Chemistry
Write balanced equations and give your observations when the following metals react:
(i) Sodium with cold water
(ii) Calcium with cold water
(iii) Magnesium with boiling water
(iv) Magnesium with steam.
Hydrogen
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Answer
(i) When Sodium reacts with cold water, it melts, forming a silvery globule, which darts about on the surface of water. It catches fire and burns with a golden yellow flame. Bubbles of hydrogen gas are liberated. The solution formed is colourless, soapy, slightly warm and alkaline.
2Na + 2H2O ⟶2NaOH + H2 ↑
(ii) Calcium sinks in water and the reaction is less vigorous than Sodium. Bubbles of hydrogen gas are liberated and the solution turns milky, turbid and alkaline. If red litmus is introduced in solution, it turns blue.
Ca + 2H2O ⟶ Ca(OH)2 + H2 ↑
(iii) Magnesium reacts slowly with boiling water and forms a base, magnesium hydroxide, liberating hydrogen gas.
Mg + 2H2O ⟶ Mg(OH)2 + H2 ↑
(iv) Magnesium burns in steam with an intense white light, liberating hydrogen gas and white ash which is magnesium oxide.
Mg + H2O ⟶ MgO + H2 ↑
Magnesium oxide crumbles down due to heating. Further exposing magnesium to steam results in the liberation of hydrogen gas.
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