मराठी
कर्नाटक बोर्ड पी.यू.सी.पीयूसी विज्ञान 2nd PUC Class 12

The value of rate constant of a pseudo first order reaction ______.

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प्रश्न

The value of rate constant of a pseudo first order reaction ______.

पर्याय

  • depends on the concentration of reactants present in small amount.

  • depends on the concentration of reactants present in excess.

  • is independent of the concentration of reactants.

  • depends only on temperature.

MCQ
रिकाम्या जागा भरा
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उत्तर

The value of rate constant of a pseudo first order reaction depends on the concentration of reactants present in excess.

Explanation:

Let's start with what a pseudo-first-order response is.

Although the pseudo-first-order reaction looks to be an order, it belong to another order. it's a second-order reaction because it involves two reactants.

Let's have a look at a reaction.

\[\ce{CH3Br + OH -> CH3OH + Br}\]

So, the rate law for the reaction is 

Rate = \[\ce{k[OH][CH3Br]}\]

Rate = \[\ce{k[OH][CH3Br] = k(constant) [CH3Br] = K' [CH3Br]}\]

Only the concentration of \[\ce{CH3Br}\] will change during the reaction and the rate will be determined by the reaction's modifications.

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पाठ 4: Chemical Kinetics - Exercises [पृष्ठ ५२]

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एनसीईआरटी एक्झांप्लर Chemistry Exemplar [English] Class 12
पाठ 4 Chemical Kinetics
Exercises | Q I. 19. | पृष्ठ ५२

संबंधित प्रश्‍न

A reaction is second order in A and first order in B.

(i) Write the differential rate equation.

(ii) How is the rate affected on increasing the concentration of A three times?

(iii) How is the rate affected when the concentrations of both A and B are doubled?

 


The following data were obtained during the first order thermal decomposition of SO2Cl2 at a constant volume :

SO2Cl2 (g) → SO2 (g) + Cl2 (g)

Experiment Time/s–1 Total pressure/atm
1 0 0.4
2 100 0.7

Calculate the rate constant.

(Given : log 4 = 0.6021, log 2 = 0.3010)


For the reaction:

\[\ce{2A + B -> A2B}\] 

the rate = k[A][B]2 with k = 2.0 × 10−6 mol−2 L2 s−1. Calculate the initial rate of the reaction when [A] = 0.1 mol L−1, [B] = 0.2 mol L−1. Calculate the rate of reaction after [A] is reduced to 0.06 mol L−1.


A reaction is first order in A and second order in B. Write the differential rate equation.


In a reaction between A and B, the initial rate of reaction (r0) was measured for different initial concentrations of A and B as given below:

A/mol L−1 0.20 0.20 0.40
B/mol L−1 0.30 0.10 0.05
r0/mol L−1 s−1 5.07 × 10−5 5.07 × 10−5 1.43 × 10−4

What is the order of the reaction with respect to A and B?


For a reaction R ---> P, half-life (t1/2) is observed to be independent of the initial concentration of reactants. What is the order of reaction?


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Rate law for the reaction \[\ce{A + 2B -> C}\] is found to be Rate = k [A][B]. Concentration of reactant ‘B’ is doubled, keeping the concentration of ‘A’ constant, the value of rate constant will be ______.


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Reason: A catalyst participating in the reaction, forms different activated complex and lowers down the activation energy but the difference in energy of reactant and product remains the same.


The role of a catalyst is to change


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The rate constant for the reaction \[\ce{2H2O5 -> 4NO2 + O2}\] is 30 × 10–5 sec–1. if the rate is 204 × 10–5 mol L1 S1, then the concentration of N2O5 (in mol1) is-


The rate of a chemical reaction double for every 10° rise in temperature. If the temperature is raised. by 50°C, the rate of relation by about:-


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Read the following passage and answer the questions that follow:

The rate of reaction is concerned with decrease in the concentration of reactants or increase in the concentration of products per unit of time. It can be expressed as instantaneous rate at a particular instant of time and average rate over a large interval of time. A number of factors such as temperature, concentration of reactants, catalyst affect the rate of reaction. Mathematical representation of rate of a reaction is given by rate law:

Rate = k[A]x [B]y

x and y indicate how sensitive the rate is to change in concentration of A and B. Sum of x + y gives the overall order of a reaction.
When a sequence of elementary reactions gives us the products, the reaction is called complex reaction. Molecularity and order of an elementary reaction are same. Zero-order reactions are relatively uncommon but they occur under special conditions. All natural and artificial radioactive decay of unstable nuclei takes place by first-order kinetics.

  1. What is the effect of temperature on the rate constant of a reason?    [1]
  2. For a reaction \[\ce{A + B → Product}\], the rate law is given by, Rate = k[A]2 [B]1/2. What is the order of the reaction?    [1]
  3. How order and molecularity are different for complex reactions?    [1]
  4. A first-order reaction has a rate constant 2 × 10–3 s–1. How long will 6 g of this reactant take to reduce to 2 g?    [2]
    OR
    The half-life for radioactive decay of 14C is 6930 years. An archaeological artifact containing wood had only 75% of the 14C found in a living tree. Find the age of the sample.
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A reaction is second order with respect to a reactant. How is the rate of reaction affected if the concentration of the reactant is reduced to half?


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