4.2 Enthalpy Flashcards
what does the amount of heat given out/taken in by a reaction vary with?
conditions
- temperature
- pressure
- concentration of solutions
etc…
define enthalpy change
The energy change of a reaction per mole at constant pressure
What are the standard conditions for an enthalpy change to be
measured under?
temp = 298 K
pressure = 100 kPa
what happens to the products in exothermic reactions? (temp)
end up with less heat
= lost into their surroundings
= ΔH is -ve
what happens to the products in endothermic reactions? (temp)
end up with more heat
= taken in from surrounding
= ΔH is +ve
what are enthalpy/energy level diagrams for?
represent enthalpy changes
in enthalpy/energy level diagrams, what needs to is shown?
relative enthalpy levels of reactants and products
what is the y-axis and x-axis of enthalpy/energy level diagrams?
x-axis = extent of the reaction (time)
y-axis = enthalpy
