Which of the following is not a correct statement ?

Options

A. Rate law can be deduced from the stoichiomatry of the reaction
B. The order of a reqaction with respect to a reactant is the power (exponent) of the concentration of the reactant to which the rate of the reaction is directly proportional.
C. The overall order of the reaction is the sum of the power (exponents) of the concentration of all the reactants in the rate law expression
D. The overall order of the reaction may be zero or even a faction, say, `0.5`.

Answer

A

Explanation

The rate always has units of concentration/time, but the units of the rate constant dpend on ht eoverall reaction of order.
For the general reaction `
`aA+bBrarrcC+dD` The rate constant may be written as `k("rate")/([a]^(x)[B]^(y])`
if `x+y=n` , i.e., the overall order of the reaction is `n` , then the dimension of rate constant depend on the reaction. Thus, the dimension of `k` are equal to
`("concentration")/("time"xx["concentration"]^(n))=["concentration"]^(1-n)["times"]^(-1)`
If we choose concentration in molarity and the in second, than for
`n=0` , zero oder reaction `K` has the units mol `L^(-1)s^(-1)`
`n=1` , first oder reaction `K` has the units mol `s^(-1)`
`n=2` , second order reaction `K` has the units `(mol//L)^(-1)s^(-1)`
`n=3` , third oder reaction `K` has the units` (mol//L)^(-2)s^(-1)`
`n=n, nth order reaction `K` has the units `(mol//L)^(1-n)s^(-1)`
In every case, the dimensions of rate equal to `mol^(-1)s^(-1)` . Thus rate constant and reaction rate have identical units only for zero order reaction.
Units for time depend on how fast os slow is the reaction. For very fast reaction it may be choose in nano `(10^(-9))` or pico `(10^(-12))` seconds.