Question

2.57 Calculate molality of KI if the density
of 20% (mass/mass) aqueous Kl is 1.202 g ml'.​

Answer 1

Answer:

$\bigstar{\bold{Molality=1.5\:m}}$

Explanation:

$\Large{\underline{\underline{\bf{Given:}}}}$

• Density of 20% aqueous KI is 1.202 g/ml

$\Large{\underline{\underline{\bf{To\:Find:}}}}$

• Molality of KI

$\Large{\underline{\underline{\bf{Solution:}}}}$

→ Molar mass of KI = 39 + 127 = 166

→ Number of moles of KI = Given mass/Molar mass

→ Substituting the datas we get,

  Number of moles of KI = 20/166 = 0.12 moles

→ Mass of water = 100 - Mass of KI

  Mass of water = 100 - 20

  Mass of water = 80 g  = 0.08kg

→ Molality is given by the equation,

  Molality = number of moles of solute/ mass of solvent in kg

→ Substituting the datas

  Molality = 0.12/0.08

  Molality = 1.5 m

$\boxed{\bold{Molality=1.5\:m}}$

$\Large{\underline{\underline{\bf{Notes:}}}}$

→ Molality is defined as the number of moles of solute per kilogram of the solvent.

  Molality = number of moles of solute/ Mass of solvent in kg

→ Number of moles of solute = Given mass/ Molar mass