What is the difference between average rate, initial rate, and instantaneous rat
ID: 478700 • Letter: W
Question
What is the difference between average rate, initial rate, and instantaneous rate? Ozone decomposes to oxygen according to the equation 2O_3(g) rightarrow 3O_2(g). Write the equation that relates the rate expressions for this reaction in terms of the disappearance of O_3 and the formation of oxygen. In the nuclear industry, chlorine trifluoride is used to prepare uranium hexafluoride, a volatile compound of uranium used in the separation of uranium isotopes. Chlorine trifluoride is prepared by the reaction Cl_2(g) + 3F_2(g) rightarrow 2ClF_3(g). Write the equation that relates the rate expressions for this reaction in terms of the disappearance of Cl_2 and F_2 and the formation of ClF_3.Explanation / Answer
1)
Rate of reaction: The rate of a chemical reaction is the change in concentration over the change in time and is a metric of the "speed" at which a chemical reactions occurs and can be defined in terms of two observables:
The Rate of Disappearance of Reactants
The Rate of Formation of Products
Initial rate of Reaction: The initial rate of a reaction is the instantaneous rate at the start of the reaction (i.e., when t = 0). The initial rate is equal to the negative of the slope of the curve of reactant concentration versus time at t = 0.
Average rate of Reaction:
The average rate of reaction, as the name suggests, is an average rate, obtained by taking the change in concentration over a time period. It is generally considered over a period of time and most commonly calculated where reaction rates are to be required.
It can be calculated as,
Rate = - reactants/time; -ve sign denotes that reactants are being consumed.
Or Rate = product/time
Instantaneous rate of Reaction:
It is calculated for the change of concentration over very small interval of time.
It can be calculated as,
2)
We know that Ozone is an unstable allotrope of oxygen, thus it decomposes as;
2O3 3O2
Now, experimental data have shown that this is two step reaction, can be given by.
O3 O2+ O
O + O3 2 O2 Rate determining step.
Now, writing the rate law for the first equation (equilibrium)
Now, substituting the value of [O] from the above equation to the rate law expression using the second reaction.
3)
Rate of reaction for preparation of Chlorine tri-fluoride can be given as;
Cl2(g)+3F2(g)2ClF3(g)
Rate = +(1/2) (ClF3/t) = -(1/3) (F2/t) = -(Cl2/t)
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