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In an exothermic reaction as temperature increases
the reverse reaction is favoured.
In an exothermic reaction as temperature decreases
the forward reaction is favoured.
In an endothermic reaction as temperature increases
the forward reaction is favoured.
In an endothermic reaction as temperature decreases
the reverse reaction is favoured.
The equivalence point
is where the titrant is neutralized.
The half equivalence point is
half the volume of something added.
diprotic
donates two electrons. if two equivalence points an acid is diprotic and undergoes two dissociations.
examples of diprotic acids
H2SO4, H2CO3
what is exchanged in a closed system
energy
what is exchanged in an open system
matter and energy
define reversible reaction
products can react together to be converted back to reactants
define irreversible reaction
products cannot react together to be converted back to reactants
dynamic equilibrium
when the rate of the forward and reverse reactions are equal.
can equilibrium be achieved in open systems
no
are the extents the same for each reaction
no
What does the extent of the reaction indicate?
how much product is formed at equilibrium.
Le Chatelier’s principle
if a system is in equilibrium and is subjected to change, the system will shift to partially oppose the change
how can the effect on equilibrium be explain
collision theory and reaction rates
adding more reactant
shifts to the right
more product
shifts to the left
decrease in pressure
shifts in the direction of the most particles
adding an inert gas
no change
adding water
shifts in the direction of the most particles
increasing the temperature for exothermic reactions
shift to the left
increasing the temperature for endothermic reactions
shifts to the right
adding a catalyst
on change
if the reaction quotient is at equilibrium it is equal to
the equilibrium constant
what does the value of Kc do
provides a measure of the extent of reaction and the relative concentrations of reactants and products at equilibrium
If Kc is between 10^-4 and 10^4
indicates significant reaction occurs
If Kc is greater than 10^4
indicates almost complete reaction occurs
If Kc is less than 10^-4
indicates negligible reaction occurs
When Kc is reversed
inverse of original Kc
When co-efficients are doubled, Kc…
squared
As the temperature increases, the value of Kc
increases for endothermic reactions and decreases for exothermic reactions
What does the Bronsted-Lowry model describe
acid-base properties in terms of proton transfer
When a proton is donated
the substance is an acid
when a proton is received
the substance is a base
how can hydrogen be represented
as H+ or H3O+
amphiprotic substances
act as either acids or bases
polyprotic acid
can donate more than one proton to a base
Dissociation of diprotic acid
the extent decreases as the dissociations go.
The stronger an acid…
the weaker its conjugate base
the stronger the base
the weaker its conjugate acid
when water self ionises it forms
H2O + H2O — H3O + OH
Kw constant
1 × 10^-14
Kw equation
Kw = [OH] [H3O]
formula for pH
pH = -log'[H3O]
pH of neutral solution
7
pH of acidic solution
less than 7
pH of basic solution
greater than 7
What happens to moles and concentration during dilution
moles of acid or base does not change, concentration decreases
formula for two concentrations and two volumes
c1V1 = c2V2
what happens to pH when an acidic solution is diluted
it increases
define buffer solutions
resist change in pH when a small amount of acid or base is added to them
define Ka
the acidity constant, measure of the strength of an acid Ka = [H][A]/[HA]
define Kb
dissociation constant, measure of the strength of a base Kb = [BH][OH]/[B]
when does an indicator change colour
when equal to the value of pKa
define pH range of an indicator
related to dissociation constant fo the acid-base indicator dissociation reaction.
