Properties of Hydrocarbons Flashcards

All 7 cards in this deck

How does the boiling point of a hydrocarbon change as its molecules get larger?

The boiling point increases.

How do viscosity and flammability change as hydrocarbon molecules get larger?

Viscosity increases (flows less easily) and flammability decreases.

True or false? Hydrocarbons with larger molecules ignite more easily.

False. Flammability decreases as molecular size increases, so larger molecules are harder to ignite.

What two products are formed by the complete combustion of a hydrocarbon?

Carbon dioxide and water.

What happens to the carbon and hydrogen in a fuel during combustion?

They are oxidised, and energy is released.

What are the steps to balance an equation for the complete combustion of a hydrocarbon?

e.g. $\mathrm{CH_4 + O_2 \rightarrow}$

1. Products are $\mathrm{CO_2}$ and $\mathrm{H_2O}$: $\mathrm{CH_4 + O_2 \rightarrow CO_2 + H_2O}$
2. Balance C then H: $\mathrm{1\,CO_2}$ and $\mathrm{2\,H_2O}$
3. Balance O last using $\mathrm{O_2}$: $\mathrm{CH_4 + 2O_2 \rightarrow CO_2 + 2H_2O}$

Why is a fraction such as petrol useful as a fuel for a car engine?

Its molecules are small, so it has a low boiling point, low viscosity and is highly flammable.