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प्रश्न
Why can we not determine the order of a reaction by taking into consideration the balanced chemical equation?
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उत्तर
Balanced chemical equation often leads to incorrect order or rate law. For example the following reaction seems to be a tenth order reaction.
\[\ce{KClO3 + 6FeSO4 + 3H2SO4 -> KCl + 3H2O + 3Fe2 (SO4)3}\]
This is actually a second order reaction. Actually the reaction is complex and occurs in several steps. The order of such reaction is determined by the slowest step in the reaction mechanism. Order is determined experimentally and is confined to the dependence of observed rate of reaction on the concentration of reactants.
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संबंधित प्रश्न
For a reaction A + B ⟶ P, the rate is given by
Rate = k [A] [B]2
What is the overall order of reaction if A is present in large excess?
For a chemical reaction R → P, the variation in the concentration (R) vs. time (t) plot is given as:
(i) Predict the order of the reaction.
(ii) What is the slope of the curve?
(iii) Write the unit of rate constant for this reaction.
From the rate expression for the following reaction, determine the order of reaction and the dimension of the rate constant.
\[\ce{C2H5Cl_{(g)} -> C2H4_{(g)} + HCl_{(g)}}\] Rate = k [C2H5Cl]
A reaction is second order with respect to a reactant. How is the rate of reaction affected if the concentration of the reactant is doubled?
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?
Write the principle behind the following methods of refining:
Hydraulic washing
Define the following term:
Pseudo first-order reaction
What is the order of a reaction which has a rate expression; Rate = `"k"["A"]^(3/2)["B"]^1`?
The value of rate constant of a pseudo first order reaction ______.
For a complex reaction:
(i) order of overall reaction is same as molecularity of the slowest step.
(ii) order of overall reaction is less than the molecularity of the slowest step.
(iii) order of overall reaction is greater than molecularity of the slowest step.
(iv) molecularity of the slowest step is never zero or non interger.
In a reaction if the concentration of reactant A is tripled, the rate of reaction becomes twenty seven times. What is the order of the reaction?
Why does the rate of any reaction generally decreases during the course of the reaction?
Match the graph given in Column I with the order of reaction given in Column II. More than one item in Column I may link to the same item of Column II.
| Column I | Column II | |
| (i) |  |
|
| (ii) |  |
(a) 1st order |
| (iii) |  |
(b) Zero-order |
| (iv) |  |
Assertion: Rate constants determined from Arrhenius equation are fairly accurate for simple as well as complex molecules.
Reason: Reactant molecules undergo chemical change irrespective of their orientation during collision.
Use Molecular Orbital theory to determine the bond order in each of species, [He2j+ and [He2]2+?
For a reaction 1/2 A ⇒ 2B, rate of disappearance of A is related 't o the appearance of B by the expression:
The number of molecules of the reactants taking part in a single step of the reaction is indicative of ______.
For the reaction, \[\ce{A +2B → AB2}\], the order w.r.t. reactant A is 2 and w.r.t. reactant B. What will be change in rate of reaction if the concentration of A is doubled and B is halved?
Higher yield of NO in \[\ce{N2(g) + O2 <=> 2NO(g)}\] can be obtained at:
[ΔH of the reaction = +180.7 kJ mol−1]
- higher temperature
- lower temperature
- higher concentration of N2
- higher concentration of O2
Choose the correct answer from the options given below:
