An alkane $(Y)$ requires 8 moles of oxygen for complete combustion and on chlorination with $\mathrm{Cl}_2 / \mathrm{h} \nu,(\mathrm{Y})$ gives only one monochlorinated product $(\mathrm{Z})$. The total number of primary carbon atoms in $(Y)$ is $\_\_\_\_$ .

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)