The entropy change for cooling 1.6g of an organic compound (mol. w. 32, molar heat capacity at constant pressure = 59 J/K mol) from 1000 K to to 800 K is:

We know  ΔS=ΔHT   (1)ΔT=1000-800=200KΔH for cooling the organic compound =nCpΔT=1.632 mol×59JK-mol-×200 K=590 JΔH=-590J because cooling is an exothermic process T = 800 K substituting the values in (1) we get : ΔS=-590 J800 K=-0.7375JK-1