consider the equilibrium between liquid water and gaseous water: H_2O(l) reversi

Question

consider the equilibrium between liquid water and gaseous water: H_2O(l) reversiblearrow H_2O(g) Predict the signs of Delta H degree and Delta S degree for the evaporation of water and then determine whether the process of evaporation is entropically or enthalpically driven. Enthalpically because it is exothermic and moves toward less disorder Enthalpically because it is exothermic and moves toward more disorder. Entropically because it is endothermic and moves toward less disorder. Entropically because it is endothermic and moves toward more disorder. The vapor pressure of a liquid is defined to be the pressure of a gas that is in thermodynamic equilibrium with its liquid phase in a closed container at a fixed temperature. What is the vapor pressure for liquid water at 75 degree C? 0.062 atm 0.41 atm 2.45 atm 15.8 am

Explanation / Answer

Q25

dH ad dS for evaporation...

dH --> must be positive, since it is endothermic, meaning it requires energy

dS --> must be positive, since more chaos is created, vapor is highe rin entropy

then

choose D

Q26

find Vapor pressure of liquid at 75°C

assume:

ln(P2/P1) = H/R/(1/T1 -1/T2)

Hvap = -286 - -242 = -44 kJ/mol = -44000

ln(P2/1) = 44000/8.314*(1/(100+273) - 1/(75+273))

solve for P2

P2 = exp(-1.0192) = 0.3608 atm, nearest answer is B

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