Question

In the contact process, SO2 is passed twice through the catalytic converted. Why?

(a) To produce less while converting to SO3

(b) Since the energy and power consumed is less

(c) To increase the yield

(d) To avoid choking hazards

This question was posed to me during an internship interview.

I need to ask this question from P-Block Elements topic in section P-Block Elements of Chemistry – Class 12

Answer 1

The correct answer is (c) To increase the yield

To elaborate: Sulfur dioxide is passed twice to increase the yield and conversion to form more sulfur trioxide. In the first pass, only 63-65% of sulfur dioxide is converted to sulfur trioxide. When passed for the second time, the conversion increases to 80% hence increasing the yield of sulfur trioxide. This can be repeated to achieve a maximum 99% conversion.