To solve this problem, let us first calculate for the rate
constant k using the half life formula:
t1/2 = ln 2 / k
where t1/2 = half life period = 24,000 years, therefore k
is:
k = ln 2 / 24,000
k = 2.89 x 10^-5 / yr
Now we use the rate equation:
A = Ao e^(-k t)
where,
A = mass of Plutonium-239 after number of years
Ao = initial mass of Plutonium-239
t = number of years
A. t = 12,000 years, find A
A = 100g e^(- 2.89 x 10^-5 * 12,000)
A = 70.7 g
B. t = 24,000 years, find A
A = 100g e^(- 2.89 x 10^-5 * 24,000)
A = 50 g
C. t = 96,000 years, find A
A = 100g e^(- 2.89 x 10^-5 * 96,000)
<span>A = 6.24 g</span>
Answer:

Explanation:
<u>Convert Atoms to Moles</u>
The first step is to convert atoms to moles. 1 mole of every substance has the same number of particles: 6.022 ×10²³ or Avogadro's Number. The type of particle can be different, in this case it is atoms of silver. Let's create a ratio using this information.

We are trying to find the mass of 8.23 ×10²³ silver atoms, so we multiply by that number.

Flip the ratio so the atoms of silver cancel. The ratio is equivalent, but places the other value with units "atoms Ag" in the denominator.


Condense into one fraction.


<u>Convert Moles to Grams</u>
The next step is to convert the moles to grams. This uses the molar mass, which is equivalent to the atomic mass on the Periodic Table, but the units are grams per mole.
Let's make another ratio using this information.

Multiply by the number of moles we calculated.

The moles of silver cancel out.



<u>Round</u>
The original measurement of atoms has 3 significant figures, so our answer must have the same. For the number we calculated, that is the ones place.
The 4 in the tenths place tells us to leave the 7 in the ones place.

8.23 ×10²³ silver atoms are equal to approximately <u>147 grams.</u>
The excretory system<span> is responsible for removing the </span>cellular waste through the lungs,skin,and kidneys<span>. </span>
1.00
Explanation:
the density of water is always 1
The population tha increases the amount of soil nutrients available to plants is D) bees that help spread pollen from one plant to another.