Paper 5

Question 1

Suggest a suitable apparatus to be used when making a large concentration of propanone solution.

Answer 1

a volumetric lask in ranges 25- 250 cm3 volume

Question 2

When a reaction involving some reactants and a catalyst is to be carried out, in what order should they be added?

Answer 2

The catalyst should be added first

and then the reactants should be added last as adding this would cause the reaction to start.

Question 3

What is a suitable apparatus to transfer 10 cms from a conical flask?

Answer 3

A 10 cm3 pipette.

Question 4

Suggest a suitable indicator to be used when the concentration of Iodine in a solution is to be identified.

What will the colour change observed on this indicator be?

Answer 4

A starch indicator will be used.

The iodine on the starch will go from blue-black to colourless.

Question 5

How could a graph be used to prove that a reaction is in the first order?

Answer 5

• > Find the half-life: if the half-life is constant throughout the graph, then the reaction is first order.
• > Half-life determined from the graph should be constant.
• > Determine the gradient at different points to find the rate. plotting this graph should give a linear plot that goes through the origin of the graph.

Question 6

Why might there be a large difference in the calculated enthalpy change per mole and the acceptable enthalpy change per mole?

Answer 6

The heat loss will account for the large discrepancy.