5.1.1: How fast? Flashcards
Rate of reaction (definition)
the change in concentration of a reactant or product per unit of time.
Rate constant (k)
the number that connects the rate of reaction with the concentrations of the reactants raised to the powers of their orders in the rate equation.
Order with respect to A
the power to which A is raised in the equation; the effect on the rate when the concentration of A is changed.
Overall order
the sum of all the individual orders.
In a first order reaction, rate
is directly proportional to concentration.
In a second order reaction, rate
is directly proportional to concentration²
In a 0 order reaction, rate
is unaffected by concentration.
Initial rate
Rate when t=0
Half life
time taken for the concentration to halve
Trend in half lives for 0 order reaction
Half life decreases with decreasing concentration
Trend in half lives for first order reaction
Length of half life remains constant
Trend in half lives for second order reaction
Length of half life increases with decreasing concentration
Stochiometrics = reaction order only when?
ONLY in the rate determining step
How to determine k (2nd order reaction)
Plot second graph: rate-conc.²
This results in a straight line going through the origin
Gradient of line = k
What is A in the Arrhenius equation?
Pre exponential factor (takes into account frequency of collisions in correct orientation); given value
