(5) Suppose you have three test tubes with three substances, A, B, and C with nearly...

(5) Suppose you have three test tubes with three substances, A, B, and C with nearly the same melting point. Describe how would you proof experimentally (having only melting point apparatus in hand) that these are not the same substances.

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Expert Solution

Add the same amoun of impurity, such as nonvolatyle sample

then

Apply Colligative properties

This is a typical example of colligative properties.

Recall that a solute ( non volatile ) can make a depression/increase in the freezing/boiling point via:

dTf = -Kf*molality * i

where:

Kf = freezing point constant for the SOLVENT;

molality = moles of SOLUTE / kg of SOLVENT

i = vant hoff coefficient, typically the total ion/molecular concentration.

At the end:

Tf mix = Tf solvent - dTf

Then

Each species has different Kf

expect different depression points

calcualte depression points and compare with respect to Kf constant

queen_honey_blossom answered 1 year ago

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