The partial pressure of water above a solution of water and a nonvolatile solute at 25oC is 19.2 mm Hg. What is the mole fraction of the solute
please help....I really don't know how I am supposed to solve this question.
I know that Partial pressure of the solvent above a soln = (mole fraction of solvent)(Vapor pressure above the pure solvent)
Are you allowed to look up information OR do you have the normal vapor pressure of water at 25 degrees C in the problem?
Po H2O @ 25 degres C = 23.8 mm I believe but check me out on that. If it's listed in the problem use that value.
Then delta P = X(solute)*P(solvent)
delta P then is 23.8-19.2 = X(solute)*23.8 and you solve for X(solute).
To solve this problem, you need to use Raoult's Law, which states that the vapor pressure of a component in a solution is directly proportional to its mole fraction in the solution.
Here's how you can approach this problem step-by-step:
1. Identify the given information:
- The partial pressure of water above the solution: 19.2 mm Hg
- The temperature: 25°C
2. Find the vapor pressure of pure water at 25°C:
You can look up the vapor pressure of water at 25°C (also known as its saturation vapor pressure) in a table or use a reference. The vapor pressure of water at 25°C is approximately 23.8 mm Hg.
3. Apply Raoult's Law:
According to Raoult's Law, the partial pressure of a component in a solution is equal to the mole fraction of that component multiplied by its vapor pressure in the pure state.
Let's assume that the mole fraction of the solute is represented by "x." The mole fraction of the solvent (water) is then given by (1 - x).
Using the given information, we can set up the equation:
Partial pressure of water = (mole fraction of water)(vapor pressure of water)
19.2 mm Hg = (1 - x) * (23.8 mm Hg)
4. Solve for the mole fraction of the solute:
Rearrange the equation and solve for "x":
(1 - x) = (19.2 mm Hg) / (23.8 mm Hg)
x = 1 - (19.2 mm Hg) / (23.8 mm Hg)
Calculate the value of "x" to find the mole fraction of the solute.
By following these steps, you can determine the mole fraction of the solute in the solution.