Electrochemistry formative quiz

What is the oxidation state of C in methane?

• +4

• -4

• +1

• -1

Which compound is the reducing agent in

Mg(s) + 2HCl(aq) → H₂ (g) + MgCl₂ (aq) ?

• Mg (s)

• 2 HCl

• H₂

• MgCl₂

In which compound does nitrogen have an oxidation state of +3?

• NO

• N₂O

• NO₂^-

• NO₃^-

Represent a voltaic cell that shows a reaction between magnesium and nickel electrodes.

Indicate the following elements in your diagram:
1) which electrode is the anode and which is the cathode as well as their respective charges (symbols);
2) in which direction electrons flow and
3) in which directions ions flow in solution as well as in the salt bridge.

Use a potassium chloride salt bridge in your voltaic cell. Ignore colours of ions in solution (graph was borrowed from another question).

Answer explanation

See image below of complete circuit.

Explain what changes in an electrolytic cell compared to a voltaic cell? Select all that apply.

• The cell requires a battery for the electrons to flow in the circuit.

• The charge of the anode is negative and the charge of the cathode is positive.

• The charge of the anode is positive and the charge of the cathode is negative.

• The electrons flow from the cathode to the anode.

• The cell potential can be measured using a voltmeter.

Balance the following equation in an acidic medium.

Answer explanation

See steps below to correct your work! Final answer should be:
Cr₂O₇^2- _(aq) + 14H⁺_(aq) + 6I^- _(aq) → 3I_{2 (s)} +  2Cr³⁺ _(aq) + 7 H₂O _(l)