The answer is D. A compound
Answer:
The answer is B an open system allows energy and mass to move in and out of it
Hope it helps
Radioactive material obeys 1st order decay kinetics,
For 1st order reaction, we have
k =

where, k = rate constant of reaction
Given: Initial conc. 100, Final conc. = 6.25, t = 18.9 hours
∴ k =

= 0.1467 hours^(-1)
Now, for 1st order reactions: half life =

= 4.723 hours.
Answer:
b
Explanation:
atom combine to form molecules to attain stable configuration
2. <span>1/8 = (1/2)³ </span>
<span>so it's 3 half lives.</span>