Question

Give reaction of manufacture of sulphuric acid by Contact proceses (industrial method).

Answer 1

Dear Student,

Contact process for the synthesis of sulphuric acid involves three steps:

Step -1: burning of sulphur or sulphide ores in air to generate SO_2.

$S+O_2\to S{O}_2$

​Step-2: catalytic oxidation of sulphur dioxide with O₂ to give ​sulphur trioxide( SO₃) in the presence of vanadium pentaoxide V₂O₅

_{$2S{O}_2\left(g\right)+O_2\left(g\right)\underset{2bar,720K}{\overset{V_2{O}_5}{\to }}2S{O}_3\left(g\right)\Delta H=-196.6KJmo{l}^{-1}$}

Step-3: absorption of SO₃ in H₂SO₄ to give oleum (H₂S₂O₇)

$$\begin{gathered} S{O}_3+H_{2}S{O}_4\to H_2{S}_2{O}_7 \\ \left(oleum\right) \end{gathered}$$

Further, H₂SO₄ of desired concentration is obtained by dilution of oleum with water.The H₂SO₄ obtained by this process is 96-98% pure.

Important notes:

1.Step-2 is the key step in the preparation of sulphuric acid.This step is exothermic,reversible and the forward reaction leads to decrease in volume.Therefore, low temparature and high pressure conditions are favourable to obtain maximum yield.​

$V\stackrel{}{=}\frac{RT}{P}$

2.The temperature should not be very low otherwise rate of reaction will become slow.
3.The reaction is proceeded at a pressure of 2 bar and a temperature of 720 K.

Regards