Rate Equations Flashcards
(29 cards)
What is the rate determining step?
Slowest step in a reaction
How does zero order affect RoR?
No effect - normally for reagents in excess
How does first order affect RoR?
Change is directly proportional
How does second order affect RoR?
Change made to concentration of reactants, RoR changes by this squared
A: First
B: Zero
How to track concentration of this equation?
- Collect H2 gas in gas syringe
- Measure volume produced
What is an initial rate method?
Multiple experiments, 1 reading/observation
2 examples of initial rate experiments?
- Gas syringe
- Iodine-clock
How to track concentration of this equation?
- Measure [NaOH] as its alkali
- Titrate with HCl OR use pH metre
A: First
B: First
A: First
B: Second
How to track concentration of this equation?
- Precipitate will make opaque solution
- Measure opacity of solution
How would you investigate the order of this reaction with respect to different reactants?
- Repeat using different conc. of reactants
- See if time taken to produce enough S ppt to obscure cross changes
In iodine-clock experiment, at what point in the reaction does the solution turn blue-black? (2)
- When enough I2 is produced to react with thiosulphate ions
- I2 now reacts with starch
Don’t have to add all reactants into 1 container simultaneously
Prevents reaction 1 from starting until ready to time it
ADD EQUATION
Which other reactants could be added last instead of hydrogen peroxide?
- Sodium Iodide
- Sulphuric Acid
Why is a constant volume of Na2S2O3 used?
So the amount of I2 produces same amount of blue-black colour
What is quenching? Why is it used?
- Slowing RoR down so reaction effectively stops
- Can stop reaction at any specific time so can analyse
Examples of quenching? Why? (3)
- Add large vol. of water - decrease reactant conc.
- Cool reaction - decrease no. reactant particles with lower Ea
- Remove catalyst by reaction of another chemical - increases Ea
Difference between continuous monitoring + initial rates?
Continuous - 1 experiment, multiple readings
Initial - Multiple experiments, 1 reading
Graph for continuous monitoring for zero order?
Graph for continuous monitoring for first + second order?
