5.2 Energetics Flashcards
(12 cards)
what is enthalpy change
the heat energy a reaction releases or absorbs per mole
exothermic
temperature of surroundings increases
energy is given out by reaction
reactants have more energy than products
enthalpy change is negative
endothermic
temperature of surroundings decreases
energy is taken in by reaction
reactants have less energy than products
enthalpy change is positive
sign for enthalpy change
delta H
positive sign
heat energy absorbed
endothermic
negative sign
heat energy released
exothermic
heat energy (Q) equation
Q = m x c x deltaT
heat energy = mass OF WATER x 4.2 x change in temperature
enthalpy change equation
Delta H = -Q/mol
energy per mole = energy change of water/moles
bond energy
Delta H = break - make
cheat for knowing if equation is positive or negative
sign is opposite to temperature change
reasons for inaccuracy with combustion calorimetry
heat loss
incomplete combustion
reasons for inaccuracy with solution calorimetry
heat loss to surroundings
reaction did not finish
water is no longer pure water
