Energetics (Physical) Flashcards
calorimetry
the process of measuring the amount of energy absorbed or released during a chemical reaction
endothermic reaction
an endothermic reaction is one that takes in energy from the surroundings so the temperature of the surroundings decreases. in an endothermic reaction, the energy needed to break existing bonds is greater than the energy released from forming new bonds
enthalpy change (𝚫H)
the heat energy change measured under conditions of constant pressure
exothermic reaction
an exothermic reaction is one that transfers energy to the surroundings so the temperature of the surroundings increases. in an exothermic reaction, the energy released from forming new bonds is greater than the energy needed to break existing bonds
Hess’s law
the enthalpy change of a reaction is independent of the route taken
mean bond enthalpy
the enthalpy change when one mole of a specified covalent bond is broken averaged out across the range of compounds
molar enthalpy change
the enthalpy change per mole of a substance
standard conditions
100 kPa and a stated temperature (generally 298K)
standard enthalpy of combustion (𝚫Hcθ)
the enthalpy change when one mole of a substance is burned in excess oxygen under standard conditions
standard enthalpy of formation (𝚫Hfθ)
the enthalpy change when one mole of a substance in its standard state under standard conditions is formed from its elements under standard conditions.
