Sorbitol is a sweet substance found in fruits and berries and someties used as a sugar substiture. An aqueous solution containin 1g of sorbitol in 100g water has a freezing point of 0.102C. Elemental analysis indicates that sorbitol is 39.56%C, 7.75%H, and 52.7O. What are the molar mass and molecular formula of sorbitorl? The Kf of water is 1.86C/m

I answered this question yesterday for someone but I can't find the answer to copy it. Here is what you do; however, let me point out that I think you have a typo in the problem. I'm sure the freezing point is -0.102 and not +0.102.

There are two problems here.
A. Problem #1.
1. Use delta T = Kf*molality. You have delta T and Kf, solve for molality.
2. Use molality = # mols/kg solvent to calculate mols.
3. Use mols = g/molar mass to solve for molar mass since you have mols and grams.
B. Problem #2.
Then take a 100 g sample which will give you 39.56 g C, 7.75 g H and 52.70 g O.
Convert those grams to mols, then determine the ratio of C, H, and O in small whole numbers. This will give you the empirical formula.

Finally, divide the molar mass by the empirical formula mass to determine the number of units of the empirical formula that makes up the molecular formula.

Post your work if you get stuck.

It is spelled Chemistry. I would learn to spell that before you go much further.

Assume 100 grams of the stuff to get a formula.

then you have 39.56g C, and so on with H and O.

Figure the moles of C, H, and O from that. Divide by the lowest moles of all the element, in order to get a ratio of C H O. The ratio for the lowest element will be 1, or course. You will get some numbers that will look like this
C3H4O2 or some such numbers from the ratios. That is the empirical formula. If you don't follow this explaination, go here:
http://home.c2i.net/astandne/help_htm/english/example/empirical-formula.htm

Now to get mole mass, use the molatity

I assume the freezing point is -.102C, not what you listed.
-.102=-1.86m
solve for m molality.
Then, 1g/molmass /.100 = m and you can solve for mole mass.

Now you have the true molmass, and the empirical formula. Figure the molmass of the empirical formula, divide it into the true mole mass. You should get a whole number, which tells you how much each of the coefficents on the empirical should be increased.

Asking

Answer

To find the molar mass and molecular formula of sorbitol, we will use the freezing point depression equation:

ΔT = Kf * m * i

Where:
- ΔT is the freezing point depression
- Kf is the freezing point depression constant (1.86°C/m for water)
- m is the molality of the solution (moles of solute per kg of solvent)
- i is the van't Hoff factor (the number of particles the solute dissociates into in solution)

First, let's calculate the molality of the solution:

m = (moles of solute) / (mass of solvent in kg)

Since we have 1g of sorbitol in 100g of water, we have:
mass of sorbitol = 1g = 0.001kg
mass of water = 100g = 0.1kg

m = (0.001 mol) / (0.1 kg) = 0.01 mol/kg

Now, let's calculate the freezing point depression:

ΔT = Kf * m * i

We know that the freezing point depression (ΔT) is 0.102°C and the Kf for water is 1.86°C/m. Since sorbitol does not dissociate or ionize in water, i = 1.

0.102 = 1.86 * 0.01 * 1
0.102 = 0.0186

To solve for the moles of solute (sorbitol), divide both sides of the equation by Kf:

mol = ΔT / (Kf * m)
mol = 0.102 / (1.86 * 0.01)
mol = 5.48

Now, let's calculate the molar mass of sorbitol:

Molar mass = Mass / Moles

To find the mass of sorbitol, we need to calculate the mass of carbon, hydrogen, and oxygen in the compound based on the given percentages:

mass of carbon = 39.56g (since the percentage is given out of 100g)
mass of hydrogen = 7.75g
mass of oxygen = 52.7g

Now, calculate the moles of carbon, hydrogen, and oxygen:

moles of carbon = mass of carbon / molar mass of carbon
moles of hydrogen = mass of hydrogen / molar mass of hydrogen
moles of oxygen = mass of oxygen / molar mass of oxygen

To calculate the molar mass of sorbitol, add up the molar masses of carbon, hydrogen, and oxygen:

molar mass of sorbitol = (moles of carbon * molar mass of carbon) + (moles of hydrogen * molar mass of hydrogen) + (moles of oxygen * molar mass of oxygen)

By using the periodic table, the molar masses are:
molar mass of carbon = 12.01 g/mol
molar mass of hydrogen = 1.01 g/mol
molar mass of oxygen = 16.00 g/mol

Substituting the values, we have:

molar mass of sorbitol = (moles of carbon * 12.01) + (moles of hydrogen * 1.01) + (moles of oxygen * 16.00)

Finally, divide the molar mass by the number of moles previously calculated:

Molecular formula = (molar mass of sorbitol) / (number of moles)

With these calculations, you should be able to determine the molar mass and molecular formula of sorbitol.