Question

Indicate whether you would expect the entropy of the system to increase or
decrease.
(i) 2SO2 (g)+O2 (g)
2SO3(g)​

Answer 1

A decrease in the number of moles on the product side means lower entropy. An increase in the number of moles on the product side means higher entropy. If the reaction involves multiple phases, the production of a gas typically increases the entropy much more than any increase in moles of a liquid or solid.