redox [P1] PAPER 1

Question 1

define the term oxidising agent

Answer 1

species that gains electrons (from the species that’s being oxidised, so is reduced)

Question 2

define the term reducing agent

Answer 2

species that loses electrons (to the species that’s being reduced, so is oxidised)

Question 3

oxidation state of an element?

Answer 3

0

Question 4

oxidation state of a neutral compound (i.e. it has no charge)?

Answer 4

0

Question 5

oxidation state of compound with a charge?

Answer 5

the individual oxidation states of each element in the compound add up to the charge of the overall compound

Question 6

oxidation state of hydrogen?

Answer 6

+1
unless bonded to a metal - in that case, it’s -1

Question 7

oxidation state of all halogens?

Answer 7

-1

Question 8

oxidation state of oxygen?

Answer 8

-2

Question 9

oxidation state of group 1 elements?

Answer 9

+1

Question 10

A student carried out an experiment to find the mass of FeSO4.7H2O in an impure sample, X, making it up to a solution and carrying out a titration with potassium dichromate to determine figures for calculations.

The student found that the calculated mass of FeSO4.7H2O was greater than the actual mass of the sample that had been weighed out. The student realised that this could be due to the nature of the impurity.

Suggest one property of an impurity that would cause the calculated mass of FeSO4.7H2O in X to be greater than the actual mass of X.

Explain your answer.

Answer 10

• Impurity reacts with dichromate
• Such that, for a given mass, the impurity would react with more dichromate than a similar mass of FeSO4.7H2O