Assertion: The order of a reaction can be zero or fractional.
Reason: We cannot determine the order from a balanced chemical equation.
Assertion: The order of a reaction can be zero or fractional.
Reason: We cannot determine the order from a balanced chemical equation.
Analysing the assertion
Let’s consider the reaction
\(aA + bB \rightarrow Product\)
The rate law expression:
rate of reaction \(= k[A]^a[B]^b\)
We can determine the order of the reaction by adding the powers of the concentration terms of the reactants in the rate law expression.
The order of a reaction is determined experimentally. The order of a reaction may be zero or fractional.
So, the assertion is a correct statement.
Analysing the reason
We cannot determine the order of a reaction by taking into consideration the balanced chemical equation, as the order is determined experimentally.
For example, a complex reaction occurs in multiple steps. The rate and the order of the complex reaction are dependent on the slowest step of the reaction. So, in such cases, the order is not completely dependent on the balanced chemical equation.
Example: As reactions can be multi-stepped, the rate of reaction is determined by the slowest step.
\(KClO_3 + 6FeSO_4 + 3H_2SO_4\)
\(\downarrow\)
\(KCl + 3H_2O + 3Fe_2(SO_4)_3\)
The given reaction appears to be a tenth order reaction, but it is a second-order reaction.
"Thus, we cannot determine the order of a reaction from it balanced chemical equation."
"So, the reason is a correct statement."
"Hence, option \((B)\) is correct."
Analysing the assertion
Let’s consider the reaction
\(aA + bB \rightarrow Product\)
The rate law expression:
rate of reaction \(= k[A]^a[B]^b\)
We can determine the order of the reaction by adding the powers of the concentration terms of the reactants in the rate law expression.
The order of a reaction is determined experimentally. The order of a reaction may be zero or fractional.
So, the assertion is a correct statement.
Analysing the reason
We cannot determine the order of a reaction by taking into consideration the balanced chemical equation, as the order is determined experimentally.
For example, a complex reaction occurs in multiple steps. The rate and the order of the complex reaction are dependent on the slowest step of the reaction. So, in such cases, the order is not completely dependent on the balanced chemical equation.
Example: As reactions can be multi-stepped, the rate of reaction is determined by the slowest step.
\(KClO_3 + 6FeSO_4 + 3H_2SO_4\)
\(\downarrow\)
\(KCl + 3H_2O + 3Fe_2(SO_4)_3\)
The given reaction appears to be a tenth order reaction, but it is a second-order reaction.
"Thus, we cannot determine the order of a reaction from it balanced chemical equation."
"So, the reason is a correct statement."
"Hence, option \((B)\) is correct."
