The balanced equation of the given reaction is
XCl4 + 2NH3 ---------> XCl2(NH3)2
The number of moles of the XCl4 present initially = The number of moles of XCl2(NH3)2
Since number of moles = weight/M.Weight
Therefore
(Weight/M.Wt) of reactants = (Weight/M.Wt) of products
Weight of reactants/Weight of Products = M.Wt of reactants/ M.Wt of products
3.571g/3.180g = M.Wt(rea) / M.Wt(pro)
1.122 = M.Wt(rea) / M.Wt(pro)
Therefore Molecular weight of reactants = 1.122(M.Wt of products)
[xg + 4(35.45g/mol for Cl) ] = 1.122[xg+2(35.45g/mol for Cl) + 2(17g/mol for NH3)]
By solving this equation we get the value of x,that is the molecular weight of X.
Therefore x = 194.36g/mol
This is the M.Wt of the Platinum,Pt.
Therefore un known X = Pt.