In a first order reaction, the concentration of the reactant, decreases from 0.8 M to 0.4 M in 15 minutes. The time taken for the concentration to change from 0.1 M to 0.025 M is

Question

Aicharya · Accepted Answer

Order 1
Concentration changes from 0.8 M to 0.4 M in

(50 %)

15 minutes this half life is = 15 minutes =

t_{50}

A change from 0.1 M to 0.025 M is 75% and for first order reaction

t_{75} = 2 \times t_{50} = 2 \times 15 = 30

m i n u t e s

t_{50} = 15 m i n u t e s

k = \frac{2.303 l o g 2}{t_{50}} = \frac{2.303 l o g 2}{15}

α = 0.1

M

(α - x) = 0.025

M

for first order:

k = \frac{2.303 l o g}{t} (\frac{α}{α - x})

\frac{2.303 l o g 2}{15} = \frac{2.303}{t} l o g \frac{0.1}{0.025} = \frac{2.303}{t} l o g 4

\frac{2.303 l o g 2}{15} = \frac{2 \times 2.303 l o g 2}{t}

t = 30 minutes.

In a first order reaction, the concentration of the reactant, decreases from 0.8 M to 0.4 M in 15 minutes.…

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