Question

A solution is prepared by adding 60 g of urea to 180 g of water. The mole frraction of urea and water are ______ and ______ respectively.

• A.
  $0.091,0.909$
• B.
  $0.085,0.915$
• C.
  $0.909,0.091$
• D.
  $0.915,0.085$

Answer 1

The correct option is A

$0.091,0.909$
$\text{Molar mass of}N{H}_{2}CON{H}_2=14+2+12+16+14+2=60g/mol\text{Moles of urea}\left(n_{urea}\right)=\frac{60}{60}=1mol\text{Molar mass of water}=18g/mol\text{Moles of water}\left(n_{water}\right)=\frac{180}{18}=10moles\text{Mole fraction of urea}=\frac{1}{1+10}=\frac{1}{11}=0.0909\approx 0.091\text{Mole fraction of water}=1-0.091=0.909$