Acidic Environment 1-

Question 1

what are acids

Answer 1

substances capable of providing hydrogen ions (H+) for chemical reactions. (proton donors). free H ions are available only in soluions where the minute proton is stabilised by association with a solvent molecule. In aq solutions it exists as the hydronium ion.
H+ + H2O –> H3O+
Examples: hydrochloric (HCl), Sulfuric (H2SOO4) and nitric acid (HNO3)

Question 2

what are bases

Answer 2

Substances that can react with acids to form salts or as substances that give rise o hydroxide ions (OH-) in solution. (proton acceptor).Alkalis are a group of ions containing the OH- ion.
E.g. Sodium Hydroxide (NaOH), ammonium hydroxide (NH4OH) and calcium hydroxide Ca(OH)2.

Question 3

what is a neutral substance

Answer 3

do not produce an imbalance in the H+ and OH- ion concentrations in solution.
E.g. CO and NO

Question 4

What are indicators

Answer 4

chemicals which change colour according to the acidity of the solution they are in.

Question 5

natural indicator preparation

Answer 5

1. grind HYDRANGEA LEAVES in a mortar and pestle with a little water and ethanol. ( coloured compound is found inside plant cells. this will break down the cell walls and release the dye)
2. Place solution in a beaker and heat (do not boil) with 150ml water.
3. Decant the coloured solution.
   In acid, –> blue colour
   in base –> pink colour

Question 6

bromothymol blue

Answer 6

yellow –> blue (6 - 7.6)

Question 7

methyl orange

Answer 7

red–> yellow (3.1 - 4.4)

Question 8

litmus

Answer 8

red –> blue (5 - 8)

Question 9

phenolphthalein

Answer 9

colourless –> pink (8.3 - 10)

Question 10

Universal indicator

Answer 10

mixture of several indicators (phenolphthalein, btb, methyl red and thymol blue).
Red- acidic
green - neutral
violet- basic

Question 11

Everyday uses of indicators

Answer 11

• testing water in aquariums
• testing water in swimming pools
• testing soil pH

Question 12

Why is it important for commercial indicators to be stable over a long period of time.

Answer 12

indicators are used when necessary and bought well in advance. If they didn’t last very long between manufacture and use there would be a problem of immediacy or changing to an indicator that did store well. You would need to make them fresh each time you needed them which would be inconvenient and flowers may not be in season.