posted by Matthew
Calculate the heat (in kJ) required to transform 58.60 g of dinitrogen tetraoxide from a solid at a
temperature of -9.3 °C to a gas at 47 °C. Report your answer to one decimal place. Data:
Molar mass of dinitrogen tetraoxide, N2O4
= 92.011 g/mol
Melting point = -9.3 °C Boiling point = 21°C.
Enthalpy of fusion = 14.65 kJ/mol
Enthalpy of vaporization = 38.12 kJ/mol.
Molar heat capacity of the liquid phase = 142.7 J/mol•K
Molar heat capacity of the gas phase= 77.3 J/mol•K
Here is how you do it.
For temperature changes in the same phase( all solid, all liquid, all gas),
q = mass x specific heat in that phase x (Tfinal-Tinitial).
For changing phases (from solid to liquid of liquid to gas),
q = mass x heat fusion (at melting point)
q = mass x heat vaporization (at boiling point)
Then add each q together to arrive at the total Q from the starting point to the ending point.