standard enthalpy and entropy questions

[seunglim87]

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so i found this question online, but i dont know how to slove this. i feel like they didnt give me enough information to solve it, but if any of you know how to solve this, please help

(*is the standard sign)
For water, delta H*vap = 40.67kJ/mol, What is delta S*vap for water?
a. 109 kJ/K mol
b. -109 kJ/K mol
c. 109 J/K mol
d. 406.7 J/K mol


The answer was C.

i understand that delta S is usually in J/k mol sign, but how would you derive that number?

 

[qkchen]

so i found this question online, but i dont know how to slove this. i feel like they didnt give me enough information to solve it, but if any of you know how to solve this, please help

(*is the standard sign)
For water, delta H*vap = 40.67kJ/mol, What is delta S*vap for water?
a. 109 kJ/K mol
b. -109 kJ/K mol
c. 109 J/K mol
d. 406.7 J/K mol


The answer was C.

i understand that delta S is usually in J/k mol sign, but how would you derive that number?

use (deltaG) = (deltaH) - T(deltaS) and realize that vaporization is an equilibrium process, so (deltaG) = 0. also, at vaporization, temperature is 100C (or 373K). now, you can set (deltaH) = T(deltaS) and solve for (deltaS).