Chapter 9: Problem 15
Saline hydrides are known to react with water violently producing fire. Can \(\mathrm{CO}_{2}\), a well known fire extinguisher, be used in this case? Explain.
Short Answer
Expert verified
No, CO₂ cannot be used, as it doesn't effectively suppress hydrogen fires.
Step by step solution
01
Understand the Reaction
Saline hydrides react with water violently to form hydrogen gas (H₂) and a hydroxide ion. For example, the reaction of sodium hydride with water is: \[ \mathrm{NaH} + \mathrm{H_2O} \rightarrow \mathrm{NaOH} + \mathrm{H_2(g)} \] Hydrogen gas is flammable, contributing to the fire.
02
Identify the Role of CO2 in Fire Suppression
Carbon dioxide (CO₂) is a commonly used fire extinguisher because it displaces oxygen, which is necessary for combustion, and cools the surrounding area. However, it does not interact chemically with hydrogen.
03
Analyze CO2's Effectiveness Against Hydrogen
Hydrogen fires are unique in that hydrogen burns with very little visible flame and CO₂ may not be effective because hydrogen can burn in very low oxygen environments that CO₂ may fail to suffocate completely. Moreover, CO₂ does not remove hydrogen gas, which continues to contribute to the fire.
04
Conclusion on Using CO2 for Saline Hydride Fires
Given that CO₂ does not interact with hydrogen or effectively suppress hydrogen fires, using a CO₂ extinguisher may not be appropriate for a fire involving saline hydrides and hydrogen gas release.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Hydrogen Gas
Hydrogen gas, or H₂, is produced during the reaction of saline hydrides with water. It is a diatomic molecule, meaning it consists of two hydrogen atoms bonded together. Hydrogen is colorless, odorless, and highly flammable.
It burns easily in air, creating water vapor as it combines with oxygen from the atmosphere in the reaction: \[ 2 ext{H}_2 + ext{O}_2 ightarrow 2 ext{H}_2 ext{O} \]When released in a confined space, it can create an explosive mixture with air. This property makes it a considerable fire hazard in scenarios involving hydrogen generation or storage.
In the context of saline hydride reactions, understanding the behavior of hydrogen gas is crucial for grasping why certain fire suppression methods may or may not be effective.
It burns easily in air, creating water vapor as it combines with oxygen from the atmosphere in the reaction: \[ 2 ext{H}_2 + ext{O}_2 ightarrow 2 ext{H}_2 ext{O} \]When released in a confined space, it can create an explosive mixture with air. This property makes it a considerable fire hazard in scenarios involving hydrogen generation or storage.
In the context of saline hydride reactions, understanding the behavior of hydrogen gas is crucial for grasping why certain fire suppression methods may or may not be effective.
Fire Extinguishers
Fire extinguishers are devices designed to suppress fires by removing or disrupting one or more of the key elements needed for fire: fuel, oxygen, and heat. Among the various types of fire extinguishers, carbon dioxide (CO₂) extinguishers are commonly used.
CO₂ extinguishers work by displacing the oxygen around a fire and by cooling the surrounding environment. They release CO₂ gas, which is heavier than air, and it blankets the fire, reducing the available oxygen needed for the fire to continue.
However, these extinguishers are not effective against all types of fires, particularly those involving metals or gases like hydrogen. Hydrogen fires require special attention because despite the CO₂'s ability to displace oxygen, hydrogen can still combust with very low oxygen levels.
CO₂ extinguishers work by displacing the oxygen around a fire and by cooling the surrounding environment. They release CO₂ gas, which is heavier than air, and it blankets the fire, reducing the available oxygen needed for the fire to continue.
However, these extinguishers are not effective against all types of fires, particularly those involving metals or gases like hydrogen. Hydrogen fires require special attention because despite the CO₂'s ability to displace oxygen, hydrogen can still combust with very low oxygen levels.
Carbon Dioxide (CO₂)
Carbon dioxide, represented by the chemical formula \( ext{CO}_2 \), is a colorless, odorless gas found naturally in Earth's atmosphere. In firefighting, CO₂ is favored for its ability to put out flames by suffocating the fire. It acts by displacing the oxygen needed to fuel the fire and can also help in cooling the fire by absorbing heat.
Despite its effectiveness on various types of fires, \( ext{CO}_2\)is not universally applicable, particularly for fires fed by flammable gases such as hydrogen. The challenge lies in the fact that hydrogen can sustain combustion in environments where oxygen has been largely displaced by \( ext{CO}_2\), making CO₂-less effective as a suppressant in such scenarios.
Despite its effectiveness on various types of fires, \( ext{CO}_2\)is not universally applicable, particularly for fires fed by flammable gases such as hydrogen. The challenge lies in the fact that hydrogen can sustain combustion in environments where oxygen has been largely displaced by \( ext{CO}_2\), making CO₂-less effective as a suppressant in such scenarios.
Chemical Reactions
Chemical reactions involve the transformation of substances through the breaking and forming of bonds. In the case of saline hydrides reacting with water, the reaction involves the hydrogen component of the hydrides combining with water to release hydrogen gas. This is an example of a reactive metal hydride reacting with water.
In these reactions, hydrogen gas becomes the primary combustible element that can lead to fire hazards. Understanding the specifics of chemical reactions—especially those involving highly reactive ingredients like hydrides—is essential when assessing the best methods for fire suppression.
By breaking down each reaction component, it's clear that addressing the flammable output, such as hydrogen in these cases, is crucial. Knowing the nature of the products formed helps in selecting the right type of fire suppression approach, avoiding reliance on multi-purpose fire extinguishers that may not be suitable for all occasions.
In these reactions, hydrogen gas becomes the primary combustible element that can lead to fire hazards. Understanding the specifics of chemical reactions—especially those involving highly reactive ingredients like hydrides—is essential when assessing the best methods for fire suppression.
By breaking down each reaction component, it's clear that addressing the flammable output, such as hydrogen in these cases, is crucial. Knowing the nature of the products formed helps in selecting the right type of fire suppression approach, avoiding reliance on multi-purpose fire extinguishers that may not be suitable for all occasions.
