2. (12 pts.) Choose correct\' or \'incorrect\' on each of the following descript

Question

2. (12 pts.) Choose correct' or 'incorrect' on each of the following descriptions on thermodynamics: (a) (2 pts.) The entropy of a system increases in the course of a spontaneous change (correct/incorrect). (b) (2 pts.) All reversible engines have the same efficiency regardless of their construction (correct/incorrect). (c) (2 pts.) Because entropy is always positive for all substances, the slope of a plot of Gibbs energy against (d) (2 pts.) Because volume is always positive for all substances, Gibbs energy always increases when the pressure (e) (2 pts.) When substance A has a lower molar entropy than substance B, the molar Gibbs energy of substance A is (f) (2 pts.) he reaction A? B at constant temperature and pressure is spontaneous when the molar Gibbs energy or temperature is negative at constant pressure and composition (correct/incorrect) of the system in increased at constant temperature and composition (correct/incorrect) less sensitive to temperature than that of substance B (correct/incorrect) A is higher than that of B (correct/incorrect)

Explanation / Answer

(a) The given statement is CORRECT.

Beacause all spontaneous process are irreversible process and for irreversible process ,the change in entropy of the system is always greater than zero.So the entropy of a system increases in the course of a spontaneous change.

(b)The given statement is INCORRECT.

Because different engines have different material of construction. So the design equipments is different for different engines. And by the carnot theoram, Carnot engines have maximum thermal efficiency than any other engines.

(c)The given statement is CORRECT.

Because, dG=V*dP-S*dT -------------(1)

Where,dG=change in gibbs free energy.

V=volume of the system.

dP=change in pressure of the system.

S=entropy involved in the system.

dT=Change in temperature of the system.

So,for constant pressure ,dP=0.

equation (1) beccomes ,dG=0-S*dT

=> dG/dT = (--S)

As in question it is provided that entropy is positive for all substances so, the slope dG/dT = (--ve).

(d)The given statement is CORRECT.

Because, dG=V*dP-S*dT -------------(1)

For constant temperature, dT=0

V is always positive.

dP= Pfinal - Pinitial.

Pfinal >Pinitial. (Given in quesrtion that pressure is increasing)

so,dP= +ve

so,

equation (1) beccomes ,dG=VdP

=>dG= +VE.

(e)The given statement is INCORRECT.

Because,by vant hoff's rule,when a substance has high molar entropy then it is less sensitive to temperature.

So,in the given question, substance A has a lower molar entropy than substance B then, the molar gibbs energy of substance A is more sensitive to temperature than substance B

(f) The given statement is CORRECT.

Because for spontaneous process change in gibbs free energy (dG) should be less than zero or negative.

dG= Gproduct - Greactant.

dG=GB - GA (FOR REACTION A----->B)

Given,

GB <GA (FOR REACTION A----->B)

therefore, dG= (--ve)

so the process is spontaneous.

#HOPE THIS WILL HELP YOU..

#THANK YOU..!!!

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