20 mL of methane is completely burnt using 50 mL of oxygen. The volume of the gas left after cooling to room temperature is

Options

A. 80 mL
B. 40 mL
C. 60 mL
D. 30 mL

Answer

D

Explanation

`underset("1 mL")(CH_(4))+underset("2 mL")(2O_(2))rarr underset("1 mL")(CO_(2))+2H_(2)O(l)`
1 mL of `CH_(4)` reacts with 2 mL of `O_(2)` and produces
1 mL of `CO_(2)`
`therefore " 20 mL of "CH_(4)" will react with 40 mL "O_(2) and " produce 20 mL of "CO_(2)`
`therefore O_(2)" left = 10 mL and "CO_(2)` produced = 20 mL
`therefore" Total voluem of gas after cooling"= 10+20`
=30 mL