Combined Chemistry - 5.5

Question 1

Name the following reactions that:

a) Take in heat from the surroundings
b) Give out heat to the surroundings

Answer 1

a) Endothermic
b) Exothermic

Question 2

Name the type of reaction used in self-heating cups and hand warmers.

Answer 2

Exothermic reaction

Question 3

Give an example of a chemical reaction that is exothermic.

Answer 3

Examples include: Combustion, Oxidation, Neutralisation

Question 4

How do you know the reaction profile below is for an exothermic reaction?

Answer 4

Energy of products is lower than the energy of reactants

Question 5

What can be said about the amount of energy before a chemical reaction and the amount of energy after a chemical reaction?

Answer 5

They are equal

Question 6

Give an example of a chemical reaction that is endothermic.

Answer 6

Examples include: Thermal Decomposition and Reacting Citric Acid with Sodium hydrogencarbonate

Question 7

Name the type of reaction is used in sports injury packs.

Answer 7

Endothermic reaction

Question 8

How do you know the reaction profile below is for an endothermic reaction?

Answer 8

Energy of products is higher than the energy of reactants

Question 9

Draw an energy level diagram (reaction profile) for an exothermic reaction.

Answer 9

Question 10

What is the name for the minimum amount of energy needed for a reaction to happen?

Answer 10

Activation energy

Question 11

Calculate the overall energy change in this reaction.

Bond energies: NN = 941 kJ/mol ; N-H = 391 kJ/mol ; H-H = 436 kJ/mol

*this is just an example, you may have to do this for any reaction. You will be given the bond energies.

Answer 11

Reactants: (6 x 391) = 2346

Products: (1 x 941) + (3 x 436) = 2249

2346 – 2249 = + 97 kJ/mol

Question 12

Draw an energy level diagram (reaction profile) for an endothermic reaction.

Answer 12

Question 13

Look at the reaction profiles below. Which arrows show the activation energy and which arrows show the overall energy change?

Answer 13