Question

Does the following reaction show an increase or decrease in entropy? KCLO3(s) ---> 2KCL(s) + 3O2(g)

Answer 1

The entropy change is positive.

Entropy is associated with the degree of disorder, or number of degrees of freedom. In the reaction `2KClO_3(s) --> 2KCl(s) + 3O_2(g)` we see that 2 moles of a solid forms 2 moles of a solid and 3 moles of gas.

In general, any reaction in which there are more moles of gaseous products than moles of gaseous reactants there will be an increase in entropy because the gas molecules have more degrees of freedom - they can move around randomly throughout the reaction volume whereas the solids can only vibrate in their crystal lattices.