Answer:
Earth has a magnetic force that is strongest at its core.
The products will be magnesium phosphate and potassium chloride. You then have to watch a solubility chart to see which one of these is not soluable. In this case it is magnesium phosphate.
1mole contains 22.4Lmol^-1
xmole contains 8.943
cross-multiply
x=1×8.943/22.4
x=0.40mole
there it contains 0.40moles.
P=0.0902 g/l
v=22.4 l/mol (stp)
M=vp
M=22.4 l/mol * 0.0902 g/l=2.020 g/mol
M=2.020 g/mol