Question

If x g of solute has molar mass mg/mole is present in y g of solution then molality is

Answer 1

Answer:

Explanation:

Given that

Density of the solution =d (in gm/ml)

Molarity of the solution =M

Molar mass of the solute =M ^B​  (in gm/mol)

Let's take 1000 ml of the solution, then  

Mass of the solution = Volume (ml) × density

                                  = 1000 ml × d gm/ml = 1000 d gm

Moles of solute =M×Volume=M×1lit=Mmoles  (Since, 1000ml=1liter)

∴   Mass of the solute = No. of moles× Molar  mass =MM ^B   gm

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∴   Mass of the solvent = mass of the solution − mass of the solute=(1000d−MM ^ B  ) gm

Now,  

Molality (m) =Kilogramsofsolvent  / molesofsolute

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 ∴   m=  M  / (1000d−MM ^ B  )×  1  / 1000

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⇒m= 1000M  /  1000d−M/M^B

 ⇒ 1000M / 1000d + m.Mb = M

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