C18 - RATES OF REACTION Flashcards
Give two ways rate of reaction can be measured
- how quickly the reactant is used up
- how quickly the product is formed
Name 5 factors which can affect the rate of reaction (speed up reaction)
1) temperature
2) concentration
3) pressure of reacting gases
4) surface area
5) use of catalysts
What is collision theory?
chemical reactions can only occur if reactant particles collide with enough energy
How do you calculate the rate of reaction?
amount of reactant used/ amount of product formed divided by time taken
What happens to the concentration of reactant during a reaction?
reactant concentration decreases
What happens to the concentration of product during a reaction?
product concentration increases
When is the concentration of a reactant the greatest during a reaction?
at the start
At what speed do reactions start?
reactions start very quickly
What does more frequent collisions result in?
Faster reaction
What must happen for a reaction to occur?
reacting molecules must collide with enough energy
How does increased surface area affect the rate of reaction?
Increased surface area creates more surfaces for the reactant particles to collide off of
How does increased pressure of reacting gases increase rate of reaction?
Increased pressure gives the reactant particles less space, meaning there will be more frequent collisions
How does increased temperature increase the rate of reaction?
Increased temperature makes the reactant particles move faster, resulting in more frequent collisions as the particles are moving more
How does increased concentration of particles increase the rate of reaction?
Increased concentration means there are more particles, resulting in less space and more particles colliding off each other
What are catalysts?
substances that speed up a reaction without being changed or used up in a reaction
What do catalysts provide?
an alternative pathway with a lower activation energy
What do catalysts do and how do they speed up a reaction?
catalysts lower the activation energy of the reaction which allows for more frequent successful collisions to occur, resulting in a quicker reaction
How are catalysts helpful with energy reduction?
catalysts enable the reaction to take place at a lower temperature, which reduces the costs of energy needed
What are enzymes?
important proteins which act as ‘biological catalysts’ and help speed up reactions (lowers the activation energy)
How does a lower activation energy increase rate of reaction?
lower activation energy means more reactant particles have the amount of energy needed to react, resulting in more frequent collisions and a quicker rate of reaction
Describe two ways of measuring reaction rates in a reaction that produces a gas
1) measure the gas formed
2) measure the gas lost
