MCQs — Electrochemistry

Practice questions for Chemistry.

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Question 21

In the same net ionic equation (Cu2+ + Zn -> Cu + Zn2+), the zinc (Zn) atom is:

A. Gaining 2 electrons to form Zn2+, so it is being reduced

B. Losing 2 electrons to form Zn2+, so it is being oxidized

C. Remaining as a spectator

D. Undergoing no change in charge

Question 22

An increase in an atom's oxidation number during a reaction corresponds to:

A. Reduction

B. Oxidation

C. No chemical change at all

D. A spectator process

Question 23

A decrease in an atom's oxidation number during a reaction corresponds to:

A. Oxidation

B. Reduction

C. No chemical change at all

D. A spectator process

Question 24

In the reaction 2Ca + O2 -> 2CaO, each calcium atom loses two electrons to form Ca2+. Based on this electron transfer, calcium is being:

A. Reduced

B. Oxidized

C. Left unchanged

D. Neither oxidized nor reduced

Question 25

In the same reaction (2Ca + O2 -> 2CaO), each oxygen atom gains two electrons to form O2-. Based on this electron transfer, oxygen is being:

A. Oxidized

B. Reduced

C. Left unchanged

D. Converted into a spectator species

Question 26

In the reaction 4Na + O2 -> 2Na2O, sodium metal is:

A. Reduced, since it gains electrons to form Na+ ions

B. Oxidized, since it loses electrons to form Na+ ions

C. Unaffected by the reaction

D. Acting only as a spectator

Question 27

In the reaction 2Al + 3Cl2 -> 2AlCl3, aluminium metal is:

A. Oxidized, since it loses electrons to form Al3+ ions

B. Reduced, since it gains electrons to form Al3+ ions

C. Left completely unchanged

D. Acting as an oxidizing agent

Question 28

In the reaction Mg + Cl2 -> MgCl2, chlorine is:

A. Oxidized, since it loses electrons to form Cl- ions

B. Reduced, since it gains electrons to form Cl- ions

C. Unaffected by the reaction

D. Acting as a reducing agent

Question 29

Oxidation and reduction always occur together in the same reaction because:

A. Electrons lost by one substance (oxidation) must be gained by another substance (reduction); electron transfer cannot happen in isolation

B. They are simply two unrelated names for the same process

C. One always happens well before the other, in a separate step

D. Only metals can undergo either oxidation or reduction

Question 30

Since Group IIA metals characteristically form M2+ cations and Group VIA non-metals characteristically form X2- anions, in a reaction between a Group IIA metal and a Group VIA non-metal, the metal will always be:

A. Reduced, while the non-metal is oxidized

B. Oxidized (losing 2 electrons), while the non-metal is reduced (gaining 2 electrons)

C. Unaffected, while only the non-metal changes

D. Acting purely as a spectator

Question 31

Oxidation state (oxidation number) is defined as:

A. The physical mass of an atom

B. The number of charges an atom will have in a molecule or compound

C. The number of neutrons in an atom's nucleus

D. The boiling point of a compound

Question 32

An element that shows an increase in oxidation number over the course of a reaction is being:

A. Reduced

B. Oxidized

C. Neutralized

D. Left as a spectator

Question 33

An element that shows a decrease in oxidation number over the course of a reaction is being:

A. Oxidized

B. Reduced

C. Neutralized

D. Left as a spectator

Question 34

In the reaction H2 + Cl2 -> 2HCl, chlorine's oxidation state changes from 0 to -1. Is chlorine being reduced?

A. No, this change indicates oxidation

B. Yes, since a decrease in oxidation number indicates reduction

C. No change in oxidation state has actually occurred

D. It is impossible to tell without more information

Question 35

In the same reaction (H2 + Cl2 -> 2HCl), hydrogen's oxidation state changes from 0 to +1. Is hydrogen being oxidized?

A. Yes, since an increase in oxidation number indicates oxidation

B. No, this change indicates reduction

C. No change in oxidation state has actually occurred

D. It is impossible to tell without more information

Question 36

According to the oxidation-state rules, the oxidation state of any element in its free, uncombined form (such as Zn metal, Na metal, or H in H2 gas) is always:

A. +1

B. -1

C. Zero

D. Variable and unpredictable

Question 37

According to the oxidation-state rules, in a simple monoatomic ion, the oxidation state is:

A. Always zero, regardless of charge

B. The same as the ion's actual charge

C. Always exactly double the ion's charge

D. Unrelated to the ion's charge

Question 38

According to the oxidation-state rules, in a polyatomic (complex) ion, the sum of the oxidation states of all the atoms present equals:

A. Always zero

B. The overall charge on the ion

C. The atomic mass of the ion

D. The number of atoms in the ion

Question 39

According to the oxidation-state rules, the algebraic sum of the oxidation numbers of all the atoms in a neutral molecule or compound is always:

A. Equal to the number of atoms present

B. Zero

C. Equal to the molecular mass

D. A negative number

Question 40

Why is the oxidation state of an atom in its free, uncombined elemental form always zero?

A. Because the atom has not gained, lost, or shared any electrons relative to its neutral state, so it carries no net charge

B. Because free elements never actually exist in nature

C. Because oxidation states only apply to compounds, never to elements

D. Because all elements are identical in reactivity

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