Shaillee Kaushal is teaching live on Unacademy Plus
XII-04 KINETICS II
RATE OF REACTION Average and instantaneous Rate Rate is usually expressed as the ratio of the amount of change in some quantity to the time required to produce that change. Change in some quantity AX Time taken for the change At Rate- Ax = Xfinal-Xinitial over a long time interval is called average rate.
T he rate measured for on infinitesimally small time interval is called instantaneous rate.
Average rate of a reaction Change in concentration of reactants or products Time taken for the change R= For example consider a reaction
Decrease in concentration of A Time taken R= Or Increase in concentration of B Time-taken At [B] At The negative sign in equation (i) signifies decrease in concentration of the reactants. The rate of the reaction is always positive.
2 2 uogenuaouoo
Expression of Rate:- Consider the following reaction between CO and NO2 CO + NO2 CO2 + NO Rate A 2H202 2H20 + 02 At At For the reaction 2 At 2 At
Question: Decomposition of N205 expressed by the equation N2052NO2 + 1/202 If during a certain time interval, the rate of decomposition of N205 is 1.8 x 10-3 mol L-1min-1 what will be the rates of formation of NO2 and 02 during the same internal?
d[N205] 1 ,[NO2] d[021 2 dt dt dt dt dt - 3.6 x 10-3mol L-1min-1 < 1.8 10-3-0.9 >< 10-"mol L-1min-1 dt 2 dt