Class 10 Science
When a metal reacts with a diulte acid, salt and hydrogen gas are formed. Following is the general equation for this reaction.
Metal + dil. acid ⇨ Metal salt + Hydrogen
When sodium reacts with dilute hydrochloric acid, then sodium chloride is formed and hydrogen gas evolves. Following equations shows this reaction.
2Na + 2HCl ⇨ 2NaCl + H2
When potassium reacts with dilute sulphuric acid, then potassium sulphate and hydrogen gas are formed. Following equation shows this reaction.
2K + H2SO4 ⇨ K2SO4 + H2
When magnesium reacts with dilute hydrochloric acid, then magnesium chloride and hydrogen gas are formed. Following equation shows this reaction.
Mg + 2HCl ⇨ MgCl2 + H2
When aluminium reacts with dilute hydrochloric acid, then aluminium chloride and hydrogen gas are formed. Following equation shows this reaction.
2Al + 6HCl ⇨ 2AlCl3 + 3H2
When zinc reacts with dilute sulphuric acid, then zinc sulphate and hydrogen gas are formed. Following equation shows this reaction.
Zn + H2SO4 ⇨ ZnSO4 + H2
Copper, gold and silver are known as noble metals. These metals do not react with dilute acids.
| Reaction with water | Being basic in nature, the solution of metal oxides is alkaline. It is important to remember that oxides of alkali metals are soluble in water. |
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| Amphoteric oxide | Oxides of some metals show dual behaviour, i.e. acidic and basic, e.g. aluminium oxide and zinc oxide. These are called amphoteric oxide. |
Metal oxides are basic in nature. That is why, aqueous solution of metal oxides turns red litmus blue.
Most of the metal oxides are insoluble in water. Alkali metal oxides are soluble in water. Alkali metal oxides give strong base when dissolved in water.
When sodium oxide reacts with water, it gives sodium hydroxide. Following equation shows this reaction.
Na2O + H2O ⇨ 2NaOH
When magnesium oxide reacts with water, it gives magnesium hydroxide. Following equation shows this reaction.
MgO + H2O ⇨ Mg(OH)2
When potassium oxide reacts with water, it gives potassium hydroxide. Following equation shows this reaction.
K2O + H2O ⇨ 2KOH
Both aluminium oxide and zinc oxide are insoluble in water. Aluminium oxide and zinc oxide are amphoteric in nature. An amphoteric substance shows both acidic and basic character. It reacts with base like an acid, and reacts with an acid like a base. In other words, amphoteric substance shows dual nature, i.e. both acidic and basic nature.
Acidic Nature of Zinc Oxide: When zinc oxide reacts with sodium hydroxide, it behaves like an acid. In this reaction, sodium zicate and water are formed. Following equation shows this reaction.
ZnO + 2NaOH ⇨ Na2ZnO2 + H2O
Basic Nature of Zinc Oxide: Zinc oxide behaves like a base when it reacts with acid. Zinc oxide gives zinc chloride and water on reaction with hydrochloric acid. Following equation shows this reaction.
ZnO + 2HCl ⇨ ZnCl2 + H2O
Similarly, aluminium oxide behaves like a base when it reacts with an acid, and behaves like an acid when it reacts with a base.
Acidic Nature of Aluminium Oxide: Aluminium oxide gives sodium aluminate along with water, when it reacts with sodium hydroxide. Following equation shows this reaction.
Al2O3 + 2NaOH ⇨ 2NaAlO2 + H2O
Basic Nature of Aluminium Oxide: Aluminium oxide gives aluminium chloride along with water, when it reacts with hydrochloric acid. Following equation shows this reaction.
Al2O3 + 6HCl ⇨ 2AlCl3 + 3H2O
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