Making Dilutions From Acid and Base Solutions
Objective
The aim of the first part of the experiment was to make up dilutions
from acid and base solutions and record the results after adding
various indicators. The aim of the second part of the experiment was
to determine the pH values of the dilutions using both pH paper and a
pH metre recording the results for both tests.
Procedure - Part 1
For the first part of the experiment the correct amount of solid NaOH
needed to prepare 250 cm3 of a 0.1M solution was calculated and then
weighed out in a weighing bottle using balanced scales. The weight of
the empty bottle was recorded, minus lid before adding approximately
1g of solid NaOH, re-weighing the bottle plus contents and the new
weight recorded.
The Solid NaOH was then transferred to a 200 cm3 beaker where
approximately 150 cm³ of H2O was added to it and the solution stirred
with a glass stirrer (a magnetic stirrer was not available as
specified in the laboratory manual) until the solid was completely
dissolved. The solution was then transferred, via funnel, into a 250
cm³ volumetric flask and H2O added to increase the volume to 250 cm³,
the solution was then thoroughly mixed by inversion, ensuring the
stopper was held firmly in place.
Next a 1/10 dilution was prepared from the solution using volumetric
flasks and pipettes, although because the original solution was a 0.1M
concentration it was actually already a 1/10 dilution of a 1M
concentration making the 1/10 dilution prepared a 1/100 dilution of a
1M concentration. Therefore the two dilutions of NaOH were 1/10 and
1/100 of a 1M concentration both clearly labelled.
Dilutions of 1/10 and 1/00 using labelled volumetric flasks and
pipettes were then made up from a pre-prepared 1M solution of both HCl
and CH3COOH (adding the acid to water, not the other way around).
Nine test tubes were set out and numerically labelled 1-9 and a
pipette used to transfer a); 5 cm³ of 1/100 HCl into test tubes 1-3