# How to Determine Mole Fraction and Mass Percent from Osmotic Pressure Data?

• Mia Vel
In summary, the question asks for the mole fraction and mass percent composition of a mixture containing 15% KNO3 by weight. The osmotic pressure at 25°C was given to be 1.25 atm when 0.32 weight/volume% of the mixture was dissolved in 997 g of H2O. Using the equation for osmotic pressure, the molarity of the solution was calculated. However, the next steps and the meaning of weight/volume% and weight/weight% are unclear. One suggestion was to multiply the given percentages by 100 to find the total mass of the mixture, but this is not always accurate. Further clarification is needed to continue solving the problem.
Mia Vel

## Homework Statement

When 0.32 weight/volume% of sucrose, MgSO4 and KNO3 mixture is dissolved in 997 g of H2O, the osmotic pressure at 25 deg Celsius is 1.25 atm. Calculate the mole fraction and mass percent composition of the original mixture if it contains 15% weight/weight KNO3.

2. Homework Equations

Osmotic pressure= Molarity x Gas constant x Temperature in Kelvin

## The Attempt at a Solution

I was able to solve for the molarity of the solution. After it, I don't know what to do next. Can someone please teach me what the next step is and what is the role(meaning) of weight/volume % and weight/weight % in the problem? Thank you in advance. :)

Mia Vel said:
When 0.32 weight/volume% of sucrose, MgSO4 and KNO3 mixture is dissolved

I have no idea what it means.

My friend told me that when you multiply the given percentage by 100, you will get the total mass of the mixture. I am just not sure whether I should believe him or not.

Mia Vel said:
My friend told me that when you multiply the given percentage by 100, you will get the total mass of the mixture.

Doesn't sound correct to me. 30% sulfuric acid doesn't always weight 3000 (and 3000 of what? stones? grams? ounces? pounds?).

## 1. What is osmotic pressure and how does it relate to stoichiometry?

Osmotic pressure is the pressure required to prevent the flow of water across a semipermeable membrane. In stoichiometry, it is used to calculate the number of moles of a solute in a solution based on the concentration and volume of the solution.

## 2. How is osmotic pressure measured?

Osmotic pressure can be measured using an osmometer, which determines the pressure required to stop the flow of water through a semipermeable membrane.

## 3. What factors affect osmotic pressure?

The concentration of solute, temperature, and volume of the solution all affect osmotic pressure. As the concentration of solute increases, so does the osmotic pressure. Higher temperatures also increase osmotic pressure, while larger volumes decrease it.

## 4. How is stoichiometry used in osmotic pressure calculations?

Stoichiometry is used to determine the number of moles of solute in a solution, which is then used to calculate the osmotic pressure. This involves using the molar mass of the solute, the concentration of the solution, and the volume of the solution.

## 5. What is the relationship between osmotic pressure and osmolarity?

Osmolarity is a measure of the concentration of a solution, while osmotic pressure is a measure of the pressure required to prevent water flow across a membrane. Osmolarity is directly proportional to osmotic pressure, meaning that as osmolarity increases, so does osmotic pressure.

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