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)
Le Chatelier’s Principle
If an external stress is applied to a system at
equilibrium, the system adjusts in such a way that the stress is partially offset
as it tries to re-establish equilibrium
examples of stress that can be applied to systems at equilibrium
Change in concentration ofreactants or products
Change in pressure or volume of a gaseous system
Change in temperature
Catalyst
if there is an increase in reactant the equilibrium will shift to …
products
if there is a decrease in reactant the equilibrium will shift to
reactants
if there is an increase in products equilibrium will shift to
reactants
if there is a decrease in products the equilibrium will shift to
products
in an exothermic reaction if temperature increase the equilibrium shifts to
reactants
in an exothermic reaction if the temperature decreases the equilibrium shifts to
products
in an endothermic reaction if there is an increase in temperature the equilibrium shifts to
products
in an endothermic reaction if there is a decrease in temperature equilibrium shifts to
reactant
what happens when you hyperventilate
Hyperventilate,rapid shallow breathing.
Too much CO2 is exhaled.
Equilibrium shifts to left - makes more CO2
Altitude sickness
pressure of oxygen at sea level = 0.2 atm
pressure of O2 at high altitudes = 0.14atm
In lungs; Hb + 4O2 = Hb(O2)4
Equilibrium shifts to left - hypoxia - low levels of O2 in tissue
if there is an increase in pressure/decrease in volume equilibrium will shift
to side with fewer moles of gas
in haber process what conditions must be kept to maximise production of NH3
increased pressure
decreased temperature
