In this lesson, we will learn:
- To apply our understanding of moles calculations to solutions.
- To understand the difference between molarity, moles, and mass.
- To be able to calculate molarity of chemicals dissolved in solution.
- To be able to calculate amounts of substance from titration problems.
- You cannot use the molar volume of gas constant (22.4 L / mol at STP) if your question is about a solution or is not at standard temperature and pressure (STP). It is only used when dealing with gases at STP.
- The same goes for RTP molar volume if not at RTP.
- Molarity means concentration, for chemists - it means the number of moles of a chemical per amount of volume. For example, in a given volume of solution.
- Units of concentration are abbreviated "M". It means moles per litre, written mol / L or mol L or moles per cubic decimeters, written mol / dm or mol dm.
- Square brackets, e.g. [HCl] are used to show that the concentration of a chemical. For example you could write [HCl] = 0.1 mol dm-3.
- You can use the formula to find concentration, where = number of moles and is volume (in liters, L, or cubic decimeters, written dm). You can re-arrange for .
- A titration is an experiment used to find out the unknown concentration of an acid by reacting it with a base of known concentration, or vice versa (unknown base with known acid). This lesson covers calculations using data from titration experiments, not the titration experiment (see Acid-base titration for this).
- When answering molar concentration questions, if given a volume make sure you convert your units if you need to. Volume is often given in mL but concentration is measured in moles per litre or moles per cubic decimeter, which has the same value.