Question

calculate the value of water that is needed to dissolve 1.11 g of CaCl2 in order to prepare a 0.0250 M CaCl2 solution?

Answer 1

Remember the definitions.
Molarity = # mols/L.
and # mols = g/molar mass.
How many moles CaCl2 do you have in 11.1 g CaCl2. That will be 11.1 g CaCl2/molar mass CaCl2.
Then #mols = M x L.
You have M and you have mols, calculate L.

Answer 2

The procedure suggested by DrBob 222 will give the correct answer to the question. However, the wording of the <b>question</b> itself could be improved. It might be:
<i>"Calculate the <b>total volume of solution</b> (water + CaCl2) when a 0.0250 M CaCl2 solution is prepared by dissolving 1.11 g of CaCl2 in a small volume of water and diluting to the calculated volume."</i>.
The amount of water added cannot be calculated with complete precision since the volume of the solution includes both, water and calcium chloride.

Answer 3

GK is correct; the problem could have been worded more correctly. I assumed you were asking for the solution. Also, I note that I made an error in typing. It isn't 11.1 g CaCl2 but 1.11 g CaCl2.