F4 Chem essay

This is a 2010 CE chem essay, and i have the following model answers.

Firstly, the pH of the acids are measured by the formula -log [H+(aq)] and the following will show the factors affecting the pH.

The strength of ionization. (1) For example, the pH of strong acid such as hydrochloric acid has a lower pH than ethanoic acid of same concetration and volume.(1)

The basicity of the acids.(1) For example, same concentration and volume of dilute sulphuric acid has a lower pH than dilute hydrochloric acid as the basicity of sulphuric acid molecules are two, which means there are two H+ ionized.(1)

The concentration of the acids(1). For example, 10M of hydrochloric acid has a lower pH than a 1M hydrochloric acid of same volume.(1)

Chemical knowledge = 6 marks .(Got all here, 1 represents 1 mark)
Effective commmunication= 3 marks

Total 9 Marks.

上面果位可以話係0分~

2010-08-31 00:52:57 補充：
上面果位係.
Discuss the factors exhibiting acidic properties.

Acid can show their typical characterists and chemical reactions only if water
is present.The crystals of citric acid have no effect on dry PH paper or blue
litmus paper.
If water is added to dissolve the crystals of citric acids, the PH paper and blue
litmus paper turns red.Thecrystals of citric acid have no effect on magnesium.If water is added to dissolve the crystals of citric acid, magnesium reacts with the aqueous solution of citric acid to evolve colourless gas bubbles.The crystals of
citric acid can dissolve in water,some molecules of citric acid ionizes to form
hydrogen ions and citrate ions.
Effective communication:
The ability to present idea in a precise manner.The ability to present ideas in a
systematicmanner.The ability to present answer in paraph form and full
sentences.