Key points
- Molarity relates moles of solute to litres of solution.
- Dilution calculations assume the amount of solute stays constant.
- pH is logarithmic, so a one-unit change is a tenfold change in hydrogen ion concentration.
What molarity measures
Molarity is the number of moles of solute per litre of solution. It is not the same as grams per litre unless molar mass has been used to convert mass into moles. The volume is the final solution volume, not always the amount of solvent added at the start.
The logic of dilution
A simple dilution calculation assumes the amount of solute remains the same while the volume changes. That is why the common relationship uses starting concentration and volume on one side, and final concentration and volume on the other. The model is simple, so it depends on careful units and appropriate lab technique.
Why pH feels different
pH uses a logarithmic scale. A move from pH 4 to pH 3 is not a one-unit linear increase in acidity. It represents a tenfold change in hydrogen ion concentration. This makes pH compact and useful, but it also makes mental comparisons less intuitive than ordinary percentages.
Practical checks
Use litres for molarity unless a formula clearly states otherwise, keep significant figures realistic and label stock and final solutions clearly. For safety-critical, clinical or regulated work, a web calculator is only a checking aid. Follow the relevant protocol and qualified supervision.
Related calculators
Put the guide into practice
Open the calculators that match this topic and test the numbers with your own inputs.