5.5.3 Electrolysis of Molten lead (II) bromide

Posted on March 16, 2015 by user

5.5.3 Electrolysis of Molten lead (II) bromide

1. Figure above shows the apparatus set up for electrolysis of molten lead (II) bromide.

2. Lead (II) bromide powder in a crucible is heated.

3. The electrolysis process start when le an (II) bromide start melting.

4. At the Cathode

When electricity is flowing, a silvery deposit of lead metal forms on the cathode.

5. At the Anode

When electricity is flowing, brown fumes of bromine gas are seen at the anode.

Explanation:

6. Thus, electrolysis of lead (II) bromide produces lead and bromine gas.

5.5.2 Electrolysis of Copper (II) Chloride Solution

Posted on March 12, 2015 by user

5.5.2 Electrolysis of Copper (II) Chloride Solution

1. Electrolysis of copper (II) chloride solution.
(a) Copper (II) ion with positive charge will attract to cathode to discharge as a copper.
(b) Chloride ion will attract to anode to discharge as a chlorine gas.
(c) At anode, chloride ions lose electrons. Greenish gas which can bleach the litmus paper is produced.
(d) At cathode, copper (II) ion receives electron. Brown solid deposited on the surface of the electrode.

2. Thus, electrolysis of copper (II) chloride produces copper and chlorine gas.

5.5 Electrolysis

Posted on March 10, 2015 by user

5.5 Electrolysis

5.5.1 Electrolysis

1. Electrolysis is a process where a compound is separated into its constituent elements when electric current passes through an electrolyte.

2. In electrolysis, energy is changed as shown below:

Electrical energy \to chemical energy

3. The apparatus used in an electrolytic cell consists of a dry cell or battery, an electrolyte and two electrodes as shown below.

Electrolytic cell

Electrolyte

(a) An electrolyte is a compound in a molten form or in aqueous solution which conducts electric current.

(b) Electrolyte contains two types of charged ions which move freely:
(i) Ion with positive charge (cation), for example, metal ions and hydrogen ions.
(ii) Ion with negative charge (anion), for example, non-metal ions.

(c) Example of electrolyte: molten potassium chloride and hydrocloric acid.

Electrode

(a) Electrode is a conductor which is immersed in an electrolyte and connected to an electric source.

(b) Examples of electrode: carbon (graphite) and platinum.

(c) The electrode connected to the positive terminal of the cell is positive electrode and is given a name, anode.

(d) The electrode connected to the negative terminal of the cell is negative electrode and is called the cathode.

Ammeter

Ammeter is used to detect the flow of current in the circuit.

Dry cell or battery

The source that generates electrical energy.

5.4.2 Reactivity Series and Extraction of Metals

Posted on March 2, 2015 by user

5.4.2 Reactivity Series and Extraction of Metals

1. The method that is used in the extraction of metal from its are depends on the position of the metal in the reactivity series of metals.

2. Metals which are located higher than carbon in the reactivity series are extracted from their molten ores using the electrolysis method.

3. Metals which are located lower than carbon in the reactivity series are extracted using the reduction method with coke (or carbon).

4. Carbon is used in the extraction process because

(a) It is cheap

(b) Easily obtained

5. Metals located the lowest in the reactivity series like silver and gold can be extracted naturally without any complex chemical reaction. These metals exist as free elements in the Earth’s crust.