Which solvent, water or hexane would you choose to dissolve each of the following?

Question

Which solvent, water or hexane (CH₃​(CH_2​)₄​CH₃​), would you choose to dissolve each of the following? a. Cu(NO₃​)₂​ 

b. CS₂​ 

c. CH₃​CO_2​H 

d. CH_3​(CH₂​)₁₇​OH 

e. HCl 

f. C₆​H₆​

Answer 1

The general principle involve is that solid or liquid substances of similar polarity tend to dissolve in each other. Or, more succinctly: Like dissolves like.

Choosing between water (a very polar solvent) and hexane (a very nonpolar solvent), we expect polar compounds to be more soluble in water and nonpolar compounds to be more soluble in hexane

Answers

a. Cu(NO₃​)₂​ is ionic, which makes it very polar, so we choose water.

b. CS₂​  is a nonpolar molecule, so we choose hexane.

c. CH₃​CO_2​H  is a polar molecule (because of the hydrogen-bonding CO_2​H group) so we choose water.

d. CH_3​(CH₂​)₁₇​OH  is a molecule comprised of a long nonpolar chain capped by a tiny polar group.

Tougher choice than the others, but we choose hexane (nonpolar chain decides...).

e. HCl  is a very polar molecule (Cl is mch more electronegative than H), so we choose water

f. C₆​H₆​ is a nonpolar molecule, so we choose hexane.