LET’S TRY ONE
In 2H2 + O2 → 2H2O, how many hydrogen atoms are on the left?
4
The coefficient 2 multiplies the 2 hydrogen atoms in each H2 molecule.
Learning steps & teaching tips
Use coefficients and subscripts to check conservation of each element in a simple equation.
- Count atoms within one formula unit.
- Multiply by its coefficient.
- Check each element separately; do not balance an equation by changing chemical subscripts.
Try it together
Use colored counters for H and O atoms. Model two H2 molecules plus one O2 molecule forming two H2O molecules without losing counters.
A coefficient multiplies every atom in the formula; compare each element on both sides.