Enthalpy; From Brightspace Flashcards
What is the general definition of enthalpy?
Enthalpy is defined as the internal energy plus the product of pressure and volume: H = E + PV.
What symbol is used to denote enthalpy?
H
Is enthalpy a state function?
Yes, enthalpy is a state function.
What is the formula for pressure-volume work?
w = - P∆V
What does P represent in the equation for pressure-volume work?
Pressure
What does ∆V represent in the equation for pressure-volume work?
The change in volume of the system: ∆V = V final - V initial.
What is the sign convention for work done by the system during gas expansion?
Negative value of w indicates work done by the system.
What happens to ∆V when a gas expands?
∆V is positive.
What happens to ∆V when a gas is compressed?
∆V is negative.
What is the relationship for the change in enthalpy at constant pressure?
∆H = ∆E + P∆V
What does ∆H equal at constant pressure?
The heat gained or lost at constant pressure: ∆H = qP.
What does the subscript P on q indicate?
The process occurs at constant pressure.
How does the change in enthalpy relate to internal energy?
∆H equals the change in internal energy plus the product of constant pressure and the change in volume.
Under what conditions is enthalpy more useful than internal energy?
When many physical and chemical changes occur at constant pressure.
What is the relationship between ∆H and qP?
∆H depends only on the initial and final states of the system.
True or False: q is a state function.
False
Fill in the blank: Enthalpy is a function that describes many processes occurring under _______.
constant pressure
What is the significance of the negative sign in the equation w = - P∆V?
It conforms to the sign convention for work.
What is the key limitation in the relationship between ∆H and qP?
Only P–V work is involved and the pressure is constant.
