Calculate (a) Molality (b) Molarity and (c) Mole Fraction of KI if the density of 20% (mass/mass) aqueous KI is 1.202 g mL⁻¹
By BYJU'S Exam Prep
Updated on: September 13th, 2023
The molality is 1.51 m, the molarity is 1.45 M, and the mole fraction of KI = 0.0263.
Molality is the concentration of solute expressed as the number of moles dissolved in 1 kilogram of solvent, denoted by the symbol ‘m’. Molarity, on the other hand, represents the concentration of solute as the number of moles dissolved in 1 liter of solution, indicated by the symbol ‘M’. Mole fraction is a dimensionless value that signifies the relative proportion of moles for a specific component compared to the total moles in a mixture, and it is denoted by the symbol ‘χ’.
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Calculate Molality, Molarity, and Mole Fraction
Molality, molarity, and mole fraction are all concepts used in chemistry to express the concentration of solutes in solutions. While they are related, they represent different ways of quantifying the amount of solute in a given amount of solvent. These concepts help chemists quantify the concentration of solutes in solutions and describe the composition of mixtures.
Molar mass of Kl = 39 + 127 = 166 g mol⁻
20% (mass/mass) aqueous KI refers to 20g of Kl is present in 100g of solution
20g of Kl is present in (100 – 20) g of water = 80g of water
(a) Molality of solution = moles of Kl/ mass of water in Kg
Substituting the values
= 20/166/ 0.08
= 1.506 m
= 1.51 m (approx)
(b) Given the density of solution = 1.202 g mL⁻1
Volume of 100 g solution = mass/density
Substituting the values
= 100/1.202
= 83.19 ml
= 83.19 x 10⁻3 L
Molarity of solution = 20/166 mole/ 83.19 x 10⁻3 L
= 1.45 M
(c) Moles of Kl = 20/166 = 0.12 mol
Moles of water = 80/18 = 4.44 mol
Mole fraction of Kl = moles of Kl/ moles of Kl + moles of water
Substituting the values
= 0.12/ (0.12 + 4.44)
= 0.0263
Therefore, the molality is 1.51 m, the molarity is 1.45 M, and the mole fraction of KI = 0.0263.
Summary:
Calculate (a) morality (b) molarity and (c) mole fraction of KI if the density of 20% (mass/mass) aqueous KI is 1.202 g mL⁻1
Molality represents the moles of solute per kilogram of solvent, molarity represents the moles of solute per liter of solution, and mole fraction represents the ratio of the moles of a component to the total moles in a mixture. As per the equation:
(a) molality is 1.51 m
(b) molarity is 1.45 M and
(c) mole fraction of KI if the density of 20% (mass/mass) aqueous KI is 1.202 g mL⁻1 is 0.0263.
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