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प्रश्न
How does calcination differ from roasting?
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उत्तर
| Roasting | Calcination |
| Ore is heated in excess of air. | Ore is heated in the absence or limited supply of air. |
| This is used for sulphide ores. | This is used for carbonate ores. |
| SO2 is produced along with metal oxide. | CO2 is produced along with metal oxide. |
| e.g. \[\ce{ 2ZnS + 3O2 ->[\Delta] 2ZnO + 2SO2}\] | e.g. \[\ce{ZnCO3 ->[\Delta] ZnO + CO2}\] |
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संबंधित प्रश्न
Write molecularity of the following reaction:
2NO(g)+O2(g)→2NO2(g)
For a reaction: 
Rate = k
(i) Write the order and molecularity of this reaction.
(ii) Write the unit of k.
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 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)
For a reaction, \[\ce{A + B -> Product}\]; the rate law is given by, `r = k[A]^(1/2)[B]^2`. What is the order of the 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]
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.
Mention the factors that affect the rate of a chemical reaction.
A reaction is first order in A and second order in B. Write the differential rate equation.
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?
Write the principle behind the following methods of refining:
Hydraulic washing
Define the following terms:
Half-life period of reaction (t1/2).
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 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.
For which type of reactions, order and molecularity have the same value?
Why does the rate of any reaction generally decreases during the course of the reaction?
Why can’t molecularity of any reaction be equal to zero?
Why molecularity is applicable only for elementary reactions and order is applicable for elementary as well as complex reactions?
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: Order and molecularity are same.
Reason: Order is determined experimentally and molecularity is the sum of the stoichiometric coefficient of rate determining elementary step.
In the presence of a catalyst, the heat evolved or absorbed during the reaction.
For a reaction A + B → products, the rate law is given by: r = `K[A]^(1/2)`. What is the order of reaction?
If the 0.05 molar solution of m+ is replaced by a 0.0025 molar m+ solution, then the magnitude of the cell potential would be
The half-life period of a. substance in a certain enzyme catalysed reaction is 138 s. The time required for the concentration of the substance to fall from 1.28 mol–1 to 0.04 mg L–1 is
At concentration of 0.1 and 0.2 mol L–1 the rates of deem position of a compound were found to be 0.18 and 0.72 mol L–1 m–1. What is the order of the reaction?
The conversion of molecules A to B follow second order kinetics. If concentration of A is increased to three times, how will it affect the rate of formation of B?
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?
