---
title: "Primary and low explosives; TNT and TNG"
subject: "Engineering Chemistry"
chapter: 7
key: "semester_2/engineering_chemistry:primary-low-tnt-tng"
source: https://www.bctengineer.com/q/semester_2/engineering_chemistry/primary-low-tnt-tng
site: BCT Engineering
---

# Primary and low explosives; TNT and TNG

Engineering Chemistry · Chapter 7: Explosives

- Asked in: 2069 Bhadra, 5 marks
- Video: [Classification of EXPLOSIVES & TNT mixtures](https://www.youtube.com/watch?v=A0_p38PmpBU) — Savvy Forensics
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_2/engineering_chemistry/primary-low-tnt-tng
- Whole chapter: https://www.bctengineer.com/md/semester_2/engineering_chemistry/chapter-7

## Question

Mention the importance of primary and low explosives. Give the preparation and uses of TNT and TNG.

## Short answer

Primary explosives (lead azide) are crucial in detonators to initiate secondary charges; low explosives (black powder) provide propelling force for guns, rockets, and soft blasting. TNT is made by nitrating toluene with HNO₃/H₂SO₄ and used in shells, bombs, mining. TNG (nitroglycerine) is made by nitrating glycerol below 15°C and used in dynamite, cordite, and as a medicine.

## Answer

#### Importance
- **Primary explosives** (lead azide, mercury fulminate) are essential in detonators and primers, because they explode easily and start the main charge of safer high explosives.
- **Low explosives** (black powder, smokeless powder) are valuable as propellants in guns and rockets, in fireworks, safety fuses, and for blasting soft rocks and coal where shattering is unwanted.

#### TNT
Prepared by nitration of toluene with conc. HNO₃ and conc. H₂SO₄ in three stages (30 °C, 60 °C, 100–110 °C):
C₆H₅CH₃ + 3HNO₃ → C₆H₂(CH₃)(NO₂)₃ + 3H₂O
Uses: shells, bombs, mining and demolition.

#### TNG (glycerol trinitrate)
Prepared by adding glycerol to conc. HNO₃ + conc. H₂SO₄ below 10–15 °C:
C₃H₅(OH)₃ + 3HNO₃ → C₃H₅(ONO₂)₃ + 3H₂O
Uses: dynamite, gelignite, cordite, blasting, and angina medicine.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Why are primary explosives important?
   A. They are the safest main charge
   B. They are propellants
   C. They are used for slow blasting only
   D. They are essential in detonators and primers to start the main charge of safer high explosives
   Answer: D. They explode easily and initiate secondary explosives. (Key point: Importance of primary)

2. Where are low explosives valuable?
   A. Shattering granite
   B. As propellants, in fireworks and safety fuses, and for blasting soft rock where shattering is unwanted
   C. In detonators
   D. As main shell charge
   Answer: B. Deflagration gives propelling effect. (Key point: Importance of low)

3. How is TNT formed from toluene?
   A. In one step at 0 C
   B. By reducing toluene with H2 and then adding HNO3 once
   C. By oxidising toluene with KMnO4
   D. In three stages of nitration at rising temperatures (about 30, 60, then 100-110 C)
   Answer: D. Nitration goes through mono-, di- and finally trinitrotoluene, with higher temperature and oleum for the last stage. (Key point: Stepwise nitration)

4. How is TNG prepared?
   A. Heating glycerol with dilute HNO3
   B. Mixing glycerol with HCl at 100 C
   C. Adding glycerol to conc. HNO3 + conc. H2SO4 below 10-15 C
   D. Adding toluene to HNO3
   Answer: C. C3H5(OH)3 + 3HNO3 gives C3H5(ONO2)3 + 3H2O with cooling. (Key point: TNG preparation)

## Related in Engineering Chemistry

- [High and low explosives; TNT preparation](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Ahigh-low-explosives-tnt) — Engineering Chemistry, chapter 7, asked 3×
- [Primary and low explosives; glycerol trinitrate](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Aprimary-low-explosives-gtn) — Engineering Chemistry, chapter 7
- [Explosive characteristics; TNT preparation and uses](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Aexplosive-characteristics-tnt) — Engineering Chemistry, chapter 7
- [Low explosives and uses; glycerol trinitrate](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Alow-explosives-gtn) — Engineering Chemistry, chapter 7
- [Low and high explosives; GTN preparation](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Ahigh-low-gtn) — Engineering Chemistry, chapter 7, asked 2×
- [High vs plastic explosives; TNT](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Ahe-vs-plastic-tnt) — Engineering Chemistry, chapter 7