5.2: Equilibrium calculations Flashcards
reaction quotient, effect of temperature on equilibrium constant
Reactant quotient
aB + bB ⇄ cC + dD
Q < K
The reaction proceeds in the forward direction, large amount of reactants, therefore products are formed
Q > K
The reaction proceeds in the reverse direction, large amounts of products, therefore reactants are formed
Q = K
Both forward and reverse reactions occur at the same time, reaching equilibrium
MICE (ICE)
Molar ratio, Initial concentration, Change in concentration, Equilibrium concentration
When K is large
Large numerator, large concentration of product, favours reverse reaction
When K is small
Large denominator, large concentration of reactant, favours forward reaction
Effect on K when temperature increases in an exothermic reaction
An increase in temperature will decrease K, equilibrium shifts left to favour reactants, the denominator gets larger and Q gets smaller
Effect on K when temperature increases in an endothermic reaction
An increase in temperature will increase K, equilibrium shifts right to favour products, the denominator gets smaller and Q gets larger
Beer-Lambert law states…
concentration is proportional to light absorption
*original intensity = OI
intensity after absorption = I
Beer-Lambert equations
A = εbc = log(i / i0) = kc
A = absorption
ε = molar absorptivity cm-1 or mol/L
b = length of cell (cm)
c = concentration mol/L
k = constant of proportionality
what does light absorption depend on (3)
(1) the substance itself
(2) concentration of sample (high C means more absorption)
(3) length of cell (longer cell, more absorption)
what is colourimetry
an analytical method for determining the concentration of coloured ions in a sample
5 features of a colourimeter
(1) light source
(2) colour filter
(3) sample cell with solution
(4) detector
(5) recorder/electronic display
function of a light filter in a colourimeter
selects light of an appropriate colour that will be strongly absorbed by the sample
