Final answer:
Without the half-life of iron-53, it is inferred that the correct answer is the original mass of 5.6 grams if we assume no decay due to the absence of enough time.
Step-by-step explanation:
The question involves a nuclear decay problem where we need to determine the mass of iron-53 remaining after 25.23 minutes. Given that iron-53 has a half-life, the mass remaining after a certain time period can be determined by repeatedly halving the initial mass for each half-life that has passed.
However, the half-life of iron-53 is not provided in the question, so we cannot calculate the mass remaining based solely on the information given.
If we presume that 25.23 minutes is less than one half-life of iron-53 (which is typically true for relatively stable isotopes), then in this particular scenario, we can infer that the mass of the iron-53 that remains unchanged should be equal to the initial mass, that is, 5.6 grams.