CBSE Class 12 Chemistry sample paper 2024-25: question 5
From the official CBSE sample question paper for 2024-25, section A, question 5, for 1 mark. Try it first; the hints and our step-by-step solution are below.
Q5 · 1 mark · MCQChemical Kinetics
The initial concentration of R in the reaction is mol/L. What is the half life for the reaction if
- (A)30 s
- (B)3 s
- (C)1 s
- (D)10 s
Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2024-25.
Hints
Open one hint at a time and try again before the next.
Hint 1
Use the units of k to find the order of the reaction.
Hint 2
Recall the half-life formula for a zero order reaction.
Step-by-step solution
Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.
The unit of k is mol L s, so the reaction is zero order.
- 1 mark
s. Option (C).
Answer: 1 s, option (C)
Where the marks are
- Recognises zero order and calculates = 1 s (1 mark)
Revise the chapter
- Chapter: Chemical Kinetics (notes, formulas, where marks are lost and every past question)
- Topic: Integrated Rate Equations and Half-Life
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