Consider the following solutions. In each case, predict...

Consider the following solutions. In each case, predict whether the solubility of the solute should be high or low. Justify your answers. (a) $\mathrm{LiCl}$ in $n$ -octane, $\mathrm{C}_{8} \mathrm{H}_{18}$ (b) $\mathrm{CaCl}_{2}$ in $\mathrm{H}_{2} \mathrm{O}$; (c) $\mathrm{C}_{8} \mathrm{H}_{18}$ in $\mathrm{H}_{2} \mathrm{O} ;$ (d) $\mathrm{CHCl}_{3}$ in $\mathrm{C}_{6} \mathrm{H}_{14} ;$ (e) $\mathrm{C}_{8} \mathrm{H}_{18}$ in $\mathrm{CCl}_{4}$

Consider the following solutions. In each case, predict whether the solubility of the solute should be high or low. Justify your answers. (a) $\mathrm{LiCl}$ in $n$ -octane, $\mathrm{C}_{8} \mathrm{H}_{18}$
(b) $\mathrm{CaCl}_{2}$ in $\mathrm{H}_{2} \mathrm{O}$;
(c) $\mathrm{C}_{8} \mathrm{H}_{18}$ in $\mathrm{H}_{2} \mathrm{O} ;$
(d) $\mathrm{CHCl}_{3}$ in $\mathrm{C}_{6} \mathrm{H}_{14} ;$
(e) $\mathrm{C}_{8} \mathrm{H}_{18}$ in $\mathrm{CCl}_{4}$

Key Concepts

Like Dissolves Like Principle

This principle states that solutes tend to be soluble in solvents that have a similar polarity. Polar solutes will generally dissolve in polar solvents due to favorable interactions such as hydrogen bonding or dipole-dipole interactions, whereas nonpolar solutes dissolve more readily in nonpolar solvents where dispersion forces dominate.

Polarity and Intermolecular Forces

The polarity of a molecule, determined by its molecular geometry and electronegativity differences, directly affects the types of intermolecular forces present. Polar substances exhibit dipole-dipole interactions or hydrogen bonding, while nonpolar substances interact mainly through van der Waals (dispersion) forces. Understanding these forces helps predict solubility outcomes based on solvent and solute compatibility.

Ionic Solubility in Polar Solvents

Ionic compounds are held together by strong electrostatic forces between ions. Their solubility in polar solvents is largely governed by ion-dipole interactions where the solvent molecules surround and stabilize the ions, overcoming the lattice energy. This concept explains why many salts dissolve well in water but poorly in nonpolar media.

Nonpolar Solvent Interactions

In nonpolar solvents, the dominant interactions are dispersion forces, which are relatively weak compared to hydrogen bonding or ion-dipole attractions. Nonpolar solutes dissolve in such media because their electron clouds can induce favorable temporary dipoles, leading to solvation primarily by van der Waals forces.

Transcript

0:00 Good day.

00:01 Our topic is about solubility.

00:04 So we define solubility as the extent at which solute dissolves in solvent.

00:17 So we note here two terms, solute and solvent, which are terms associated with solutions.

00:25 So it follows that solubility is also the term that defines or that is related with solutions.

00:34 Now, we note that solute and solvent can be any phase of matter, can be gas or liquid or solid, but the determining factor as to whether solute or solvent can be dissolved in each other is by the principle we call where we know commonly as like dissolves -like principle, where it states that solves like principles, where that states that molecules, with the same polarity will dissolve in each other.

01:15 That means polar molecules will dissolve in polar molecules and non -polar molecules will dissolve in non -polar molecules.

01:34 So let us take a look at the difference following examples.

01:39 So say lithium chloride in an octane.

01:50 Okay, lithium chloride is an ionic compound and so it has very high polarity and we say that it's a very polar compound whereas chh18 or octane which is by the way the component of gasoline is a non -polar molecule because these two molecules or we say these two substances or compound have the same or have different rather polarity it follows that licl does not dissolve in water or in obtaining this matter.

02:35 How about let's consider cacl2 in water? just like licl, cacl2 or calcium chloride is ionic and thus polar, very polar.

02:53 And h2o is a polar molecule as it is composed of hydrogen bonded with electronegative oxygen atom.

03:01 So we expect a dipole in the molecule due to the difference in electron sharing making the molecule water molecule polar.

03:10 Since they have the same polarity, then definitely cacl2 dissolves in water.

03:16 Or in terms of solubility, we say that cacl2 has high solubility in water.

03:25 Another that we have to take a look at is this time octane and water...

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