2H2 + O2 → 2H2O: From this equation; calculate the volume of unreacted oxygen gas if a mixture of 50cm3 of hydrogen and 75cm3 of oxygen are involved

A. 85cm³
B. 50cm³
C. 125cm³
D. 55cm³

Correct Answer:

Option B – 50cm³

Explanation

Since 2 mol H₂ reacted with 1 mol of O₂
: 50cm³ of hydrogen reacted with 25cm³ of oxygen

Remainder oxygen = Supplied amount – Reacted amount → 75cm³ – 25cm³ = 50cm³