What happens when (Write the balanced equation involved) –(i) Copper is heated in air?(ii) Aluminium oxide is reacted with hydrochloric acid?(iii) Potassium reacts with water?(iv) Cinnabar is heated in air?(v) Aluminium oxide reacts with sodium hydroxide?

(i) Copper is heated in air to form the black copper oxide. The equation for the reaction is given below:

$2Cu + O_2 →2CuO$

(ii) Aluminium oxide is reacted with hot dilute hydrochloric acid to give aluminum chloride solution and water. The equation for the reaction is given below:

$Al_2O_3 + 6HCl → 2AlCl_3 + 3H_2O$

(iii) Potassium reacts with water, the metal melts and floats. It moves around very quickly on the surface of the water. The metal is set on fire, with sparks and a lilac flame. The equation for the reaction is given below:

$2K + 2H_2O → 2KOH + H_2$

(iv) Cinnabar is heated in air, cinnabar is reduced to mercuric oxide and sulphur dioxide gas is formed. The equation for the reaction is given below:

$2HgS + 3O_2 → 2HgO + 2SO_2$

(v) Aluminium oxide reacts with sodium hydroxide, to produce sodium aluminate and water. This reaction takes place at a temperature of 900-1100°C. The equation for the reaction is given below:

$Al_2O_3 + 2NaOH → 2NaAlO_2 + H_2O$

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Updated on: 10-Oct-2022

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