a) The negative sign has to do with the fact that the energy for the evaporation has to come from the water itself. This means that the energy needed to evaporate has to be "given" by the water in the form of heat, which is why it has a negative sign. (The negative sign is actually missing from the third term of the equation, where it should also be, we will see why):
b) To calculate this, we will use the expression given in item a), adding the missing negative sign and the number of moles multiplying the heat of vaporization:
Using the fact that the number of moles is the quotient between the evaporated mass and the molar mass of water (18 g/mol) and assuming that the evaporated water doesn't "give" energy in the form of heat, we have:
We can therefore rearrange and calculate the final temperature of the remaining 99 grams of water:
con 6.13. Assume that the AvapH of an evaporating liquid comes from the liquid itself, which...
mic or endothermic 612. Ctus is expected. Use equations 6.4 to explain why. 3 ex6ther- farmers sometimes spray water on the fruit trees Citrus farmers frost is when a frost is e that the AvapH of an evaporating liquid comes 6.13. Assume that t the liquid itself, which then changes temperature ac- cording to equation AvapH-q mcAT lal Explain the presence of the negative sign in this equation. (b) If 1.00 g of H2O evaporates at 25.0°C in an adiabatic...
Calculate the enthalpy change, Delta H process in which 32.5 g water is converted from liquid at 18.9 C to vapor 25.0 degrees C. For water Delta H vap =44.0 kJ/mol at 25.0 °C and Cs=4.18 J/(g*^ C) for H2O (l)
Chapter 5 and Chapter 10 Problem solving (please practice the following questions and make sure that you understand the principles behind: you can find Ar from textbook or website I. A 145 g sample of copper metal at 100.0°C is placed into 250.0 g of water at 25.0°C in a calorimeter. When the system reaches thermal equilibrium, the temperature of the water in the calorimeter is 28.8°C. Assume the calorimeter is perfectly insulated. What is the specific heat capacity of...