Chemical Kinetics

01

PYQ 2010

hard

chemistry ID: mht-cet-

The first order integrated rate equation is

1

2

3

4

02

PYQ 2017

medium

chemistry ID: mht-cet-

Which among the following reactions is an example of pseudo first order reaction ?

1

Inversion of cane sugar

2

Decomposition of

3

Conversion of cyclopropane to propene

4

Decomposition of

03

PYQ 2019

medium

chemistry ID: mht-cet-

For a chemical reaction rate law is, rate If is doubled at constant, the rate of reaction

1

increases by a factor of

2

increases by a factor of

3

increases by a factor of

4

increases by a factor of

04

PYQ 2020

medium

chemistry ID: mht-cet-

What is the unit of rate constant for the zero-order reaction?

1

mol dm t

2

mol dm t

3

t

4

mol dm t

05

PYQ 2020

medium

chemistry ID: mht-cet-

The rate constant for first order reaction is 0.02232 min . Calculate the time required for 75% completion of the reaction.

1

62.12 min

2

38.31 min

3

12.77 min

4

48.12 min

06

PYQ 2020

medium

chemistry ID: mht-cet-

The half life of a first order reaction is 6.0 hours. How long will it take for the concentration of reactant to decrease from 0.4 M to 0.12 M?

1

30:36 h

2

10:42 h

3

4:25 h

4

9:51 h

07

PYQ 2020

medium

chemistry ID: mht-cet-

Reaction given below follows first order kinetics. 2N O 4NO + O Calculate rate constant of reaction if concentration of N O is 0.05 M and rate of reaction is mol L s .

1

2

3

4

08

PYQ 2020

medium

chemistry ID: mht-cet-

Which of the following amine is most basic in nature?

1

2,4-Dichloroaniline

2

2,4-Dibromoaniline

3

2,4-Dinitroaniline

4

2,4-Dimethylaniline

09

PYQ 2020

medium

chemistry ID: mht-cet-

Half-life of first order reaction What is the time required to reduce the concentration of X by 90% of its initial concentration?

1

minutes

2

minutes

3

minutes

4

minutes

10

PYQ 2020

medium

chemistry ID: mht-cet-

In the reaction 2 the rate of formation of are in the ratio

1

2

3

4

11

PYQ 2020

medium

chemistry ID: mht-cet-

If,, calculate heat liberated during formation of 0.154 kg of .

1

1386.0 kJ

2

346.5 kJ

3

693.0 kJ

4

1039.5 kJ

12

PYQ 2020

medium

chemistry ID: mht-cet-

What is the number of hydroxyl groups present in lactic acid?

1

Zero

2

Three

3

Two

4

One

13

PYQ 2020

medium

chemistry ID: mht-cet-

What is the temperature needed for decomposition of lime stone in blast furnace for extraction of iron?

1

1500 K

2

2000 K

3

1200 K

4

500 K

14

PYQ 2020

medium

chemistry ID: mht-cet-

Mg N reacts with water to produce

1

Mg(OH) and NH

2

Mg(OH) and N O

3

MgO and NH

4

MgO and NH OH

15

PYQ 2020

medium

chemistry ID: mht-cet-

Which among the following catalysts is used in manufacture of sulphuric acid by contact process?

1

Ni

2

Fe with Mo

3

V O

4

MnO

16

PYQ 2020

medium

chemistry ID: mht-cet-

A first-order reaction is 50% completed in 16 minutes. The percentage of reactant that will react in 32 minutes is

1

100%

2

12.5%

3

25%

4

75%

17

PYQ 2020

medium

chemistry ID: mht-cet-

For zero order reaction, when [A] is plotted against time (t), the slope of the straight line obtained is equal to

1

-k

2

k

3

[A]

4

-kt

18

PYQ 2020

medium

chemistry ID: mht-cet-

In the reaction, the rate of appearance of is . The rate of disappearance of is

1

2

3

4

19

PYQ 2020

medium

chemistry ID: mht-cet-

The reaction takes place in two steps as \text{(i) } \text{(ii) } \text{Identify the reaction intermediate.

1

2

3

4

20

PYQ 2020

medium

chemistry ID: mht-cet-

Which among the following is an example of pseudo first order reaction?

1

2

3

4

21

PYQ 2020

medium

chemistry ID: mht-cet-

In a first order reaction, 87.5% of reactant is converted into product in 15 minutes. The rate constant for the reaction is given by

1

2

3

4

22

PYQ 2020

medium

chemistry ID: mht-cet-

Half life of first order reaction is 20 minutes. What is the time taken to reduce the initial concentration of the reactant to th?}

1

2

3

4

Official Solution

Correct Option: $(2)$

$Step 1: Relation between half-life and rate constant. For a first order reaction, the half-life is given by: Given, Step 2: First order rate equation. For reduction to th of initial concentration: Step 3: Substitution of values. Step 4: Conclusion. Thus, the time required is .$

23

PYQ 2020

medium

chemistry ID: mht-cet-

$Which among the following is correct when energy of activation,, of the catalyzed reaction decreases at constant temperature and for same concentration?$

1

$decreases$

2

$decreases$

3

$decreases$

4

$decreases$

Official Solution

Correct Option: $(1)$

$Step 1: Arrhenius equation. The Arrhenius equation is given by: Step 2: Effect of catalyst on activation energy. A catalyst lowers the activation energy without affecting temperature or concentration. Step 3: Analyze each term. When decreases at constant, the term decreases directly. As a result, the exponential term increases and the rate constant increases. Step 4: Option analysis. (A) decreases — Correct (B) decreases — Incorrect, rate constant increases (C) decreases — Incorrect, it increases (D) decreases — Incorrect, its value becomes less negative Step 5: Conclusion. Thus, the correct statement is (A) decreases}.$

24

PYQ 2020

easy

chemistry ID: mht-cet-

$In the reaction: The rate of disappearance of H is 0.02 M/s. The rate of appearance of NH is:$

Official Solution

Correct Option: $(1)$

25

PYQ 2020

easy

chemistry ID: mht-cet-

$Which of the following is a character of catalyst?$

Official Solution

Correct Option: $(1)$

26

PYQ 2020

medium

chemistry ID: mht-cet-

$Which of the following is NOT dihydric phenol?$

1

$-naphthol$

2

$Resorcinol$

3

$Hydroquinone$

4

$Catechol$

Official Solution

Correct Option: $(1)$

$Step 1: Understanding dihydric phenols. Dihydric phenols have two hydroxyl (-OH) groups attached to a benzene ring. Hydroquinone, resorcinol, and catechol all have two hydroxyl groups. Step 2: Analyzing the options. (A) -naphthol: -naphthol is a phenol with only one hydroxyl group, so it is not a dihydric phenol. (B) Resorcinol: Resorcinol is a dihydric phenol with two hydroxyl groups at positions 1 and 3. (C) Hydroquinone: Hydroquinone is a dihydric phenol with two hydroxyl groups at positions 1 and 4. (D) Catechol: Catechol is a dihydric phenol with two hydroxyl groups at positions 1 and 2. Step 3: Conclusion. The correct answer is (A) -naphthol as it is not a dihydric phenol.$

27

PYQ 2020

medium

chemistry ID: mht-cet-

$Which among the following compound is NOT optically active?$

1

$3 - Chloropentane$

2

$2 - Chloropentane$

3

$2 - Chloro - 3 - methyl pentane$

4

$3 - Chloro - 2 - methyl pentane$

Official Solution

Correct Option: $(1)$

$Step 1: Optical activity and chirality. A compound is optically active if it contains a chiral center (a carbon atom attached to four different groups). Step 2: Analyzing the options. (A) 3 - Chloropentane: Incorrect — This compound is not optically active because the carbon at position 3 is not attached to four different groups, hence no chiral center is present. (B) 2 - Chloropentane: This compound is optically active as it has a chiral center. (C) 2 - Chloro - 3 - methyl pentane: This compound is also optically active due to the presence of a chiral center. (D) 3 - Chloro - 2 - methyl pentane: This compound is optically active due to a chiral center. Step 3: Conclusion. The correct answer is (A) 3 - Chloropentane because it lacks a chiral center and is thus not optically active.$

28

PYQ 2020

medium

chemistry ID: mht-cet-

$The rate constant for a second-order reaction, A Product is 1.62 M s . What will be the rate of reaction when the concentration of reactant is 2 10 M?$

1

$3.24 10 M s$

2

$3.24 10 M s$

3

$6.48 10 M s$

4

$210 M s$

Official Solution

Correct Option: $(3)$

$Step 1: Rate Law for a Second-Order Reaction. The rate of a second-order reaction is given by the equation: where is the rate constant, and is the concentration of reactant A. Step 2: Substituting the Given Values. We are given that the rate constant and the concentration of A is . Substituting these values into the rate law equation: Step 3: Conclusion. The rate of reaction is 6.48 10 M s, corresponding to option (C) .$

29

PYQ 2020

medium

chemistry ID: mht-cet-

$The rate law for the reaction is . If the concentration of is doubled and that of is halved, the new rate is; then what is the ratio of ?$

1

2

3

4

Official Solution

Correct Option: $(4)$

$Step 1: Understanding the rate law. The rate law for the reaction is given as . If the concentration of is doubled and that of is halved, the new rate can be written as: This gives the ratio . Thus, the ratio is, where and . Step 2: Analyzing the options. (A) : Incorrect. This is not the correct ratio. (B) :} Incorrect. This is not the correct expression for the ratio. (C) : Incorrect. This does not give the correct ratio. (D) : Correct — This is the correct ratio, where and . Step 3: Conclusion. The correct answer is (D), as this represents the correct ratio of rates in the given rate law.$

30

PYQ 2020

medium

chemistry ID: mht-cet-

$The rate law for the reaction is} Then which among the following statements is correct?$

1

$The reaction is first order in, first order in NO and second order overall.$

2

$The reaction is second order in NO, zero order in and second order overall.$

3

$The reaction is second order in NO, first order in and third order overall.$

4

$The reaction is zero order overall.$

Official Solution

Correct Option: $(3)$

$Step 1: Understand the rate law. The given rate law is: The powers of concentration terms indicate the order of reaction with respect to each reactant. Step 2: Determine individual orders. Order with respect to NO . Order with respect to . Step 3: Calculate overall order. Overall order of the reaction is the sum of individual orders: Step 4: Analyze the options. (A) Incorrect — overall order is not 2. (B) Incorrect — is not zero order. (C) Correct — it correctly represents individual and overall orders. (D) Incorrect — the reaction is not zero order. Step 5: Conclusion. The reaction is second order in NO, first order in oxygen, and third order overall.$

31

PYQ 2020

medium

chemistry ID: mht-cet-

$Which among the following is used as refrigerants and for air conditioning?$

1

$Trichloro methane$

2

$Carbon tetrachloride$

3

$Dichloromethane$

4

$Dichloro difluoro methane$

Official Solution

Correct Option: $(4)$

$Step 1: Understanding refrigerants. Dichloro difluoro methane (CFC-12) is a chlorofluorocarbon used widely as a refrigerant and in air conditioning due to its low boiling point and non-flammability. Step 2: Analyzing the options. (A) Trichloro methane: This is also known as chloroform, but it is not commonly used as a refrigerant. (B) Carbon tetrachloride: This was once used as a refrigerant but is now avoided due to its toxicity and harmful environmental effects. (C) Dichloromethane: This is used as a solvent but not as a refrigerant. (D) Dichloro difluoro methane: This is the correct answer, as it is used as a refrigerant in air conditioning systems. Step 3: Conclusion. The correct answer is (D) Dichloro difluoro methane .$

32

PYQ 2020

medium

chemistry ID: mht-cet-

$Which among the following compounds belongs to lipids?$

1

$Cloroxyleneol$

2

$Terpenes$

3

$BHA$

4

$Novestrol$

Official Solution

Correct Option: $(2)$

$Step 1: Understanding lipids. Lipids are a broad group of naturally occurring compounds that include fats, oils, waxes, and terpenes. Terpenes are hydrocarbons found in essential oils and are classified as lipids due to their solubility in organic solvents and role in biological processes. Step 2: Analyzing the options. (A) Cloroxyleneol: This is not a lipid but a disinfectant. (B) Terpenes: This is the correct answer as terpenes are naturally occurring compounds that are part of lipids. (C) BHA: BHA (Butylated HydroxyToluene) is an antioxidant, not a lipid. (D) Novestrol: This is a synthetic compound used in pharmaceuticals, not a lipid. Step 3: Conclusion. The correct answer is (B) Terpenes .$

33

PYQ 2020

medium

chemistry ID: mht-cet-

$For the first order reaction A \to B, the rate constant is 0.25 s, if the concentration of A is reduced to half, the value of the rate constant will be$

1

$2.25 s$

2

$0.075 s$

3

$0.30 s$

4

$0.25 s$

Official Solution

Correct Option: $(4)$

$Step 1: Understanding first-order reactions. For a first-order reaction, the rate constant remains constant regardless of the concentration of reactants. Hence, when the concentration of A is halved, the rate constant will not change. Step 2: Analyzing the options. (A) 2.25 s : Incorrect — The rate constant does not change for first-order reactions. (B) 0.075 s : Incorrect — The rate constant remains the same. (C) 0.30 s : Incorrect — The rate constant is unchanged. (D) 0.25 s : Correct — The rate constant for a first-order reaction remains constant. Step 3: Conclusion. The correct answer is (D) 0.25 s, as the rate constant for a first-order reaction does not change with concentration.$

34

PYQ 2020

medium

chemistry ID: mht-cet-

$Which among the following is an example of a zero order reaction?$

1

$Decomposition of N O in presence of catalyst$

2

$Inversion of C H O$

3

$Hydrolysis of CH COOCH$

4

$Decomposition of N O$

Official Solution

Correct Option: $(1)$

$Step 1: Understanding zero-order reactions. A zero-order reaction has a rate that is independent of the concentration of reactants. The decomposition of N O in the presence of a catalyst is a typical example of a zero-order reaction, where the rate is constant and independent of the concentration of the reactant. Step 2: Analyzing the options. (A) Decomposition of N O in presence of catalyst: This is correct. This is a zero-order reaction where the rate is constant and does not depend on the concentration of N O. (B) Inversion of C H O : This is incorrect. The inversion of sucrose is a first-order reaction. (C) Hydrolysis of CH COOCH : This is incorrect. Hydrolysis of esters is typically a second-order reaction. (D) Decomposition of N O : This is incorrect. The decomposition of N O is a first-order reaction. Step 3: Conclusion. The correct answer is (A) Decomposition of N O in presence of catalyst .$

35

PYQ 2020

medium

chemistry ID: mht-cet-

$60 g of CH₃COOH dissolved in 1 dm³ solvent. What is molality of solution? (density = 1.25 g/cm³)$

1

$0.8 m$

2

$0.4 m$

3

$0.2 m$

4

$0.6 m$

Official Solution

Correct Option: $(1)$

$Step 1: Formula for molality. Molality is defined as the number of moles of solute per kilogram of solvent. We use the formula: Where: -, - is the mass of the solvent in kg. Step 2: Calculation. The mass of acetic acid is 60 g, and the molar mass of CH₃COOH is 60 g/mol. Hence, the number of moles of CH₃COOH is: Now, we calculate the mass of the solvent. Given that the density of the solution is 1.25 g/cm³, the volume of the solution is 1 dm³ (1000 cm³). Thus, the total mass of the solution is: Since the mass of the solute is 60 g, the mass of the solvent is: Now, molality is: Step 3: Conclusion. The molality of the solution is approximately 0.8 m. Thus, the correct answer is (A) 0.8 m .$

36

PYQ 2020

medium

chemistry ID: mht-cet-

$The rate law for the reaction is expressed as What is the overall order of the reaction?$

1

$3$

2

$0$

3

$1$

4

$2$

Official Solution

Correct Option: $(1)$

$Step 1: Recall definition of order of reaction. The overall order of a reaction is the sum of powers of concentration terms in the rate law. Step 2: Add the powers from rate expression. Step 3: Conclusion. Hence, the overall order of the reaction is 3.$

37

PYQ 2020

medium

chemistry ID: mht-cet-

$Which of the following is a synthetic estrogen derivative?$

1

$Tegamet$

2

$Norethindrone$

3

$Novestrol$

4

$Ranitidine$

Official Solution

Correct Option: $(3)$

$Step 1: Understanding synthetic estrogen derivatives. Synthetic estrogens are chemicals that mimic the action of estrogen in the body. Novestrol is a synthetic estrogen derivative, commonly used in hormonal treatments. Step 2: Analyzing the options. (A) Tegamet: Tegamet (cimetidine) is a histamine receptor antagonist, not an estrogen derivative. (B) Norethindrone: Norethindrone is a synthetic progestin, not an estrogen. (C) Novestrol: Correct — Novestrol is a synthetic estrogen derivative. (D) Ranitidine: Ranitidine is a medication used to treat ulcers and reflux, not a synthetic estrogen. Step 3: Conclusion. The correct answer is (C) Novestrol .$

38

PYQ 2020

medium

chemistry ID: mht-cet-

$In PCl molecule, the angle Cl-P-Cl present in a plane is equal to$

1

$180°$

2

$120°$

3

$90°$

4

$104°$

Official Solution

Correct Option: $(2)$

$Step 1: Understanding the molecular geometry of PCl . PCl has a trigonal bipyramidal structure. In this geometry, the three chlorine atoms in the equatorial plane form 120° angles with each other. The axial chlorine atoms are positioned at 90° angles with the equatorial plane. Step 2: Analyzing the options. (A) 180°: This is incorrect. The angle between two chlorines in the same plane is 120°. (B) 120°: Correct — In the equatorial plane of a trigonal bipyramidal molecule, the chlorine atoms are at 120° from each other. (C) 90°: This is incorrect. The 90° angle is between the axial and equatorial chlorine atoms. (D) 104°: This is incorrect. The 104° angle is characteristic of a bent geometry, like in H O, not PCl . Step 3: Conclusion. The correct angle is (B) 120° .$

39

PYQ 2020

medium

chemistry ID: mht-cet-

$For the reaction, if the rate of disappearance of is, what is the rate of formation of water?$

1

2

3

4

Official Solution

Correct Option: $(4)$

$Step 1: Write the stoichiometric rate relation. For the reaction the rates are related as: Step 2: Substitute the given rate. Step 3: Calculate the rate of formation of water. Step 4: Conclusion. Hence, the rate of formation of water is .$

40

PYQ 2020

medium

chemistry ID: mht-cet-

$What is the relative rate of reaction for ?$

1

2

$Less than$

3

4

Official Solution

Correct Option: $(4)$

$Step 1: Nature of the substrate. is a secondary alkyl halide. Step 2: Reference standard. In relative rate studies of reactions, secondary alkyl halides are taken as the standard with rate equal to 1. Step 3: Conclusion. Therefore, the relative rate of the reaction is .$

41

PYQ 2020

medium

chemistry ID: mht-cet-

$The reaction is first order in, having rate constant . What is the value of rate of reaction when concentration of is 1.25 mol L ?$

1

2

3

4

Official Solution

Correct Option: $(2)$

$Step 1: First-order rate law. For a first-order reaction, the rate law is given by: Where is the rate constant and is the concentration of the reactant. Step 2: Substituting values. Substitute the given values: Step 3: Conclusion. The correct answer is (B) .$

42

PYQ 2022

easy

chemistry ID: mht-cet-

$What is the formula for zero order reaction?$

Official Solution

Correct Option: $(1)$

$Concept: In chemical kinetics, a zero-order reaction is one in which the rate of the reaction is independent of the concentration of the reactant(s). That means even if the concentration of the reactant changes, the reaction rate remains constant. Integrated Rate Law for Zero-Order Reaction: The formula is: [A] = [A] 0 - kt Where: • [A] is the concentration of reactant A at time t • [A] 0 is the initial concentration of reactant A • k is the rate constant (with units mol\cdotL⁻¹\cdots⁻¹ for zero-order) • t is the time elapsed Explanation: Since the reaction is zero order, the rate of reaction = k, which is constant. Integrating this with respect to time gives a straight-line equation. This is similar to the slope-intercept form of a straight line (y = mx + c), where [A] decreases linearly with time. Graphically, if you plot [A] vs. time (t), you'll get a straight line with a negative slope equal to -k and y-intercept equal to [A] 0 . When [A] reaches zero, the reaction stops because the reactant is fully consumed. Real-life Applications: Zero-order kinetics are observed in some enzymatic reactions when the enzyme is saturated, and also in the decomposition of gases on metal surfaces like platinum or gold. Conclusion: The integrated rate law for a zero-order reaction is: [A] = [A] 0 - kt This equation is essential in understanding reaction mechanisms and predicting how concentration changes over time.$

43

PYQ 2022

easy

chemistry ID: mht-cet-

$Ammonia and oxygen react at high temperature as in reaction, 4HN 3 (g) + 5O 2 (g) \to 4NO(g) + 6H 2 O(g) If rate of formation of NO is 3.6 x 10 -3 mol L -1 .sec -1 . Calculate the rate of formation of water.$

1

$6.0 x 10 -3 mol L -1 sec -1$

2

$3.6 x 10 -3 mol L -1 sec -1$

3

$1.8 x 10 -3 mol L -1 sec -1$

4

$5.4 x 10 -3 mol L -1 sec -1$

Official Solution

Correct Option: $(4)$

$Solution: The given reaction is: 4NH₃(g) + 5O₂(g) \to 4NO(g) + 6H₂O(g) The problem asks to calculate the rate of formation of water, given that the rate of formation of NO is 3.6 x 10⁻³ mol L⁻¹ sec⁻¹. Step 1: Understanding the Stoichiometric Ratio From the balanced equation, we can see that for every 4 moles of NO formed, 6 moles of H₂O are formed. This is a stoichiometric ratio of 4:6 or 2:3. This means that for every 4 moles of NO, 6 moles of H₂O will be formed. Step 2: Relating the Rate of Formation of NO to H₂O The rate of formation of NO is given as 3.6 x 10⁻³ mol L⁻¹ sec⁻¹. Since the ratio of NO to H₂O is 2:3, we can calculate the rate of formation of H₂O using the stoichiometric relationship. Step 3: Calculating the Rate of Formation of Water We can now calculate the rate of formation of H₂O as follows: Rate of formation of H₂O = (3.6 x 10⁻³ mol L⁻¹ sec⁻¹) \times (6 / 4) = 5.4 x 10⁻³ mol L⁻¹ sec⁻¹ Conclusion: The rate of formation of water is 5.4 x 10⁻³ mol L⁻¹ sec⁻¹, which corresponds to Option (D) .$

44

PYQ 2023

easy

chemistry ID: mht-cet-

$Find the ratio of the t 0 and t for a first-order reaction.$

Official Solution

Correct Option: $(1)$

$The ratio of t₀ and t for a first-order reaction is given by the equation: Explanation: This equation represents the relationship between the time taken for a reaction to occur at various stages in a first-order reaction. Let's break it down: t₀: This is the initial time of the reaction, often considered as the time when the reaction starts, or the time at which the concentration of reactants is at its maximum. t: This is the time at which the reaction is measured or observed, where the concentration of reactants has decreased due to the progress of the reaction. k: This is the rate constant for the first-order reaction, which dictates how fast the reaction proceeds. It is a measure of the reaction's speed, with higher values of k indicating faster reactions. The equation illustrates the inverse relationship between the reaction time and the rate constant. As the rate constant increases, the time t required for the reaction to progress decreases. This equation can be used to estimate the rate constant k if the times t₀ and t are known. Important Concept: The factor 2.303 comes from the mathematical derivation of the integrated rate law for a first-order reaction, which involves logarithms. The general form of the rate law for a first-order reaction is: Where [A₀] is the initial concentration of reactant A, and [A] is the concentration of A at time t. In this case, the equation is simplified to give the relationship above when using logarithms to solve for reaction time.$

45

PYQ 2024

medium

chemistry ID: mht-cet-

$The rate constant for a first-order reaction whose half-life is 480 seconds is:$

1

2

3

4

Official Solution

Correct Option: $(3)$

$For a first-order reaction, the rate constant is related to the half-life using the equation: Substitute the given value of : Simplifying: This value represents the rate constant for the reaction, which depends solely on the half-life for first-order processes. Final Answer:$

46

PYQ 2024

medium

chemistry ID: mht-cet-

$Find the pH if,, and are given.$

1

2

3

4

Official Solution

Correct Option: $(3)$

$Using the Henderson-Hasselbalch equation for a basic buffer: and the relationship: Substitute the given values:,, . Step 1: Substitute into the equation: Step 2: Simplify the logarithmic term: Using : Step 3: Calculate the pH: Final Answer:$

47

PYQ 2024

easy

chemistry ID: mht-cet-

$In 2-chloro-3,4-dimethylhexane, how many chiral carbon atoms are present?$

1

2

3

4

Official Solution

Correct Option: $(2)$

$A chiral carbon atom is bonded to four different groups. The structure of 2-chloro-3,4-dimethylhexane can be analyzed as follows: - The second carbon (C-2) is chiral because it is attached to a chlorine atom, a methyl group, an ethyl group, and a hydrogen atom. - The third carbon (C-3) is also chiral because it is bonded to a methyl group, a 2-chloropropyl group, a hydrogen atom, and another unique substituent. Other carbons in the molecule do not satisfy the chiral carbon criteria. Hence, there are 2 chiral carbons.$

48

PYQ 2024

medium

chemistry ID: mht-cet-

$Which of the following represents the rate equation for a zero-order reaction?$

1

2

3

4

Official Solution

Correct Option: $(3)$

$In a zero-order reaction, the rate of reaction is independent of the concentration of the reactants. The rate law for a zero-order reaction is simply: where is the rate constant. This means that no matter how much of the reactant is present, the rate of the reaction remains constant over time. For the other options: - Option (1) represents a first-order reaction. - Option (2) represents a second-order reaction. - Option (4) represents a general order reaction, where can be any value. Therefore, the correct answer is, representing a zero-order reaction.$

49

PYQ 2024

medium

chemistry ID: mht-cet-

$Cross Cannizzaro of formaldehyde and benzaldehyde give a mixture of:$

1

$Benzyl alcohol and sodium formate$

2

$Benzyl alcohol and formic acid$

3

$Benzaldehyde and sodium acetate$

4

$Benzaldehyde and sodium formate$

Official Solution

Correct Option: $(1)$

$Step 1: The Cannizzaro reaction involves the disproportionation of non-enolizable aldehydes in the presence of a strong base. Formaldehyde undergoes reduction, and benzaldehyde undergoes oxidation to form a mixture of products. In this case, the products are benzyl alcohol and sodium formate. Conclusion: The correct answer is benzyl alcohol and sodium formate.$

50

PYQ 2024

medium

chemistry ID: mht-cet-

$Which of the following represents the expression for the 3/4th life of a 1st-order reaction?$

1

2

3

4

Official Solution

Correct Option: $(2)$

$Step 1: For a first-order reaction, the half-life is given by . To find the expression for, we use the following relationship for first-order reactions: Conclusion: The correct expression for the 3/4th life of a first-order reaction is given by option (B).$

51

PYQ 2024

medium

chemistry ID: mht-cet-

$The plot that represents the zero-order reaction is:$

1

2

3

4

Official Solution

Correct Option: $(2)$

$we start by analyzing the characteristics of a zero-order reaction. The defining feature of zero-order kinetics is that the rate of reaction does not depend on the concentration of the reactant. The rate law is given as: This indicates a constant rate of reaction throughout the process. Graphical Approach: For a zero-order reaction, the integrated rate equation is: where is the initial concentration, is the rate constant, and is time. This equation represents a straight-line graph when is plotted against, with: - Slope = (negative value due to the decreasing concentration over time). - Y-intercept = . Deriving the Correct Plot: To verify the graphical representation, consider the following steps: 1. At :, which matches the y-intercept. 2. At :, which corresponds to the time at which the reactant is fully consumed. Thus, the plot of versus will be a straight line with a downward slope, consistent with the equation. Final Answer: (2)$

52

PYQ 2024

medium

chemistry ID: mht-cet-

$Which one of the following is vinyl alcohol?$

1

$But-2-en-2-ol$

2

$Prop-2-en-1-ol$

3

$Ethanol$

4

$Methanol$

Official Solution

Correct Option: $(2)$

$Vinyl alcohol () is an unstable tautomer of acetaldehyde. It is represented by the IUPAC name Prop-2-en-1-ol: Explanation: But-2-en-2-ol does not match the structure of vinyl alcohol. Prop-2-en-1-ol matches the structural and chemical characteristics of vinyl alcohol.$

53

PYQ 2025

easy

chemistry ID: mht-cet-

$For a reaction, the rate law is given by . If the concentration of is doubled and the concentration of is halved, how will the rate of the reaction change?$

1

$The rate will be doubled.$

2

$The rate will be halved.$

3

$The rate will be quadrupled.$

4

$The rate will remain unchanged.$

Official Solution

Correct Option: $(3)$

$The rate law for the given reaction is: Where: - is the rate constant, - and are the concentrations of reactants and . We are told that the concentration of is doubled and the concentration of is halved. Let the initial concentrations of and be and, respectively. Then, the new concentrations are: Now, substitute these into the rate law: Comparing the new rate with the original rate: Thus, the new rate is twice the original rate. Therefore, the rate will be quadrupled.$

54

PYQ 2025

medium

chemistry ID: mht-cet-

$Identify isoelectronic pair from following.$

1

$Ne and$

2

$and$

3

$and$

4

$and$

Official Solution

Correct Option: $(1)$

$Step 1: Concept Isoelectronic species are atoms or ions that have the same number of electrons. Step 2: Electron Count - (A); . (Match) - (B); . - (C); . - (D); . Step 3: Conclusion Only Ne and have the same number of electrons. Final Answer: (A)$

55

PYQ 2025

hard

chemistry ID: mht-cet-

$The decomposition of a compound A follows first-order kinetics. The concentration of A at time t = 0 is 1.0 mol L -1 . After 60 minutes, it reduces to 0.25 mol L -1 . What is the initial rate of the reaction at t = 0? (Take ln 2 = 0.693)$

1

$0.0115 mol L min$

2

$0.0173 mol L min$

3

$0.277 mol L min$

4

$0.0364 mol L min$

Official Solution

Correct Option: $(1)$

$For a first-order reaction, the integrated rate law is given by: Where: - (initial concentration) - (concentration after 60 minutes) - is the rate constant - First, calculate the rate constant using the integrated rate law: Thus, the initial rate of the reaction is .$

56

PYQ 2025

medium

chemistry ID: mht-cet-

$The rate constant of a first-order reaction is . What is the half-life of the reaction?$

1

$0.347 s$

2

$1.4 s$

3

$0.693 s$

4

$2.0 s$

Official Solution

Correct Option: $(1)$

$For a first-order reaction, the half-life is given by the equation: Where: - is the rate constant. Substitute the values: Thus, the half-life of the reaction is approximately 0.347 s.$

57

PYQ 2025

medium

chemistry ID: mht-cet-

$For a reaction A B, the rate law is given by: If the concentration of A is increased by a factor of 3, by what factor does the rate of the reaction increase?$

1

$3$

2

$9$

3

$27$

4

$6$

Official Solution

Correct Option: $(2)$

$The rate law for the reaction is given by: Where: - is the rate constant, - is the concentration of reactant A. If the concentration of A is increased by a factor of 3, then: Substitute this new concentration into the rate law: Thus, the rate of the reaction increases by a factor of 9.$

58

PYQ 2025

hard

chemistry ID: mht-cet-

$For the reaction: The rate law is given as: If the concentration of A is doubled and the concentration of B is halved, how does the rate of the reaction change?$

1

$It remains the same.$

2

$It increases by a factor of 4.$

3

$It doubles.$

4

$It decreases by a factor of 2.$

Official Solution

Correct Option: $(3)$

$The rate law is given by: Step 1: Initial Rate Expression Let's say the initial concentrations of and are and, and the initial rate is: Step 2: New Concentrations The concentration of is doubled: The concentration of is halved: Step 3: New Rate Expression Substituting the new concentrations into the rate law: Simplifying: Step 4: Comparing the New Rate with the Initial Rate The initial rate was: The new rate is: ✅ Final Answer: The rate of the reaction doubles, so the correct answer is .$

59

PYQ 2025

hard

chemistry ID: mht-cet-

$The rate constant for a first-order reaction is . What is the half-life of the reaction?$

1

2

3

4

Official Solution

Correct Option: $(2)$

$Step 1 — Recall the half-life formula for a first-order reaction For a first-order reaction the half-life is independent of concentration and is given by the well-known formula: . Step 2 — Substitute values and compute Use (often approximated as 0.693). Since, the quotient is approximately (Using the more precise ln2 gives min, which rounds to 10.0 min.) Step 3 — Units and significant figures • The rate constant k is given in min⁻¹, so the resulting time is in minutes . • Given k = 0.0693 (4 significant digits) and ln2 \approx 0.6931, the half-life computed to two or three significant figures is 10.0 min . For typical multiple-choice reporting, 10 min is the correct choice. Quick verification If min, then, which matches the given k = 0.0693 min⁻¹ within the given precision. Final answer (clear) The half-life is . (Select the option: 10 min .) Note: This derivation follows directly from the integrated first-order rate law. The result is independent of initial concentration and depends only on k.$

60

PYQ 2025

medium

chemistry ID: mht-cet-

$The solubility product of a sparingly soluble salt AX is . What is its solubility in ?$

1

2

3

4

Official Solution

Correct Option: $(3)$

$Concept: Step 1: Find solubility. Step 2: Calculate. Step 3: Conclusion. Solubility =$

61

PYQ 2025

medium

chemistry ID: mht-cet-

$Identify a monomer used in preparation of neoprene.$

1

$2-methyl-1,3-butadiene$

2

$2-chloro-1,3-butadiene$

3

$Melamine$

4

$1,3-butadiene$

Official Solution

Correct Option: $(2)$

$Step 1: Concept Neoprene is a synthetic rubber formed by the free radical polymerization of chloroprene. Step 2: Identification The chemical name for chloroprene is 2-chloro-1,3-butadiene. Step 3: Comparison - (A) is Isoprene (Natural rubber monomer). - (D) is the monomer for Buna rubbers. Final Answer: (B)$

62

PYQ 2025

hard

chemistry ID: mht-cet-

$For a reaction A B, the rate doubles when temperature increases from 298 K to 308 K. What is the activation energy (Ea)?$

1

$52 kJ/mol$

2

$48 kJ/mol$

3

$62 kJ/mol$

4

$66 kJ/mol$

Official Solution

Correct Option: $(2)$

$We use the Arrhenius equation to calculate activation energy: Where is the rate constant, is the pre-exponential factor, is the activation energy, is the gas constant (8.314 J/molÂ\cdotK), and is the temperature in Kelvin. The rate doubles, so: Using the logarithmic form of the Arrhenius equation: Substitute the known values: Solving for :$

63

PYQ 2025

medium

chemistry ID: mht-cet-

$What is the volume occupied by of at STP?$

1

2

3

4

Official Solution

Correct Option: $(2)$

$Concept: At STP (0Â°C, 1 atm): Step 1: Use proportional relation. Step 2: Calculate. Step 3: Conclusion.$

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Chapter Questions 63 MCQs

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Step 1: Initial Rate Expression

Step 2: New Concentrations

Step 3: New Rate Expression

Step 4: Comparing the New Rate with the Initial Rate

✅ Final Answer:

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Chapter Questions
63 MCQs