Question

1. For each of the following spontaneous processes, identify the signs of the specified thermodynamic quantities by CIRCLING the correct answers. (18 points) a) The reaction 2KCIO, (s)=2KCI (s)+302 (g) which releases 78 kJ of heat AH> OR AH<0 AS>0 OR AS < 0 ASsur > 0 OR AS surt < 0 b) Boiling water AH>0 OR AH< 0 AS> OR AS < 0 AS sur > 0 OR AS.surk < 0 c) When urea is dissolved in water, the beaker feels cool to the touch AH> OR AH< 0 AS >0 OR AS < 0 AS sur >0 OR ASsur < 0

Answer 1

1. Thermodynamic criterion for the spontaneity of a reaction carried out at a constant temperature and pressure. If ΔG<0, the reaction is spontaneous. If ΔG>0, the reaction is non-spontaneous. If ΔG=0, the reaction is at equilibrium.

And, ∆G = ∆H - T∆S

So, ∆H - T∆S < 0

ΔH	ΔS	ΔG
negative	negative	negative at lower temperatures, positive at higher temperatures
positive	negative	always positive

a) For this reaction heat is released thus ∆H<0

And ∆S is ( entropy of products- entropy of reactants) which is positive. Hence, ∆S>0

And ∆Ssurr <0

b) for boiling of water entropy increases and heat is released. Thus, ∆H <0 and ∆S>0

And ∆Ssurr <0

c) when urea is dissolved in water then heat is consumed. Thus ∆H>0

∆S >0

And ∆Ssurr<0