Calculate the molar mass of a molecular compound if a solution of 6.70 g of the compound in 22.60 g of water boils at 100.78 degrees C (at 760mmHg).
You must assume this is a non-volatile compounds AND that it is not ionic.
delta T = 100.78-100 = ?
delta T = Kb*molality
You know delta T, look up Kb (about 0.5), solve for m.
m = mols/kg solvent. You kow m and kg waterk solve for mols.
mol = grams/molar mass You know grams and mol solve for molar mass.
To calculate the molar mass of a molecular compound, we need to follow a few steps:
Step 1: Determine the number of moles of the compound present in the solution.
We can use the formula:
Moles = Mass / Molar mass
In this case, the mass of the compound is given as 6.70 g. However, we need to convert the mass of water to moles as well, as it affects the boiling point of the solution. To do this, we use the formula:
Moles of water = Mass of water / Molar mass of water
Looking up the molar mass of water, we find that it is approximately 18.015 g/mol. Therefore:
Moles of water = 22.60 g / 18.015 g/mol ≈ 1.253 mol (rounded to three decimal places)
Now, let's go back to the compound in the solution. From the equation:
Moles = Mass / Molar mass
we can rearrange to solve for the molar mass:
Molar mass = Mass / Moles
Plugging in the given values:
Molar mass = 6.70 g / 1.253 mol ≈ 5.348 g/mol (rounded to three decimal places)
The molar mass of the molecular compound is approximately 5.348 g/mol.