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.
F9. QUANTITATIVE DILUTION OF SOLUTIONS
It is common practice in the laboratory to make a dilution from a more concentrated starting solution, termed the stock solution, by the addition of more solvent. For all aqueous solutions, distilled water, rather than tap water, should be used unless, depending upon the procedure(s) involved, de-ionised water proves to be a satisfactory but more economical alternative.
Quantitative dilution might be important in order to:
-
make a solution of specified concentration for a particular procedure from a standard solution;
-
dilute an unknown sample prior to analysis to give a concentration suitable for titration;
-
perform a serial dilution.
As a solution is diluted, the chemical amount of solute remains the same, but as it disperses through
a larger volume, the concentration is decreased. In other words, the chemical amount, n is a constant, and as n = c V, c V must be constant throughout dilution. So, it follows that
diluted concentration and volume. The arithmetic is straightforward.
In accurate work, dilution should be carried out using titrimetric - aka volumetric - flasks so the final volume of the solution is measured, taking account of volume changes on mixing that may occur with dilution.
