have learnt that acids give H3O+ or H+ ion in water.
Let us see what happens when a base is dissolved in water.
NaOH (s) –––H²O ––––> Na + (aq) + OH – (aq)
KOH (s) –––H²O––––> K + (aq) + OH – (aq)
Mg (OH) 2(s) –––H²O––––> Mg+ 2 (aq) + 2OH – (aq)
On dissolving bases in water produces hydroxide (OH- )ions. Bases which are soluble in water are called alkalis. All bases donot dissolve in water. Be(OH)2 is slightly soluble in water.
What do you observe when water is mixed with acid or base?
Activity 9
- Take 10 ml water in a test tube.
- Add a few drops of concentrated H2
SO4
to it and swirl the test tube slowly.
- Touch the bottom of the test tube.
• What do you feel?
•
Is it an exothermic or endothermic process?
Carry out the above activity with sodium hydroxide
pellets instead of H2
SO4
and record your observation.
The process of dissolving an acid or a base in water is
an exothermic process. Care must be taken while mixing
concentrated nitric acid or sulphuric acid with water. The
acid must always be added slowly to water with constant
stirring. If water is added to a concentrated acid, the heat
generated may cause the mixture to splash out and cause
burns. The glass container may also break due to excessive
local heating. Look out for the warning sign (shown in