Balancing Chemical Equations — 80 Practice Problems

Practice balancing chemical equations with 80 problems across 4 difficulty levels. Enter coefficients in the boxes, click Check to verify your answer, or Show to reveal the solution. Each equation links to the equation balancer for a step-by-step breakdown.

Score: 0 / 80 correct

Level 1 — Simple (Synthesis & Decomposition)

1. H2 + O2 → H2O Try in Balancer →
2. N2 + H2 → NH3 Try in Balancer →
3. Fe + O2 → Fe2O3 Try in Balancer →
4. Na + Cl2 → NaCl Try in Balancer →
5. Ca + O2 → CaO Try in Balancer →
6. Mg + N2 → Mg3N2 Try in Balancer →
7. Al + O2 → Al2O3 Try in Balancer →
8. K + Br2 → KBr Try in Balancer →
9. Li + H2O → LiOH + H2 Try in Balancer →
10. P4 + O2 → P2O5 Try in Balancer →
11. C + O2 → CO2 Try in Balancer →
12. S + O2 → SO2 Try in Balancer →
13. Ba + O2 → BaO Try in Balancer →
14. Zn + HCl → ZnCl2 + H2 Try in Balancer →
15. Ca(OH)2 → CaO + H2O Try in Balancer →
16. KClO3 → KCl + O2 Try in Balancer →
17. H2O2 → H2O + O2 Try in Balancer →
18. NaN3 → Na + N2 Try in Balancer →
19. HgO → Hg + O2 Try in Balancer →
20. Mg + HCl → MgCl2 + H2 Try in Balancer →

Level 2 — Intermediate (Single & Double Replacement)

21. Fe + CuSO4 → FeSO4 + Cu Try in Balancer →
22. AgNO3 + NaCl → AgCl + NaNO3 Try in Balancer →
23. CH4 + O2 → CO2 + H2O Try in Balancer →
24. C3H8 + O2 → CO2 + H2O Try in Balancer →
25. Al + HCl → AlCl3 + H2 Try in Balancer →
26. Na2CO3 + HCl → NaCl + H2O + CO2 Try in Balancer →
27. CaCO3 + HCl → CaCl2 + H2O + CO2 Try in Balancer →
28. Fe2O3 + C → Fe + CO2 Try in Balancer →
29. NaOH + H2SO4 → Na2SO4 + H2O Try in Balancer →
30. BaCl2 + Na2SO4 → BaSO4 + NaCl Try in Balancer →
31. Pb(NO3)2 + KI → PbI2 + KNO3 Try in Balancer →
32. Cu + AgNO3 → Cu(NO3)2 + Ag Try in Balancer →
33. FeCl3 + NaOH → Fe(OH)3 + NaCl Try in Balancer →
34. Al2O3 + H2SO4 → Al2(SO4)3 + H2O Try in Balancer →
35. Zn + CuSO4 → ZnSO4 + Cu Try in Balancer →
36. KOH + H3PO4 → K3PO4 + H2O Try in Balancer →
37. Ca(OH)2 + H3PO4 → Ca3(PO4)2 + H2O Try in Balancer →
38. Na + H2O → NaOH + H2 Try in Balancer →
39. Mg(OH)2 + HCl → MgCl2 + H2O Try in Balancer →
40. FeS2 + O2 → Fe2O3 + SO2 Try in Balancer →

Level 3 — Advanced (Combustion & Redox)

41. C6H12O6 + O2 → CO2 + H2O Try in Balancer →
42. C2H5OH + O2 → CO2 + H2O Try in Balancer →
43. Fe2O3 + CO → Fe + CO2 Try in Balancer →
44. KMnO4 + HCl → KCl + MnCl2 + H2O + Cl2 Try in Balancer →
45. Cu + HNO3 → Cu(NO3)2 + NO + H2O Try in Balancer →
46. C4H10 + O2 → CO2 + H2O Try in Balancer →
47. Al + Fe2O3 → Al2O3 + Fe Try in Balancer →
48. NH3 + O2 → NO + H2O Try in Balancer →
49. Ca3(PO4)2 + SiO2 + C → CaSiO3 + P4 + CO Try in Balancer →
50. Cr2O3 + Al → Al2O3 + Cr Try in Balancer →
51. P4O10 + H2O → H3PO4 Try in Balancer →
52. C5H12 + O2 → CO2 + H2O Try in Balancer →
53. MnO2 + HCl → MnCl2 + Cl2 + H2O Try in Balancer →
54. Mg + Fe2O3 → MgO + Fe Try in Balancer →
55. NH4NO3 → N2O + H2O Try in Balancer →
56. C7H16 + O2 → CO2 + H2O Try in Balancer →
57. FeSO4 + K2Cr2O7 + H2SO4 → Fe2(SO4)3 + Cr2(SO4)3 + K2SO4 + H2O Try in Balancer →
58. C8H18 + O2 → CO2 + H2O Try in Balancer →
59. SnO2 + C → Sn + CO2 Try in Balancer →
60. Mn2O7 → MnO2 + O2 Try in Balancer →

Level 4 — Challenge (Complex Stoichiometry)

61. K2Cr2O7 + FeSO4 + H2SO4 → Cr2(SO4)3 + Fe2(SO4)3 + K2SO4 + H2O Try in Balancer →
62. Ca10(PO4)6(OH)2 + H3PO4 → Ca(H2PO4)2 + H2O Try in Balancer →
63. (NH4)2Cr2O7 → Cr2O3 + N2 + H2O Try in Balancer →
64. K4[Fe(CN)6] + H2SO4 + H2O → K2SO4 + FeSO4 + (NH4)2SO4 + CO Try in Balancer →
65. Cu3(PO4)2 + H2SO4 → CuSO4 + H3PO4 Try in Balancer →
66. Al(OH)3 + H2SO4 → Al2(SO4)3 + H2O Try in Balancer →
67. Fe3O4 + H2 → Fe + H2O Try in Balancer →
68. Ca3(PO4)2 + H2SO4 → CaSO4 + H3PO4 Try in Balancer →
69. Sb2S3 + HCl → SbCl3 + H2S Try in Balancer →
70. C6H12O6 → C2H5OH + CO2 Try in Balancer →
71. P4 + HNO3 + H2O → H3PO4 + NO Try in Balancer →
72. Cu2S + O2 → Cu2O + SO2 Try in Balancer →
73. Na2CO3 + C + N2 → NaCN + CO Try in Balancer →
74. Bi2O3 + C → Bi + CO2 Try in Balancer →
75. V2O5 + HCl → VOCl3 + H2O Try in Balancer →
76. Hg2CO3 → Hg + HgO + CO2 Try in Balancer →
77. SiCl4 + H2O → SiO2 + HCl Try in Balancer →
78. TiCl4 + Mg → Ti + MgCl2 Try in Balancer →
79. WO3 + H2 → W + H2O Try in Balancer →
80. Fe3C + O2 → Fe2O3 + CO2 Try in Balancer →

Frequently Asked Questions

How do you balance a chemical equation?

Count atoms of each element on both sides, then adjust coefficients (the numbers in front of formulas) until atoms are equal on both sides. Start with the most complex molecule and leave hydrogen and oxygen for last. Never change subscripts — only coefficients.

What are the steps to balance equations?

1) Write the unbalanced equation. 2) List all elements present. 3) Count atoms per element on each side. 4) Add coefficients to equalize atoms, starting with elements that appear in only one compound per side. 5) Verify conservation of mass — total atoms of each element must match.

Why must chemical equations be balanced?

The law of conservation of mass requires that atoms are neither created nor destroyed in a chemical reaction. A balanced equation shows the same number and type of atoms on both sides, reflecting this fundamental law.

What is the hardest type of equation to balance?

Redox (oxidation-reduction) equations are typically the hardest, especially those involving polyatomic ions or multiple oxidation state changes (like Level 3 & 4 in this worksheet). The half-reaction method or algebraic method (Gaussian elimination) can help with complex cases. Our equation balancer uses Gaussian elimination to solve any equation automatically.

Related Tools

All equations in this worksheet are balanced using the same Gaussian elimination algorithm as the equation balancer. Solutions are verified to conserve mass for every element.

Conversion factors verified against NIST, BIPM Based on SI definitions (BIPM). Last reviewed: March 2026
Adilson Fernandes By Adilson Fernandes
Tiago Fernandes Reviewed by Tiago Fernandes