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प्रश्न
Why molecularity is applicable only for elementary reactions and order is applicable for elementary as well as complex reactions?
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उत्तर
A complex reaction proceeds through several elementary reactions. Numbers of molecules involved in each elementary reaction may be different i.e., the molecularity of each step may be different. Therefore, discussion of molecularity of overall complex reaction is meaningless. On the other hand, order of a complex reaction is determined by the slowest step in its mechanism and is not meaningless even in the case of complex reactions.
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संबंधित प्रश्न
Define “zero order reaction”.
In a first order reaction x → y, 40% of the given sample of compound remains unreacted in 45 minutes. Calculate rate constant of the reaction.
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?
For the first order thermal decomposition reaction, the following data were obtained:
Time / sec Totalpressure / atm
0 0.30
300 0.50
Calculate the rate constant
(Given: log 2 = 0.301, log3 = 0.4771, log 4 = 0.6021)
For a reaction : 
(i) Write the order and molecularity of this reaction.
(ii) Write the unit of k.
For the hydrolysis of methyl acetate in aqueous solution, the following results were obtained :
| t/s | 0 | 30 | 60 |
| [CH3COOCH3] / mol L–1 | 0.60 | 0.30 | 0.15 |
(i) Show that it follows pseudo first order reaction, as the concentration of water remains constant.
(ii) Calculate the average rate of reaction between the time interval 30 to 60 seconds.
(Given log 2 = 0.3010, log 4 = 0.6021)
A reaction is first order in A and second order in B. How is the rate affected on increasing the concentration of B three times?
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?
How does calcination differ from roasting?
Define the following terms:
Half-life period of reaction (t1/2).
Which of the following statement is true for order of a reaction?
Compounds ‘A’ and ‘B’ react according to the following chemical equation.
\[\ce{A(g) + 2B(g) -> 2C(g)}\]
Concentration of either ‘A’ or ‘B’ were changed keeping the concentrations of one of the reactants constant and rates were measured as a function of initial concentration. Following results were obtained. Choose the correct option for the rate equations for this reaction.
| Experiment | Initial concentration of [A]/mol L–¹ |
Initial concentration of [B]/mol L–¹ |
Initial rate of formation of [C]/mol L–¹ s–¹ |
| 1. | 0.30 | 0.30 | 0.10 |
| 2. | 0.30 | 0.60 | 0.40 |
| 3. | 0.60 | 0.30 | 0.20 |
Consider the reaction A ⇌ B. The concentration of both the reactants and the products varies exponentially with time. Which of the following figures correctly describes the change in concentration of reactants and products with time?
For a reaction A + B → products, the rate law is given by: r = `K[A]^(1/2)`. What is the order of reaction?
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:-
For a reaction 1/2 A ⇒ 2B, rate of disappearance of A is related 't o the appearance of B by the expression:
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. |
- What is the effect of temperature on the rate constant of a reason? [1]
- 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]
- How order and molecularity are different for complex reactions? [1]
- 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.
[log 4 = 0.6021, log 3 = 0.4771, log 2 = 0.3010, log 10 = 1] [2]
