Oxidation and Reduction Test

What is the half-reaction for lead (II) being oxidized to lead (IV)?

Pb²⁺ → Pb⁴⁺ + 2e⁻

In the reaction Al° + Cr³⁺ yields Al³⁺ + Cr, what is the reducing agent?

Al°

What does a redox reaction always involve?

A change in oxidation number.

Which half-reaction correctly represents reduction?

Mn⁷⁺ + 3e⁻ → Mn⁴⁺

In the reaction AlO + Cr³⁺ yields Al³⁺ + Cr, what is the reducing agent?

Al°

What is the algebraic sum of the oxidation numbers of the atoms in a compound?

Always zero.

Which of the following is a redox reaction?

2 H₂O → 2 H₂ + O₂.

In the reaction 2 Na + 2 H₂O → 2 Na⁺ + 2 OH⁻ + H₂, which substance has been oxidized?

Na.

What is the coefficient of Cr³⁺ (aq) in the balanced equation C³⁺ (aq) + 3 Mn (s) → Mn²⁺ (aq) + Cr (s)?

2.

What are the oxidation numbers in the ion SO₃²⁻?

S = +4, O = -2.

In a redox reaction, how many electrons must be lost or gained by C when CO is changed to CO₂?

Two electrons lost.

If the element 'X' forms the oxides XO and X₂O₃, what are the oxidation numbers of the element X?

+2 and +3.

In which substance is the oxidation number of nitrogen zero?

N₂.

What are the oxidation numbers in the compound H₂O₂?

H = +1, O = -1.

What is the most common oxidation number of combined oxygen?

-2.

What is the balanced redox reaction for Sn + Ag⁺?

Sn + Ag⁺ → Sn²⁺ + Ag.

If species change their oxidation numbers, what is the process called?

Oxidation-reduction reaction.

What are the oxidation numbers in the compound NO₂?

N = +4, O = -2.

In which compound does oxygen have a positive oxidation number?

OF₂.

Which redox equation is correctly balanced?

Br₂ + Hg → Hg²⁺ + 2 Br⁻.

In the redox reaction MnO₄⁻ changing to MnO₄²⁻, how many electrons must be gained by Mn?

One electron gained.

What is another name for an oxidation-reduction reaction?

Redox reaction.

What change occurs when an Sn²⁺ ion is oxidized?

Two electrons are lost.

As an S²⁻ ion is oxidized to an S° atom, what happens to the number of protons in its nucleus?

Remains the same.

Write the half-reaction for silver(I) being reduced to a silver atom.

Ag⁺ + e⁻ → Ag.

In the redox reaction MnO₄ changing to Mn²⁺, how many electrons are gained by Mn?

Five electrons gained.

What is the oxidation number of a monoatomic ion?

Equal to its charge.

In the reaction magnesium and oxygen yields magnesium oxide, which element is being reduced?

Oxygen.

Is the redox equation H₂ + O₂ → 2 H₂O correctly balanced?

Correctly balanced for number of atoms but NOT for charge.

Is the redox equation MnO₄⁻ + 4 CO + H⁺ → 4 CO²⁺ + Mn²⁺ + 4 H₂O correctly balanced?

Correctly balanced.

In the compound Na₂HPO₄, which element has a negative oxidation number?

O.

Is the redox equation 4 H⁺ + N₂ → NH₄⁺ + N correctly balanced?

Correctly balanced for number of atoms but NOT for charge.

What are the oxidation numbers in the compound H₃O₄?

H = +1, P = +5, O = -2.

What is the oxidation number of carbon in NaHCO₃?

+4.