Review of basic electrolytic cells – aqueous electrolytes

Question 1

For the ions in an ionic compound to move freely, the compound must be molten or ___ . Thus, aqueous solutions can also serve as electrolytes and can be
used in electrolytic cells. The products of the electrolysis, however, will not necessarily be the same as when the ionic compound is in the molten state since
____ itself can be electrolysed and can offer competition for the loss and gain of electrons at the electrodes.

Answer 1

aqueous

water

Question 2

You should recall the Hoffman Voltameter from UIV,
which was used to electrolyse water. It shows us that
when current is passed through water, it produced:

Answer 2

You should recall the Hoffman Voltameter from UIV,
which was used to electrolyse water. It shows us that
when current is passed through water, it produced
Hydrogen gas and oxygen gas.

Question 3

In aqueous solutions, one must consider whether water will be preferentially oxidized or reduced in place of the other species present. For this, we need the _____.

Answer 3

Standard Electrode Potential Table

Question 4

How does the SEP table work?

Answer 4

The more positive the value, the more likely the substance is to be reduced (gain electrons) or to act as an oxidizing agent. Thus, when electrons are
available at the cathode to be gained, the species with the most positive E0 value will be reduced in preference.

Question 5

We can use the E0 values to calculate the potential difference of the battery that must be used to ensure that the electrons are effectively removed and transferred from negative ions to positive ions. We make use of the following equation:

Answer 5

E0cell = E0cathode – E0anode

E0cell = E0oxidising agent – E0reducing agent

Question 6

What does a positive emf value indicate?

Answer 6

Spontaneous

Question 7

What does a negative emf value indicate?

Answer 7

Nom-spontaneous

Question 8

The SEP table is constructed based on reactions performed at standard conditions. What are these conditions?

Answer 8

These are 298K, 1 mol.dm-3 concentration of solutions and 1-atmosphere pressure (where relevant). Thus, when these conditions are changed, the Eo values quoted,
can and will change. To understand how they change, one needs to consider Le Chateliers Principle and the fact that these reactions are occurring in an equilibrium.