Unit 3 - Topic 2 - Electricity and Chemistry

Electrolysis takes place when electricity is passed through an ionic compound in solution or in the liquid state. A solution that conducts electricity is called an electrolyte.

The copper ion in copper (II) chloride has a positive charge, therefore, it is attracted to the negative electrode The chloride ion has a negative charge, therefore, it is attracted to the positive electrode.

To clearly identify the products.

The chloride ion is attracted to the positive electrode because the chloride ion is negatively charged. At the positive electrode, the chlorine will lose an electron to become chlorine gas. This loss of electrons is called oxidation.

The copper ion is attracted to the negative electrode because the copper ion is positively charged. At the negative electrode, the copper (II) ion will gain 2 electrons to become copper metal. This loss of electrons is called reduction.

Reduction is the gain of electrons Whenever a metal is extracted from its ore, the metal is reduced. In a reduction ion electron equation, the electrons (e-) are always on the left of the arrow.

Oxidation is the loss of electrons. In a oxidation ion electron equation, the electrons (e-) are always on the right of the arrow.

Oxidation and reduction occur at the same time. If one substance is oxidised, the other is reduced. This is called a redox reaction.

A simple cell (or battery) can made by joining zinc to copper An electrical current flows from the zinc electrode to the copper electrode For zinc atoms to produce electrons they have to change into zinc ions The zinc atoms are oxidised as each atom loses 2 electrons The salt solution is an electrolyte. The ions in the salt solution completed the circuit

Compounds which conduct electricity when molten or in aqueous solution are called ELECTROLYTES. Regularly, electrolytes are used to complete circuits. All ionic compounds are electrolytes. All cells (batteries) require electrolytes.

A simple battery is called a cell All metals change into their ions, giving off electrons when they react. However, different metals are not equally good at changing into their ions. The electrons, which come off the metal atoms, build up on the surface of the metal. Measuring the voltage between two different metals gives a measure of the difference in their abilities to change into their ions and give off electrons.

In a simple cell, the metal that is higher up in the electrochemical series is oxidised (lose electrons). The mass of the oxidised metal will decrease. The metal that is lower down in the electrochemical series will be reduced (gain electrons). The further apart the metals in the in the electrochemical series, the larger the voltage. Electrons flow through the wire from the metal higher to the metal lower in the electrochemical series. The ionic solution is an electrolyte. It completes the circuit.

The metal higher in the reactivity series is oxidised, the metal lower in the reactivity series is reduced. The metal electrode that is oxidised will decrease in mass. The electrons flow through the wire from the metal that is oxidised to the metal that is reduced.

An ELECTROCHEMICAL CELL makes an electric current from chemicals. This name is often shortened to a CELL.

The electrochemical cell does not work without a salt bridge. Another name for a salt bridge is an ion bridge The ion bridge ensures the solutions are always electrically neutral by allowing ions to move between the solutions.

To complete the circuit

To clearly identify the products.

The electrons are flowing the other way