Question

When a Pepsi bottle is opened, the gas fizzes out because it obeys

• A. Hess's Law
• B. Henry's Law
• C. Kohlarsh's Law
• D. None of the above

Answer 1

The Correct Option is B

Step 1: Understand the question
The question asks why gas fizzes out when a Pepsi (or any carbonated drink) bottle is opened, and which gas law explains this phenomenon.

Step 2: Concept of carbonation
Pepsi and other soft drinks are carbonated, meaning carbon dioxide (CO₂) gas is dissolved in the liquid under high pressure. While the bottle is sealed, the pressure inside is much higher than normal atmospheric pressure, allowing large amounts of CO₂ to remain dissolved in the liquid.

Step 3: Henry’s Law**
Henry’s Law states that the amount of gas that can be dissolved in a liquid is directly proportional to the pressure of that gas above the liquid, at constant temperature. Mathematically: C ∝ P, where C is the concentration of dissolved gas and P is the partial pressure of the gas.

Step 4: Apply to the Pepsi bottle
- Inside the sealed bottle, the pressure of CO₂ is high, so a large amount of CO₂ remains dissolved in the Pepsi. - When the bottle is opened, the pressure above the liquid suddenly decreases to atmospheric level. - As a result, the solubility of CO₂ decreases, and the excess dissolved CO₂ escapes rapidly in the form of bubbles and fizz.

Step 5: Final justification
This process directly demonstrates Henry’s Law, since lowering the pressure reduces the solubility of the gas, making it come out of the solution.

Final Answer: The correct option is (B) Henry’s Law.