Topic 1 Flashcards
(15 cards)
What are the four factors that can affect the rate of a chemical reaction?
Concentration, temperature, particle size, catalyst
What effect does decreasing the particle size have on the rate of reaction? Be able to explain in terms of collision theory.
Decreasing the particle size increases the rate of reaction. In order for a reaction to take place reactant particles must collide with each other.
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.
Calcium carbonate lumps and hydrochloric acid.
CaCO3(s) + 2HCl(aq) → CaCl2(aq) + H2O(l) + CO2(g)
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?
Increasing temperature increases the kinetic energy of the reactant molecules and therefore more collisions per second occur.
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.
What happens to the rate if the time taken for a reaction decreases?
The rate increases.
What is the relationship between time and rate in a chemical reaction?
Rate is inversely (indirectly) proportional to time taken.
Rate is proportional to 1/time
(r=1/t)
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 the average rate of reaction?
Average rate of reaction = change 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.
e.g. what is the rate if 5g is lost in 10 seconds?
5/10 = 0.5 gs^-1
How can you tell from looking at a graph that the reaction is faster at the beginning?
Explain this in terms of collision theory.
The gradient of the curve/slope is steeper.
There are more reactant particles so more likelihood of successful collisions occurring at start of a reaction.
How would you recognise the point on a graph when the reaction has just finished?
The slope ‘flattens out’/levels off.
Know how to work out the units for rate depending on which factor is being used to follow the reaction.
e.g. What are the units for rate if…
(a) …a change in mass is measured?
(b) …a change in volume is measured?
(a) If mass change then gs-1
(b) If volume volume change then cm3 s-1
Be able to plot graphs of any data given for a chemical reaction.
List the things you need to remember when drawing a scatter/line graph.
Scales
Axes labels
Accurate plotting
Line of best fit
