Question

Assess the spontaneity of the following reaction using ΔSsys and ΔSsurr:

3 X2 (g) + R (l) → RX6 (g) ΔHrxn = +60.5 kJ

Is this reaction spontaneous or nonspontaneous at 100 °C? In 1-2 sentences, explain your answer and what your answer means with respect to how this reaction occurs. You must show work on your worksheet for full credit.

Answer 1

$ΔS_{univ}=ΔS_{surr}+ΔS_{sys}\\ ΔS_{univ}=ΔS_{surr}+\frac{q_{sys}}{T}$

$q_{sys} = ∆H = 60.5kJ$

$ΔS_{univ}=ΔS_{surr}+\frac{60.5}{373} =ΔS_{surr} + 162.2J$

The reaction is non-spontaneous because it is endothermic (∆q>0) and it's change in enthalpy js too small to displace the effects of the energy absorbed.