If 0.98 g of an unknown was dissolved in 10.30 g of solvent and the resulting solution has a molality of 0.45 m, what is the molar mass of the unknown

The molecular mass of the unknown has been 211.66 g/mol.

Molality can be defined as the moles of the solute per kg of solvent.

Molality can be expressed as:

Molality = ......(i)

The given unknown has been the solute.

The mass of solute = 0.98 g.

The mass of solvent = 10.30 g.

The molality of the solution formed has been = 0.45 m.

Substituting the values in equation (i):

0.45 m =

0.45 m =

 =  

 = 0.00463

Molecular mass of solute =

Molecular mass of solute = 211.66 g/mol.

The molecular mass of the unknown has been 211.66 g/mol.

For more information about the molality of the solution, refer to the link:

link

211.4g/mol.

Explanation:

Data obtained from the question includes:

Mass of unknown compound = 0.98g

Mass of solvent = 10.30g

Molality = 0.45 M

Next, we shall determine the number of mole of the unknown compound present in the solution.

This can be obtained as follow:

Molality = mole /kg of solvent

Mole of the unknown compound =.?

Mass of solvent = 10.30g = 10.30/1000 = 0.0103Kg

Molality = 0.45 M

Molality = mole /kg of solvent

0.45 = mole /0.0103

Cross multiply

Mole = 0.45 x 0.0103

Mole = 4.635×10¯³ mole

Therefore the mole of the unknown compound that dissolve in solution is 4.635×10¯³ mole

Now, we can obtain the molar mass of the unknown compound as follow:

Mole of the unknown compound = 4.635×10¯³ mole

Mass of unknown compound = 0.98g

Molar mass of the unknown compound =?

Mole = mass /Molar mass

4.635×10¯³ = 0.98 /Molar mass

Cross multiply

4.635×10¯³ x molar mass = 0.98

Divide both side by 4.635×10¯³

Molar mass = 0.98 / 4.635×10¯³

Molar mass = 211.4g/mol.

Therefore, the molar mass of the unknown compound is 211.4g/mol.

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