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Title: Balancing Chemical Equations Worksheet with Answers (Grade 11)

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📄 Title: Balancing Chemical Equations Worksheet with Answers (Grade 11)

Practise balancing chemical equations with this free Grade 11 chemistry worksheet.

This free balancing chemical equations worksheet takes students from counting atoms to balancing combustion reactions in 27 questions, with a complete answer key.

It starts with simple equations like hydrogen and oxygen forming water, moves on to polyatomic ions and hydrocarbon combustion, and finishes with word equations, common errors and a butane challenge. Every equation has been checked atom by atom.

  • Grade 11 · SCH3U
  • 27 marks
  • 30–40 minutes
  • Answer key included

What's in This Balancing Chemical Equations Worksheet

The difficulty climbs steadily, so the same sheet works for a first lesson, homework and test review.

PartSkill practisedMarks
ACount atoms in formulas with coefficients and brackets3
BBalance basic equations8
CBalance equations with polyatomic ions6
DBalance combustion reactions3
EWrite and balance word equations3
FSpot the mistake2
GChallenge: butane combustion and conservation of mass2

It supports the Ontario SCH3U expectations in the Chemical Reactions unit, and it's a useful refresher before stoichiometry.

How to Balance a Chemical Equation in 5 Steps

The method on this balancing chemical equations worksheet works for every question on it:

  1. Count the atoms of each element on both sides of the arrow.
  2. Change coefficients only. Never change subscripts, because that changes the substance.
  3. Balance metals first, then non-metals, and leave hydrogen and oxygen for last.
  4. Treat polyatomic ions as one unit if they appear unchanged on both sides, such as SO4 or NO3.
  5. Check every element again and make sure the coefficients are in the lowest whole-number ratio.

Balancing is how chemists apply the law of conservation of mass: atoms are rearranged, never created or destroyed. If students need help with the formulas themselves, review the naming ionic compounds worksheet first.

Worked Example: Aluminum and Oxygen

Here is how to solve question 8 on the balancing chemical equations worksheet: Al + O2 → Al2O3.

  1. Oxygen: 2 on the left, 3 on the right. The lowest common multiple is 6, so put 3 in front of O2 and 2 in front of Al2O3.
  2. Aluminum: now there are 2 × 2 = 4 Al on the right, so put 4 in front of Al.
  3. Check: 4 Al and 6 O on each side. The balanced equation is 4Al + 3O2 → 2Al2O3.

Balancing Chemical Equations Practice Questions

These match the balancing chemical equations worksheet PDF. Fill in the coefficients, then check the answer key.

Part A – Count the Atoms

Count the atoms of each element.

  1. 3H2O
  2. 2Ca(NO3)2
  3. 4Al2(SO4)3

Part B – Balance: The Basics

  • 4. H2+ O2→ H2O
  • 5. N2+ H2→ NH3
  • 6. Na+ Cl2→ NaCl
  • 7. Mg+ O2→ MgO
  • 8. Al+ O2→ Al2O3
  • 9. KClO3→ KCl+ O2
  • 10. Fe+ Cl2→ FeCl3
  • 11. CH4+ O2→ CO2+ H2O

Part C – Balance: Polyatomic Ions and More

  • 12. Pb(NO3)2+ KI→ PbI2+ KNO3
  • 13. Ca(OH)2+ HCl→ CaCl2+ H2O
  • 14. Al+ CuSO4→ Al2(SO4)3+ Cu
  • 15. Na3PO4+ MgCl2→ Mg3(PO4)2+ NaCl
  • 16. H2SO4+ NaOH→ Na2SO4+ H2O
  • 17. Fe2O3+ CO→ Fe+ CO2

Part D – Combustion Reactions

  • 18. C3H8+ O2→ CO2+ H2O
  • 19. C2H6+ O2→ CO2+ H2O
  • 20. C6H12O6+ O2→ CO2+ H2O

Part E – Word Equations: Write and Balance

  1. Hydrogen gas reacts with chlorine gas to form hydrogen chloride.
  2. Zinc reacts with hydrochloric acid to form zinc chloride and hydrogen gas.
  3. Sodium reacts with water to form sodium hydroxide and hydrogen gas.

Part F – Spot the Mistake

  1. A student balances H2O → H2 + O2 by writing H2O2 → H2 + O2. What is wrong? Fix it.
  2. A student writes 4H2 + 2O2 → 4H2O. What is wrong? Fix it.

Part G – Challenge

  • 26. C4H10+ O2→ CO2+ H2O
  1. Explain how a balanced equation shows the law of conservation of mass.

Balancing Chemical Equations Worksheet Answer Key

Open each part to check your answers to the balancing chemical equations worksheet. A coefficient of 1 is shown for clarity, but it's normally left blank. The printable answer key is on pages 3–4 of the PDF.

Part A answers (Q1–3)
  1. 3H2O: H = 6, O = 3
  2. 2Ca(NO3)2: Ca = 2, N = 4, O = 12
  3. 4Al2(SO4)3: Al = 8, S = 12, O = 48
Part B answers (Q4–11)
  • 4.2H2+1O2→2H2O
  • 5.1N2+3H2→2NH3
  • 6.2Na+1Cl2→2NaCl
  • 7.2Mg+1O2→2MgO
  • 8.4Al+3O2→2Al2O3
  • 9.2KClO3→2KCl+3O2
  • 10.2Fe+3Cl2→2FeCl3
  • 11.1CH4+2O2→1CO2+2H2O
Part C answers (Q12–17)
  • 12.1Pb(NO3)2+2KI→1PbI2+2KNO3
  • 13.1Ca(OH)2+2HCl→1CaCl2+2H2O
  • 14.2Al+3CuSO4→1Al2(SO4)3+3Cu
  • 15.2Na3PO4+3MgCl2→1Mg3(PO4)2+6NaCl
  • 16.1H2SO4+2NaOH→1Na2SO4+2H2O
  • 17.1Fe2O3+3CO→2Fe+3CO2
Part D answers (Q18–20)
  • 18.1C3H8+5O2→3CO2+4H2O
  • 19.2C2H6+7O2→4CO2+6H2O
  • 20.1C6H12O6+6O2→6CO2+6H2O
Part E answers (Q21–23)
  1. H2 + Cl2 → 2HCl
  2. Zn + 2HCl → ZnCl2 + H2
  3. 2Na + 2H2O → 2NaOH + H2
Part F answers (Q24–25)
  1. Changing a subscript changes the substance (H2O2 is hydrogen peroxide). Only change coefficients: 2H2O → 2H2 + O2
  2. It balances, but coefficients must be in the lowest whole-number ratio: 2H2 + O2 → 2H2O
Part G answers (Q26–27)
  • 26.2C4H10+13O2→8CO2+10H2O
  1. Atoms are only rearranged in a reaction, not created or destroyed, so the same number of each atom (and the same total mass) appears on both sides.

5 Common Balancing Mistakes

Part F of the balancing chemical equations worksheet is built around the first two, because they're the most common.

  1. Changing subscripts. Writing H2O2 to "fix" the oxygen creates a different chemical.
  2. Not reducing. 4H2 + 2O2 → 4H2O balances, but the answer is 2H2 + O2 → 2H2O.
  3. Miscounting brackets. In Al2(SO4)3, the 3 multiplies everything inside: 3 S and 12 O.
  4. Forgetting diatomic elements. Hydrogen, oxygen, nitrogen and the halogens are written as H2, O2, N2, Cl2 and so on.
  5. Balancing O too early in combustion. Balance C, then H, then O last, because O2 appears alone and is easiest to adjust.

How to Use This Balancing Chemical Equations Worksheet in Class

As a teacher, I use it across the reactions unit:

  • First lesson: Parts A and B, with the five steps on the board.
  • Practice day: Parts C and D in pairs, comparing coefficients before checking the key.
  • Review: Parts E–G as homework, since word equations connect balancing to naming. Students who finish the whole balancing chemical equations worksheet are ready for stoichiometry.

For more practice, try the balancing chemical equations quiz and the chemical reaction types quiz, both auto-graded. To check atom counts or molar masses, see the free chemistry calculators.

Frequently Asked Questions

Is this balancing chemical equations worksheet free?

Yes. The worksheet and answer key are free to download and print as a PDF, with no account needed.

What is the easiest way to balance a chemical equation?

Count the atoms on each side, then adjust coefficients one element at a time: metals first, then non-metals, and hydrogen and oxygen last. Treat polyatomic ions that stay together as a single unit.

Why can't you change subscripts when balancing equations?

Subscripts are part of the chemical formula. Changing H2O to H2O2 turns water into hydrogen peroxide, a different substance. Only coefficients, which count molecules, can change.

Why do we balance chemical equations?

Because of the law of conservation of mass: atoms are rearranged in a reaction but never created or destroyed, so each element must have the same number of atoms on both sides.

What grade is this balancing chemical equations worksheet for?

It is written for Grade 11 chemistry (Ontario SCH3U) and also works for Grade 9–10 science extension and introductory college chemistry.

More Free Grade 11 Chemistry Resources

Ready to practise? Download the free balancing chemical equations worksheet PDF (use the Download button above), print it double-sided, and keep the answer key pages for marking.

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