CH. 2.2 - ENTHALPY Flashcards
What is Enthalpy?
Enthalpy is the amount of energy in a system at a constant temperature
Can absolute enthalpy be measured?
No, which is why we use ΔH = ΔE + PΔV (we use Δ to calculate change in enthalpy)
At a constant pressure, ΔH (enthalpy change) of a system is = to…
the heat flowing into or out of a system:
ΔH = qₚ
What is latent heat?
the energy change associated with physical processes that involve a change of state
What are examples of endothermic state changes?
Melting, boiling, etc.
(solid —> liquid —> gas)
What are examples of exothermic state changes?
Condensation, freezing, etc.
(gas —> liquid —> solid)
If ΔH < 0, is the process EXOthermic or ENDOthermic?
exothermic
if ΔH > 0, is the process EXOthermic or ENDOthermic?
endothermic
What is Calorimetry?
the study of heat flow in physical and chemical processes
TRUE OR FALSE: a calorimeter and its contents will INCREASE in temperature during an EXOthermic process
TRUE
TRUE OR FALSE: a calorimeter and its contents will INCREASE in temperature during an ENDOthermic process
FALSE: the calorimeter and its contents will DECREASE
What is the Standard Enthalpy of Formation?
the enthalpy change that occurs when one mole of a substance is formed from elements in their standard states
ΔH* (element in standard state) = _____
0
What is Hess’s Law?
the enthalpy change for a reaction is the SUM of the enthalpy changes for the individual steps of the reaction
What is Bond Enthalpy (BE)?
the energy required to break one mole of a specific type of bond (double or triple) between 2 atoms
