Chemical Equation Examples in Chemistry

Start with the recap, study the fully worked examples, then use the practice problems to check your understanding of Chemical Equation.

This page combines explanation, solved examples, and follow-up practice so you can move from recognition to confident problem-solving in Chemistry.

Concept Recap

A written representation of a chemical reaction using chemical formulas for reactants and products, coefficients to indicate mole ratios, state symbols to show physical states.

A recipe that shows what goes in, what comes out, and in what amounts.

Read the full concept explanation →

How to Use These Examples

  • Read the first worked example with the solution open so the structure is clear.
  • Try the practice problems before revealing each solution.
  • Use the related concepts and background knowledge badges if you feel stuck.

What to Focus On

Core idea: Equations must be balanced—same number of each atom on both sides.

Common stuck point: Coefficients show mole ratios, not absolute amounts — you can scale them up or down freely.

Sense of Study hint: When writing a chemical equation, follow these steps in order. First write the correct chemical formulas for all reactants on the left and products on the right, separated by an arrow. Then add state symbols — (s), (l), (g), (aq) — after each formula. Finally, adjust coefficients so each element has equal atoms on both sides.

Common Mistakes to Watch For

Before you work through the examples, skim the mistake guide so you know which shortcuts and sign errors to avoid.

Balancing Equations Mistakes

Worked Examples

Example 1

easy
What information does a balanced chemical equation convey? Explain using 2\text{H}_2 + \text{O}_2 \rightarrow 2\text{H}_2\text{O} as an example.

Solution

  1. 1
    A chemical equation shows: (1) the reactants (left side: \text{H}_2, \text{O}_2) and products (right side: \text{H}_2\text{O}).
  2. 2
    (2) The coefficients show mole ratios: 2 mol \text{H}_2 reacts with 1 mol \text{O}_2 to produce 2 mol \text{H}_2\text{O}.
  3. 3
    (3) The equation is balanced — same number of each type of atom on both sides (H: 4=4, O: 2=2), satisfying conservation of mass.

Answer

\text{Shows reactants, products, mole ratios, and conserved atoms}
A balanced chemical equation is a quantitative recipe for a chemical reaction. It tells us what reacts, what is produced, and in what proportions, all while obeying the law of conservation of mass.

Example 2

medium
Interpret the following chemical equation including state symbols: \text{Na}_2\text{CO}_3\text{(s)} + 2\text{HCl(aq)} \rightarrow 2\text{NaCl(aq)} + \text{H}_2\text{O(l)} + \text{CO}_2\text{(g)}. What does each state symbol mean?

Practice Problems

Try these problems on your own first, then open the solution to compare your method.

Example 1

medium
Write a balanced chemical equation with state symbols for the reaction of solid iron with oxygen gas to form solid iron(III) oxide.

Example 2

hard
A student writes the following unbalanced equation for the reaction of aluminum with sulfuric acid: \text{Al} + \text{H}_2\text{SO}_4 \rightarrow \text{Al}_2(\text{SO}_4)_3 + \text{H}_2. Balance this equation and verify by counting all atoms on each side.
← Back to Chemical Equation Common Mistakes Practice Mode

Background Knowledge

These ideas may be useful before you work through the harder examples.

reactantproductmolecular formula