THE ANSWER OF REDOX REACTION QUIZ Part I

QUIZ FOR YOU 

1.      According to the old concept, the correct equation of a reduction is ….

a.       C + O₂ à CO₂                 

b.      H₂ + Cl₂ à 2 HCl

c.       Cu + Cl₂ à CuCl₂          

d.      2 Cu + O₂ à 2 CuO

e.       CuO + H₂  à Cu + H₂O  

     

2.      Based on the old concept, the correct oxidation reaction is ….

a.       Fe₂O₃(s)+3CO(g)à2Fe(l)+3CO₂(g)

b.      CuO(s)+ H₂(g)àCu(s) + H₂O(g)

c.       ZnO(s) + C(s) à Zn(s) + CO(g)

d.      Cr₂O₃(s)+3C(s)à2Cr(s)+3CO(g)

e.       2Pb(s) + O₂(g) à 2PbO(s)

3.      Until now, the old concept of oxida-tion and reduction reactions is still used, for example in the discussion of ….

a.       solution                            

b.      metabolism

c.       electrochemistry               

d.      organic compound           

e.       inorganic compound

4.      One of the following processes which doesn’t involve a redox reaction is ….

a.       photosynthesis

b.      burning of gasoline

c.       evaporation of water        

d.      human respiration

e.       preparation of metals from their ores

5.      The correct statement about the new concept of oxidation reaction is ….

a.       there is a transfer of electron

b.      decreasing an oxidation number

c.       changing in oxidation number

d.      a substance or an ion loses electrons     

e.       a substance which gains electrons, so its charge increases

6.      A transfer electron will happen when

a.       there are ions

b.      the molecules have different charges

c.       an electron valence relative small

d.      different oxidation number

e.       metal reacts with another substance

7.      When metallic ions are reduced, they can turn into its ….

a.       element                 

b.      compound

c.       cation                   

d.      molecule

e.       particle

8.      If the Fe³⁺ ion gained electrons and it would become an iron atom, the correct equation is ….

a.       Fe³⁺  +  e-    à  Fe²⁺

b.      Fe³⁺  +  2e-  à  Fe⁺

c.       Fe³⁺  +  3e-  à  Fe           

d.      Fe³⁺  à  Fe  + 3e-

e.       Fe³⁺  à  Fe⁺  + 2e-

9.      A substance undergoes oxidation if it ….

a.       gains oxygen, 2Pb(s) + O₂(g)à 2PbO(s)

b.      loses oxygen, 2Cu(s) + O₂(g) à 2CuO(s)

c.       loses hydrogen, O₂(g) + 2H₂(g)à 2H₂O(g)

d.      gains electrons, Na⁺(l)+eàNa(l)

e.       loses electrons,Cu²⁺(aq)+2eàCu(s)

10.  In an ionic reaction between magnesium and sulfur, the wrong answer is ….

a.       magnesium will reduced

b.      sulfur will oxidized

c.       sulfur as a reducing agent

d.      magnesium will lose its electrons to sulfur

e.       there is a transferring from sulfur to magnesium

11.  One of the reactions below carbon is oxidized and oxygen is reduced. The correct answer is ….

a.       2CO  à C + CO₂ 

b.      C   +  O₂  à  CO₂                        

c.       C   +  CO₂  à  2CO

d.      FeO   +  C  à  Fe + CO

e.       Fe₂O₃  +  CO  à  Fe + CO₂

12.  A reducing agent brings about the reduction of a substance. In the reaction it is always oxidized. The substances below are common reducing agents, except ….

a.       H₂                          d. C

b.      CO                                    e. CO₂   

c.       SO₂

13.  A substance undergoes reduction if it :

(1)   loses oxygen

(2)   gains hydrogen

(3)   gains electrons

The correct answer(s) is (are) ….

a.   (1)

b.      (2)

c.       (3)

d.      (1) and (2)

e.       (1), (2), and (3)                 

14.  When metallic ions are reduced they turn from the ion into its elemental state. For example if the M²⁺ ion gained 2 electrons it would become its atom. The answer which unrelated(s) to this information is (are) ….

(1) Fe³⁺  +  3e  à  Fe

(2) Cr³⁺  +  3e  à  Cr

(3) Fe²⁺  +  2e  à  Fe

(4)   Cl₂    +  2e  à  2Cl^-

(5)   Cr³⁺  +  e  à  Cr²⁺

a.       (1) and (2)

b.      (1) and (3)

c.       (4) and (5)            

d.      (1), (2), and (5)

e.       (3), (4), and (5)

15.  If iron is in contact with a more active metal such as zinc, the zinc will reduce the iron to return it to its elemental state. This occurs by the following reaction ….

a.       Fe  +  3 Zn  à   2Fe  +  3 Zn

b.      2Fe³⁺  +  3Zn à 3Fe   +  3Zn²⁺   

c.       2Fe³⁺  +  3Zn  à  3Fe²⁺ +  3Zn²⁺

d.      3Fe   +  3Zn²⁺  à 2Fe³⁺  +  3 Zn 

e.       3Fe²⁺  +  3Zn  à  2Fe³⁺  + 3Zn²⁺

16.  The new concept of oxidation and reduction reactions concerns with the concept of ….

a.       an oxidation number        

b.      an oxygen’s property

c.       an electron valency          

d.      an ionic charge

e.       a neutral compound

17.  The oxidation number of hydrogen is always +1, unless it is part of a metal hydride. The hydrogen ion which has an oxidation number of -1 is ….

a.       H₂O₂                                  d. CaH₂

b.      H₂O                                   e. CH₄

c.       HCl

18.  The oxidation number of oxygen in a compound is always -2, except for peroxides The oxidation number of oxygen in barium peroxide, BaO₂ is ….

a.       +2                          d.  -1               

b.      +1                          e. -2

c.       0

19.  In which one of the following particles does nitrogen have the highest oxidation number?

a. Li₃N                         d. NH₄⁺

b. N₂O                         e. NO₃^-            

20.  In which one of the following does iodine have oxidation number of +1 ?

            a. NaIO₄                      c. IO₃^-

            b. I₃^-                             d. OI^-              

21.  The oxidation’s number of S ( sulfur ) in pirosulfate acid compound ( H₂S₂O₇ ) is ….

            a. +4

            b. +6               

c. +8

d. +10

            e. +12

22.  The highest oxidation number of sulfur in the following cases is ….

a.       H₂S    

b.      H₂SO₄      

c.       CS₂     

d.      S₈     

e.       Na₂SO₃

23.  The statements below correct, except ….

a.       oxidation number of an element which is uncombined is zero

b.      in any neutral compound the sum of the oxidation numbers is zero

c.       for polyatomic ions the sum of the oxidation numbers of each of its elements must equal the charge on the ion

d.      the oxidation number of a monoatomic ion is equal to its charge

e.       the phosphate ion, PO₄^3- has a minus three charge, its oxidation number is -3                

24.  In H₂PO₄^-, the oxidation number of fosfor is …

a.       -5                           d. -3                            

b.      0                            e. 3

c.       5

               

25.  The oxidation number of sulfur in sodium sulphate, Na₂SO₄ is ….

a.       0                            d. +4

b.      +1                          e. +6               

c.       +2

26.  The minimum oxidation number of chlorine in the species below is ….

a.       ClO₂^-

b.      NaCl                     

c.       NaClO₄                

d.      Cl₂O₅

e.       Cl₂

27.  The maximum oxidation number of Mn is ….

a.       MnO₂                   

b.      MnSO₄

c.       Mn₂O₃                  

d.      KMnO₄                

e.       K₂MnO₄