Henry's Law and Gas Solubility Explained

Summary

This script explores Henry's Law, demonstrating how gas solubility in a liquid is affected by pressure. Using carbon dioxide in water, it shows that doubling the pressure quadruples solubility. The script applies Henry's Law to predict how much CO2 escapes from an opened soda bottle, illustrating a practical application of the law in everyday life.

Takeaways

• 🧪 The pressure of a gas above a liquid affects its solubility in that liquid.
• 📦 Experiments with equal-sized vessels demonstrate how pressure impacts gas solubility.
• 🌐 Henry's Law states that the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas.
• 📉 As pressure increases, the solubility of a gas in a liquid doubles with each doubling of pressure.
• 🌿 The example of carbon dioxide dissolving in water is used to illustrate Henry's Law.
• 🥤 Soda bottles are pressurized with carbon dioxide to keep the bubbles dissolved until opened.
• 💨 When a soda bottle is opened, the pressure of CO2 drops, leading to the release of gas and the soda going flat.
• 🔍 Henry's Law constant for CO2 is used to calculate the expected amount of gas that will escape from an opened soda.
• 📏 A calculation shows that approximately 2.7 liters of CO2 will escape from a 1-liter soda over a few hours.
• 🔬 A modern trick allows observing the gas release effect without waiting for the soda to go flat naturally.

Q & A

What is the relationship between the pressure of a gas above a liquid and its solubility?

The solubility of a gas in a liquid is directly proportional to the pressure of the gas above the liquid, as described by Henry's Law.

What is Henry's Law?

Henry's Law states that the solubility of a gas in a liquid is equal to the product of Henry's constant for that gas and the partial pressure of the gas above the liquid.

How does the experiment with three vessels of water and varying amounts of CO2 demonstrate Henry's Law?

The experiment shows that doubling the pressure of CO2 above the water doubles the solubility of CO2 in the water, illustrating a linear relationship between pressure and solubility.

What is the role of Henry's constant in Henry's Law?

Henry's constant is a proportionality constant that relates the solubility of a specific gas to its partial pressure in a solution at a given temperature.

Why does the amount of gas dissolved in soda decrease when the bottle is opened?

When a soda bottle is opened, the pressure of CO2 decreases significantly, leading to a decrease in solubility according to Henry's Law, causing the gas to effervesce.

What is the typical pressure of CO2 in a closed soda bottle?

The typical pressure of CO2 in a closed soda bottle is about 4.0 atmospheres.

How is the solubility of CO2 in water calculated using Henry's Law?

The solubility of CO2 in water is calculated by multiplying Henry's constant for CO2 (3.1 x 10^-2 mole per liter atmosphere) by the partial pressure of CO2 (4 atmospheres in a closed bottle).

What happens to the solubility of CO2 in soda when the bottle is opened?

When the soda bottle is opened, the partial pressure of CO2 drops to nearly zero, resulting in a significant decrease in CO2 solubility.

How much CO2 is expected to escape from a soda bottle once it's been opened?

About 2.7 liters of CO2 is expected to escape from a 1-liter soda bottle once it's been opened, based on the calculation using Henry's Law.

What is the significance of the Henry's Law constant being a constant?

The Henry's Law constant being a constant allows for the prediction of gas solubility changes with pressure changes, as it does not vary with pressure.

What is the practical application of understanding the relationship between gas pressure and solubility in beverages like soda?

Understanding this relationship is crucial for maintaining the fizz in carbonated beverages and for the design of processes that involve gas dissolution, such as in soft drink production.