Question

What is the chemical formula for the compound ammonium phosphate? Use the list of polyatomic ions and the periodic table to help you answer.
Chemical Name Chemical Formula Chemical Name Chemical Formula
acetate C2H3O2– nitrite NO2–
carbonate CO32– ammonium NH4+
hypocarbonite CO2− cyanide CN–
hydrogen carbonate
(bicarbonate) HCO3– hydroxide OH–
chlorite ClO2– peroxide O22–
hypochlorite ClO– phosphate PO43–
chlorate ClO3– hydrogen phosphate HPO42–
perchlorate ClO4– dihydrogen phosphate H2PO4–
hydronium H3O+ sulfate SO42–
permanganate MnO4– hydrogen sulfate (bisulfate) HSO4–
nitrate NO3– sulfite SO32–


A. H4H2PO4
B. (NH4)2PO4
C. (NH4)3PO4
D. (NH4)4PO4

Answer 1

Answer:

The correct answer is option C.

Explanation:

The nomenclature of ionic compounds is given by:

1. Positive is written first.

2. The negative ion is written next and a suffix is added at the end of the negative ion. The suffix written is '-ide', 'ate' , 'ite' according to polyatomic anion.

The chemical formula for the compound ammonium phosphate:

Name of the cation =  ammonium = $NH_4^{+}$

Name of the anion =  phosphate  = $PO_4^{3-}$

By criss-cross method, the oxidation state of the ions gets exchanged and they form the subscripts of the other ions. This results in the formation of a neutral compound.

So, the chemical formula for the given compound is

Ammonium phosphate = $(NH_4)_3PO_4$

Answer 2

Answer: The correct answer is Option C.

Explanation:

We are given some polyatomic ions with their oxidation states. Polyatomic ions are defined as the ions which are formed from more than 2 atoms.

We need to find out the chemical formula for ammonium phosphate.

For this, the polyatomic ions used are:

Ammonium ion - $NH_4^+$

Phosphate ion - $PO_4^{3-}$

By using criss-cross method, the oxidation state of the ions are exchanged and they form the subscripts of the other ions. This results in the formation of a neutral compound.

Thus, the chemical formula for this compound is $(NH_4)_3PO_4$

Hence, the correct answer is Option C.