Module 5.1 - Rates, Equilibrium, and pH Flashcards
What is Rate of Reaction?
How fast reactants are converted into products
What does rate depend on?
- Concentrations of reactant
- Rate constant
What is the equation for rate of reaction?
A + B -> C + D
Rate = k[A]^m[B]^n
What does m and n show in the equation
Rate = k[A]^m[B]^n
The order of reaction with respect to that species
Can be either 0, 1, or 2
How do you calculate total reaction order?
m + n
What are the units for rate of reaction?
mol dm-3 s-1
What is the rate constant? (K)
- Relates to the concentrations of the species that affect the rate of a reaction to the overall rate of reaction
- Constant when temperature remains constant.
How do you find K in a reaction?
Rearrange rate equation
k = rate / [A]^m[B]^n
How are zero, first, and second order species shown on concentration-rate graphs?
Zero = Horizontal First = Diagonal upwards Second = curving upwards
What does Zero order mean?
The concentration of the species has no impact on the rate
rate = k
What does First order mean?
The concentration of the species and the rate are directly proportional - double conc. doubles rate
rate = k[A]
What does Second order mean?
- Rate is proportional to the concentration of the species squared
- Doubling conc. will quadruple the rate
- Rate = k[A]²
How are zero, first, and second order species shown on concentration-time graphs?
zero = linear diagonal down first = curved downwards second = curved downwards with a kink in the line
How would you write a rate equation for A, B, and C, A being 1st order, B being 0 order, and C being 2nd order?
Rate = k[A][C]^2
What is half life?
The time taken for the initial concentration of the reactants to decrease by half.
How do you determine half life of a reactant?
From a concentration-time graph, each time the concentration halves.
e.g. if starting conc = 1.8, 1st half life = 0.9, 2nd half life = 0.45, etc.
What are the 2 general ways to investigate rate of reaction at given times
- Measuring change in a reactant mass or concentration over time
- Measuring change in a product mass or concentration over time
How do you obtain a concentration-time graph through titration?
- Remove small samples of a mixture at regular intervals throughout reaction
- Titrate samples to determine concentration of a given reactant or product at that time
What is the Rate determining step?
the slowest step in a reaction, that determines the overall rate
