Chemistry – Acids and Alkalis 1: Introduction
Acids
Acids solutions are electrolytes, that is, they conduct electricity when they dissolve in water. They turn blue litmus paper red.
Reactions
Reactions Between Metals and Acids
Acids + metal oxide(bases) ➡️ salt + water
Dilute acids + carbonates + hydrogen-carbonates ➡️ salt + carbon dioxide + water
Basicity
The maximum number of hydrogen ions produced by one molecule of the acid is called the basicity of the acid. Acids that can give more than one hydrogen ion per molecule are called poly-basic acids.
Alkalis
Bases are 'chemical opposites' of acids. Metal oxides and metal hydroxides are bases. A few bases are soluble in water, and they are called alkalis. Ammonia is also an alkali. Alkalis are also electrolytes, and they turn red litmus paper blue.
Reactions
alkalis + acids ➡️ salt + water
alkalis + carbon dioxide ➡️ metal carbonate + water
alkalis + salt(solution) ➡️ metal hydroxides(precipitation) + new salt (solution)
Precipitates That Redissolve in Excess Sodium Hydroxide Solution
Aluminum hydroxide, zinc hydroxide and lead(II) hydroxide dissolve in excess sodium hydroxide solution; zinc hydroxide and copper(II) hydroxide dissolve in excess aqueous ammonia. This is because soluble complex ions are formed after reaction.
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