What are the molality and mole fraction of solute in a 25.5 percent by mass aqueous solution of formic acid (HCOOH)?

(Explain how you got the answer please)

http://www.jiskha.com/display.cgi?id=1487548953

DRboB im confused on how you worked this one

To determine the molality and mole fraction of solute in a 25.5% by mass aqueous solution of formic acid (HCOOH), we need to follow these steps:

Step 1: Convert the given percentage by mass to grams of formic acid.
- The aqueous solution is 25.5% formic acid, meaning that 25.5g of formic acid is present in 100g of the solution.
- So, we have 25.5g of formic acid.

Step 2: Calculate the molality of the solution.
- Molality (m) is defined as the number of moles of solute per kilogram of solvent.
- We need to determine the moles of formic acid and the mass of water (solvent).
- The molar mass of formic acid (HCOOH) is approximately 46.02 g/mol.
- The mass of water (solvent) is equal to the mass of the solution (100g) minus the mass of formic acid (25.5g).
- Assuming the density of water is 1g/mL, the mass of water is 100g - 25.5g = 74.5g.
- Now, we can calculate the moles of formic acid: moles = mass / molar mass = 25.5g / 46.02 g/mol.
- The molality (m) is then given by: molality = moles / mass of water (in kg) = moles / (74.5g / 1000) = moles / 0.0745kg.

Step 3: Calculate the mole fraction of solute.
- Mole fraction (χ) is defined as the ratio of moles of a component to the total moles of all components in a solution.
- The mole fraction of formic acid is given by: mole fraction = moles of formic acid / total moles.
- We already have the moles of formic acid, obtained in Step 2.
- The total moles can be calculated using the Ideal Solution Law: total moles = moles of formic acid + moles of water.
- The moles of water can be determined by dividing the mass of water by the molar mass of water (18.015 g/mol).
- The total moles = moles of formic acid + (mass of water / molar mass of water).

By following these steps, you should be able to calculate the molality and mole fraction of the solute in the given solution.