Reactions at Electrodes during Electrolysis
Which half-reaction will take place at the cathode during the electrolysis of molten MgCl2?
2Cl- > Cl2 + 2e-
Cl2 + 2e- > 2Cl-
Mg2+ + 2e- > Mg
Mg > Mg2+ + 2e-
Which half-reaction will take place at the cathode during the electrolysis of 0.10M aqueous KF solution
2F- > F2 + 2e-
F2 + 2e- > 2F-
2H2O + 2e- > H2 + 2OH-
2H2O > O2 + 4H+ + 4e-
Which half-reaction will take place at the anode during the electrolysis of molten MgCl2?
2Cl- > Cl2 + 2e-
Cl2 + 2e- > 2Cl-
Mg > Mg2+ + 2e-
Mg2+ + 2e- > Mg
Which half-reaction will take place at the anode during the electrolysis of 1.0 M AgNO3?
Ag > Ag+ + e-
2H2O + 2e- >H2 + 2OH-
2H2O >O2 + 4H+ + 4e-
Ag+ + e- >Ag
Cl2 + 2e- > 2Cl-
Mg > Mg2+ + 2e-
2Cl- > Cl2 + 2e-
Mg2+ + 2e- > Mg
To determine which half-reaction will take place at the cathode or anode during electrolysis, you can follow a set of rules known as the "electrolysis rule".
1. The cathode is the electrode where reduction occurs. Reduction is the gain of electrons, so you need to identify the half-reaction that involves the gain of electrons.
2. The anode is the electrode where oxidation occurs. Oxidation is the loss of electrons, so you need to identify the half-reaction that involves the loss of electrons.
Let's go through each question to determine the correct half-reactions:
1. Electrolysis of molten MgCl2:
- Cathode: The half-reaction that involves the gain of electrons is: Mg2+ + 2e- > Mg
- Anode: The half-reaction that involves the loss of electrons is: 2Cl- > Cl2 + 2e-
2. Electrolysis of 0.10M aqueous KF solution:
- Cathode: The half-reaction that involves the gain of electrons is: 2H2O + 2e- > H2 + 2OH-
- Anode: The half-reaction that involves the loss of electrons is: 2F- > F2 + 2e-
3. Electrolysis of molten MgCl2:
- Cathode: The half-reaction that involves the gain of electrons is: Mg2+ + 2e- > Mg
- Anode: The half-reaction that involves the loss of electrons is: 2Cl- > Cl2 + 2e-
4. Electrolysis of 1.0M AgNO3:
- Cathode: The half-reaction that involves the gain of electrons is: Ag+ + e- > Ag
- Anode: The half-reaction that involves the loss of electrons is: 2H2O > O2 + 4H+ + 4e-
So, the correct half-reactions for each scenario are:
1. Cathode: Mg2+ + 2e- > Mg
Anode: 2Cl- > Cl2 + 2e-
2. Cathode: 2H2O + 2e- > H2 + 2OH-
Anode: 2F- > F2 + 2e-
3. Cathode: Mg2+ + 2e- > Mg
Anode: 2Cl- > Cl2 + 2e-
4. Cathode: Ag+ + e- > Ag
Anode: 2H2O > O2 + 4H+ + 4e-
During the electrolysis of molten MgCl2, the half-reaction that will take place at the cathode is: Mg2+ + 2e- > Mg.
During the electrolysis of 0.10M aqueous KF solution, the half-reaction that will take place at the cathode is: 2H2O + 2e- > H2 + 2OH-.
During the electrolysis of molten MgCl2, the half-reaction that will take place at the anode is: 2Cl- > Cl2 + 2e-.
During the electrolysis of 1.0 M AgNO3, the half-reaction that will take place at the anode is: Ag+ + e- > Ag.