Question

A metal X reacts with aqueous NaOH solution to form Y and a highly inflammable gas. Solution Y is heated and carbon dioxide is poured through it Z precipitates out and sodium carbonate is formed. Z on heating gives \[A{{l}_{2}}{{O}_{3}}\]. Identify X, Y and Z.
(a) \[Al-X,NaAl{{O}_{2}}-Y,Al{{(OH)}_{3}}-Z\]
(b) \[A{{l}_{2}}{{O}_{3}}-X,NaAl{{O}_{2}}-Y,A{{l}_{2}}C{{O}_{3}}-Z\]
(c) \[A{{l}_{2}}{{O}_{3}}-X,{{[N{{a}_{2}}Al{{O}_{2}}]}^{+}}O{{H}^{-}}-Y,Al{{(OH)}_{3}}-Z\]
(d) \[Al-X,Al{{(OH)}_{3}}-Y,A{{l}_{2}}{{O}_{3}}-Z\]

Answer 1

Hint:The reaction is based on the Hall Heroult process. In this process smelting of aluminium occurs. This means aluminium is oxidised to aluminium oxide and heating at high temperature is involved.

Complete step by step answer:
Let us consider X as Aluminium metal as in the end we get \[A{{l}_{2}}{{O}_{3}}\].
When X reacts with aqueous NaOH, it forms Y and inflammable gas. Reaction will be as follows,
\[2Al+2NaOH+2{{H}_{2}}O\to \underset{Y}{\mathop{2NaAl{{O}_{2}}}}\,+3{{H}_{2}}O\]
Here Y is \[NaAl{{O}_{2}}\] and highly inflammable gas is water vapour.
Next Y then heated with carbon dioxide we get Z.
\[\underset{{}}{\mathop{2NaAl{{O}_{2}}}}\,+3{{H}_{2}}O+C{{O}_{2}}\xrightarrow{323-333K}\underset{Z}{\mathop{Al{{(OH)}_{3}}}}\,\downarrow +N{{a}_{2}}C{{O}_{3}}\]
Here Z is aluminium hydroxide precipitated and sodium hydroxide is formed.
Z on heating with \[A{{l}_{2}}{{O}_{3}}\],we get
\[2\underset{Z}{\mathop{Al{{(OH)}_{3}}}}\,\xrightarrow{{{1200}^{o}}C}A{{l}_{2}}{{O}_{3}}+3{{H}_{2}}O\]
Thus, the correct answer to the question is option (a)\[Al-X,NaAl{{O}_{2}}-Y,Al{{(OH)}_{3}}-Z\]

Additional Information:
-Aluminium can undergo many reactions. But usually it is less reactive. It oxides and hydroxides are amphoteric, that is, it can behave as a base as well as an acid. Aluminium is synthesised in its pure form by a process called the Hall Heroult process. It is an industrialised process. It is also an electrolytic process. When the metal as such is exposed to air, it forms a thin white coating of aluminium oxide. Due to this, it is resistant to corrosion to an extent. Aluminium is post transition metal. Aluminium reacts explosively with pure liquid oxygen. Various organic acids can be stored in aluminium containers.

Note: Aluminium is more reactive with carbon and has high oxygen affinity, so it cannot be reduced at high temperatures that is by burning. So, the electrolysis process is used.