Flashcards in Module 5 Deck (43):
How do you calculate rate and what are the units?
Change in concentration / change in time
Mol dm-3 s-1
When is a reaction of zero order?
When the concentration of the reactant has no effect on the rate
When is a reaction first order?
When the rate depends on its concentration raised to the power of one
If concentration is tripled the rate is tripled
When is a reaction second order?
When the rate depends on its concentration raised to the power of two
If the concentration is tripled the rate increases by a factor of 9
What is the rate equation?
Rate = k [A]^order [B]^order
How do you calculate the overall order of reactants?
Sum of orders with respect to each reactant
What is the shape of a zero order graph?
Straight line with negative gradient
The gradient is equal to the rate constant, k
What is the graph of a first order reactant?
A downward curve with a decreasing gradient over time
The concentration of the reactant to halve is constant (half-life)
What is the shape of a graph with second order?
A downward curve, steeper at the start but tails of slower than a first order curve
What is the gradient of a concentration time graph?
What is the rate determining step?
The slowest step in the sequence
What happens to the Boltzmann distribution when temperature is increased?
It shifts to the right, increasing the proportion of particles that exceed the activation energy
What is the Arrhenius equation?
k = A e^(-Ea/RT)
A = pre-exponential factor(frequency factor)
Ea = activation energy
R = gas constant
T = temperature in kelvin
What is the gradient of a ln k - 1/T graph?
What is the y intercept of a ln k - 1/T graph?
What is Kc?
Kc = [concentration of products]^number of moles / [concentration of reactants]^number of moles
What is a homogeneous equilibrium?
Contains an equilibrium species that all have the same state or phase
What is a heterogeneous equilibrium?
Contains equilibrium species that have different states or phases
What is the mole fraction?
Of A = moles of A / total moles in a gas mixture
What is the partial pressure of A?
Mole fraction of A x total pressure
What is Kp?
The equilibrium constant
Kp = partial pressure of products^number of moles / partial pressure of reactants^number of moles
What are the units for partial pressure?
Pa or kPa or atm
What happens to the position of equilibrium when the concentration of a species is increased?
Shifts in the direction that reduces the concentration
What happens to the position of equilibrium when the pressure is increased?
Shifts towards the side with fewer gaseous molecules
What happens to the position of equilibrium when the temperature is increased?
Shifts in the endothermic direction
What is the only factor which affects K?
What happens to the equilibrium constant, K, when temperature increases in an exothermic reaction?
What is a brønsted lowry acid?
A proton donor
What is a Brønsted-Lowry base?
A proton acceptor
What is a conjugate acid-base pair?
Contains two species that can be interconverted by transfer of a proton
What is a mono basic acid?
One hydrogen ion can be replaced per molecule in an acid-base reaction
Acid + metal =
Salt + hydrogen
Acid + carbonate =
Salt + water + carbon dioxide
Acid + base =
Salt + water
Acid + alkali =
Salt + water
What is the pH of an acid?
What is the pH of an alkali?
What will pH be if [H+] is low?
A high value
What is the relationship between pH and [H+]?
pH = -log[H+]
What is the relationship between [H+] and [HA] for a strong acid?
[H+] = [HA]
For what type of acid does [H+] = [HA]?
A strong acid
How do you calculate pKa?
pKa = -logKa