Rates of Reaction Flashcards
Rate of reaction definition
How fast reactants turn into products and the amount of reactant used or product formed divided by time
What method is used to measure rate of reaction when a solid or a coloured substance is formed
Disappearing cross method
Which two methods can be used to measure he rate of reaction when a gas is produced
A balance to measure mass loss over a period of time
Gas syringe to measure amount of gas produced over a period of time
When might you draw a line graph rather than a bar chart
The independent variable is continuous
Why is an anomalous result
A result which does not fit the general trend of the other results or is not close to the line of best fit
Four main factors which affect rate of reaction
Temperature
Surface area
Concentration
Presence of a catalyst
How does increasing the concentration of a solution or pressure of gases increase rate of reaction
There are more particles of the reactant per unit volume so there is a higher frequency of successful collisions
How does increasing the surface area increase the rate of reaction
Increasing surface area increases the number of particles exposed to the surface so there is a higher frequency of successful collisions
How does increasing the temperature increase the rate of reaction
Particles have more energy so move faster so there is a higher frequency of collisions
There are also more particles that have the activation energy so more collisions are successful
What is a catalyst
A substance that speeds up the rate of reaction without itself being chemically changed by the end of the reaction so can be reused
How does a catalyst work/ why does adding a catalyst increase rate of reaction
Provides an alternative pathway for the reaction that has a lower activation energy
More particles will have the activation energy therefore a higher frequency of successful collisions
What is collision theory
In order for a reaction to occur the reactant particles must collide with each other with the activation energy
How is the average rate of reaction calculated
= volume of gas produced/ time
Two causes of anomalous results when using a gas strange to measure rate of reaction
Gas loss at the start of the experiment as the bung was not put on fast enough
Gas loss due to leaky apparatus
Difficulty in reading the gas syringe when it is moving too fast
What is the shape of the typical graph that shows the rate of reaction over time
Steep at the start as there is a fast reaction
Shallower gradient in the middle as the reaction is slowing down
Horizontal when the reaction has stopped
