M.C.Qs on Oxidation Number ....Unit # 10
1. Which
one is incorrect regarding oxidation?
(a)
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It involves addition of oxygen to a substance or
removal of hydrogen from a compound.
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(b)
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It
involves the loss of electron and is always accompanied by an increase in
oxidation number.
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(c)
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It always occurs at cathode.
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(d)
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All of the above.
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2. Which
one is incorrect regarding reduction?
(a)
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It involves addition of hydrogen to a substance or
removal of oxygen from oxides.
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(b)
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It
involves the gain of electron and is always accompanied by a decrease in oxidation
number.
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(c)
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It always occurs at anode.
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(d)
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All of the above.
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3. Which
one is an example of oxidation reaction?
(a)
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Cl
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+
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e-
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¾¾®
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Cl–
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(b)
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H2O
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¾¾®
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H+
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+
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(c)
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Ag+
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+
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Cl–
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¾¾®
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AgCl
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(d)
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Al
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-
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3e–
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¾¾®
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Al3+
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4. Which
one is an example of reduction reaction?
(a)
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C
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+
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O2
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¾¾¾¾®
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CO2
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(b)
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Fe3+
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¾¾¾¾®
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Fe2+
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(c)
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H2
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¾¾¾¾®
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2H+
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(d)
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Zn
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¾¾¾¾®
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Zn2+
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5. Which
one is incorrect regarding oxidizing agent?
(a)
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It provides nascent oxygen either on decomposition
or on reaction with other substance.
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(b)
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It acts as
electron acceptor.
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(c)
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It undergoes decrease in
oxidation number.
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(d)
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It always oxidizes itself.
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6. Which
one is incorrect regarding reducing agent?
(a)
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It provides nascent hydrogen either on decomposition
or on reaction with other substance.
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(b)
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It acts as
electron donor.
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(c)
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It undergoes an increase in
oxidation number.
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(d)
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It always reduces itself.
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7. Which
one of the following reactions involves oxidation and reduction?
(a)
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NaBr
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+
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HCl
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¾¾¾¾®
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NaCl
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+
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HBr
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(b)
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HBr
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+
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AgNO3
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¾¾¾¾®
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AgBr
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+
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HNO3
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(c)
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H2
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+
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Br2
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¾¾¾¾®
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2HBr
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(d)
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Na2O
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+
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H2SO4
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¾¾¾¾®
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Na2SO4
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+
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2H2O
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8. Which
one of the following is not an oxidation-reduction reaction?
(a)
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MgO
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+
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2HCl
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¾¾¾¾®
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MgCl2
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+
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H2O
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(b)
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Mg
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+
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HCl
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¾¾¾¾®
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MgCl2
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+
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H2
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(c)
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Cu
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+
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4HNO3
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¾¾¾¾®
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Cu(NO3)2
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+
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2H2O
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+
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2NO2
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(d)
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Cu
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+
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2H2SO4
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¾¾¾¾®
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CuSO4
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+
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2H2O
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+
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SO2
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9. Which
one of the following equation does not represent a redox reaction?
(a)
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Ba2+
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+
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SO42–
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¾¾¾¾®
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BaSO4
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(b)
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Br2
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+
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2I–
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¾¾¾¾®
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2Br–
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+
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I2
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(c)
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Cl2
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+
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S2–
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¾¾¾¾®
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S
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+
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2Cl–
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(d)
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Cu2+
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+
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Zn
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¾¾¾¾®
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Cu
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+
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Zn2+
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10. Which
one is incorrect regarding oxidation number?
(a)
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It shows the extent of oxidation or reduction.
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(b)
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Free
elements have zero oxidation number.
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(c)
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It may have fractional value
and it may be zero.
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(d)
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It is a number without positive or negative sign.
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11. When
oxidation number of a specie increases in a chemical reaction, the specie is
said to be:
(a)
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Oxidized
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(b)
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Reduced
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(c)
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Electrolyzed
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(d)
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Hydrolyzed
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12. The
oxidation number of an element in the free
state
(a)
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0
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(b)
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+1
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(c)
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+2
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(d)
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-1
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13. The
oxidation number of oxygen in a molecule is not -2 when it is bonded to a ……
atom.
(a)
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Ne
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(b)
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S
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(c)
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Br
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(d)
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F
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14. The
oxidation number of oxygen in OF2 is:
(a)
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+1
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(b)
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+2
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(c)
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-2
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(d)
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-1
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15. The
oxidation number of oxygen in peroxides (e.g. Na2O2, H2O2,
BaO2, and SrO2) is:
(a)
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-1
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(b)
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-1
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(c)
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- ½
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(d)
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+2
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16. The
oxidation number of oxygen in superoxides (e.g. KO2, RbO2,
and CsO2) is:
(a)
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-1
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(b)
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-2
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(c)
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- ½
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(d)
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+2
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17. The
oxidation number of hydrogen is +1 in its compounds except in:
(a)
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Covalent hydrides
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(b)
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H2O
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(c)
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Ionic hydrides
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(d)
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CH4
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18. The
oxidation number of Pt in K2PtCl6 is:
(a)
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+2
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(b)
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+4
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(c)
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+3
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(d)
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-4
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19. The
oxidation number of W in WO3 is:
(a)
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+5
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(b)
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+2
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(c)
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+3
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(d)
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+6
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20. The
oxidation number of Ni in Ni(CO)4 is:
(a)
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+5
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(b)
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+4
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(c)
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Zero
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(d)
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+3
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21. The
oxidation number of carbon in C12H22O11 is:
(a)
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+12
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(b)
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-12
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(c)
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Zero
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(d)
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+4
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22. The
oxidation number of chlorine in HClO4 is:
(a)
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+1
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(b)
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+7
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(c)
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+5
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(d)
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+3
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23. The
oxidation number of S in SO32- is:
(a)
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-4
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(b)
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+4
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(c)
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-2
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(d)
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+6
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24. The
oxidation number of S in S2O32- is:
(a)
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+2
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(b)
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+4
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(c)
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-2
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(d)
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+2.5
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25. In
which of the following substances does sulphur exhibits is highest oxidation
state?
(a)
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S8
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(b)
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SO2Cl2
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(c)
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Na2S4O6
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(d)
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Na2S2O3
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26. When
Cl– ions are converted to Cl2, the oxidation number of
chlorine increases from:
(a)
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-1 to +1
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(b)
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-1 to zero
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(c)
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-1 to -2
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(d)
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-1 to +2
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27. The
most common oxidation state of an element is -2. The number of electrons
present in its outermost shell
is:
(a)
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4
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(b)
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6
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(c)
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5
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(d)
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2
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28. Which
one of the following formulae contains nitrogen with an oxidation state of +5?
(a)
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NH4+
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(b)
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N2O5
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(c)
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NO2
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(d)
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N2O
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29. The electronic configuration of an element is 1s2,
2s2 2p5. In a chemical reaction, it is most likely to
(a)
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Donate two electrons
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(b)
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Gain one electron
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(c)
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Donate one electron
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(d)
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Gain two electrons
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30. An atom has 3 electrons in its valence shell. It
is most likely to have following oxidation state?
(a)
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-3
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(b)
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-5
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(c)
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+2
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(d)
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+3
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31. What
is the oxidation number associated of the element with oxygen in each of the
following radicals?
(i). CrO42– (ii). ClO41– (iii). PO43– (iv). PbO22–
(a)
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+6, +7, +5, +2
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(b)
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+6, +5, +5, +4
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(c)
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+2, +5, +7, +6
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(d)
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+5, +6, +2, +7
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32. What
is the oxidation number of Mn in the following compounds?
KMnO4,
K2MnO4, MnO2, MnCl2
(a)
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+7, +6, +4, +2
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(b)
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+7, +2, +6, +4
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(c)
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+6, +4, +7, +2
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(d)
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+7, +4, +6, +4
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33. What
is the oxidation number of Cl in the following compounds?
Cl2O,
HOCl, NaClO3, AuCl3, ClF
(a)
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+1, +1, +5, -1, -1
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(b)
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+1, +2, +5, -1, +1
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(c)
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+1, -1, +3, -1, +1
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(d)
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+3, +1, +5, -1, -1
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34. In
which of the following formulae contains Mn in its highest oxidation state?
(a)
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MnO2
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(b)
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MnO41–
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(c)
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MnO42-
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(d)
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Mn(OH)3
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35. In
which of the following formulae contains P in its highest oxidation state?
(a)
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P2O72–
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(b)
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P4
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(c)
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PO33–
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(d)
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PH3
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36. In
which of the following formulae contains C with oxidation state of -2?
(a)
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CO
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(b)
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Al4C3
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(c)
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C2H6O
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(d)
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HCO31–
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37. In
which of the following formulae contains C with oxidation state of +4?
(a)
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C6H12O6
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(b)
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C6H10O5
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(c)
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CO
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(d)
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None of them
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38. In
which of the following formulae contains Cr with oxidation state of +3?
(a)
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K2Cr2O7
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(b)
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H2CrO4
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(c)
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CrO3
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(d)
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None of them
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39. In
which of the following formulae contains O in its highest oxidation state?
(a)
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Na2O
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(b)
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KO2
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(c)
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OF2
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(d)
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O2F2
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40. In
the reaction; Zn + H2SO4 ¾¾¾¾®
ZnSO4 + H2,
which element is reduced?
(a)
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H
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(b)
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O
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(c)
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Zn
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(d)
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S
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41. In
the reaction; 2HBr + H2SO4 ¾¾¾¾®
SO2 + Br2
+
2H2O, which element is oxidized?
(a)
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S
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(b)
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Br
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(c)
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H
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(d)
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O
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42. In
the reaction; Zn + I2 ¾¾¾¾®
ZnI2,
which element is oxidized?
(a)
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Zinc atom
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(b)
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Zinc ion
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(c)
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Iodine atom
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(d)
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Iodide ion
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