Radioactive decay can be described by the following equation in a = in a_0 -kt where a_0 is the original amount of the substance, a is the amount of the substance remaining after time t, and k is a constant that is characteristic of the substance. for the radioactive isotope lead -214, k is 2.59 times 10^-2 minutes^-1 if the original amount of lead - 214 in a sample is 25.9 mg, how much lead-214 remains after 29.7 minutes have passed?

The amount of lead-214 remaining after given time is 12 mg.

Explanation:

The equation used to calculate the amount of sample for first order kinetics follows:

where,

= initial mass of isotope = 25.9 mg

N = mass of the isotope left after the time = ? mg

t = time = 29.7 min

k = rate constant =

Putting values in above equation, we get:

Hence, the amount of lead-214 remaining after given time is 12 mg.

c. heat could easily travel through the molecules in the air and escape/enter the flask. removing the air slows down the heat transfer.  

i'm pretty sure it is letter c.) car