CGIER 33 - Chemical equilibria and psychological consequences Flashcards
describe chemical equilibrium
When the rates of the forward and reverse reactions are equal and the concentrations of the reactants and products no longer change with time
what does the equilibrium constant expression relate ro
Relates the concentration of reactants and products at equilibrium in terms of a quantity called the equilibrium constant, K
what is the equilibrium constant k
Is the ratio of equilibrium concentrations raised to powers equal to the stoichiometric coefficients
3 values of constant k
has a constant value regardless of the initial concentration of reactants and products
depends on the particular reaction and the temperature
is unit-less
Kc denotes
Kc denotes that the equilibrium concentrations of the reacting species are in moles/L or molarity (M)
Kp denotes
Kp tell us that the equilibrium concentrations of the reacting species are expressed in terms of pressure
why is solids of reactant omitted in constant k calculation in reactions involving solids and liquids
The concentration of a solid is fixed by its density and does not change, so it can be omitted from the equilibrium constant expression.
why can liquid be omitted in calculation in reactions with solid and pure liquid
The concentration of a liquid is very high and does not change, so it can be omitted from the equilibrium constant expression.
Kfwd
1/Krev
if K»1
Reaction is product-favored The equilibrium concentrations of the products are greater than the concentrations of reactants.m
if K is <1
Reaction is reactant-favored The equilibrium concentrations of the reactants are greater than the concentrations of products.
2 types of problems in solving equilibrium
- using equilibrium conc. of reactants and products to determine the value of K
- Using initial conc. of reactants and products and the value of K to determine the equilibrium concentrations of reactants and products
how would one use equilibrium conc. of reactants and products to find K
k = [products] coefficient^/ [reactants]coefficient
equilibrium concentration of reactants and products are provided
if volume of vessel is measured divide equilibrium concentration of products and reactants by volume in LITRES
how would one determine equilibrium concentration of reactants and products using initial conc. of reactants and products
Table ICE
Initial
Change (x if coefficient is greater than 1 multiply x by that coefficient.)
Equilibrium - sum of initial and change
if the volume of the vessel is known divide initial conc and equilibrium conc by that value
using algebra use equilibrium table and conc at equilibrium to solve for x
determine the value of K
2NO(g) + O2(g) -> 2NO2(g)
Initial Pressures: PNO = PO2 = 1.00 atm
Final Pressure: PO2 = 0.506 atm
Using ICE table O Initial: 1.00 Change: -x Equilibrium: 0.506 1.00 - x = 0.506 x = 1 - 0.506 x = 0.494 using find equilibrium for 2NO and 2NO2 Equilibrium for 2NO =0.012 Equilibrium for 2NO2 = 0.988 k (0.988)2^/ (0.012)2^(0.506)
