Westonci.ca is the best place to get answers to your questions, provided by a community of experienced and knowledgeable experts. Our platform offers a seamless experience for finding reliable answers from a network of experienced professionals. Get detailed and accurate answers to your questions from a dedicated community of experts on our Q&A platform.
Sagot :
The question is incomplete. Here is the complete question.
When 2.10 g of a certain molecular compound X are dissolved in 65.0 g of benzene (C₆H₆), the freezing point of the solution is measured to be 3.5°C. Calculate the molar mass of X. If you need any additional information on benzene, use only what you find in the ALEKS Data resource. Also, be sure your answer has a unit symbol, and is rounded to 2 significant digits.
Answer: MM = 47.30 g/mol.
Explanation: There is a relationship between freezing point depression and molality. With this last one, is possible to calculate molar mass or molar weight of a compound.
Freezing Point Depression occurs when a solute is added to a solvent: the freezing point of the solvent decreases when a non-volatile solute is incremented.
Molality or molal concentration is a quantity of solute dissolved in a certain mass, in kg, of solvent. Its symbol is m and it's defined as
[tex]m=\frac{moles(solute)}{kg(solvent)}[/tex]
Freezing point depression and molal are related as the following:
[tex]\Delta T_{f}=K_{f}.m[/tex]
where
[tex]\Delta T_{f}[/tex] is freezing point depression of solution
[tex]K_{f}[/tex] is molal freezing point depression constant
m is molality
Now, to determine molar mass, first, find molality of the mixture:
[tex]\Delta T_{f}=K_{f}.m[/tex]
[tex]m=\frac{\Delta T_{f}}{K_{f}}[/tex]
For benzene, constant is 5.12°C/molal. Then
[tex]m=\frac{3.5}{5.12}[/tex]
m = 0.683 molal
Second, knowing the relationship between molal and moles of solute, determine the last one:
[tex]m=\frac{moles(solute)}{kg(solvent)}[/tex]
[tex]mol(solute)=m.kg(solvent)[/tex]
mol(solute) = 0.683(0.065)
mol(solute) = 0.044 mol
The definition for Molar mass is the mass in grams of 1 mol of substance:
[tex]n(moles)=\frac{m(g)}{MM(g/mol)}[/tex]
[tex]MM=\frac{m}{n}[/tex]
In the mixture, there are 0.044 moles of X, so its molecular mass is
[tex]MM=\frac{2.1}{0.044}[/tex]
MM = 47.30 g/mol
The molecular compound X has molecular mass of 47.30 g/mol.
Thanks for using our platform. We aim to provide accurate and up-to-date answers to all your queries. Come back soon. Thank you for your visit. We're committed to providing you with the best information available. Return anytime for more. Thank you for choosing Westonci.ca as your information source. We look forward to your next visit.
