Homework 2: Electrochemistry
- Page ID
- 2854
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True/False
- Platinum cannot be plated from solution by electrolysis.
- Reactions which are readily reversed by a small change in concentration are ones in which E is close to zero.
- All solutions of electrolytes conduct electricity.
- Electrolysis can only be performed on solutions.
- In electrolysis, the process occurring at the cathode is oxidation.
- In any cell, electrolytic or voltaic, the cathode is the negative electrode.
- An anode is a positive electrode.
- The liberation of free elements from liquids by the passage of an electric current is called neutralization.
- Electrolysis can be carried out in molten salts as well as in water solutions.
- Electroplating is the reverse of electrolysis.
Q9
Consider the cell: Ag(s) | Ag+(1.0M) || Cu2+(1.0M) | Cu(s)
- Write the chemical reaction that takes place in this cell. In which direction will the reaction proceed spontaneously?
- What is Eo for the cell?
- Do electrons floow from Ag to Cu in the external circuit, or the other way?
Q10
Consider the following cell: Ni | Ni2+(0.010M) || Sn2+(1.0M) | Sn
- Predict the direction in which spontaneous reactions will occur.
- Which metal, Ni or Sn, will be the cathode and which the anode?
- What is Eo for the cell?
- What will E be for the cell with the specified concentrations at 25°C?
Q11
Consider the cell: Sn | SnCl2 (0.10M) || AgCl(s) || Ag
- Will electrons flow spontaneously from Sn to Ag, or in the reverse direction?
- What is the standard potential, Eo, for the cell?
- What will the cell potential, E, be at 25°C?
Q12
Use the line notation of the previous problems to represent a cell that uses the following half-reactions:
PbO2 + 4H+ + 2e- → Pb2+ + 2H2O
PbSO4 + 2e- → Pb + SO42-
- Which is the reaction at the cathode of the cell? Which way do electrons flow in an external circuit?
- What is Eo for this cell?
Q14
Find the missing standard reduction potentials for these following half-reactions:
| Half-reaction | Eo (V) |
| MnO4- + 8H+ + 5e- → Mn2+ + 4H2O | + 1.49 |
| Au3+ + 3e- → Au(s) | + 1.42 |
| Cl2 + 2e- → 2Cl- | ? |
| AuCl4- + 3e- → Au(s) + 4Cl- | ? |
| 4H+ + NO3- + 3e- → NO + 2H2O | ? |
lf we assume that all reactants and products are at unit activity:
- Which substance in the half-reactions given is the best oxidizing agent? Which is the best reducing agent?
- Will permanganate oxidize metallic gold?
- Will metallic gold reduce nitric acid?
- Will nitric acid oxidize metallic gold in the presence of Cl- ion?
- Will metallic gold reduce pure Cl2 gas in the presence of water?
- Will chlorine oxidize metallic gold if Cl- ion is present?
- Will permanganate oxidize chloride ions?
Q15
Find the standard reduction potentials for the following half-reactions;
SO42- + 4H+ + 2e- → H2SO3 + H2O
Ag+ + e- → Ag
- Write the balanced overall reaction for a successful cell made from these two couples,
- Write the line notation for the cell.
- What is E° for the cell?
- What is the equilibrium constant for the cell reaction at 25°C?
- Calculate the ratio of activities of products and reactants, Q, that will produce a cell voltage of 0.51 V.