4 Rates and energy Flashcards
What is the first way we can find out the rate of a chemical reaction?
By following the amount of reactants used up over time
What is the second way we can find out the rate of a chemical reaction?
By following the amount of products made over time
What is the rate of reaction equation?
time
What does the slope of a line on a graph tell us?
The rate of reaction at any given time
e.g. the steeper the slope the faster the rate of reaction
What are the four main factors affecting the rate of chemical reactions?
Temperature
Surface area
Concentration of solutions or pressure of gases
Presence of a catalyst
What is the collision theory?
- Reactions can only take place when particles of reactants come together
- The reacting particles don’t just have to bump into each other
- They also need enough energy to react when they collide
What is the activation energy?
The smallest amount of energy that particles must have before they can react
When are reactions more likely to happen between reactant particles?
If we…
- increase the chance of reacting particles colliding with each other
- increase the energy that they have when they collide
This increases the rate of reaction as well
How does a larger surface area increase the rate of reaction?
Higher surface area will increase the amount of reactant exposed so more collisions can occur (frequency not energy)
How does a higher temperature increase the rate of reaction?
Particles have more energy so they can move faster and collide more often- this means a greater activation energy and more successful collisions
How does a higher concentration/pressure increase the rate of reaction?
It increases the frequency of collisions between the particles
How can we tell if a reaction has occurred?
- gas released (bubbles present) so you can measure the volume produced
- change in mass
- colour change
- change in pH
- temperature change
How does the presence of a catalyst increase the rate of reaction?
It speeds up the rate of reaction but is not used up during the chemical reaction and different ones are required for different reactions
Why are catalysts used in industry?
To increase the rate of reaction and reduce energy costs
It also saves money in the long term even if it is an expensive substance because it doesn’t need to be replaced for a long time and saving energy also saves money
What are traditional catalysts generally made from and what is a potential downside?
Transition metals or their compounds
Can be toxic or harm the environment if they escape
