Ask Question
25 December, 18:39

Calculate the mass of urea that should be dissolved in 175 g of water at 35°C to produce a solution with a vapor pressure of 38.1 mmHg. (At 35°C, P o water = 42.2 mmHg.)

+2
Answers (2)
  1. 25 December, 18:40
    0
    The mass of urea that dissolved in the solution is 62.72 g

    Explanation:

    Psol = Xsolvent * Psolvent

    Where;

    Psol is the vapor pressure of the solution = 38.1 mmHg

    Psolvent is the vapor pressure of water = 42.2 mmHg

    Xsolvent is the mole fraction of the solvent = ?

    Xsolvent = Number of moles of solvent/Total number of moles in the solution

    Molar mass of water = 18 g

    Number of moles of solvent = 175/18 = 9.722 mols

    Let the number of moles of urea present in the solution = n

    Xsolvent = Psol/Psolvent

    Xsolvent = 38.1 / 42.2 = 0.903 mols

    Also, Xsolvent = 9.722 / (n + 9.722)

    0.903 = 9.722 / (n + 9.722)

    0.903 (n + 9.722) = 9.722

    0.903n + 8.779 = 9.722

    0.903n = 9.722 - 8.779

    0.903n = 0.943

    n = 0.943/0.903

    n = 1.0443 mols

    Thus, the number of moles of urea present in the solution is 1.0443 mols

    Molar mass of urea = 60.06 g/mol

    Therefore, the mass of urea that dissolved in the solution = 1.0443 * 60.06

    mass of urea = 62.72 g
  2. 25 December, 18:50
    0
    We should dissolve 62.5 grams of urea

    Explanation:

    Step 1: Data given

    mass of water = 175 grams

    Temperature = 35.0 °C

    Vapor pressure of solution = 38.1 mmHg

    Vapor pressure of water = 42.2 mmHg

    Step 2: Calculate mol fraction H2O

    Mol fraction H2O = 38.1 mmHg / 42.2 mmHg

    Mol fraction H2O = 0.903

    Step 3: Calculate mol fraction urea

    mol fraction urea = 1 - 0.903 = 0.097

    Step 4: Calculate moles H2O

    Moles H2O = 175 grams / 18.02 g/mol

    Moles H2O = 9.71 moles H2O

    Step 5: Calculate moles urea

    moles urea = x

    x / (9.71 + x) = 0.097

    x = 1.04 moles urea

    Step 6: Calculate mass urea

    mass urea = 1.04 moles * 60.06 g/mol = 62.5 grams of urea

    We should dissolve 62.5 grams of urea
Know the Answer?
Not Sure About the Answer?
Find an answer to your question 👍 “Calculate the mass of urea that should be dissolved in 175 g of water at 35°C to produce a solution with a vapor pressure of 38.1 mmHg. (At ...” in 📗 Chemistry if the answers seem to be not correct or there’s no answer. Try a smart search to find answers to similar questions.
Search for Other Answers