Question

Which one the following is an example of homogenous catalysis?
A.Manufacture of sulphuric acid by the Contact process
B.Manufacture of ammonia by Haber’s process
C.Hydrolysis of sucrose in the presence of dilute sulphuric acid
D.Hydrogenation oil.

Answer 1

Hint: Catalysis is the phenomenon of increasing the rate of a chemical reaction by adding a catalyst. It is of two types:
Homogeneous catalysis: is a type of catalysis in which reactants and the catalyst used are in the same phase, commonly either in a liquid state or the gaseous state.
Heterogeneous catalysis: in this the reactants and the catalyst are in different phases.

Complete step by step answer:
Manufacture of sulphuric acid by Contact process:
During a contact process of manufacturing of sulphuric acid in very high concentrations vanadium pentoxide (solid) is used as a catalyst. The reactions involved during it is:
${\text{2S}}{{\text{O}}_{\text{2}}}{\text{(g) + }}{{\text{O}}_{\text{2}}}{\text{(g)}}\xrightarrow[{{\text{400 - 45}}{{\text{0}}^{\text{0}}}{\text{C,1 - 2atm}}}]{{{\text{V}}{{\text{O}}_5}({\text{s}})}}{\text{S}}{{\text{O}}_{\text{3}}}{\text{(g)}}$
${\text{S}}{{\text{O}}_{\text{3}}}{\text{(g) + }}{{\text{H}}_{\text{2}}}{\text{S}}{{\text{O}}_{\text{4}}} \to {{\text{H}}_{\text{2}}}{{\text{S}}_{\text{2}}}{{\text{O}}_{\text{7}}}$
${{\text{H}}_{\text{2}}}{{\text{S}}_{\text{2}}}{{\text{O}}_{\text{7}}}{\text{(l) + }}{{\text{H}}_{\text{2}}}{\text{O(l)}} \to {\text{2}}{{\text{H}}_{\text{2}}}{\text{S}}{{\text{O}}_{\text{4}}}{\text{(l)}}$
Here the reactants are in gaseous phase while catalyst is in solid state, i.e. reactants and catalyst are in different phases. And hence it is an example of heterogeneous catalysis
Manufacture of Ammonia by Haber’s Process:
Haber’s Process is also known as Haber-Bosch process and it is an artificial nitrogen fixation process. It’s main industrial process for the production of ammonia. It is an exothermic process.
\[{{\text{N}}_{\text{2}}}{\text{(g) + 3}}{{\text{H}}_{\text{2}}}{\text{(g)}}\xrightarrow[{{\text{400 - 45}}{{\text{0}}^{\text{0}}}{\text{C,150 - 200atm}}}]{{{\text{Fe(catalyst),Mo(promotor)}}}}{\text{2N}}{{\text{H}}_{\text{3}}}{\text{(g)}}\]
As you can see, this process reactants (in gaseous state) and catalyst (in solid state) are in different phases; it is an example of heterogeneous catalysis.
Hydrolysis of sucrose in presence of dilute sulphuric acid:
Sucrose is a disaccharide carbohydrate. Hydrolysis of sucrose yield equimolar solution of glucose and fructose:
${{\text{C}}_{{\text{12}}}}{{\text{H}}_{{\text{22}}}}{{\text{O}}_{{\text{11}}}}{\text{(l) + }}{{\text{H}}_{\text{2}}}{\text{O(l)}}\xrightarrow{{{{\text{H}}_{\text{2}}}{\text{S}}{{\text{O}}_{\text{4}}}{\text{(aq)}}}}{{\text{C}}_{\text{6}}}{{\text{H}}_{{\text{12}}}}{{\text{O}}_{\text{6}}}{\text{(l) + }}{{\text{C}}_{\text{6}}}{{\text{H}}_{{\text{12}}}}{{\text{O}}_{\text{6}}}(l)$
As you can see in the above reaction both the reactants and the catalyst are in same phase (liquid), thus it is an example of homogenous catalysis
Hydrogenation of Oil:
Hydrogenation of oil is the process of addition of Hydrogen across a double or triple bond in an oil molecule which is usually highly unsaturated. The process is carried out in the presence of a catalyst, mostly nickel:
${\text{C = C(l) + }}{{\text{H}}_{\text{2}}}{\text{(g)}}\xrightarrow{{{\text{Ni(s)}}}}{\text{CH - CH}}$
Since the reactants and the catalyst are in different states it is an example of heterogeneous catalysis.
And thus we can conclude that the correct answer is C.

Note:Please note some of the important points when it comes to catalyst:
Catalyst is a substance which increases the rate of a reaction by decreasing the activation energy of that reaction.
Catalyst is fully recovered at the end of the reaction or in other words it is not consumed in the chemical process.
A catalyst increases the rate of both forward as well as backward reaction to the same extent which means it helps to attain equilibrium at a faster rate.
If a reaction is thermodynamically not feasible a catalyst cannot make that reaction feasible.