Orgo Lab MT

Question 1

Melting pt. determination Impure compound

Answer 1

dramatically lower melt. pt,

Question 2

factors affecting melting pt.

Answer 2

• size
• individual bonds
• symmetry of molecule

Question 3

pure compound melt pt.

Answer 3

melts sharply within publicized range

Question 4

property allowing sep. by recrystallization

Answer 4

solubility

Question 5

property allowing sep. by solvent partitioning

Answer 5

density

Question 6

separation by steam distillation

Answer 6

boiling point

Question 7

purpose of hot filtration

Answer 7

hot solution to remove insoluble impurities

Question 8

% recovery =

Answer 8

(mass of crystals / mass of original) x 100

Question 9

desired property for chromatography

Answer 9

polarity

Question 10

steam distillation best for …

Answer 10

heat sensitive compounds (limonene)

Question 11

purpose of melt pt. experiment

Answer 11

determine the unknown compound using known melting temperatures

Question 12

2 things determined by melting point

Answer 12

1. identity of substance

2. purity of substance

Question 13

recrystalzation, why water as solvent?

Answer 13

components have different solubilities, and benzoic acid is insoluble in cold, but very soluble in hot water

Question 14

why nucleation is important to not disturb

Answer 14

1. tiny crystals will form

2. larger surface area for impurity attachment

Question 15

what is bumping?

Answer 15

violent boiling caused by superheating. boiling chips resolve

Question 16

direction cold water flow in condensor

Answer 16

away from recieving flask

Question 17

why steam distillation ?

Answer 17

isolate heat sensitive compounds

Question 18

bromine test

Answer 18

steam distillation; discoloration confirms presence of limonene