Chemical Engineering - Chemical Engineering Basics - Discussion

Among the options given, the incombustible substance is CCl4 (carbon tetrachloride).

Here’s why;

-> H2 (hydrogen gas) is highly combustible and burns with a pale blue, almost invisible flame.

-> C2H2 (acetylene) is also highly combustible and is often used as a fuel in welding torches.

-> S (sulfur) is combustible and burns with a blue flame, producing sulfur dioxide.

-> CCl4 (carbon tetrachloride), on the other hand, does not support combustion and is used as a fire extinguishing agent and in other applications where non-flammability is required.

CCl4 (carbon tetrachloride), on the other hand, does not support combustion and is used as a fire extinguishing agent and in other applications where non-flammability is required.

Consider the combustion of a simple molecule methane CH4:

CH4 + 2O2 = CO2 + 2H2O.

However, if we consider a similar molecule CCl4, carbon tetrachloride, which is just a replacement of H by Cl in methane, is incombustible.

This can be explained by observing the reaction above. CH4 burns to give CO2 and Water. Hydrogen being an electropositive element joins oxygen quickly.

However, chlorine being an electronegative element would like to connect to an electropositive element carbon, as it can pull the electron pair closer to itself!

Getting Cl in +1 state is difficult.

So the reaction
CCl4 + 2O2 = CO2 + 2Cl2O is least probable.

Because it doesn't combust, it was used as a fire extinguisher under the name pyrene.

Since both, chlorine and oxygen, are electronegative elements therefore the combustion reaction CCl4 + 2 O2 ---> CO2 + 2 Cl2O doesn't take place.

H2 is combustable too.

Among the options given, the incombustible substance is CCl4 (carbon tetrachloride).

Here’s why;

-> H2 (hydrogen gas) is highly combustible and burns with a pale blue, almost invisible flame.

-> C2H2 (acetylene) is also highly combustible and is often used as a fuel in welding torches.

-> S (sulfur) is combustible and burns with a blue flame, producing sulfur dioxide.

-> CCl4 (carbon tetrachloride), on the other hand, does not support combustion and is used as a fire extinguishing agent and in other applications where non-flammability is required.

Because CCl4 does not have free (delocalized) electrons as does a metal or something like graphite. Nor does CCl4 ionize in solution to form ions. It is a nonelectrolyte.

The molecular formula of carbon tetrachloride is CCl4. It is a tetrachloro derivative of methane. Its IUPAC name is tetrachloromethane and it doesn't burn.

Incombustible means?

CCl4 is incombustible because the combustion products will have higher energy content than that of the reactants. For combustion to take place, the products should contain stable compounds (lower energy content) eg. H2O, CO2 etc. Than that of the reactants. CCl4 is very stable due to its structure.