Final answer:
The entropy change when 8 mol HI condenses at atmospheric pressure is approximately 18.67 J/K.
Step-by-step explanation:
To determine the entropy change when 8 mol HI condenses at atmospheric pressure, we need to use the formula:
ΔS = nR ln(Vf/Vi)
where ΔS is the entropy change, n is the number of moles (8 mol in this case), R is the gas constant, and (Vf/Vi) is the ratio of final and initial volumes.
Since HI is condensing, the final volume is smaller than the initial volume, so (Vf/Vi) is less than 1. This means that the natural logarithm term will be negative. Plugging in the values and calculating, we find that the entropy change is approximately 18.67 J/K.