To calculate the volume of a 3 g sample of CaCl2, we first need to determine the molar mass of CaCl2.

The molar mass of CaCl2 is:
Ca - 40.08 g/mol
Cl - 35.45 g/mol

Molar mass of CaCl2 = 40.08 + 2(35.45) = 110.98 g/mol

Now we can use the given mass of 3 g and the molar mass of CaCl2 to calculate the number of moles of CaCl2:

Number of moles = mass / molar mass
Number of moles = 3 g / 110.98 g/mol = 0.027 moles

Finally, we can use the definition of molarity to determine the volume of the solution:

Molarity = moles / volume of solution
3 M = 0.027 / V
V = 0.027 / 3 = 0.009 L

Therefore, the volume of the 3 g sample of CaCl2 is 0.009 L (9 mL).