Question

molality of 40%(by mass solution)urea solution is​

Answer 1

Explanation:

40% by mass urea solution means 40 gram urea in 100 gram solution.

Thus molality can be given as,

m=(mass of urea in grams/molar mass of urea in gram per mole)*(1000/mass of solvent in grams)

Here mass of solvent can be given as,

Mass of solvent=Mass of solution - mass of solute

=100 - 40

=60

m=(40/60)*(1000/60)

m=200/18

m=11.11 molal

Answer 2

Molality(m) of 40% urea solution is 11.12 mol/kg

Given:

40% by mass solution it means that

40 g of solute is present in 100 g of solution.

To Find:

Molality(m) =  ?

Solution:

We can find the molality easily by using the formulas;

The molar mass of Solute(Urea)((NH2CONH2) is

M=14*1+2*1+12*1+16*1+14*1+2*1

M=60 g/mol

Molality (m)= $\frac{Moles * 1000}{Molar mass of solute}=\frac{n*1000}{M}$

Where moles(n)= Given Mass/Molar Mass =40/60=0.667 mol

M=60 g/mol

Therefore after putting the values in the formula we get,

m=$\frac{n*1000}{M}$=$\frac{0.667*1000}{60}$=$\frac{667}{60}$=$11.12$ mol/kg

Hence the molality of 40% by mass urea is 11.12 mol/kg.

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