Answer:
True.
Explanation:
An exothermic reaction has a positive enthalpy (heat) of reaction. However, it can be negative in some circumstances.
Sodium-25 after 3 minutes : 1.0625 mg
<h3>Further explanation</h3>
General formulas used in decay:

T = duration of decay
t 1/2 = half-life
N₀ = the number of initial radioactive atoms
Nt = the number of radioactive atoms left after decaying during T time
<h3 />
No=8 mg
t1/2=60 s
T=3 min=180 s

I think you forgot to give the choices along with your question. I am answering the question based on my research and knowledge. "Helium effuses 0.71 times faster than hydrogen" is the statement that <span>holds true when the molar mass of hydrogen is 2.0 grams and that of helium is 4.0 grams. I hope the answer has helped you.</span>