Question

What is the molality of a solution made by dissolving 137.9g of sucrose in 414.1g of water? The density of the solution is 1.104g/ml.

Answer 1

Answer:

Molality of solution = 0.973 m

Explanation:

Molality : It is defined as the moles of the solute per Kg mass of solvent.It is not temperature dependent.

Solute = Substance which is present in less quantity in the solution is called the solute. Here , Sucrose is the solute.

Solvent = Substance which is present in more quantity is the solvent. Here water is solvent.

$Molality=\frac{moles\ of\ solute}{mass\ of\ solvent}$

Density = It is defined as the mass per unit volume.

$Density=\frac{mass}{Volume}$

Mass of Solute = 137.9 g

$Moles=\frac{mass}{Molar\ mass}$

Molar mass of sucrose =

$C_{12}H_{22}O_{11}$= 12(mass of C)+22(mass of H)+11(mass of O)

= 12(12)+22(1)+11(16)

= 144+22+176

= 342 g/mol

$Moles=\frac{mass}{Molar\ mass}$

$Moles=\frac{137.9}{342}$

$Moles=0.403$

Moles = 0.403 moles

Mass of Solvent = 414.1 g  (water)

$Molality=\frac{moles\ of\ solute}{mass\ of\ solvent(g)}(1000)$

$Molality =\frac{0.403}{414.1}\times 1000$

Molality = 0.973 m