Redox Reactions NDA Questions

NDA Chemistry

Redox Reactions MCQ Questions


1.
In terms of the classical (oxygen-based) concept, a reaction such as 2Mg(s) + O2(g) -> 2MgO(s) is classified as an oxidation reaction because magnesium:
A.
Gains oxygen
B.
Loses hydrogen
C.
Loses oxygen
D.
Gains hydrogen
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ANSWER :
A. Gains oxygen
2.
In the classical sense, reduction was originally understood mainly as the process of converting a metal oxide into the free metal, historically observed in reactions such as:
A.
The reduction of metal oxides (e.g., of copper or lead) to the metal by heating with carbon or hydrogen
B.
The dissolving of salt in water
C.
The rusting of iron
D.
The evaporation of water
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ANSWER :
A. The reduction of metal oxides (e.g., of copper or lead) to the metal by heating with carbon or hydrogen
3.
In the reaction CuO + H2 -> Cu + H2O, identify which substance is reduced according to the classical concept:
A.
Hydrogen, since it gains oxygen
B.
Copper oxide (CuO), since it loses oxygen to form copper metal
C.
None of the substances undergo reduction
D.
Water, since it is a product
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ANSWER :
B. Copper oxide (CuO), since it loses oxygen to form copper metal
4.
According to the classical concept, the removal of hydrogen from a compound (dehydrogenation) is regarded as an example of:
A.
Oxidation
B.
Hydrolysis
C.
Reduction
D.
Neutralisation
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ANSWER :
A. Oxidation
5.
The classical concept of oxidation and reduction (based purely on oxygen/hydrogen transfer) was found to have limitations mainly because it:
A.
Applied only to organic compounds
B.
Was applicable only to gaseous reactions
C.
Could explain all types of chemical reactions without exception
D.
Could not explain redox changes that do not involve oxygen or hydrogen at all, such as reactions between chlorine and metals
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ANSWER :
D. Could not explain redox changes that do not involve oxygen or hydrogen at all, such as reactions between chlorine and metals
6.
The modern definition of oxidation, based on electron transfer, states that oxidation is a process that involves:
A.
A net gain of one or more electrons by a species
B.
A net loss of one or more electrons by a species
C.
A gain of a neutron
D.
No change in the number of electrons
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ANSWER :
B. A net loss of one or more electrons by a species