Problem 87 - Introductory Chemistry Atoms First

Question

What effect does increasing pressure have on the solubility of gaseous solutes? Explain your answer.

Step-by-Step Solution

Answer

Increasing pressure has a direct positive effect on the solubility of gaseous solutes, as described by Henry's Law (\( C = kP \)). Higher pressure causes more gas molecules to dissolve into the liquid, resulting in a higher concentration of dissolved gas. Therefore, higher pressure leads to higher solubility for gaseous solutes.

Step 1: Understand Henry's Law

Henry's Law states that the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas above the liquid. Mathematically, it can be expressed as: \[ C = kP \] Where: - \(C\) is the solubility (molar concentration) of the gas in the liquid - \(k\) is a constant specific to the solute-solvent system (Henry's Law Constant) - \(P\) is the partial pressure of the gas above the liquid

Step 2: Explain the Pressure-Solubility Relationship

The relationship between pressure and solubility, as described by Henry's Law, implies that when the pressure above the liquid is increased, the solubility of the gaseous solute in the liquid will also increase. This occurs because an increase in pressure causes more gas molecules to dissolve into the liquid and reach an equilibrium between the dissolved and undissolved states, resulting in a higher concentration of dissolved gas in the liquid.

Step 3: The Effect of Increasing Pressure on Solubility

In conclusion, according to Henry's Law, increasing pressure has a direct positive effect on the solubility of gaseous solutes. As the pressure above the liquid increases, more gas molecules dissolve into the liquid phase, leading to a higher concentration of dissolved gas. So, higher pressure results in higher solubility for gaseous solutes.

Key Concepts

Gas Solubility

Gas solubility refers to the ability of a gas to dissolve in a solvent, such as a liquid. This is an important concept in chemistry because it helps us understand how gases behave in different environments and conditions. The solubility of a gas is influenced by several factors, including temperature, pressure, and the specific properties of the gas and solvent. Gas solubility is typically measured in terms of molar concentration, which is the amount of gas that can be dissolved in a given volume of solvent at a specific temperature and pressure. The more soluble the gas, the greater the amount that will dissolve in the solvent, resulting in a higher concentration.

Pressure and Solubility

The relationship between pressure and solubility is crucial for understanding how gases dissolve in liquids. Henry's Law plays an important role here, demonstrating that the solubility of a gas in a liquid is directly proportional to the pressure of the gas above the liquid. As the pressure increases:

• More gas molecules are forced into the liquid.
• The rate of gas dissolution increases.
• An equilibrium is established with a higher concentration of the dissolved gas.

This means that increasing the pressure above a liquid allows more gas to dissolve, enhancing its solubility. This concept is applied in various real-life scenarios, such as carbonated beverages, where gas is kept under high pressure to ensure maximum solubility.

Molar Concentration

Molar concentration, often referred to as molarity, is a measure of the concentration of a solute in a solution. It is represented by the formula:\[ C = \frac{n}{V} \]where:

• \(C\) is the molar concentration (moles per liter or mol/L).
• \(n\) is the number of moles of the solute.
• \(V\) is the volume of the solution in liters.

Molar concentration is a key factor in understanding gas solubility, as it helps quantify how much gas is dissolved in the solution under certain conditions. A higher molar concentration indicates more solute (gas) is dissolved in the solvent, controlled by Henry's Law and conditions like pressure.

Partial Pressure

Partial pressure is a term used to describe the pressure exerted by a single type of gas in a mixture of gases. In the context of Henry's Law, partial pressure refers to the specific pressure of a gas above the liquid in which it is being dissolved. The partial pressure of a gas affects its solubility in a liquid. According to Henry's Law:

• The solubility of a gas is directly proportional to its partial pressure.
• Higher partial pressure results in higher gas solubility.

For example, if the partial pressure of a gas such as oxygen increases, more of that gas will dissolve in a solvent like water, which is particularly important in contexts such as respiration and the carbonation of drinks. Understanding partial pressure helps in calculating and predicting the behavior of gases under different pressure conditions.