(a) Entropy of vaporization of most liquids at 1 bar is all close to 85 J/K*MOL

Question

(a) Entropy of vaporization of most liquids at 1 bar is all close to 85 J/K*MOL (also called Trouton's rule). Provide a physical explanation for the Trouton's rule. (b) Entropy of vaporization of water liquid however is noticeably higher than other liquids (109 vs. 85.) Provide another physical explanation for the deviation seen for water entropy of vaporization. (c) A student learned in physical chemistry that the second- law thermodynamics dictates that the entropy of the universe always increases in a spontaneous process. Then he observed that when the temperature drops below O C, water automatically freeze. So he concluded that entropy of ice must be greater than that the entropy of water liquid at 0 C. do you agree with his conclusion? Explain your answers.

Explanation / Answer

(a)Trouton's rule states that entropy of vaporization of most liquids is 85-88 JK^-1mol^-1 at the normal boiling point hence this law can be used to make a rough estimate of the heat of vaporization. (b) Water has usually large entropies of vaporization. That is because water is more ordered than most liquids due to extensive hydrogen bonding which orients the molecules and increases the amount of molecular order.As a result, the increase in molecular disorder on converting 1 mole of liquid to vapour is greater for water and thus deltaS(vap) is greater. (c)This is not true because at ) degree celsius (melting point) in case of freezing of liquid to solid at melting point firstly delta S(system) is negative and delta S(surrounding) is positive but both of them have same value Hence deltaS(total) = 0. Hence the process remains at equilibrium

Related Questions

Navigate

• Browse (All)
• Browse #
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.