Answer:
2.56 L NiCl2
Explanation:
This is a stoichiometry problem. You need to find a way to go from g of Ni3(PO4)2 to L of NiCl2. To do this you travel
mass Ni3(PO4)2 > moles Ni3(PO4)2 > moles NiCl2 > L NiCl2
so you need to know the key that lets you travel from one to the next.
Mass > moles, use molar mass
moles > moles, use the mole ratio
moles > L, use the molarity (moles / liter) in this case. (With gases, you use the STP gas volume of 22.4L / mole).
The attached picture shows what this problem looks like.