Question

Aluminium reacts with caustic soda to form:
A. Sodium meta aluminate
B. Aluminum hydroxide
C. Aluminium oxide
D.Sodium Tetra aluminate

Answer 1

Hint: Sodium hydroxide \[NaOH\] is commonly known as caustic soda or soda. It is a white crystalline odorless solid at room temperature. It is highly alkaline in nature and on reaction with metals including Aluminium it releases hydrogen gas and the reaction is highly exothermic.

Complete step by step answer:
We know caustic soda is also known as sodium hydroxide having chemical formula \[NaOH\].
Aluminium is represented as the symbol \[Al\].
So, when Aluminium which is an amphoteric metal reacts with caustic soda it will form sodium aluminate and hydrogen gas is evolved as a result.
The reaction is as follows:
\[\underset{\text{Aluminium}}{\mathop{2Al}}\,+\underset{\text{Caustic soda}}{\mathop{2NaOH}}\,+2{{H}_{2}}O\to 2\underset{\begin{smallmatrix}
 \text{Sodium } \\
 \text{meta }
 \\
 \text{aluminate}
\end{smallmatrix}}{\mathop{NaAl{{O}_{2}}}}\,+\underset{\text{Hydrogen gas}}{\mathop{3{{H}_{2}}\uparrow }}\,\]
This reaction is highly exothermic.

So, the correct answer is Option A.

Additional Information:
Sodium metal aluminate here, Metarefers to least hydrated form because sometimes it exists in the hydrated form in an excess of water containing environment.
Exothermic reactions are the reactions which release energy in the form of heat and light and the reason for this energy released is because the total energy of the products is less than the total energy produced by the reactants.
Uses of sodium aluminate:
It is used to solidify the concrete, mainly when working during frost.
It is also used in water treatment as a supplementary to soften the water and as a coagulant aid to improve flocculation, and for removing dissolved silica and phosphates.
Uses of caustic soda:
It is used in the manufacturing of pulp, petroleum products, soaps, detergents and chemical production.
Other applications include water treatment, food, textiles, metal processing, mining, glass making and others.

Note: Aluminium and \[NaOH\] that is sodium hydroxide cannot be stored in the same containers because they both react heavily with the evolution of heat and form sodium aluminate as a product of reaction. Ortho, Meta, Para, etc., are all variations of something called the condensation degree of the aluminate ions.