Question

Which gas is produced when silicon reacts with caustic soda solution?
A)${{\text{O}}_2}$
B)${\text{C}}{{\text{l}}_2}$
C)${{\text{N}}_2}$
D) ${{\text{H}}_2}$

Answer 1

Hint: The formula of caustic soda solution is ${\text{NaOH}}$.When silicon reacts with it, sodium ortho-silicate is formed and hydrogen gas is produced.

Step-by-Step Explanation: When silicon reacts with caustic soda solution which is also called sodium hydroxide, the following reaction happens-
$ \Rightarrow {\text{Si + 4NaOH}} \to {\text{N}}{{\text{a}}_4}{\text{Si}}{{\text{O}}_4}{\text{ + 2}}{{\text{H}}_2}$
This is a displacement reaction in which hydrogen is replaced with silicon to form sodium silicate and hydrogen is liberated. Silicon reacts with sodium hydroxide which is strongly alkaline in nature and forms sodium ortho-silicate. Hydrogen gas is liberated in the process.

Hence, the correct answer is ‘D’.

Additional Information- The complex formed in the above reaction sodium ortho-silicate. It is the salt of unstable orthosilic acid $({{\text{H}}_4}{\text{Si}}{{\text{O}}_4})$.It is a white powder which is used as an additive to reduce tension in water flooding of oil fields so that oil can be extracted easily from the surface of earth.

Note: Caustic soda is a white solid compound which is strongly alkaline in nature. It is used as a cleansing agent and in manufacturing of washing soda. It forms sodium ortho-silicate on reaction with silicon which is a white powder and used as anti corrosion treatment on iron and steel surfaces as it stabilizes the ferrate ions.