Equilibrium (AS/A level) Flashcards
four charactertistics of equilibrium
dynamic
forward = backward reaction at same rate
concentration of r/p remain constant
closed system
what is la chateliar’s principle
If one or more factors that affect an equilibrium is changed, the position of equilibrium shifts in the direction that reduces the change
decreasing concentration of reactants causes
equilibrium to move left
whichever side you take stuff off, equilibrium shifts to the side to restore ok
ok
increasing pressure causes
equilibrium moves to less molecules side
how does temperature affect equilibrium
depending on exo/endo
both forward/backward rate increases
which factor is Kc dependant
temperature
how does catalyst affect equilibrium
no effect
no effect on delta H
remember to practice mole ratios
ok
what is homogeneous equilibrium
everything present in the same phase
what is heterogeneous equilibrium
things present in more than one phase
definition of an acid
proton donor
definition of a base
proton acceptor
what are conjugate pairs
HCl (acid) = cl- (conjugate base)
differ by one proton
definition of ionic product of water
[H+][OH-]mol2dm-6 (Kw)
1 x 10^-14
definition of pH
-log[H+]
how to find pH of strong acids
[H+] = concentration of acid
how to find pH of strong bases
using Kw
[OH-] = concentration of base
how to find pH of weak acids
Ka = [H+]^2/[HA}
what does high value of Ka mean
equilibrium toward right = stronger acid
pKa formula
-log[Ka] (less positive = more acidic)
definition of indicator
Acid-base indicator is a dye/mixture that changes colour over a specific pH range. The weak acid and conjugate base has different colours. Hln ⇌ H+ + ln-
what does pKa show
transition of colour
where is equivalence point
midpoint of fall
strong acid + strong base
equivalence point + pH range
7
10.5 - 3.5
strong acid + weak base
equivalence point + pH range
5
7.5 - 3.5
weak acid + strong base
equivalence point + pH range
9
11 - 7.5
how to find Ka of buffer solution
[H+][A-]/[HA]
definition of buffer solution
a solution that resists in pH changes when small amounts of H+ or OH- are added;
uses of buffer solution
electroplating
dyes
how to find equations in buffer solution
acid partially dissociates so conjugate base is not enough - salt is needed
A (acid) ⇌ B + C
D (salt) → E + F (conjugate base)
look at examples of buffer solutions now
ok
how to find pH of buffer solution
pKa + log [A-]/[HA]
definition of solubility product
product of concentrations of each ion in a saturated solution of a sparingly soluble salt at 298K raised to the power of their relative concentrations
definition of saturated solution
solution in contact with its undissolved solid
smaller Ksp means
less soluble
what is Ksp dependant
temperature
definition of common ion effect
the reduction in the solubility of a dissolved salt achieved by adding a solution of a compound which has an ion in common with the dissolved salt, often resulting in precipitation.
definition of partition coefficient
equilibrium constant that relates the concentration of solute partitioned between two immiscible solvents at a particular temperature.
how to find Kpc
[organic solvent]/[in water]
