Download oxidation and reduction

QUESTIONSHEETS
CHEMISTRY
AS Level
OXIDATION AND REDUCTION
AS TOPIC 8
Questionsheet
1
OXIDATION NUMBERS I
27 marks
Questionsheet
2
OXIDATION NUMBERS II
18 marks
Questionsheet
3
INTRODUCTION TO REDOX
17 marks
Questionsheet
4
OXIDISING AGENTS AND REDUCING AGENTS
22 marks
Questionsheet
5
IONIC HALF-EQUATIONS AND THEIR COMBINATION
14 marks
Questionsheet
6
METALS WITH ACIDS
18 marks
Questionsheet
7
RELATIONSHIP BETWEEN CHANGE IN OXIDATION NUMBER
AND REACTION STOICHIOMETRY
15 marks
Questionsheet
8
DISPROPORTIONATION
17 marks
Questionsheet
9
EXTRACTION OF ALUMINIM
18 marks
Questionsheet
10
EXTRACTION OF METALS BY REDUCTION OF OXIDE
OR CHLORIDE
15 marks
Questionsheet
11
BLAST FURNACE
17 marks
Questionsheet
12
TEST QUESTION I
16 marks
Questionsheet
13
TEST QUESTION II
14 marks
Authors
Trevor Birt
Donald E Caddy
Andrew Jones
Adrian Bond
Editors
John Brockington
Stuart Barker
Curriculum Press – Licence Agreement:
John Brockington
Kevin Frobisher
Andy Shepherd
CP ress
Paper copies of the A-Level Chemistry Questionsheets
may be copied free of charge by teaching staff or students
for use within their school, provided the Photocopy
Masters have been purchased by their school. No part of
these Questionsheets may be reproduced or transmitted,
in any other form or by any other means, without the
prior permission of the publisher. All rights are reserved.
This license agreement is covered by the laws of England
and Wales © Curriculum Press March 2008.
urriculum
www.curriculum-press.co.uk
Curriculum Press • Bank House • 105 King Street • Wellington • Shropshire • TF1 1NU
AS Level
TOPIC 8
Questionsheet 1
Do not
write in
margin
OXIDATION NUMBERS I
a) Work out the oxidation number of nitrogen in each of the following substances.
(i)
NO
..........................................................
(v)
NH 3
.................................................................
(ii) NO 2 ..........................................................
(vi) HNO 3 .................................................................
(iii) NF 3
(vii) N 2
..........................................................
(iv) N2O5 ..........................................................
.................................................................
(viii) N 2 O
.................................................................
[8]
b) Work out the oxidation number of chlorine in each of the following substances.
Cl2O .........................................................
(iii) ClO2
...................................................................
(ii) Cl2O7 .........................................................
(iv) KCl
...................................................................
[4]
(i)
c) Work out the oxidation number of the named elements in the following ions:
Chlorine in ClO -
.............................
(vi) Chlorine in ClO4-
(ii) Chromium in CrO42-
.............................
(vii) Chromium in Cr2O72- .............................
(iii) Aluminium in AlF63-
.............................
(viii) Copper in CuF42-
.............................
(iv) Oxygen in OH -
.............................
(ix) Oxygen in O22-.
.............................
(v) Phosphorus in PO43-
.............................
(x) Nitrogen in NO2-
.............................
(i)
.............................
[10]
d) Complete the following names by adding the appropriate Roman numeral:
SO 42- sulfate(
) ion
(ii) SO 32- sufate(
) ion
(iii) CuO
copper(
) oxide
(iv) Cu2O copper(
) oxide
(i)
(v) NaClO3
sodium chlorate(
)
[5]
TOTAL / 27
AS Level
TOPIC 8
Questionsheet 2
Do not
write in
margin
OXIDATION NUMBERS II
a) Calculate the oxidation number of the stated element in each of the following species.
(i)
Mn in MnO42- ........................................................................................................................................ [1]
(ii) N in HNO3
........................................................................................................................................ [1]
(iii) S in S2O32-
........................................................................................................................................ [1]
(iv) Cr in Cr2O72- ........................................................................................................................................ [1]
(v) V in VO2+
........................................................................................................................................ [1]
b) What exceptions are there to the rule that the oxidation number of oxygen in its compounds is -2, while that of
hydrogen is +1?
...........................................................................................................................................................................
...........................................................................................................................................................................
....................................................................................................................................................................... [3]
c) Why is the oxidation number of fluorine in its compounds always -1?
...........................................................................................................................................................................
....................................................................................................................................................................... [2]
d) NH3 and AsH3 are related compounds in that they are both covalent hydrides of Group 5 elements.
Why is it that hydrogen has an oxidation number of +1 in NH3 but -1 in AsH3?
...........................................................................................................................................................................
....................................................................................................................................................................... [2]
e) Explain why ammonia dissolving in water does not involve a redox change
...........................................................................................................................................................................
....................................................................................................................................................................... [1]
f) When a species is oxidised or reduced, what relationship is there between the change in oxidation number of
the central atom and the number of electrons lost or gained? Illustrate your answer by referring to the MnO4and Cr2O72- ions, both in acidic solution.
...........................................................................................................................................................................
...........................................................................................................................................................................
...........................................................................................................................................................................
...........................................................................................................................................................................
...........................................................................................................................................................................
....................................................................................................................................................................... [5]
TOTAL / 18
AS Level
TOPIC 8
Questionsheet 3
Do not
write in
margin
INTRODUCTION TO REDOX
a) (i) Define oxidation and reduction in terms of electrons.
...........................................................................................................................................................................
....................................................................................................................................................................... [2]
(ii) Explain why it is that oxidation and reduction always occur together.
...........................................................................................................................................................................
....................................................................................................................................................................... [2]
b) (i)
Oxidation used to be defined as ‘combination with oxygen’. Explain why, even though the definition
has now been broadened, it is still generally true to say that combination with oxygen is oxidation.
...........................................................................................................................................................................
...........................................................................................................................................................................
....................................................................................................................................................................... [3]
(ii) When oxygen reacts with fluorine, converting it into oxygen difluoride, OF2, does the fluorine become
oxidised? Explain your answer.
...........................................................................................................................................................................
....................................................................................................................................................................... [2]
c) For each of the following, state whether or not it is a redox reaction (Y/N) and give a reason if it is or a reaction
type if not:
I
HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)
Redox (Y/N)? ........................................................................................................................................ [1]
Reason/reaction type ........................................................................................................................... [1]
II
AgNO3(aq) + KCl(aq) → AgCl(s) + KNO3(aq)
Redox (Y/N)? ........................................................................................................................................ [1]
Reason/reaction type ........................................................................................................................... [1]
III
Ca(s) + Cl2(g) → CaCl2(s)
Redox (Y/N)? ........................................................................................................................................ [1]
Reason/reaction type ........................................................................................................................... [1]
IV PCl3(l) + 3H2O(l) → H3PO3(aq) + 3HCl(aq)
Redox (Y/N)? ........................................................................................................................................ [1]
Reason/reaction type ........................................................................................................................... [1]
TOTAL / 17
AS Level
TOPIC 8
Questionsheet 4
Do not
write in
margin
OXIDISING AGENTS AND REDUCING AGENTS
a) Oxidation and reduction are brought about by substances referred to as oxidising agents and reducing agents.
Define each of these substances in terms of electrons.
Oxidising agent ............................................................................................................................................. [1]
Reducing agent .............................................................................................................................................. [1]
b) Why is it that, during a redox reaction, the oxidising agent always becomes reduced, while the reducing agent
becomes oxidised?
...........................................................................................................................................................................
...........................................................................................................................................................................
....................................................................................................................................................................... [3]
c) Some oxidising agents, e.g. potassium dichromate(VI), function much better in acidic solution than in neutral
solution. Explain this.
...........................................................................................................................................................................
...........................................................................................................................................................................
....................................................................................................................................................................... [3]
d) Explain why hydrochloric acid can be used for titrations using dichromate(VI) but not with manganate(VII)
...........................................................................................................................................................................
...........................................................................................................................................................................
....................................................................................................................................................................... [3]
The terms oxidant and reductant can be used to mean ‘oxidising agent’ and ‘reducing agent’ respectively.
During a redox reaction, the oxidant becomes reduced and the reductant becomes oxidised.
e) Complete the following table by inserting the formulae of the species to which the given oxidants are reduced,
and any colour change, precipitate formation or evolution of gas which is observed.
Oxidant
Species on reduction
Observation
MnO4- in acidic solution
Cr2O72- in acidic solution
Bromine water
Iodine solution
[8]
f) Complete the next table to show (by formula) the species to which the given reductants are oxidized.
Reductant
Species on oxidation
I- in neutral solution
Zn in acidic solution
Fe2+ in acidic solution
[3]
TOTAL / 22
AS Level
TOPIC 8
Questionsheet 5
Do not
write in
margin
IONIC HALF-EQUATIONS AND THEIR COMBINATION
Throughout this Questionsheet, for simplicity, state symbols may be omitted.
a) Write ionic half-equations for the following oxidation changes.
(i)
Ethanedioic acid to carbon dioxide.
....................................................................................................................................................................... [1]
(ii) Sulfite ions to sulfate ions.
....................................................................................................................................................................... [1]
(iii) Chlorine to chlorate(I) during disproportionation.
....................................................................................................................................................................... [1]
(iv) Hydrogen peroxide to oxygen.
....................................................................................................................................................................... [1]
b) Write ionic half-equations for the following reduction changes.
(i)
Manganate(VII) ions to manganese(II) ions in acidic solution.
....................................................................................................................................................................... [1]
(ii) Iodate(V) ions to iodine in acid.
....................................................................................................................................................................... [1]
(iii) Dichromate(VI) ions to chromium(III) ions in acidic solution.
....................................................................................................................................................................... [1]
(iv) Aqueous nitrate ion to ammonia.
....................................................................................................................................................................... [1]
c) Combine the ionic half-equations from a)(ii) and b)(i) to obtain the complete ionic equation for the redox
reaction between manganate(VII) ions and sulfite ions in acidic solution.
...........................................................................................................................................................................
...........................................................................................................................................................................
...........................................................................................................................................................................
....................................................................................................................................................................... [3]
d) Titanium dissolves in concentrated hydrochloric acid to give titanium(III) chloride and hydrogen. Construct
an ionic equation for this reaction by writing down two ionic half-equations and then combining them.
...........................................................................................................................................................................
...........................................................................................................................................................................
....................................................................................................................................................................... [3]
TOTAL / 14
AS Level
TOPIC 8
Questionsheet 6
METALS WITH ACIDS
Whenever a metal dissolves in an acid, a redox reaction occurs. The metal is always the reductant, but the identity
of the oxidant (i.e. the ion or molecule which oxidises the metal) depends on the particular acid which is used.
a) This part of the Questionsheet refers to zinc dissolving in dilute sulfuric acid, which you can assume is fully
dissociated into H+ and SO42- ions. The products are zinc sulfate and hydrogen.
(i) How could you test for the evolution of hydrogen?
...........................................................................................................................................................................
....................................................................................................................................................................... [2]
(ii) Write two ionic half-equations for the change.
...........................................................................................................................................................................
....................................................................................................................................................................... [2]
(iii) Combine the half-equations into an overall ionic equation.
....................................................................................................................................................................... [1]
(iv) Identify the oxidant in this reaction ...................................................................................................... [1]
b) This part refers to zinc dissolving in concentrated sulfuric acid (98% H2SO4). For the purposes of this
Questionsheet, you should assume it is undissociated, i.e. it consists entirely of H2SO4 molecules. The products
are zinc sulfate, sulfur dioxide and water.
(i) Describe a chemical test for the evolution of sulfur dioxide.
...........................................................................................................................................................................
....................................................................................................................................................................... [2]
(ii) Write two ionic half-equations for the change.
...........................................................................................................................................................................
....................................................................................................................................................................... [2]
(iii) Combine the half-equations into an overall ionic equation.
....................................................................................................................................................................... [1]
(iv) Identify the oxidant in this reaction ...................................................................................................... [1]
c) The reaction between zinc and concentrated nitric acid (which you can assume is dissociated into H+ and NO3ions) is given by the following equation: 4Zn(s) + 10HNO3(aq) → 4Zn(NO3)2(aq) + NH4NO3(aq) + 3H2O(l)
(i) Rewrite this equation, first as a complete ionic equation, and then as two ionic half-equations.
Complete ionic equation ....................................................................................................................... [1]
Ionic half-equations ..................................................................................................................................
............................................................................................................................................................... [2]
(ii) Identify the oxidant in this reaction ...................................................................................................... [1]
d) When copper dissolves in concentrated nitric acid, the principal nitrogen-containing product is NO2 rather
than NH4NO3. How do you account for this?
...........................................................................................................................................................................
....................................................................................................................................................................... [2]
TOTAL / 18
Do not
write in
margin
AS Level
TOPIC 8
Questionsheet 7
Do not
write in
margin
RELATIONSHIP BETWEEN CHANGE IN OXIDATION NUMBER
AND REACTION STOICHIOMETRY
Carbon monoxide can be prepared by reacting a metal carbonate with hydrazine, N2H4, as shown by the ‘unbalanced
equation’ referred to as Scheme X.
N2H4 + CO32- → N2 + CO + OH-
Scheme X
a) Assign an oxidation number to each element (i.e. N, H, C & O) in all species of Scheme X.
N2H4
+
CO32-
N = ..............
C = ...............
H = ..............
O = ..............
→
N2
+
N = ................
CO
+
OH-
C = ...............
O =..............
O = ..............
H =.............
[5]
b) Hence state which species becomes oxidised and which is reduced.
Species oxidised ............................................................................................................................................. [1]
Species reduced ............................................................................................................................................. [1]
c) For hydrazine, write down the following.
(i)
The increase in oxidation number of nitrogen ...................................................................................... [1]
(ii)
The number of N atoms which are oxidised in one molecule of N2H4 ................................................. [1]
(iii) Hence, the number of electrons which are lost by one molecule of N2H4 ............................................ [1]
d) For the carbonate ion, write down the following.
(i)
The decrease in oxidation number of carbon ........................................................................................ [1]
(ii) The number of C atoms which are reduced in one CO32- ion ................................................................ [1]
(iii) Hence, the number of electrons which are gained by one CO32- ion ..................................................... [1]
e) Given that the number of electrons which are lost on oxidation must be equal to the number of electrons which
are gained on reduction, state how many carbonate ions are reduced for each molecule of hydrazine which is
oxidised.
....................................................................................................................................................................... [1]
f) Use this information to convert Scheme X into a balanced equation.
....................................................................................................................................................................... [1]
TOTAL / 15
AS Level
TOPIC 8
Questionsheet 8
Do not
write in
margin
DISPROPORTIONATION
a) Define the term disproportionation.
...........................................................................................................................................................................
....................................................................................................................................................................... [2]
b) (i)
Write an ionic equation for the reaction that occurs when chlorine dissolves in a cold aqueous solution
of sodium hydroxide.
....................................................................................................................................................................... [1]
(ii)
Explain this reaction in terms of disproportionation. Support your answer by referring to the changes
that occur in the oxidation number of chlorine.
...........................................................................................................................................................................
...........................................................................................................................................................................
....................................................................................................................................................................... [3]
c) One of the reaction products of b)(i) in turn disproportionates when heated to temperatures above 70 oC.
Explain why, when this happens, the oxidation number of chlorine increases by 4 but decreases by only 2.
...........................................................................................................................................................................
...........................................................................................................................................................................
...........................................................................................................................................................................
....................................................................................................................................................................... [4]
d) Copper(I) compounds (except for complexes) are unstable in aqueous solution and decompose by
disproportionation. Suggest what you would expect to observe when the white soluble salt, copper(I) sulfate,
dissolves in water and write a chemical equation for the reaction.
Observations .................................................................................................................................................. [2]
Equation ........................................................................................................................................................ [1]
e) Manganate(x) disproportionates into manganese(IV) oxide and manganate(VII) in acid, the manganese products
being in the ratio 1:2
(i)
Deduce a value for x and give a formula for the original ion
....................................................................................................................................................................... [2]
(ii) Write an ionic equation for the reaction.
....................................................................................................................................................................... [2]
TOTAL / 17
AS Level
TOPIC 8
Questionsheet 9
Do not
write in
margin
EXTRACTION OF ALUMINIUM
a) State one general advantage and one disadvantage of the method of electrolytic reduction over the reduction
of ores by carbon.
Advantage ..................................................................................................................................................... [1]
Disadvantage ............................................................................................................................................... [1]
b) Why can aluminium not be obtained by reducing the oxide with carbon?
....................................................................................................................................................................... [1]
c) Draw a diagram to show the electrolysis cell used to extract aluminium from purified bauxite, and label it to show:
(i) the composition and temperature of the electrolyte,
[2]
(ii) the anode and cathode, and the materials from which they are made,
[2]
(iii) how aluminium is removed.
[1]
d) Write an ionic equation for the reaction occurring at each electrode.
Anode reaction............................................................................................................................................... [1]
Cathode reaction ........................................................................................................................................... [1]
e) Why are these plants often situated in mountainous regions?
...........................................................................................................................................................................
....................................................................................................................................................................... [2]
f) Give three major environmental concerns associated with the overall process of extracting aluminium from
bauxite.
...........................................................................................................................................................................
...........................................................................................................................................................................
....................................................................................................................................................................... [3]
g) List four main variable costs associated with the process.
...........................................................................................................................................................................
...........................................................................................................................................................................
...........................................................................................................................................................................
....................................................................................................................................................................... [4]
TOTAL / 18
AS Level
TOPIC 8
Questionsheet 10
EXTRACTION OF METALS BY REDUCTION OF OXIDE OR CHLORIDE
a) In the extraction of lead, galena, PbS, is first converted into lead(II) oxide, PbO, and then reduced by carbon to
give the metal and carbon dioxide
(i)
How is a sulfide ore converted to the corresponding oxide?
....................................................................................................................................................................... [1]
(ii) Write an equation for the conversion of lead(II) sulfide to lead(II) oxide.
....................................................................................................................................................................... [1]
(ii) Write an equation for the reduction of the oxide.
....................................................................................................................................................................... [1]
b) Although titanium can be extracted by reducing TiO2 with carbon, the method is unsatisfactory. Explain why.
...........................................................................................................................................................................
....................................................................................................................................................................... [2]
c) In the Kroll process, TiO2 is first converted into TiCl4, which is then reduced to the metal.
(i)
How is TiO2 converted into TiCl4?
...........................................................................................................................................................................
...........................................................................................................................................................................
....................................................................................................................................................................... [3]
(ii) How is the TiCl4 purified?
....................................................................................................................................................................... [1]
(iii) What reducing agent is used to convert TiCl4 to titanium?
....................................................................................................................................................................... [1]
(iv) Why must the reduction be carried out in the absence of air?
....................................................................................................................................................................... [1]
d) Tungsten (VI) oxide is obtained from the treatment of tungsten ores with alkali.
(i)
Suggest an equation for the reduction of the oxide with hydrogen
...........................................................................................................................................................................
....................................................................................................................................................................... [2]
(ii) Hydrogen is less economic than using carbon. Suggest why hydrogen is employed as the reducing agent
....................................................................................................................................................................... [1]
(iii) Suggest a risk associated with the process
....................................................................................................................................................................... [1]
TOTAL / 15
Do not
write in
margin
AS Level
TOPIC 8
Questionsheet 13
Do not
write in
margin
BLAST FURNACE
a) (i)
Name the three materials that are fed into the top of a blast furnace.
....................................................................................................................................................................... [3]
(ii) What other material is essential to the operation of the furnace?
....................................................................................................................................................................... [1]
b) (i)
State the two reducing agents which take part in reactions in the blast furnace.
....................................................................................................................................................................... [2]
(ii) Only one of these reducing agents is fed into the furnace: the second is formed from it. Write two
chemical equations to show how this happens.
Equation 1 ............................................................................................................................................. [1]
Equation 2 ............................................................................................................................................. [1]
c) Write chemical equations to show the formation of iron from its ore:
(i) in the upper, cooler regions of the furnace.
....................................................................................................................................................................... [1]
(ii) in the lower, hotter regions.
....................................................................................................................................................................... [1]
TOTAL(Continued...)
/
AS Level
TOPIC 8
Questionsheet 11 Continued
Do not
write in
margin
BLAST FURNACE
d) Write two equations to show how one of the materials in the blast furnace removes sand (SiO2) from the iron
ore.
Equation 1 .................................................................................................................................................... [1]
Equation 2 .................................................................................................................................................... [1]
e) Why is it beneficial, at the bottom of the furnace, to have a layer of molten slag floating on molten iron?
....................................................................................................................................................................... [1]
f) State two features of a blast furnace which improve its energy efficiency.
Feature 1 ....................................................................................................................................................... [1]
Feature 2 ....................................................................................................................................................... [1]
g) Suggest why a blast furnace is wider at the base than it is at the top.
...........................................................................................................................................................................
...........................................................................................................................................................................
....................................................................................................................................................................... [2]
TOTAL / 17
AS Level
TOPIC 8
Questionsheet 12
Do not
write in
margin
TEST QUESTION I
a) Nitric acid is manufactured by the Ostwald process, which involves the following three stages.
Stage 1 Oxidation of ammonia with oxygen over a hot platinum-iridium catalyst:
4NH3(g) + 5O2(g) → 4NO(g) + 6H2O(g)
Stage 2 Conversion of nitrogen monoxide to nitrogen dioxide with oxygen at a lower temperature:
2NO(g) + O2(g)→ 2NO2(g)
Stage 3 Dissolving nitrogen dioxide in water in the presence of oxygen:
4NO2(g) + 2H2O(l) + O2(g) → 4HNO3(aq)
(i)
Write down the change in oxidation number of nitrogen at each of the three stages.
Change at Stage 1 ................................................................................................................................. [1]
Change at Stage 2 ................................................................................................................................. [1]
Change at Stage 3 ................................................................................................................................. [1]
(ii) If nitrogen dioxide were to be dissolved in water in the absence of oxygen, it would give a mixture of
nitric acid, HNO3, and nitrous acid, HNO2. Write an equation for this reaction, state the oxidation number
of nitrogen in NO2, HNO3 and HNO2, and hence deduce the type of reaction that occurs.
Equation ................................................................................................................................................ [1]
Oxidation number of N in : NO2 ....................... HNO3 ......................... HNO2 .......................... [2]
Type of reaction ..................................................................................................................................... [1]
b) As a powerful oxidising agent, concentrated nitric acid presents serious health and safety hazards whenever it
is used in the laboratory. Name three major hazards and state what precautions you would take to minimise the
danger in each case. (Do not mention ‘goggles’ and ‘laboratory overalls’, which must always be worn in the
laboratory.)
Hazard 1 ........................................................................................................................................................ [1]
Precaution ..................................................................................................................................................... [1]
Hazard 2 ........................................................................................................................................................ [1]
Precaution ..................................................................................................................................................... [1]
Hazard 3 ........................................................................................................................................................ [1]
Precaution ..................................................................................................................................................... [1]
c) ‘Starch-iodide’ papers are commonly used in the laboratory as a test for oxidising agents. (They are strips of
paper impregnated with potassium iodide and starch.) State what is observed when starch-iodide paper is
dipped into a solution of an oxidising agent and explain the chemistry of the test.
Observation ................................................................................................................................................... [1]
Chemistry ...................................................................................................................................................... [2]
TOTAL / 16
AS Level
TOPIC 8
Questionsheet 13
Do not
write in
margin
TEST QUESTION II
a) Chromium occurs naturally as a mineral called chromite or chrome ironstone, which can be regarded as a
mixed oxide of iron and chromium, FeO.Cr2O3. Pure chromium is obtained from this by a four stage process
summarised by the following diagram:
FeO.Cr2O3
Stage 1
Heat in air
with K2CO3
K2CrO4
Stage 2
H2SO4
Stage 3
K2Cr2O7
Heat with
carbon
Stage 4
Cr2O3
Al
Cr
Complete the table below to show, for each stage, the change in oxidation number of chromium and hence
state which stage does not involve oxidation-reduction.
Change in oxidation number of Cr
From
To
Stage 1
Stage 2
Stage 3
Stage 4
[4]
Stage which does not involve oxidation-reduction ........................................................................................ [1]
b) Magnesium chloride, which is electrolysed to produce magnesium, is manufactured by passing chlorine over
a heated mixture of magnesium oxide and carbon :
MgO(s) + C(s) + Cl2(g) → MgCl2(s) + CO(g)
State which element is oxidised and which is reduced, and hence identify the oxidising agent and reducing
agent in this reaction.
Element oxidised ........................................................................................................................................... [1]
Element reduced ............................................................................................................................................ [1]
Oxidising agent ............................................................................................................................................. [1]
Reducing agent .............................................................................................................................................. [1]
c) TiO2, known in industry as ‘titanium dioxide’, dissolves in concentrated sulfuric acid to give an orange solution
of ‘titanyl sulfate’, TiO2+ SO42-. It also reacts with fused potassium hydroxide to give potassium titanate,
(K+)2TiO32-.
(i) Write down the oxidation number of titanium in each of the following :
TiO2 ........................................................................................................................................................ [1]
TiO2+ ........................................................................................................................................................ [1]
TiO32- ........................................................................................................................................................ [1]
(ii) Hence state whether each of these conversions involves ‘oxidation’, ‘reduction’ or ‘neither’.
TiO2 → TiO2+ ........................................................................................................................................... [1]
TiO2 → TiO32- ........................................................................................................................................ [1]
TOTAL / 14