1) For an irreversible reaction A ----> 2B, the rate is increased by four times when the concentration of A is doubled. The incorrect statement about this reaction is:
Answers
Answer:
1) It is a second order reaction.
2) Half life is independent of initial concentration of A.
3) The unit of the specific rate, k is L mol-1 s-1.
4) Half life is inversely related to the initial concentration of A.
Logic:
Except one, the remaining three statements are correct regarding the given reaction. The logic is to find out the order of reaction comparing the rates at different concentrations.
Solution:
The rate law for a given reaction reaction can be written as follows:
rate law
where:
k = specific rate
[A] = concentration of reactant, A
n = order of reaction
Let
the initial rate: r1 = k[A1]n
the rate after doubling the conc. of A: r2 = k[A2]n
Also we know that:
[A2] = 2[A1] (since the concentration of A is doubled)
and
r2 = 4r1 (since the rate is increased by four times)
Now by comparing rates at two different conditions, it is possible to find the order of the reaction.
comparison of rates
or
4 = 2n
Therefore:
n = 2
That means given reaction is a second order reaction.
* Now we know that for a second order reaction, the half life is inversely proportional to the initial concentration of the reactants and the units of specific rate can be written as: L mol-1 s-1.
In general:
half life