Answer: 208g/mol
Step-by-step explanation:
First of all we have to write the balance equation for the reaction. 
BaCl2 + Fe2(SO4)3____> BaSO4 + FeCl3
After balancing we have. 
3BaCl2 +Fe2(SO4)3_____> 3BaSO4 +2FeCl3
Looking at the equation, we find out that 3 moles of barium chloride reacts with 1 mole of iron iii sulfate
Therefore we have 
3moles of BaCl2 _____> 400g/mole of iron iii sulfate 
Xmole of BaCl2 _____> 200g/mole of iron iii sulfate 
X = 2 * 200g/mol divide by 400g/mol
X = 1mole
 1 mole of BaCl2 will be need to react with 200g/mol of iron iii sulfate. 
This 1 mole of BaCl2 is equivalent to 208g/mol of BaCl2.
Therefore the gram of barium chloride that must be present is = 208g/mol//