Ammonium Nitrate: Structure, Preparation, Properties, Uses

Edited By Team Careers360 | Updated on Jul 02, 2025 05:14 PM IST

Ammonium nitrate is defined as an ionic salt which is made up of the ammonium cation and the nitrate anion .

Chemical Name

The chemical name of Ammonium Nitrate is .

Structure Of Ammonium Nitrate

Ammonium nitrate compounds have many features as an ionic bond between an ammonium ion and a nitrate ion.

The pi electrons in the nitrate ion are delocalized due to resonance and the net charge on this ion is -1 (because the nitrogen atom holds a charge of +1 and each oxygen atom holds a charge of -⅔). Thus, only one ion can form an ionic bond with one ion.

Chemical Data

Chemical Formula is
Molar Mass/ Molecular Weight is 80.043 grams per mole
Density is 1.725 grams per cubic centimetre
Melting Point (MP) is 442.8K (169.6oC)
Boiling Point(BP) decomposes at 483K (210oC)

This Story also Contains

Chemical Name
Structure Of Ammonium Nitrate
Chemical Data
Preparation Of Ammonium Nitrate
Ammonium Nitrate Properties
Uses Of Ammonium Nitrate

Ammonium Nitrate: Structure, Preparation, Properties, Uses

Preparation Of Ammonium Nitrate

Ammonium nitrate which is commonly known as readily dissolves in water by dissociating into its constituent ions. This salt is acidic because it is derived from a weak base that is and a strong acid that is .

Ammonium nitrate can be prepared from the acid-base reaction between nitric acid and ammonia which is described by the following chemical equation:

The above-given reaction is highly exothermic and proceeds violently. It is also known for its oxidizing powers and is widely used in many explosives used in the mining and construction sectors. NH4NO3 is the key component of ANFO, which is one of the most popular choices for industrial explosives.

Ammonium Nitrate Properties

Physical Properties

Ammonium nitrate is a crystalline solid having a white colour.
Ammonium nitrate has a trigonal crystal structure.
Ammonium nitrate is quite soluble in water and its solubility at 20oC is 150g/100ml. The solubility increases to 1024g/100ml when the temperature is raised to 100 degrees.
The dissolution of Ammonium nitrate (NH4NO3) in H2O is highly endothermic.
Ammonium nitrate has very low shock and friction sensitivities.

Chemical Properties

When Ammonium nitrate (NH4NO3 ) is reacted with the hydroxides of alkali metals then the nitrates of alkali metals are formed along with ammonia.
While heating, this compound decomposes to form nitrous oxide (N2O) and water.
And when exploded, this compound yields N2, O2, and water as the by-products.
Despite being a component of many explosives, ammonium nitrate is not an explosive by itself because it must be mixed with a primary explosive like azide to form an explosive mixture.

Uses Of Ammonium Nitrate

Some applications of this ionic salt are given below.

Ammonium nitrate (NH4NO3) is a key component of many fertilizers because it is quite rich in nitrogen (34%).
This compound does not lose its nitrogen to the atmosphere, as is the case with urea.
And when mixed with fuel oil, it forms an explosive which is known as ANFO. It is one of the most popular industrial explosives.
The dissolution of this compound in water is quite endothermic due to it makes an ideal choice of material in instant cold packs.
Ammonium nitrate is also used in the mining and construction industry as a component of explosives.

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Frequently Asked Questions (FAQs)

1. Is ammonium nitrate an acid?

Ammonium nitrate is not an acid but a salt because the solution is acidic since it is a salt with a weak base (ammonium hydroxide) and a heavy nitric acid.

2. What does ammonium nitrate react with?

Ammonium nitrate is sensitive when it is mixed with titanium, tin, or aluminium.

3. What happens if we breathe ammonium?

Due to exposure to high concentrations of ammonia in the air, can cause immediate burning of the eyes, nose, throat and respiratory tract that can result in blindness, lung damage or death.

4. At what temperature does ammonium nitrate explode?

At 400 degrees Fahrenheit temperature ammonium nitrate explodes.

5. What is the formula of ammonium nitrate?

The formula of ammonium nitrate is NH4NO3.

6. Why is ammonium nitrate considered an ionic compound?

Ammonium nitrate is considered an ionic compound because it is composed of positively charged ammonium ions (NH4+) and negatively charged nitrate ions (NO3-) held together by electrostatic forces.

7. How does the structure of ammonium nitrate contribute to its properties?

The ionic structure of ammonium nitrate contributes to its high solubility in water, its ability to absorb moisture from the air (hygroscopic nature), and its tendency to decompose at high temperatures.

8. What is the crystal structure of ammonium nitrate at room temperature?

At room temperature, ammonium nitrate typically exists in a tetragonal crystal structure. However, it's important to note that ammonium nitrate can undergo several phase transitions at different temperatures.

9. How does temperature affect the crystal structure of ammonium nitrate?

Ammonium nitrate undergoes several phase transitions as temperature changes. It has five different polymorphs (crystal structures) between -18°C and 125°C. These transitions can affect its properties and stability, which is crucial for its storage and use.

10. What is the melting point of ammonium nitrate?

The melting point of ammonium nitrate is approximately 170°C (338°F). However, it's important to note that ammonium nitrate can decompose before reaching this temperature, especially if heated rapidly or in the presence of contaminants.

11. What is the chemical formula of ammonium nitrate?

The chemical formula of ammonium nitrate is NH4NO3. It consists of one ammonium ion (NH4+) and one nitrate ion (NO3-).

12. Why is ammonium nitrate highly soluble in water?

Ammonium nitrate is highly soluble in water due to its ionic nature. The water molecules can easily surround and separate the ammonium (NH4+) and nitrate (NO3-) ions, breaking the ionic bonds and dissolving the compound.

13. What makes ammonium nitrate an effective component in explosives?

Ammonium nitrate is an effective component in explosives due to its chemical composition. It contains both a fuel (ammonium) and an oxidizer (nitrate) in a single compound. When rapidly heated or detonated, it decomposes to release a large volume of gases and energy.

14. How does the endothermic dissolution of ammonium nitrate work?

When ammonium nitrate dissolves in water, it requires energy to break the ionic bonds between the NH4+ and NO3- ions. This energy is absorbed from the surroundings, resulting in a temperature decrease. The equation is: NH4NO3 + H2O + heat → NH4+ (aq) + NO3- (aq).

15. How does the decomposition of ammonium nitrate occur?

Ammonium nitrate decomposes when heated, following the reaction: NH4NO3 → N2O + 2H2O. At higher temperatures or with rapid heating, it can decompose more violently: 2NH4NO3 → 2N2 + O2 + 4H2O. This decomposition releases a large volume of gases, which is the basis for its explosive properties.

16. How is ammonium nitrate typically prepared in industrial settings?

Ammonium nitrate is typically prepared industrially by reacting ammonia (NH3) with nitric acid (HNO3). This neutralization reaction produces ammonium nitrate and water: NH3 + HNO3 → NH4NO3 + H2O.

17. Why is the preparation of ammonium nitrate considered an acid-base reaction?

The preparation of ammonium nitrate is considered an acid-base reaction because it involves the neutralization of a base (ammonia, NH3) with an acid (nitric acid, HNO3), resulting in the formation of a salt (ammonium nitrate) and water.

18. What safety precautions are necessary when handling ammonium nitrate?

Safety precautions for handling ammonium nitrate include: storing it away from combustible materials, avoiding contamination, ensuring proper ventilation, preventing exposure to high temperatures, and keeping it dry. Proper education and adherence to regulations are crucial due to its potential for misuse in explosives.

19. Why is ammonium nitrate sometimes mixed with calcium carbonate in fertilizers?

Ammonium nitrate is sometimes mixed with calcium carbonate (limestone) in fertilizers to create calcium ammonium nitrate. This mixture helps to counteract the soil-acidifying effects of ammonium nitrate and provides calcium as an additional nutrient for plants.

20. How does ammonium nitrate contribute to the nitrogen cycle?

Ammonium nitrate contributes to the nitrogen cycle by providing nitrogen in forms that can be readily used by plants (NH4+ and NO3-). As plants absorb these ions, they incorporate the nitrogen into organic compounds. The nitrogen is then cycled through the ecosystem as plants are consumed or decompose.

21. How does the solubility of ammonium nitrate change with temperature?

The solubility of ammonium nitrate increases significantly with temperature. This property is important in its use as a fertilizer and in cold packs, where its endothermic dissolution process is utilized.

22. What is the primary use of ammonium nitrate?

The primary use of ammonium nitrate is as a nitrogen-rich fertilizer in agriculture. It provides both ammonium (NH4+) and nitrate (NO3-) ions, which are important sources of nitrogen for plant growth.

23. How does ammonium nitrate function as a fertilizer?

As a fertilizer, ammonium nitrate provides nitrogen in two forms: ammonium (NH4+) and nitrate (NO3-). Plants can directly absorb the nitrate, while the ammonium is converted to nitrate in the soil. This dual-form nitrogen supply allows for both immediate and sustained nutrient release.

24. Why is ammonium nitrate considered a "complete" fertilizer?

Ammonium nitrate is considered a "complete" fertilizer because it provides nitrogen in both the ammonium (NH4+) and nitrate (NO3-) forms. This allows for both immediate uptake by plants (nitrate) and a more sustained release of nitrogen as soil bacteria convert ammonium to nitrate over time.

25. What is the significance of ammonium nitrate being hygroscopic?

Ammonium nitrate's hygroscopic nature means it readily absorbs moisture from the air. This property is important for its use in fertilizers, as it can help deliver water to plants, but it also requires careful storage to prevent caking and maintain its effectiveness.

26. What is the environmental impact of using ammonium nitrate as a fertilizer?

While ammonium nitrate is an effective fertilizer, its overuse can lead to environmental issues such as soil acidification, groundwater contamination, and eutrophication of water bodies. Proper application techniques and amounts are crucial to minimize these impacts.

27. How does ammonium nitrate affect soil pH?

Ammonium nitrate can potentially lower soil pH over time. This occurs because as plants absorb the ammonium ions (NH4+), they release hydrogen ions (H+) into the soil, which can increase soil acidity. Regular soil testing and liming may be necessary to maintain optimal pH levels.

28. What is the role of ammonium nitrate in instant cold packs?

In instant cold packs, ammonium nitrate is used because its dissolution in water is an endothermic process, meaning it absorbs heat from the surroundings. When the pack is activated, the ammonium nitrate dissolves in water, creating a cooling effect.

29. How does the presence of ammonium nitrate affect the freezing point of water?

Ammonium nitrate, when dissolved in water, lowers its freezing point. This is due to the colligative properties of solutions, where the presence of dissolved ions interferes with the formation of ice crystals. This property is utilized in some de-icing applications.

30. What is the difference between ammonium nitrate and urea as nitrogen fertilizers?

While both are nitrogen fertilizers, ammonium nitrate provides nitrogen in both nitrate (NO3-) and ammonium (NH4+) forms, allowing for immediate and sustained nitrogen release. Urea (CO(NH2)2) must first be converted to ammonium by soil enzymes before plants can use it, leading to a slower initial but longer-lasting effect.

31. How does ammonium nitrate compare to other nitrogen fertilizers in terms of nitrogen content?

Ammonium nitrate has a high nitrogen content of about 34% by weight, split equally between ammonium and nitrate forms. This is higher than many other common nitrogen fertilizers like urea (46% N) or ammonium sulfate (21% N), making it an efficient source of nitrogen.

32. What happens to ammonium nitrate when it's applied to soil?

When applied to soil, ammonium nitrate quickly dissolves due to its high solubility. The nitrate ions (NO3-) are immediately available for plant uptake, while the ammonium ions (NH4+) can be absorbed by plants or converted to nitrate by soil bacteria through nitrification.

33. How does temperature affect the storage of ammonium nitrate?

Temperature significantly affects ammonium nitrate storage. High temperatures can cause it to decompose, potentially leading to dangerous situations. It should be stored in a cool, well-ventilated area away from sources of heat. Temperature cycling can also lead to caking, affecting its quality as a fertilizer.

34. What is "caking" in the context of ammonium nitrate, and why is it a concern?

Caking refers to the formation of hard lumps or a solid mass of ammonium nitrate, often due to moisture absorption and temperature fluctuations during storage. It's a concern because it can make the fertilizer difficult to apply evenly and may affect its dissolution rate in soil.

35. How does the nitrogen release pattern of ammonium nitrate differ from slow-release fertilizers?

Ammonium nitrate provides a quick release of nitrogen compared to slow-release fertilizers. Its nitrate component is immediately available to plants, while the ammonium portion is quickly converted to nitrate in soil. Slow-release fertilizers, in contrast, release nitrogen gradually over an extended period.

36. What role does ammonium nitrate play in the production of nitrous oxide (N2O)?

Ammonium nitrate can contribute to nitrous oxide (N2O) emissions, a potent greenhouse gas. This occurs through denitrification processes in soil, where nitrate is converted to N2O by microorganisms, especially in waterlogged or compacted soils with low oxygen levels.

37. How does the presence of ammonium nitrate affect soil microbial activity?

Ammonium nitrate can significantly impact soil microbial activity. The influx of readily available nitrogen can stimulate microbial growth and activity. However, long-term use may alter the microbial community structure, potentially affecting soil health and nutrient cycling.

38. What is the concept of "nitrogen use efficiency" and how does it relate to ammonium nitrate?

Nitrogen use efficiency (NUE) refers to the proportion of applied nitrogen that is actually taken up and used by plants. Ammonium nitrate generally has a high NUE due to its readily available nitrogen forms, but proper application timing and rates are crucial to maximize efficiency and minimize environmental losses.

39. How does ammonium nitrate interact with other nutrients in the soil?

Ammonium nitrate can interact with other nutrients in the soil. For example, the ammonium ions can compete with other cations like potassium, calcium, and magnesium for uptake by plants. Additionally, the nitrate form can enhance the uptake of cations due to the plant's need to maintain charge balance.

40. What is the "prilling" process in the production of ammonium nitrate?

Prilling is a process used in the production of ammonium nitrate fertilizer. It involves spraying molten ammonium nitrate from the top of a tall tower. As the droplets fall, they cool and solidify into small, round pellets called prills. This form improves handling and application of the fertilizer.

41. How does the particle size of ammonium nitrate prills affect its effectiveness as a fertilizer?

The particle size of ammonium nitrate prills affects its dissolution rate and distribution in soil. Smaller prills dissolve more quickly and can be distributed more evenly, but may be more prone to caking. Larger prills dissolve more slowly but are easier to handle and spread.

42. What is the significance of the ammonium to nitrate ratio in ammonium nitrate?

The 1:1 ratio of ammonium to nitrate in ammonium nitrate is significant because it provides a balance between immediate (nitrate) and slightly delayed (ammonium) nitrogen availability. This ratio helps in maintaining a steady supply of nitrogen to plants over a short period.

43. How does ammonium nitrate affect plant root development?

Ammonium nitrate can significantly influence root development. The nitrate form promotes lateral root growth, while the ammonium form can stimulate root hair development. However, excessive amounts can inhibit root growth, emphasizing the importance of proper application rates.

44. What is the role of ammonium nitrate in the nitrogen assimilation process in plants?

In nitrogen assimilation, plants can directly utilize the nitrate (NO3-) from ammonium nitrate in the production of amino acids and other organic compounds. The ammonium (NH4+) is also used, but it must first be incorporated into organic compounds in the roots to avoid toxicity.

45. How does soil texture affect the behavior of ammonium nitrate when applied as a fertilizer?

Soil texture significantly affects how ammonium nitrate behaves when applied. In sandy soils, the highly soluble nitrate can leach quickly, potentially leading to groundwater contamination. In clay soils, ammonium ions can be held more tightly, potentially reducing immediate availability but also reducing leaching.

46. What is the concept of "luxury consumption" in relation to ammonium nitrate fertilization?

Luxury consumption refers to the uptake of nutrients by plants in excess of their immediate growth requirements. With ammonium nitrate, plants may absorb more nitrogen than needed when it's readily available, which can lead to inefficient fertilizer use and potential environmental issues if not managed properly.

47. How does ammonium nitrate compare to organic nitrogen sources in terms of environmental impact?

Ammonium nitrate, being a synthetic fertilizer, can have a more immediate environmental impact due to its high solubility and rapid availability. Organic nitrogen sources release nutrients more slowly, potentially reducing leaching and runoff. However, proper management of ammonium nitrate can mitigate many environmental concerns.

48. What is the role of nitrification inhibitors when used with ammonium nitrate?

Nitrification inhibitors are sometimes used with ammonium nitrate to slow the conversion of ammonium to nitrate in the soil. This can reduce nitrogen losses through leaching and denitrification, potentially improving nitrogen use efficiency and reducing environmental impacts.

49. How does the electrical conductivity of soil change with the application of ammonium nitrate?

The application of ammonium nitrate increases the electrical conductivity of soil due to the addition of ions (NH4+ and NO3-). This increase in conductivity can affect soil microbial activity and plant nutrient uptake, and in high concentrations, may lead to salt stress in plants.

50. What is the concept of "split application" in the context of ammonium nitrate fertilization?

Split application refers to the practice of applying ammonium nitrate (or other fertilizers) in multiple smaller doses throughout the growing season rather than all at once. This approach can improve nitrogen use efficiency, reduce leaching losses, and better match the plant's nitrogen demand over time.

51. How does ammonium nitrate affect the carbon-to-nitrogen ratio in soil?

Ammonium nitrate application lowers the carbon-to-nitrogen ratio in soil by increasing the nitrogen content. This can stimulate microbial activity and organic matter decomposition, potentially leading to a temporary decrease in soil organic carbon if not managed properly.

52. What is the significance of the "critical relative humidity" for ammonium nitrate storage?

The critical relative humidity for ammonium nitrate is about 59% at 30°C. Above this humidity, it will absorb moisture from the air, potentially leading to caking and degradation. Understanding this property is crucial for proper storage and handling to maintain fertilizer quality.

53. How does ammonium nitrate interact with pesticides when used in agricultural settings?

Ammonium nitrate can interact with pesticides in several ways. It may affect the soil pH, potentially altering the effectiveness or degradation rate of certain pesticides. The increased plant growth from nitrogen application may also influence pest populations and the need for pest management.