Chemistry, asked by gagan694, 11 months ago

the vapour pressure of water is 92mm at 323k . 18.1g of urea are dissolved in 100 g of water the vapour pressure is reduced by 5mm . calculate the molar mass of urea​

Answers

Answered by kobenhavn
25

Answer: The molar mass of urea is 60 g/mol

Solution:

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,

\frac{p^o-p_s}{p^o}=\frac{w_2M_1}{w_1M_2}

where,

p-p^o = lowering in vapour pressure= 5 mm

p^0= vapor pressure of pure solvent (water) = 92 mm

w_2 = mass of solute  (urea) = 18.1 g

w_1 = mass of solvent (water) = 100 g

M_1 = molar mass of solvent (water) = 18 g/mole

M_2 = molar mass of solute (urea) = M g/mole

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

\frac{5}{92}=\frac{18.1 \times 18}{100\times M}

M=60g/mol

Therefore, the molar mass of urea is 60 g/mol

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