Question 1 Why HCl show acidic behaviour whereas glucose and alcohol do not show acidic behaviour?
Question 2 Why does an aqueous solution of an acid conduct electricity?
Question 3 Why does dry HCl gas not change the colour of the dry litmus paper?
Question 4 Why does distilled water no conduct electricity whereas rain does?
Question 5 Compounds such as alcohol and glucose also contain hydrogen but are not categorised as acids. Why?
Question 6 What are strong acids. Give example?
Question 7 What are weak acids. Give example?
Common in Acids
When acids are dissolved in water,the hydrogen separate out as positively charged hydrogen ion (H +)
The compounds such as glucose and alcohol also contains hydrogen but they do not show acidic character. Because their hydrogen does not separate out as hydrogen ion on dissolving in water.
All hydrogen containing compounds are not acids can be shown by the following experiment:
(1) Take solution of hydrochloric acid, sulphuric acid, glucose and alcohol.
(2) Fix two iron nails on a rubber cork and place the cork in a beaker.
(3) Connect the nails to the terminal of battery through a switch and a bulb.
(4) Pour some dilute hydrochloric solution in the beaker and switch on the current. The bulb starts glowing. This shows that hydrochloric acid solution taken in the beaker conduct electricity.
(5) Pour some dilute sulphuric acid solution in the beaker and switch on the current. The bulb starts glowing. This shows that sulphuric acid solution taken in the beaker conduct electricity.
(6) Pour some glucose solution in the beaker and switch on the current. The bulb does not glow. This shows that glucose solution taken in the beaker does not conduct electricity.
(7) Pour some ethanol solution in the beaker and switch on the current. The bulb does not glow.
This shows that ethanol solution taken in the beaker does not conduct electricity.
Hydrochloric acid and sulphuric acid conduct electricity due to the presence of charged particles whereas glucose and ethanol do not contain ions and hence do not conduct electricity.
Distilled water does not conduct electricity because it does not contain any ionic compounds dissolved in it.
Rain water conduct electricity because it contain dissolved gases which react with water vapours present in atmosphere to form acids(carbonic acid).This acid provide ions to conduct electricity.
In the absence of water, a substance will not form hydrogen ion and hence will not show acidic behaviour.
Dry HCl does not show acidic behaviour but when some water is present, its acidic behaviour can be observed. The colour of the litmus will not change.
An acid which is completely ionised in water and thus produces a large amount of hydrogen ion is called strong acid.
For Example: HCl, H2SO4 , HNO3
An acid which is partially ionised in water and produces a small amount of hydrogen ion is called weak acid.
For Example: Carbonic acid, Acetic acid