IB Chem Redox Reaction SL

Which statement is correct?

• Oxidation involves loss of electrons and a decrease in oxidation state.

• Oxidation involves gain of electrons and an increase in oxidation state.

• Reduction involves loss of electrons and an increase in oxidation state.

• Reduction involves gain of electrons and a decrease in oxidation state.

The oxidation number of chromium is the same in all the following compounds except

• Cr(OH)₃

• Cr₂O₃

• Cr₂(SO₄)₃

• CrO₃

Magnesium is a more reactive metal than copper. Which is the strongest oxidizing agent?

• Mg

• Mg²⁺

• Cu

• Cu²⁺

Which processes occur during the electrolysis of molten sodium chloride?

I. Sodium and chloride ions move through the electrolyte.

II. Electrons move through the external circuit.

III. Oxidation takes place at the positive electrode (anode).

• I and II only

• I and III only

• II and III only

• I, II and III

What happens to the Cr³⁺(aq) ion when it is converted to CrO₄^2–(aq)?

• Its oxidation number decreases and it undergoes reduction.

• Its oxidation number decreases and it undergoes oxidation.

• Its oxidation number increases and it undergoes reduction.

• Its oxidation number increases and it undergoes oxidation.

The following reactions are spontaneous as written.

Fe(s) + Cd²⁺(aq) → Fe²⁺(aq) + Cd(s)

Cd(s) + Sn²⁺(aq) → Cd²⁺(aq) + Sn(s)

Sn(s) + Pb²⁺(aq) → Sn2+(aq) + Pb(s)

Which of the following pairs will react spontaneously?

I. Sn(s) + Fe²⁺(aq)

II. Cd(s) + Pb²⁺(aq)

III. Fe(s) + Pb²⁺(aq)

• I only

• II only

• III only

• II and III only

Consider the following reaction.

H₂SO₃(aq) + Sn⁴⁺(aq) + H₂O(l) → Sn²⁺(aq) + HSO₄^–(aq) + 3H⁺(aq)

Which statement is correct?

• H₂SO₃ is the reducing agent because it undergoes reduction.

• H₂SO₃ is the reducing agent because it undergoes oxidation.

• Sn⁴⁺ is the oxidizing agent because it undergoes oxidation.

• Sn⁴⁺ is the reducing agent because it undergoes oxidation.

In which change does oxidation occur?

• CH₃CHO → CH₃CH₂OH

• CrO₄^2–→ Cr₂O₇^2–

• SO₄^2–→ SO₃^2–

• NO₂^– → NO₃^–

A voltaic cell is made from copper and zinc half-cells. The equation for the reaction occurring in the cell is

Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s)

Which statement is correct when the cell produces electricity?

• Electrons are lost from zinc atoms.

• The mass of the copper electrode decreases.

• Electrons flow from the copper half-cell to the zinc half-cell.

• Negative ions flow through the salt bridge from the zinc half-cell to the copper half-cell.

What are the oxidation numbers of the elements in sulfuric acid, H2SO4?

• O: -2, S: +6, H: +1

• O: -2, S: +4, H: +1

• O: +4, S: +1, H: +2

• O: -8, S: +6, H: +2