Tamil Nadu Board of Secondary EducationHSC Science Class 12

Tamil Nadu Board Samacheer Kalvi solutions for Class 12th Chemistry Volume 1 and 2 Answers Guide chapter 7 - Chemical Kinetics [Latest edition]

Solutions for Chapter 7: Chemical Kinetics

Below listed, you can find solutions for Chapter 7 of Tamil Nadu Board of Secondary Education Tamil Nadu Board Samacheer Kalvi for Class 12th Chemistry Volume 1 and 2 Answers Guide.

Evaluation
Evaluation [Pages 226 - 231]

Tamil Nadu Board Samacheer Kalvi solutions for Class 12th Chemistry Volume 1 and 2 Answers Guide Chapter 7 Chemical Kinetics Evaluation [Pages 226 - 231]

Evaluation | Q 1. | Page 226

For a first-order reaction $\ce{A -> B}$ the rate constant is x min−1. If the initial concentration of A is 0.01 M, the concentration of A after one hour is given by the expression.

• 0.01 e−x

• 1 × 10−2 (1 − e−60x)

• (1 × 10−2) e−60x

• none of these

Evaluation | Q 2. | Page 226

A zero-order reaction $\ce{X -> Product}$, with an initial concentration 0.02 M has a half-life of 10 min. if one starts with concentration 0.04 M, then the half-life is

• 10 s

• 5 min

• 20 min

• cannot be predicted using the given information

Evaluation | Q 3. | Page 226

Among the following graphs showing the variation of rate constant with temperature (T) for a reaction, the one that exhibits Arrhenius behavior over the entire temperature range is

• Both

and

Evaluation | Q 4. | Page 226

For a first order reaction $\ce{A ->Product}$ with initial concentration x mol L−1, has a half life period of 2.5 hours. For the same reaction with initial concentration ("x"/2) mol L−1 the half life is

• (2.5 × 2) hours

• (2.5/2) hours

• 2.5 hours

• Without knowing the rate constant, t1/2 cannot be determined from the given data

Evaluation | Q 5. | Page 227

For the reaction, $\ce{2NH3 -> N2 + 3H2}$, if (-"d" ["NH"_3])/"dt" = k1 [NH3], ("d" ["N"_2])/"dt" = k2 [NH3], ("d" ["H"_2])/"dt" = k3 [NH3] then the relation between k1, k2 and k3 is

• k1 = k2 = k3

• k1 = 3 k2 = 2 k3

• 1.5 k1 = 3 k2 = k3

• 2 k1 = k2 = 3 k3

Evaluation | Q 6. | Page 227

The decomposition of phosphine (PH3) on tungsten at low pressure is a first-order reaction. It is because the

• rate is proportional to the surface coverage

• rate is inversely proportional to the surface coverage

• rate is independent of the surface coverage

• rate of decomposition is slow

Evaluation | Q 7. | Page 227

For a reaction Rate = "k" ["acetone"]^(3/2) then unit of rate constant and rate of reaction respectively is

• ("mol L"^-1 "s"^-1), ("mol"^((-1)/2) "L"^(1/2) "s"^-1)

• ("mol"^((-1)/2) "L"^(1/2) "s"^-1), ("mol L"^-1 "s"^-1)

• ("mol"^(1/2) "L"^(1/2) "s"^-1), ("mol L"^-1 "s"^-1)

• ("mol L s"^-1), ("mol"^(1/2) "L"^(1/2) "s")

Evaluation | Q 8. | Page 227

The addition of a catalyst during a chemical reaction alters which of the following quantities?

• Enthalpy

• Activation energy

• Entropy

• Internal energy

Evaluation | Q 9. | Page 227

Consider the following statements:

(i) increase in concentration of the reactant increases the rate of a zero-order reaction.

(ii) rate constant k is equal to collision frequency A if Ea = 0

(iii) rate constant k is equal to collision frequency A if Ea = ∞

(iv) a plot of ln (k) vs T is a straight line.

(v) a plot of ln (k) vs (1/"T") is a straight line with a positive slope.

Correct statements are

• (ii) only

• (ii) and (iv)

• (ii) and (v)

• (i), (ii) and (v)

Evaluation | Q 10. | Page 227

In a reversible reaction, the enthalpy change and the activation energy in the forward direction are respectively −x kJ mol−1 and y kJ mol−1. Therefore , the energy of activation in the backward direction is

• (y − x) kJ mol−1

• (x + y) J mol−1

• (x − y) kJ mol−1

• (x + y) × 103 J mol−1

Evaluation | Q 11. | Page 228

What is the activation energy for a reaction if its rate doubles when the temperature is raised from 200 K to 400 K? (R = 8.314 JK−1mol−1)

• 234.65 kJ mol1

• 434.65 kJ mol−1

• 2.305 kJ mol1

• 334.65 J mol1

Evaluation | Q 12. | Page 228

This reaction follows first-order kinetics. The rate constant at particular temperature is 2.303 × 10−2 hour−1. The initial concentration of cyclopropane is 0.25 M. What will be the concentration of cyclopropane after 1806 minutes? (log 2 = 0.3010)

• 0.125 M

• 0.215 M

• 0.25 × 2.303 M

• 0.05 M

Evaluation | Q 13. | Page 228

For a first-order reaction, the rate constant is 6.909 min−1 the time taken for 75% conversion in minutes is

• (3/2) log 2

• (2/3) log 2

• (3/2) log (3/4)

• (2/3) log (4/3)

Evaluation | Q 14. | Page 228

In a first order reaction $\ce{x -> y}$; if k is the rate constant and the initial concentration of the reactant x is 0.1 M, then, the half life is

• ((log 2)/"k")

• (0.693/((0.1) "k"))

• ((ln 2)/"k")

• none of these

Evaluation | Q 15. | Page 228

Predict the rate law of the following reaction based on the data given below.

$\ce{2A + B -> C + 3D}$

 Reaction number [A](min) [B](min) Initial rate(M s−1) 1 0.1 0.1 x 2 0.2 0.1 2x 3 0.1 0.2 4x 4 0.2 0.2 8x
• rate = k [A]2 [B]

• rate = k [A] [B]2

• rate = k [A] [B]

• rate = "k" ["A"]^(1/2) ["B"]^(3/2)

Evaluation | Q 16. | Page 228

Assertion: rate of reaction doubles when the concentration of the reactant is doubles if it is a first-order reaction.

Reason: rate constant also doubles.

• Both assertion and reason are true and reason is the correct explanation of assertion.

• Both assertion and reason are true but reason is not the correct explanation of assertion.

• Assertion is true but reason is false.

• Both assertion and reason are false.

Evaluation | Q 17. | Page 228

The rate constant of a reaction is 5.8 × 10−2 s−1. The order of the reaction is ____________.

• First order

• Zero order

• Second order

• Third order

Evaluation | Q 18. | Page 228

For the reaction $\ce{N2O5_{(g)} -> 2NO2_{(g)} + 1/2O2_{(g)}}$, the value of rate of disappearance of N2O5 is given as 6.5 × 10−2 mol L−1s−1. The rate of formation of NO2 and O2 is given respectively as

• (3.25 × 102 mol L-1s1) and (1.3 × 102 mol L1s1)

• (1.3 × 102 mol L1s1) and (3.25 × 102 mol L1s1)

• (1.3 × 101 mol L1s1) and (3.25 × 102 mol L1s1)

• None of these

Evaluation | Q 19. | Page 229

During the decomposition of H2O2 to give dioxygen, 48 g O2 is formed per minute at certain point of time. The rate of formation of water at this point is

• 0.75 mol min−1

• 1.5 mol min−1

• 2.25 mol min−1

• 3.0 mol min−1

Evaluation | Q 20. | Page 229

If the initial concentration of the reactant is doubled, the time for half reaction is also doubled. Then the order of the reaction is ____________.

• Zero

• One

• Fraction

• None

Evaluation | Q 21. | Page 229

In a homogeneous reaction $\ce{A -> B + C + D}$, the initial pressure was P0 and after time t it was P. Expression for rate constant in terms of P0, P and t will be

• "k" = (2.303/"t") log ((2"P"_0)/(3"P"_0 - "P"))

• "k" = (2.303/"t") log ((2"P"_0)/("P"_0 - "P"))

• "k" = (2.303/"t") log ((3"P"_0 - "P")/(2"P"_0))

• "k" = (2.303/"t") log ((2"P"_0)/(3"P"_0 - 2"P"))

Evaluation | Q 22. | Page 229

If 75% of a first order reaction was completed in 60 minutes, 50% of the same reaction under the same conditions would be completed in ____________.

• 20 minutes

• 30 minutes

• 35 minutes

• 75 minutes

Evaluation | Q 23. | Page 229

The half life period of a radioactive element is 140 days. After 560 days, 1 g of element will be reduced to

• (1/2) "g"

• (1/4) "g"

• (1/8) "g"

• (1/16) "g"

Evaluation | Q 24. | Page 229

The correct difference between first and second order reactions is that

• A first order reaction can be catalysed; a second order reaction cannot be catalysed.

• The half life of a first order reaction does not depend on [A0]; the half life of a second order reaction does depend on [A0].

• The rate of a first order reaction does not depend on reactant concentrations; the rate of a second order reaction does depend on reactant concentrations.

• The rate of a first order reaction does depend on reactant concentrations; the rate of a second order reaction does not depend on reactant concentrations.

Evaluation | Q 25. | Page 229

After 2 hours, a radioactive substance becomes (1/16)^"th" of original amount. Then the half life ( in min) is

• 60 minutes

• 120 minutes

• 30 minutes

• 15 minutes

Evaluation | Q 1. | Page 230

Define average rate.

Evaluation | Q 1. | Page 230

Define instantaneous rate.

Evaluation | Q 2. | Page 230

Define rate law.

Evaluation | Q 2. | Page 230

Define rate constant.

Evaluation | Q 3. | Page 230

Derive integrated rate law for a zero-order reaction $\ce{A -> Product}$.

Evaluation | Q 4. | Page 230

Define half life of a reaction.

Evaluation | Q 4. | Page 230

Show that for a first order reaction half life is independent of initial concentration.

Evaluation | Q 5. | Page 230

What is an elementary reaction?

Evaluation | Q 5. | Page 230

Give the differences between order and molecularity of a reaction.

Evaluation | Q 6. | Page 230

Explain the rate determining step with an example.

Evaluation | Q 7. | Page 230

Describe the graphical representation of first order reaction.

Evaluation | Q 8. (a) | Page 230

Write the rate law for the following reaction.

A reaction that is 3/2 order in x and zero order in y.

Evaluation | Q 8. (b) | Page 230

Write the rate law for the following reaction.

A reaction that is second order in NO and first order in Br2.

Evaluation | Q 9. | Page 230

Explain the effect of catalyst on reaction rate with an example.

Evaluation | Q 10. | Page 230

The rate law for a reaction of A, B and C has been found to be rate = "k" ["A"]^2["B"] ["L"]^(3/2). How would the rate of reaction change when

1. Concentration of [L] is quadrupled
2. Concentration of both [A] and [B] are doubled
3. Concentration of [A] is halved
4. Concentration of [A] is reduced to (1/3) and concentration of [L] is quadrupled.
Evaluation | Q 11. | Page 230

The rate of formation of a dimer in a second order reaction is 7.5 × 10−3 mol L−1s−1 at 0.05 mol L−1 monomer concentration. Calculate the rate constant.

Evaluation | Q 12. | Page 230

For a reaction $\ce{x + y + z -> products}$ the rate law is given by rate = "k" ["x"]^(3/2) ["y"]^(1/2) what is the overall order of the reaction and what is the order of the reaction with respect to z.

Evaluation | Q 13. | Page 230

Explain briefly the collision theory of bimolecular reactions.

Evaluation | Q 14. | Page 230

Write Arrhenius equation and explains the terms involved.

Evaluation | Q 15. | Page 230

The decomposition of Cl2O7 at 500 K in the gas phase to Cl2 and O2 is a first order reaction. After 1 minute at 500 K, the pressure of Cl2O7 falls from 0.08 to 0.04 atm. Calculate the rate constant in s−1.

Evaluation | Q 16. | Page 230

Give two examples for zero order reaction.

Evaluation | Q 17. | Page 230

Explain pseudo-first-order reaction with an example.

Evaluation | Q 18. (i) | Page 230

Identify the order for the following reaction.

Rusting of Iron

Evaluation | Q 18. (ii) | Page 230

Identify the order for the following reaction.

Evaluation | Q 18. (iii) | Page 230

Identify the order for the following reaction.

$\ce{2A + 3B -> products}$; rate = "k" ["A"]^(1/2) ["B"]^2

Evaluation | Q 19. | Page 230

A gas phase reaction has energy of activation 200 kJ mol−1. If the frequency factor of the reaction is 1.6 × 1013 s−1. Calculate the rate constant at 600 K. ("e"^-40.09 = 3.8 xx 10^-18)

Evaluation | Q 20. | Page 231

For the reaction $\ce{2x + y -> L}$ find the rate law from the following data.

 [x](M) [y](M) rate(M s−1) 0.2 0.02 0.15 0.4 0.02 0.30 0.4 0.08 1.20
Evaluation | Q 21. | Page 231

How do concentrations of the reactant influence the rate of reaction?

Evaluation | Q 22. | Page 231

How do nature of the reactant influence rate of reaction?

Evaluation | Q 23. | Page 231

The rate constant for a first order reaction is 1.54 × 10−3 s−1. Calculate its half life time.

Evaluation | Q 24. | Page 231

The half life of the homogeneous gaseous reaction $\ce{SO2Cl2 -> SO2 + Cl2}$ which obeys first order kinetics is 8.0 minutes. How long will it take for the concentration of SO2Cl2 to be reduced to 1% of the initial value?

Evaluation | Q 25. | Page 231

The time for half change in a first order decomposition of a substance A is 60 seconds. Calculate the rate constant. How much of A will be left after 180 seconds?

Evaluation | Q 26. | Page 231

A zero order reaction is 20% complete in 20 minutes. Calculate the value of the rate constant. In what time will the reaction be 80% complete?

Evaluation | Q 27. | Page 231

The activation energy of a reaction is 22.5 k Cal mol−1 and the value of rate constant at 40°C is 1.8 × 10−5 s−1. Calculate the frequency factor, A.

Evaluation | Q 28. | Page 231

Benzene diazonium chloride in aqueous solution decomposes according to the equation $\ce{C6H5N2Cl -> C6H5Cl + N2}$. Starting with an initial concentration of 10 g L−1, the volume of N2 gas obtained at 50°C at different intervals of time was found to be as under:

 t (min): 6 12 18 24 30 ∞ Vol. of N2(ml) 19.3 32.6 41.3 46.5 50.4 58.3

Show that the above reaction follows the first order kinetics. What is the value of the rate constant?

Evaluation | Q 29. | Page 231

From the following data, show that the decomposition of hydrogen peroxide is a reaction of the first order:

 t (min) 0 10 20 V (ml) 46.1 29.8 19.3

Where t is the time in minutes and V is the volume of standard KMnO4 solution required for titrating the same volume of the reaction mixture.

Evaluation | Q 30. | Page 231

A first order reaction is 40% complete in 50 minutes. Calculate the value of the rate constant. In what time will the reaction be 80% complete?

Evaluation

Tamil Nadu Board Samacheer Kalvi solutions for Class 12th Chemistry Volume 1 and 2 Answers Guide chapter 7 - Chemical Kinetics

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Concepts covered in Class 12th Chemistry Volume 1 and 2 Answers Guide chapter 7 Chemical Kinetics are Integrated Rate Equations, First Order Reactions, Zero Order Reactions, Rate of a Chemical Reaction, Molecularity, Collision Theory, Arrhenius Equation – the Effect of Temperature on Reaction Rate, Factors Affecting the Reaction Rate, Pseudo First Order Reaction, Half Life Period of a Reaction.

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