Chemical Equations and Balancing Solved Examples (10 Chemistry)
Balancing chemical equations ensures conservation of mass by having equal numbers of each atom type on both sides. These examples cover balancing methods,
TL;DR: Balancing chemical equations ensures conservation of mass by having equal numbers of each atom type on both sides. These examples cover balancing meth…
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Balancing chemical equations ensures conservation of mass by having equal numbers of each atom type on both sides. These examples cover balancing methods,
Chemical Equations and Balancing — Solved Numerical Examples (Step by Step)
Example 1: Balance the equation: Fe + O2 → Fe2O3
Solution: Step 1: Count atoms on each side (unbalanced).
Left: 1 Fe, 2 O
Right: 2 Fe, 3 O
Step 2: Balance Fe atoms first. Put 2 on left.
2Fe + O2 → Fe2O3
Step 3: Count again.
Left: 2 Fe, 2 O
Right: 2 Fe, 3 O
Step 4: Balance O atoms. Need 3 O on left, so need 1.5 O2 = 3/2 O2
2Fe + 3/2 O2 → Fe2O3
Step 5: Multiply all coefficients by 2 to remove fraction.
4Fe + 3O2 → 2Fe2O3
Example 2: Balance: C + O2 → CO2
Solution: Step 1: Count atoms.
Left: 1 C, 2 O
Right: 1 C, 2 O
The equation is already balanced.
Verification: 1 carbon on each side, 2 oxygens on each side.
Example 3: Balance: H2 + O2 → H2O
Solution: Step 1: Count atoms (unbalanced).
Left: 2 H, 2 O
Right: 2 H, 1 O
Step 2: Balance O atoms. Put 2 on right.
H2 + O2 → 2H2O
Step 3: Count again.
Left: 2 H, 2 O
Right: 4 H, 2 O
Step 4: Balance H atoms. Put 2 on left.
2H2 + O2 → 2H2O
Verification: 4 H on left, 4 H on right; 2 O on left, 2 O on right.
Example 4: How many moles of CO2 are produced from 5 moles of C in the reaction C + O2 → CO2?
Solution: From the balanced equation: C + O2 → CO2
Molar ratio: 1 mole C : 1 mole CO2
Given: 5 moles of C
Moles of CO2 = 5 × (1 mole CO2 / 1 mole C) = 5 moles CO2
Example 5: Balance: Ca(OH)2 + HCl → CaCl2 + H2O
Solution: Step 1: Count atoms (unbalanced).
Left: 1 Ca, 2 O, 2 H, 1 Cl
Right: 1 Ca, 2 Cl, 2 H, 1 O
Step 2: Balance Cl atoms. Put 2 on right (since Ca(OH)2 has 2 OH groups).
Ca(OH)2 + 2HCl → CaCl2 + H2O
Step 3: Count again.
Left: 1 Ca, 2 O, 4 H, 2 Cl
Right: 1 Ca, 2 Cl, 2 H, 1 O
Step 4: Balance O and H. Put 2 on right for H2O.
Ca(OH)2 + 2HCl → CaCl2 + 2H2O
Verification: Ca=1, Cl=2, H=4, O=2 on both sides.
Example 6: In the reaction 2Na + Cl2 → 2NaCl, how many moles of NaCl are formed from 4 moles of Na?
Solution: From balanced equation: 2 moles Na : 2 moles NaCl
Ratio is 1 : 1
Given: 4 moles Na
Moles of NaCl = 4 × (2 moles NaCl / 2 moles Na) = 4 moles NaCl
Example 7: Balance: CH4 + O2 → CO2 + H2O
Solution: Step 1: Count atoms (unbalanced).
Left: 1 C, 4 H, 2 O
Right: 1 C, 2 H, 3 O
Step 2: Balance H atoms. Put 2 on right.
CH4 + O2 → CO2 + 2H2O
Step 3: Count O atoms on right: 2 (from CO2) + 2 (from 2H2O) = 4 O atoms
Need 4 O on left, so put 2 O2.
CH4 + 2O2 → CO2 + 2H2O
Verification: C=1, H=4, O=4 on both sides.
Tips
- Start balancing with elements that appear in only one compound on each side.
- Balance metals first, then non-metals, then hydrogen, then oxygen (rough guideline).
- Use fractional coefficients if needed, then multiply all by the smallest whole number to remove fractions.
- Always verify by counting atoms on both sides after balancing.
Frequently Asked Questions
Why do we balance chemical equations?
Balancing ensures conservation of mass and atoms. The same number of each type of atom must appear on both sides of the equation, reflecting the fact that atoms are neither created nor destroyed in a chemical reaction.
Can you change subscripts in a chemical formula to balance an equation?
No, you can only change coefficients (numbers in front of formulas). Changing subscripts changes the chemical formula itself, creating a different compound entirely.
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- Solutions - Previous Year Questions
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