Thermochemistry Flashcards
Define enthalpy
Addition or subtraction of energy in a system
- potential energy change
- enthalpy change makes phases change for reaction that involves breaking inter and intramolecular bonds
Endothermic
- Positive value
- Absorb heat or energy
- Reactants are lower than products (in graph)
- Written as reactants
Exothermic
- Negative value
- Releases energy or heat
- Reactants higher than products (in graph)
- Written as products
Amount of energy transferred depends on:
- mass of substance
- temp change
- specific heat cap.
Define Calorimetry
Lab technique that measures energy changes that is associated w/ phase changes or chemical changes
What is the Potential Energy for Elements
Ep= 0
What is more stable, negative molar enthalpy or positive molar enthalpy, why?
negative enthalpy bcs a molecule is stable with more attractive forces. attractive forces lower the potential energy.
What H2O is used for open environments?
H2O gas (vapour)
What H2O is used in a bomb calorimeter?
H2O liquid
Breaking bonds ____ energy
need energy
Forming bonds _____ energy
release energy
For a collision to proceed, you need:
- Correct orientation
- sufficient collision energy (activation energy) which depends on the kinetic energy of reactants
Activation Energy and low Ea vs High Ea
- Minimum collision energy needed for a reaction
- Low Ea= reactions is faster
- High Ea= reactions slower
Activated Complex
- Unstable
- has partial bonds
- within reactions
- highest energy
Catalysts
- Increases rxns
- Not consumed in rxns
- Make Ea smaller = faster
- regenerated at end of reaction
- long acting
where is Ea in graph
reactant to peak
where is H in graph
reactants to products
