posted by John on .
A metal, M, of atomic mass 91 amu reacts with fluorine to form a salt that can be represented as MFx. In order to determine x and therefore the formula of the salt, a boiling point elevation experiment is performed. A 9.05-g sample of the salt is dissolved in 100.0 g of water and the boiling point of the solution is found to be 374.54 K. Find the formula of the salt. Assume complete dissociation of the salt in solution.
Formula is MFx so molar mass is 91+19x
delta T = i*Kb*m and
m = mols/kg solvent and
mols = g/molar mass
374.54-273.15 = 1.39 = delta T.
mols 9.05/molar mass
m = 9.05/(91+19x)/0.1
i = 1 for M + x for F
Solve for x. My answer comes out 3.955 which rounds to 4 so I would think MF4 is the formula and the molar mass is 167. Check my work carefully because I don't see a metal that fits this MF4 category.