Topic 7- Rates of reaction and energy changes (with spec) paper 2 Flashcards
How could you describe the rate of a reaction?
The rate of formation of a product or the rate of removal of a reactant.
What is the formula for rate of reaction?
amount of reactant used or amount of product formed ÷ time
What are three ways you can measure the rate of a reaction?
Precipitation (mixing two solutions and putting it on a cross), change in mass or volume of gas given off
What does having finer particles mean for the rate of the reaction?
It means that it has a larger surface area so it’ll be quicker.
What needs to happen for a reaction to take place?
The particles need to collide. They need to collide with enough energy to react. The activation energy is the minimum energy needed.
How does concentration affect rate of reaction?
If a solution is more concentrated it increases the rate because more particles are reactant in the same volume. This makes collisions more likely.
What factors do reactions depend on?
Temperature, concentration and the size of the particles
What does the rate of reaction depend on?
How often particles collide and the energy transferred during a collision.
How does temperature affect rate of reaction?
- particles move faster so will have more collisions
- the particles will gain energy meaning there will be more successful collisions
How does having a large surface area affect rate of reaction?
- particles will have more area to work on sos the frequency of collisions will increase
- rate is faster for solids with a larger surface area to volume ratio
What is a catalyst?
A substance that increases the rate of a reaction without being chemically changed or used up in the reaction.
What are three advantages of using catalysts?
- speeds up the reaction
- reduces energy use
- use more than once
How do catalysts work?
Decreasing the activation energy needed for the reaction to take place. They provide an alternative reaction pathway that has a lower activation energy.
What is activation energy?
the minimum energy needed to start a reaction.
What are enzymes?
Biological catalysts that speed up chemical reactions in living cells. They are used to catalyse reactions like respiration and photosynthesis.