Why is Specific Rotation Not a Colligative Property? Answers Here

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Discussion Overview

The discussion revolves around the nature of specific rotation and its classification as a colligative property. Participants explore the relationship between specific rotation, concentration, and molarity, questioning the definitions and implications of these terms.

Discussion Character

  • Debate/contested

Main Points Raised

  • One participant questions why specific rotation is not considered a colligative property, suggesting it should depend on molarity due to its relation to molecular structure.
  • Another participant clarifies the distinction between rotation and specific rotation, indicating that the confusion may stem from this misunderstanding.
  • A participant acknowledges their confusion and seeks clarification on whether rotation depends on the number of moles per liter, referencing a formula that includes concentration in g/L.
  • There is a discussion about the formula for specific rotation, with a participant noting that it uses concentration in g/L and questioning the absence of molarity in the formula.
  • Another participant responds that while concentration is expressed in g/L, it can be interconverted with molarity, implying that both measures are related but not necessarily interchangeable in this context.

Areas of Agreement / Disagreement

Participants do not reach a consensus on whether specific rotation should depend on molarity or why it is not classified as a colligative property. Multiple viewpoints and questions remain unresolved.

Contextual Notes

There are limitations regarding the definitions of specific rotation and colligative properties, as well as the assumptions about concentration and molarity. The discussion does not resolve these complexities.

pseudogirl
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Why is specific rotation not a colligative property?
i just read that it depends on concentration(gm/litre)
but i feel that it should depend on molarity considering the fact that rotation is due to changes in molecular structure...do i have a point or am i just being silly ...can someone help me?
 
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Looks to me like you are confusing rotation with specific rotation.
 
i am sorry .i did confuse them both
so does rotation depend on number of moles per liter?this is the formula in the book

specific rotation=rotation/l*cl=length of polarimeter tube
c=concentration of optically active solution in (gm/l)why is molarity not there in the formula?
 
pseudogirl said:
so does rotation depend on number of moles per liter?

Yes.

c=concentration of optically active solution in (gm/l)

why is molarity not there in the formula?

Does it have to be there? Concentration in the definition is expressed in g/L, g/L and molarity are easily interconvertible.
 

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