Confirmation for Chromyl Chloride Test

Chromyl chloride is a chemical compound known by the chemical name CrO2Cl2. They are tetrahedral and appear as dark red blood. Mostly they are made of chromium as an initial derivative.

It works as an oxidising agent and is found to exhibit oxidation properties to oxidise toluene into Benzaldehyde. 

Confirmation for Chromyl Chloride Test

One of the most basic methods to prepare chromyl chloride includes the reaction of chemical compounds such as potassium chromate or potassium dichromate with an acid such as hydrochloric acid. This reaction usually takes place in the presence of sulphuric acid. The resultant formed by the chemical reaction goes through distillation and can be purified. The presence of sulphuric acid during this process is necessary because it acts as a dehydrating agent. 

Another method is by exposing chromium trioxide to hydrogen chloride present in the gaseous form. The method of forming chromyl chloride can also be used to detect chloride in any chemical substance. If the chemical compound contains chloride as one of its constituents, it’ll release red fumes, affirming the presence of chloride. 

Chloride chromyl test:

Requirements: Sulphuric acid, dilute acetic acid, powdered potassium dichromate, sodium hydroxide, salt, lead acetate, spatula, bunsen burner, test tube, test tube holder, dropper, and glass rod.

Procedure: 

Follow the given steps to conduct a chromyl chloride test on the given sample.

• Add a little potassium dichromate in a small quantity of salt, and mix it well. 
• With the help of a dropper, drop a small amount of sulphuric acid in a test tube.
• Heat the test tube carefully.
• Heat up till red fumes are visible from the test tube.
• Once red fumes start coming out, collect them using another test tube.
• Add sodium hydroxide to the tube that contains red fumes.
• Allow reacting.
• A yellow solution will be formed, indicating the formation of sodium chromate.
• Add dilute acetic acid followed by lead acetate.
• Allow reacting. 
• Yellow precipitates indicate the reaction is complete.

Precautions:

• As the experiment involves handling fumes, proper care should be taken to avoid burns. 
• Avoid contact of chromyl chloride with eyes and sensitive areas.
• It is to be noted that chromyl chloride is highly carcinogenic, so care must be taken.
• Must be stored in a glass jar.
• Some reactions may involve the evolution of heat, so be careful during such reactions.

Chromyl chloride test reaction mechanism:

• Potassium dichromate, when reacted with sulphuric card, yields chromium trioxide. Chromate trioxide is a dark reddish-brown coloured compound.

K2Cr2O7 + H­2SO4 → CrO3 + H2O

• Next, sodium chloride is reacted with sulphuric acid to yield sodium bisulphate and hydrochloric acid.

NaCl +H2SO4 → NaHSO­4 +HCl

• In the final step, Chromate trioxide is allowed to react with hydrochloric acid that yields chromyl chloride.

CrO3 + HCl → CrO2Cl2

Confirmatory test for chromyl chloride test:

For the confirmation purpose, sodium hydroxide is used to let the red vapour get dissolved into it. This is marked by the conversion and formation of yellow coloured compound

CrO2Cl2 + NaOH → Na2CrO4 + NaCl +H2O

This is further treated with lead acetate and dilute acetic acid, forming a yellow precipitate.

CrO42- + Pb(CH3COO)2 → PbCrO4 +CH3COONa

The formation of yellow precipitate means the test is successful.

Conclusion

Chromyl chloride is a chemical compound that is highly volatile when present in its liquid form at room temperature. It is not explosive itself, but it helps in enhancing the combustion of other chemicals. It is dark red in colour and produces poisonous fumes. It is highly oxidative in nature and has a high electron affinity with a low boiling and melting point. It is hazardous to humans and can cause acute and chronic effects if contacted with the human body. It can also cause chromosomal aberrations and can even cause cancer.