MU #1 An electrolytic cell requires electrical energy to produce chemical change. This process is known as electrolysis.

Example

An electrolytic cell is used to plate a metallic object (ex: a spoon) with a layer of another metal (ex: silver)  the process is called electroplating.

Problem

Draw an electrolytic cell representing  the electroplating of a fork with gold.

Example

An electrolytic cell is used to produce Na(l) (a very active metal) and Cl₂(g) (a very dangerous gas) from the electrolysis of  NaCl (l)

Problem

Draw an electrolytic cell showing the production of  Li(l) and F₂(g) from the electrolysis LiF(l)

Example 

An electrolytic cell is used to produce pure metal (ex: 99.9 % nickel) from impure metal (ex: 60.7 % nickel) the process is called electrorefining.

Problem

Draw an electrolytic cell showing the electrorefining of chromium.

Example 

An electrolytic cell is used to produce H₂(g) and O₂(g) from the electrolysis of water.

Problem

Draw an electrolytic cell showing the electrolysis of NH₃(l) to produce H₂(g) and N₂(g)

TEST YOUR UNDERSTANDING

1. In an electrolytic cell, a negative ion will migrate to and undergo oxidation at the

(1) anode, which is negatively charged   (3) cathode, which is negatively charged

(2) anode, which is positively charged   (4) cathode, which is positively charged

2.  A metal object is to be electroplated with silver. Which set of electrodes should be used?

(1) a silver anode and a metal object as the cathode       (3) a silver cathode and a metal object as the anode

(2) a platinum anode and a metal object as the cathode (4) a platinum cathode and a metal object as the anode

3. The diagram shows the electrolysis of fused KCl. What occurs when the switch is closed?

 1. Positive ions migrate toward the anode, where they lose electrons.  3. Positive ions migrate toward the cathode, where they lose electrons.      

 2. Positive ions migrate toward the anode, where they gain electrons. 4. Positive ions migrate toward the cathode, where they gain electrons.

4. Which net reaction occurs by the process of electrolysis?

5. The diagram shows a spoon that will be electroplated with nickel metal. What will occur when switch S is closed?

            1. The spoon will lose mass, and the Ni(s) will be reduced    3. The spoon will gain mass, and the Ni(s) will be reduced     

            2. The spoon will lose mass, and the Ni(s) will be oxidized       4. The spoon will gain mass, and the Ni(s) will be oxidized 

6. In which kind of cell are the redox reactions made to occur by an externally applied electrical current?

            1. galvanic cell  2. chemical cell 3. electrochemical cell   4. electrolytic cell

7. Which atom forms an ion that would migrate toward the cathode in an electrolytic cell? 1. F      2. I       3. Na     4. Cl

8/07

Base your answers to questions 83 and 84 on the information below.

Electroplating is an electrolytic process used to coat metal objects with a more expensive and less reactive metal. The diagram below shows an electroplating cell that includes a battery connected to a silver bar and a metal spoon. The bar and spoon are submerged in AgNO₃(aq).

83 Explain why AgNO₃ is a better choice than AgCl for use in this electrolytic process.

84 Explain the purpose of the battery in this cell.

6/02

Which process requires an external power source?  (1) neutralization     (2) synthesis     (3) fermentation       (4) electrolysis

6/03

Base your answers to questions 57 and 58 on the information below.

Two chemistry students each combine a different metal with hydrochloric acid. Student A uses zinc, and hydrogen gas is readily produced. Student B uses copper, and no hydrogen gas is produced.

57. State one chemical reason for the different results of students A and B. 

58. Using Reference Table J, identify another metal that will react with hydrochloric acid to yield hydrogen gas. 

63. State one difference between voltaic cells and electrolytic cells. Include information about both types of cells in your answer.

8/03

48 A voltaic cell differs from an electrolytic cell in that in a voltaic cell
        (1) energy is produced when the reaction occurs       (2) energy is required for the reaction to occur
        (3) both oxidation and reduction occur                         (4) neither oxidation nor reduction occurs

1/04

24 Which energy transformation occurs when an electrolytic cell is in operation?
        (1) chemical energy electrical energy (2) electrical energy chemical energy (3) light energy heat energy (4) light energy chemical energy

44 The diagram below shows a key being plated with copper in an electrolytic cell.

 Given the reduction reaction for this cell: Cu²⁺ (aq) +2e- ---> Cu(s) This reduction occurs at
        (1) A, which is the anode (2) A, which is the cathode (3) B, which is the anode (4) B, which is the cathode

1/06

84 What type of electrochemical cell is shown?

Base your answers to questions 78 through 81 on the information below. Aluminum is one of the most abundant metals in Earth’s crust. The aluminum compound found in bauxite ore is Al2O3. Over one hundred years ago, it was difficult and expensive to isolate aluminum from bauxite ore. In 1886, a brother and sister team, Charles and Julia Hall, found that molten (melted) cryolite, Na3AlF6, would dissolve bauxite ore. Electrolysis of the resulting mixture caused the aluminum ions in the Al2O3 to be reduced to molten aluminum metal. This less expensive process is known as the Hall process.

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