Question

what is contact process? please tell me the reaction

Answer 1

The Contact process::-
The most important process for making sulfuric
acid in industry is the Contact process. We can think of the Contact process as involving three stages.


Absorb Chemistry for GCSE by Lawrie Ryan

The Manufacture of Sulfuric Acid
Introduction

It was once said that a country's wealth could be measured by its production of sulfuric acid (H2SO4). That may no longer be true, but the acid is still used in the manufacture of paints, fertilizers, plastics, fabrics, dyes, detergents, and many other useful products. In this unit you can find out how we make the acid in industry.

The Contact process
The most important process for making sulfuric
acid in industry is the Contact process. We can think of the Contact process as involving three stages. Look at the process shown in Fig.1 below:


Figure 1. The Contact process.
Stage 1

Sulfur is imported from Poland or the USA. We can also obtain sulfur from the impurities in fossil fuels such as coal. In the first stage of the process, sulfur is burned in air to make sulfur dioxide gas:

sulfur + oxygen sulfur dioxide
S(l) + O2(g) SO2(g)

Stage 2

In the next stage, we convert the sulfur dioxide to sulfur trioxide:

sulfur dioxide + oxygen sulfur trioxide
2 SO2(g) + O2(g) 2 SO3(g)

The reaction happens on a
catalyst of vanadium(V) oxide to speed up the reaction. As much sulfur dioxide as possible is changed into sulfur trioxide, and releases of sulfur dioxide are prevented because it is a gas that causes
acid rain.

Stage 3

In the final stage, the sulfur trioxide is converted into sulfuric acid. The sulfur trioxide gas is absorbed into very concentrated sulfuric acid (a 98 per cent solution of H2SO4 in water), producing a thick fuming liquid called oleum. The oleum is mixed carefully with water, and the sulfur trioxide in the oleum reacts with the water as follows:

sulfur trioxide + water sulfuric acid
SO3(g) + H2O(l) H2SO4(l)

You may wonder why the sulfur trioxide is not mixed directly with pure water. The problem is that this is a highly
exothermic reaction, which would produce a fine mist of sulfuric acid that is difficult to condense and could escape to pollute the air.