Ethane burns in oxygen to form `CO_2` and `H_2O` according to the equation :
`2C_2H_6 + 7O_2 rarr 4CO_2 + 6H_2O`
If 1250 cc of oxygen is burnt with 300 cc of ethane. Calculate :
the volume of unused `O_2`.

Explanation

The equation involved is
`2C_2 H_6 + 7O_2 to 4CO_2 + 6H_2O`
`2 " volumes " " " 4 " volumes "`
This equation implies that under similar conditions
2 volumes of ethane (on burning completely), will give
4 volumes of `CO_2`. Since the conditions are similar in the
given problem, 2.5 L of ethane will form `2.5 xx 4/2 = 5.0L " of " CO_2 " at " 27^@C` and 1 atm pressure.