Chemistry - How Fast? Flashcards
What is rate of reaction?
How quickly a reactant substance reacts together with another substance to form products during a chemical reaction.
What are the different units for measuring rates of reaction and why?
Because
rate of reaction = Quantity of reaction used / time taken or quantity of reaction formed / time taken
This quantity can either be mass or volume. For a reaction that took seconds the units would be:
g/s or cm^3/s
What are some factors that can affect a chemical reaction?
Concentration
Temperature
Catalyst
Pressure
Surface Area
How does temperature, concentration/pressure, surface area and catalyst affect the rate of reaction? Explain using collision theory.
Chemical reactions can only happen if reactant particles collide with enough energy. The more frequently particles collide, and the greater the proportion of collisions with enough energy, the greater the rate of reaction.
Increasing the temperature, concentration/pressure, surface area and use a catalyst speeds up the reaction by increasing the number of succesful collisions.
How does temperature affect the rate of reaction?
As the temperature increases the rate of reaction also increases.
How does changing the temperature of a reactant alter the rate of reaction? Use collision theory to explain.
If the temperature is increased, the reactant particles have more kinetic energy so they therefore move quicker. This means the particles will collide more often with more energy so there will be more successful collisions so the rate of reaction will increase.
Use the graphs to calculate the rate of reaction at specific times in a chemical reaction.
On GoodNotes
How do you increase the surface area of a solid?
Break the solid into smaller pieces or by grinding it into a powder.
How does changing the surface area affect the rate of reaction?
If you increase the surface area the rate of reaction also increases.
How does changing the surface area of a reactant alter the rate of reaction? Use collision theory to explain.
Increasing the surface area means there are more particles exposed to the other reactant. This means that the frequency of collisions will increase meaning there is more chance of successful collisions so the rate of reaction increases.
How do you work out the surface area to volume ratio? Do the examples.
Divide the surface area by the volume. Examples on GoodNotes.
How does changing the concentration of a reactant or the pressure of a gaseous reactant affect the rate of reaction?
If you increase the concentration/pressure of a reactant the rate of reaction increases.
How does changing the pressure/concentration of a reactant alter the rate of reaction? Use collision theory to explain.
If the concentration of a reactant is increased or the pressure of a reacting gas is increased there becomes more particles per unit volume. It then becomes more crowded and therefore there is a greater chance of the particles colliding so there is more chance of a successful collision. This means that the rate of reaction is increased.
What is activation energy?
The minimum amount of energy reactants need to react.
What is a catalyst?
A substance that can increase the rate of reaction without being used up itself.
It provides an alternative reaction pathway with a lower activation energy.
Decreasing the activation energy means that more particles will have sufficient energy to overcome the energy barrier so the rate of reaction increases.
