GENERAL KNOWLEDGE

Detailed explanation-1: -Answer: Option C Solution: The half life period of an isotope is 2 hours. After 6 hours 1/8 of the original amount, or 12.5% of the isotope will be left behind.

Detailed explanation-2: -As an example, iodine-131 is a radioisotope with a half-life of 8 days. It decays by beta particle emission into xenon-131. After eight days have passed, half of the atoms of any sample of iodine-131 will have decayed, and the sample will now be 50% iodine-131 and 50% xenon-131.

Detailed explanation-3: -The half-life of a first-order reaction is a constant that is related to the rate constant for the reaction: t 1/2 = 0.693/k. Radioactive decay reactions are first-order reactions. The rate of decay, or activity, of a sample of a radioactive substance is the decrease in the number of radioactive nuclei per unit time.

Detailed explanation-4: -The half-life of a radioactive isotope is the amount of time it takes for one-half of the radioactive isotope to decay. The half-life of a specific radioactive isotope is constant; it is unaffected by conditions and is independent of the initial amount of that isotope.

Detailed explanation-5: -Answer and Explanation: The isotope with the longest known half-life is tellurium-128, with a half-life of 2.2 septillion years.