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प्रश्न
Distinguish between Order and Molecularity of reaction.
Distinguish between molecularity and order of reaction.
उत्तर १
| Order | Molecularity | |
| i. | It is an experimentally determined property. | It is a theoretical entity. |
| ii. | It is the sum of powers of the concentration terms of reactants that appear in the rate equation. | It is the number of reactant molecules taking part in an elementary reaction. |
| iii. | It may be an integer, fraction, or zero. | It is an integer. |
| iv. | It is not based on a balanced chemical equation. |
It is based on a balanced chemical equation. |
उत्तर २
| Sr. No. | ORDER OF A REACTION | MOLECULARITY OF A REACTION |
| 1. | It is sum of the concentration terms on which the rate of reaction actually depends or it is the sum of the exponents of the concentrations in the rate law equation. | It is the number of atoms, ions or molecules that must collide with one another simultaneously so as to result into a chemical reaction. |
| 2. | It need not be a whole number i.e. it can be fractional as well as zero. | It is always a whole number. |
| 3. | It can be determined experimentally only and cannot be calculated. | It can be calculated by simply adding the molecules of the slowest step. |
| 4. | It is for the overall reaction and no separate steps are written to obtain it. | The overall molecularity of a complex reaction has no significance. It is the only slowest step whose molecularity has significance for the overall reaction. |
| 5. | Even the order of a simple reaction may not be equal to the number of molecules of the reactants, as seen from the unbalanced equation. | For simple reactions, the molecularity can usually be obtained from the stoichiometry of the equation. |
| 6. | It may be an integer, fractionor zero | It is always an integer and never a fraction or zero. |
Notes
Students should refer to the question according to their preferred marks.
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संबंधित प्रश्न
Answer the following in one or two sentences.
What is the relationship between coefficients of reactants in a balanced equation for an overall reaction and exponents in the rate law? In what case the coefficients are the exponents?
Answer the following in one or two sentences.
What is the rate-determining step?
A reaction takes place in two steps:
- \[\ce{NO_{(g)} + Cl2_{(g)} -> NOCl2_{(g)}}\]
- \[\ce{NOCl2_{(g)} + NO_{(g)} -> 2NOCl_{(g)}}\]
- Write the overall reaction.
- Identify the reaction intermediate.
- What is the molecularity of each step?
Which of the following is a unimolecular reaction?
Name the slowest step that determines the rate in a complex reaction.
Define molecularity.
Write an expression for instantaneous rate of reaction:
2N2O(g) → 4NO2(g) + O2(g).
What is the order of reaction?
Why is molecularity applicable for only elementary reactions whereas order of a reaction is applicable for elementary and complex reactions? Explain with suitable examples.
For a zero-order reaction, molecularity can never be equal to zero. Explain.
Give one example of the reaction where order and molecularity are the same.
Mention any two factors that influence the rate of chemical reaction.
If for the reaction A → products, a straight line graph passing through origin is obtained between the rate of reaction against concentration of A, what would be the order of reaction? Why?
For the elementary reaction
\[\ce{2SO2(g) + O2(g) -> 2SO3(g)}\], identify the correct among the following relations.
The rate determining step of a reaction is the step ____________.
The reaction \[\ce{2NO2Cl_{(g)} -> 2NO2_{(g)} + Cl2_{(g)}}\] takes place in two steps as
(i) \[\ce{NO2Cl_{(g)} -> NO2_{(g)} + Cl_{(g)}}\]
(ii) \[\ce{NO2Cl_{(g)} + Cl_{(g)} -> NO2_{(g)} + Cl2_{(g)}}\]
Identify the reaction intermediate.
A chemical species that is formed in one elementary step in the mechanism of complex reaction and consumed in the subsequent step is called ____________.
Consider the following elementary reaction;
\[\ce{2AB_{(g)} -> A2_{(g)} + B2_{(g)}}\]
The molecularity of the reaction is ____________.
A reaction involving two different reactants can never be a ______
Identify the molecularity of following elementary reaction:
NO(g) + O3(g) → NO3(g) + O(g)
The reaction takes place in two steps as
(i) \[\ce{NO2Cl(g) ->[k1] NO2(g) + Cl(g)}\]
(ii) \[\ce{NO2Cl(g) + Cl(g) ->[k2] NO2(g) + Cl2(g)}\]
Identify the reaction intermediate.
A certain reaction occurs in two steps as
(i) \[\ce{2SO2(g) + 2NO2(g) -> 2SO3(g) + 2NO(g)}\]
(ii) \[\ce{2NO(g) + O2(g) -> 2NO2(g)}\]
In the reaction:
What is an elementary reaction?
How does a catalyst differ from reaction intermediate?
A complex chemical reaction takes place in two steps.
Step I: NO(g) + O3(g) → NO3(g) + O(g)
Step II: NO3(g) + O(g) → NO2(g) + O2(g)
The predicted rate law is rate = k[NO][O3]
- Identify the rate determining step.
- Name the reaction intermediate/s. Why is/are it/these intermediate/s?
Define molecularity of reaction.
