A first order reaction has a specific reaction rate of 10^-2 s^-1 . How much time will it take for 20 g of the reactant to reduce to 5 g ? - Chemistry MCQ NEET 2017 2026 | ExamTest.live

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A first order reaction has a specific reaction rate of 1 0^{- 2} s^{- 1} . How much time will it take for 20 g of the reactant to reduce to 5 g ?

Solution & Step-by-step Explanation

1. t = \frac{2.303}{k} lo g (\frac{a}{a - x}) 2. t = \frac{2.303}{1 0 ^{- 2}} lo g (\frac{20}{5}) = 230.3 lo g (4) 3. t = 230.3 \times 2 \times lo g (2) = 230.3 \times 2 \times 0.3010 4. t \approx 230.3 \times 0.602 \approx 138.6 seconds .Alternatively, 20 \to 10 \to 5 is exactly two half-lives. t_{1/2} = \frac{0.693}{k} = 69.3 s . Total t = 2 \times 69.3 = 138.6 s .

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A first order reaction has a specific reaction rate of 1 0^{- 2} s^{- 1} . How much time will it take for 20 g of the reactant to reduce to 5 g ?

238.6 second

138.6 second

346.5 second

693.0 second

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