MCQs — Electrochemistry

Practice questions for Chemistry.

Question 41

Why does the oxidation state of a simple monoatomic ion equal its actual charge?

A. Because the charge directly reflects the number of electrons the atom has gained or lost relative to its neutral atom, which is exactly what oxidation state measures

B. Because oxidation state and charge are entirely unrelated coincidences

C. Because monoatomic ions never actually carry a real charge

D. Because this rule only applies to noble gases

Question 42

According to standard oxidation-state patterns, elements in Group IA (alkali metals) typically have an oxidation state of:

A. -1

B. +1

C. +2

D. +3

Question 43

According to standard oxidation-state patterns, elements in Group IIA (alkaline earth metals) typically have an oxidation state of:

A. +1

B. +2

C. -2

D. +3

Question 44

According to standard oxidation-state patterns, elements in Group IIIA typically have an oxidation state of:

A. +1

B. +2

C. +3

D. -3

Question 45

Hydrogen typically has an oxidation state of +1 in most compounds, except in metal hydrides, where its oxidation state is instead:

A. 0

B. -1

C. +2

D. -2

Question 46

According to standard oxidation-state patterns, elements in Group VIIA (the halogens) typically have an oxidation state of:

A. +1

B. -1

C. +2

D. 0

Question 47

Oxygen typically has an oxidation state of -2, except in peroxides and in OF2, where its oxidation state differs. This shows that:

A. Most oxidation-state patterns are common tendencies with specific, well-defined exceptions, rather than absolute, unbreakable rules

B. Oxygen never actually has a fixed oxidation state in any compound

C. Peroxides do not actually contain oxygen

D. This exception applies to every single oxygen-containing compound

Question 48

In the sulfate ion (SO4^2-), applying the rule that the oxidation states of atoms in a polyatomic ion must sum to the ion's overall charge, the oxidation state of sulfur plus four times oxygen's oxidation state must equal:

A. Zero

B. -2 (the charge on the sulfate ion)

C. +2

D. -4

Question 49

In the neutral compound HCl, applying the rule that oxidation numbers in a neutral compound sum to zero, if hydrogen is +1, then chlorine must be:

A. +1

B. -1

C. 0

D. -2

Question 50

In the neutral compound CO2, applying the rule that oxidation numbers in a neutral compound sum to zero, if each oxygen atom is -2, then carbon must be:

A. +2

B. -2

C. +4

D. -4

Question 51

The oxidation number of a monoatomic ion is equal to:

A. Its atomic mass

B. Its charge

C. The number of neutrons it contains

D. Zero, always

Question 52

Sodium (Na) loses one electron to form Na+. What is the oxidation number of sodium in this ion?

A. -1

B. 0

C. +1

D. +2

Question 53

Chlorine gains one electron to form Cl-. What is the oxidation number of chlorine in this ion?

A. +1

B. 0

C. -1

D. -2

Question 54

The oxidation number of a monoatomic ion always equals the number of electrons the atom has lost or gained because:

A. A monoatomic ion is formed only by the gain or loss of electrons from a single atom, so its resulting charge directly reflects that electron change

B. Oxidation number and charge are unrelated for monoatomic ions

C. Monoatomic ions never actually carry any charge

D. This is true only for negatively charged ions

Question 55

The rule that a monoatomic ion's oxidation number equals its charge follows directly from the general oxidation-state rule that:

A. The oxidation state of a free element is always zero

B. In simple ions, the oxidation state is the same as the ion's charge

C. The sum of oxidation states in a neutral compound is zero

D. Oxygen's oxidation state is usually -2

Question 56

In the carbonate ion (CO3^2-), given that oxygen has an oxidation number of -2, the total contributed by the three oxygen atoms is:

A. -2

B. -4

C. -6

D. -8

Question 57

Continuing from the carbonate ion (CO3^2-) example, if the overall ion charge is -2 and the three oxygen atoms contribute -6, then carbon's oxidation number must be:

A. +2

B. +4

C. -4

D. -2

Question 58

The oxidation number of oxygen in a polyatomic ion generally follows the standard pattern of:

A. +2, with no exceptions

B. -2, except in special cases such as peroxides

C. 0, always

D. Equal to the ion's overall charge

Question 59

The general method for finding the oxidation number of one atom in a polyatomic ion, when the oxidation numbers of the other atoms are already known, is to:

A. Add the ion's overall charge to the known total contribution of the other atoms

B. Subtract the known total contribution of the other atoms from the ion's overall charge

C. Multiply the ion's charge by the number of atoms present

D. Ignore the ion's overall charge entirely

Question 60

In the ammonium ion (NH4+), given that hydrogen has an oxidation number of +1, the total contributed by the four hydrogen atoms is:

A. +1

B. +2

C. +4

D. +8

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