Rate of Reactions Flashcards
What are the equations for calculating the rate of reactions?
Mean rate of reactions = Quantity of reactants/time
Or
Mean rate of reactions = Quantity of product formed/time
What is time and quantity measured in?
Time is measured in seconds (s) Quantity: Mass is measured in grams (g) Volume is measured in cubic centrimetres (cm^3) Amount is measured in moles (mol)
What is collision theory?
Chemical reactions can only occur when reacting particles collide with each other with sufficient energy
What is activation energy?
The minimum energy required to start a chemical reaction (for a collision to be successful)
What is a successful collision?
A collision between reactant particles that has energy greater than or equal to the activation energy
What are the five factors that affect the rate of reaction?
Temperature Concentration Surface area Pressure Catalyst
How does increasing temperature increase the rate of reaction?
Particles have more energy to move faster
More particles had energy greater than the activation energy
More successful collisions per unit time
Therfore, increase in rate of reaction
How does increasing concentration increase rate of reaction?
More particles per unit volume
More successful collision per unit time
Therefore, increase in rate of reaction
How can you increase pressure?
Add more particles
Reduce size of container
How does increasing pressure increase the rate of reaction?
Gas particles are closer together
More successful collision per unit time
Therefore, increase in rate of reaction
How does increasing surface area increase rate of reaction?
Increase the surface area to volume ratio
More particles on the surface are exposed
More successful collisions per unit time
Therefore, increase rate of reaction
What’s a catalyst?
A substance that increases the rate of a chemical reactions without being used up in the process
How does using catalysts increase the rate of reaction?
They provide an alternative reaction pathway
- reduces the amount of energy needed for a successful collision
More particles have enough energy to react
More successful collisions per unit time
Therefore, increase in rate of reaction
How do you calculate the mean rate of reaction from a graph?
Calculate the gradient of the line:
Gradient = difference in the amount of product formed or reactant used/time
How do you calculate the rate of reaction at a particular time given by graphs?
Draw a tangent to the curve at the time given
Find the gradient of the tangent
The gradient is the rate of reaction at that time
