3 half-lives have occured
Further explanationGiven
Half-life Radon-222 = 3.8 days
12.5% of Rn-222 remains
Required
Half-lives occurred
Solution
General formulas used in decay:
[tex]\large{\boxed{\bold{N_t=N_0(\dfrac{1}{2})^{t/t\frac{1}{2} }}}[/tex]
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
12.5% of Rn-222 remains ⇒ Nt/No = 0.125
Input the value :
[tex]\tt 0.125=\dfrac{1}{2}^{t/3.8}\\\\\dfrac{1}{2}^3=\dfrac{1}{2}^{t/3.8}\\\\3=t/3.8\\\\t=11.4\rightarrow 3~half-lives[/tex]
PLSSS HELP. And there’s also at the bottom of the picture another option if u didn’t see it
Answer:
B. Gradualism
Explanation:
A pan containing hot water is left on the counter and becomes cool mainly due to....
A. water molecules moving apart.
B. cold air penetrating the hot water.
C. heat from the water moving into the cooler air.
D. hot water reacting with the metal pan.
Answer:
C. heat from the water moving through the cooler air
I think it's C because when something cools down, it has to reach a point of thermal equilibrium with the matter (in this case air) around it. So heat transfer happens through convection from the heat in the pan to the cooler surrounding air. The heated air becomes less dense and rises, while cooler air, sinks to the surface of the water, gets heated, and rises. This convection cycle keeps happening until the water in the pan is around the same temperature with the air around it.
