Measuring the amounts of chemicals in solutionsCalculating concentrations - Higher
Quantitative analysis is used by chemists to make measurements and calculations. Alkalis neutralise acids to make salts and water. Their concentration can be analysed using titrations.
It is often more useful to know the concentrationA measure of the mass or amount of solute dissolved in a given volume of solvent or solution. of a reactantA substance that reacts together with another substance to form products during a chemical reaction. in moleThe amount of substance that contains the same number of particles as there are atoms in 12 g of carbon-12 (contains the Avogadro's constant 6.0 ×10²³ number of particles)./dm3 as this relates more easily to reacting ratios.
Concentration using moles
The concentration of a solution can be calculated using:
the number of moles of dissolvedA substance is said to be dissolved when it breaks up and mixes completely with a solvent to produce a solution.soluteThe dissolved substance in a solution., mol
the volume of solution (or solventThe liquid in which the solute dissolves to form a solution.) in cubic decimetres, dm3
The units for concentration are also shown as mol dm-3 or M (for ‘molar’), but this means the same as moles/dm3.
Question
0.5 moles of sodium hydroxide is dissolved in 2 dm3 of water. Calculate the concentration of the sodium hydroxide solution formed.
