Advertisements
Advertisements
Question
Mention the factors that affect the rate of a chemical reaction.
Advertisements
Solution
(i) Nature of the reactant: The rate of reaction depends on the nature of the reactant. For example, ionic molecules react more quickly than covalent ones.
(ii) State of reactants: Solid reactions are slower, liquid reactions are faster, and gas reactions are very quick.
(iii) Temperature: The rate of reaction is mainly affected by temperature. Every 10°C rise in temperature increases the reaction rate by 2-3 times.
`(r_(t + 10))/r_t` = 2 − 3
This ratio is called the temperature coefficient.
There are two reasons why the reaction rate increases with temperature.
- Increasing temperature raises the average kinetic energy of reactant molecules, increasing the rate of collisions.
- As the temperature rises, the number of molecules with threshold energy increases, resulting in more active molecules. As a result, the number of effective collisions grows. As a result, the reaction rate increases.
(iv) Concentration: The rate of reaction depends on the concentration of reactants.
Rate = k × Cn
Where,
n = order of reaction
C = concentration of reactant
(v) Catalyst: The presence of a catalyst changes the rate of the reaction. It lowers the activation energy by producing a chemical intermediate, lowering the potential energy barrier. Thus, the reaction rate increases.
APPEARS IN
RELATED QUESTIONS
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 → B is a first order reaction with rate 6.6 × 10-5m-s-1. When [A] is 0.6m, rate constant of the reaction is
- 1.1 × 10-5s-1
- 1.1 × 10-4s-1
- 9 × 10-5s-1
- 9 × 10-4s-1
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 conversion of molecules X to Y follows second order kinetics. If concentration of X is increased to three times how will it affect the rate of formation of Y?
From the rate expression for the following reaction, determine the order of reaction and the dimension of the rate constant.
\[\ce{CH3CHO_{(g)} -> CH4_{(g)} + CO_{(g)}}\] Rate = k[CH3CHO]3/2
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.
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?
How does calcination differ from roasting?
Define the following term:
Pseudo first-order 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 |
The value of rate constant of a pseudo first order reaction ______.
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+?
In the presence of a catalyst, the heat evolved or absorbed during the reaction.
For a reaction R → p the concentration of reactant change from 0.03 m to 0.02 m in minute, calculate the average rate of the reaction using the unit of second.
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
The number of molecules of the reactants taking part in a single step of the reaction is indicative of ______.
On heating compound (A) gives a gas (B) which is constituent of air. The gas when treated with H2 in the presence of catalyst gives another gas (C) which is basic in nature, (A) should not be ______.
