Chapter 6.2 Enthalpy: Chemical Change at Constant Pressure

Question 1

enthalpy

Answer 1

a thermodynamic variable that relates directly to energy changes at constant pressures

Question 2

pressure - volume work (PV work)

Answer 2

mechanical work done when the volume of the system changes int he presence of an external pressure (P)

Question 3

Quantity of PV work (equation)

Answer 3

w = -PΔV

Question 4

Enthalpy of a system (definition and equation)

Answer 4

the internal energy plus the product of the pressure and volume:
H = E + PV

Question 5

Change in Enthalpy (ΔH) (definition and equation)

Answer 5

change in internal energy plus the product of the pressure (constant), times the change in volume (ΔV):
ΔH = ΔE + PΔV

Question 6

Enthalpy change of a reaction (equation)

Answer 6

ΔH = Hfinal - Hinitial = Hproducts - Hreactants

Question 7

exothermic process

Answer 7

heat as a product
An exothermic process RELEASES heat and results in a decrease in the enthalpy of the system:
Hproducts

Question 8

endothermic process

Answer 8

heat as a reactant
An endothermic process ABSORBS heat and results in an increase in the enthalpy of the system:
Hproducts > Hreactants so ΔH > 0