Question

Which of the following statement is correct for the catalytic conversion of \[S{O_2}\] into \[S{O_3}\] by contact process?
\[2S{O_2}(g) + {O_2}(g) \rightleftharpoons 2S{O_3}(g)\]
(A) It is an exothermic reaction
(B) It is favored at low temperature
(C) It is not favored at low pressure
(D) All are correct.

Answer 1

Hint: In order to find which of the following statement is correct for the catalytic conversion of Sulphur dioxide into Sulphur trioxide by contact process, we must first have an idea about what a contact process is. The contact process is one of the processes for producing sulphuric acid.

Complete step by step answer:
- Let us first understand about Le-Chatelier’s principle. Le-Chatelier’s principle is also referred to as the equilibrium law which is used to predict the effect of changes in a chemical equilibrium system. When the factors like temperature, pressure, concentration, and inert gases are changed, the equilibrium will shift in such a way that these changes get nullified.
- Now let us understand the contact process. The contact process is one of the processes for producing sulphuric acid. in the above reaction, the Sulphur dioxide converted into Sulphur trioxide in presence of oxygen and catalyst Vanadium pentoxide. The conversion reaction is given below.
\[2S{O_2}(g) + {O_2}(g) \rightleftharpoons 2S{O_3}(g)\]
The enthalpy of the above given reaction is \[\Delta H = - 196KJmo{l^{ - 1}}\].
The negative sign shows that the reaction is an exothermic reaction.
- Based on Le-Chatelier’s principle, low temperature will yield more products. But this reaction cannot take place at very low temperatures. It will require temperature at an optimum level of 400-450\[^\circ C\].
- Similarly, based on Le-Chatelier’s principle high pressure can yield more products. However, in this reaction, the pressure should be kept very low around 1-2 atm due to safety and economic concern.
So, the correct answer is “Option A”.

Note: We have to remember that the manufacture of sulphuric acid will involve the following steps.
- First one is the Extraction of Sulphur
- Next is the preparation of sulfur oxide.
- Converting sulfur dioxide to sulfur trioxide.
- Converting sulfur trioxide to sulphuric acid.