M5 Equilibrium Reactions Flashcards
Le Chatelier’s Principle
states that changes in the temperature, pressure, volume or concentration of a system will result in predictable and opposing changes in the system in order to achieve a new equilibrium state.
Enthalpy
H = U + PV, U is the sum of the internal energy of a system, P is pressure, V is volume.
Types of Systems
Open - energy and matter can be exchanged between system and surroundings. Closed - only energy can be exchanged between system and surroundings. Isolated - no energy or matter can be exchanged.
Gibbs Free Energy
G = H - TS If G < 0, spontaneous. If G > 0, non-spontaneous. If G = 0, equilibrium.
Dynamic Equilibrium
The forward and reverse reactions occur at the same rate at the time of equilibrium. The concentrations of reactants and products at equilibrium are constant. Equilibrium requires a closed system. There is no change in macroscopic properties at equilibrium.
Physical Equilibrium
changes of state. Rate of evaporation = rate of condensation.
Static Equilibrium
when rates of forward and reverse reactions are 0.
Collision Theory
For a reaction to occur, the particles must collide with sufficient energy to break the bonds and have the appropriate orientation to allow new bonds to form.
Gas Laws
Boyle’s V = k / p at fixed n and T, P1V1 = P2V2. Charle’s V = kT at fixed n and P. Avogadro’s V = kn at fixed P and T. Ideal gas law PV = nRT.
Reaction Quotient
At equilibrium Q = Keq, if Q>Keq then reverse reaction is favoured to reach equilibrium (forward reaction was favoured), if Q
Homogeneous/heterogeneous systems
Homogeneous System: All reactants and products are in the same phase.
Heterogeneous: different phases are present.
The Extent of Reaction
If Keq = 1 then reactants = products. If Keq >1, forward reaction is favoured. If Keq <1, reverse reaction is favoured.
Solubility SNAAP Rule
All compounds containing the following are soluble: Sodium, Nitrate, Ammonium, Acetate (aka ethanoate), Potassium.
Solubility Product
Ionic product = Q. If Q = Ksp then at equilibrium (saturated). If Q > Ksp then supersaturated, more solid forms to establish equilibrium. If Q < Ksp then unsaturated, if solid is present some dissolves to establish equilibrium.
Solubility depends on
strength of ionic bonding (spatial arrangement of lattice, size and charge of ions), strength of ion-dipole attraction (size and charge of ions, geometry/shape of molecule).
