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Control and Coordination
A student Prepared 20% sodium hydroxide solution in a beaker to study saponification reaction. Some observations related to this are given below :
(I) Sodium hydroxide solution turns red litmus blue
(II) Sodium hydroxide readily dissolves in water
(III) The beaker containing solution appears cold when touched from outside
(IV) The blue litmus paper turns red when dipped into the solution
The correct observations are :
I, II and IV
I, II and III
Only III and IV
Only I and II
D.
Only I and II
The correct option is D.
Sodium hydroxide being a base dissolves in water to form an alkaline solution which turns red litmus blue. A large amount of heat is dissipated, when sodium hydroxide is dissolved in water because the process is exothermic in nature. So, when touched from outside the beaker containing sodium hydroxide solution should be hot.
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Take 5 ml hydrochloric acid in a boiling tube or a conical flask. Add a few pieces of zinc granules to it.
(a) What do you observe on the surface of zinc granules?
(b) Name the gas evolved.
(c) What happens when the above gas is passed through soap solution?
(d) What happens when a burning candle is brought near the gas filled tube?
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