Concentration of Solutions

Concentration in g/dm³

• Concentration is the amount of solute in a given volume of solution
• It can be measured as mass per volume, in g/dm³

$$\text{concentration (g/dm}^3) = \frac{\text{mass of solute (g)}}{\text{volume of solution (dm}^3)}$$

• 1 dm³ $=$ 1000 cm³, so convert cm³ to dm³ by dividing by 1000
• Worked example: 8 g of sodium hydroxide dissolved to make 250 cm³ of solution. $250 \text{ cm}^3 = 0.25 \text{ dm}^3$, so the concentration is $\frac{8}{0.25} = 32$ g/dm³
• Worked example: mass of solute in 50 cm³ of a 20 g/dm³ solution: $20 \times 0.05 = 1$ g
• (HT) A greater mass of solute in the same volume means a higher concentration; the same mass in a larger volume means a lower one. Adding water dilutes a solution