Balancing Chemical Equations

Introduction

• Focus on balancing chemical equations.
• Goal: Make sure atoms are equal on both sides of the reaction.

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Example 1: Combustion of Propane (C₃H₈)

Reaction: C₃H₈ + O₂ → CO₂ + H₂O

1. Balance Carbon (C):

   • 3 C on left, need 3 CO₂ on right.
   • Add 3 in front of CO₂.

2. Balance Hydrogen (H):

   • 8 H on left, need 4 H₂O on right (8/2 = 4).

3. Balance Oxygen (O):

   • 6 O from 3 CO₂ + 4 O from 4 H₂O = 10 O on right.
   • Need 5 O₂ on left (10/2 = 5).

Final Balanced Equation:

• C₃H₈ + 5 O₂ → 3 CO₂ + 4 H₂O

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Example 2: Combustion of Butane (C₄H₁₀)

Reaction: C₄H₁₀ + O₂ → CO₂ + H₂O

1. Balance Carbon (C):

   • 4 C on left, need 4 CO₂ on right.

2. Balance Hydrogen (H):

   • 10 H on left, need 5 H₂O on right (10/2 = 5).

3. Balance Oxygen (O):

   • 4 CO₂ gives 8 O, 5 H₂O gives 5 O = 13 O on right.
   • Use fraction: 13/2 O₂, multiply everything by 2 for whole numbers.

Final Balanced Equation:

• 2 C₄H₁₀ + 13 O₂ → 8 CO₂ + 10 H₂O

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Example 3: Aluminum and Hydrochloric Acid

Reaction: Al + HCl → AlCl₃ + H₂

1. Balance Chlorine (Cl):
   • 3 Cl on right, put 3 in front of HCl, but this gives odd H.
   • Multiply everything by 2, use 6 HCl, need 2 AlCl₃ and 3 H₂.

Final Balanced Equation:

• 2 Al + 6 HCl → 2 AlCl₃ + 3 H₂

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Example 4: Gallium and Copper Bromide

Reaction: Ga + CuBr → GaBr₃ + Cu

1. Balance Bromine (Br):

   • 2 Br on left, 3 on right; LCM is 6.
   • Put 3 in front of CuBr, 2 in front of GaBr₃.

2. Balance Copper (Cu):

   • 3 Cu on left, add 3 in front of Cu.

Final Balanced Equation:

• 2 Ga + 3 CuBr → 2 GaBr₃ + 3 Cu

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Example 5: Iodine and Fluorine

Reaction: I₂ + F₂ → IF₇

1. Balance Fluorine (F):

   • 2 F on left, 7 on right; LCM is 14.
   • Put 7 in front of IF₇ and 2 in front of F₂.

2. Iodine (I) is already balanced.

Final Balanced Equation:

• I₂ + 7 F₂ → 2 IF₇

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Example 6: Sulfur Dioxide and Oxygen

Reaction: SO₂ + O₂ → SO₃

1. Balance Oxygen (O):
   • 4 O on left, 3 on right; use fraction.
   • Multiply by 2 for final equation.

Final Balanced Equation:

• 2 SO₂ + O₂ → 2 SO₃

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Example 7: Sodium and Sulfur

Reaction: Na + S₈ → Na₂S

1. Balance Sulfur (S):

   • 8 S on left, need 8 on right, put 8 in front of Na₂S.

2. Balance Sodium (Na):

   • 16 Na needed (8 S); put 16 in front of Na.

Final Balanced Equation:

• 16 Na + S₈ → 8 Na₂S

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Example 8: Sodium Phosphate and Magnesium Chloride

Reaction: Na₃PO₄ + MgCl₂ → NaCl + Mg₃(PO₄)₂

1. Balance Phosphate (PO₄):

   • 2 PO₄ on right, put 2 in front of Na₃PO₄.

2. Balance Sodium (Na):

   • Put 6 in front of NaCl.

3. Balance Magnesium (Mg):

   • Put 3 in front of MgCl₂.

Final Balanced Equation:

• 2 Na₃PO₄ + 3 MgCl₂ → 6 NaCl + Mg₃(PO₄)₂

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Example 9: Potassium Sulfate and Aluminum Chloride

Reaction: K₂SO₄ + AlCl₃ → KCl + Al₂(SO₄)₃

1. Balance Sulfate (SO₄):

   • Put 3 in front of K₂SO₄.

2. Balance Aluminum (Al):

   • Put 2 in front of AlCl₃.

3. Balance Chlorine (Cl):

   • Put 6 in front of KCl.

Final Balanced Equation:

• 3 K₂SO₄ + 2 AlCl₃ → 6 KCl + Al₂(SO₄)₃

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Example 10: Ammonia and Oxygen

Reaction: NH₃ + O₂ → NO + H₂O

1. Balance Hydrogen (H):

   • Use 3 in front of H₂O for 6 H.

2. Balance Nitrogen (N):

   • Put 2 in front of NO.

3. Balance Oxygen (O):

   • Use fraction, then multiply everything by 2.

Final Balanced Equation:

• 4 NH₃ + 5 O₂ → 4 NO + 6 H₂O

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Example 11: Combustion of Ethanol

Reaction: C₂H₅OH + O₂ → CO₂ + H₂O

1. Balance Carbon (C):

   • Put 2 in front of CO₂.

2. Balance Hydrogen (H):

   • Put 3 in front of H₂O.

3. Balance Oxygen (O):

   • Calculate and put 3 in front of O₂.

Final Balanced Equation:

• C₂H₅OH + 3 O₂ → 2 CO₂ + 3 H₂O

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Conclusion

• Balancing equations ensures conservation of mass.
• Practice with different types of reactions to improve skills.