Ammonium Dichromate: General, Physical, Chemical Properties, Uses, FAQs

Edited By Team Careers360 | Updated on Jul 02, 2025 05:17 PM IST

Ammonium dichromate is an inorganic compound. It is flammable in nature . It has the chemical formula (NH4)2Cr2O7. Ammonium dichromate is an orange-red needle formed during crystallization. Toxic chemical salts are used to sensitize organic emulsions such as gelatin to the hardening effects of actinic radiation. It is very sensitive to light. Let's see the name of ammonium dichromate -diammonium dichromate ammonium bichromate; ammonium pyrochromate.

This Story also Contains

General properties of ammonium dichromate- (NH4)2Cr2O7
Physical Properties of Ammonium Dichromate- (NH4)2Cr2O7
Chemical Properties of Ammonium Dichromate- (NH4)2Cr2O7
Uses of Ammonium Dichromate- (NH4)2Cr2O7
Hazards and Safety of Ammonium Dichromate- (NH4)2Cr2O7
Oxidation Reactions- (NH4)2Cr2O7

General properties of ammonium dichromate- (NH4)2Cr2O7

Ammonium dichromate has a density of 2.12 g/cm³.
Ammonium dichromate has a molecular weight of 252.07 g/mol.
Ammonium dichromate has a spontaneous ignition temperature of 190 °C.
The melting point of ammonium dichromate is 180 °C.
The chemical formula for ammonium dichromate is (NH4)2Cr2O7.

Physical Properties of Ammonium Dichromate- (NH4)2Cr2O7

Odorless
Its appearance is an orange-red crystal.
Stable under recommended storage conditions.
Ammonium dichromate has a specific gravity of 2.1500.
It is not soluble in acetone.
It is soluble in alcohol.

Chemical Properties of Ammonium Dichromate- (NH4)2Cr2O7

At room temperature and pressure, it is an orange acidic crystal, soluble in water and alcohol. Ammonium dichromate decomposes on heating to produce chromium(III) oxide and nitrogen gas.

Uses of Ammonium Dichromate- (NH4)2Cr2O7

Ammonium dichromate sensitizes solutions that are used in lithography.
It has it’s application in pyrotechnics, lithography and photoengraving.
It is used as a magnetic recording material.
It has it’s application as an approved pesticide .
It is a mordant for dyeing.
It has it’s application as a pigment.

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Hazards and Safety of Ammonium Dichromate- (NH4)2Cr2O7

The main hazards of Ammonium Dichromate are:

Toxic
Oxidising
Dangerous for environment
Mutagen

Safety precautions must be taken to deal with these hazards.

Safety: Like all chromium (VI) compounds, ammonium dichromate is highly toxic and explosive under certain conditions.

Safety precautions should be taken when using ammonium dichromate.

Wear safety glasses and avoid skin contact with ammonium dichromate (wear gloves).

Oxidation Reactions- (NH4)2Cr2O7

Ammonium dichromate acts as an oxidizing agent. Often reacts violently with reducing agents. The greater the influence of the reducing agent, the more violent the reaction. This compound is also used in the oxidation of fatty alcohols. It is used for the corresponding aldehydes and ketones in ZrCl4/wet SiO2 under solvent-free conditions. This occurs at relatively high yields.Reaction: Consists of tabletop volcano and pyrolysis.When a small pile of ammonium dichromate is ignited with a few drops of ethanol, it can be seen that a spark is generated and an ash-like product is formed. This phenomenon resembles a volcanic eruption.

Frequently Asked Questions (FAQs)

1. What is Ammonium dichromate-(NH4)2Cr2O7?

Ammonium dichromate- (NH4)2Cr2O7 is an inorganic compound . It is flammable in nature . It has the chemical formula (NH4)2Cr2O7. Ammonium dichromate is an orange-red needle formed during crystallization. Toxic chemical salts are used to sensitize organic emulsions such as gelatin to the hardening effects of actinic radiation.It is very sensitive to light. Let's see the name of ammonium dichromate-diammonium dichromate; ammonium bichromate; ammonium pyrochromate.

2. What are the General properties of ammonium dichromate- (NH4)2Cr2O7?

The General properties of ammonium dichromate- (NH4)2Cr2O7 are -

Ammonium dichromate has a density of 2.12 g/cm³.
Ammonium dichromate has a molecular weight of 252.07 g/mol.
Ammonium dichromate has a spontaneous ignition temperature of 190 °C.
The melting point of ammonium dichromate is 180 °C.

The chemical formula for ammonium dichromate is (NH4)2Cr2O7.

3. What are the Physical Properties of Ammonium Dichromate- (NH4)2Cr2O7?

The Physical properties of ammonium dichromate- (NH4)2Cr2O7 are -

Odorless
Its appearance is an orange-red crystal.
Stable under recommended storage conditions.
Ammonium dichromate has a specific gravity of 2.1500.
It is not soluble in acetone.

4. What are the Chemical Properties of Ammonium Dichromate- (NH4)2Cr2O7?

The Chemical properties of ammonium dichromate- (NH4)2Cr2O7 are -

At room temperature and pressure, it is an orange acidic crystal, soluble in water and alcohol. Ammonium dichromate decomposes on heating to produce chromium(III) oxide and nitrogen gas.

5. What are the Hazards of Ammonium Dichromate-(NH4)2Cr2O7?

The hazards of ammonium dichromate- (NH4)2Cr2O7 are -

Toxic
Oxidising
Dangerous for environment
Mutagen

6. How does ammonium dichromate behave in acidic and basic solutions?

In acidic solutions, ammonium dichromate maintains its orange color due to the stability of the dichromate ion in acidic conditions. In basic solutions, it converts to the yellow chromate ion (CrO4^2-), changing the solution color from orange to yellow.

7. How does the presence of ammonium ions affect the properties of ammonium dichromate?

The ammonium ions in ammonium dichromate contribute to its high solubility in water and its ability to decompose at relatively low temperatures. They also make the compound less stable compared to other dichromates, such as potassium dichromate.

8. How does pH affect the stability of ammonium dichromate solutions?

Ammonium dichromate solutions are most stable in acidic conditions. In basic solutions, the dichromate ion converts to the chromate ion, changing the color from orange to yellow. In strongly basic conditions, chromium can precipitate as chromium(III) hydroxide.

9. How does ammonium dichromate interact with organic compounds?

Ammonium dichromate is a strong oxidizing agent and can react vigorously with many organic compounds. It can oxidize alcohols to aldehydes or ketones, and in some cases, it can completely oxidize organic molecules to carbon dioxide and water.

10. What happens when ammonium dichromate reacts with reducing agents?

When ammonium dichromate reacts with reducing agents, the chromium is reduced from its +6 oxidation state to lower states, typically +3. This is often accompanied by a color change from orange to green or blue, depending on the specific reaction conditions.

11. What is the significance of the ammonium ion in ammonium dichromate?

The ammonium ion (NH4+) in ammonium dichromate contributes to its high solubility in water and its ability to decompose at relatively low temperatures. It also makes the compound less stable compared to other dichromates, influencing its reactivity and applications.

12. How does the presence of ammonium dichromate affect the pH of a solution?

A solution of ammonium dichromate is slightly acidic. The ammonium ion can act as a weak acid, releasing protons in solution. Additionally, the dichromate ion can undergo hydrolysis, further contributing to the acidic nature of the solution.

13. How does the solubility of ammonium dichromate change with temperature?

The solubility of ammonium dichromate in water increases with temperature. This positive temperature coefficient of solubility is typical for many ionic compounds and is due to the endothermic nature of the dissolution process.

14. How does ammonium dichromate interact with transition metal ions?

Ammonium dichromate can form complex ions with various transition metal ions. These interactions can result in color changes or precipitation reactions, which are useful in qualitative analysis for identifying specific metal ions in solution.

15. How does the reactivity of ammonium dichromate compare with that of chromic acid?

Both ammonium dichromate and chromic acid are strong oxidizing agents containing chromium in the +6 oxidation state. However, chromic acid (H2CrO4) is generally more reactive due to its higher acidity. Ammonium dichromate is often preferred in situations where a solid reagent is more convenient to handle.

16. What safety precautions should be taken when handling ammonium dichromate?

Ammonium dichromate is toxic and a known carcinogen. When handling it, one should wear protective gear including gloves, goggles, and a lab coat. It should be used in a well-ventilated area, and any skin contact should be immediately washed with copious amounts of water.

17. How does ammonium dichromate compare to other chromium compounds in terms of toxicity?

Ammonium dichromate is highly toxic, like other hexavalent chromium compounds. It's considered more dangerous than trivalent chromium compounds due to its higher oxidation state, which makes it more reactive with biological molecules and increases its carcinogenic potential.

18. What is the environmental impact of ammonium dichromate?

Ammonium dichromate can have significant environmental impacts if released. It's toxic to aquatic life and can persist in the environment. The chromium it contains can accumulate in living organisms and potentially enter the food chain, causing long-term ecological effects.

19. How does ammonium dichromate behave under different lighting conditions?

Ammonium dichromate is photosensitive. When exposed to light, especially UV light, it can undergo photochemical reactions. This property is the basis for its historical use in photographic processes and can also lead to gradual decomposition if stored in light-exposed conditions.

20. What is the role of ammonium dichromate in photography?

Historically, ammonium dichromate was used in various photographic processes, particularly in dichromate photography. When exposed to light, it hardens gelatin, allowing for the creation of photoresists and printing plates. However, its use has declined due to safety concerns.

21. Why is ammonium dichromate considered a strong oxidizing agent?

Ammonium dichromate is a strong oxidizing agent due to the presence of chromium in its highest oxidation state (+6). The dichromate ion can readily accept electrons, reducing chromium to lower oxidation states and oxidizing other substances in the process.

22. What happens during the thermal decomposition of ammonium dichromate?

When heated, ammonium dichromate decomposes in a spectacular reaction known as the "volcano reaction." It produces nitrogen gas, water vapor, and chromium(III) oxide, accompanied by sparks and the formation of a green "ash" that resembles a miniature volcano eruption.

23. How does the redox potential of ammonium dichromate compare to other common oxidizing agents?

Ammonium dichromate has a high redox potential, making it a strong oxidizing agent. Its oxidizing power is comparable to that of potassium dichromate and is stronger than many other common oxidizers like hydrogen peroxide or potassium permanganate in acidic conditions.

24. How does the structure of ammonium dichromate contribute to its properties?

Ammonium dichromate consists of ammonium ions (NH4+) and dichromate ions (Cr2O7^2-). The dichromate ion has a characteristic V-shape with two tetrahedral chromium centers sharing an oxygen atom. This structure contributes to its oxidizing properties and thermal decomposition behavior.

25. How does ammonium dichromate compare to potassium dichromate in terms of properties and uses?

Both compounds contain the dichromate ion and exhibit similar oxidizing properties. However, ammonium dichromate is more soluble in water and decomposes at a lower temperature. Potassium dichromate is more stable and is often preferred in analytical chemistry.

26. How does the solubility of ammonium dichromate compare to other chromium compounds?

Ammonium dichromate is highly soluble in water, more so than many other chromium compounds. This property is due to the presence of ammonium ions, which form hydrogen bonds with water molecules, enhancing solubility.

27. How does the crystal structure of ammonium dichromate influence its properties?

Ammonium dichromate crystallizes in a monoclinic system. This crystal structure allows for efficient packing of the ammonium and dichromate ions, contributing to its physical properties such as its orange color, solubility, and thermal behavior.

28. What is ammonium dichromate and why is it orange?

Ammonium dichromate is an inorganic compound with the chemical formula (NH4)2Cr2O7. It appears orange due to the presence of chromium in its +6 oxidation state, which absorbs light in the blue-violet region of the visible spectrum, reflecting orange light.

29. How does the thermal stability of ammonium dichromate compare to other ammonium salts?

Ammonium dichromate is less thermally stable than many other ammonium salts due to the oxidizing nature of the dichromate ion. It decomposes at lower temperatures, around 180°C, compared to salts like ammonium chloride, which sublimes at higher temperatures.

30. How does ammonium dichromate behave as an electrolyte in solution?

In solution, ammonium dichromate dissociates completely into ammonium ions (NH4+) and dichromate ions (Cr2O7^2-). As a strong electrolyte, it conducts electricity well and exhibits properties typical of ionic compounds in solution, such as decreased freezing point and increased boiling point of the solvent.

31. What is the significance of ammonium dichromate in qualitative analysis?

Ammonium dichromate is used in qualitative analysis to detect the presence of certain ions. For example, it can be used to test for the presence of lead ions, forming a yellow precipitate of lead chromate.

32. What is the role of ammonium dichromate in leather tanning?

Ammonium dichromate has been used in leather tanning as a chrome tanning agent. It can be reduced to chromium(III) compounds, which form cross-links with the collagen fibers in leather, improving its durability and resistance to water and heat.

33. Why is ammonium dichromate used in pyrotechnics?

Ammonium dichromate is used in pyrotechnics due to its spectacular decomposition reaction. When ignited, it produces sparks, ash, and smoke, creating visual effects. However, its use is limited due to toxicity concerns.

34. What role does ammonium dichromate play in the production of safety matches?

Ammonium dichromate is sometimes used in the production of safety matches as an oxidizing agent in the match head composition. It helps to ensure rapid and reliable ignition when the match is struck against the striking surface.

35. What is the significance of ammonium dichromate in analytical chemistry?

In analytical chemistry, ammonium dichromate serves as a standard oxidizing agent for various titrations and as a reagent for detecting certain ions. Its known oxidation potential makes it useful for standardizing solutions of reducing agents.

36. What is the role of ammonium dichromate in organic synthesis?

In organic synthesis, ammonium dichromate serves as a strong oxidizing agent. It can be used to oxidize primary alcohols to aldehydes, secondary alcohols to ketones, and in some cases, for the complete oxidation of organic compounds to carbon dioxide and water.

37. What is the significance of ammonium dichromate in the production of pigments?

Ammonium dichromate is used in the production of certain pigments, particularly chrome yellow (lead chromate). The dichromate ion reacts with lead compounds to form the bright yellow pigment, which has been used in paints and other colorants.

38. What is the role of ammonium dichromate in chemical vapor deposition (CVD) processes?

Ammonium dichromate can be used as a precursor in chemical vapor deposition processes for depositing thin films of chromium oxides. When heated, it decomposes to form chromium oxide, which can be deposited on various substrates for applications in electronics and materials science.

39. What is the significance of ammonium dichromate in forensic science?

In forensic science, ammonium dichromate can be used in various analytical techniques. For example, it can be used in tests for the presence of certain drugs or in the analysis of trace metal evidence. Its oxidizing properties make it useful in some chemical spot tests.

40. What is the role of ammonium dichromate in the production of chrome alum?

Ammonium dichromate is a key reagent in the production of chrome alum (ammonium chromium sulfate dodecahydrate). It's reduced by a suitable reducing agent in the presence of sulfuric acid to form the chromium(III) compound, which then crystallizes with ammonium sulfate to form chrome alum.

41. What is the significance of ammonium dichromate in the study of reaction kinetics?

Ammonium dichromate is sometimes used in studying reaction kinetics, particularly in undergraduate chemistry labs. Its decomposition reaction, which produces a visible change, can be used to demonstrate factors affecting reaction rates, such as temperature and particle size.

42. How does ammonium dichromate interact with reducing sugars?

Ammonium dichromate can oxidize reducing sugars. This reaction is sometimes used as a test for the presence of reducing sugars in analytical chemistry. The orange dichromate ion is reduced to green chromium(III) ions, providing a visible color change.

43. What is the role of ammonium dichromate in the production of chromium dioxide (CrO2)?

Ammonium dichromate can be used as a starting material in the production of chromium dioxide (CrO2), a ferromagnetic compound used in magnetic tape. The process involves the thermal decomposition of ammonium dichromate under controlled conditions.

44. How does the presence of ammonium dichromate affect the conductivity of water?

The addition of ammonium dichromate significantly increases the electrical conductivity of water. As a strong electrolyte, it dissociates completely into ions in solution, providing charge carriers that enhance the solution's ability to conduct electricity.

45. What is the significance of ammonium dichromate in the study of coordination compounds?

Ammonium dichromate serves as a source of chromium for synthesizing various coordination compounds. The dichromate ion can be reduced to form chromium(III) complexes, allowing students and researchers to study the colorful world of transition metal coordination chemistry.

46. How does ammonium dichromate behave in non-aqueous solvents?

The behavior of ammonium dichromate in non-aqueous solvents depends on the solvent's polarity and ability to solvate ions. In polar organic solvents like methanol or ethanol, it may partially dissolve, while in non-polar solvents, it generally remains insoluble.

47. What is the role of ammonium dichromate in the production of chromium metal?

While not the primary industrial method, ammonium dichromate can be used in the production of chromium metal through a series of reduction reactions. The dichromate is first reduced to chromium(III) oxide, which can then be further reduced to chromium metal using carbon or aluminum at high temperatures.

48. How does the crystal field splitting of chromium in ammonium dichromate compare to other chromium compounds?

In ammonium dichromate, chromium is in a tetrahedral environment within the dichromate ion. This results in a different crystal field splitting compared to octahedral chromium complexes. The tetrahedral field is generally weaker, influencing the compound's color and magnetic properties.

49. What is the significance of ammonium dichromate in environmental monitoring?

Ammonium dichromate, due to its toxicity and environmental persistence, is often a target analyte in environmental monitoring programs. Its presence in water or soil can indicate industrial pollution, and its levels are regulated in many jurisdictions.

50. How does ammonium dichromate interact with amino acids and proteins?

Ammonium dichromate can oxidize amino acids and proteins, potentially causing denaturation. This interaction is one reason for its toxicity in biological systems. The oxidation can lead to the formation of cross-links between protein molecules, altering their structure and function.

51. What is the role of ammonium dichromate in the production of holographic materials?

Ammonium dichromate has been used in the production of holographic materials due to its photosensitive properties. When mixed with gelatin and exposed to light, it creates areas of varying refractive index, allowing for the creation of holograms.

52. How does the thermal conductivity of ammonium dichromate compare to other inorganic salts?

The thermal conductivity of ammonium dichromate is relatively low compared to many other inorganic salts. This is due to its complex crystal structure and the presence of large, complex ions which impede the efficient transfer of thermal energy through the lattice.

53. What is the significance of ammonium dichromate in the study of redox reactions?

Ammonium dichromate is often used as a model compound in the study of redox reactions due to its strong oxidizing properties and visible color changes. It helps students understand concepts like oxidation states, electron transfer, and the role of oxidizing agents in chemical reactions.

54. How does ammonium dichromate affect the freezing point of water?

As an ionic compound, ammonium dichromate causes freezing point depression when dissolved in water. The extent of this depression depends on the concentration of the solution and is proportional to the number of particles (ions) produced upon dissociation.