Required Practical: Analysis & Purification of Water Samples Flashcards
All 6 cards in this deck
In the required practical on water samples, what three things are carried out on the samples?
Measuring the pH, finding the mass of dissolved solids, and purifying the water by distillation.
What is used to measure the pH of a water sample in the required practical?
Universal indicator (paper or solution) compared with a colour chart, or a pH meter/probe.
What are the steps to find the mass of dissolved solids in a water sample?
e.g. a sample of pond water- Weigh the empty evaporating basin
- Add a measured volume of the pond water and evaporate to dryness
- Reweigh the basin; the increase in mass is the mass of dissolved solids
What are the steps to purify a water sample by distillation in the lab?
e.g. a salty sea water sample- Heat the sample so the water boils and evaporates, leaving the dissolved solids behind
- Pass the vapour through a condenser, where it cools and condenses
- Collect the distillate — pure water
True or false? A sample of water that leaves no solid residue when evaporated to dryness contains no dissolved solids.
True. Dissolved solids would be left behind as a residue when the water evaporates.
Why must you never taste water samples in the required practical?
They may contain harmful microbes or dissolved chemicals.