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.

Is the answer not MF_3??

assume it is MF3. then

bpe=.52*4*9.05/(.1*(91+3*19))
bpe=18.8/(14.8)=1.2 check that.

Is that equivalent to a new bp of 374.54K?

It is not... So where do I go from here?

You're right. It isn't MF3.

Do it this way.
delta T = i*Kb*m
If you let MFx ionize into M + xF, then
molar mass is 91+19x and
m = 90.5g/(91+19x)
Substitute delta T, for i substitute x+1, then Kb and m. Solve for x.

the answer should be ZrF4

ZrF4 is wrong.

This is an OLD question but I'm having trouble on it... *sigh*

To determine the formula of the salt, we can use the concept of boiling point elevation.

Boiling point elevation occurs when a solute is dissolved in a solvent, causing the boiling point of the solvent to increase. The change in boiling point (ΔTb) is directly proportional to the molality (m) of the solute in the solvent. The equation for boiling point elevation is given by:

ΔTb = Kbm

Where:
- ΔTb is the change in boiling point
- Kb is the molal boiling point elevation constant for the solvent
- m is the molality of the solute in the solvent

In this case, water is the solvent and the salt MFx is the solute. We are given the mass of the salt (9.05 g) and the mass of water (100.0 g). To find the molality of the salt, we need to calculate the moles of the salt and the moles of the water.

The moles of the salt (MFx) can be calculated using its mass and the molar mass:

moles of salt = mass of salt / molar mass of salt

The molar mass of the salt, M, is given as 91 amu. To convert this to grams per mole (g/mol), we use the conversion factor 1 g = 1 amu. Therefore, the molar mass of M is 91 g/mol.

moles of salt = 9.05 g / 91 g/mol

Now, we need to find the moles of water. The molar mass of water (H2O) is 18 g/mol.

moles of water = mass of water / molar mass of water

moles of water = 100.0 g / 18 g/mol

Next, we need to determine the molality of the salt (m). Molality is defined as the moles of solute per kilogram of solvent. As we have the mass of water, we need to convert it to kilograms.

mass of water in kg = mass of water / 1000

Now, we can calculate the molality:

molality = moles of salt / mass of water in kg

From the given information, we were also given the boiling point elevation (ΔTb), which is 374.54 K. Now, we can rearrange the boiling point elevation equation to solve for molality:

ΔTb = Kb * molality

Solving this equation for molality gives:

molality = ΔTb / Kb

Given the boiling point elevation constant (Kb) for water is 0.512 °C/m (or 0.512 K/m), we can plug in the values to calculate the molality.

Finally, if we know the molality of the salt (MFx), we can determine the value of x. Since the salt is assumed to completely dissociate in the solution, the moles of the salt are equal to the moles of the metal M. Hence, we can write:

moles of M = moles of salt

Knowing that the formula is MFx, we can use the molar mass of M to calculate the value of x.

molar mass of M = mass of M / moles of M

Now, with x known, we can write the formula for the salt in the given question. If x = 3, then the formula would indeed be MF₃.