Question

20 mL of methane is completely burnt using 50 mL of oxygen. The volume of the gas left after cooling to room temperature is? A) 80 B)40 C) 60 D) 30

Answer 1

Answer:

D) 30 mL

Explanation:

The reaction can be written as

CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(l)

Here H₂O is liquid, rest are gases.

From reaction it is clear that 1 mole of Methane reacts with 2 moles of Oxygen

Since the reaction involves gases under the same temperature and pressure, the mole ratios can be treated as volume ratios.

Thus 20 mL of Methane will react with 40 mL of Oxygen

Therefore, here methane is a limiting reagent

So, 20 mL of Methane (CH₄) will react with 40 mL of Oxygen (O₂) to produce 20 mL of CO₂

Therefore after the reaction is complete, there will be 10 mL of O₂ and 20 mL of CO₂ left.

Thus total volume of gas left = 10 + 20 = 30 mL