5.1.1 Rates of reaction Flashcards
what does the rate equation provide
The relationship between reactant concentrations and the rate
What is the rate equation
rate = k x [A]ª x [B]ᵇ
Describe/ decode each component of the rate equation
rate = k x [A]ª x [B]ᵇ
- k = rate constant
- [A] and [B] = concentration of reactants
- ª + ᵇ = orders of reactions
What is the relationship between rate and any reactant
rate is proportional to the concentration of reactant to th power of its order of reaction.
rate ∝ [A]ª
give 2 ways to measure rate
- rate = quantity reacted or produced/ time
- rate = change in conc./ change in time
what are the units of rate
mols dm⁻³ s⁻¹
define zero (0) order
- means that the concentration of a reactant has no effect on the rate.
rate ∝ [A]⁰
What happens in a zero order reaction
- any number raised to the power of zero is 1
- conc. does not influence rate
define 1st order
means that any change in conc. gives the same change to the rate
use [A] to be 2 or 3
give an example of what happens in 1st order reactions
- If [A] x2 then rate increases by 2¹ = 2
- Or if [A] x3 then rate increases by 3¹ = 3
define 2nd order
means with respect to a reactant when the rate depends on the conc. raised to the power of 2
use [A] to be 2 or 3
give an example of what happens in 2nd order reactions
- If [A] x2 then rate increases to 2² = 4
- Or if [A] x 3 then rate increases to 3² = 6
how is overall order calculated
overall order = sum of orders with respect to each reaction
how is the units of ‘k’ calculated
They can be determined by:
1. rearranging the equation to make k the subject
2. substitute units into the expression for k
3. use orders
4. cancel common units and show final units on a single line.
