Radio waves is the lowest frequency
Answer:
O
Explanation:
The top number always represents the mass number.
The bottom number always represents the atomic number.
The element always goes after the numbers.
If charge is present, that comes after the element.
78.78 g out of 250 g of Thorium-234 would remain after 40 days.
Explanation:
All radioactive samples are unstable in nature and so they will be decaying with time. So the equation of disintegration of the radioactive element is given as
![N=N_{0}e^{-kt}](https://tex.z-dn.net/?f=N%3DN_%7B0%7De%5E%7B-kt%7D)
So N is the mass of the radioactive element at time t and
is the mass of the radioactive element at initial stage. Here k is the disintegration constant and t is the time.
We can determine the disintegration constant from the half life term of any element.
![Half life = \frac{0.693}{k}](https://tex.z-dn.net/?f=Half%20life%20%3D%20%5Cfrac%7B0.693%7D%7Bk%7D)
So, ![k = \frac{0.693}{Half life}](https://tex.z-dn.net/?f=k%20%3D%20%5Cfrac%7B0.693%7D%7BHalf%20life%7D)
Since, the half life time of thorium-234 is known to be 24 days. Then, the disintegration constant is
![days^{-1}](https://tex.z-dn.net/?f=days%5E%7B-1%7D)
As the given questions have the initial mass
as 250 g and t is given as 40 days, then the mass after 40 days will be
![N = 250 * e^{-0.02887*40}= 250 * e^{-1.1548}=78.78 g.](https://tex.z-dn.net/?f=N%20%3D%20250%20%2A%20e%5E%7B-0.02887%2A40%7D%3D%20250%20%2A%20e%5E%7B-1.1548%7D%3D78.78%20g.)
Thus, 78.78 g of thorium-234 would remain after 40 days.
Answer:
The key to chemistry is to change everything to moles. Then when you have the answer in moles change the answer back to grams, liters, or whatever you want.
change 25 grams of potassium chlorate to moles.
calculate the gram molecular mass of potassium chlorate.
Chlorate is Cl with 3 oxygens. ate = saturated. Chlorine has seven valance electrons when it is saturated six of these electrons are used by oxygen ( 2 electrons per oxygen) leaving only 1 electron.
1 K x 39 grams/mole
+1 Cl x 35.4 grams/ mole
+3 O x 16 grams/ mole
= 122.4 grams / mole Potassium Chlorate
25
122.4
= moles.
2.05 moles of Potassium Chlorate.
There is a 1:1 mole ratio. 1 mole of Potassium Chlorate will produce 1 mole of Potassium Chloride.
2.05 moles of Potassium Chlorate will produce 2.05 moles of Potassium Chloride.
Find the gram molecular mass of Potassium Chloride.
1 K x 39 = 39
+1 Cl x 35.4 = 35.4
= 74.4 grams / mole.
2.05 moles x 74.4 grams/ mole = 15.2 grams
Explanation:
hope this helped :)