Consider the isomers of hydrocarbon with molecular formula $C_5H_{10}$. These isomers do not decolourise $KMnO_4$ solution. These isomers are subjected to chlorination with chlorine in presence of light to give monochloro compounds. The total number of monochloro compounds (structural isomers only) formed is ________.

One mole of an alkane (x) requires 8 mole oxygen for complete combustion. Sum of number of carbon and hydrogen atoms in the alkane (x) is ________.

Consider the following reaction of benzene.

In compound $(Q)$, the percentage of oxygen is $\_\_\_\_$ %. (Nearest integer)

The cycloalkene $(\mathrm{X})$ on bromination consumes one mole of bromine per mole of $(\mathrm{X})$ and gives the product $(\mathrm{Y})$ in which $\mathrm{C}: \mathrm{Br}$ ratio is 3:1. The percentage of bromine in the product $(\mathrm{Y})$ is $\_\_\_\_$ %. (Nearest integer)

(Given : molar mass in $\mathrm{g} \mathrm{mol}^{-1} \mathrm{H}: 1, \mathrm{C}: 12, \mathrm{O}: 16, \mathrm{Br}: 80$ )