Chem question! urgent please help!?

The answer is 0.3L. To do this you need to use Stoichiometry. Since there are 2 acetate ions (CH3COO) for every calcium acetate molecule, all you have to do is multiply 0.300 mol CH300 by a molar conversion between the ion and the molecule (1 mol Ca(CH3COO)2 / 2 mol CH3COO) and then multiply by the concentration of calcium acetate (1L / 0.500 mol). This is the same as dividing 0.3 by 2 and then multiplying it by 2.