give three example of reaction between metal and water, to show that different metals have different reactivites
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Answer:
Let us take four metals according to their reactivity, Potassium, Calcium, Iron and Gold.
1) Potassium with water
K + H2O = KOH + H2(g)
Potassium is a highly reactive metal so it reacts with cold water and immediately catches fire. It is a highly exothermic reaction.
2) Calcium with water
Ca + H20 = Ca(OH)2 + H2(g)
Calcium reacts with hot water as it is medium reactive metal. Bubbles evolved stick to the surface of calcium metal as heat evolved is not sufficient.
3) Iron with water
Fe + H2O = Fe3O4 + H2(g)
Iron reacts with steam to release hydrogen gas.
4) Gold with water
Gold doesn't react with water.
These experiments demonstrate that different metals react with water at different temperatures. The descending reactivity of these metals is: Potassium, Calcium, Iron and Gold.
(PS: Please appreciate, took time in writing this)