Alkalenes

Question 1

Alkanes

Answer 1

Most compounds in crude oil are hydrocarbons (organic compounds made of carbon and hydrogen). Most of these molecules are alkanes.

Question 2

Alkane structure

Answer 2

In alkanes, carbon atoms bond to four other atoms (hydrogen or carbon).
We call them saturated hydrocarbons as they only contain single bonds with other atoms.

Question 3

Alkane uses

Answer 3

Alkanes are quite unreactive but can burn well.

This makes them useful fuels.

Question 4

General formula

Answer 4

The general formula for alkanes is CnH(2n+2).
E.g. if a hydrocarbon contained 7 carbon atoms, the number of hydrogen atoms would be (2 x 7) + 2 = 16.
Therefore, the formula for this hydrocarbon would be C7H16.

Question 5

What is the general formula for alkanes?

Answer 5

CnH(2n+2)

Question 6

The 4 smallest alkanes, in ascending size order, are:

Answer 6

Methane (CH4).
Ethane (C2H6).
Propane (C3H8).
Butane (C4H10).

Question 7

Meth
Eth
Prop
But
ane
ane
ane
ane

Answer 7

All alkanes end in ane.

Question 8

If an alkane contains 21 carbon atoms, what will its formula be?

Answer 8

To work this out, we must use the general formula for alkanes: CnH(2n+2).
Number of carbon atoms (n) = 21.
Number of hydrogen atoms = 2n + 2 = (2 x 21) + 2 = 44.
Formula: C21H44.

Question 9

The 4 smallest alkanes are (in ascending size order): Methane (CH4), Ethane (C2H6), Propane (C3H8), Butane (C4H10).