In an oil refinery, heavy fractions of petroleum are heated to a high temperature in the absence of…

In an oil refinery, heavy fractions of petroleum are heated to a high temperature in the absence of air. Large alkane molecules break into smaller ones, and the smaller molecules are worth more as fuel and as a raw material for plastics. A laboratory model of this process uses $1.70\ \text{kg}$ of dodecane, $\text{C}_{12}\text{H}_{26}$, which is cracked completely into heptane, $\text{C}_{7}\text{H}_{16}$, and one other hydrocarbon X, in the mole ratio $1 : 1$. No other product forms, and the two products are separated by distillation, since their boiling points are far apart. The molar masses are $170.3\ \text{g/mol}$ for dodecane, $100.2\ \text{g/mol}$ for heptane and $70.13\ \text{g/mol}$ for X.

1. Find the number of hydrogen atoms in X.

1. X decolourises bromine water. How many open-chain structural isomers of X are possible? Ignore cis-trans isomers.

1. Find the mass of heptane and the mass of X that form, in grams. Check that the two masses add up to the mass of dodecane, and say why they must.