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MODEL PAPER 10 — Chemistry STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 ScienceChemistryMODEL PAPER 101 Mark
MCQ
The reaction $A \rightarrow B$ is a second order process when the initial concentration of $A$ is $0.50 M$, the half life is $8.0$ minutes. What is the half life if the initial concentration of $A$ is $0.10 M?$
  • ✓
    $40.0$ minutes
  • B
    $1.6$ minutes
  • C
    $8.0$ minutes
  • D
    $16.0$ minutes
✓

Answer

Correct option: A.
$40.0$ minutes
Explanation: For second-order reaction:
$t_{1 / 2}=\frac{2 k}{[R]}$
$\Rightarrow k=\frac{t_{1 / 2}[R]}{2}$
Applying this equation,
$\frac{t_{1 / 2}[R]}{2}=\frac{t_{1_{1 / 2}}\left[R^{\prime}\right]}{2}$
$\frac{8.0 \times 0.50}{2}=\frac{t_{1 / 2}^{\prime} \times 0.10}{2}$
$t_{1 / 2}^{\prime}=\frac{8 \times 0.50}{0.10}=40$

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