Concentrations of Solutions | Chemistry for Grade 10 PDF Download

Expressing Concentration

• A solid substance that dissolves in a liquid is called a solute, the liquid is called a solvent and the two when mixed together form a solution
• Most chemical reactions occur between solutes which are dissolved in solvents, such as water or an organic solvent
• Concentration simply refers to the amount of solute there is in a specific volume of the solvent
• The greater the amount of solute in a given volume, the greater the concentration
• A general formula for concentration is thus:
  
• Concentration can be measured in grams per cubic decimetre
• 1 decimetre cubed (dm³) = 1000 cm³
  • 1 decimetre cubed (dm³) is the same as 1 litre
• You may be given data in a question which needs to be converted from cm³ to dm³ or the other way around
  • To go from cm³ to dm³ :
    • Divide by 1000
  • To go from dm³ to cm³ :
    • Multiply by 1000

Calculating Concentration in Mass per Volume

• To calculate the concentration of a solution in terms of mass per unit volume, you need to
  • Identify the solute and solvent
  • Convert the volume units into decimetres cubed
  • Divide the mass of the solute by the volume of the solution in decimetres cubed

Worked Example

Exam Tip

Be careful when doing volume unit conversions as it is easy to multiply instead of dividing by 1000 and vice-versa. Always ask yourself - is the result going to be a bigger or smaller number than I started with? Do I get more or fewer cubic decimetres when I convert from cubic centimetres?