Environmental Chemistry - Water Flashcards
What is hard water?
2
Hard water is water that will not easily form a lather with soap
Hardness in water is caused by Ca(^2+) or Mg(^2+) ions dissolved in the water
What is temporary hardness?
2
Hardness that can be removed by boiling the water
Caused by calcium hydrogencarbonate Ca(HCO3)2
What is permanent hardness?
2
Hardness which cannot be removed by boiling the water
Caused by calcium sulfate CaSO4
What is total hardness of water?
Calcium hardness + magnesium hardness
What is a complexometric titration?
2
A titration involving the formation of a complex between metal ions and a reagent such as edta.
In this type of titration the end point is marked by a sharp decrease in the concentration of free metal ions
What is a buffer solution?
2
A buffer solution is a solution that resists change in pH
I.e. it keeps the pH constant
What is flocculation?
The coming together (coagulating) of small suspended particles in water
What is a flocculating agent?
A chemical added to water to coagulate suspended particles and this help sedimentation to take place
What is biochemical oxygen demand (B.O.D)?
5
The amount of dissolved oxygen
Consumer by biological (biochemical) action
When a sample of water is kept at 20 degrees
In the dark
For five days
What is eutrophication?
The enrichment of water with nutrients, leading to excessive growth of algae and other plants
What is primary treatment of sewage?
A mechanical process in which large solids are removed by screening and some suspended solids are removed by settlement (sedimentation)
What is secondary treatment of sewage?
2
A biological oxidation process in which the levels of suspended and dissolved organic materials are reduced
I.e. the sewage is decomposed by means of bacteria which use the nutrients from the sewage together with oxygen from the air to break down the sewage
What is tertiary treatment of sewage?
A process involving the removal of phosphorus compounds by precipitation and the removal of nitrogen compounds by biological and ion-exchange methods
What is the principle of colorimetry?
The amount of absorbance of light by a coloured solution is proportional to the concentration of the solution
