Chemistry: Which Electrode Undergoes Which Reaction (AN OX, RED CAT) Practice
Use AN OX and RED CAT to identify oxidation, reduction, anodes, and cathodes
Chemistry: Which Electrode Undergoes Which Reaction (AN OX, RED CAT) Practice
Use AN OX and RED CAT to identify oxidation, reduction, anodes, and cathodes
Chemistry - Grade 9-12
- 1
In any electrochemical cell, oxidation occurs at one electrode and reduction occurs at the other electrode. State which reaction happens at the anode and which reaction happens at the cathode.
AN OX means anode oxidation. RED CAT means reduction cathode.
Oxidation occurs at the anode, and reduction occurs at the cathode. This matches the memory aid AN OX and RED CAT. - 2
A zinc-copper galvanic cell has the overall reaction: Zn(s) + Cu2+(aq) -> Zn2+(aq) + Cu(s). Identify the anode, the cathode, the oxidation half-reaction, and the reduction half-reaction.
Look for the species that loses electrons and the species that gains electrons.
The zinc electrode is the anode because zinc is oxidized from Zn(s) to Zn2+(aq). The copper electrode is the cathode because Cu2+(aq) is reduced to Cu(s). The oxidation half-reaction is Zn(s) -> Zn2+(aq) + 2e-, and the reduction half-reaction is Cu2+(aq) + 2e- -> Cu(s). - 3
In a cell, the half-reaction at the silver electrode is Ag+(aq) + e- -> Ag(s). Is the silver electrode the anode or the cathode? Explain your answer.
The silver electrode is the cathode because Ag+(aq) gains an electron to form Ag(s). Gaining electrons is reduction, and reduction occurs at the cathode. - 4
In a cell, the half-reaction at the iron electrode is Fe(s) -> Fe2+(aq) + 2e-. Is the iron electrode the anode or the cathode? Explain your answer.
Electrons on the product side usually mean oxidation.
The iron electrode is the anode because Fe(s) loses electrons to form Fe2+(aq). Losing electrons is oxidation, and oxidation occurs at the anode. - 5
A diagram shows electrons flowing through a wire from an aluminum electrode to a nickel electrode in a galvanic cell. Which electrode is the anode, and which electrode is the cathode?
The aluminum electrode is the anode because electrons leave the anode in a galvanic cell. The nickel electrode is the cathode because electrons arrive at the cathode. - 6
For the half-reaction Mg(s) -> Mg2+(aq) + 2e-, identify whether oxidation or reduction is occurring and name the electrode where this reaction occurs.
Loss of electrons is oxidation.
Oxidation is occurring because magnesium loses electrons. This reaction occurs at the anode. - 7
For the half-reaction Pb2+(aq) + 2e- -> Pb(s), identify whether oxidation or reduction is occurring and name the electrode where this reaction occurs.
Reduction is occurring because lead ions gain electrons. This reaction occurs at the cathode. - 8
An electrolytic cell is used to plate copper metal onto a spoon. Copper ions in solution become copper metal on the spoon: Cu2+(aq) + 2e- -> Cu(s). Is the spoon the anode or the cathode? Explain.
Electroplating deposits metal where reduction occurs.
The spoon is the cathode because Cu2+(aq) gains electrons and is reduced to Cu(s) on the spoon. Reduction always occurs at the cathode, including in an electrolytic cell. - 9
A student labels a cathode as the place where oxidation happens because it is positive in a galvanic cell. Correct the student's mistake using AN OX and RED CAT.
The student is incorrect because oxidation happens at the anode, not the cathode. RED CAT means reduction occurs at the cathode, even though the cathode is positive in a galvanic cell. - 10
In a galvanic cell made from tin and silver, the tin electrode loses mass while silver metal forms on the silver electrode. Identify the anode and cathode, and state which electrode undergoes oxidation.
In a galvanic cell, the metal that dissolves is usually being oxidized.
The tin electrode is the anode because it loses mass as tin atoms become ions in solution. The silver electrode is the cathode because silver ions are reduced to silver metal. Oxidation occurs at the tin electrode. - 11
Write the missing electrode type for each statement: oxidation occurs at the blank, and reduction occurs at the blank.
Oxidation occurs at the anode, and reduction occurs at the cathode. This is summarized by AN OX and RED CAT. - 12
A cell has these two half-reactions: Ni(s) -> Ni2+(aq) + 2e- and Sn2+(aq) + 2e- -> Sn(s). Identify the anode, cathode, oxidation half-reaction, reduction half-reaction, and the direction of electron flow through the wire.
In a galvanic cell, electrons flow from anode to cathode through the external circuit.
The nickel electrode is the anode because Ni(s) is oxidized to Ni2+(aq). The tin electrode is the cathode because Sn2+(aq) is reduced to Sn(s). The oxidation half-reaction is Ni(s) -> Ni2+(aq) + 2e-, and the reduction half-reaction is Sn2+(aq) + 2e- -> Sn(s). Electrons flow through the wire from the nickel anode to the tin cathode.