Determining the Hardness of a Water Sample(Complete) Flashcards
What indicator is used in this titration?
Determining the hardness of a water sample
Eriochrome Black.
How is hardness measured?
As ppm, CaCO3.
What is the colour change experienced in this titration?
Wine red to blue.
What is added in a small amount and why?
Buffer solution.
To keep the pH> 10 so the indicator will work properly.
Describe the procedure of the titration.
To the sample of water in the conical flask add:
Buffer
Indicator- goes wine red.
ETDA
The end point is when the solution goes blue.
Do one rough and 2 accurate titres.
What does EDTA stand for?
Ethylene Diamine Tetra Acetic Acid.
What does unboiled water contain?
Permanent and temporary hardness.
What does boiled water contain?
Permanent hardness only.
Suggest a way to determine if the water supply has temporary hardness.
Boil and the scale will indicate temporary hardness.
Identify. compound of calcium that is one of the main causes of permanent hardness.
Calcium sulfate.
Calcium chloride.
What buffer is used in this titration?
pH 10
What would happen if the wrong buffer was used for this titration?
Poor end point.
EDTA complexing with other ions.
State and explain whether the water having passed through a deioniser is suitable for use as deionised water in the laboratory or is the deioniser needs to be changed or regenerated.
The water is unsuitable because hardness remains.
The deioniser needs to be replaced because hardness remains
