Concentration Calculator

How strong is the solution?

Stir one spoon of salt into a glass of water and it tastes mild; stir in ten and it is far stronger. Chemists measure this strength as concentration: how much solute is dissolved in a given volume of solution. This module shows what concentration means, the units it uses, and how to calculate it.

Concentration words to know

Learn these before you do the calculations.

Strong against weak

The same volume can hold very different amounts of solute.

Mass over volume

To find a concentration in g/dm3, divide the mass of solute in grams by the volume of solution in cubic decimetres. So 30 g dissolved in 3 cubic decimetres gives a concentration of 10. Remember: adding more solute raises the concentration, while adding more solvent lowers it.

Match the term

Match the change

How is concentration found?

How do you calculate the concentration of a solution in g/dm3?

• Divide the mass of solute by the volume of solution.
• Multiply the mass by the volume.
• Add the mass and the volume.
• Just use the mass on its own.

Raising the concentration

Select the TWO changes that make a solution more concentrated.

• Dissolving more solute in the same volume
• Letting some of the solvent evaporate
• Adding more water
• Stirring it for longer

Work out the concentration

A solution contains 20 g of solute dissolved in 2 cubic decimetres of solution. Divide the mass by the volume to find the concentration. What is the answer?

Order the calculation

Put the steps of finding a concentration in order, earliest first.

• Measure the mass of solute
• Measure the volume of solution
• Divide the mass by the volume
• Give the answer in g/dm3

Complete the rules

Concentration is the mass of _____ dissolved in a given volume of solution, measured in _____. You work it out by dividing the mass by the _____. Adding more solvent makes the solution more _____.

Spot what you need

To work out a concentration in g/dm3, tap the TWO quantities you must know.

• the mass of solute
• the volume of solution
• the colour of the solution
• the room temperature

Judge the solution

Read each case and choose the best answer.

• Two beakers hold the same volume, but one has twice as much salt dissolved. Which is more concentrated?
• You pour more pure water into a solution without adding solute. What happens to the concentration?
• You have 30 g of solute in 3 cubic decimetres of solution. What is the concentration in g/dm3?

Explain concentration

Explain what the concentration of a solution means, how it is calculated, and what changes it.

• Say what concentration measures and its units
• Explain how to calculate it from mass and volume
• Explain one change that raises it and one that lowers it