Question

Half life period of a radioactive substance is 20 days .After 30 days what percentage of the substance will be left?

This is the questions of class 12 Chemistry - Kinetics
Please answer using the chemistry formula

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Answer 1

Answer:

35.35 % of the substance is left

Explanation:

We Have :-

Half life period of a radioactive substance is 20 days

To Find :-

After 30 days what percentage of the substance will be left

Solution :-

$t_{\frac{1}{2} } = \frac{ln2}{k} \\\\k = \frac{ln2}{t_{\frac{1}{2} } } \\\\k = \frac{ln2}{20} \\\\Given\\\\ln\frac{N_{o} }{N_{t}} = \frac{ln2}{20} *30\\\\ln\frac{N_{o} }{N_{t}} = \frac{3ln2}{2} \\\\\ln\frac{N_{o} }{N_{t}} = ln ( \sqrt{2})^{3} \\\\\frac{N_{t} }{N_{o}} = \frac{1}{(\sqrt{2})^{3} } \\\\N_{t} = \frac{N_{o}}{(\sqrt{2})^{3} } \\\\\\% = \frac{N_{t}}{N_{o}}*100 \\\\% = \frac{1}{2\sqrt{2} }*100$

$Percentage = \frac{N_{t}}{N_{o}}*100 \\\\Percentage = \frac{1}{2\sqrt{2} }*100\\\\= 25\sqrt{2} \\\\=25 * 1.414\\\\\approx 35.35 \%$

35.35 % of the substance is left

Answer 2

Answer:

25√2

35.5 % Left

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