Question

The following list contains some common polyatomic ions. Using the charge on these ions and the idea of valence, predict the formulas for the following: nitrate NO3 - phosphate PO4 -3 sulfate SO4 -2 acetate C2H3O2 -1 ammonium NH4 + chromate CrO4 -2 carbonate CO3 -2 dichromate Cr2O7 -2 permanganate MnO4 -1 potassium chromate

Answer 1

The formula for potassium chromate is
`K_2CrO_4`.

Step-by-step explanation:

The formula for potassium chromate :

Cation in the potassium chromate : Potassium

Anion in the potassium chromate : chromate

The symbol of potassium ion =
`K^+`

oxidation state on the potassium ion = +1

The symbol of chromate ion =
`CrO_4^(2-)`

Oxidation state on the chromate ion = -2

By criss-cross method, teh oxidation states 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 formula for potassium chromate :
`K_2CrO_4`

`2K^++CrO_4^(2-)\rightarrow K_2CrO_4`

Answer 2

Answer: The chemical formula for potassium chromate is
`K_2CrO_4`

Step-by-step explanation:

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

We are asked to find the chemical formula for potassium chromate,

For this, only one polyatomic ion is used which is: Chromate having formula
`CrO_4^(2-)`

Potassium is the 19th element of the periodic table having electronic configuration of
`[Ar]4s^1`

This element will easily loose 1 electron and will attain an oxidation state of +1 forming an ion of
`K^+`

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.

Hence, the chemical formula for this compound is
`K_2CrO_4`