To find the total mass of the reactants, we need to calculate the mass of each element in the reactants and then add them together.
FeCI3:
1 iron atom (Fe) = 56 amu
3 chlorine atoms (CI) = 3 x 35 amu = 105 amu
Total mass of FeCI3 = 56 + 105 = 161 amu
3H2O:
6 hydrogen atoms (H) = 6 x 1 amu = 6 amu
3 oxygen atoms (O) = 3 x 16 amu = 48 amu
Total mass of 3H2O = 6 + 48 = 54 amu
Total mass of the reactants = 161 amu (FeCI3) + 54 amu (3H2O) = 215 amu
Therefore, the total mass of the reactants is 215 amu. Therefore, the correct answer is b. 215.