Rate of Reaction Flashcards
What are the 3 ways of measuring rate ?
Bunged flask on balance
Conical flask and gas syringe
White paper with a cross
Describe the bunged flask method
Put a flask on balance
Add reactants and quickly bung w cotton wool
Measure how mass of reactants changes with time as gas is produced and escapes the flask
Describe the conical flask and gas syringe method
Add reactants (HCl & marble chips) to a flask and quickly bung with a tube going through attached to a syringe
Measure how long it takes for a certain amount of gas to be produced
OR
how much gas is produced in a certain time
Describe the white paper with a cross method
Works when mixing 2 clear solutions to make a precipitate
Put the flask on top of the cross
Add reactants
Measure how long it takes for the cross to disappear (subjective)
What is collision theory?
A reaction will only occur if colliding particles have energy greater than activation energy
Define activation energy
The minimum energy required for a successful reaction
What are the five ways to speed up reactions and how do they work?
Increase:
SA/conc/pressure/temp (increase no. collisions)
Temp/catalyst (increase energy of particles)
What is the effect of temperature/concentration/pressure on rate?
More particles exposed so more frequent collisions
So more frequent successful collisions
Therefore rate increases
What is the effect of temperature on rate?
Higher temperature means particles have more energy
Therefore particles move faster and more particles have energy greater than activation energy
A greater proportion of collisions are successful
Therefore rate increases lots
What is the effect of catalysts on rate?
They provide an alternative route for the reaction with a lower activation energy therefore there is a higher chance a particle will have activation energy
Why are catalysts used in industry?
Reactions happen at the same rate (ish) but at a lower temperature therefore less energy is needed so less cost
Define rate of reaction
The relative time for reactants to turn into products
| ———- | ~ | % | / | / | / | /\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ What does the sharp incline mean if the left axis is amount of product ? Why?
Fast reaction
There are lots of particles at the start
High concentration means more frequent collisions means more frequent successful collisions means higher rate
What actually is activation energy tho?
The amount of energy needed to break the old bonds of the reactants
How much energy relatively is used in an exothermic reaction?
More energy released in forming the new bonds than is used in breaking the old bonds.
Therefore net gain of energy.
