### Chapter 1: Chemical reactions and equations

Q
##### Chemical reactions and equations

Question:

Write the balanced equation for the following chemical reactions.

(i) Hydrogen + Chlorine → Hydrogen Chloride

(ii) Barium chloride + Aluminium sulphate → Barium sulphate +  Aluminium chloride

(iii) Sodium + Water → Sodium hydroxide + Hydrogen

(i) Hydrogen and chlorine exist as diatomic molecules. So, the chemical equation for this reaction is written as:

H2 (g) + Cl2 (g) → HCl (g)

The number of atoms of different elements present in the given unbalanced equation is as follows: Multiply 2 in the product side as shown below:

H2 (g) + Cl2 (g) → 2 HCl (g)

The number of atoms of different elements present in the given balanced equation is as follows: Therefore, the correct answer is H2 + Cl2 → 2 HCl.

(ii) The chemical equation for the given reaction is written as:

BaCl2 (s) + Al2(SO4)3 (aq) → BaSO4 (aq) + AlCl3 (s)

The number of atoms of different elements present in the given unbalanced equation is as follows: First balance chlorine by multiply 3 in the reactant and 2 in the product side as shown below:

3 BaCl2 (s) + Al2(SO4)3 (aq) → BaSO4 (aq) + 2 AlCl3 (s)

So, we have six atoms of chlorine and two atoms of aluminium on both sides of the equation.  Now, balance barium atom by multiplying 3 on the product side as shown below:

3 BaCl2 (s) + Al2(SO4)3 (aq) → 3 BaSO4 (aq) + 2 AlCl3 (s)

The number of atoms of different elements present in the given balanced equation is as follows: Therefore, the correct answer is 3BaCl2+ Al2(SO4)3 → 3BaSO4 + 2AlCl3

(iii) The chemical equation for the given reaction is written as:

Na (s) + H2O (l) → NaOH (aq) + H2 (g)

The number of atoms of different elements present in the given unbalanced equation is as follows: First balance hydrogen by multiply 2 in the reactant and 2 in the product side as shown below:

Na (s) + 2 H2O (l) → 2 NaOH (aq) + H2 (g)

Now, balance the sodium atom by multiplying 2 on the reactant side as shown below:

2 Na (s) + 2 H2O (l) → 2 NaOH (aq) + H2 (g)

The number of atoms of different elements present in the given balanced equation is as follows: Therefore, the correct answer is 2Na+ 2H2O→ 2NaOH+ H2

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