E.Q's

Question 1

Describe the energy change when an excess of water is added to anhydrous copper sulfate

[2 marks]

Answer 1

Energy is transferred from the anhydrous copper sulfate to the surroundings and heat is given off

The reaction is exothermic

Question 2

What is the ionic equation for neutralising?

[1 mark]

Answer 2

H+ + OH– → H2O

Question 3

Explain how adding a catalyst increases the rate of reaction

[2 marks]

Answer 3

Catalysts provide an alternative reaction pathway

With a lower activation energy

This means that less energy is required to produce the same yield

Question 4

What effect does adding a catalyst have on the equilibrium of a reaction?

Answer 4

No effect

Question 5

What is an exothermic reaction

[1 mark]

Answer 5

A reaction where energy is released

Question 6

A reaction is as follows:
C2H4(g) + H2O(g) ⇌ C2H5OH(g

The forward reaction is exothermic

Explain how the conditions for this reaction should be chosen to produce ethanol as
economically as possible.

Answer 6

Add a catalyst. A catalyst would provide an alternative reaction pathway with a lower activation energy. This will reduce costs as less energy is required to produce the same yield.

Reducing the temperature will increase the yield. Reducing the temperature means that heat is being given off into the surroundings so the temperature of the system increases. The equilibrium will shift to the right to favour the forward, exothermic, reaction. This will increase the yield of ethanol and reduce costs as a lower temperature is required

think cheapest for INCREASING RATE and INCREASING YIELD

Question 8

During a reversible reaction, the temperature of the system increased.

Name the type of reaction that cause temperature to rise

Answer 8

Exothermic reaction

Question 9

Name a piece of equipment that could be used to measure the volume of acid in the turbidity practical

[1 mark]

Answer 9

Measuring cylinder

Question 10

In the turbidity practical when should the student stop the stop watch

Answer 10

When the cross drawn on paper can no longer be seen through the solution

Question 11

What are the dependant and independant variables in the turbidity practical?

[2 marks]

Answer 11

Dep: Time taken for cross to disappear

Ind: Temperature

Question 13

A student investigated how the concentration of hydrochloric acid affected the rate of reaction between hydrochloric acid and magnesium ribbon.

Give two variables which the student should control during the experiment

[2 marks]

Answer 13

1. Temperature
2. Length of magnesium strip

Question 14

State a change that can be made to a magnesium strip to increase the rate of a reaction

Answer 14

Cut it up into smaller pieces

Question 15

Reversible reactions can reach equilibrium in a closed system.

What is meant by a closed system?

Answer 15

The reaction occurs in a sealed reaction vessel where no reactant can be added and no product can escape

Question 16

Explain why a reaction seems finished when a reversible reaction reaches equilibrium.

Answer 16

The forward and reverse reaction are occuring at the same rate.

This means that there is no overall change in the reactant and product quantities

Question 17

How will a reaction profile display that a reaction is exothermic?

[1 mark]

Answer 17

The overall energy change is negative

Question 18

How will a reaction profile display that a reaction is endothermic

Answer 18

The overall energy change is positive

Question 19

State what is meant by activation energy

Answer 19

The minimum amount of energy required for a reaction to take place

Question 20

A reaction has an energy change of -45 kJ per mole

Give one difference and one similarity in the energy change between the forward and reverse reaction

Answer 20

The same amount of energy is transferred

Forward reaction is exothermic and reverse reaction is endothermic