5.1.1 - How Fast Flashcards
What is the reaction rate?
The change in the amount of reactants or products per unit time.
What does the order of reaction tell you?
How the reactant’s concentration affects the rate.
If the order is 0 what will happen to the rate if the concentration of the reactant is doubled?
Rate stays the same.
If the order is 1 what will happen to the rate if the concentration of the reactant is doubled?
Rate also doubles.
If the order is 2 what will happen to the rate if the concentration of the reactant is doubled?
The rate quadruples.
Rate =
k[A]^m [B]^n
What is k, and what does it mean if it is bigger?
k is the rate constant and the bigger it is, the faster the reaction.
What are m and n in the rate equation?
The orders of reaction with respect to reactant A and reactant B.
On a concentration-time graph what does 0 order look like?
Straight line downwards (negative gradient) \
On a concentration-time graph what does 1st order look like?
Curve downwards like a curly l.
What is the half life of a reaction?
The time it takes for half of the reactants to be used up.
What can you use the half life to calculate?
The order of the reactant, and the rate constant k.
What happens to the half life in for 0 order?
The half life decreases.
What happens to the half life for 1st order?
Same length.
What happens to half life in a second order reaction?
Increases.
What is the equation for calculating k using the half life? (Only 1st order)
k = In2 / half life
What is the rate concentration graph for 0 order?
Straight horizontal line.
What is the rate concentration graph for 1st order?
Straight line through origin, directly proportional.
What is the rate concentration graph for 2nd order?
Curve upwards.
What 4 ways can you measure the rate of reaction?
- measure the volume of gas evolved.
- measure the loss in mass of a gas evolved.
- use colorimetry to measure the colour change of a reaction.
- measure the pH change of a reaction.
What is the rate determining step?
The slowest step in a reaction.
How do you know what reactants are in the rds?
They are in the rate equation.
How many moles of each reactant is in the rate equation?
You look at the order and that tells you how many moles of each of the reactant.
What are intermediates?
Not shown in the overall equation as they are created and used up.
What must occur to particles in order for a reaction to take place?
They must collide with energy equal to or above the activation energy and they must collide with the right orientation.
What happens to the rate constant when the temperature increases?
It also increases.
In the Arrhenius equation what is activation energy measured in?
J mol-1
In the Arrhenius equation what is temperature measured in and how do you calculate this?
Kelvin (+273)
When you log the Arrhenius equation what graph do you plot? What is the gradient and what is the y intercept?
ln against 1/T. -Ea/R. InA
