Redox + Electrochemistry Revision

Redox & Electrochemistry

Multiple Choice

A concentrated aqueous solution containing each of the following ions, Cl^-, SO₄^2-, Na⁺, Cu²⁺, is electrolysed using platinum electrodes.

Which row shows the ions that discharge first at the two electrodes?

• at positive electrode: Cl^-

  at negative electrode: Cu²⁺

• at positive electrode: Cl^-

  at negative electrode: Na⁺

• at positive electrode: SO₄^2-

  at negative electrode: Cu²⁺

• at positive electrode: SO₄^2-

  at negative electrode: Na⁺

Multiple Choice

Inert electrodes are used in the electrolysis of an aqueous solution containing both copper(II) sulfate and magnesium sulfate.

What will be produced at the negative electrode?

• copper

• hydrogen

• magnesium

• oxygen

Multiple Choice

Metal M can be obtained from its oxide by heating with carbon and from is aqueous chloride by electrolysis.

Which metal is M?

• copper

• lead

• silver

• sodium

Multiple Choice

The diagram shows a cell.

Which statement about the cell is correct?

• Electrons pass from the magnesium electrode to the silver electrode through the electrolyte.

• The cell shows that silver is more reactive than magnesium.

• The magnesium electrode loses electrons.

• The silver electrode is oxidised.

Multiple Choice

What is the oxidation state of oxygen in ethanol, C₂H₅OH?

• 0

• +2

• -2

• +1

Multiple Choice

Acidified KMnO₄ is used to test for _____________.

During the process, it is ____________.

• reducing agents, reduced

• oxidising agents, reduced

• oxidising agents, oxidation

• reducing agents, oxidation

Multiple Choice

In the presence of reducing agents, acidified KMnO₄ turns from _______________________.

• purple to colourless

• colourless to purple

• brown to colourless

• colourless to brown

Multiple Choice

In which reaction does the oxidation state of iron remain unchanged?

• 2Fe + 3Cl₂ --> 2FeCl₃

• 2FeCl₂ + Cl₂ --> 2FeCl₃

• Fe + 2FeCl₃ --> 3FeCl₂

• Fe₂O₃ + 6HCl --> 2FeCl₃ + 3H₂O

Multiple Choice

Chlorine reacts with aqueous sodium hydroxide in a redox reaction.

2NaOH (aq) + Cl₂ (g) --> NaClO (aq) + NaCl (aq) + H₂O (l)

Which statement about this reaction is not correct?

During the reaction

• chlorine changes from oxidation state 0 to oxidation state +1

• chlorine changes from oxidation state 0 to oxidation state -1

• hydrogen changes from oxidation state -1 to oxidation state +1

• oxygen remains in oxidation state -2

Multiple Choice

In which equations is manganese being reduced?

1) 2Mn(OH)₂ + H₂O₂ --> Mn₂O₃ + 3H₂O

2) MnO₂ + 4HCl --> MnCl₂ + Cl₂ + 2H₂O

3) MnO₄^- + 8H⁺ + 5Fe²⁺ --> 5Fe³⁺ + Mn²⁺ + 4H₂O

• 1, 2 and 3

• 1 and 2 only

• 2 and 3 only

• 3 only

Multiple Choice

In which reaction is substance X reduced?

• acidified potassium manganate(VII) is decolourised on addition to an aqueous solution of X.

• adding aqueous potassium iodide to an aqueous solution of X give a brown colour.

• X --> X²⁺ + 2e-

• XO^- + O₂ --> XO₃^-

Multiple Choice

Which product is formed at the anode when molten lead(II) bromide is electrolysed?

• lead(II) ions

• lead atoms

• bromide ions

• bromine molecules