Chem - Introduction to organic chemistry

bonkysleuth SG

A very easy question here. Which one of the following hydrocarbons would you expect to find in petroleum gas?

a.C3H8

b.C7H14

c.C16H34

d.C20H12

My guess is either a or b. Both look like possible answers.

And also from these 4 fuels

coal, hydrogen, natural gas, petrol

which is the fuel that is ALMOST pollution free?

(Hydrogen is eliminated because it already is in the category under absolutely pollution free, which is in another question)

and also, what are 3 fuels that do not leave any ash after combustion?

I wrote coal, hydrogen and petrol. Natural gas will produce soot under incomplete combustion, so it is eliminated. Am I right?

Thanks.

dkcx SG

1) A. B is not a gas, its a liquid i think.

2) If H2 really cannot be the answer then u are left with natural gas.

3) Coal is the 1 that leads ash behind.

Natural gas is CH4

CH4 + 2O2 -> CO2 + 2H2O

Eyelessz SG

1) Answer should be A.

Roughly organic compounds with 1 - 4 Carbons are gaseous and 5 - 8? (i forgot) are liquids and above that are all solids. This is due to the increasing Mr of the molecules which results in a more extensive van der waal's forces of attraction. Hence a higher melting/boiling point