Chemical Quantities: Concentrations of Solutions

Learning about concentrations of solutions begins with understanding the definition of concentration. In general, concentration pertains to the amount of solute present in a particular volume of solution.
The fundamental unit of concentration is moles per cubic decimetre (mol/dm³).
The molar concentration can be found using the formula: concentration = moles/volume. However, the volume should always be in cubic decimetres.
The problem for calculations may often provide the volume in millilitres (ml) or litres (L), so conversion to cubic decimetres might be necessary. Note that 1 dm³ is equal to 1 litre or 1000ml.
Concentration of a solution can increase by adding more solute or by evaporating the solvent, and it can decrease by adding more solvent or diluting the solution.
To dilute a solution means to decrease its concentration by adding more solvent without adding more solute.
The process of diluting a solution can be summarised by the equation: C₁V₁ = C₂V₂, where C₁ is the initial concentration, V₁ is the initial volume, and C₂ and V₂ are the final concentration and volume.
It’s also important to understand percentage solutions, which are another way of expressing the concentration. A solution that is called a “10% solution” would contain 10g of solute for every 100g of solution.
Techniques like titration can be used to measure the concentration of a solution. Titration involves the controlled addition of a solution of known concentration to a solution of unknown concentration until the reaction between them is just complete.
Knowledge of stoichiometry, or the ratio of reactants in a balanced chemical equation, is essential to calculate concentrations in titration experiments.
A mole is the amount of pure substance containing the same number of chemical units (atoms, molecules, ions, electrons, or other specified groups or particles) as exactly 12 grams of carbon-12.
The balancing numbers in a chemical equation show the ratio of moles of reactants and products. Using these ratios, you can work out the quantities of reactants and products in a reaction.
Practice with a variety of problems involving concentration and solution measurements. This will not only reinforce your understanding of the principles but will also prepare you for potential question variations.