Question

An element X forms an oxide with formula ${{X}_{2}}{{O}_{3}}$.
(A) State the valency of X
(B) Write the formula of:
i) Chloride of X. ii) Sulphate of X.

Answer 1

Hint: As we know oxides are the chemical compounds which contain at least one oxygen atom along with other elements in its chemical formula. The valency of other elements can be calculated by using the oxidation state of the oxygen atom. So here we have to calculate the oxidation state of X and form its compound with other anions.

Complete answer:
Let us first understand about oxide compounds and calculate the oxidation state of X in ${{X}_{2}}{{O}_{3}}$ compound as follows:-
Oxides: These are the compounds that contain at least one oxygen atom along with other elements in its chemical formula. The oxidation state of oxygen is generally -2 in the oxide compounds.
(A) Calculation of valency of element X in ${{X}_{2}}{{O}_{3}}$compound as follows:-
Let us suppose the valency (oxidation state) of X is ‘a’. As the compound is neutral so summation of valencies of all the atoms in the compound is equal to 0. So ‘a’ can be calculated as:-
$\begin{align}
  & \Rightarrow 2a+3(-2)=0 \\
 & \Rightarrow 2a=6 \\
 & \Rightarrow a=+3 \\
\end{align}$
Therefore, the valency of X is +3.
(B) i) Chloride of X:-
As we know that chloride is an anion with -1 charge. To form a chloride compound with X, both have to complete each other octet or neutralize their charges. Three chloride anions will interact with one cation of X in order to neutralize each other charge.
${{X}^{+3}}+3C{{l}^{-1}}\to XC{{l}_{3}}$
Hence the chloride of X is $XC{{l}_{3}}$ .
ii) Sulphate of X:-
As we know, sulphate is an anion with -2 charge and its chemical formula is $S{{O}_{4}}^{-2}$ . To form a sulphate compound with X, we require 3 sulphate anions to interact with two cations of X in order to neutralize each other charge.
${{X}^{+3}}+S{{O}_{4}}^{-2}\to {{X}_{2}}{{(S{{O}_{4}})}_{3}}$
Hence the sulphate of X is ${{X}_{2}}{{(S{{O}_{4}})}_{3}}$.

Note:
-Compounds can be directly formed by exchanging the valencies of both ions and writing them in their subscript. For example there are two ions ${{A}^{+a}}$ and ${{B}^{-b}}$. Let us exchange their valencies and write them as subscript as shown below:-
${{A}_{b}}{{B}_{a}}$
This trick can be applied to form any compound with the given ions.