The gas leaked from a storage tank of the Union Carbide plant in Bhopal gas tragedy was :

We begin by carefully reading the statement: “The gas leaked from a storage tank of the Union Carbide plant in the Bhopal gas tragedy was …”. Our task is to recall the name of the exact chemical involved in this historical industrial disaster.

The four possibilities are:

   A. Ammonia        B. Phosgene        C. Methyl isocyanate        D. Methylamine

Now, let us recall the factual information associated with the Bhopal incident of December 2-3, 1984. The Union Carbide India Limited chemical plant stored a large quantity of a highly toxic intermediate used in the manufacture of carbamate pesticides. That intermediate was $$\text{CH}_3\text{NCO}$$, whose common name is “methyl isocyanate”. During the accident, water entered the storage tank containing this compound, causing an exothermic reaction, rapid pressure build-up, and the consequent release of a deadly cloud of $$\text{CH}_3\text{NCO}$$ gas into the atmosphere.

We verify each option one by one:

• Option A, ammonia ($$\text{NH}_3$$), is used widely in fertilizer production but was not the main toxicant in the Bhopal tragedy.

• Option B, phosgene ($$\text{COCl}_2$$), is indeed a poisonous gas historically used in warfare, yet it was not stored in the Union Carbide tank.

• Option C, methyl isocyanate ($$\text{CH}_3\text{NCO}$$), matches precisely the documented reports on the disaster.

• Option D, methylamine ($$\text{CH}_3\text{NH}_2$$), though related in name, was likewise not the gas that escaped that night.

Since only Option C aligns with the established historical and chemical facts, we select it.

Hence, the correct answer is Option C.