spm-redox questions

Essential Chemistry SPM Question Bank

Chapter 12: Oxidation and Reduction

Paper 1

1) What is the oxidation number of the sulphur element in a sulphate ion, SO 2-?
4

A -2 C +6

B -6 D -8

2)
Cl2 + 2KI → I2 + 2KCl

The oxidation number of chlorine in the reaction above changes from

A O to -1 C 1 to -1

B -1 to O D -2 to O

3) Which of the following can act as an oxidising agent?

I Chlorine gas

II Bromine water

III Sulphur dioxide gas

IV Tin(II) chloride solution

A I and II only C I, II and III only

B III and IV only D II, III and IV only

4) Which of the following reactions is not a redox reaction?

A Displacement C Electrolysis

B Precipitation D Rusting

5) When a certain type of gas is channelled into an iron (II) sulphate solution, it will change

the green colour of the solution into brown. The gas is most likely

A hydrogen chloride C chlorine

B hydrogen sulphide D ammonia

6) When an ion is discharged at the anode during electrolysis, it experiences

A ionisation C oxidation

B precipitation D reduction

7) What is the energy change that occurs in the cell shown in the diagram below?

A Chemical energy into kinetic energy
B Electrical energy into heat energy
C Electrical energy into chemical energy
D Chemical energy into electrical energy
8) Which of the following equations occurs at the anode?

A Fe →Fe2+ + 2e-
B O2 + 2H2O + 4e- → 4OH-
C 4OH- → O2 + 2H2O + 4e-
D Fe2+ + 2e- → Fe
9) The figure below shows the extraction process of tin in a blast furnace.

What is substance Y? C Platinum
A Iron D Magnesium
B Carbon

10) The figure below shows an experiment that is carried out to study the corrosion of iron.

The iron nail will become corroded at the slowest rate if the metal container is made of

A magnesium C aluminium

B copper D tin

Paper 2
Structured question

PQ

The figure above shows an apparatus set-up that is used to study the reaction that occurs in test
tubes P and Q.

(a) What can be observed in test tubes P and Q?
(b) Write the ionic equation for the reaction in (a).
(c) Some of the reaction products in test tube Q is mixed with 1,1,1-trichloroethane liquid

and then shaken.
(i) What is the colour of the 1,1,1-trichloroethane liquid layer that is formed?
(ii) Write an ion electron equation to represent the formation of the substance
that gives the 1,1,1-trichloroethane liquid layer its colour.

(d) State the function of the zinc in test tube P.
(e) Write the change in oxidation number of the bromine in test tube Q after (c) occurs.
(f) For the reaction that occurs in test tube P,

(i) state the type of reaction that occurs.
(ii) name one other substance that can replace the zinc piece.

Essay question
(a) You are given two compound formulae.

NaCl PbO2

(i) Based on the two formulae, state the oxidation number of sodium and lead.

[2 marks]

(ii) Name both the compounds according to the IUPAC naming system. [2 marks]

(iii) Explain the difference between the names of the two compounds according to the

IUPAC naming system. [2 marks]

(b) The figure below shows the set-up of apparatus that is used in an experiment to study

electron transfer at a distance.

(i) Name the reducing agent in this experiment. [1 mark]

(ii) Write the half-equation for the reaction that occurs at the negative terminal and the

positive terminal. [5 marks]

(iii) Based on the answer in (b)(ii), describe the oxidation and reduction processes in

terms of the electron transfer that occurs at the negative terminal and the positive

terminal as well as state the observation that can be made at the end of the

experiment. [8 marks]

Paper 3
The figure below shows an experiment that is carried out to determine the order of metals in the
reactivity series of metals, by using the carbon element.

Mixtures of the following substances are heated strongly in the crucible.

Lead(II) oxide and carbon
Zink oxide and carbon
Copper(II) oxide and carbon

The results of the experiment are recorded in the table below.

Experiment Observation on the mixture of substances
Bright embers

(a) Observe each diagram in the table above. Complete the observation on the mixture of

substances by stating the observation made on the reaction that occurs. [Observe]

(b) Complete the table below based on the observations.

(i) Variable that is manipulated: (i) Way that variable is manipulated:

(ii) Variable that responds: (ii) Observation of the responding variable:

(iii) Variable that is kept constant: (iii) Way to maintain the variable that is kept
constant:

[Method of controlling the variable]

(c) State the hypothesis of this experiment. [Making the hypothesis]

(d) Based on the observation made in this experiment, arrange the lead, zinc, and copper metals
according to a descending order in the reactivity of the metals.

Decreasing reactivity of metal

(e) The experiment is repeated using a number of different oxides and the observations made in
the experiment are shown in the table below.

Mixture of substance Observation on the mixture
Aluminium oxide and carbon No change
Iron(II) oxide and carbon Embers
Magnesium oxide and carbon No change
Tin(II) oxide and carbon Embers

Based on the observations in the table above, classify the metals into two groups, namely the

group of metals that are more reactive than carbon and the group of metals that are less reactive

than carbon. [Classify]