Page 1 of 1
Posted: Tue Jan 29, 2019 3:00 pm
What does it mean by enthalpy is a state function ?
Posted: Tue Jan 29, 2019 3:06 pm
A state function means that we only care what happens at the beginning and at the end and it isn't dependent on the path taken. So, enthalpy is a state function because we can add and subtract heat to get the change in enthalpy.
Posted: Tue Jan 29, 2019 3:08 pm
Hi! Enthalpy being a state function essentially means that the value of enthalpy does not depend on the path taken to obtain that state. In other words, it can be added and subtracted. An example of a state function, like enthalpy, is temperature. When finding the change in temperature, you look at the initial temperature and the final temperature, not the temperature changes throughout the reaction. This is the same for enthalpy.
Posted: Tue Jan 29, 2019 3:09 pm
State function is a property that depends only on the current state of the system and is independent of how that state was prepared.
In other words, it doesn't matter how much or how many times the enthalpy value changed. All that matters is the net result (the sea level example that Dr. Lavelle gave during lecture). Compare that to heat, which is not a state function because it matters how the energy was transferred (raising temperature by supplying it as heat vs. stirring it and using kinetic energy to raise temperature).
Posted: Tue Jan 29, 2019 3:50 pm
If you're a more visual person picture the image Lavelle presented in class of a mountain. There was a blue line and a red line, both lines started and ended in the same place. However, the path each line took was different! But because enthalpy is a state property that path doesn't matter because both lines started and ended in the same place.