Balance Chemical Equation Calculator
Balance chemical equations with step-by-step explanations, proper subscripts, atom-count checks, coefficient ratios, and conservation-of-mass verification. For redox reactions, use the acidic or basic solution mode to balance atoms, charge, electrons, H+, OH−, and H2O.
Background
A balanced equation must conserve atoms. Redox reactions also need charge balance, because electrons are transferred between oxidation and reduction half-reactions. This calculator is designed to help students see both the final answer and the logic behind it.
How to use this calculator
- Choose Standard atom balancing for most molecular equations.
- Choose Redox acidic or Redox basic for ionic redox equations.
- Use =, ->, or → between reactants and products.
- For ions, write charges as Fe^2+, SO4^2-, MnO4^-, or e-.
- Review the atom and charge checks to confirm the equation is balanced.
How this calculator works
- In standard mode, each compound receives an unknown coefficient.
- The calculator creates conservation equations for each element.
- It solves the system and reduces the result to the smallest whole-number coefficients.
- In redox mode, the calculator also accounts for charge conservation and electron transfer.
- For acidic redox reactions, H+ and H2O may be added.
- For basic redox reactions, OH− and H2O may be added.
Formula & Equations Used
Atom conservation: atoms of each element on reactants = atoms of each element on products
Charge conservation for ionic equations: total charge on reactants = total charge on products
Redox electron cancellation: electrons lost by oxidation = electrons gained by reduction
Example Problems & Step-by-Step Solutions
Example 1 — Standard balancing
Balance Fe + O2 = Fe2O3.
- Assign coefficients: a Fe + b O2 = c Fe2O3.
- Balance iron: a = 2c.
- Balance oxygen: 2b = 3c.
- Use the smallest whole numbers: 4 Fe + 3 O2 → 2 Fe2O3.
Example 2 — Redox in acidic solution
Balance MnO4^- + Fe^2+ = Mn^2+ + Fe^3+.
- Identify the reduction half-reaction: permanganate becomes Mn2+.
- Identify the oxidation half-reaction: Fe2+ becomes Fe3+.
- Balance oxygen with H2O and hydrogen with H+.
- Balance charge with electrons.
- Multiply half-reactions so electrons cancel.
- The acidic solution result is MnO4^- + 5 Fe^2+ + 8 H^+ → Mn^2+ + 5 Fe^3+ + 4 H2O.
Example 3 — Redox in basic solution
For basic redox reactions, the calculator can add OH− to neutralize H+ and simplify water on both sides.
Frequently Asked Questions
Q: What is the difference between standard and redox balancing?
Standard balancing checks atom conservation. Redox balancing also checks charge conservation and electron transfer.
Q: Can I change subscripts to balance an equation?
No. Changing subscripts changes the identity of the compound. Only coefficients should be changed.
Q: How should I enter ionic charges?
Use formats like Fe^2+, Fe^3+, MnO4^-, Cr2O7^2-, SO4^2-, OH^-, H^+, and e-.
Q: What does acidic redox mode add?
Acidic redox mode may add H+, H2O, and electrons while balancing the half-reactions.
Q: What does basic redox mode add?
Basic redox mode may add OH-, H2O, and electrons while balancing the half-reactions.
Q: Does the calculator reduce coefficients?
Yes. The final result is reduced to the smallest whole-number coefficient ratio whenever possible.
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