Bases and Alkalis

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Bases and Alkalis A base is a compound that reacts with and neutralises an acid. The reaction forms a salt plus water. Alkalis are a type of base - ones that dissolve in water. Alkalis are compounds that react and neutralise acids. Like bases, they form a salt and water in the reaction. Alkalis turn red litmus indicator paper blue and they cause Universal Indicator paper to turn blue or purple. Alkaline solutions have a pH value greater than 7. Alkaline solutions feel soapy and are corrosive. Examples of bases and alkalis: NAME FORMULA DOES IT DISSOLVE IN WATER ALKALI OR BASE FOUND IN/USED FOR Copper oxide CuO No Base Sodium hydroxide NaOH Yes Alkali pH 13 Used to remove grease from ovens & drains. Used to make soap Ammonia NH3 Yes Alkali pH 10 The main active ingredient in household cleaning fluids Calcium hydroxide Ca(OH)2 No Base Slaked lime used in agriculture Aluminium hydroxide Al(OH)3 No Base Used in some indigestion tablets Acids and Alkalis Neutralisation Neutralisation is the reaction of an acid with a base or alkali until the solution is neutral (pH7). In neutralisation, the acid and base (or alkali) both lose their properties and the solution becomes neutral. A salt and water are formed. Neutralisation is used in the following everyday situations: * Farmers use an alkali called calcium hydroxide (slaked lime or lime). This is spread on the fields or ploughed ground. It is used to neutralise the slightly acidic soil or even to make the soil slightly alkaline, because grass and vegetable crops often need often soils with a specific pH to grow well. * When you get a burning feeling in your throat after you've been

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