Author Question: Compound A has a refractive index of 1.4577 at 20, while compound B (miscible with com pound A) has ... (Read 27 times)

Anajune7 · **on:** Aug 23, 2018

Compound A has a refractive index of 1.4577 at 20, while compound B (miscible with com
pound A) has a refractive index of 1.5000 at the same temperature.
(a) How could you experimentally determine if the refractive indexes of mixtures of A and B
follow a linear relationship to the mole percent compositions of the mixtures?
(b) If the relationship is linear, what is the composition (in mole percent) of a mixture that has
a refractive index of 1.4678 at 20C?

Question 2

You have a mixture of p-nitrobenzaldehyde (vapor pressure 0.01 at its melting point of 106)
and camphor. Explain how you would separate these two compounds by sublimation. How
would you perform the sublimation if benzoic acid instead of camphor is used?

14vl19 · **Reply #1 on:** Aug 23, 2018

Answer to Question 1

(a) Prepare several mixtures of A and B with known compositions. Determine their refractive
indexes. Construct a graph of mol versus nD and see if the points fall on the line joining
1.4577 (100A) and 1.5000 (100B).
(b) 76 A24 B (from the graph not shown here)

Answer to Question 2

Subject the mixture of p-nitrobenzaldehyde and camphor to atmospheric sublimation; the
camphor will sublime onto the tube filled with ice while the p-nitrobenzaldehyde remains in
the flask itself. If benzoic acid is used, the mixture could be separated similarly using vacuum
sublimation.