How many moles of CaCl2 are in 250mL of a 3.0M of CaCl2 solution?
Since the problem provides the amount in liters of CaCl2 solutions, then 3.0M expresses the molarity of solution, hence you need to use the molarity formula such that:
M = (number of moles of CaCl2 solution)/(volume of CaCl2 in liters)
You need to convert the amount of 250 mL in liters such that:
250mL = 250*10^(-3)L
Substituting 3 for M and 250*10^(-3)L for V yields:
3 = N/(0.250) => N = 3*0.250
N = 0.75
Hence, evaluating the number of moles in 250mL of CaCl2 solution yields 0.75 moles.
3.0 M = 3moles/1liter
250mL= 0.25 L
so, 3mol/1L= (?)mol/.25L
there are 0.75 moles of CaCl2 in 250 mL of a 3.0 molar solution