Chapter 18 Rates of Reactions Flashcards
(15 cards)
what does every reaction have?
a reaction rate
what are reaction rates measured by?
observing the changes in the quantities of reactants or products over time
formula for reaction rate with quantity:
rate = quantity reacted or produced / time
formula for rate of reaction with concentration:
rate = change in concentration/ change in time
what is the units for rate of reaction?
any convenient unit e.g minutes, seconds
- if in seconds units for rate is mol dm-3 / s
shorthand for concentration of A:
[A] (mol dm-3)
what is rate of reaction proportional to?
concentration of a particular reactant raised to a power n (order of reaction for that reactant)
rate = [A]^n
common orders:
- zero order (0)
- first order (1)
second order (2)
what is zero order?
when the conc of a reactant has no effect on the rate
what happens in a first order of a reactant?
- if the conc of A is doubled, the reaction rate increases by a factor of 2^1 =2
- if the conc of A is tripled, the reaction rate increases by a factor of 3^1 =3
what happens in a. second order reaction?
- if the conc of A is doubled, the rate of reaction increases by a factor of 2^2=4
- if the conc of A is tripled, the reaction rate increases by a factor of 3^2 =9
what relationship does the rate equation give?
the mathematical relationship between the concs of the reactants and the rate
formula for reaction rate with 2 reactants:
rate = k [A]^m [B]^n
A = conc of A
B = conc of B
m = order of reaction with respect to A
n = order of reaction with respect to B
k = constant
what does the overall order of a reaction give?
the overall effect of the concs of all reactants on the rate of reaction
formula for overall order:
overall order = sum of order with respect to each reactant
overall order = m + n
