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| Amphoteric Behaviour of Some Hydroxides |
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| Some hydroxides behave both as bases and acids under different conditions, |
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| e.g., hydroxides of zinc, lead and aluminium. These hydroxides are only weakly basic, but like other bases, they still combine with acids to form salt and water. |
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| However in the presence of strong alkalis, these hydroxides behave like acids, and combine with them to yield a salt and water. |
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| This behaviour of amphoteric hydroxides can be better understood if the formula of zinc hydroxide is modified from Zn(OH)2 to H2ZnO2 . In this form it can be identified as hydrogen zincate and the action with sodium hydroxide can be represented as: |
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| The basic anhydride is a metal oxide that reacts with water to produce hydroxyl ions in an aqueous solution e.g. |
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iii)  |
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Study of Acids Bases and Salts
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