Balancing Chemical Equations
Atoms are conserved, so equations must balance.
About this topic
A balanced chemical equation has equal numbers of each type of atom on both sides, obeying conservation of mass. Balance by changing coefficients, never subscripts: for example, 2H2 + O2 → 2H2O. A good strategy is to balance elements that appear in only one compound first, then hydrogen and oxygen last, and finally check every atom.
Coefficients tell the ratio of particles or moles of each substance, so they feed directly into stoichiometry. State symbols show the physical state: (s) solid, (l) liquid, (g) gas and (aq) dissolved in water. Where polyatomic ions appear unchanged on both sides, balance them as one unit. If odd and even numbers cause trouble, such as oxygen in the burning of ethane, double everything to clear a fraction.
Worked example: methane burns as CH4 + O2 → CO2 + H2O. Carbon is already balanced. Hydrogen needs two water molecules, giving 2H2O, so oxygen on the right becomes 2 + 2 = 4 atoms. Put 2 in front of O2 and the equation reads CH4 + 2O2 → CO2 + 2H2O.
A major mistake is changing subscripts, which would change the substance (H2O2 is hydrogen peroxide, not water). Also reduce coefficients to the smallest whole numbers. Balanced equations are essential for predicting reactant amounts in industry, cooking-like recipes for chemists, and medicine manufacture.
Key ideas
- Same atoms each side
- Adjust coefficients not subscripts
- Check each element
Quick check
Use cases: where Balancing Chemical Equations helps
- Homework: review the key idea behind Balancing Chemical Equations before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Balancing Chemical Equations without notes.
- Visual learning: play with the interactive lab to see how Balancing Chemical Equations changes when you adjust its inputs.
- Teaching a friend: explain Balancing Chemical Equations in your own words, then compare your version with the key ideas.
Chemistry explains medicine, food, cleaning products, fuels and building materials.
Frequently asked questions
What is Balancing Chemical Equations?
Atoms are conserved, so equations must balance.
What will I learn in Balancing Chemical Equations?
Same atoms each side. Adjust coefficients not subscripts. Check each element.
Is Balancing Chemical Equations part of Chemistry?
Yes. It is one of 150 Chemistry topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Balancing Chemical Equations lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Balancing Chemical Equations?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.