Molality: Calculate Aqueous Solution Density 1g/(cm^3)

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Discussion Overview

The discussion revolves around calculating the molality of an aqueous solution containing a specific protein concentration, considering the solution's density. Participants explore the definitions and calculations related to molality, including the relationship between solute and solvent in the context of the solution's density.

Discussion Character

  • Homework-related
  • Mathematical reasoning

Main Points Raised

  • One participant asks how to find the molality of a solution with 1g/L of a protein with a given molar mass, given the solution's density.
  • Another participant clarifies that molality is defined as moles of solute per kilogram of solution and suggests starting with this approach.
  • A participant reiterates the definition of molality as moles of solute over kilograms of solvent and seeks guidance on determining the kilograms of solvent.
  • One participant provides a logical framework for the calculation, indicating that the mass of protein in the solution can be related to the total mass of the solution.
  • Another participant suggests that it is acceptable to assume the addition of protein does not change the volume of the water significantly.
  • A later reply confirms that this assumption allows for the calculation to proceed.

Areas of Agreement / Disagreement

Participants express some agreement on the definitions of molality and the approach to calculating it, but there remains uncertainty regarding the assumptions about volume changes and the specific calculations needed to find the kilograms of solvent.

Contextual Notes

Participants discuss the assumption that the addition of protein does not alter the volume of the solution, which may not hold in all scenarios. The discussion also highlights the need for clarity on the definitions and relationships between solute and solvent in the context of molality.

bomba923
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How do I find the molality of an aqueous solution containing 1g/L of a certain protein with molar mass 9.0 x 10^4 g/mol if the density of the solution is 1g/(cm^3)??
 
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Molality is expressed with mole of the solute in one kilogram of solution. Try this approach first.
 
My book says molality is moles of solute over kilograms solvent.

My question/problem is how to find the kilograms of solvent
 
U needn't.Use what Chem_Tr told u and a bit of logics.Just to get u started

1g protein--------------------->1L solution
1g solution--------------------->1 cc solution

Question:
1g protein--------------------->x Kg solution...

Why didn't i pick "g solution" in the last line??Because u need to find moles protein/Kg solution...


Daniel.
 
bomba923 said:
My book says molality is moles of solute over kilograms solvent.

My question/problem is how to find the kilograms of solvent
You may assume that adding a gram of protein to a liter of water does not change its volume (or the density).
 
In that case...yes!--I can find it
 

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