A solution of sugar has a concentration of 3 g/dm3. What is the mass of sugar in 0.5 dm3 of solution?

The key to this question is understanding the relationship between concentration, mass and volume. Concentration shows how much of a substance (the mass) is packed into a space (the volume). This means that concentration (C) = Mass/VolumeWe can rearrange this relationship to see that Mass = C x V. We know that C = 3g/dm³ and the volume of the solution is 0.5dm³. So the mass of sugar is 0.5x3 = 1.5g (don't forget units!)