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. 60 ml
C. 30 ml
D. 20 ml

Answer

C

Explanation

`CH_(4(g))+2O_(2(g))toCO_(2(g))+2H_2O_((i))`
To burn 20 ml of `CH_4`, 40 ml of `O_2` is needed. So 50 - 40 = 10 ml `O_2` is left and corresponding to 20 ml of `CH_4`, 20 ml of `CO_2` is formed and `H_2O` is liquid on cooling. So `(20+10) = 30 ml of gases are left.