Assertion : Half life of a radioactive isotope is the time required to decrease its mass number by half.
Reason : Half life of radioactive isotopes is independent of the initial amount of the isotope.

If both (A) and (R) are correct, and (R) is the correct explanation of (A).

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If both (A) and (R) are correct, but (R) is not the correct explanation of (A).

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If (A) is correct, but (R) is incorrect.

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If (A) is incorrect, but (R) is correct.

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If both (A) and (R) are incorrect.

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Solution

The correct option is D If (A) is incorrect, but (R) is correct.
Half life is the time period required to decrease the initial number of atoms or amount of radioactive substance to half. Hence, the assertion is incorrect.

As radioactivity is a first order process, the half life is independent of the starting amount. So, reason is correct.

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Similar questions

Q. Assertion :Half life of a radioactive isotope is the time required to decrease its mass number by half. Reason: Half life of radioactive isotopes is independent of initial amount of the isotope.

Assertion (A) Order and molecularity are same.

Reason (R) Order is determined experimentally and molecularity is the sum of the stoichimetric coeffcient of rate determining elementary step.

(a) Both assertion and reason are correct and the reason is correct explanation of assertion
(b) Both assertion and reason are correct, but reason does not explain assertion.
(c) Assertion is correct, but reason is incorrect
(d) Both assertion and reason are incorrect
(e) Assertion is incorrect but reason is correct.

Assertion (A) Order of the reaction can be zero or fractional.

Reason (R) We cannot determine order from balanced chemical equation.

Assertion: The sides of a triangle are 3cm, 4cm and 5cm. Its area is $6 c m^{2}$

Reason: If 2s = (a + b + c), where a, b, c are the sides of a triangle, then area

$= \sqrt{(s - a) (s - b) (s - c)}$

Which of the following is correct?

Assertion (A) The enthalpy of reaction remains constant in the presence of a catalyst.

Reason (R) A catalyst participating in the reaction forms different activated complex and lowers down the activation energy but the difference in enrgy of reactant and product remains the same.

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Assertion : Half life of a radioactive isotope is the time required to decrease its mass number by half.Reason : Half life of radioactive isotopes is independent of the initial amount of the isotope.

Assertion : Half life of a radioactive isotope is the time required to decrease its mass number by half.
Reason : Half life of radioactive isotopes is independent of the initial amount of the isotope.