16.4 rate equations & reaction mechanisms

Question 1

what is the rate determining step?

Answer 1

slowest step in multi-step reaction

Question 2

what reactants will be present in a rate-determining step?

Answer 2

reactants/substances derived from in rate equation

Question 3

what determines the order of reactant in a slow step?

Answer 3

number of molecules

Question 4

describe how the experiment of iodine & propanone is carried out.

Answer 4

small samples are removed in time intervals & quenched with excess NaHCO3 -> neutralises H+ & stops reaction
the sample is titrated with Na2S2O3 with starch catalyst

Question 5

give the equation of iodine & propanone.

Answer 5

CH3COCH3 + I2 + H+ -> CH3COCH2I + I-

Question 6

give the equation of the titration of Na2S2O3 with iodine.

Answer 6

2 S2O3 2- + I2 -> 2 I- + S4O6 2-

Question 7

what will be the colour change of the titration of Na2S2O3 with iodine?

Answer 7

yellow/brown -> colourless

Question 8

why must there be 2+ steps in a reaction if there is a zero-order reactant?

Answer 8

zero-order reactant does not involve in rate-determining step

Question 9

what does SN2 stands for & which type of halogenoalkanes react through it?

Answer 9

nucleophilic substitution, 2 species involved in rate determining step

-> primary & secondary

Question 10

why does tertiary halogenoalkanes react differently compared to primary halogenoalkanes?

Answer 10

methyl groups are e- releasing & prevents OH- from attacking like SN2