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Standard XII

Chemistry

Half and Average Life

Two radioacti...

Question

Two radioactive element A and B have half - lives in the ratio of 1 : 2. If half - life A is 2 days, what will be the mole ratio of A to B after 12 days in a sample initially containing 1 mole of each ?

1 : 2

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1 : 4

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1 : 6

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1 : 8

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Solution

The correct option is D
1 : 8

Number of $t_{\frac{1}{2} (A)} = \frac{12}{2} = 6 :$
Number of $t_{\frac{1}{2} (B)} = \frac{12}{4} = 3$
$n_{A} l e f t = (\frac{1}{2})^{6} = \frac{1}{64}; n_{B} l e f t = (\frac{1}{2})^{3} = \frac{1}{8}$
$n_{A} : n_{B} = \frac{1}{64} : \frac{1}{8} = 1 : 8$

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Two radioactive element A and B have half - lives in the ratio of 1 : 2. If half - life A is 2 days, what will be the mole ratio of A to B after 12 days in a sample initially containing 1 mole of each ?

The correct option is D 1 : 8 Number of t12(A)=122=6: Number of t12(B)=124=3 nA left=(12)6=164;nB left=(12)3=18 nA:nB=164:18=1:8

The correct option is D
1 : 8

Number of $t_{\frac{1}{2} (A)} = \frac{12}{2} = 6 :$
Number of $t_{\frac{1}{2} (B)} = \frac{12}{4} = 3$
$n_{A} l e f t = (\frac{1}{2})^{6} = \frac{1}{64}; n_{B} l e f t = (\frac{1}{2})^{3} = \frac{1}{8}$
$n_{A} : n_{B} = \frac{1}{64} : \frac{1}{8} = 1 : 8$