Question

A student prepared \[20\% \] sodium hydroxide solution in a beaker containing water.
The observations noted by him are given below.
l. Sodium hydroxide is in the form of pellets.
II. It dissolves in water readily.
Ill. The beaker appears cold when touched from outside.
IV. The red litmus paper turns blue when dipped into the solution.
The correct observations are:
A )\[I,{\text{ }}II{\text{ & }}III\]
B ) \[II,{\text{ }}III\,\& IV\]
C ) \[III,{\text{ }}IV{\text{ & }}I\]
D) \[I,{\text{ }}II{\text{ }} and {\text{ }}IV\]

Answer 1

Hint: Sodium hydroxide is commonly called caustic caustic soda because of its corrosive action on animal and vegetable tissues. Large quantity of sodium hydroxide is now-a-days prepared by electrolytic processes.

Complete step by step answer:
 Since sodium hydroxide is an ionic compound , it is soluble in water which is a polar solvent. It is a soluble salt. It is seen in the form of pellets. Each pellet is like a small button. It also dissolves in water. It is a basic salt. Hence, it turns red litmus paper to blue colour. It is an exothermic reaction when sodium hydroxide dissolves in water and the solution is corrosive. Hence, the beaker in which sodium hydroxide is dissolved in water, turns hot.
Hence, observations \[l,{\text{ }}II{\text{ }} and {\text{ }}IV\] are correct.
Therefore, option “D” is correct.

Additional Information: \[NaOH\] is
 (a)Deliquescent white crystalline solid
(b)Highly soluble in water, solution (aqueous) is corrosive and soapy to touch
(c)It is sparingly soluble in alcohol.
(d)It is a strong alkaline substance.
(e) As a strong base it reacts with acidic oxides.
(f) Caustic Property : \[NaOH\] breaks down the proteins of skin to a pasty mass. On account of this property, it is called caustic soda.

Note: Sodium hydroxide, also known as lye and caustic soda. Sodium hydroxide is a highly caustic base and alkali that decomposes proteins at ordinary ambient temperatures and may cause severe chemical burns.. As with other alkaline solutions, it feels slippery with skin contact due to the process of saponification that occurs between NaOH and natural skin oils.