RATES OF REACTION
ORDERS of reaction
From study mind
RATE EQUATION
From chemguide
Overall order of reaction (overall effect of concentrations of all reactants) = sum of
orders of reactants
UNITS OF RATE CONSTANT k
, from Unacademy
INITIAL RATE
Gradient of concentration-time graph at time=0
From continuous monitoring of the reactant
CLOCK REACTION
Measures how the time for the net amount of product to form varies as the
concentration of a reactant is changed
Assumptions:
● Concentration of each reactant doesn’t change significantly over the time period
of the reaction
● The reaction has not proceeded too far at endpoint
● Rate stays constant during the time period of the measurement = estimate initial
rate
IODINE CLOCK REACTION
H2O2 + 2I- + 2H+ → 2 H2O + I2
Sodium thiosulfate and starch added as an indicator (turns blue-black in presence of
iodine)
Iodine removed by Na2S2O3 as it forms
All Na2S2O3 used up: iodine forming stays in solution = starch indicator turns blue-
black
Measure time for the blue-black starch-iodine to appear
Initial rate proportional to 1/t
Graph of 1/t against concentration
Vary concentration of reactants to find the order of the reaction & rate equation
ORDERS of reaction
From study mind
RATE EQUATION
From chemguide
Overall order of reaction (overall effect of concentrations of all reactants) = sum of
orders of reactants
UNITS OF RATE CONSTANT k
, from Unacademy
INITIAL RATE
Gradient of concentration-time graph at time=0
From continuous monitoring of the reactant
CLOCK REACTION
Measures how the time for the net amount of product to form varies as the
concentration of a reactant is changed
Assumptions:
● Concentration of each reactant doesn’t change significantly over the time period
of the reaction
● The reaction has not proceeded too far at endpoint
● Rate stays constant during the time period of the measurement = estimate initial
rate
IODINE CLOCK REACTION
H2O2 + 2I- + 2H+ → 2 H2O + I2
Sodium thiosulfate and starch added as an indicator (turns blue-black in presence of
iodine)
Iodine removed by Na2S2O3 as it forms
All Na2S2O3 used up: iodine forming stays in solution = starch indicator turns blue-
black
Measure time for the blue-black starch-iodine to appear
Initial rate proportional to 1/t
Graph of 1/t against concentration
Vary concentration of reactants to find the order of the reaction & rate equation
