(11)oxidation and reduction

8/12/2019 (11)Oxidation and Reduction

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CHAPTER 11 : OXIDATION AND REACTION

1. Which of the following reactions occurs when molten lead(II) bromide iselectrolysed by using carbon electrodes?

A Redox reaction

B etal corrosion of reaction! Reduction of bromide ion at cathode" #xidation of bromide ion at anode

$. Which of the following statements about reduction and oxidation is true?

A Reduction is a %rocess of adding oxygenB #xidation is a %rocess of losing electron! Reduction is a %rocess where the oxidation number of a substance

increases." #xidation is the %rocess of adding hydrogen

&. Which of the following is reducing agent?

A 'incB Bromine water ! Acidified sodium dichromate(I)" Acidified %otassium manganate(II) acidified

. Which of the following reactions can*t be carried out byusing electrolysismethod?

A "anielle !ellB +xtraction of Aluminum

! "ecom%osition of molten ,ead(II)oxide" Recharging of ,ead Acid Accumulator

-. he diagram shows the set u% of the a%%aratus used to determine the %osition ofhydrogen in reacti/ity series of metal.

Which of the following metal oxide will be reduced by hydrogen?

I 'inc oxideII Iron(III) oxideIII !o%%er(II) oxide

1

etal oxide

"ry hidrogen gas

Burning of excesshydrogen gas

0eat



I ,eadII) oxide

A I and II onlyB II and III only! II and I only" II2 III and I only

3. Which of the following metal is easily oxidi4ed?

A 'incB ,ead! Aluminium" agnesium

5. Which of the following reactions do not in/ol/e redox reaction?

I "is%lacementII 6reci%itation

III !ombustionI 7eutralisation

A I and II onlyB I and III only! II and III only" II and I only

8. Which of the following is not a redox reaction?

A Rusting of ironB 7eutralisation reaction

! Reaction in nic9el cadmium cell" +xtraction of iro from their ore

:. Which of the following does not occur during extraction of sil/er using carbon?

A !arbon is oxidi4ed to carbon dioxideB in(I) oxide2 ;n#$ is reduced to tin! in(I) oxide2 ;n#$ act as a reducing agent" he oxidation number of carbon increases from < to =

1<. he following are the ad/antages of using carbon in extraction of metals except

A carbon is easily a/ailableB the cost for using carbon is chea%er ! carbon is located under tin in the reacti/ity series of metal" the by %roduct of the reaction which is carbon dioxide is easy to eliminate

2

!arbon is used as a reducing agent in the extraction of metals2 li9e iron and

tin from their ores.



11. +lectrolysis is a %rocess when a chemical substance is decom%osed by usingelectricity. Which of the following statement is true in an electrolysis %rocess?

A Anion recei/es electron at anodeB !ation recei/es electron at anode! !ation recei/es electron at cathode

" Anion releases electron at cathode

1$. he diagram shows the set>u% of the a%%aratus to determine the location ofcarbon in the reacti/ity series of metals.

What is the obser/ation at the end of ex%eriment?

A he mixture remains unchanged

B A brown solid is %roduced! !arbon reacts as an oxidising agent" !o%%er(II) oxide is oxidi4ed to co%%er

1&. What is the %ur%ose of carbon in the dis%lacement %rocess of iron?

A o reduce iron oxide B o decrease the melting %oint of iron ! o change iron ore to molten iron " o oxidi4ed the im%urity in iron ore

1. etal is located between iron and 4inc in the metal reacti/ity series.Which of the following metals can reduce oxide?

A !o%%er

B in ! ,ead " Aluminium

3

ixture of carbon %owder andco%%er(II) oxide %owder

6i%e>clay triangle

ri%od stand

Asbestos %a%er

Heat



1-. 7ic9el is located between iron and 4inc in the metal reacti/ity series.Which of the following metal can reduce nic9el oxide?

I in II ,ead III Aluminium

I agnesium

A I and II only B II and III only ! III and I only " I2II2III and I

13. All of the following metals can react as a reducing agent. Which one is thestrongest?

A Iron B ;odium

! ;il/er " Aluminium

15. Aluminium is extracted from its ore by electrolysis %rocess. Why is aluminiumcannot be extracted from its ore by heating it with carbon?

A Im%ure aluminium is %roducedB he cost of extraction is /ery high! Aluminium is more reacti/e than carbon" Aluminium can react with carbon

18. Which of the following shows the arrangement of the metal reacti/ity series with

oxygen in ascending order?

A @27a2g2Al B ;n2e2'n2!l ! 'n2e2;n26b

" !u20g2Ag2Au

1:. What is the name of com%ound which its formula is 7a!l#?

A ;odium chlorate(III)B ;odium(I) chlorate(I)! ;odium chlorate(II)

" ;odium(I) chlorate(II)

$<. Which of the following substances can oxidi4e iron(II)2 e$= ion toIron(II)2 e&= ion ?

A 'inc metalB "ilute sul%huric acid2 0$;#

! 0idrogen sul%hide gas" Acidicfied %otassium manganate(II) solution

4



$1. he following is an ionic euation2

Which of the following is true about that euation?

A C$= is oxidised to CB $= is a reducing agent! is an oxidising agent" donates electron to C$=

$$. he diagram below shows the set u% of the a%%aratus to change iron(III)2 e&= ionto iron(II)2 e$= ion.

Which of the following can re%lace 4inc %owder in this reaction?

A Bromine water B in(II) chloride solution! 6otassium hexacianoferate(II) solution

" Acidicfied %otassium manganate(II)

$&. he diagram shows the set>u% of the a%%aratus of an ex%eriment. he a%%aratusis left for an hour.

Which of the following statements is not true?

A +lectron transferred from electrode 6 to electrode DB 6otassium iodide solution turn to brown in colour ! he orange colour of acidified %otassium dichromate(II) decolourised" he oxidation number of chromium change from =3 to =&

5

+lectrode D+lectrode 6

Acidic dichromate(II) solution6otassium iodidesolution

"ilute sul%huric acid

X[s]

+ Y2+

[aq] X2+

[aq] + Y

[s]

Iron(III) ion solution

'inc %owder

0eat



$. he euation shows the changes of iodide ion to iodine.Which of the following cannot ma9e that ion change?

A !hlorine water.B 6otassium bromide solution.! Acidified %otassium manganate(II) solution.

" Acidified %otassium dichromate(I) solution.

$-. he table shows some chemical changes occur in four chemical reactions.

Reactions Ce!ica" can#es

$X

Y%

'inc atom changes to 4inc ionn#E changes to n$=

Iodide ion changes to iodine!hlorine molecule changes to chloride ion

Among the chemical changes abo/e2 which one loses electron?

A W and B W and C! and C" C and '

$3. he diagram shows the set u% of the a%%aratus of an ex%eriment to in/estigatethe effect of corrosion to iron

Which of the following decrease the rate of rusting of iron?

A Ion e $= acce%t electron B etal is less electro%ositi/e ! etal donate electron easily " ;odium chloride solution is a strong electrolyte

6

Iron nail

etal

;odium chloride solution



$5. he diagram shows the reaction between hot lead %owder with brominegas.

Which of the following is correct ?

A White solid is %roducedB ,ead atom oxidi4ed to lead(II) ion! #xidation number of Bromine decreases from < to >$" Bromine reacts as oxidising agent

$8. When the mixture of lead(II) oxide and aluminium %owder is heated2 lead is%roduced as shown in the euation below.

his reaction occur because2

A lead is an am%hoteric oxide B aluminium burns reacti/ely ! lead is a strong reducing agent

" aluminium is more reacti/e than lead

$:. Which of the following reaction2 shows that nitric is an oxidising agent?

A g = $07#& F g(7#&)$ = 0$

B !u# = $07#& F !u(7#&)$ = 0$#! 7a#0 = 07#& F 7a7#& = 0$#" !a!#& = $07#& F !a(7#&)$ = !#$ = 0$#

&<. he following chemical euation shows a halogen re%lacement reaction.

Which of the following statement is true about the reaction?

7

&' 2[#] + 2(I[aq] ) I2[#] + 2(&' [aq]

*PO + 2A" A"2O* + *P

0ot lead %owder

Bromine gas

Gas Har s%oon



A Bromine gas is a reducing agentB Bromide ion undergoes reduction! Iodide ion undergoes oxidation" #xidation number of iodine changes from =1 to =$

&1. In an ex%eriment2 concentrated sodium chloride solution is electrolised usingcarbon electrodes. Which of the following statement is true?

A 0idrogen20= ion isoxidi4edB !hloride2!l> ion acts as oxidi4ing agent! ;odium27a= ion undergoes oxidation" he oxidation number of sodium decreases from =1 to <

&$. he diagram shows a sim%le /oltaic cell.

Which of the following2 is reduced in that cell?

A !o%%er

B ;odium ion! agnesium" 0idrogen ion

&&. he diagram shows2 a few dro%s of acidic %otassium manganate(II) solution aredro%%ed into solution.

8

Acidified %otassiummanganate(II) solution

solution

V

!o%%er agnesium

;odium sul%hatesolution



If the %ur%le colour of acidified %otassium manganate(II) is decolourised2 solution should be

A bromine water.B iron(II) ion solution.! iron(III) ion solution.

" dichromate(I) ionsolution.

&. he diagram shows chemical cell.

Which of the following2 will ha%%en in the cell?

A agnesium rode becomes thinner.B he number of co%%er(II) ion increase.! !o%%er rode acts as a negati/e terminal." agnesium acts as an oxidation agent.

&-. he euation below re%resents the dis%lacement reaction between metal 2 Cand '.

!hoose the correct statement for this reaction?

A C is more electro%ositi/e than B and ' are oxidising agents ! he arrangement of reacti/ity in descending order is ' 22 C

" $= and C$= are reducing agents2 where as '$= is an oxidising agent

&3. he extraction of stanum is a redox reaction. Which of the following substancescan be use to reduce tin(I)oxide to tin?

A !arbon B !o%%er ! ,ead " ;il/er

9

!o%%er(II) sul%hate solution21.< mol dm>&

agnesium sul%hatesolution2 1.< mol dm>&

!o%%er metalagnesium metal

Reaction I : X ,s- + Y2+ ,aq- ) X2+ ,aq- + Y ,s-

Reaction II : %,s- + X2+ ,aq- ) %2+ ,aq- + X,s-



&5. Which of the following euations re%resents a redox reaction?

A 0!l = @#0 ) @!l = 0$#

B 0$;# = g ) g;# = 0$

! 6b(7#&)$ = @$!#& ) 6b!#& = $@7#&

" !a!#& = $0!l ) !a!l$ = !#$ = 0$

&8. he rusting of iron can be reduced by coiling the iron with other metals.Which ofthe following metals can %rotect the iron from rusting?

A 'inc B in ! !o%%er " ,ead

&:. Which of the following metals will increase in mass if heated in stim?

A !o%%er B agnesium! ,ead" ;il/er

<. Reaction between acidified %otassium dichromate2@$!r $#5 with iron(II)sul%hate2e;# solution is a redox reaction. In this reaction2 the oxidationnumber of chromium changes from

A =5 to =&B =3 to =&! =3 to =$" =- to =1

1. Which of the following shows the correct oxidation number of manganese?

.nO .nO2 .n2O*

A $ 3B 1 $ 3! 1 $ &" $ &

$.

Based on the abo/e statement2 which of the following metal can be used to%rotect tin from corrosion?

10

Corrosion of metal can be protected by using other metal



A 'incB !o%%er ! ,ead" ;il/er

&. he euation below2 shows half euation for a redox reaction.

rom the euation2 a $#5$> ion is reduced to two &= ion by recei/ing n

electrons2 (ne>) as shown in the abo/e half euation. What is the /alue of n?

A $B 3! 8" :

. he euation shows a redox reaction.

In the reaction2 what is the change in the oxidation number for nitrogen?

A >& to <B =& to <! =1 to >$" >$ to =$

-. When a %iece of iron %lated with metal was scratched2 the iron did not rust butwhen a %iece of metal %lated with iron was scratched2 the iron rusting /eryuic9ly. rom the abo/e obser/ations2 the arrangement of metals 2 C and iron indescending order in electrochemical series is

A Iron2 2 CB 2 iron2 C! 2 C2 iron" C2 iron

3. he following euation shows a reaction between hydrogen and excess air.

In the reaction2 the oxidation number of hydrogen changes from

A < to =1B < to =$! =$ to <" =1 to =$

11

&!u# = $70& F &!u = 7$ = &0$#

$0$ = #$ F $0$#

$#5$> = 10= = ne> F $&= = 50$#



5. he chemical euation shows a redox reaction.

Which of the following is the changes of the oxidation number of nitrogen?

A =- to =&B =3 to =! =& to =-" = to =3

8. Which of the following substances contains nitrogen with the highest oxidationnumber?

A 7$#

B @7#$

! 07#&

" 70!l

:. he euation below shows the reduction of iron(III) to iron(II) by ;n$=.What isthe /alue of n in ;nn=?

A &B ! -

" 3

-<. Which of the following %air of substances2 ha/e the same oxidation number forthe underlined elements?

A !r#$> and !r $#5

$>

B @7#$ and 7a7#&

! ;# $> and ;#&

$>

" @n# and n$#&

12

$@7#& F $@7#$ = #$

$e &=(a) = ;n$= (a) $ e$=(a) = ;n n=(a)



/TR0CT0RED 0E/TION/

/ECTION A

Answer all the uestions

1. he diagram shows the set u% of the a%%aratus to in/estigate transfer of

electrons at a distance between iron(II) sul%hate solution and

acidified %otassium dichromate(I) solution

he /oltmeter shows reading. After a few minutes2 solution at side and C side

of the u tube shows changes.

a) What is the function of dilute sul%huric acid?

JJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJ

[1 .]

b) ;tate the changes of colour in(i) Iron(II) sul%hate solution


13

Acidicfied %otassiumdichromate(I) solution

V

X Y

Iron(II) sul%hate solution

"ilute sul%huric acid



(ii) Acidicfied %otassium dichromate(I) solution


[2 .]

c) 6otassium dichromate(I) solution contains %otassium2@= ion and

dichromate(I)2!r $#5$> ion. What is the oxidation number of chromium in

dichromate(I)2 !r $#5$> ion?

JJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJ

[1 .]

14



$. he diagram below shows the set>u% of the a%%aratus used to in/estigate a

redox reaction.

est tube 6 is filled with $ cm& of %otassium bromide while test tube D is filled

with $ cm& of %otassium iodide solution. A few dro%s of chlorine water is dro%%ed

into both of the test tubes and sha9ed.

a) ;tate one obser/ation for the ex%eriment.


[1 .]

b) A little of %roduct in test tube D was mixed with tetra chloromethane

liuid. he mixture was sha9en

(i) What is the colour of tetra chloromethane layer after the mixture wassha9en?


[1 .]

15

Potassium

bromide solution

Chlorine

water

Potassium iodide

solution

Chlorinewater

P Q



(ii) Write an ionic euation to re%resent the reaction.


[1 .]

c) Write the changes in the oxidation number of chlorine in both test tubes.


[1 .]

d) 7ame one substance that can re%lace chlorine water in this ex%eriment

and state the obser/ation.



[2 .]

e) ransfer of electron at a distance is also a redox reaction. Cou are gi/en

%otassium bromide solution2 chlorine water2 %otassium nitrate solution

and related a%%aratus. "raw the set>u% of the a%%aratus diagram for the

ex%eriment.

[2 .]

16



&. he diagram shows an ex%eriment to in/estigate redox reaction for three

elements2 2 C and 'inc. is in %owder form located between calcium and

aluminium where C is blac9 %owder and a non metal.

his results are recorded as shown below.

+lements

#bser/ation

"uring 0eating After 0eating

;hining flame KKKKKKKKK.........

C Bright flame 7o residue'inc ery Bright glow KKKKKKKKKKK.

a) What is the function of %otassium manganate((II) in the ex%eriment?

JJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJ

[1 .]

b) Which one need to be heated first to get a %erfect %roduct2 metal %owder or

%otassium manganate(II) ?

JJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJ

[1 .]

c) ;tate the elements that re%resent by and C ?

(i) LJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJ

(ii) CL JJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJ

[2 .]

d) ;tate obser/ation for and 'inc after being heated and when cooled.

17

0eat

6otassiummanganate(II)

Glass wool

Y !in"



(i) L JJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJ

(ii) 'inc L JJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJ

[2 .]

e) Residue from decom%osition of 4inc through heating %rocess is mixed

with and heated. A redox reaction occurs.

(i) Write chemical euation for the reaction.

JJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJ

(ii) ;tate the changes of oxidation number for 4inc in this reaction

JJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJ

[2 .]

(iii) rom the abo/e euation2 determine the oxidising agent and

reducing agent

#xidising agent

LJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJ

Reducing agent

LJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJ

[2 .]

. he diagram shows the set u% of the a%%aratus used to electrolised concentrated

sodium chloride solution with carbon electrodes.

18



[1 .]

d) he gas released at electrode D is reacted with oxygen.

(i) Write the euation in/ol/ed.


[1 .]

(ii) rom the euation2 determine whether this reaction is a redox reaction or

not base on the electron transfer.


[1 .]

e) he gas released at electrode is %assed through the test tube containing

%otassium iodide.

(i) Write the ionic euation for the reaction in the test tube.


[1 .]

(ii) rom the euation2 determine the oxidising agent and reducing agent for

the reaction.



[2 .]

/ECTION & : E//AY

Answer all uestions. Cou are reuired to answer this section within &< minutes.

20



1.

a) he table shows the set u% of the a%%aratus and the results of an

ex%eriment to in/estigate the effect of other metals to the rusting of iron.

+x%eriment

#bser/ation after a

few days

Iron nail rusted Iron nail is not rusted

+x%lain the abo/e results.

[ .]

b)

+x%lain the abo/e statement and draw the

set u% of the a%%aratus used

for the electro%lating %rocess

[3 .]

c) A student conducted two ex%eriments to in/estigate a redox reaction

between iron(II)2 e$= ion with bromine solution and magnesium ribbon.

21

$le"tro%latin& o' iron s%oon with "o%%er throu&h ele"trol(sis is a redo)

rea"tion

Iron nail

!o%%er metal

Water

Iron nail

agnesium ribbon

Water



he table shows the set u% of the a%%aratus for +x%eriment I and

+x%eriment II.

+x%eriment I II

;et u% of the

a%%aratus

(i) !om%are obser/ations between +x%eriment I and +x%eriments II.

(ii) M#xidising agent in a reaction can also act as a reducing agent in

another reactionN

Based on +x%eriment I and +x%eriment II2 discuss this statement.

In your discussion2 you need to write ionic euations.

[14 .]

/ECTION C : E//AY (#%en Res%ond Item)

#rderL Answer the following uestions

22

Iron(II) sul%hatesolution

agnesiumribbon

Iron(II) sul%hatesolution

Bromine

water



he suggested time to answer the uestion in this section is &< minutes.

a)

+x%lain the abo/e statement. [ .]

b) (i) &0$;(g) = $07#&(a) F &;(s) = $7#(g) = 0$#(l)

(iii) 6b(7#&)$(a) = @$!#&(a) F 6b!#&(s) = $@7#&(s)

he euation in (b)(i) re%resent the redox rection and the euation (b)(ii) is not a

redox reaction. +x%lain. [3 .]

c)

"escribe an ex%eriment to %ro/e the abo/e statement by using iron(II) sul%hate

solution as the reducing agent with a named oxidising agent.

[14 .]

PAPER *

23

etals which are located near the sea will be easily corrode.

+lectricity can be %roduced from transferring of the electron in a distance



Answer all uestion

1. he diagram abo/e shows the set u% of the a%%aratus of an ex%eriment by using

four different solutions. he /oltmeter readings for all ex%eriments are shown in

the table below.

a) ;tate all the /ariables in the ex%eriment.

Res%onding /ariable L JJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJ

ani%ulated /ariable L JJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJ

ixed /ariable L JJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJ

@@<-1<O

b) ;tate the hy%othesis for the ex%eriment.

JJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJ

JJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJ

@@<-11O

24

+x%er iment II+x%eriment I

+x%eriment I+x%eriment III

V

!arbon electrodes

;olution 6

;ul%huric acid21 mol dm>&

6otassium iodidesolution2 1 mol dm>&



he diagram shows /oltmeter reading for ex%eriment I2 II2 III and I.

!om%lete the table below.

+x%eriment ;olution 6 oltmeter readingP

I 6otassium dichromate(I) solutionII !hlorine water

III Bromine water I 6otassium manganate(II) solution

@@<-<&O

c) ;tate two obser/ations from the abo/e ex%eriment not including

deflection of /oltmeter needle.



@@<-<1O

d) 6redict the /oltmeter reading if %otassium iodide solution in

ex%eriment(I) is re%laced with %otassium bromide solution.


@@<-<-O

e) Arrange solutions 6 according to descending order as oxidising agent.


@@<-<$O

25



$. An ex%eriment was conducted to determine the location of three elements2 2 C

and ' in the reacti/ity series of metal. 2 C and 4 are metals %owder. After being

heated for a while. he following obser/ations occurQ

E"e!ent Ose'5ations

26



"uring 0eating After 0eating

X Brightly burned White %owder Y aintly glowed Blac9 %owder

% airly bright burned he %owder is yellow when

hot and white when cold

a) Base on the ex%eriment results of the ex%eriment2 state the inference that

we can ma9e.


@@<-<O

b) "raw the diagram for the set>u% of a%%aratus for the abo/e ex%eriment.

@@<-<3O

c) 7ame the elements re%resented by 2 C and '.

(i) L JJJJJJJJJJJJJJJJJ

(ii) C L JJJJJJJJJJJJJJJJJ

(iii) ' L JJJJJJJJJJJJJJJJJ @@<-<8O

d) 0ow can you build a reacti/ity series of metal based on the reacti/ity of

metals with oxygen?



@@<-<:O

e) In metal extraction2 carbon is used to extract iron metal. !an we useelement C to extract iron metal ?


@@<-<5O

27



&.

28

I6 i'on is expose7 to 8ate' an7 ai'9 it 8i"" n7e'#o 'stin# p'ocess qic;"<= /o9in a'a cont'ies9 i'on pipe tat ca''ies oi" is tie7 8it !a#nesi! a# tocont'o" it 6'o! n7e'#oin# 'stin# p'ocess=



Refer to the abo/e situation2 %lan a laboratory ex%eriment to show that

magnesium can control rusting %rocess on iron.

Cour ex%eriment %lanning should consist the following matter.

(i) Aim of ex%erimentP 6roblem statement

(ii) All the /ariables

(iii) 0y%othesis

(i/) ,ist of a%%aratus and materials

(/) 6rocedure

(/i) abulation of data

(11)oxidation and reduction

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