Assertion (A): For a first order reaction, the half-life does not depend on the initial concentration of the reactant. Reason (R): For a first order reaction, $t_{1/2} = \frac{0.693}{k}$. Choose the correct option:

Both A and R are true and R is the correct explanation of A

Both A and R are true but R is not the correct explanation of A

According to collision theory, the rate constant of a bimolecular reaction depends on all of the following EXCEPT:

The initial concentration of the reactants

The frequency factor (collision frequency)

The temperature of the reaction

The activation energy of the reaction

Chapter testChemistryIncluded in the seriesTest 9 of 36

CBSE Class 12 Science Chemistry · Ch 3: Chemical Kinetics

CBSE Class 12 Science Chemistry · Ch 3: Chemical Kinetics is an online chapter test in the CBSE Class 12 Science pattern, covering Chemical Kinetics. Attempt it on SeatBeat with a timer like the real exam, then see a detailed solution for every question and your score and weak-topic analysis.

Questions

Minutes

Marks

None

Negative marking

Unlock all 36 tests — ₹199 Try English · Ch 1: The Last Lesson free →

Topics in this test

Topic	Subject	Questions
Chemical Kinetics	Chemistry	30

Difficulty: 7 medium · 23 hard

Chemical Kinetics MCQ questions with answers

The first 3 of 30 questions. Unlock the series for the rest, each with a solution.

Q1. Assertion (A): For a first order reaction, the half-life does not depend on the initial concentration of the reactant. Reason (R): For a first order reaction, $t_{1/2} = \frac{0.693}{k}$. Choose the correct option:
अभिकथन (A): प्रथम कोटि अभिक्रिया के लिए, अर्ध-आयु अभिकारक की प्रारंभिक सांद्रता पर निर्भर नहीं करती। कारण (R): प्रथम कोटि अभिक्रिया के लिए, $t_{1/2} = \frac{0.693}{k}$। सही विकल्प चुनिए:
- A. A is true but R is false / A सत्य है परन्तु R असत्य है
- B. Both A and R are true and R is the correct explanation of A / A और R दोनों सत्य हैं और R, A की सही व्याख्या है
- C. Both A and R are true but R is not the correct explanation of A / A और R दोनों सत्य हैं परन्तु R, A की सही व्याख्या नहीं है
- D. A is false but R is true / A असत्य है परन्तु R सत्य है
Solution
Since $t_{1/2}=\frac{0.693}{k}$ contains only the rate constant and no concentration term, the half-life is independent of initial concentration; R correctly explains A.
चूँकि $t_{1/2}=\frac{0.693}{k}$ में केवल वेग स्थिरांक है और कोई सांद्रता पद नहीं है, अतः अर्ध-आयु प्रारंभिक सांद्रता से स्वतंत्र है; R, A की सही व्याख्या करता है।
Q2. According to collision theory, the rate constant of a bimolecular reaction depends on all of the following EXCEPT:
संघट्ट सिद्धांत के अनुसार, एक द्विअणुक अभिक्रिया का वेग स्थिरांक निम्नलिखित सभी पर निर्भर करता है, सिवाय इसके:
- A. The frequency factor (collision frequency) / आवृत्ति गुणांक (संघट्ट आवृत्ति)
- B. The initial concentration of the reactants / अभिकारकों की प्रारंभिक सांद्रता
- C. The temperature of the reaction / अभिक्रिया का तापमान
- D. The activation energy of the reaction / अभिक्रिया की सक्रियण ऊर्जा
Solution
The rate constant depends on the frequency of collisions, the activation energy and temperature, but it does not depend on the initial concentration of the reactants.
वेग स्थिरांक संघट्टों की आवृत्ति, सक्रियण ऊर्जा और तापमान पर निर्भर करता है, परन्तु यह अभिकारकों की प्रारंभिक सांद्रता पर निर्भर नहीं करता।
Q3. For a zero order reaction, which of the following plots will give a straight line with a slope equal to $-k$?
एक शून्य कोटि अभिक्रिया के लिए, निम्नलिखित में से कौन सा आरेख $-k$ के बराबर ढाल वाली एक सीधी रेखा देगा?
- A. $\log[R]$ versus time / $\log[R]$ बनाम समय
- B. $[R]^2$ versus time / $[R]^2$ बनाम समय
- C. $\frac{1}{[R]}$ versus time / $\frac{1}{[R]}$ बनाम समय
- D. $[R]$ versus time / $[R]$ बनाम समय
Solution
The integrated law for zero order is $[R] = [R]_0 - kt$, so a plot of $[R]$ against $t$ is linear with slope $-k$.
शून्य कोटि के लिए समाकलित नियम $[R] = [R]_0 - kt$ है, अतः $[R]$ और $t$ के बीच का आरेख $-k$ ढाल वाला रैखिक होता है।

Frequently asked questions

How many questions are in the CBSE Class 12 Science Chemistry · Ch 3: Chemical Kinetics?

30 questions for 30 marks, to be answered in 20 minutes.

Is there negative marking in the CBSE Class 12 Science Chemistry · Ch 3: Chemical Kinetics?

No — wrong answers are not penalised in this test.

Which topics does the CBSE Class 12 Science Chemistry · Ch 3: Chemical Kinetics cover?

Chemical Kinetics (30 questions).

Is the CBSE Class 12 Science Chemistry · Ch 3: Chemical Kinetics free?

It is part of the CBSE Class 12 Science Test Series 2027 — Chapter-wise + Full Tests (36 tests, ₹199). You can first try English · Ch 1: The Last Lesson for free.

More tests in the CBSE Class 12 Science Test Series 2027 — Chapter-wise + Full Tests

See the full CBSE Class 12 Science Test Series 2027 — Chapter-wise + Full Tests → · CBSE Class 12 Science: pattern, notification & syllabus →

₹199

View the full series