Molarity = number of mole of substance(n) / volume of solution (V).
n(CaCl2) = mass (CaCl2)/M(CaCl2)
M(CaCl2) = 40+2*35.5 = 111 g/mol
n(CaCl2) =39.5 g CaCl2*1 mol/111g
0.250 M = 39.5 g CaCl2*1 mol/111g*volume of solution (V).
volume of solution (V) = 39.5 g CaCl2*1 mol/(0.250 M*111g) = 1.42 L
Answer:


Explanation:
<u>Calculation of the mass of chromium as:-
</u>
Moles = 1.002 moles
Molar mass of chromium = 51.9961 g/mol
The formula for the calculation of moles is shown below:
Thus,

<u>Calculation of the mass of neon as:-
</u>
Moles =
moles
Molar mass of neon = 20.1797 g/mol
Thus,

First you should know that there is seven oxygen atoms in one Mn2O7
So
2.00 moles of Mn2O7 contain 14.00 moles of oxygen...
Then you multiply this no. with Avagadro no....
from formula
Number of moles= no. of particles/avagadro's no..
14.00×6.02×10²³=84.28 atoms of oxygen...