Thursday, November 27, 2008

Chemicals from salt- gcse/igcse

The electrolysis of aqueous sodium chloride solution

When the electrolysis of aqueous sodium chloride takes place, hydrogen and chlorine are given off as gases and sodium hydroxide is left. Aqueous sodium chloride contains hydrogen ions H+ and hydroxide ions OH- (from the water) and sodium ions Na+ and chloride ions Cl-.

The positive sodium and hydrogen ions go to the cathode and the negative chloride and hydroxide ions go to the anode. Hydrogen is formed at the cathode and chlorine is formed at the anode.

substance test result


lighted splint squeaky pop


damp blue litmus turns red then white

sodium hydroxide

damp red litmus turns blue/purple

Write a word and a balanced chemical equation for the reaction in which hydrogen burns.
Complete: Chlorine is (acidic/alkaline) because
it turns litmus red.
Chlorine is a (dye/bleach) because it turns litmus white.
This type of reaction is (oxidation/reduction).

Uses of sodium chloride, hydrogen, chlorine and sodium hydroxide

sodium chloride preserve food, flavouring, stops ice on roads because salt lowers freezing point of water to -5oC,

manufacture of sodium, chlorine and sodium hydroxide

chlorine kills bacteria in swimming pools and drinking water, bleach, making hydrochloric acid and solvents.

hydrogen rocket fuel, making margarine, making ammonia
sodium hydroxide detergents, bleach, paper, fibres, purifying bauxite

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chemistry notes / igcse-gcse- Olevel