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Ammonium Phosphate - Formula, Structure, Properties and Uses

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Last updated date: 22nd Mar 2024
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About Ammonium Phosphate

Ammonium phosphate is a salt that is made up of ammonia and phosphorus, and its chemical formula is (NH4)3PO4.  However, this is a very unstable salt and due to how unstable it is, it is not exactly a salt worth a lot of commercial value. It can be formed by combining phosphoric acid along with ammonia, or by adding a lot more ammonia with acid phosphate.

For it to be used commercially, it is mostly obtained from crystalline powders. 


The Formula of Ammonium Phosphate

The molecular formula for this salt is (NH4)3PO4 and it is also referred to as triammonium phosphate or diazonium hydrogen phosphate.

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How is Ammonium Phosphate Formed?

When phosphoric acid H3PO4 reacts with ammonia NH3 (it needs to be anhydrous in nature), we get the following reaction: 

NH3 + H3PO4 → NH4H2PO4

On combining concentrated quantities of both the products, ammonium phosphate is amassed in the form of a crystallised powder. This powder is soluble in water and if the water is boiled, then the solution loses the ammonia in the form of gas. This then results in the formation of acid phosphate (NH4)(H2PO4).


Structure of Ammonium Phosphate

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What are the Properties of Ammonium Phosphate?

Every salt or compound has a set of distinct physical and chemical properties which are used as basic determinants to differentiate it from other chemical compounds and salts.

Physical Properties: 

Since this is a salt of ammonia, the characteristic smell of ammonia will always be present. The crystallised powder is white in colour. The powder is also very easily soluble in water with a pH that ranges between 4-4.5. 

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Chemical Properties: 

The salt is highly unstable due to the nature of the compounds that are combined to make this.

Even though triammonium salt has an unstable nature, diammonium phosphate still holds an important position within the fertilizer industry. That being said, all the phosphate acids are divided into three categories:

  • Phosphoric acid and super phosphoric acid

  • Normal superphosphate and triple superphosphate

  • Ammonium phosphate in granular form

Ammonium phosphate can readily react with lead nitrate, which results in the formation of ammonium nitrate and lead phosphate.

4(NH4)3PO4 + 3Pb(NO3)4 → Pb3(PO4)4 + 12NH4NO3

Anhydrous ammonia, when it reacts with phosphoric acid, also results in the production of the ammonium phosphate.

NH3 + H3PO4 à NH4H2PO4


Ammonium Phosphate Uses

Down below is a list of some of the major use cases of ammonium phosphate:

  • Ammonium phosphate is used as a leavening agent during the process of bakingIts interaction with heat, results in instant evaporation without leaving any residue of ammonia

  • Due to the ability of rapidly dissolving and becoming soluble, ammonium phosphate works as an effective fertilizer. It has two crucial elements embedded in them, the ammonium and phosphate, both of which are highly beneficial to the plants

  • It also works great as a plant revitalize

  • Ammonium phosphate can also be used as a great ingredient for dry chemical extinguisher


Solved Questions

1. If a sample of Ammonium phosphate (NH4)3PO4 has 3.18 moles of hydrogen atom then what is the number of moles available for oxygen atoms within the solution?

i) 0.265

ii) 1.06 

iii) 0.795

iv) 3.18

Solution: As we know that the molar mass of (NH4)3PO4 is 149 grams.

Within the same, contains 12 g of HSo for 3.18 moles, i.e. 3.18 grams of H, the total number of moles of ammonium phosphate:

12149×3.18​=39.5gm (NH4)3PO4

We know that 149 grams of (NH4)3PO4 contains 64g of oxygen

So, for 39.5 grams of (NH4)3PO4 it will contain 

14964×39.5​g of oxygen =16.96 gm oxygen

So, 16.96 grams of oxygen is present

Converting it into moles, we get, 1616.96 = 1.06 moles of OSo, the right answer is option ii).

 

2. If 6 moles of H are present in a sample of (NH4)3PO4, what is the number of moles of oxygen atom? Answer the question without converting the moles into grams.

1)     6

2)     4

3)     2

4)     1

Solution: We know that in ammonium phosphate:

The total number of H atoms: 12

Total number of O atoms: 4

We know that the ratio of atoms and moles remains the same

So, 12/4 = 6/X

Or, X = 2

So, the total number of moles of oxygen is 2.

FAQs on Ammonium Phosphate - Formula, Structure, Properties and Uses

1. What is the Difference between Ammonia and Ammonium?

Ammonia, with its chemical formula of NH3, is a neutral substance. It doesn’t have any electrical change. On the contrary, Ammonium is positively charged. The ammonia compound consists of one nitrogen alongside three hydrogen atoms. Ammonium, on the other hand, consists of another hydrogen atom, resulting in a +1 in charge. So, on an atomic level, they are two different elements.

Both ammonia and ammonium can also be differentiated based on the pH level when mixed with water. Ionic strength and temperature are also some of the influential factors for ammonia. The un-ionized ammonia is deemed to be harmful to aquatic animals, while ammonium doesn’t show any such trait.

The chemical equation between ammonia and ammonium is given by:

NH 3 + H2O <-> NH 4 + + OH -

With a lower pH, the reaction shifts rightward, whereas a higher pH drives the equation to the left side. In room temperature, the pH is generally lower than 6. Thus, the proportion of ammonium N along with ammonia N remains unbalanced. While NH3 remains lower, the concentration of NH 4+ increases exponentially.

2. How is Ammonium Phosphate Soluble in Water?

Before figuring out its solubility, one needs to understand what is the chemical formula for ammonium phosphate along with its structure. It is an ammonium salt of orthophosphoric acid, which makes it a highly unstable compound and easy to react with. When ammonium phosphate is added in water, the acidic phosphate is formed, leaving ammonia behind. The reaction is what makes ammonium phosphate soluble in water. It is the sole reason, due to which (NH₄)₃PO₄ is used as a fertilizer.

Not considering the fact that water is a universal solvent, ammonium phosphate has been seen to be very easily soluble in water. The reason behind this can be found in the structure of the salt itself. The salt is formed of orthophosphoric acid and this is very unstable in nature, meaning that it cannot occur in isolation and has the tendency to easily combine and react with other substances. This is why when it is added to water, the ammonia escapes as gas and phosphoric acid is formed in the water.

3. How is ammonium phosphate used?

There are many industrial uses for this salt. The most common application of ammonium phosphate is seen in the agricultural industry since it is a very potent and useful fertilizer. Due to the fact that it is very readily soluble in water and has a very quick ability to dissolve, it is ideal as a fertilizer. Ammonium phosphate releases nutrients such as nitrogen very quickly into the soil when used in fertilisers, which replenishes and nourishes the soil and helps in healthier crop yield.

4. Can ammonium phosphate be harmful?

Many salts can be harmful if they are directly touched or inhaled or swallowed. This is why safety practices are always encouraged wherever chemical reactions are concerned. If the fumes are inhaled then it can lead to serious respiratory tract damage. Upon coming to contact with human skin, this salt can cause chemical burns as well. If the eyes are exposed to this without any proper protective gear, then there can be significant vision damage as well. This is why it is always important to prioritise safety while working with chemicals.

5. How can burns from ammonium phosphate be treated?

Chemical burns can have serious health implications. While it is true that safety practices are always adhered to, there can be accidents. In that case, it is important to first neutralise the site of the burn. This can be done by gently washing the area with a mixture of warm water and baking soda in a 3:1 ratio. The area should then be rinsed again with lukewarm water and then a mild soap solution needs to be used on the area. In case of severe burns, the person needs to be sent to the emergency room.