NEET Chemistry Chemical Kinetics MCQs

Two radioactive isotopes, X and Y, have half-lives of $T_X$ and $T_Y$ respectively, where $T_X = 2T_Y$. Initially, the activity of X is four times the activity of Y. At what time $t$ will their activities be equal?

A radioactive element A decays into a stable element B with a half-life of $T_A$. Element B, in turn, decays into another stable element C with a half-life of $T_B$. If initially, only element A is present, at what time will the amount of element B be maximum?

The half-life of a radioactive substance is 10 days. After how many days will its activity reduce to less than 1% of its original activity?

A sample initially contains 1000 nuclei of a radioactive isotope with a half-life of 5 hours. After 20 hours, the sample is contaminated with 500 nuclei of a stable isotope of the same element. What is the ratio of radioactive nuclei to the total number of nuclei in the sample after 20 hours?

Element X decays into Y with a half-life of $T_1$, and Y decays into Z with a half-life of $T_2$. If $T_1 >> T_2$, which of the following is TRUE regarding the activity of Y after a long time ($t >> T_2$)?

A radioactive sample has a half-life of 10 days. What fraction of the original sample will remain after 30 days?

The half-life of a radioactive isotope is 5 years. If the initial activity is 1000 counts per minute, what will be the activity after 15 years?

A radioactive element X decays to Y with a half-life of 20 minutes. If you start with 1 gram of X, how much Y will be formed after 40 minutes?

Which of the following factors affects the half-life of a radioactive substance?

After 2 half-lives, what percentage of a radioactive sample remains?