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Ammonium molybdate is a chemical compound with the formula (NH4)2MoO4. It is commonly encountered in two different forms:

1. Ammonium molybdate tetrahydrate ((NH4)2MoO4 · 4H2O): This is the most common form of ammonium molybdate. It is a white crystalline solid that contains four water molecules per formula unit. It is often used as a source of molybdenum in various applications, such as analytical chemistry, fertilizers, and catalysts.

2. Ammonium molybdate dihydrate ((NH4)2MoO4 · 2H2O): This form of ammonium molybdate is similar to the tetrahydrate but contains two water molecules per formula unit. It is also a white crystalline solid and finds applications in similar fields as the tetrahydrate.

Both forms of ammonium molybdate are widely used in laboratories and industries for their molybdenum content, which is an important element in various chemical processes and applications.

Ammonium metavanadate (NH4VO3) is an inorganic compound that can act as an environmental catalyst in various applications. It contains the vanadium(V) cation, which is a redox-active element with multiple oxidation states, allowing it to participate in catalytic reactions.

Here are a few ways in which ammonium metavanadate can function as an environmental catalyst:

1. Air Pollution Control: Ammonium metavanadate can be used as a catalyst in selective catalytic reduction (SCR) systems to mitigate nitrogen oxide (NOx) emissions from industrial processes and power plants. In SCR, ammonia (NH3) is used as a reducing agent to convert harmful NOx into nitrogen (N2) and water (H2O) through a reaction facilitated by the catalyst.

2. Organic Synthesis: Ammonium metavanadate can serve as a catalyst in various organic synthesis reactions. For instance, it can be used in the oxidative bromination of organic compounds, where it facilitates the introduction of bromine atoms into specific positions of a molecule. It can also catalyze oxidation reactions, such as the conversion of alcohols to aldehydes or ketones.

3. Water Treatment: Ammonium metavanadate has been investigated for its potential in water treatment applications. It can act as a catalyst in advanced oxidation processes (AOPs) to degrade organic pollutants in water. AOPs typically involve the generation of highly reactive hydroxyl radicals (•OH), which can break down organic contaminants into simpler, less harmful compounds. Ammonium metavanadate can participate in these reactions and enhance the degradation efficiency.

4. Fuel Cells: Vanadium-based compounds, including ammonium metavanadate, have been explored as catalysts in fuel cells. Fuel cells generate electricity through electrochemical reactions, and catalysts are essential to facilitate these reactions. Ammonium metavanadate can be utilized as a catalyst in the oxygen reduction reaction (ORR) that occurs at the cathode of fuel cells, improving their efficiency and performance.

Ammonium heptamolybdate, also known as ammonium molybdate(VI), is a commonly used compound in analytical chemistry and industrial applications. It is primarily used as a reagent for the determination of phosphate, arsenate, and silicate in various samples. The solubility of ammonium heptamolybdate in water is moderate.

At room temperature (around 25 degrees Celsius or 77 degrees Fahrenheit), the solubility of ammonium heptamolybdate is approximately 80 grams per 100 milliliters of water. It means that 80 grams of ammonium heptamolybdate can dissolve in 100 milliliters of water at this temperature. However, it’s important to note that the solubility may vary slightly depending on the purity of the compound and the specific conditions.

Ammonium dimolybdate, also known as ammonium molybdate, is a chemical compound with the formula (NH4)2Mo2O7. It is composed of ammonium cations (NH4+) and dimolybdate anions (Mo2O7^2-). Ammonium dimolybdate has several uses in various fields:

1. Catalyst: Ammonium dimolybdate is used as a catalyst in various chemical reactions, particularly in the petroleum and petrochemical industries. It is commonly employed in processes such as desulfurization, oxidation, and hydrodesulfurization.

2. Fertilizers: Ammonium dimolybdate is used as a source of molybdenum in fertilizers. Molybdenum is an essential micronutrient for plants, and its deficiency can adversely affect crop growth and development. Adding ammonium dimolybdate to the soil helps provide plants with the required molybdenum.

3. Pigments: Ammonium dimolybdate is used in the production of pigments, specifically yellow and orange pigments. These pigments find applications in various industries, including paints, ceramics, plastics, and textiles.

4. Corrosion inhibitors: Ammonium dimolybdate is utilized as a corrosion inhibitor in various systems, such as cooling water treatment, metal surface coatings, and oil and gas pipelines. It helps to prevent or slow down the corrosion process by forming a protective film on the metal surface.

5. Analytical chemistry: Ammonium dimolybdate is used as a reagent in analytical chemistry, particularly for the determination of phosphates and silicates. It forms complexes with these analytes, allowing their quantification through colorimetric or spectrophotometric methods.

6. Electroplating: Ammonium dimolybdate is sometimes used in the electroplating industry for molybdenum plating. This process can enhance the corrosion resistance and wear resistance of metal surfaces.

7. Research and development: Ammonium dimolybdate is employed in various research and development activities, such as the synthesis of other molybdenum compounds, the preparation of catalysts, and the investigation of new chemical reactions and processes.