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Master 75 Percent Reaction Completion MCQs with Answers Chemistry for NEET, JEE & CUET Aspirants

Master 75 Percent Reaction Completion MCQs with Answers Chemistry for NEET, JEE & CUET Aspirants

Chemical kinetics is an important chapter in Class 12 chemistry because it explains how fast reactions occur and what factors influence reaction rates. One of the frequently tested topics in kinetics is reaction completion, especially problems related to percentage completion of reactions. Among these, 75 percent reaction completion MCQs with answers chemistry are commonly asked in board exams and competitive entrance tests. Understanding how to solve 75 percent reaction completion MCQs with answers chemistry helps aspirants develop strong analytical skills in reaction kinetics.

In chemical reactions, percentage completion refers to the fraction of reactants that has been converted into products over time. Many 75 percent reaction completion MCQs with answers chemistry focus on determining the time required for a reaction to reach a specific level of completion. This is especially common in first order reactions where the rate of reaction depends directly on the concentration of the reactant. Practicing 75 percent reaction completion MCQs with answers chemistry allows aspirants to become comfortable with applying the integrated rate equations of first order reactions.

In a first order reaction, the integrated rate equation is expressed as
k = (2.303/t) log(a/(a − x)),
where a is the initial concentration and x is the amount reacted at time t. When solving 75 percent reaction completion MCQs with answers chemistry, aspirants typically substitute values corresponding to 75% conversion of the reactant. This means that 75% of the initial concentration has reacted and only 25% of the original concentration remains. Using this relationship makes solving 75 percent reaction completion MCQs with answers chemistry much easier.

Another important concept that appears frequently in 75 percent reaction completion MCQs with answers chemistry is the relationship between half-life and reaction completion. For a first order reaction, the half-life remains constant and independent of initial concentration. This property allows aspirants to determine the time required for different percentages of completion using multiples of the half-life. Many 75 percent reaction completion MCQs with answers chemistry rely on understanding how multiple half-lives correspond to increasing levels of conversion.

Graphical interpretation is also an important tool when dealing with 75 percent reaction completion MCQs with answers chemistry. For example, plots of logarithmic concentration versus time produce straight lines for first order reactions. From such graphs, aspirants can determine rate constants and estimate the time required for specific reaction completions. These graphical techniques are often tested through conceptual 75 percent reaction completion MCQs with answers chemistry.

Temperature effects also influence reaction completion times. As temperature increases, the rate constant increases according to the Arrhenius equation, leading to faster reactions. Many 75 percent reaction completion MCQs with answers chemistry compare reaction completion times at different temperatures to test aspirants’ understanding of temperature dependence in chemical kinetics.

Another aspect highlighted in 75 percent reaction completion MCQs with answers chemistry is the difference between reaction order and molecularity. Reaction order is determined experimentally from the rate law, while molecularity refers to the number of molecules involved in an elementary step. This distinction often appears in conceptual 75 percent reaction completion MCQs with answers chemistry to evaluate deeper understanding of reaction mechanisms.

In many competitive exams such as NEET and JEE, numerical problems are frequently framed around percentage completion concepts. By consistently practicing 75 percent reaction completion MCQs with answers chemistry, aspirants learn how to interpret data quickly and apply the correct formulas. This practice improves both speed and accuracy when solving kinetics problems.

75 percent reaction completion MCQs with answers chemistry:

1. Zero Order Graph

Q1. For a zero order reaction, the plot of concentration of reactant vs time is:

A. Linear with negative slope and zero intercept
B. Linear with positive slope and zero intercept
C. Linear with negative slope and non-zero intercept
D. A curve asymptotic to concentration axis

Answer: C

2. Half-life and Pressure

Q2. At 500 K, half-life at 80 kPa is 350 s and at 40 kPa is 175 s. The order of reaction is:

A. Zero
B. One
C. Two
D. Three

Answer: A

3. Effect of Concentration Change

Q3. Reaction: 2A + B + C → D + E
Order: A = 1, B = 2, C = 0
If all concentrations are doubled, rate becomes:

A. 2 times
B. 8 times
C. 24 times
D. None

Answer: B

4. Elementary Reaction

Q4. Which of the following are most likely elementary reactions?

A. 3 only
B. 1 and 3
C. 1 and 4
D. 1, 2 and 3

Answer: C

5. Zero Order Statements

Q5. Which statements are correct?

A. I only
B. I and II only
C. I and IV only
D. I and III only

Answer: C

6. Order of Reaction

Q6. Rate becomes nine times when concentration changes from 1.2×10−31.2×10^{-3} to 3.24×10−23.24×10^{-2}. Order is:

A. 1/2
B. 3/2
C. 1/3
D. 2/3

Answer: D

7. Temperature Effect

Q7. Rate constant doubles between 20°C and 25°C. Increase from 20°C to 40°C:

A. 8 times
B. 16 times
C. 32 times
D. 64 times

Answer: B

8. Rate After Conversion

Q8. Reaction: A + B → Products
Order: A = 1, B = 2
Initial rate = 1.0×10−21.0×10^{-2} mol L⁻¹ s⁻¹
Rate when 50% converted:

A. 1.0×10−21.0×10^{-2}
B. 0.05×10−20.05×10^{-2}
C. 1.25×10−31.25×10^{-3}
D. 4.0×10−24.0×10^{-2}

Answer: C

9. First Order Integrated Equation

Q9. Integrated equation is:

A. k=2.303tlog⁡a−xak=\frac{2.303}{t}\log\frac{a-x}{a}
B. k=1tlog⁡aa−xk=\frac{1}{t}\log\frac{a}{a-x}
C. k=2.303tlog⁡aa−xk=\frac{2.303}{t}\log\frac{a}{a-x}
D. −k=1tlog⁡a−xa-k=\frac{1}{t}\log\frac{a-x}{a}

Answer: C

10. First Order Equation Form

Q10. First order rate expression:

A. k=xtk=\frac{x}{t}
B. k=−2.303tlog⁡aa−xk=-\frac{2.303}{t}\log\frac{a}{a-x}
C. k=1tln⁡aa−xk=\frac{1}{t}\ln\frac{a}{a-x}
D. k=1txa(a−x)k=\frac{1}{t}\frac{x}{a(a-x)}

Answer: C

11. Unit of Rate Constant

Q11. Unit of rate constant t−1t^{-1} corresponds to:

A. Zero order
B. First order
C. Second order
D. Third order

Answer: B

12. Order of Reaction

Q12. A + 2B → C with rate = k[A][B]. Order is:

A. 3
B. 2
C. 1
D. Zero

Answer: B

13. Half-life of First Order

Q13. Half-life is:

A. log⁡2k\frac{\log2}{k}
B. log⁡2k0.5\frac{\log2}{k\sqrt{0.5}}
C. ln⁡2k\frac{\ln2}{k}
D. 0.6930.5k\frac{0.693}{0.5k}

Answer: C

14. Reaction Completion

Q14. 50% complete in 2 h and 75% in 4 h. Order:

A. 1
B. 2
C. 3
D. Zero

Answer: A

15. Incorrect Statement

Q15. Which statement is incorrect?

A. Order determined experimentally
B. Order independent of stoichiometry
C. Order equals sum of powers in rate law
D. Order always whole number

Answer: D

16. Reaction Independent of Concentration

Q16. Which reaction does not depend on concentration?

A. Zero order
B. First order
C. Second order
D. Third order

Answer: A

17. Completion Time

Q17. If 75% completes in 40 min, 50% completes in:

A. 16 min
B. 25 min
C. 18 min
D. 20 min

Answer: D

18. Order from Plot

Q18. Straight line of (C0−C)/C(C_0-C)/C vs t indicates order:

A. Zero
B. One
C. Two
D. Three

Answer: C

19. Unit of Second Order Constant

Q19. Unit is:

A. s⁻¹
B. mol L⁻¹ s⁻¹
C. L mol⁻¹ s⁻¹
D. L mol⁻¹

Answer: C

20. Reaction Order from Rate Constant

Q20. k = 2.5×10−22.5×10^{-2} min⁻¹ indicates:

A. Zero
B. First
C. Second
D. Third

Answer: B

21. Order of Reaction

Q21. Order can be:

A. Zero
B. Fraction
C. Whole number
D. Integer, fraction, or zero

Answer: D

22. Ammonium Nitrite Decomposition

Q22. Order is:

A. Zero
B. One
C. Two
D. Three

Answer: B

23. Pressure Effect

Q23. For reaction 2NO + O₂ → 2NO₂, rate becomes:

A. One-fourth
B. One-eighth
C. Eight times
D. Four times

Answer: C

24. Two-third Life

Q24. Two-third life of first order reaction:

A. 8×10138×10^{13} s
B. 2×10132×10^{13} s
C. 8×10148×10^{14} s
D. 5×10145×10^{14} s

Answer: B

25. Decomposition of H₂O₂

Q25. Time required:

A. 4 min
B. 15 min
C. 30 min
D. 60 min

Answer: D

26. Molecularity and Order

Q26. Reaction: (CH3)3CCl+OH−→(CH3)3COH+Cl−(CH₃)₃CCl + OH⁻ → (CH₃)₃COH + Cl⁻

A. (2,2)
B. (2,1)
C. (1,2)
D. (1,1)

Answer: B

27. First Order Completion

Q27. 75% completed in 32 min. 50% completion time:

A. 8 min
B. 16 min
C. 20 min
D. 24 min

Answer: B

28. Order from Half-life Graph

Q28. Order from graph is:

A. Zero
B. One
C. Two
D. Three

Answer: C

29. Hydrolysis Reaction

Q29. Reaction RCl + H₂O → ROH + HCl (excess water):

A. Molecularity 2, order 2
B. Molecularity 2, order 1
C. Molecularity 1, order 2
D. Molecularity 1, order 1

Answer: B

30. Molecularity Statement

Q30. Which statement is wrong?

A. Molecularity may be fractional
B. Determined from mechanism
C. Number of molecules in elementary step
D. Equal to order for elementary reaction

Answer: A

75 percent reaction completion MCQs with answers chemistry

Conclusion on 75 percent reaction completion MCQs with answers chemistry

In conclusion, mastering reaction completion concepts is essential for understanding chemical kinetics. Regular practice with 75 percent reaction completion MCQs with answers chemistry strengthens conceptual clarity, improves numerical problem-solving ability, and helps aspirants confidently tackle exam questions related to reaction rates. By focusing on 75 percent reaction completion MCQs with answers chemistry, aspirants can build a strong foundation in kinetics and perform better in both academic examinations and competitive entrance tests.

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