 \times 2$
Total number of moles at equilibrium
$4(1 - 0.25)\ \ \ \ \ \ \ \ \ \ 4(1 - 0.25)\ \ \ \ 0.5$
$4 - 1\ \ \ \ \ \ 4 - 1\ \ \ \ \ 0.5\ \ \ \ 6.5$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.