Calculating Energy changes in Reactions

Select the correct statement.

• Energy is needed to make bonds only.

• Energy is needed to break bonds only.

• Energy is needed to make and break bonds.

• Energy is not needed to make or break bonds.

Select the correct statement.

• Energy is needed to break bonds in reactants.

• Energy is needed to break bonds in products.

• Energy is needed to make bonds in reactants.

• Energy is not needed to make or break bonds.

Select the correct statement.

• Energy is needed to make bonds in reactants.

• Energy is needed to make bonds in products.

• Energy is needed to make bonds in reactants and in products.

• Energy is not needed to make or break bonds.

Write down the type of reaction where the energy needed to make bonds is higher than the energy needed to break bonds.

Write down the type of reaction where the energy needed to break bonds is higher than the energy needed to make bonds.

Select the word which means the amount of energy needed to break a specific bond between two atoms.

• A mouse

• A mole

• A rabbit

• A rat

1. Hydrogen and chlorine react together to make hydrochloric acid

2. H−H + Cl−Cl → 2 × (H−Cl)

3. The bond energy between hydrogen atoms is 436KJ, the bond energy between chlorine atoms is 243KJ.

4. Calculate the total bond energy in the reactants.

1. Hydrogen and chlorine react together to make hydrochloric acid

2. H−H + Cl−Cl → 2 × (H−Cl)

3. The bond energy between hydrogen and chlorine atoms is 432KJ.

4. Calculate the total bond energy in the products of this reaction.

1. Hydrogen and chlorine react together to make hydrochloric acid

2. H−H + Cl−Cl → 2 × (H−Cl)

3. The bond energy in the reactants is 679KJ, the bond energy in the products is 864KJ.

4. Calculate the energy change in this reaction.

1. Hydrogen and chlorine react together to make hydrochloric acid

2. H−H + Cl−Cl → 2 × (H−Cl)

3. The energy change in this reaction is -185KJ.

4. Select the correct type of reaction this represents.

• Exothermic

• Endothermic

• Neutralisation

• Reduction