Balancing Chemical Reactions at a glance

 

Balancing Chemical Reactions

A chemical equation shows how substances react to form new substances.
A balanced chemical equation has the same number of each type of atom on both sides of the equation.

This is based on the Law of Conservation of Mass, which states that matter is neither created nor destroyed in a chemical reaction.

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Steps for Balancing Chemical Equations

1. Write the correct chemical formula for all reactants and products.

2. Count the number of each atom on both sides.

3. Adjust the coefficients (numbers in front of formulas) to make the atoms equal.

4. Do not change subscripts in the formulas.

5. Check that all atoms are balanced.

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Examples

1. Formation of Water

Unbalanced:
H₂ + O₂ → H₂O

Balanced:
2H₂ + O₂ → 2H₂O

2. Formation of Magnesium Oxide

Unbalanced:
Mg + O₂ → MgO

Balanced:
2Mg + O₂ → 2MgO

3. Reaction of Hydrogen and Chlorine

Unbalanced:
H₂ + Cl₂ → HCl

Balanced:
H₂ + Cl₂ → 2HCl

4. Combustion of Methane

Unbalanced:
CH₄ + O₂ → CO₂ + H₂O

Balanced:
CH₄ + 2O₂ → CO₂ + 2H₂O

5. Reaction of Zinc with Hydrochloric Acid

Unbalanced:
Zn + HCl → ZnCl₂ + H₂

Balanced:
Zn + 2HCl → ZnCl₂ + H₂

Conclusion

Balancing chemical equations ensures that the number of atoms on both sides is equal, showing that mass is conserved in chemical reactions.

EASYKEMISTRY

Chemistry Test – Balancing Chemical Equations
Time: 30 Minutes

Name: __________________________ Class: __________ Date: __________

SECTION A – Balance the following equations

(Each question carries 2 marks)

1.     H₂ + N₂ → NH₃

2.     Fe + H₂O → Fe₃O₄ + H₂

3.     Na + H₂O → NaOH + H₂

4.     Al + O₂ → Al₂O₃

5.     CaCO₃ → CaO + CO₂

6.     KClO₃ → KCl + O₂

7.     Zn + HNO₃ → Zn(NO₃)₂ + H₂

8.     C₂H₆ + O₂ → CO₂ + H₂O

9.     Pb(NO₃)₂ → PbO + NO₂ + O₂

10.     Cu + HNO₃ → Cu(NO₃)₂ + NO₂ + H₂O

SECTION B – Answer all questions

1.      What is meant by a balanced chemical equation?

    

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2.      State the law that is obeyed when chemical equations are balanced.

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3.     Why is it important to balance chemical equations

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4.     Why should subscripts not be changed when balancing equations?

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5. Write a balanced chemical equation for the reaction between magnesium and dilute hydrochloric acid.

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END OF TEST