What is/are the full form(s) of HMX? 1. High Melting Explosive 2. High-Density Monoatomic Xenon 3. Hedge Monetizing Xenocurrency 4. Her Majesty’s Explosive Select the correct answer using the codes given below.
- (a)1 and 2
- (b)2 and 3
- (c)Only 1
- (d)1 and 4
Correct — D, 1 and 4. HMX, also called octogen, is a nitroamine high explosive with the formula C4H8N8O8: an eight-membered ring of alternating carbon and nitrogen atoms carrying a nitro group on every nitrogen. Its name has never been formally settled. The standard reference work on the subject — Paul W. Cooper, Explosives Engineering (New York: Wiley-VCH, 1996) — records the letters as having been variously expanded to High Melting Explosive, High-velocity Military Explosive, High-Molecular-weight RDX and Her Majesty's Explosive. Two of those four are on this page, as items 1 and 4, and both are genuine. 'High Melting' is not a guess: HMX melts at 276–286 °C where its close relative RDX melts at 205.5 °C, and since the two compounds are made by the same Bachmann nitration of hexamine and separated only by reaction conditions, the higher-melting product needed a name that distinguished it. 'Her Majesty's Explosive' reflects the British wartime naming habit that also left RDX with two competing expansions of its own — Research Department Explosive and Royal Demolition Explosive. Items 2 and 3 are where the paper does its filtering: 'High-Density Monoatomic Xenon' names no explosive (xenon is an inert monatomic gas used in lamps, ion thrusters and anaesthesia) and 'Hedge Monetizing Xeno-currency' is not chemistry at all. The stem's own plural, 'full form(s)', is the setter telling you that more than one item is meant to survive. This is a derived answer rather than a published one, and it is the one place on this question where honesty matters: see the reasoning below for why option (c) is a live rival rather than a dead one.
- (a)1 and 2 — Item 1 is right, but item 2 is invented. 'High-Density Monoatomic Xenon' strings together real physics words — xenon is genuinely monatomic and genuinely dense for a gas — into a compound that does not exist and names no energetic material. Xenon is a chemically inert noble gas used in high-intensity lamps, in ion thrusters and as an anaesthetic; nothing about it detonates. Choosing this option means accepting a scientific-sounding phrase without first asking whether it could name an explosive at all.
- (b)2 and 3 — The only option that contains neither genuine expansion, so it is wrong twice over. It pairs the fabricated 'High-Density Monoatomic Xenon' with 'Hedge Monetizing Xeno-currency', a finance-flavoured string with no chemical meaning whatever. A candidate lands here only by having no anchor on HMX at all and being drawn to the two most exotic-sounding items on the page — which is precisely what the setter built them for.
- (c)Only 1 — The serious rival, and the reason this question is not open-and-shut. 'High Melting Explosive' is the single expansion that most Indian defence writing and general-knowledge compilations give, so an examiner working from one such source could have intended (c). What tips the page towards (d) is that 'Her Majesty's Explosive' is equally documented in the standard explosives literature, not a distractor invented for this paper, and that the stem deliberately asks for the 'full form(s)' in the plural — a construction with no purpose if exactly one item were correct.
HMX belongs to the nitroamines (nitramines), the family of secondary high explosives built around nitrogen–nitrogen nitro linkages, alongside RDX and tetryl. An energetic material of this kind carries its fuel and its oxidiser inside one molecule: the nitro groups supply the oxygen that burns the carbon and hydrogen skeleton, which is why detonation does not need air and propagates as a shock wave rather than a flame. Performance is compared on three numbers. Detonation velocity is the speed at which that shock front travels — about 6,900 m/s for TNT, 8,750 m/s for RDX and 9,100 m/s for HMX. Relative effectiveness takes TNT as 1.00, putting RDX at 1.60 and HMX at 1.70. Sensitivity decides whether a compound can be handled: HMX is rated low for both shock and friction sensitivity, which is what makes it a secondary explosive needing a detonator, and not a primary one like mercury fulminate. Because it is expensive and hard to make, HMX is reserved for jobs where the extra energy per unit volume is worth it.
Two of the four items are transparent inventions, and spotting them is the whole battle, because any option containing item 2 or item 3 dies at once. That kills (a) and (b) together and leaves a straight choice between 'Only 1' and '1 and 4' — which is where the actual knowledge is tested. The discriminating fact is that HMX has no single official expansion: the explosives literature lists four candidates and two of them are on this page. Reinforcing that reading, the stem asks for the 'full form(s)' with the plural bracketed in, and a setter who meant one answer would not write the question that way. Be honest about where this stands, though. There is no published key for this paper, and the answer here was derived rather than looked up. Both derivations reached (d), but one of them flagged the same weak link a careful student will feel: if the examiner drew on a single Indian defence article, which almost always gives only 'High Melting Explosive', the intended key could have been (c). Nothing external can settle that now, so the honest position is that (d) is the better-supported reading of the page as printed, not a certainty.
- HMX, also called octogen, is a nitroamine high explosive of formula C4H8N8O8 (molar mass 296.155 g/mol, density 1.95 g/cm³) whose molecule is an eight-membered ring of alternating carbon and nitrogen atoms with a nitro group on each nitrogen.
- The standard explosives literature (Paul W. Cooper, Explosives Engineering, Wiley-VCH, 1996) records four competing expansions of the letters HMX — High Melting Explosive, High-velocity Military Explosive, High-Molecular-weight RDX and Her Majesty's Explosive — so the name's origin is genuinely disputed rather than merely uncertain.
- HMX melts at 276–286 °C against RDX's 205.5 °C, which is what 'High Melting' points to; HMX's detonation velocity is about 9,100 m/s and its relative effectiveness factor 1.70, against RDX's 8,750 m/s and 1.60, with TNT set at 1.00 by definition.
- HMX was first made in 1930, and in 1949 Bachmann and Sheehan showed it could be prepared by nitrolysis of RDX; both compounds come out of the same Bachmann process — nitration of hexamine with ammonium nitrate and nitric acid in acetic acid and acetic anhydride — with the reaction conditions deciding which one dominates.
- Its uses are almost entirely military: detonators in nuclear weapons, polymer-bonded explosive compositions, missile warheads and armour-piercing shaped charges, melt-castable 'octols' when mixed with TNT, solid rocket propellant, and shaped charges that perforate the steel casing of oil and gas wells.
Two of the four printed items are real and two are fabricated, so the answer is 1 and 4 = option (d). The stem's bracketed plural, 'full form(s)', is the setter's signal that more than one item survives.
- Assuming an abbreviation has exactly one expansion — HMX carries four in the literature and RDX carries two, which is the whole point of this question
- Falling for a string of real technical words assembled into a fake compound; 'High-Density Monoatomic Xenon' sounds like physics and names nothing
- Reading past the bracketed plural in 'full form(s)', which is the strongest in-question clue that more than one item is intended to be correct
BPSC asks abbreviations flat and often — expand HMX here, expand PHBV in 2025, expand mRNA later in this very paper — and dresses them as multi-statement code questions where the real skill is spotting the fabricated options rather than knowing any chemistry. UPSC almost never asks for an expansion; it asks what the substance does. In 2025 it grouped CL-20, HMX and LLM-105 and asked for their common characteristic, in 2007 it wanted another name for RDX, and in 2009 it asked which listed substance is used as an explosive. Learn the compound's job and its numbers and both styles are covered.
What is the common characteristic of the chemical substances generally known as CL-20, HMX and LLM-105, which are sometimes talked about in media?
- (a) These are alternatives to hydrofluorocarbon refrigerants
- (b) These are explosives in military weapons
- (c) These are high-energy fuels for cruise missiles
- (d) These are fuels for rocket propulsion
Answer(b) These are explosives in military weapons
The same compound, two years later and from the other direction: BPSC wants the letters expanded, UPSC wants to know what HMX actually is — a military high explosive, grouped with the newer energetic materials CL-20 and LLM-105.
Which one of the following is another name of RDX?
- (a) Cyanohydrin
- (b) Dextran
- (c) Cyclohexane
- (d) Cyclonite
Answer(d) Cyclonite
Naming conventions in the same chemical family: RDX is HMX's close relative, made by the same Bachmann process, and carries the same problem of multiple names — Cyclonite, hexogen, Research Department Explosive, Royal Demolition Explosive.
- practice — not a real PYQ
HMX and RDX are both classified as
- (a)primary explosives
- (b)nitroamine (nitramine) secondary high explosives
- (c)low explosives used as propellants
- (d)blasting agents that cannot be detonated by a booster
Answer(b) nitroamine (nitramine) secondary high explosives — both are ring nitramines of low shock and friction sensitivity that need a detonator, unlike primary explosives such as mercury fulminate or lead azide.
- practice — not a real PYQ
Which one of the following is another name for HMX?
- (a)Hexogen
- (b)Cyclonite
- (c)Octogen
- (d)Tetryl
Answer(c) Octogen — hexogen and cyclonite are both alternative names for RDX, and tetryl (2,4,6-trinitrophenylmethylnitramine) is a separate nitramine used as a booster charge.