Write the balanced chemical equation for the following and identify the type of

reaction in each case.

(a) Potassium bromide(aq) + Barium iodide(aq) → Potassium iodide(aq) +

Barium bromide(s)

(b) Zinc carbonate(s) → Zinc oxide(s) + Carbon dioxide(g)

(c) Hydrogen(g) + Chlorine(g) → Hydrogen chloride(g)

(d) Magnesium(s) + Hydrochloric acid(aq) → Magnesium chloride(aq) + Hydrogen(g)

 

Answer

 

  • KBr(aq) + BaI 2 (aq) → KI(aq) + BaBr 2 (s)

 

Name of the element

No. of atoms in reactants

No. of atoms in products

Potassium

1

1

Bromine

1

2

Barium

1

1

Iodine

2

1

 

To balance Bromine,

Multiply KBr by 2

2 KBr + BaI 2 → KI + BaBr 2

 

Name of the element

No. of atoms in reactants

No. of atoms in products

Potassium

2

1

Bromine

2

2

Barium

1

1

Iodine

2

1

 

To balance Potassium and Iodine,

Multiply KI by 2

2 KBr + BaI 2 2 KI + BaBr 2

 

Name of the element

No. of atoms in reactants

No. of atoms in products

Potassium

2

2

Bromine

2

2

Barium

1

1

Iodine

2

2

 

Now, all the elements are balanced and the balanced equation is

2 KBr(aq) + BaI 2 (aq) → 2 KI(aq) + BaBr 2 (s)

 

In this chemical reaction two compounds react and their positive and negative ions switch places to form two new products

Thus it is a Double Displacement Reaction

 

  • ZnCO 3 (s)  →  ZnO(s) + CO 2 (g)

 

Name of the element

No. of atoms in reactants

No. of atoms in products

Zinc

1

1

Carbon

1

1

Oxygen

3

3

 

The number of atoms of elements in reactants and products are equal. It does not require any further balancing.

 

Since all the elements are balanced the final balanced equation is

ZnCO 3 (s)  →  ZnO(s) + CO 2 (g)

 

In this reaction a single reactant breaks down into more than one product.

Hence it is a Decomposition Reaction .



(c) H 2 (g) + Cl 2 (g)  →  HCl(g)

 

Name of the element

No. of atoms in reactants

No. of atoms in products

Hydrogen

2

1

Chlorine

2

1

 

To balance Hydrogen and Chlorine,

Multiply HCl by 2

H 2 + Cl 2   →  2 HCl

 

Name of the element

No. of atoms in reactants

No. of atoms in products

Hydrogen

2

2

Chlorine

2

2

 

Now, all the elements are balanced and the balanced equation is

H 2 + Cl 2   →  2 HCl

 

In this reaction two substances react to form a single product

Hence it is a combination reaction.



(d) Mg(s) + HCl(aq)  →  MgCl 2 (aq) + H 2 (g)

 

Name of the element

No. of atoms in reactants

No. of atoms in products

Magnesium

1

1

Hydrogen

1

2

Chlorine

1

2

 

To balance Hydrogen and Chlorine,

Multiply HCl by 2

Mg + 2 HCl  →  MgCl 2 + H 2

 

Name of the element

No. of atoms in reactants

No. of atoms in products

Magnesium

1

1

Hydrogen

2

2

Chlorine

2

2

 

Now, all the elements are balanced and the balanced equation is

Mg(s) + 2 HCl(aq)  →  MgCl 2 (aq) + H 2 (g)

 

In this reaction a more reactive element takes the place of a less reactive element in a chemical compound .

 

Here, Magnesium is more reactive than Hydrogen

(Magnesium is above Hydrogen in the reactivity series) 

 

Hence it is a Displacement Reaction .

  1. Class 10
  2. Chapter 1 Class 10 - Chemical Reactions and Equations (Term 1)

About the Author

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CA Maninder Singh
CA Maninder Singh is a Chartered Accountant for the past 11 years and a teacher from the past 11 years. He teaches Science, Accounts and English at Teachoo