Chapter 3.2, Problem 22E

a)

Interpretation Introduction

Interpretation:Most suitable solvent for recrystallization of impure solids should be determined. Also, reason for the same should be determined.

Concept introduction:Criteria mentioned below should be used to select solvent for recrystallization.

1. Solvent should be able to dissolve desired compound in itself at high temperatures but insoluble at low temperatures. In short, solvent with favorable temperature coefficient should be used for particular solute.

2. Solvent should be chosen in such way that impurities are either insoluble in it or remain moderately soluble in it at low temperatures.

3. Boiling point of desired solvent should be low so that it gets separated from crystals easily.

4. Boiling point of solvent should be less than melting point of solid under consideration.

5. There should be no reaction between solvent and substance that needs to be purified.

b)

Interpretation Introduction

Interpretation:Reason for ethanol and petroleum ether not to be used as suitable solvent for recrystallization should be determined.

Concept introduction:Criteria mentioned below should be used to select solvent for recrystallization.

1. Solvent should be able to dissolve desired compound in itself at high temperatures but insoluble at low temperatures. In short, solvent with favorable temperature coefficient should be used for particular solute.

2. Solvent should be chosen in such way that impurities are either insoluble in it or remain moderately soluble in it at low temperatures.

3. Boiling point of desired solvent should be low so that it gets separated from crystals easily.

4. Boiling point of solvent should be less than melting point of solid under consideration.

5. There should be no reaction between solvent and substance that needs to be purified.

c)

Interpretation Introduction

Interpretation:Chemical structures for water, ethanol, toluene, petroleum ether, $2\text{-Butanone}$ and acetic acid should be drawn.

Concept introduction:Solvent for recrystallization process should be selected in such way that solute particles remain undissolved in solvent at low temperatures but become soluble at high temperatures. It should be chosen in such way that impurities are either insoluble in it or remain moderately soluble in it at low temperatures.Boiling point of desired solvent should be low so that it gets separated from crystals easily. Boiling point of solvent should be less than melting point of solid under consideration. No reaction should occur between solvent and substance that needs to be purified.

d)

Interpretation Introduction

Interpretation:Most polar and least polar solvents among water, ethanol, toluene, petroleum ether, $2\text{-Butanone}$ and acetic acid should be determined.

Concept introduction:Polar solvents have dipole moment in them while there is no dipole moment in nonpolar solvents. Hexane, benzene, carbon tetrachloride are examples of nonpolar compounds whereas ammonia, water, hydrogen fluoride are polar solvents.