What is ammonium phosphate definition formula reactions and uses
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
14964×39.5g 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 Chemistry and Applications
1. What is ammonium phosphate?
Ammonium phosphate is a salt formed from the reaction of ammonia (NH3) with phosphoric acid (H3PO4), commonly used as a fertilizer.
It contains the ammonium ion (NH4+) and the phosphate ion (PO43-). Depending on the ratio of ammonia to phosphoric acid, different types are formed, such as monoammonium phosphate and diammonium phosphate. Ammonium phosphate is highly valued in agriculture because it supplies both nitrogen (N) and phosphorus (P), two essential plant nutrients.
2. What is the chemical formula of ammonium phosphate?
The chemical formula of ammonium phosphate is (NH4)3PO4.
This formula shows that three NH4+ ions are required to balance one PO43- ion, ensuring overall electrical neutrality:
- Charge of 3 × NH4+ = +3
- Charge of PO43- = −3
The total charge is zero, forming a neutral ionic compound.
3. What are the different types of ammonium phosphate?
The main types of ammonium phosphate are monoammonium phosphate (MAP), diammonium phosphate (DAP), and triammonium phosphate.
- Monoammonium phosphate (NH4H2PO4) – formed from one NH4+ and one H2PO4-
- Diammonium phosphate ((NH4)2HPO4) – contains two NH4+ and one HPO42-
- Triammonium phosphate ((NH4)3PO4) – contains three NH4+ and one PO43-
MAP and DAP are the most commonly used phosphate fertilizers in agriculture.
4. How is ammonium phosphate prepared?
Ammonium phosphate is prepared by reacting ammonia (NH3) with phosphoric acid (H3PO4) in a neutralization reaction.
For example, triammonium phosphate can be formed as:
3NH3(aq) + H3PO4(aq) → (NH4)3PO4(aq)
Similarly:
- NH3 + H3PO4 → NH4H2PO4 (MAP)
- 2NH3 + H3PO4 → (NH4)2HPO4 (DAP)
The product depends on the molar ratio of ammonia to phosphoric acid.
5. Is ammonium phosphate an acid or a base?
Ammonium phosphate is a salt, but its aqueous solution can be slightly acidic or basic depending on its type.
- Monoammonium phosphate (NH4H2PO4) forms a mildly acidic solution.
- Diammonium phosphate ((NH4)2HPO4) forms a slightly basic solution.
This behavior occurs because NH4+ is a weak acid (conjugate acid of NH3) and phosphate species can act as weak bases, influencing the solution pH.
6. What is ammonium phosphate used for?
Ammonium phosphate is mainly used as a fertilizer because it provides essential nitrogen and phosphorus to plants.
- Supplies nitrogen (N) for leaf growth
- Supplies phosphorus (P) for root development and energy transfer (ATP)
- Used in fire extinguishers (especially monoammonium phosphate)
- Used in some food and industrial applications
Its high nutrient content makes MAP and DAP among the most widely used phosphate fertilizers worldwide.
7. How do you calculate the molar mass of ammonium phosphate?
The molar mass of ammonium phosphate ((NH4)3PO4) is calculated by adding the atomic masses of all atoms in the formula.
- N: 3 × 14.01 = 42.03 g/mol
- H: 12 × 1.008 = 12.096 g/mol
- P: 1 × 30.97 = 30.97 g/mol
- O: 4 × 16.00 = 64.00 g/mol
Total molar mass ≈ 149.10 g/mol. This value is used in stoichiometric calculations involving ammonium phosphate.
8. Is ammonium phosphate soluble in water?
Yes, ammonium phosphate is highly soluble in water.
As an ionic compound containing NH4+ and phosphate ions, it dissolves readily:
(NH4)3PO4(s) → 3NH4+(aq) + PO43-(aq)
All ammonium salts are generally soluble in water, which makes ammonium phosphate effective for agricultural use.
9. What is the difference between monoammonium phosphate and diammonium phosphate?
The main difference between monoammonium phosphate (MAP) and diammonium phosphate (DAP) is the number of ammonium ions attached to the phosphate species.
- MAP: NH4H2PO4 – contains one NH4+; slightly acidic
- DAP: (NH4)2HPO4 – contains two NH4+; slightly basic
DAP generally has a higher nitrogen content than MAP, making it more concentrated as a nitrogen fertilizer.
10. Is ammonium phosphate ionic or covalent?
Ammonium phosphate is an ionic compound composed of ammonium cations and phosphate anions.
It consists of:
- NH4+ (a polyatomic cation with covalent N–H bonds inside)
- PO43- (a polyatomic anion with covalent P–O bonds inside)
The attraction between NH4+ and PO43- is ionic, while the bonds within each ion are covalent.
