Why is Specific Rotation Not a Colligative Property? Answers Here

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Specific rotation is not considered a colligative property because it is defined based on the concentration of an optically active solution in grams per liter rather than molarity. The formula for specific rotation includes the length of the polarimeter tube and the concentration in g/L, which can be interconverted with molarity. The discussion clarifies that rotation does depend on the number of moles per liter, but the specific rotation formula does not explicitly use molarity. This distinction is important in understanding how specific rotation relates to molecular structure and concentration. Overall, the relationship between concentration and specific rotation is key to grasping why specific rotation is treated differently than colligative properties.
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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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