Thermodynamics Flashcards
When two objects reach thermal equilibrium, that means their _______________ and ______________ are equal.
Temperatures; average kinetic energy
In a calorimeter, energy is transferred between
(2 possibilities)
1) one chemical species and another chemical species (ex. hot iron ball in water)
2) a chemical reaction and an aqueous solution (ex. dissolving ammonium nitrate in water lab)
NO ENERGY IS LOST FROM THE CALORIMETER UNLESS THE QUESTION PROMPTS YOU IN THAT DIRECTION.
Heat capacity (c) can have units including
mass, moles, or neither. Watch your units carefully in thermo!
Exothermic processes
ΔH < 0
Surroundings feel hot
Temperature of surroundings increases
Endothermic process
ΔH > 0
Surroundings feel cold
Temperature of surroundings decreases
ΔH°rxn formula from bond energies
ΔH°rxn = broken – formed
Breaking attractions is always
endothermic.
Forming attractions is always
exothermic.
ΔH°rxn from ΔH°f values requires you multiply the
ΔH°f values by the coefficients in the balanced chemical equation.
ΔH°rxn formula related to energy transferred and moles of rxn
ΔH°rxn = –qsurr/molrxn
If a reaction is exothermic, the bonds in the __________ are stronger/more stable.
Products
ΔH°fus is used during what phase change?
Melting
–ΔH°fus is used during what phase change?
Freezing
ΔH°vap is used during what phase change?
Vaporization
–ΔH°vap is used during what phase change?
Condensation