Answer:The mole is important because it allows chemists to work with the subatomic world with macro world units and amounts. Atoms, molecules and formula units are very small and very difficult to work with usually. However, the mole allows a chemist to work with amounts large enough to use.
Explanation:
Answer:
Two Half-lives
Explanation:
Let number of Parent nuclei Initially present be X,
Then, finally
Parent nuclei Will remain with
daughter nuclei.
In one half- life , parent nuclei becomes half of initial.
So, starting with X parent nuclei,
After one half-life, it will degrade to
.
After another half life , Parent nuclei will become half of
Which is equal to
.
So, Parent nuclei have to go through Two half-lives.
<u>Answer:</u> The molar solubility of
is 
<u>Explanation:</u>
Solubility is defined as the maximum amount of solute that can be dissolved in a solvent at equilibrium.
Solubility product is defined as the product of concentration of ions present in a solution each raised to the power its stoichiometric ratio.
The balanced equilibrium reaction for the ionization of calcium fluoride follows:

s 2s
The expression for solubility constant for this reaction will be:
![K_{sp}=[Pb^{2+}][I^-]^2](https://tex.z-dn.net/?f=K_%7Bsp%7D%3D%5BPb%5E%7B2%2B%7D%5D%5BI%5E-%5D%5E2)
We are given:

Putting values in above equation, we get:

Hence, the molar solubility of
is 
Answer:
C
Explanation:
Large chlorine atoms can not fit within the atoms of boron
Answer is B. Releases heat and is exothermic