A bit more on solutions

The Solutions part of this course outline is pretty similar to the stuff we did in Year 11, so you can visit my old post on solutions for a refresher.

There are a couple of things that I didn't explicitly mention there, however, so I will mention them here.

Concentration Calculations

Concentration of substances is represented using a variety of measurements, such as moles per litre, grams per litre, parts per million etc. Here's how to calculate the concentration:

mol/L: Divide number of moles by number of litres. (Makes perfect sense when you consider that a forward slash is also considered to be a divide sign on some computers/calculators.)
g/L: Divide number of grams by number of litres.
ppm (parts per million): Divide number of milligrams of solute by the number of kilograms of solvent.
Percentage composition by mass: See my post on simple chemistry calculations.

Concentration of ions in solution for strong electrolytes

This is easy. Since strong electrolytes completely ionise, the concentration of the ions in solution is the same as the concentration of the strong electrolyte.

Calculation of concentration and volume in dilution and addition of solutions

For this we use a nifty formula: C₁V₁ = C₂V₂, where C₁ = concentration of initial solution, V₁ = volume of initial solution, C₂ = concentration of final solution and V₂ = volume of final solution.

This works because the number of moles of the solute isn't changing when you dilute a solution: it's only the concentration that is. You see, the good ol' concentration formula C = n/V can be rearranged to n = CV. Now, C and V might be different for the initial solution and the final solution, but n is the same.