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Question
Explain, all alkalis are bases but all bases are not alkalis.
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Solution
An alkali is a base which is soluble in water but all bases are not water soluble.
For example Ferric hydroxide [Fe(OH)3] and cupric hydroxide [ Cu(OH)2 ] are bases but these are not soluble in water but sodium hydroxide NaOH, calcium hydroxide Ca(OH)2 are bases and are also soluble in water.
Hence it is rightly said that all alkalis are bases but all bases are not alkalis.
Concept Insight : An alkali is a basic hydrooxide which when dissolved in water produces hydroxyl (OH-) ions as the only negatively charged ions.
Example : NaOH(aq) ⇌ Na+ + OH-
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