Reaction Kinetics Flashcards
why did the graph not pass through the origin (note that graph has to pass thru the origin to determine ROR)
due to experimental errors
why must the conc of [other reactants] be around 10 times more than [x]
so that the concentrations of the other reactants are large and does not change much during the reaction and hence the rate of reaction is pseudo zero order wrt to these other reactants and is only dependent on the conc of x
what is the purpose of quenching the solution by adding
- acid / base reactants
- cold and large volume of water
- is to neutralise the acid / base reactant / catalyst present
- large volume of water added to dilute the solution and this results in lower concentration of reactants and reactant particles to be further apart from each other, and low temp is used to reduce the average kinetic energy of the particles, so overall, the particles would collide with each other less frequently and less frequency of effective collisions, hence the ROR would be slower and the colour change would be more obvious during the titration
explain why slow return of colour observed after I2/Na2S2O3 titration completed
because the temperature of the solution is still low and the kinetic energy and concentration of reactants FOR THE REVERSE REACTION is low, and since it takes some time for the temp of the solution to increase, the proportion of reactant particles that have the kinetic energy greater of equal to the activation energy for the reaction is low and hence the slow ROR of the reverse reaction where the I- gets oxidised by the atmospheric oxygen to I2
expected OOR to be 1st but why is it not
due to random error from the expt such as loss of gas
apart from loss of gas why is there a difference in the gas collected and max volume calculated and how to overcome it ?
some co2 may have dissolved in the water due to long expt (SO?) the expt value lower than theoretical one
use a gas syringe
why is the total volume of mixture kept constant (for clock reactions)
so that the initial concentration of each reactant is directly proportional to its volume used
what is the significance of the term 1/t s-1
it represents the initial rate of reaction
why is the volume of the fa5 a measure of [fa5]
because the total volume of mixture and conc of fa5 is kept constant
since rate prop to 1/t and conc x prop to vol x, rate prop to [conc x]^2 and OOR 2 order wrt to x
yea
why is a fixed and small amount of phenol used in each experiment
We keep the amount of phenol small, so that we are measuring the time taken to produce a small amount of bromine and extent of reaction is small
If extent of reaction is small, we can use the approximation: rate approx TRIANGLE [product] / TRIANGLE t
The amount of phenol is fixed so that for each experiment, we are measuring the time
taken for a fixed amount of Br2 to be produced
This makes TRIANGLE[product] a constant for each experiment, so that rate approx k / TRIANGLE t and rate approx 1/TRAINGLEt
reason for slow rxn
repulsion between 2 negatively charged ions causes the Ea of reaction to be high
why does the reaction mixture contain both conj base and acid or vice versa
they create a buffer solution to keep the pH of the solution relatively constant so that the {H+} does not change and affect the rate of reaction
