4.6.1 Rate and extent of chemical change (must know) PAPER 2 Flashcards
Factors that effect rate
Temperature
Surface area
Concentration
Pressure
How is the rate of reaction calculated
amount of reactant used or product formed / time
moles of reactant used or product formed / time
Describe measuring rate by mass lost
Place the reaction flask on a balance
In these reactions a gas is given off, so record the decrease in mass in time intervals
Plot a graph of mass vs time
How to measure the rate by monitoring the volume of a gas
Connect a gas syringe to a reaction flask and measure the volume of gas formed in time intervals
Plot a graph of volume vs time
How to find rate at some point from a graph of amount of reactant vs time
Draw a tangent at the corresponding time
Work out the gradient
What is collision theory
Chemical reactions can occur when reacting particles collide with each other with sufficient energy
Describe and explain the effect of increasing temperature on the rate of reaction
T increases = faster reaction
As T increases, kinetic energy of particles increases, they move faster and there are more frequent collisions
NOT DIRECT PROPORTION
Describe and explain the effect of increasing concentration on the rate
Conc increases = faster reaction
More reacting particles available, more frequent collisions
Describe and explain the effect of increasing pressure of a gas on the rate of reaction
More reacting particles available so more frequent collisions
Increases rate
Describe and explain the effect of increasing surface area
Increases frequency of collisions and so increases rate
What is a catalyst and how does it work
How does it affect the reaction profile
It changes the rate of reaction but is not used up. It increases the rate of reaction by providing a different pathway for the reaction that has a lower activation energy
The reaction profile for a catalysed reaction will have a lower maximum of the curve
What is an enzyme
A molecule that acts as a catalyst in a biological system
