Rate Of Reaction Flashcards
Collision theory: Why does rate of reaction change over time?
- Concentration of reactants decreases
- At the beginning, chance of successful collisions is higher
- As reactants are used up, collision rate decreases
Collision theory: temperature changes the rate of reaction. Explain. (3 marks)
- Temperature increases, energy of particles increases
- More collisions have energy above activation energy
- Successful collisions are more frequent
Why is it important that solutions added into the flask have the same temp?
Otherwise a temperature change would occur on adding the other solution which had nothing to do with the reaction
How to monitor rate of reaction (coloured product, H+ produced, gas produced)?
Use a colorimeter to measure colour changes with time
Use a pH meter to measure pH changes with time
Use a gas syringe / collect gas over water to measure changes in volume with time
Use a balance to measure mass changes with time
How would the rate of reaction be affected if chloroalkane is replaced by bromoalkane? (3 marks)
Rate would be faster because C—X bond needs to be broken (1)
C—Br is weaker than C—Cl / takes less energy to break (1)
This outweighs effect of greater dipole in C—Cl / chlorine being more electronegative (1)
How to determine which one is a better catalyst? (4 marks)
measure volume of gas at a particular time / time how long it takes to produce a fixed volume
use the same amount of catalyst
use the same volume of the same concentration of reactant
better catalyst increases rate by more
Explain why a change in concentration affects the rate of reaction. (2 marks)
at higher concentration, more particles in a given volume / particles closer together (1)
more frequent collisions / more chance of collisions (1)
Thiosulfate cross method: why is it necessary to keep the volume the same?
To ensure same depth of liquid above the cross
