Reactivity Exam Questions-2

8/16/2019 Reactivity Exam Questions-2

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Reactivity Series IGCSE Year 11 Revision

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Questions

Q1

A student found this information about hydrogen.

(a) (i) The student repeated Boyle's experiment using iron and dilute sulfuric acid.tate t!o obser!ations that he could ha!e made.

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..............................................................................................................................................(ii) "omplete the #ord e$uation for this reaction.

"1$iron % sulfuric acid & ....................................... % .........................................

(b) Balance the e$uation for the complete combustion of hydrogen."1$

..................... % ..................... & .....................

(c) To sho# that the li$uid produced by burning hydrogen #as pure #ater* a student carried out achemical test and a physical test.(i) The chemical test in!ol!ed adding a fe# drops of the li$uid to a sample of anhydrous copper(++)sulfate.tate the colour change obser!ed.

"#$+nitialcolour ...........................................................................................................................................................,inalcolour.............................................................................................................................................................

(ii) -lace a cross in one box to sho# the formula of the compound formed in this chemical test.

"1$ % "u()

& "u

C "u.

D "u./

(iii) The physical test in!ol!ed measuring a property of the li$uid.

tate a suitable physical property and gi!e the !alue for pure #ater.



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-hysical property

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0alue

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(d) (i) uggest #hat property of hydrogen ma1es it suitable for filling balloons."1$

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(ii) elium is no# used instead of hydrogen to fill balloons.

tate the property of helium that ma1es it more suitable than hydrogen for filling balloons.

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(e) 2rite an e$uation* including state symbols* to sho# the process that occurs #hen hydrogen isli$uefied.

"1$ .............................................................................................................................................."Total 'or Question ( 1# marks$



Q#

The reacti!ity of metals can be studied using displacement reactions. +n these reactions* one metal isadded to a solution of a salt of a different metal.+f a displacement reaction occurs* there is a temperature rise. A student used the follo#ing method in a series of experiments.

•-our some metal salt solution into a polystyrene cup supported in a glass bea1er and record the

temperature of the solution.

• Add a 1no#n mass of a metal and stir.

•3ecord the maximum temperature of the mixture.(a) uggest three !ariables that should be 1ept the

same for the student's experiments to be a fair test.")$

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(b) The student used a thermometer to measure the temperature rise. The diagrams sho# thethermometer readingsbefore and after adding the metal.

4se the diagrams to complete the table.

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(c) The student used copper(++) sulfate solution in all her experiments. he used fi!e different metals. he

did not 1no#the identity of the metal labelled *.

The student did each experiment t#ice. The table sho#s her results.



(i) 2hich of the metals ga!e the least reliable temperature rise56xplain your choice.

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7etal

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6xplanation

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..............................................................................................................................................(ii) +dentify the most reacti!e of the metals used.6xplain ho# the results sho# that it is the most reacti!e.

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7etal

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6xplanation

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..............................................................................................................................................(iii) 2hy is there no temperature rise #hen sil!er is added to copper(++) sulfate solution5

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(i!) 2hy do the results ma1e it impossible to decide #hich of the metals is the least reacti!e5"1$

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..............................................................................................................................................(d) A #ord e$uation for one of the reactions is

8inc % copper(++) sulfate & copper % 8inc sulfate

2rite a chemical e$uation for this reaction."1$

.............................................................................................................................................."Total 'or Question ( 1) marks$



Q)

The diagrams sho# the reactions of some metals #ith cold #ater and #ith dilute hydrochloric acid.

(a) Ans#er the follo#ing $uestions* using only the metals that appear in the diagrams.(i) Name t!o metals that react #ith cold #ater.

"#$..............................................................................................and ..............................................................................................

(ii) Name one metal that reacts #ith dilute hydrochloric acid but not #ith cold #ater."1$

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(iii) Arrange the fi!e metals in order of reacti!ity.")$

+ost reactive metal ..............................................................................

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,east reactive metal ..............................................................................(b) ome magnesium po#der is added to dilute sulfuric acid in a test tube.

A colourless solution is formed and a gas is gi!en off.2hen more magnesium is added* the reaction continues for a #hile and then stops* lea!ing some magnesium po#der in the test tube.2hen a flame is placed at the mouth of the test tube* the gas burns #ith a s$uea1y pop.(i) +dentify the gas produced.

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..............................................................................................................................................(ii) uggest #hy the reaction stops.

"1$

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(iii) tate the name of the colourless solution. "1$

..............................................................................................................................................(i!) o# could you separate the magnesium po#der from the colourless solution5

"1$



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..............................................................................................................................................(c) +n some fire#or1s* magnesium po#der reacts $uic1ly #ith oxygen in the air.9uring this reaction heat energy is produced.

(i) 2hat name is gi!en to reactions in #hich heat energy is produced5"1$

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(ii) Name the compound formed #hen magnesium reacts #ith oxygen. "1$

.............................................................................................................................................."Total 'or Question ( 1# marks$



Q-

Aluminium and iron ha!e some similar properties.

Both metals

• are malleable

• are ductile (can be dra#n into a #ire)

• are good conductors of electricity

• are good conductors of heat

• ha!e a high melting point

(a) (i) "hoose t#o properties from the list that ma1e iron a suitable metal for saucepans.

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(ii) "hoose t#o properties from the list that ma1e aluminium a suitable metal for po#er cables."#$

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(b) teel is an alloy containing iron.

These are three differences bet#een steel and aluminium.

• steel can rust but aluminium resists corrosion

• steel has a higher density than aluminium

• steel is much stronger than aluminium

(i) 4se information from the list to suggest #hy steel is the better metal for ma1ing bridges. "1$

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(ii) 4se information from the list to suggest #hy aluminium is the better metal for ma1ing aircraftbodies.

"1$

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(c) The reaction bet#een aluminium and iron(+++) oxide is 1no#n as a thermite reaction.

The diagram sho#s ho# this thermite reaction can be carried out.

The magnesium ribbon is lit to ignite the reaction mixture.The reaction is highly exothermic.The e$uation for the reaction is

Al % ,e; & Al; % ,e

(i) 2hat is meant by the term e.othermic5"1$

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(ii) 2hat does the reaction suggest about the reacti!ity of aluminium compared to the reacti!ity ofiron56xplain your ans#er.

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(iii) 2hich element is oxidised in this thermite reaction5<i!e a reason for your ans#er.

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(d) This thermite reaction can be used to =oin together t#o rails on a rail#ay line.

The reaction mixture is ignited and molten iron pours into the mould. The mould is remo!ed and themolten iron solidifies to create a =oin bet#een the t#o rails.6xplain #hy the iron produced in the reaction is molten.

"1$

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"Total 'or /uestion ( 1# marks$



Q0

A student carries out an in!estigation to compare the reacti!ities of four metals* aluminium* copper* 8incand 7.

e adds strips of 8inc to the a$ueous solutions of the nitrates of each metal.

After a fe# minutes he remo!es the strips of 8inc and examines them.

The table sho#s his results.

(a) Name the substance that causes the bro#n coating on the 8inc.

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(b) tate #hy there is no change in the experiment #ith 8inc nitrate solution.

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(c) The student repeats the experiment #ith strips of metal 7 instead of strips of 8inc. The table sho#shis results.

4sing information from both tables of results* place the metals aluminium* copper* 8inc and 7 in order



of decreasing reacti!ity."#$

most reacti!e ...................................................................

...................................................................

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least reacti!e ...................................................................

(d) 7agnesium reacts #ith an a$ueous solution of sil!er nitrate.

The reaction can be represented by the ionic e$uation

(i) tate #hy this reaction is described as a redox reaction."1$

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(ii) 6xplain* in terms of electrons* #hich species is beha!ing as an oxidising agent in this reaction."#$

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"Total 'or /uestion ( marks$



Q2

Titanium is extracted from its main ore* rutile* in a three>stage process.

tage 3utile is heated #ith chlorine and co1e (carbon) at a temperature of about ?@@".

Ti % "l % " & Ti"l % "

tage Ti"l is then added to li$uid magnesium at a temperature of about @@" in an atmosphere ofargon.

Ti"l % 7g & Ti % 7g"l

9uring the reaction the temperature rises to about @@".

tage ; The magnesium chloride is remo!ed by distillation from the mixture formed in stage * lea!ingbehind pure titanium.

(a) +n stage * is the carbon oxidised or reduced5

<i!e a reason for your ans#er.

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(b) 2hat does the reaction in stage indicate about the reacti!ity of magnesium compared to thereacti!ity of titanium5

6xplain your ans#er.

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(c) +n stage ;* suggest #hy distillation can be used to remo!e magnesium chloride from titanium.



"1$

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(d) Titanium has these properties.

• it is corrosion resistant

• it has a high melting point

• it has a !ery high strength>to>#eight ratio

• it is non>toxic

"omplete the table to suggest an important property of titanium for each use.

"hoose from the four properties listed.

Cou must choose a different property for each use.

")$

"Total 'or Question ( marks$



Q

The thermite reaction is used on rail#ays to produce molten iron for =oining rails together. The diagramsho#s ho# this is done.

The e$uation for this thermite reaction is

Al % ,e; & Al; % ,e

(a) 2hat does this reaction sho# about the reacti!ity of iron compared to the reacti!ity of aluminium5

"1$

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(b) 2hy is this reaction described as displacement5

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(c) tate t#o reasons #hy the term oxidation applies to aluminium in this reaction.

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(d) Although the thermite reaction is exothermic* it only begins after a lot of heat energy is supplied.

o# is this heat energy supplied5



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"Total 'or /uestion ( 0 marks$

E.aminer3s Re4ort

D.

+n this $uestion about hydrogen* fe# candidates scored both mar1s in (a)(i)* the commonest error beingthe formation of a precipitate.* #hile in (a)(ii)* #ater often appeared instead of hydrogen andoccasionally an incorrect oxidation state appeared in iron sulfate. -arts (c)(i)>(ii) #ere generally correct*but unsuitable properties such as p #ere occasionally seen. +n part (d)* most scored the mar1 in (i)

but rarely in (ii)* #here helium #as often stated to be less dense than hydrogen. ,e# correct ans#ers#ere seen in (e)* #here the term Eli$uefiedE #as not understood* the commonest error being to includeoxygen as a reactant and #ater as the product.

Q#

-art (a) of this $uestion about metal displacement reactions caused problems for candidates > somesuggestions about same starting temperature and same polystyrene cup #ere unsuitable* #hile manyother ans#ers #ere incomplete (often mass or !olume) or incorrect (mass of salt). -art (b) #asgenerally #ell ans#ered* although #ith some misreadings of the scales (F.;/ instead of F.F and .instead of .). -art (c) pro!ed challenging for many candidates. Although most chose magnesium in

(i) the second mar1 #as not scored because of the lac1 of a comparison > stating that there is a largedifference in the temperatures for magnesium is not sufficient. imilarly in (ii)* it is not sufficient to statethat the temperature rise is high* although the mar1 #ould ha!e been a#arded for stating that thetemperature rise #as the highest (or higher than for the other metals). Ans#ers to (c)(iii) #ere usuallycorrect* but in (i!) the commonest non>scoring ans#er #as Ethe temperature changes for sil!er and Gare the sameE* rather than Esil!er and G sho#ed no temperature riseE. The e$uation in (d) #as oftencorrect* although some started #ith "u* no doubt because of the gi!en oxidation state.

Q)

This #as a !ery high scoring $uestion* as #as expected. ome candidates did not read the gi!en

information carefully and hence stated in (b)(ii) that both reactants had been used up or that themagnesium had completely reacted. The most common mista1e in (b)(iii) #as to state that thecolourless solution #as magnesium sulfide.

Q-

,e# incorrect ans#ers #ere seen in either (a) or (b). +n (c)(i)* the term 'exothermic' should be explained#ith reference to 'heat energy' (as in the specification)H 'heat'* but not =ust 'energy' is an acceptablealternati!e.

+n (c)(ii)* the second mar1 #as not a#arded to candidates #ho said that aluminium displaces 'oxygen' or'iron oxide'. A simple definition of oxidation I in terms of gain of oxygen I #as expected in (iii)* althoughan ans#er in terms of electron transfer #ere also accepted* as long as this did not contradict any ans#erin terms of oxygen.



-art (d) discriminated #ell bet#een candidates* #ith fe# using language correctly enough. All exothermicreactions release heat energy I but #ould not cause the change of state #e see here* as the heat energydissipates to the surroundings. ere* the 1ey is that the heat energy is contained and the result is that ahigh temperature is reached* abo!e the melting point of iron. +t #as this reference to temperature thateluded many.

Q0

"opper #as often gi!en as the correct ans#er to part (a)* but the incorrect ans#ers of copper (++) orcopper ions #ere also seen.

-art (b) #as generally poorly ans#ered. A !ery common error #as to state that 8inc cannot react #ith8inc* rather than 8inc cannot react #ith 8inc ions. +t #as considered too !ague to state merely that nodisplacement #ould occur.

"andidates had to combine information from t#o tables in order to deduce an ans#er to part (c). Thispro!ed problematical for some* although many fully correct ans#ers #ere seen. "ommon errors #ere tolist the nitrates instead of the metal* and to list the correct metals in re!erse order.

-art (d) (i) #as generally ans#ered #ell* usually in terms of both reduction and oxidation ta1ing place*although some chose correctly to state that both gain and loss of electrons #as occurring. Jac1 ofprecision in the ans#er #as the do#nfall for some* #ho stated* for example* that a redox reaction in!ol!eseither reduction or oxidation* rather than both.

There #ere some fully correct ans#ers to part (d) (ii)* but many failed to gain the first mar1 by stating thatsil!er* rather than the sil!er ion* #as acting as the oxidising agent. These candidates usually #ent on thestate that the sil!er #as gaining electrons so #ere a#arded the second mar1 on the basis of a 'near miss'

ans#er for the oxidising agent. ome thought that an oxidising agent #as a species that #as oxidised andhence ga!e magnesium* because it is losing electrons* as their ans#er.

Q2

-art (a) #as #ell ans#ered although some failed to offer a reason for their ans#er and others stated thatoxidation had ta1en place because the carbon had lost electrons rather than gained oxygen.

7ost recognised in (b) that magnesium #as more reacti!e than titanium* but some lost the explanationmar1 through careless use of language. ,or example* candidates should ha!e stated that magnesiumdisplaces titanium and not that it displaces chlorine.

+n part (c)* the examiners expected candidates to dra# on their 1no#ledge of the general principlesin!ol!ed in distillation of li$uid mixtures to reach the conclusion that magnesium chloride and titaniummust ha!e different boiling points. Again* ho#e!er* there #as some confusion bet#een melting points andboiling points* and some thought that magnesium chloride could be separated by distillation because it#as soluble in #ater.

All three mar1s #ere regularly gained in part (d)* although some lost mar1s through not reasoningscientifically* stating for example that the non>toxicity of titanium #as a rele!ant property for its use as apropeller* or that ha!ing a high melting point #as important #hen used in a hip replacement.



Q

-art (b) #as not #ell ans#ered #ith many candidates merely repeating the information gi!en in the$uestion by using the #ord 'displaces'. The examiners #ere loo1ing for a #ord or phrase that indicated

#hat is meant by displacement in this context. The t#o most common correct ans#ers #ere thataluminium replaces iron* or ta1es the place of iron. nly a third of the candidates #ere able to produce acorrect ans#er to (d). The rest did not recognise that is #as the burning of the magnesium in oxygen that#as generating the heat.

+ark Scheme

D.





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Q0





Q2

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Reactivity Exam Questions-2

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