Question

The order of a reaction having rate constant \[1.34 \times {10^{ - 3}}{\text{mol }}{{\text{L}}^{{\text{ - 1 }}}}{\text{se}}{{\text{c}}^{\text{ - }}}^{\text{1}}\] will be:
A) 0
B) 2
C) 1
D) 3

Answer 1

Hint:The order of the reaction is defined as the number of molecules whose concentration alters as a result of chemical change. It is an experimental property. We can determine the order of reaction from the unit of the rate constant.


Complete solution:
The rate of reaction is the change in concentration of reactant or product in unit time.
The order of reaction may be defined as the number of molecules whose concentration alters as a result of chemical change. In other words, it is some of the concentration of reactants in the rate law equation. It determines the rate and kinetics of the reaction
The mathematical relation between the rate of reaction and the concentration of the reaction component is known as the rate law expression.
The relation between the rate of reaction and the concentration of the reaction component is explained by the proportionality constant. This proportionality constant is known as the rate constant. It is denoted by the symbol\[k\].
\[k = \dfrac{{{\text{Rate}}}}{{{{{\text{[Concentration]}}}^{\text{n}}}}}\]
. Here,
\[k\] = rate constant
\[n\]= order of reaction
Concentration is always expressed in molarity that is nothing but \[{\text{mol }}{{\text{L}}^{{\text{ - 1 }}}}\]. As the rate of reaction changes in concentration per unit time so its unit is \[{\text{mol }}{{\text{L}}^{{\text{ - 1 }}}}{\text{se}}{{\text{c}}^{\text{ - }}}^{\text{1}}\].
Now we will determine the unit of the rate constant for zero order reaction.
For a zero order reaction \[n\] is zero. So substituting the units of rate and concentration we can determine the unit of the rate constant.
\[k = \dfrac{{{\text{mol }}{{\text{L}}^{{\text{ - 1 }}}}{\text{se}}{{\text{c}}^{\text{ - }}}^{\text{1}}}}{{{{{\text{[mol }}{{\text{L}}^{{\text{ - 1 }}}}{\text{]}}}^0}}}\]
\[k = {\text{mol }}{{\text{L}}^{{\text{ - 1 }}}}{\text{se}}{{\text{c}}^{\text{ - }}}^{\text{1}}\]
Thus, the unit of zero order reaction is \[{\text{mol }}{{\text{L}}^{{\text{ - 1 }}}}{\text{se}}{{\text{c}}^{\text{ - }}}^{\text{1}}\].
So, the order of a reaction having rate constant \[1.34 \times {10^{ - 3}}{\text{mol }}{{\text{L}}^{{\text{ - 1 }}}}{\text{se}}{{\text{c}}^{\text{ - }}}^{\text{1}}\] will be 0.
Thus, the correct option is (A).

Note:To determine the rate law of reaction it is necessary to calculate the order of the reaction.We can determine the order of reaction from the unit of rate constant value as each order of reaction has a different unit of rate constant.