Question

Zeolites are microporous catalysts. The general formula of a zeolite may be given as-
[A] $\begin{align}
  & {{M}_{\frac{x}{n}}}[{{(Al{{O}_{2}})}_{x}}{{(Si{{O}_{2}})}_{y}}].m{{H}_{2}}O \\
 & \\
\end{align}$
[B]$M[{{(Al{{O}_{2}})}_{x}}].m{{H}_{2}}O$
[C]${{M}_{x}}[{{(Al{{O}_{2}})}_{x}}{{(Si{{O}_{2}})}_{y}}].m{{H}_{2}}O$
[D]${{M}_{x}}[{{(Si{{O}_{2}})}_{y}}].m{{H}_{2}}O$

Answer 1

Hint: Zeolites serve a catalytic purpose. Zeolites have different compositions, hence they have various formulas. Generally they are alumina-silicate but there are other classes of zeolites too.
  Complete step by step solution: Zeolite, a crystalline, aluminosilicate mineral, is a common shape selective catalyst and adsorbent. Zeolite is extremely porous and is resistant to factors like high temperature and pressure.
As we know, catalysis is a process of increasing the rate (speed) of the reaction by using substance (catalyst) which does not change the reaction chemically neither get involved in the reaction.

-The catalytic reaction that depends upon the structure of the pores of the catalyst and the size of the molecules of the reactant and the product is known as shape-selective catalysis.
-Zeolite is used as a shape selective catalyst due to its uniform shape and size of the micropores. In a catalytic reaction, where zeolite is used, the molecules of the reactant are diffused in the pores of the mineral I.e. The molecule is trapped inside it and is later adsorbed in the active sites of the chemical reaction.

ZSM-5 which is a nanometer sized shape selective zeolite catalyst, is used as a highly effective isomerisation, polymerisation and a dehydration catalyst. It is used to convert methanol directly into gasoline (synthetic) along with a mixture of aromatic and aliphatic hydrocarbons on dehydrating.

Generally, zeolites are hydrated, bound to a metal with a positive charge of n+ and contain $Al{{O}_{2}}andSi{{O}_{2}}$thus, have the general formula$\begin{align}
  & {{M}_{\frac{x}{n}}}[{{(Al{{O}_{2}})}_{x}}{{(Si{{O}_{2}})}_{y}}].m{{H}_{2}}O \\
 & \\
\end{align}$
Therefore, the correct answer is option [A] $\begin{align}
  & {{M}_{\frac{x}{n}}}[{{(Al{{O}_{2}})}_{x}}{{(Si{{O}_{2}})}_{y}}].m{{H}_{2}}O \\
 & \\
\end{align}$

Additional Information : The zeolites used in industries are generally synthetic because naturally, zeolites are bound to metals or other minerals. There are various zeolite catalysts which are used in the petrochemical industry and drug, fragrance industry.

Note: It is important to note here that zeolites are aluminosilicate i.e. they will have both aluminium and silicate molecules. Therefore, the option with either silicon or aluminium parts is incorrect. It is also important to remember that the metal is a cation with a positive charge equal to ‘n’.