What mass (in g) of urea (co(nh2)2) in 100.0 g of water is needed to decrease the vapor pressure of water from 55.32 mmhg of pure water to 54.21 mmhg for the solution? the temperature is held constant at 40oc.

6.7 g

Explanation:

As the relative lowering of vapor pressure is directly proportional to the amount of dissolved solute.

The formula for relative lowering of vapor pressure will be,

where,

= vapor pressure of pure solvent  (water) = 55.32 mmHg

= vapor pressure of solution = 54.21 mmHg

= mass of solute  (urea) = ? g

= mass of solvent  (water) = 100 g

= molar mass of solvent (water) = 18 g/mole

= molar mass of solute (urea) = 60 g/mole

Now put all the given values in this formula ,we get the vapor pressure of the solution.

Therefore, 6.7 g of urea is needed in 100.0 g of water is needed to decrease the vapor pressure of water from 55.32 mmHg of pure water to 54.21 mmHg for the solution.

i think   the answer is c hope i'm right

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