C2- Rates and Energy Flashcards
How can we use a graph of amount of product against time to tell us the rate of reaction at a given time?
Gradient or slope of line at any given time.
The steeper the slope/gradient, the faster the reaction.
What is the collision theory?
The collision theory states that reactions can only happen if particles collide.
However, just colliding is not enough. The particles must collide with enough energy.
What do we call the minimum amount of energy needed for particles to react?
Activation energy.
What 3 main factors affect the rate of reaction?
- Temperature.
- Concentration of reactants/Pressure of gases.
- Surface Area of solids.
Also, if a catalyst is used.
How can surface area increase the rate of reaction?
Increasing the surface area (making pieces smaller) increases the frequency of collisions. This means there are more collisions happening at the same time and this increases the rate of reaction.
How can temperature increase rate of reaction?
As temperature increases, so does the rate of reaction.
With a higher temperature, particles have more energy➡️collide more frequently and more energetically➡️higher chance of successful collisions.
How can concentration/pressure increase rate of reaction?
As concentration/pressure increases, so does the rate of reaction.
Increased concentration/pressure means there are more particles in the same volume, so the particles are closer together➡️collide more frequently➡️higher chance for successful collisions.
Why can catalysts be used over and over again?
The catalyst is not used up in the reaction.
What does a catalyst do?
A catalyst speeds up the rate of a chemical reaction by lowering the activation energy, so less energy is needed and more collisions are successful.
What are the benefits of using catalysts in industrial processes?
- Catalysts increase rate of reactions, so reduce energy costs.
- Reduces impacts on the environment➡️If fossil fuels are burnt to provide the energy, using catalysts will help conserve resources and reduce pollution.
What two areas of research offer possibilities for new or better catalysts?
- Nanoparticles➡️New, highly efficient catalysts.
- Enzymes= Biological catalysts➡️Work at ordinary temperatures➡️Further reduce energy costs.
Define exothermic reactions.
A reaction in which energy is transferred from the reacting substances to their surroundings.
Give 2 examples of exothermic reactions.
- Combustion➡️Burning fuels.
- Oxidation reactions➡️e.g: respiration.
- Neutralisation reactions➡️Involving acids and bases.
Define endothermic reaction.
A reaction in which energy is transferred to the reacting substances from their surroundings.
How can we calculate the rate of reaction?
- Rate= Amount of reactant used/ time.
- Rate= Amount of product formed/ time.
In reversible reactions, the amount of energy released is…
Exactly equal both when the reaction goes in one direction, and when the reaction goes in the opposite direction.
