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Right ANSWER is (a) True

The explanation: The rate constant is defined as the proportionality constant which explains the RELATIONSHIP between the molar CONCENTRATION of the reactants and the rate of a chemical REACTION. It is denoted by K.

For a first-order reaction, the unit of k is s^-1.

The correct ANSWER is (c) 0.015 s^-1

Easiest explanation: Given,

[A] = 0.75 M, k= 0.02

The reaction BELONGS to pseudo FIRST order reaction so, the UNIT is s^-1

R= k [A]= 0.02 × 0.75= 0.015 s^-1.

The CORRECT choice is (a) True

To explain: For the collisions to be EFFECTIVE, molecules MUST collide with sufficient energy, known as activation energy so that CHEMICAL BONDS can break. This causes the reaction to occur faster and to form the required products.

Correct OPTION is (B) 207.9s^-1

For explanation I would say: Given,

K = 0.01s^-1

t1/2 = 0.693/0.01

t1/2 = 69.3s

[R] = [R]0/2^n

2^n = [R]0/[R]

2^n = 2.4/0.3

2^n = 8

n = 3 (NUMBER of half-lives)

For 1 half-life t1/2 = 69.3s

For 3 half-life 3t1/2 = 3 x 69.3s = 207.9s.

Correct option is (B) R=k [CH3COOC2H5]

The explanation: The reaction involved in acid hydrolysis of ester = CH3COOC2H5 + H2O → CH3COOH + C2H5OH. So the rate law becomes R=k’ [CH3COOC2H5][H2O], SINCE water is present in LARGE excess it is assumed to be constant throughout the reaction.

R=k[CH3COOC2H5], where k is k’ [H2O].

Right choice is (d) 2 × t50

For EXPLANATION I WOULD SAY: Given, the reaction is 75 percent complete so, a = 75

We know, t = \(\frac{2.303}{k}\)log\(\frac{100}{100-a}\)

T75 = \(\frac{2.303}{k}\)log\(\frac{100}{100-75}\) = \(\frac{1.386}{k}\)

t50 = \(\frac{2.303}{k}\)log\(\frac{100}{100-50}\) = \(\frac{0.693}{k}\)

t75 = 2 × t50.

Correct choice is (c) Surface area of the reactants

To explain I would say: Automobile engines cannot CHANGE the CONCENTRATION, viscosity or the nature of the FUEL. In the engines, fuel is injected in the FORM of microscopic droplets so that it has a larger surface area than when fed into the engine as a stream. This allows the fuel to burn RAPIDLY.

The correct choice is (C) Addition of catalyst

For explanation: The presence of a catalyst in a REACTION LOWERS the activation ENERGY barrier and hence the reaction BECOMES faster. Hence, the addition of catalysts helps to increase the rate of a reaction.

Correct option is (B) 17.143 M

Best explanation: GIVEN, R=0.6 s^-1 and K= 0.035

For a first ORDER reaction R= k [A]

[A]=\(\frac{R}{k}\) = \(\frac{0.6}{0.035}\) = 17.143 M.

Correct answer is (c) HARD SPHERES

The best explanation: In Collision theory, activation energy and proper ORIENTATION of molecules together DETERMINE the criteria for an effective collision but it has a certain drawback as it considers atoms/molecules to be hard spheres and ignores their SPHERICAL aspects.

The correct OPTION is (C) E^-Ea/RT

Easiest explanation: The factor e^-Ea/RT in the Arrhenius equation is called Boltzmann factor. It represents the fraction of the molecules (NE/NT) having ENERGY equal to or greater than E where NE represents the number of molecules with energy E and NT represents the total number of molecules.

Right answer is (a) Trautz and Lewis

Easiest EXPLANATION: In 1916, Max Trautz and William Lewis PUT forward the collision theory giving a better explanation about the rates of reactions. According to this theory, it is assumed that the REACTANT molecules are hard spheres and reaction between them occurs only when they COLLIDE with each other.

Right ANSWER is (b) Shifts forward and DOWNWARD

To EXPLAIN I would say: With the increase of temperature, the peak shifts forward but downward. This is because with the increase of temperature, the most PROBABLE kinetic energy increases and the FRACTION of molecules possessing most probable kinetic energy decreases.

The CORRECT option is (a) True

Easiest EXPLANATION: The increase in the rate of REACTION with a RISE in TEMPERATURE is not due to the increase in the total number of collisions but mainly due to an increase in the total number of effective collisions.

The correct option is (a) n = Rate CONSTANT at T + 10°/Rate constant at T°

Easiest explanation: The effect of temperature on the rate of a reaction is usually EXPRESSED in terms of the temperature coefficient which is defined by the EQUATION:

Temperature coefficient (n) = Rate constant at T + 10° (308 K)/Rate constant at T° (298 K).

Right choice is (c) Gas

Best explanation: When TWO reactants are in the same phase, it is better for the speed if the REACTION if they are in a gaseous phase as the particles are free to move and can collide more frequently with each other, RESULTING in a CHEMICAL reaction.

The correct choice is (B) False

Easy explanation: The reaction for the inversion of cane sugar is C12H22O11 + H2O → glucose + fructose.

In this reaction WATER is present in excess and belongs to a pseudo first order reaction, even THOUGH the molecularity is 2 the order of the reaction is 1 so the rate law R=k[C12H22O11].

Correct option is (a) 4.74 × 10^-2 (L/MOL)^1/2 s^-1

The BEST I can EXPLAIN: Given, [A] = 0.5 M, [B] = 0.1 M and k= 0.03

From the RATE law it is evident that the order of the reaction is 1+ 0.5 = 1.5 = \(\frac{3}{2}\)

Therefore the unit of k= (mol L^-1)^1-1.5 s^-1 = (L/mol)^1/2 s^-1

R= k[A]^1[B]^1/2 = 0.03 × 0.5 × 0.1^1/2 = 4.74 × 10^-2(L/mol)^1/2 s^-1.

The correct choice is (C) 7596.45 s^-1

Explanation: Given,

EA = 50 kJ mol^-1

T = 300 K

k = 1.5 × 10^-5 sec^-1

R = 8.314 J K^-1 mol^-1

log k = – Ea / (2.303 RT) + log A

OR

log A = log k + Ea / (2.303 RT)

log A = log (1.5 × 10^-5) + 50000 / (2.303 × 8.314 × 300)

log A = 3.88061

A = antilog (3.880611)

A = 7596.45 s^-1.

Right answer is (a) R = 8.314 J K^-1 mol^-1

The explanation is: Saline medium has extra salts such as SODIUM CHLORIDE dissolved in water. It has a GREATER CONCENTRATION of electrolyte than ordinary medium. The ions present will favour the formation of more electrochemical CELLS and favour the transfer of hydrogen ions and will thus promote rusting or corrosion.

Right option is (a) s^-1

The explanation is: The UNIT of the RATE of the reaction (K) is (mol L^-1)^1-N s^-1, where n is the order of the reaction.

For a pseudo first-order reaction n=1.

So, (mol L^-1)^1-n s^-1 = (mol L^-1)^1-1 s^-1 = s^-1.

Right choice is (C) mol^-1 L s^-1

To ELABORATE: The UNIT of the rate of the reaction (K) is (mol L^-1) ^1-N s^-1, where n is the order of the reaction.

For a second-order reaction, n=2

(mol L^-1) ^1-n s^-1 = (mol L^-1)^1-2 s^-1 = mol^-1 L s^-1.

The correct choice is (B) 8.124 kJ mol^-1

Easiest EXPLANATION: Given,

K1=6 × 10^-3s^-1T1=50 + 273=323 K

k2=9 × 10^-3s^-1T2=100 + 273=373 K

Substituting these values in the equation:

log (k2 / k1 ) = (EA / 2.303 R) × ((T2 – T1) / T1 T2), we get

log (9 × 10^-3s^-1 / 6 × 10^-3 s^-1) = ((Ea / (2.303 × 8.314)) × ((373 – 323) / (373 × 323))

log 9 / 6 = ((Ea / (2.303 × 8.314)) × (50 / (373 × 323))

Ea = 8.124 kJ mol^-1.

The CORRECT option is (c) 90 minutes

Explanation: Reaction is 50 PERCENT complete in 30 minutes. Hence, t1/2 = 30 minutes

75 percent of the reaction is completed in two half-lives. Hence, t = 2 × 30 = 60 minutes

87.5 percent of the reaction is completed in three half-lives. Hence, t = 3 × 30 = 90 minutes.

Correct OPTION is (c) Law of mass action

For explanation I would say: The law of mass action is the proposition which STATES that the rate of a CHEMICAL reaction is directly proportional to the concentrations of the REACTANTS. On the other hand, the other laws mentioned in the options are UNRELATED to the rate of a reaction.

The CORRECT option is (d) 7.75 x 10^-4

The BEST I can explain: GIVEN,

 N2O5 → 2N02 + 1/2 O2

Rate = k[N2O5] ^1

Rate =6.25 x 10^-4 x [1.25]

Rate = 7.75 x 10^-4.

The CORRECT ANSWER is (a) R= [C2H4] [I2]^3/2

The best explanation: Fractional ORDER reactions are reaction WHOSE order is a fraction. This reaction is an example of fractional order reaction, where the order of the reaction is \(\frac{5}{2}\).

The rate law for the reaction is known to be R= [C2H4] [I2]^3/2.

Right answer is (a) 6 × 10^2s^-1

The BEST explanation: GIVEN,

Ea = 49 kJ / mol^-1

T = 313 K

A = 9 × 10^2 s^-1

R = 8.314 J K^-1 mol^-1

log k = – Ea / (2.303 RT) + log A

log k = – 49000 / (2.303 × 8.314 × 313) + log 9 × 10^10

log k = 2.77843

k= antilog (2.77843)

k = 6 × 10^2 s^-1.

The correct CHOICE is (B) Molecularity of the REACTION should be one

To EXPLAIN: The order of the reaction can be sometimes altered by taking one of the REACTANT in excess compared to the other. Pseudo first order reactions are those reactions in which the molecularity is more than one but follows first order kinetics.

The CORRECT answer is (a) True

Best explanation: For most of the reactions, the rate of REACTION becomes nearly double or even more for 10° RISE of TEMPERATURE. The effect of temperature is usually expressed in terms of temperature COEFFICIENT.

Right ANSWER is (c) 4.07 x 10^-4

Easy EXPLANATION: Given,

Arrhenius factor(A) = 4 x 10^13 collisions/sec

Activation energy (Ea)=98.6KJ/mol=98.6 x 10^3J/mol, T=303 K

log K = log A – (Ea/2.303RT)

log K = log (4 x 10^13) – (98.6 x 10^3)/(2.303 x 8.314 x 303)

log K = 13.6020 – (98.6 x 10^3/5801.584)

log k = -3.39

K = 10^-3.39

K = 4.07 x 10^-4.

Correct choice is (a) 38.4s

To EXPLAIN: GIVEN,

K=7.5 X 10^-3 s^-1

K = (2.303/t) x log([R]0/[R])

t = (2.303/7.5 x 10^-3) x log([100]/[25])

t = (2.303/7.5 x 10^-3) x 0.6

t = 38.4s.

The CORRECT choice is (d) r2= 4r1

Easiest explanation: Since it is an elementary reaction, its RATE law R1= k [A] ^3[B]

When the concentrations are CHANGED the new rate will be r2= k (2[A])^3([B]/2) = 4k[A]^3[B]

So, r2=4r1.

Correct option is (a) True

The explanation: PROPER orientation of reactant molecules LEADS to bond formation because improper orientation makes the reactant molecules bounce BACK and HENCE the reaction won’t take place and the required PRODUCTS will not to be formed.

Right ANSWER is (d) k = A e^-Ea/RT

Best explanation: Quantitatively, the effect of temperature on the rate of a reaction and hence on the rate constant k, was PROPOSED by ARRHENIUS in 1889. The EQUATION, called Arrhenius equation, is usually WRITTEN in the form k = A e^-Ea/RT.

Correct option is (B) 0.06 min^-1

The best EXPLANATION: Given, the reaction is 70 percent complete so, a = 70

Time t = 20 minutes

First order integrated rate equation, k = \(\frac{2.303}{t}\)LOG\(\frac{100}{100-a}\)

k= \(\frac{2.303}{20}\)log\(\frac{100}{100-70}\) = 0.06 min^-1.

Right ANSWER is (a) 60.28 minutes

The BEST I can explain: GIVEN, the reaction is 75 complete so, a=75

Rate of the reaction k=0.023 min^-1

First-order integrated rate equation, k = \(\FRAC{2.303}{t}\)LOG\(\frac{100}{100-a}\)

t=\(\frac{2.303}{0.023}\)log\(\frac{100}{100-75}\) = 60.28 minutes.

Right answer is (B) False

To explain I would say: The UNIT of the rate CONSTANT k for a zero-order reaction is mol L^-1 s^-1. For a first-order reaction, the unit of k is s^-1. The unit of the rate constant k for a second-order reaction is mol^-1 L s^-1.

The correct answer is (B) FIRST order

Best explanation: Given,

 k= 3.28 × 10^-4 s^-1

 The general formula to find the UNITS for rate constant, k=(mol L^-1)^1-ns^-1 where n is the order of the reaction. The VALUE of n must be 1 for (mol L^-1)^1-ns^-1 to become s^-1. Therefore, k=3.28 × 10^-4s^-1 represents a first order reaction.

The correct option is (c) It quadruples

To explain I would SAY: Let the initial concentration of reactant = [A]

Given concentration of reactant = 2 x [A]

We KNOW that the rate of a SECOND order reaction = k x [A]^2

Therefore, rate for 2 x [A] = k x 4 x [A]^2

Therefore, the rate quadruples when the concentration of the reactant is doubled in a second order kinetic reaction.

Right option is (a) [A] = [A]0e^-kt

Explanation: A reaction is said to be of the first order if the rate of the reaction DEPENDS upon one CONCENTRATION TERM only. The integrated rate equation for a first order reaction in exponential FORM is [A] = [A]0e^-kt.

Correct answer is (B) False

Explanation: ΔH REFERS to the enthalpy of the REACTION. It TELLS us how much energy was absorbed or released as a result of the reaction. It can only tell us if a reaction is EXOTHERMIC or endothermic and as a result, the rate of a reaction does not depend on it.

The correct answer is (d) MOLECULARITY

To explain: Molecularity of a reaction is the NUMBER of atoms, ions or molecules that MUST collide with one another simultaneously so as to result into that CHEMICAL reaction. It does not affect the RATE of the reaction directly.

Right answer is (a) CH3COOC2H5 + NaOH → CH3COOH + H2O

Explanation: The reactions CH3COOC2H5 + H2O → CH3COOH + C2H5OH, C2H5COOC2H5 + H2O → C2H5COOH + C2H5OH and C12H22O11 + H2O → glucose + fructose are examples of pseudo first order reaction because water is present in excess and is assumed to remain CONSTANT is all the reactions but the reaction CH3COOC2H5 + NaOH → CH3COOH + H2O is an example of second order reaction and follows second order KINETICS with rate law R=k [CH3COOC2H5] [NaOH].