Reduction worksheet

In terms of chemistry, Reduction means the process of adding hydrogen or removing oxygen from a compound in a chemical reaction.

In this article you can find some question related to oxidation and reduction with their answers.


1. Chlorine is in +1 oxidation state in
(a)    HCl

(b)   HClO_4

(c)    ICl

(d)   Cl_2O


2.  In which of the following reactions there is no change in valency?

(a)    4KClO_3 \to 3KClO_4 + KCl

(b)   HBr + AgNo_3 \to AgBr + HNO_3

(c)    H_2 + Br_2 \to 2HBr

(d)   BaO + O_2 \to 2BaO_2


3. Which of the following reaction involves oxidation and reduction?

(a)    NaBr + HCl \to NaCl + HBr

(b)   HBr + AgNO_3 \to AgBr + HNO_3

(c)    H_2 + Br_2 \to HBr

(d)   Na_2O + H_2SO_4 \to Na_2SO_4 + H_2O


4. In which of the following reactions, has underlined substance been reduced?

(a)    CO + \underset{-}{CuO} \to CO_2 +Cu

(b)   \underset{-}{Cu}O + 2HCl \to CuCl_2 + H_2O

(c)    \text{steam} + \text{iron} \to H_2 + \text{iron oxide}

(d)   hydrogen + iron oxide = water + iron


5. The most common oxidation state of an element is -2. The number of electrons present in its outermost sheel is:

(a)    2

(b)   4

(c)    6

(d)   8


6. Oxidation of thiosulphate ion by iodine gives

(a)    SO_3^=

(b)   SO_4^=

(c)    S_4O_6^=

(d)   S_2O_3^=


7. The oxidation state of nitrogen in N_3His:

(a)    +1/2

(b)   +3

(c)    -1

(d)   -1/3


8. The oxidation number and valency of sulphur in the sulphur molecule (S_3) are respectively:

(a)    0 and 2

(b)   6 and 8

(c)    0 and 8

(d)   6 and 2


9. Oxidation state of oxygen atom in potassium peroxide is:

(a)    Zero

(b)   -1/2

(c)    -1

(d)   -2


10. In which of the following compounds transition metal is in oxidation state zero?

(a)    [CO(NH_3)_6]Cl_2

(b)   [Fe(H_2O)_5SO_4

(c)    Ni(CO)_4

(d)   [Fe(H_2O)_3](OH)_2


11. In which one of the following changes there are transfer of five electrons?

(a)    MnO^-_4 \to Mn^{++}

(b)   CrO^{2-}_4 \to Cr^{3+}

(c)    MnO^{2-}_4 \to MnO_2

(d)   Cr_2O^{2-}_7 \to 2Cr^{3+}


12. The oxidation number of nitrogen in NH_2OH  is

(a)    +1

(b)   -1

(c)    -3

(d)   -2


13. In which of the following reaction is hydrogen peroxide a reducing agent?

(a)    2FeCl_2 + 2HCl + H_2O_2 \to 2FeCl_2 + 2H_2O

(b)   Cl_2 + H_2O_2 \to 2HCl + O_2

(c)    2HI + H_2O_2 \to 2H_2O + I_2

(d)   H_2SO_3 + H_2O_2 \to H_2SO_4 + H_2O


14. The process in which oxidation number increases is known as:

(a)    Oxidation

(b)   Reduction

(c)    auto oxidation

(d)   none of the above


15. The oxidation states of phosphorous vary from:

(a)    -3 to +5

(b)   -1 to +1

(c)    -3 to +3

(d)   -5 to + 1


16. In the reaction,

Cr_2O^{2-}_7 + 14H^+ + 6I^- \to 2Cr^{3+} + 3H_2O +3I_2 Which element is reduced?

(a)    Cr

(b)   H

(c)    O

(d)   I


17. In which of the following reaction, there is no change in valency?

(a)    SO_2 + 2H_2S \to 2H_2O + 3S

(b)   2Na + O_2 \to Na_2O_2

(c)    Na_2O_2 + H_2SO_4 \to Na_2SO_4 + H_2O_2

(d)   4KClO_3 \to 3KClO_4 + KCl


18. The compound that can work both as oxidizing and reducing agent is:

(a)    KMnO_4

(b)   H_2O_2

(c)    BaO_2

(d)   K_2Cr_2O_7


19. In the reaction,

Cl_2 + OH^- \to Cl^- + ClO^-_3 + H_2O Chlorine is:

(a)    Oxidized

(b)   Reduced

(c)    oxidized as well as reduced

(d)   neither oxidized not reduced


20. Oxidation number of P in KH_2PO2 is:

(a)    +1

(b)   +3

(c)    +5

(d)   -3


21. The anhydride of hypochlorous acid is:

(a)    ClO_3

(b)   ClO_3

(c)    Cl_2O_5

(d)   Cl_2O


22. In the presence of dilute H_2SO_4, the equivalent weight of KMnO_4 is:

(a)    1 / 5 of its molecular weight

(b)   1/6 of its molecular weight

(c)    1 / 10 of its molecular weight

(d)   1 / 2 of its molecular weight


23. The strongest reducing agent is:

(a)    HNO_2

(b)   H_2S

(c)    H_2SO_3

(d)   SnCl_2


24. In the reaction,

2KI + Br_2 \to 2KBr + I_2 The oxidizing agent is:

(a)    KI

(b)   Br_2

(c)    KBr

(d)   none of these


25. In the reaction,

2FeCl_2 + Cl_2 \to 2FeCl_3 the equivalent weight of FeCl_2 will be

(a)    equal to its molecular weight

(b)   half of its molecular weight

(c)    1 / 3 rd of its molecular weight

(d)   1/6th  of its molecular weight



1.(d)       2. (b)        3. (c)       4. (a)        5. (c)

6. (c)      7. (d)        8. (a)       9. (b)        10. (c)

11. (a)     12. (b)     13. (b)      14. (a)      15. (a)

16. (a)    17. (c)     18. (b)      19. (c)      20. (a)

21. (d)     22. (a)    23. (b)     24. (b)     25. (a)

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