CIE iGCSE Co-Ordinated Science C6.3 Redox Exam Style Questions Paper 3
Question
(a) Chlorine reacts with hydrogen to make hydrogen chloride.
(i) Construct the word equation for this reaction.
(ii) Hydrogen chloride gas is a covalent compound.
Explain why hydrogen chloride gas is a covalent compound and not an ionic compound.
(iii) Fig. 5.1 shows the electronic structure in atoms of hydrogen and chlorine.
Draw a dot-and-cross diagram to show the arrangement of outer-shell electrons in a molecule of hydrogen chloride gas.
(iv) Hydrogen chloride dissolves in water to make dilute hydrochloric acid.
The pH of the hydrochloric acid is found using a pH probe.
Describe one other way of finding the pH of dilute hydrochloric acid.
(v) Suggest the pH of the dilute hydrochloric acid.
(b) Table 5.1 shows information about three Group VII elements.
(i) Complete Table 5.1.
(ii) State the name given to Group VII of the Periodic Table.
(iii) Explain why chlorine, bromine and iodine are all in Group VII of the Periodic Table.
Use ideas about electrons in your answer.
▶️Answer/Explanation
Ans :
5(a)(i) hydrogen + chlorine → hydrogen chloride ;
5(a)(ii) two non-metals bonding ;
5(a)(iii) one pair of bonding electrons ;
all else correct ;
5(a)(iv) use universal indicator ;
colour indicates the pH ;
5(a)(v) any value between 1 and 3 ;
5(b)(i)
5(b)(ii) halogens ;
5(b)(iii) all have 7 electrons in their outer shell ;
Question
(a) Iron is a metal.
Circle three physical properties which are characteristic of metals.
good electrical conductor high melting point
low boiling point malleable
poor thermal conductor
(b) Fig. 11.1 shows a spanner made from an alloy of iron.
The composition of the alloy is shown in Table 11.1.
(i) Calculate the percentage of carbon in the alloy.
percentage = ………………………………………………%
(ii) The mass of the spanner is 80g.
Calculate the mass of chromium contained in the spanner.
mass of chromium = ……………………………………………… g
(iii) Suggest why the spanner is made from an alloy of iron and not pure iron.
…………………………………………………………………………………………………………………….
…………………………………………………………………………………………………………………….
(c) Iron is extracted from iron oxide using carbon monoxide.
iron oxide + carbon monoxide → iron + carbon dioxide
State the substance that is reduced in this reaction.
……………………………………………………………………………………………………………………………
(d) Iron reacts with two substances to make rust.
(i) Name the element and the compound that react with iron to make rust.
element ……………………………………………………………………………………………………………..
compound ………………………………………………………………………………………………………….
(ii) Barrier methods are used to stop iron rusting.
Name one substance used in a barrier method of rust prevention.
…………………………………………………………………………………………………………………….
(e) Recycling iron costs less than extracting iron from iron ore.
Suggest one other reason why iron needs to be recycled.
…………………………………………………………………………………………………………………….
…………………………………………………………………………………………………………………….
▶️Answer/Explanation
Ans: 11(a) good electrical conductor
high melting point
malleable
1 correct ;
3 correct ;
11(b)(i) 2% ;
11(b)(ii) 1.6 (g) ;
11(b)(iii) stronger ;
11(c) iron oxide ;
11(d)(i) element–oxygen ;
compound–water ;
11(d)(ii) paint / oil / grease ;
11(e) iron is a finite resource ;
Question
(a) An atom of copper has a proton number of 29 and a nucleon number of 63.
(i) State the number of electrons in this copper atom. …………………………….
(ii) State the number of neutrons in this copper atom. …………………………….
(b) Copper oxide is heated with carbon. Copper and carbon dioxide are made.
(i) Write the word equation for this reaction.
(ii) In this reaction, reduction of copper in the copper oxide occurs.
Describe what is meant by the term reduction.
…………………………………………………………………………………………………………………….
…………………………………………………………………………………………………………………….
(iii) Explain why copper oxide is described as a basic oxide.
…………………………………………………………………………………………………………………….
…………………………………………………………………………………………………………………….
(c) Copper is a transition element.
Transition elements have high densities, high melting points and high boiling points. They are all metals.
State one other property of a transition element.
……………………………………………………………………………………………………………………..
……………………………………………………………………………………………………………………..
(d) (i) Brass is a mixture of copper and zinc.
State the term used to describe a mixture of metals.
…………………………………………………………………………………………………………………….
(ii) Brass is more malleable than either copper or zinc.
State the meaning of the term malleable.
…………………………………………………………………………………………………………………….
(iii) State the symbols of both copper and zinc.
copper symbol ……………………
zinc symbol ……………………
(e) A metal key is covered with a layer of copper by electroplating.
(i) The key is an electrode.
State which electrode is the key.
…………………………………………………………………………………………………………………….
(ii) Suggest a suitable electrolyte for electroplating the key.
…………………………………………………………………………………………………………………….
▶️Answer/Explanation
Ans: 8(a)(i) 29 ;
8(a)(ii) 34 ;
8(b)(i) copper oxide + carbon → copper + carbon dioxide ;
8(b)(ii) loss of oxygen ;
8(b)(iii) metal oxide / reacts with an acid to make a salt / neutralises an acid ;
8(c) any one from:
forms coloured compounds ;
acts as catalyst ; variable valency ;
8(d)(i) alloy ;
8(d)(ii) can be beaten into shape;
8(d)(iii) Cu and Zn ;
8(e)(i) cathode / negative ;
8(e)(ii) copper (II) sulfate ;