CDS (II) 2020 General Knowledge · Question 54 of 120

Correct — B, ammonium nitrate. About 2,750 tonnes of ammonium nitrate stored at the Port of Beirut detonated on 4 August 2020, releasing energy comparable to roughly 1.1 kilotons of TNT and making it one of the largest accidental non-nuclear explosions on record. The cargo had arrived aboard the ship MV Rhosus in November 2013, bound from Georgia to Mozambique; the vessel was found unseaworthy, the shipment was confiscated and it sat in Warehouse 12 for six years while customs officials wrote repeatedly to judges asking for it to be removed. Ammonium nitrate is an ordinary nitrogen fertiliser and quite stable in normal storage, but it is a strong oxidiser, and a large confined mass of it that is heated will detonate.

• (a)dynamite — Dynamite is nitroglycerine absorbed into an inert medium, manufactured in sticks for blasting. Nothing of the kind was stored at the port, and a warehouse of dynamite would not have been left sitting for six years as impounded cargo.
• (c)RDX — A military high explosive, also called cyclonite, used in shells and demolition charges. It is not shipped as bulk fertiliser and was not what investigators found.
• (d)mercury nitride — Not the substance involved. The mercury compound usually met in explosives work is mercury fulminate, and that is a detonator material used in very small quantities, not something stockpiled by the thousand tonnes.

Ammonium nitrate is made by neutralising nitric acid with ammonia. Most of what is produced goes into fertiliser, and the rest into commercial blasting, where it is mixed with fuel oil to make ANFO. On its own it does not burn, but it supplies oxygen readily; a large mass that is confined, contaminated with fuel or organic material, and then heated can transition from burning to detonation. That is the chain behind the Oppau disaster of 1921 and the Texas City disaster of 1947 as well as Beirut.

The question is answered by asking which of the four substances would plausibly be sitting in a port warehouse in bulk for years. Fertiliser would; military explosives would not. Anchor the casualty figures honestly: the paper, written within weeks of the blast, says about one hundred killed and a thousand wounded, which reflects the first reports. The confirmed toll settled far higher — 218 dead and more than 7,000 injured, at least 150 of them permanently disabled. Later investigation pointed to negligence by port, customs and government officials, and the inquiry has been repeatedly obstructed. The stem's phrasing, 'a blast has taken place' and 'thousand wounded', is the booklet's own wording.

• About 2,750 tonnes of ammonium nitrate detonated at the Port of Beirut on 4 August 2020.
• The blast released energy comparable to about 1.1 kilotons of TNT.
• The cargo arrived on the MV Rhosus in November 2013 and was stored in Warehouse 12 for six years.
• Confirmed casualties were 218 dead and over 7,000 injured, well above the figures the question quotes.
• Ammonium nitrate is chiefly a fertiliser and an oxidiser; mixed with fuel oil it becomes the blasting agent ANFO.

• Assuming a large explosion must involve a military explosive.
• Confusing mercury fulminate, a primary explosive, with mercury nitride.
• Quoting the casualty figures printed in the question as final; they were early estimates.

As a current-affairs cause question like this one, or as a chemistry item on which compound is used as an explosive or as a fertiliser.

• practice — not a real PYQ

  The blasting agent ANFO, widely used in mining, is a mixture of fuel oil with which one of the following?

  • (a)Ammonium nitrate
  • (b)Potassium chlorate
  • (c)Sodium azide
  • (d)Calcium carbide

  Answer(a) Ammonium nitrate — the fertiliser supplies the oxygen and the fuel oil the combustible material.

• practice — not a real PYQ

  Ammonium nitrate is manufactured by the reaction of ammonia with

  • (a)sulphuric acid
  • (b)nitric acid
  • (c)hydrochloric acid
  • (d)phosphoric acid

  Answer(b) nitric acid — ammonia with sulphuric acid would give ammonium sulphate instead.