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, SO42-?

A -2 C +6B -6 D -8

2) Cl2 + 2KI → I2 + 2KCl

The oxidation number of chlorine in the reaction above changes fromA O to -1 C 1 to -1B -1 to O D -2 to O

3) Which of the following can act as an oxidising agent?I Chlorine gas II Bromine waterIII Sulphur dioxide gas IV Tin(II) chloride solutionA I and II only C I, II and III onlyB III and IV only D II, III and IV only

4) Which of the following reactions is not a redox reaction?A Displacement C ElectrolysisB 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 likelyA hydrogen chloride C chlorineB hydrogen sulphide D ammonia

6) When an ion is discharged at the anode during electrolysis, it experiencesA 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 energyB Electrical energy into heat energyC Electrical energy into chemical energyD 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?A Iron C Platinum B Carbon D Magnesium

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 ofA magnesium C aluminiumB copper D tin

Paper 2Structured question

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.

P Q

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

(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]

NaCl PbO2

Paper 3The 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.

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

Experiment Observation on the mixture of substancesBright 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:___________________________________

Lead(II) oxide and carbonZink oxide and carbonCopper(II) oxide and carbon

[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.

(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 mixtureAluminium oxide and carbon No changeIron(II) oxide and carbon EmbersMagnesium oxide and carbon No changeTin(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]

Decreasing reactivity of metal

AnswersPaper 1

1 C2 A3 A4 B5 C6 C7 D8 A9 B10 A

Paper 2Structured question

1) (a) Test tube P: Blue coloured solution becomes colourless / Zinc piece dissolvesTest tube Q: Yellow coloured chlorine water is bleached / colourless solution changes to a brown colour

(b) Test tube P: Zn + Cu2+ → Zn2+ + Cu; Test tube Q: Cl2 + 2Br- → 2Cl- + Br2 (c) (i) Brown

(ii) 2Br-→ Br2 + 2e(d) As a reducing agent(e) From -1 to 0(f) (i) Redox reaction

(ii) Magnesium tape / aluminium piece

Essay question(a) (i) Na: +1; Pb: +4

(ii) Sodium chloride; Lead(IV) oxide(iii) - For the element in the compound that has only one oxidation number, the roman

numeral does not have to be written. - Sodium has only one oxidation number. Lead has more than one oxidation number.

(b) (i) Iodide ion/ potassium iodide(ii) Negative terminal: 2I-→ I2 + 2e

Positive terminal: Br2 + 2e- → 2Br- (iii) At the negative terminal:

- The iodide ion loses one electron- The iodide ion is oxidised into iodine- The green solution changes to brownAt the positive terminal:- The bromine gains electron- The bromine is reduced into bromide ion- The brown solution is decolourised

Paper 3(a) Dimly lit embers; Very bright embers(b) (i) Type of metal oxide; By changing the type of metal oxide

(ii) Embers; Brightness of embers(iii) Quantity of metal oxide; Use the same mass of metal oxide

(c) The more reactive a metal is, the brighter its embers (d) Carbon, lead, copper (e)

Metal that is more reactive than carbon

Metal that is less reactive than carbon

MagnesiumAluminium

IronTin