## Enthalpy of Vaporization of Water

Jeremy Jong 3H
Posts: 16
Joined: Fri Sep 25, 2015 3:00 am

### Enthalpy of Vaporization of Water

On Table 8.3 on pg 284, the textbook mentions two $\Delta H{_{vap}}^{o}$ values for water. One is 40.7 Kj/mol and the other is 44.0 Kj/mol at $25^{^{o}}$C. Im confused what that means. Does that mean that the 40.7 Kj/mol value is at $100^{^{o}}$C? If so then why doesn't $q=C\Delta T$ from $25^{^{o}}$C to $100^{^{o}}$C give me the difference in the $\Delta H{_{vap}}^{o}$ values

Taylor Rafii
Posts: 4
Joined: Tue Nov 17, 2015 3:00 am

### Re: Enthalpy of Vaporization of Water

I believe that the deltaHvap value of 40.7 kJ mol^-1 refers to the standard enthalpy of vaporization of water at its normal boiling point, 100 degrees Celsius. Therefore, the other deltaHvap value of 44.0 kJ mol^-1 refers to the standard enthalpy of vaporization of water at its standard room temperature, 25 degrees Celsius. The room temperature deltaHvap value is higher because it takes that much more energy, about 3.3 kJ mol^-1, to vaporize the water at 25 degrees Celsius.

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