Problem 91 - A Complete Resource Book in Chemistry for JEE Main

Question

A certain metal \(\mathrm{M}\) is used to prepare an antacid, which is used as a medicine for acidity. This metal accidently catches fire, which can not be extinguished by using \(\mathrm{CO}_{2}\) based extinguishers. The metal \(\mathrm{M}\) is (a) \(\mathrm{Mg}\) (b) \(\mathrm{Ba}\) (c) \(\mathrm{Be}\) (d) \(\mathrm{C}\)

Step-by-Step Solution

Answer

The metal is (a) Mg.

Step 1: Analyze the Properties of CO2 Extinguishers

CO2 extinguishers work effectively on fires caused by substances that do not react with CO2. They are unsuitable for metals that can react with CO2 and release energy.

Step 2: Examine the Properties of the Metal Options

Consider the reactivity of the metals given in the options with CO2. Metals like Magnesium (Mg) can actively react with CO2 to form metal oxides and carbon, which can sustain combustion.

Step 3: Identify Metals Used in Antacids

Antacids are designed to neutralize stomach acid, and common ingredients include compounds of alkaline earth metals like Magnesium (Mg) because they are effective in neutralizing excess acid.

Step 4: Determine Which Metal Cannot Be Extinguished by CO2

Magnesium (Mg) is known to burn at high temperatures and can react with CO2 to form magnesium oxide and carbon. This reaction releases additional heat, making CO2 ineffective at extinguishing the fire.

Key Concepts

Magnesium in Antacids

Magnesium is a common ingredient in antacids that many people use to relieve heartburn or indigestion. But why magnesium? This alkaline earth metal has properties that make it excellent at neutralizing stomach acids.

When you ingest magnesium-based antacids, the magnesium compounds react with the hydrochloric acid present in your stomach. The primary purpose is to alleviate the discomfort caused by acid reflux by raising the pH balance to lessen acidity levels.

• Reactivity: Magnesium easily reacts with acids, making it ideal for neutralizing gastric acid.


• Effectiveness: Compared to other metals like calcium, magnesium often offers quicker relief from acidity symptoms.


• Safety: In regulated dosages, magnesium in antacids is safe for most users.

Overall, magnesium’s effectiveness and regulation in the body make it a preferred choice for many over-the-counter antacid formulations.

CO2 Fire Extinguisher Limitations

CO2 fire extinguishers are popular due to their efficiency in putting out fires, especially electrical ones, without leaving residues. However, they have limitations and are not suitable for every type of fire.

While effective against ordinary combustible liquids and most electrical fires, CO2 extinguishers fall short when it comes to certain metals. Here's why:

• Reactivity Concerns: Metals like magnesium (Mg) can react with CO2. Instead of extinguishing the fire, this reaction can produce more heat, prolonging combustion.


• Combustion Enhancements: As CO2 gets consumed in forming metal oxides, additional oxygen can fuel the fire.


• Not All-Purpose: When it comes to materials that can produce intense heat, like magnesium, CO2 extinguishers become ineffective.

Understanding the limitations of CO2 extinguishers is crucial for fire safety, ensuring that the correct extinguisher type is used for the specific scenario.

Magnesium Combustion Properties

Magnesium is a fascinating metal, especially when it comes to its combustion properties. It holds the tendency to combust with bright, intense fire, which makes it both useful and challenging.

When igniting, magnesium produces a very bright white light. This quality makes it valuable in applications where bright illumination is required, such as flares and fireworks. However, some unique properties make it difficult to control:

• High Temperature Combustion: Magnesium burns at incredibly high temperatures, making the flames difficult to extinguish without special equipment.


• Reactivity with CO2: When burning, magnesium can react with CO2 to form magnesium oxide and carbon, which perpetuate the fire.


• Light Emission: The intense white light emitted doesn't just make magnesium valuable in some areas, but also raises safety concerns due to potential eye damage.

Keeping these properties in mind, one must handle magnesium with care, particularly around open flames or combustibles.