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

1st level = s
<span>2nd level = s,p </span>
<span>3rd level = s,p,d </span>
<span>4th level = s,p,d,f</span>
Answer:
How can I tell if a chemical reaction is occurring? A chemical reaction is usually accompanied by easily observed physical effects, such as the emission of heat and light, the formation of a precipitate, the evolution of gas, or a color change.
Explanation:
Animals contribute water mainly through breathing, perspiration and urination. ... When droplets of sweat evaporate from the surface of an animal's skin, they take a bit of the animal's body heat with them. They also turn into water vapor and enter the water cycle, just like water evaporating from plant leaves.
Answer:
The answer is
<h2>91.9 g</h2>
Explanation:
The mass of a substance when given the density and volume can be found by using the formula
<h3>mass = Density × volume</h3>
From the question
volume of copper = 10.3 mL
density = 8.92 g/mL
The mass is
mass = 8.92 × 10.3 = 91.876
We have the final answer as
<h3>91.9 g</h3>
Hope this helps you