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NEET 2011
Exam
NEET
Year
2011
Subject
Chemistry
Chapter
Chemical Kinetics

NEET 2011 · Chemistry · Chemical Kinetics

The half-life of a substance in a certain enzyme-catalysed reaction...

The half-life of a substance in a certain enzyme-catalysed reaction is 138 s138 \mathrm{~s}. The time required for the concentration of the substance to fall from 1.28mgL−11.28 \mathrm{mg} \mathrm{L}^{-1} to 0.04mgL−10.04 \mathrm{mg} \mathrm{L}^{-1} is

Options

  1. A414 s414 \mathrm{~s}
  2. B552 s552 \mathrm{~s}
  3. C690 s690 \mathrm{~s}
  4. D276 s276 \mathrm{~s}

Correct answer

C. 690 s690 \mathrm{~s}

Step-by-step solution

Enzyme-catalysed reactions follow first order kinetics. 1.28⟶t1/20.64⟶t1/20.32⟶t1/20.16⟶t1/20.08⟶t1/20.04\begin{aligned}& 1.28 \stackrel{t_{1/2}}{\longrightarrow} 0.64 \stackrel{t_{1/2}}{\longrightarrow} 0.32 \stackrel{t_{1/2}}{\longrightarrow} 0.16 \\ & \stackrel{t_{1/2}}{\longrightarrow} 0.08 \stackrel{t_{1/2}}{\longrightarrow} 0.04 \end{aligned}∴ Time required =5×t1/2=5×138s=690s.\begin{aligned} \therefore\text{ Time required }& =5 \times t_{1/2} \\ & =5 \times138 \mathrm{ s}\\ & =690 \mathrm{ s} . \end{aligned}
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