In the following diagrams, A represents a radioactive isotope that decays into a new isotope, X. Each circle represents 1 mmol of atoms. t = 0: t = 25.0 s: Which diagram best represents the sample at t = 50.0 s?

Question

In the following diagrams, A represents a radioactive isotope that decays into a new isotope, X. Each circle represents 1 mmol of atoms. t = 0:  t = 25.0 s:  Which diagram best represents the sample at t = 50.0 s?

Quizplus · Accepted Answer

At t=25.0 s, half of the sample has decayed into the new isotope X, leaving 0.5 mmol of A and 0.5 mmol of X. At t=50.0 s, another half of the remaining A will decay, leaving only 0.25 mmol of A and 0.75 mmol of X. The only diagram that represents this ratio of A to X is option C.

In the Following Diagrams, a Represents a Radioactive Isotope That