Question

(a) What is a balanced chemical equation ? Why should chemical equations be balanced ?

(b) Aluminium burns is chlorine to form aluminium chloride $\left(AlC{l}_3\right)$. Write a balanced chemical equation for this reation.

(c) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas. Write a balanced chemical equation for this reaction.

Answer 1

(a) A reaction which has an equal number of atoms of all the elements on both sides of the chemical equation is called a balanced chemical equation. [0.5 marks]

The law of conservation of mass states that mass can neither be created nor destroyed. Hence, in a chemical reaction, the total mass of reactants should be equal to the total mass of the products. It means that the total number of atoms of each element should be equal on both sides of a chemical equation. Hence, it is for this reason that chemical equations should be balanced. [0.5 marks]

(b) Aluminium burns is chlorine to form aluminium chloride
$2\mathrm{Al}+3{\mathrm{Cl}}_2\to 3{\mathrm{AlCl}}_3$

[1 mark]

(c) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas.

[1 mark]