[kirk]

What formulas would I use for this question?    A solution is found to contain 0.010 moles of Ca per liter. If you are using 25.00ml of this solution dilutes to 100.0ml, what is the concentration of Ca in this new solution?

[lemonoman]

You are given:

C₁ - initial concentration
V₁ - initial volume
V₂ - final volume

and are asked to find

C₂ - final concentration

Hope this helps!

Hint: The AMOUNT (n, in moles) will be the same in both the initial and final solutions.  No Ca is being added or removed....it's just being diluted.