Density= mass/volume
step one :
convert m3 to ml
1m^3 =1000000ml
0.250m^3 x1000000=250000ml
step two: convert mg to g
1mg=0.001g, therefore 4.25 x108mg=0.459g
density is therefore= 0.459g/250000=1.836 x10^-6g/ml
One thing that does not change is the chemical composition of water, which is still H2O. And maybe mass, if all of the particles remain inside the beaker, which was never mentioned in the question so I am not sure.
When an electron absorbs energy, it will move up from a lower energy level to a higher energy level, called the "excited state" of the negatively-charged subatomic particle.<span> However, the absorbed energy is released within a small interval of time and the electron moves down to its "ground state."</span>
Answer:

Explanation:
From the question, we have been asked to find the molarity of FeCl2 having a volume of 450 mL,
We have been provided with 225 g which is proportional to 1.8 moles.
We know that molarity of any solution should be in mol/L.
1 mole contained in 1 L means it has a molarity of 1 mol/L
Let's convert 450 mL to Litres which is,

= 0.450 L
Thus,
1 mole is contained in 1L
x moles are contained in 0.450 L
Hence,
x mole/molarity = {1 mole x 1 L}/{0.450 L}
= 4 mol/L
Therefore 4 mol/L is the molar concentration.