SOURCE 6
Wash out the conical flask with water and then pipette another 25 cm3 of the
sodium hydroxide solution into it and add five drops of indicator. Fill up the
burette with acid to the 0 cm3 mark as previously described. Repeat the titration
as before.
Take the burette and carefully wash it out with about 10 cm3 of the hydrochloric
acid provided. Clamp the burette in the retort stand and place an empty beaker
below it. Using the small filter funnel, fill the burette with hydrochloric acid to just
above the 0 cm3 mark. Remove the filter funnel. Run the acid into the beaker so
that it is on the 0 cm3 mark – your eye should be level with the meniscus of the
liquid when you do this. Also, make sure there are no air bubbles below the tap.
Position the conical flask below the burette as shown in the diagram.
Run the acid slowly into the sodium hydroxide solution in the flask with constant
swirling. Your teacher will show you exactly how to do this.
Take the two beakers and label them as hydrochloric acid and sodium hydroxide
solution. Add about 100 cm3 of the appropriate solution to each.
Ideally the whole procedure should be repeated until the volume of acid added in
each titration agrees to within 0.1 cm3. Only do the experiment up to a maximum
of three times and each student should do at least one titration.
When the acid is added a distinct yellow colour will be seen in the blue solution.
Eventually, the colour in the conical flask will resemble a ‘streamer’ that grows
longer and longer. At this point, increase the rate of swirling and add the acid
drop by drop. When the solution remains green for a few seconds, stop adding
the acid and record the volume of acid added in the results table. The volume of
acid should be read with your eyes level with the meniscus of the liquid.
Take the conical flask and using the bulb pipette add 25 cm3 of the 1 mol/dm3
sodium hydroxide solution. Add about 5 drops of the bromothymol blue indicator
and swirl the flask to mix it in.
USE THE HOT MAP PROVIDED TO REARRANGE THE INSTRUCTIONS ABOVE
IN TO THE CORRECT ORDER.
SOURCE 6
1 Take the two beakers and label them as sulfuric acid and sodium hydroxide
solution. Add about 100 cm3 of the appropriate solution to each.
2 Take the conical flask and using the bulb pipette add 25 cm3 of the 1 mol/dm3
sodium hydroxide solution. Add about 5 drops of the bromothymol blue
indicator and swirl the flask to mix it in.
3 Take the burette and carefully wash it out with about 10 cm3 of the
hydrochloric acid provided. Clamp the burette in the retort stand and place an
empty beaker below it. Using the small filter funnel, fill the burette with sulfuric
acid to just above the 0 cm3 mark. Remove the filter funnel. Run the acid into
the beaker so that it is on the 0 cm3 mark – your eye should be level with the
meniscus of the liquid when you do this. Also, make sure there are no air
bubbles below the tap.
4 Position the conical flask below the burette as shown in the diagram.
5 Run the acid slowly into the sodium hydroxide solution in the flask with
constant swirling. Your teacher will show you exactly how to do this.
6 When the acid is added a distinct yellow colour will be seen in the blue
solution. Eventually, the colour in the conical flask will resemble a ‘streamer’
that grows longer and longer. At this point, increase the rate of swirling and
add the acid drop by drop. When the solution remains green for a few
seconds, stop adding the acid and record the volume of acid added in the
results table. The volume of acid should be read with your eyes level with the
meniscus of the liquid.
7 Wash out the conical flask with water and then pipette another 25 cm3 of the
sodium hydroxide solution into it and add five drops of indicator. Fill up the
burette with acid to the 0 cm3 mark as previously described. Repeat the
titration as before.
8 Ideally the whole procedure should be repeated until the volume of acid added
in each titration agrees to within 0.1 cm3. Only do the experiment up to a
maximum of three times and each student should do at least one titration.