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Equilibrium constant expression for aA + bB ↔ cC + dD
- K = K1/K-1 = [C]c[D]d/[A]a[B]b
- Product favored: K has large value
- Reactant favoried: K has a small value
- Note - Pure solids and liquids aren't included in equilibrium constant expression
Effect on equilibrium constant if equation is reversed? A coefficient is added? You add equations together?
- Reversed: Kbackward = 1/Kforward
- Coefficent: Knew = Knoriginal
- Addition: Knew = K1 x K2
Relationship between Kp and Kc
- KP = Kc x (RT)Δn
- Δn = moles gas products - moles gas reactants
- note - Kp always given in atm
- same as equilibirum constant, but at ANY concentration.
- Can be compared with equilibrium constant to determine how reactants/products will change
- Q>K - [reactants] increase and [products] decrease
- Q<K - [reactants] decrease and [products] increase
- Q=K - [reactants] and [products] do not change
- If rxn has only reactants Q = 0, only products Q = ∞
Explain the simplification step and method of approximations
- Simplification: assume x is very small and eliminate x from equation (+x, -x). Solve equation. If x is less than 5% of the largest initial concentration then the answer is correct.
- Method of approximations: if x is not smaller than 5% of the largest initial concentration then input the number you got into the equation. If the new answer is not less than 5% of the largest initial concentration then input the number you just got into the equation, repeat until less than 5%!
Effect of adding/removing reactants, gas volume changes, and temperature shifts
- Adding a reactant / removing a product: rxn ---->
- Adding a product / removing a reactant: rxn <-----
- When volume is reduced equilibrium favors side w/ fewer moles (gases)
- When volume is increase equilibrium favors side w/ more moles (gases)
- Temperature: determine exothermic/endothermic. Write heat into the equation (exo - heat as product, endo - heat as reactant). Consider temperature change as a change to heat within the equation. EXAMPLE - endothermic heat increases forces equilibrium ---->