unit 3 revison Flashcards
what is hess’ law?
the enthalpy change of a reaction is the same no matter what route is taken
what is enthalpy change of formation?
the enthalpy change when one mole of substance is formed under standard conditions
what is enthalpy change of combustion?
the enthalpy change when one mole of substance is completely burnt in oxygen under standard conditions
what are bond enthalpies?
enthalpy change required to break a covalent bond with all species in the gaseous state
what is enthalpy change?
a measure of heat energy given out or taken in when a chemical or phyiscal change occurs at constant pressure
what is the enthalpgy change of formation of elements in their natural states?
0
what is activation energy?
the energy required for a reaction to occur
what is a catalyst?
a substance that lowers the activation energy of a reaction without being physically or chemically altered by the reaction
name 5 factors that increase the rate of a reaction
- pressure in a gas
- concentration of a solution
- tempertature
- pressence of a catalyst
- surface area of a solid
why do most collisions not result in a succesful reaction?
as the particles either don’t have enough energy or they have the wrong orientation
name three things the maxwell-boltzman distribution tells us about the distribution of energy amongst particles
- no particles have 0 energy
- a few have very high energy
- average energy is not the same as the most probable energy
in what kind of system can equilibrium occur in?
a closed system
what is le chatelier’s principle?
if a system at equilibrium is disturbed, the equilibrium moves in the other direction to reduce the disturbance
name 3 conditions of equilibrium
- it is a dynamic process
- it can only be reached in a closed system
- it can be approached from either direction
do catalysts affect dynamic equilibrium?
they do not affect equilibrium they only allow equilibrium to be reached a lot faster
