Rates of reaction Flashcards
What is the rate of reaction
A measure of how quickly a reactant is used up, or a product is formed
What is a successful collision
A collision that produces a reaction
What is activation energy
The minimum energy required for a reaction to take place between reacting particles
How do particles collide
Two pairs of particles move towards each other
The pairs collide and reform so that each member of the original pair joins with a member of the other pair, forming two new pairs
The new pairs are now moving away from each other
How do you calculate the mean rate of reaction
mean rate of reaction = quantity of reactant used / time taken
mean rate of reaction = quantity of product formed / time taken
How to read a rate of reaction graph
Steep - a greater rate of reaction
Horizontal - finished
What are the factors affecting the rate of reaction and how do they do it
Concentration
Pressure
Surface area
Temperature
Speed up the rate of reaction
Why does concentration, pressure, surface area and temperature affect the rate of reaction
Concentration - there are more particles to react with each other which causes more frequent collisions
Pressure - the particles have less room to move around which causes more successful collision
Surface area - there is more space for the particles to collide which causes more successful collision
Temperature - the particles have more energy when they collide which causes more frequent collisions
What is a catalyst and how do they work
A substance that increases the rate of chemical reactions but aren’t used up during the reaction
Provides an alternative reaction pathway that has a lower activation energy than the uncatalyzed reaction
Required practical : Measure the production of gas
What is the method
Support a gas syringe by a clamp
Using a measuring cylinder, add 50cm^3 of dilute hydrochloric acid to a conical flask
Add 0.4g of calcium carbonate into the flask and connect it with a gas syringe and start a timer
Every 10s, record the amount of gas produced
Repeat these steps with different concentrations
Required practical : Investigate the rate of reaction by colour change
What is the method
Measure 50 cm³ of sodium thiosulphate solution in a conical flask using a measuring cylinder
Place the conical flask on piece of paper with a cross
Add 10 cm³ of dilute hydrochloric acid to the conical flask with a different measuring cylinder. Immediately swirl the flask to mix its contents, and start a timer
Have one person watch the cross until it disappears
Measure and record the temperature of the reaction mixture
Repeat with different temperatures of sodium thiosulphate solution
What is a reversible reaction
A chemical reaction that can go both ways, e.g. A + B ⇌ C + D
What is the dynamic equilibrium
The rate of the forward reaction equals the rate of the reverse reaction. This happen in a closed system
What is Le Chatelier’s principle
If a change is made to the conditions of a system at equilibrium, the position of the equilibrium moves to oppose that change in conditions
What happens when you change the pressure or temperature in an equilibrium
Increase pressure - moves to the side with fewer molecules
Decrease pressure - moves to side with more molecules
Increase temperature - favours the endothermic reaction (shifts to the left)
Decrease temperature - favours the exothermic reaction (shifts to the right)
