Reaction of metals with water
Reaction of metals with water produces metal oxide and hydrogen gas. The metal oxides dissolves in excess of water forming metal hydroxides. Since heat is released during reaction therefore the reaction is exothermic.
Metal + Water → Metal oxide + Hydrogen
Metal oxide + Water → Metal hydroxide + Heat
2K(s) + 2H2O(l) → 2KOH(aq) + H2(g) + heat energy
Reaction of metals: Highly Reactive Metals with Water
- Metals such as sodium, potassium reacts violently with cold water that the released hydrogen catches fire immediately,
2K (s) + 2H2O (l) → 2KOH (aq) + H2 (g) + Heat energy
2Na (s) + 2H2O (l) → 2NaOH (aq) + H2 (g) + Heat energy - Calcium reacts with water less vigorously therefore the heat produced is not sufficient to catch fire.
Ca(s) + 2H2O(l) → Ca(OH)2(aq) + H2(g) + Heat energy
The hydrogen produced stick to the surface of calcium and hence calcium floats on water. - Magnesium does not react with cold water. It reacts with hot water and produces magnesium hydroxide releasing hydrogen. It also starts floating due to the bubbles of hydrogen gas sticking to its surface.
Mg (s) + 2H2O (l) → Mg(OH)2 (aq) + H2 (g)
Reaction of metals: Moderately Reactive Metals with Water
- Metals like Aluminium, Iron and Zinc react with steam to form metal oxide and hydrogen .
2Al (s) + 3H2O (g) → Al2O3 (s) + H2 (g)
3Fe (s) + 4H2O (g) → Fe3O4 (s) + H2 (g)
Reaction of Metals: Least Reactive Metals with Water
- Least reactive metals such as gold, silver and copper do not react with water.
Reaction of Metals with Acids
- Generally metals reacts with acids to form salt and releases hydrogen gas.
Metal + Acid → Salt + Hydrogen Gas - Magnesium reacts with acids to form salt and releases hydrogen gas which is tested by burning.
E.g. Mg (s) + 2HCl (l) → MgCl2 (s) + H2 (g)
Mg (s) + H2SO4 (l) → MgSO4 (s) + H2 (g)
2Al (s) + 6 HCl (l) → 2AlCl3 (s) + 6H2 (g)
Zn (s) + 2HCl (l) → ZnCl2 (s) + H2 (g)
Zn (s) + H2SO4 (l) → ZnSO4 (s) + H2 (g)
Fe (s) + 2HCl (l) → FeCl2 (s) + H2 (g) - Some metals reacts with dilute Nitric acid (HNO3) and produces salt and any of the nitrogen oxides (N2O, NO, NO2) and water. It is because HNO3 is a strong oxidising agent. It oxidises the H2 produced to water and itself gets reduced to any of the nitrogen oxides (N2O, NO, NO2).
Cu + 4HNO3 → Cu(NO3)2 + 2NO2 + 2H2O
However magnesium and manganese react with very dilute HNO3 to evolve H2 gas.
Mg + 2HNO3 → Mg(NO3)2 + H2
Such reaction is the most exothermic. - The reactivity of metals towards the acids decreases in the order Mg > Al > Zn > Fe. In the case of copper, no bubbles were seen and the temperature also remained unchanged. This shows that copper does not react with dilute HCl.
Keywords: Reaction of Metals with Water, Reaction of metals with acids, Reaction of moderately reactive metals with water, Reaction of highly reactive metals with water, Reaction of least reactive metals with water
This article is helpful for Class 10 Science
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