Solutions: Solubility and Intermolecular Forces: Videos & Practice Problems

Solubility is a chemical property referring to a solute's ability to dissolve in a solvent, forming a homogeneous mixture known as a solution. Conversely, a heterogeneous mixture occurs when a solute does not dissolve. The principle of "like dissolves like" suggests that compounds with similar intermolecular forces (IMFs) and polarities are miscible, meaning they can mix to form a solution. The types of IMFs include ion-dipole (polar, found in ionic compounds), hydrogen bonding (polar, in compounds with hydrogen attached to fluorine, oxygen, or nitrogen), dipole-dipole (polar, in polar covalent compounds), and London dispersion forces (nonpolar, present in all compounds but dominant in nonpolar covalent compounds). If two substances share the same polarity or IMFs, they are likely to be miscible and create a solution. Understanding the nature of IMFs is crucial in predicting solubility and miscibility of substances.

Solubility and Mixtures

Now before we can talk about solutions and how it relates solubility in the intermolecular forces, first recall that solubility is a chemical property and it deals with the ability of a solute to become dissolved in a solvent. Now another term for being dissolved is meaning missable. That means the two things will mix together.

Now, a solution itself represents a homogeneous mixture that is created when a solvent dissolves a solute. Now, not all solutes can be dissolved by a solvent. In those situations, we say we have a heterogeneous mixture. So a heterogeneous mixture is created when a solvent cannot dissolve a solute.

So just keep these terms in mind when we're talking about solubility, intermolecular forces and how they relate to the idea of solutions. So a homogeneous mixture is another term for a solution where a solute and solvent has successfully been mixed together.

Gas Solubility Example

The following table represents a solubility of a few nonpolar gases in water at 25�C under a total pressure of 1.0 atmospheres. Based on the information provided, what is the most likely solubility value of F₂?

So if we take a look here, we have N₂O₂ and F₂N₂ has a solubility of 0.6 millimolar, O₂ has 1.2 millimolar, and F₂ is what we need to find. If you look on your periodic table, you'll see that nitrogen is in Group 5A, Oxygen is in Group 6A and then fluorine is in Group 7A. From the pattern that we see going from nitrogen to oxygen, we can see that the solubility is increasing.

Now this partly is due to the fact that oxygen O₂ weighs more than N₂ and therefore it's going to be more soluble because it connects to ideas such as intermolecular forces. Now here we're going to say that going from N₂ to O₂ the mass is increasing, so our solubility increases and we can see that it increases by a lot. It goes from 0.6 to 1.2. Following this pattern, we should expect the solubility to keep on increasing if we go from O₂ to F₂.

So we should expect the solubility to be higher than 1.2, which means that A&B are out. Now going from N₂ to O₂ there was a big increase, so we should expect that continued pattern. There should be a big increase. Going from O₂ to F₂C wouldn't work because going from 1.2 to 1.3 is not a big enough increase. So the best answer here would be option D 4.2 millimolar for the solubility of F₂.

Intermolecular Forces in Solutions

Under the theory of likes dissolves likes. We say here that compounds with the same intermolecular force, which I'm going to abbreviate as IMF and Oregon polarity, we'll dissolve into each other to form a solution. Remember a solution is when a solute is successfully dissolved by a solvent.

Now here we have our different types of intermolecular forces, the types of compounds that has that as their major force and then whether that force is polar or nonpolar. So ion dipole is the strongest of the intermolecular forces, it is the major force of ionic compounds. Ion dipole itself represents a polar force. So we're going to say here that this is ionic and it is a polar intermolecular force.

Next strongest is hydrogen bonding, which is just a special type of dipole dipole bonding, so just keep that in mind. So hydrogen bonding happens as the major force for compounds containing hydrogen directly connected to fun, Fon. So fluorine, oxygen or nitrogen. Now this is also a polar intermolecular force. Dipole dipole is the major force of polar covalent compounds. So it already describes the type of compounds that happen as their major force. So it itself has to be a polar intermolecular force.

Then finally we have London dispersion forces, also called van der Waals forces or just dispersion forces as a whole. Now we're going to say that this force is found in all compounds. It doesn't matter what the compound is, it has some of this in it, but it is the major and only force of non polar covalent compounds. And since it's the major force of non polar covalent compounds, it itself is a non polar intermolecular force.

So again, we can look at two different substances if you can tell their polarities. If both are polar, they'll dissolve into each other. If both are non polar they'll dissolve into each other. That's the idea of likes. Dissolve likes. Two things that have the same polarity are missable, they will mix together. If one is pole and one is non polar, they will not mix.

Let's say that you're looking at 2 substances and can't tell if they're polar, non polar. Then try to look at their intermolecular forces. If they both have the same intermolecular force, they're going to have the same basic idea of polarity, OK? And again, that will reinforce the idea of them being missable and being able to mix to form a solution. So keep this in mind when comparing any two substances to one another.

Intermolecular Forces Example

Identify the intermolecular forces present in both a solute and solvent and predict whether a solution will form between the two. So here we have 50 grams of arsenic pentachloride placed into 250 grams of water. All right, so first of all, we know that water is our solvent since it's larger in a mouth. Water we know as a polar solvent because it possesses hydrogen bonding. So we're going to say H bonding.

Now arsenic pentachloride, it's not as obvious what kind of intermolecular force it has, so we're going to draw it out. Arsenic is in Group 5A, so it has five valence electrons and we're going to say here that the chlorines are in Group 7A, so they have 7 valence electrons. And remember, halogens, when they're not in the center, only make single bonds. So each one of these chlorines will single bond to the arsenic and in that way we'll have our molecular shape for arsenic pentachloride.

If we take a look here, we're going to know that this is one of our perfect shapes that we've talked about in our earlier topics dealing with molecular polarity. Because it is a perfect shape. It has the same surrounding elements, it has no lone pairs. It's one of the perfect shapes. It is non polar in nature. So we're going to say here that arsenic pentachloride is nonpolar and therefore it's intermolecular force would be London dispersion forces or Vander Waals forces.

Now London dispersion is a non polar force, hydrogen bonding is a polar force. Their polarities don't match and as a result we cannot form a solution with them. So we've classified with their intermolecular forces are and we've classified their polarity as a result and from that we know that no, a solution will not form between the two.

Indicate the most important type of intermolecular attraction responsible for solvation in the following solution:
Methanol, CH₃OH, dissolved in ethanol, CH₃CH₂OH

• A. Ion-Dipole
• B. Dipole-Dipole
• C. Hydrogen Bonding
• D. Dispersion Forces
• E. Ionic Bonding

Answer: (C)

Which of the following solutes will most readily dissolve in H₂O?

• A. HOCH₂CH₂CH₂OH
• B. CH₃CH₂CH₂CH₃
• C. CH₃CH₂CH₂OH
• D. CCl₄
• E. HOCH₂CH₂OH

Answer: (E)

Two pure chemical substance are likely to mix and form a solution if:

• A. The formation of the solution causes an increase in energy.
• B. One substance is polar and the other is nonpolar.
• C. The formation of the solution causes an increase in randomness.
• D. Strong intermolecular attraction between the solute molecules.

Answer: (C)

Which of the following statements is/are true?
I. The hydrocarbon methane (CH₄) will dissolve completely in acetone (CH₃COCH₃).
II. Ammonia (NH₃) will form a heterogeneous mixture with carbon tetrachloride (CCl₄).
III. Pentane (C₅H₁₂) will form a homogeneous mixture with carbon tetrabromide (CBr₄).
IV. Methanethiol (CH₃SH) is miscible in fluoromethane (CH₃F).

• A. I only
• B. II and III
• C. II, III, IV
• D. III and IV
• E. None of the above

Answer: (C)

Here’s what students ask on this topic:

What is solubility and how does it relate to solutions?

Solubility is a chemical property that refers to the ability of a solute to dissolve in a solvent, forming a homogeneous mixture known as a solution. When a solute dissolves in a solvent, the resulting mixture is uniform throughout, meaning the solute particles are evenly distributed within the solvent. This homogeneous mixture is called a solution. Conversely, if a solute does not dissolve in a solvent, a heterogeneous mixture is formed, where the solute and solvent remain distinct and separate. Understanding solubility is crucial in predicting whether a particular solute will dissolve in a given solvent, which is essential in various chemical processes and applications.

What is the principle of 'like dissolves like' in chemistry?

The principle of 'like dissolves like' in chemistry states that compounds with similar intermolecular forces (IMFs) and polarities are likely to dissolve in each other, forming a solution. This means that polar substances tend to dissolve in polar solvents, and nonpolar substances tend to dissolve in nonpolar solvents. For example, water (a polar solvent) can dissolve salt (a polar solute) because both have similar IMFs. Conversely, oil (a nonpolar substance) does not dissolve in water because their IMFs are different. Understanding this principle helps predict the solubility and miscibility of substances in various solvents.

What are the different types of intermolecular forces and their characteristics?

There are four main types of intermolecular forces (IMFs):

1. Ion-dipole: The strongest IMF, found in ionic compounds, and is polar.

2. Hydrogen bonding: A special type of dipole-dipole interaction, occurring in compounds with hydrogen directly bonded to fluorine, oxygen, or nitrogen. It is also polar.

3. Dipole-dipole: Found in polar covalent compounds, where the positive end of one molecule is attracted to the negative end of another. It is polar.

4. London dispersion forces: The weakest IMF, present in all compounds but dominant in nonpolar covalent compounds. It is nonpolar.

These IMFs determine the physical properties and solubility of substances.

How do intermolecular forces affect solubility?

Intermolecular forces (IMFs) significantly affect solubility by determining how well a solute can interact with a solvent. According to the principle of 'like dissolves like,' substances with similar IMFs are more likely to be soluble in each other. For example, polar solutes with strong IMFs like hydrogen bonding or dipole-dipole interactions will dissolve well in polar solvents with similar IMFs. Conversely, nonpolar solutes with London dispersion forces will dissolve better in nonpolar solvents. If the IMFs between the solute and solvent are different, the solute is less likely to dissolve, resulting in a heterogeneous mixture.

What is the difference between a homogeneous and a heterogeneous mixture?

A homogeneous mixture, also known as a solution, is a mixture where the solute is evenly distributed within the solvent, resulting in a uniform composition throughout. An example is salt dissolved in water. In contrast, a heterogeneous mixture is one where the solute does not dissolve in the solvent, leading to a non-uniform composition with distinct phases. An example is oil and water, where the two substances remain separate. Understanding the difference between these mixtures is essential in studying solubility and the behavior of substances in various solvents.