at 40 degree C , the vapour pressure of water is 55.3 mm of hg. calculate the vapour pressure at same temp. of 10%aques solution of urea??

PH2O = Xsoln*PoH2O

10% urea = 10g urea/(10g urea+90g H2O)
moles urea = grams/molar mass urea.
moles H2O = grams/molar mass H2O.
XH2O = moles H2O/total moles.
Then plug this X for H2O into the equation at the top, multiply by 55.3 mm.

To calculate the vapor pressure of a 10% aqueous solution of urea at 40°C, you need to understand the concept of Raoult's law.

Raoult's law states that the partial vapor pressure of a volatile component in a solution is directly proportional to its mole fraction in the solution.

Step 1: Determine the mole fraction of urea in the solution.
The mole fraction (X) of urea is calculated by dividing the moles of urea by the total moles of the solution. Since we have a 10% solution, this means that 10 grams of urea is dissolved in 100 grams of water.

Step 2: Calculate the mole fraction of water.
Since we know the mass of water in the solution is 100 grams, we can determine the moles of water using its molar mass (18 g/mol). Divide the mass of water by its molar mass to get the moles of water.

Step 3: Calculate the total moles in the solution.
Add the moles of urea and the moles of water together to get the total moles in the solution.

Step 4: Calculate the vapor pressure of the urea solution.
Use Raoult's law to calculate the vapor pressure of the urea solution at 40°C. The vapor pressure of water at this temperature is given as 55.3 mmHg. Multiply the mole fraction of water (X) by the vapor pressure of water to get the vapor pressure of the solution.

By following these steps, you can determine the vapor pressure of a 10% aqueous solution of urea at 40°C.

The first equation should read this way.

Psoln = XH2O*PoH2O