Example 1 — Combustion
Unbalanced: \( \mathrm{C_3H_8 + O_2 \rightarrow CO_2 + H_2O} \). Balance C: \(3\,\mathrm{CO_2}\); H: \(4\,\mathrm{H_2O}\); then O: \(5\,\mathrm{O_2}\). Final: \( \boxed{\mathrm{C_3H_8 + 5O_2 \rightarrow 3CO_2 + 4H_2O}} \).
Balances chemical equations using linear algebra and half-reactions, enforcing atom and charge conservation, smallest integers, and helpful, stepwise previews online.
A Balance Chemical Equations Calculator automatically finds the smallest whole-number coefficients that make a chemical equation obey the conservation of atoms (and charge, when ionic species appear). Balancing ensures the same count of each element appears on both sides of the arrow, reflecting matter conservation in reactions. The calculator accepts unbalanced formulas with physical states if provided, analyzes the elements present, and returns coefficients that satisfy all constraints. For redox reactions, it can apply the half-reaction method (acidic or basic medium), guaranteeing both mass and electron balance. Clear equation previews help learners see how coefficients distribute across molecules, polyatomic ions, and ionic charges, while notes emphasize that subscripts in formulas never change—only the integer coefficients do.
Under the hood, balancing can be cast as a homogeneous linear system. Let the element–species matrix \(A\) contain, in each column, the atom counts of a species (reactants with negative sign, products positive). A nontrivial solution \( \mathbf{x}\ne\mathbf{0} \) to \(A\mathbf{x}=\mathbf{0}\) gives coefficients; scaling by the greatest common divisor yields the smallest integers. For ionic equations, an additional row tracks net charge. Alternatively, for oxidation–reduction, the half-reaction approach separates oxidation and reduction, balances atoms other than O and H, then uses \( \mathrm{H_2O} \), \( \mathrm{H^+} \) (acid) or \( \mathrm{OH^-} \) (base), and electrons \(e^- \) to enforce mass and charge, finally combining the halves to cancel electrons. The tool highlights polyatomic “as a unit” shortcuts and suggests fractional-oxygen tactics (then multiply to clear fractions) for combustion problems.
C3H8 + O2 → CO2 + H2O). Include charges for ionic species, states optional.Atom/charge conservation (algebraic method): \[ A\,\mathbf{x}=\mathbf{0},\quad \mathbf{x}\in\mathbb{Z}_{\ge 0}\setminus\{\mathbf{0}\};\qquad \mathbf{x}_{\min}=\frac{\mathbf{x}}{\gcd(\mathbf{x})}. \]
Half-reaction electron balance: \[ \text{Oxidation: } \nu_\text{ox}\text{ (e.g., Fe}^{2+}\to\text{Fe}^{3+}+e^-),\qquad \text{Reduction: } \nu_\text{red}\text{ (e.g., MnO}_4^-+5e^-\to\text{Mn}^{2+}). \]
Acidic/basic adjustments: \[ \text{Acidic: add }\mathrm{H^+},\ \mathrm{H_2O};\qquad \text{Basic: add }\mathrm{OH^-},\ \mathrm{H_2O},\ \text{then cancel } \mathrm{H^+H^-}\Rightarrow \mathrm{H_2O}. \]
Unbalanced: \( \mathrm{C_3H_8 + O_2 \rightarrow CO_2 + H_2O} \). Balance C: \(3\,\mathrm{CO_2}\); H: \(4\,\mathrm{H_2O}\); then O: \(5\,\mathrm{O_2}\). Final: \( \boxed{\mathrm{C_3H_8 + 5O_2 \rightarrow 3CO_2 + 4H_2O}} \).
\( \mathrm{Fe^{2+} + MnO_4^- \rightarrow Fe^{3+} + Mn^{2+}} \) in acid. Balanced: \( \boxed{\mathrm{5Fe^{2+} + MnO_4^- + 8H^+ \rightarrow 5Fe^{3+} + Mn^{2+} + 4H_2O}} \).
\( \mathrm{Cl_2 + OH^- \rightarrow Cl^- + ClO^- + H_2O} \). Balanced: \( \boxed{\mathrm{Cl_2 + 2OH^- \rightarrow Cl^- + ClO^- + H_2O}} \).
\( \mathrm{Na_3PO_4 + CaCl_2 \rightarrow NaCl + Ca_3(PO_4)_2} \). Balanced: \( \boxed{\mathrm{2Na_3PO_4 + 3CaCl_2 \rightarrow 6NaCl + Ca_3(PO_4)_2}} \).
Balance C and H first, then O. Allow fractional \( \mathrm{O_2} \) temporarily, then multiply all coefficients to clear fractions.
Intermediate fractions are fine; the final balanced equation should use the smallest whole numbers (divide by gcd).
Coefficients scale entire species; subscripts are fixed by chemical identity and must never be altered to balance.
Balance atoms and charge. Use the half-reaction method with \( \mathrm{H^+} \)/\( \mathrm{OH^-} \) and \( \mathrm{H_2O} \) as appropriate.
They don’t affect balancing arithmetic but are important for communicating reaction conditions.
Use acidic when \( \mathrm{H^+} \) is present; basic when \( \mathrm{OH^-} \) is present. The medium dictates balancing species.
The nullspace gives proportional coefficients. Scale to the smallest integers by dividing by the gcd of components.
Yes, if the same polyatomic appears unchanged on both sides; it speeds balancing without breaking into atoms.
Count each element on both sides and check net charge equality (for ionic equations). Both must match.
With unusual inputs, multiple basis solutions can appear; any positive integer linear combination that preserves ratios is valid.
No. Balancing only enforces stoichiometry; mechanisms require kinetic/experimental evidence.
They represent mole ratios, enabling limiting-reagent analysis, theoretical yield, and percent yield calculations.