Chemistry NCERT Exemplar Solutions Class 12th Chapter Four

This is a Multiple Choice Questions as classified in NCERT Exemplar

Correct options: B, C and D

Catalysts reduce the activation energy of a process and give an alternate path by reducing or raising the activation energy between reactants and products, altering the reaction's enthalpy change. As a result, B, C, and D statements are the proper responses

This is a Multiple Choice Questions as classified in NCERT Exemplar

Correct options: A and B

Arrhenius equation k = Ae – $\frac{{\mathbf{E}}_{\mathbf{a}}}{\mathbf{R}\mathbf{T}}$

When the temperature rises, $\frac{{\mathbf{E}}_{\mathbf{a}}}{\mathbf{R}\mathbf{T}}$ value falls and – $\frac{{\mathbf{E}}_{\mathbf{a}}}{\mathbf{R}\mathbf{T}}$

As a result, e- $\frac{{\mathbf{E}}_{\mathbf{a}}}{\mathbf{R}\mathbf{T}}$  increases, and it is certain that k and  T increases as well. As a result, Option A is proven.

Catalyst increases the rate of reaction by lowering the activation energy. Thus option B is also correct. 

This is a Multiple Choice Questions as classified in NCERT Exemplar

Correct options: A and D

According to the graph, the area under the cure must not vary as the temperature rises.T2 > T1

The energy level of T2 is higher than T1.

This is a Multiple Choice Questions as classified in NCERT Exemplar

Correct options: A and C

The Maxwell Boltzmann distribution, often known as the Gibbs distribution, is a measure that expresses the likelihood of a system being in each state as a function of the energy of that state.

Look at the graph.

T₂ > T₁

The fraction of molecules falls as the temperature rises because the area under the curve shrinks.

This is a Multiple Choice Questions as classified in NCERT Exemplar

Correct options: A and D

Activation Energy is the amount of energy released when reactant molecules collide and form an activated complex. When energy is released, the complex decomposes into a product.

This is a Multiple Choice Questions as classified in NCERT Exemplar

Correct options: A, C and D

The pressure in this reaction is extremely high, and it becomes independent of the ammonia concentration. The metal surface becomes saturated with gas molecules when the rate of reaction=Rate constant. The rate of a zero-order reaction is independent of the concentration of reactants in the reaction.

This is a Multiple Choice Questions as classified in NCERT Exemplar

Correct options: A and D

A complex reaction is one that does not happen in a single step.

The total number of molecules involved in the slowest step of the reaction determines the overall reaction rate.

Correct options: A and B

This is a Multiple Choice Questions as classified in NCERT Exemplar

Unimolecular reaction: Unimolecular means relating to a single molecular reaction that describes decomposition of a single reactant.

If product A→ (B)

rate = k [A]

Example Na₂O₄ (g)→2No₂ (g)

Order = 1

Molecularity = 1

The slowest step is the rate determining which determines the Order and Molecularity.

This is a Multiple Choice Questions as classified in NCERT Exemplar

Correct options: A and D 

Elementary reaction: It is a reaction that occurs in a single step.

Here we must understand about the Order and Molecularity.

Molecularity of a reaction = number of reacting species (collide to bring a chemical reaction).

Discussing about the Order, Rate law is used in Order and how do we equate shall be seen in the next step

rate = k [A] ^α [B] ^β

For a balanced chemical equation of an elementary reaction Order and Molecularity is same and can never be 0. 

This is a Multiple Choice Questions as classified in NCERT Exemplar

Correct options : A, C and D.

Rate law = Experimental rate of the reaction

Suppose aA + bB→cC + dD

Then rate = k [A] ^α [B] ^β

Here instead of using complex reaction we use elementary reaction which gets solved in one step