Author Question: Consider the following solvent pairs. If mixed together, which pairs would form two layers? If they ... (Read 168 times)

EY67 · **on:** Aug 23, 2018

Consider the following solvent pairs. If mixed together, which pairs would form two layers? If
they form two layers, which solvent would be on top?
(a) hexanes and water
(b) water and methylene chloride
(c) hexanes and methylene chloride
(d) methanol and hexanes
(e) ethanol and water
(f) acetone and toluene

Question 2

You and your lab partner take melting points of the same sample. You observe a melting point
of 101107C, while your partner observes a value of 110112C. Explain how two different
melting point values can be observed for the exact same sample.

macagn · **Reply #1 on:** Aug 23, 2018

Answer to Question 1

(a) Would form two layers; the hexanes (d=0.7) would be on top (water, d=1.0).
(b) Would form two layers; the water (d=1.0) would be on top (methylene chloride; d=1.3)
(c) Would not form two layers (miscible).
(d) Would form two layers; the hexanes (d=0.7) would be on top (methanol, d=0.79)
(e) Would not form two layers (miscible).
(f) Would not form two layers (miscible).

Answer to Question 2

If your lab partner took the melting point on a different apparatus, it can be that one or both of
the apparati are not calibrated. If the same apparatus was used, you were probably heating the
apparatus too quickly and the thermometer was not in equilibration with the thermometer,
causing the reading for the melting point to appear too low.