Unit 1, Topic 1- Rates of Reaction Flashcards
What are the four factors that can affect the rate of a chemical reaction?
Concentration, temperature, particle size, catalyst
Describe the collision theory.
In order for a reaction to take place reactant particles must collide with each other.
What effect does decreasing the particle size have on the rate of reaction?
Decreasing particle size increases available surface area making it more likely for a successful collision to take place. There are more collisions per second.
Give an example reaction where changing the particle size can affect the rate of reaction.
Changing particle size of marble chips in reactions with acid. Smaller chips faster reaction.
Burning magnesium powder is faster than burning magnesium ribbon.
Describe why increasing the concentration results in an increase in reaction rate.
Increasing concentration increases the number of reactant particles and therefore more collisions per second occur.
How does temperature affect reaction rate?
As temperature increases, the reaction rate increases.
What is a catalyst?
A catalyst is a substance that can be added to a chemical reaction to speed it up/ increase the rate. The catalyst itself is not used up in the process.
Name 4 ways that a chemical reaction could be followed to work out how fast the reaction is proceeding.
Measure volume of gas collected
Measure mass loss
Measure pH change
Measure colour change
What is the formula used to calculate average rate of reaction?
Average rate of reaction=changd in quantity measured/change in time
Know how to calculate the average rate of reaction from either a table of results or from a graph.
Practise
What is the rate of reaction if 5g is lost in 10 seconds?
ror=5/10=0.5gs -1
How can you tell from looking at a graph that the reaction is faster at the beginning?
The gradient of the curve/slope is steeper.
How can you tell from looking at a graph that the reaction is faster at the beginning? (explain this in terms of collision theory.)
There are more reactant particles so more likelihood of successful collisions occurring at the start of a reaction. As the reaction goes on the reactant particles are used up so if the concentration decreases and rate decreases.
How would you recognise the point on a graph when the reaction has just finished?
Where the slope first ‘flattens out’/levels off.
What are the units for rate if
a)a change in mass is measured?
b)a change in volume is measured?
a)gs ^-1
b)cm^3 s^-1
