mass
'no magic to the mole'
amount
molar mass
concentration
solution volume
gas volume
molar gas volume
Avogadro
constant, L
number of
entities, N
Now try the following question.
F5. STANDARD SOLUTIONS
Quantitative analysis is concerned with determining the amounts of known substances present in a sample of material. One of the most important and powerful techniques in this field is titrimetric analysis, used widely by chemists in many different disciplines. In titrimetric analysis, the volumes of solutions of reacting substances are measured using burettes and pipettes.
The analysis is completed by determining the volume of a standard solution needed to react completely with the analyte (substance of unknown concentration).
A standard solution is one of known identity and of precisely known concentration.
For school-based Chemistry courses this usually implies three significant figures, corresponding to the limitations of a typical electronic top-pan balance employed to measure the masses of the corresponding solid ingredients. Note that for the IB & AP, molar masses are usually required to 2 d.p.
A known concentration of solution can either by prepared according to a given recipe or its value determined by analysis. In solutions where no solvent is specified, water is assumed. In preparing standard aqueous solutions, de-ionized or distilled water is used.
The symbolism ‘M’ is too often seen used as short-hand for the derived amount-concentration unit
is far from obsolete however, remaining a unit of choice for practising chemists, biomedical scientists, physicians, teachers and instructors, particularly in the USA. There are good reasons, no doubt.