Question

What is the formula of ammonium carbonate?

Answer 1

Criss Cross method is one of the methods to write the chemical formula of the ionic compound. In the criss cross method, we need to cross over the numerical value of each of the ions to become the subscript of another ion. We have to drop the signs of the charges.

Complete answer:
- We know that the crisscross method is used to determine the chemical formula. We can write the chemical formula of the ionic compound by the following steps using criss cross method:
First write the symbols and charges of the anion and cation. The cation is written first, and then the anion is written.
Then transpose the number of positive charges to become the subscript of the anion and the number of negative charges to become the subscript of cation.
Then reduce to the smallest ratio.
The final chemical formula has to be written and the subscript that has 1 is left off.
If there is only one of the polyatomic ions, the parentheses are left off.
The chemical formula of ammonium carbonate:
Here, the cation is ammonium ion and anion, carbonate ion.
The symbol and charge of ammonium ion is $NH^{+}_{4}$
The symbol and charge of carbonate ion is $CO^{2-}_{3}$
Now, interchange the number of positive charges and the number of negative charges. The subscript of ammonium ion becomes $(NH_{4})_{2}$ and the subscript of carbonate ion becomes $CO_{3}$.
Therefore, the formula of ammonium carbonate is $(NH_{4})_{2}CO_{3}$

Note:
We can obtain the chemical formula of compounds by alternate method. In this method, we first write the symbol and charge of cation and anion. Using a multiplier, we make the total charges of the anion and cation equal to each other. The multipliers are used as subscripts for each ion. The final formula is written, and the charges are left out and the subscript and charges that are 1 are left out.