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Calculate molarity and molality of 20% …

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Calculate molarity and molality of 20% aqueous ethanol solution by volume .( Density of solution =0.960 gm/ cm3 . assume the solution to be ideal
  • 2 answers

Gaurav Seth 6 years, 6 months ago

20% aqueous ethanol solution by volume means 20 ml/ ethanol in 80 ml/ water.
Density of the solution as 0.960 g/cm3 or 0.960 g/ml
Now,
Mass of solution = density x volume
  = 0.960 x 100
  = 96 g
Mass of 80 ml water = density of water x volume of water
  = 1g/ml x 80 ml = 80 g
Mass of ethanol in solution = mass of solution - mass of water
  = 96-80 = 16 g
Molar mass of ethanol,(C2H5OH) = 12 x 2 + 5x 1 + 16 + 1
  = 46 g
Number of moles of ethanol = 16/46 = 0.348
Molarity = number of moles/volume in litres
  = 0.348/0.1
  = 3.48 M

Molality = number of moles of solute/ mass of solvent in Kg
  = 0.348/0.08
  = 4.35 m

Sandeep Yadav 999 6 years, 6 months ago

Ncert mein h
http://mycbseguide.com/examin8/

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