3rd March '09

1) Common Apparatus used in lab:

- deionised/distilled water
- white tile
- beaker
- pipette filler
- retort stand
- funnel
- pipettes
- conical flask
- burette
- dropper
- glass rod
- volumetric flask
- weighing bottle
- electronic analytical balance

2) To prepare standard solutions:

eg Using a fixed mass of solid sample
-requires weighing

OR

Using a fixed volume of liquid sample
- requires use of pipette

2) Choosing an appropriate weighing vessel.

a) Ensure the weighing pan is clean.
Use a brush to remove solid particles or a paper towel to wipe off liquids.
b) Tare the balance.
c) Centre the vessel on the balance.
d) Add the required mass of substance into the vessel.
e) Record the mass after the reading has stabilized.
f) Before leaving, ensure the balance pan is clean from spills.
g) Transfer sample to a container, and re-weigh the vessel.
h) Mass of sample transferred is the difference in of the two readings.
i) Recording readings to appropriate number of decimal places.

Tips & Precautions


Use a draft shield for accurate mass readings.
Use a clean and dry weighing vessel.
Use a weighing bottle for weighing hygroscopic substances.
Allow a hot sample to cool before weighing.
When weighing volatile substances, ensure you seal the vessel before taking the final mass reading.
Ensure the substance weighed is dry.

3) Choosing an indicator

a) BROMOTHYMOL BLUE; strong acid-strong base
b) PHENOLPHTHALEIN; weak acid-strong base
c) METHYL ORANGE; strong acid-weak base

4) When reading the liquid level...

Eye should be at level of meniscus, not above or below.
Reading from an angle results in parallax error.