Rate of reaction

Question 1

What is an endothermic and exothermic reaction?

Answer 1

Endothermic takes heat in from surroundings.
Exothermic releases heat energy.

Question 2

In a heating/cooling graph why does it plateau?

Answer 2

When going liquid to gas the temp stays constant as it boils. The particles are escaping from liquid to form a gas.

When going solid to liquid the temp is constant as it is still being heated but the added energy is making the particles break away from the fixed arrangement.

Question 3

What types of reactions are exothermic or endothermic?

Answer 3

Exothermic- Combustion, respiration and neutralisation.

Endothermic- Photosynthesis, thermal decomposition and sherbet.

Question 4

What energy do breaking and making bonds release?

Answer 4

Breaking bonds is endothermic as energy is needed to break bonds.

Making bonds is exothermic as energy is released when a bond is formed.

Question 5

Describe an energy level diagram.

Answer 5

• The Y axis is energy and the X axis is the progress of reaction.
• If it goes down it is exothermic and if it goes up it is endothermic.
• The line is labelled reactant then the line that goes down or up has a △H and an arrow to show direction and the the last line is labelled product.
• Activation energy is the energy needed to break the bond.

Question 6

What can speed up the rate of reaction?

Answer 6

Temperature- Higher temperature the faster the rate of reaction as particles have more energy.
Concentration- More reactants the more frequent collisions.
Catalyst- Lower activation energy and produce the same amount of product faster while not getting used up.
SA:V- If a solid splits into multiple pieces there is more SA for the particles to react so there are more frequent collisions.

Question 7

What is the collision theory?

Answer 7

For a chemical reaction to happen the reactant particles need to collide with each other and they must have enough energy for them to react.

Question 8

What are the advantages and disadvantages of the different models?

Answer 8

Dot and Cross- Useful to illustrate transfer of electrons, shows how substances are formed but fails to show the 3D and doesn’t show relative size.

Ball and stick-