Explanation:
1) Initial mass of the Cesium-137=
= 180 mg
Mass of Cesium after time t = N
Formula used :
Half life of the cesium-137 =
= initial mass of isotope
N = mass of the parent isotope left after the time, (t)
= half life of the isotope
= rate constant

Now put all the given values in this formula, we get
Mass that remains after t years.

Therefore, the parent isotope remain after one half life will be, 100 grams.
2)
t = 70 years


N = 35.73 mg
35.73 mg of cesium-137 will remain after 70 years.
3)


N = 1 mg
t = ?

t = 224.80 years ≈ 225 years
After 225 years only 1 mg of cesium-137 will remain.
Answer:
18 * 10^19 atoms
Explanation:
We must first convert 57.8 mg to grams.
If 1000 mg = 1g
57.8 mg = 57.8/1000 = 57.8 * 10^-3 g
Now;
If 1 gold atom has a mass of 3.27X10^-22 grams
x gold atoms have a mass of 57.8 * 10^-3 g
x = 57.8 * 10^-3 g/3.27X10^-22 g
x = 18 * 10^19 atoms
The answer is wedge to your answer
This is the same as its freezing point
hope this helps