1The Diagram Shows Two Molecules of a Hydrocarbon Called Ethane and a Molecule of Oxygen

1The diagram shows two molecules of a hydrocarbon called ethane and a molecule of oxygen.

aWhat are the products formed when ethane burns in excess air? Carbon dioxide and water

bWrite a word equation for the combustion of ethane. Ethane + oxygen  Carbon dioxide + water

cWrite an equation showing the formulae of the reactants and products (this does not have to be balanced). C2H6 + O2  CO2 + H2O

dHow many carbon atoms are there altogether in the two ethane molecules? 4

eHow many carbon dioxide molecules will be formed from the two ethane molecules? 4

fCopy the diagram and draw the correct number of carbon dioxide molecules in one of the empty boxes.

gHow many hydrogen atoms are there altogether in the two ethane molecules? 12

hHow many water molecules will these make? 6

(Hint: remember there are two hydrogen atoms in every water molecule.)

iDraw the water molecules in the remaining empty box.

jCount up the number of oxygen atoms in all the carbon dioxide and water molecules you have drawn. Draw more oxygen molecules in the second box until you have the right number. Remember, you must have oxygen molecules, not atoms.

kBalance the formula equation by writing the correct numbers in front of the formulae you wrote in part c. 2C2H6 + 7O2  4CO2 + 6H2O

2The drawing shows a molecule of propane.
Write a balanced equation for the combustion of propane.

C3H8 + 5O2  3CO2 + 4H2O

3Write balanced equations for hydrocarbons with the following formulae by asking yourself the same questions about the numbers of molecules. Draw pictures of the molecules if it helps you to work out the answer. For some of these you may need to start with two molecules of the hydrocarbon.

This document may have been altered from the original.

aC4H10

bC5H12

cC6H14

This document may have been altered from the original.

2C4H10 + 13O2  8CO2 + 10H2O

C5H12 + 8O2  5CO2 + 6H2O

2C6H14 + 19O2  12CO2 + 14H2O

Extra challenge

4The drawing shows a molecule of an alcohol called methanol.

aIs methanol a hydrocarbon? Explain your answer. No because it contains oxygen as well as hydrogen and carbon.

bAlcohols also produce carbon dioxide and water when they burn completely in excess oxygen. Write a balanced equation for the combustion of methanol.

2CH3OH + 3O2  2CO2 + 4H2O

This document may have been altered from the original.