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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 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.
\[\ce{H2O2_{( aq)} + 3I^-_{( aq)} + 2H^+ -> 2H2O_{(l)} + I^-_3}\] Rate = k[H2O2][I−]
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?
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?
Define the following terms:
Half-life period of reaction (t1/2).
Rate of reaction for the combustion of propane is equal to:
\[\ce{C3H8_{(g)} + 5O2_{(g)} -> 3CO2_{(g)} + 4H2O_{(g)}}\]
What is the order of a reaction which has a rate expression; Rate = `"k"["A"]^(3/2)["B"]^1`?
Consider a first order gas phase decomposition reaction given below :
\[\ce{A(g) -> B(g) + C(g)}\]
The initial pressure of the system before decomposition of A was pi. After lapse of time ‘t’, total pressure of the system increased by x units and became ‘pt’ The rate constant k for the reaction is given as ______.
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 |
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.
Why is the probability of reaction with molecularity higher than three very rare?
Why does the rate of any reaction generally decreases during the course of the reaction?
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.
Assertion: The enthalpy of reaction remains constant in the presence of a catalyst.
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.
Use Molecular Orbital theory to determine the bond order in each of species, [He2j+ and [He2]2+?
In the presence of a catalyst, the heat evolved or absorbed during the reaction.
For a first order A → B, the reaction rate at reactant concentration of 0.01 m is found to be 2.0 × 10–5. The half-life period 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:-
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?
A flask contains a mixture of compounds A and B. Both compounds decompose by first-order kinetics. The half-lives for A and B are 300 s and 180 s, respectively. If the concentrations of A and B are equal initially, the time required for the concentration of A to be four times that of B (in s) is ______. (Use ln 2 = 0.693)
