Question

What is the formula of sodium zincate?
A.${\text{NaZnOH}}$
B.${\text{N}}{{\text{a}}_{\text{2}}}{\text{Zn}}{\left( {{\text{OH}}} \right)_{\text{4}}}$
C.${\text{NaZn}}{\left( {{\text{OH}}} \right)_{\text{3}}}$
D.${\text{NaZn}}{\left( {{\text{OH}}} \right)_{\text{4}}}$

Answer 1

Hint:To answer this question, you must recall the rules for writing the chemical formula and the nomenclature of inorganic chemical compounds set by the International Union of Pure and Applied Chemistry or the IUPAC. The rules of nomenclature help us to find the chemical formula of a compound since each compound and complex ion is represented by a unique name.

Complete answer:
We have to find the chemical formula for sodium zincate. We know that sodium is an alkali metal with a valency of 1. It is present in compounds as a monovalent cation as $N{a^ + }$.
The zincate ion is represented as $Zn\left( {OH} \right)_4^{2 - }$.
We know that while writing the chemical formula of a compound, we cross the valencies of the two species or the charges in case of ionic compounds. So the subscript of sodium in the compound becomes equal to the magnitude of charge of zincate ion that is 2 and the subscript of zincate ion is 1.
The chemical formula of sodium zincate is thus given by ${\text{N}}{{\text{a}}_{\text{2}}}{\text{Zn}}{\left( {{\text{OH}}} \right)_{\text{4}}}$

Hence, the correct answer is B.

Note:
Nomenclature of inorganic chemical compounds:
While naming of the cations, there are no special rules. The name of the cation in the given chemical compound is written as it is followed by the name of the anion. For example, $KCl$is written as potassium chloride with the name of the cation, i.e. potassium as it is.
The oxyanions (polyatomic anions containing oxygen) are named along with a suffix -ite or -ate, depending on the number of oxygen atoms present in the ion. If two different anions are present, the one with lesser number of oxygen atoms carries the suffix –ite and the one with more oxygen atoms carries the suffix –ate.