Solutions, Molarity and Intermolecular Forces Video Lessons

Concept: Solutions and Molarity.

# Problem: Predict whether the following pairs of liquids would be miscible or immiscible:a. Water and methyl alcoholb. Hexane and benzenec. Methylene chloride and benzened. Water and toluenee. Ethyl alcohol and isopropyl alcohol

###### FREE Expert Solution

miscible → they will mix and will form a homogeneous mixture
immiscible → they will not mix and will form a heterogeneous mixture

We’re going to use the theory “likes” dissolving “likes”  which states that the solvent can only completely dissolve the solute if they share similar polarity

Therefore, a pure solvent with similar polarity can successfully dissolve a solute to create a solution.

a. Water and methyl alcohol

water (H2O)

▪ water has an electronegative atom (O) → there will be a net dipole moment in the direction of oxygen
▪ water is a polar compound
▪ water can participate in ion-dipole and dipole-dipole interactions

methyl alcohol

▪ alcohols generic formula: ROH
▪ can participate in H-bonding
▪ methyl alcohol will also be polar due to the presence of the –OH group

polar + polar = miscible

b. Hexane and benzene

hexane

▪ made up of C and H only → hydrocarbon
hydrocarbons are nonpolar
▪ hexane → nonpolar

benzene

▪ made up of C and H only → hydrocarbon
hydrocarbons are nonpolar
▪ benzene → nonpolar

Recall that compounds ending in –ene, –ene, and –yne represents hydrocarbons. Hydrocarbons are only made up of carbon and hydrogen and are nonpolar.

nonpolar + nonpolar = miscible

c. Methylene chloride and benzene

methylene chloride

C         4A                   1 x 4 e-4 e-
H         1A                   2 x 1 e-2 e-
F          7A                   2 x 7 e-14 e-
Total:  20 valence e-

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###### Problem Details

Predict whether the following pairs of liquids would be miscible or immiscible:

a. Water and methyl alcohol

b. Hexane and benzene

c. Methylene chloride and benzene

d. Water and toluene

e. Ethyl alcohol and isopropyl alcohol