Question

Example(s) of a compound with chlorine in +7 oxidation state is/are:
(This question has multiple correct options)
A. $\text{KCl}{{\text{O}}_{\text{4}}}$
B. $\text{C}{{\text{l}}_{2}}{{\text{O}}_{7}}$
C. $\text{C}{{\text{l}}_{2}}{{\text{O}}_{6}}$
D. All of these

Answer 1

Oxidation state, or oxidation number, of an element is defined as the charge that appears on an atom of the element when all other atoms attached to it are removed in the form of their ions.
- As the overall charge on the given compounds is 0, the sum of the oxidation states of all the atoms of different elements is equal to zero.

Complete Solution :
Let us calculate the oxidation state of chlorine atom one by one in the given compounds:
(a) In $\text{KCl}{{\text{O}}_{\text{4}}}$​,
Let the oxidation number of ‘Cl’ be x.
Since the overall charge on the compound is 0, the sum of oxidation states/numbers of all the atoms of the elements in it is equal to 0.
Oxidation state of potassium (K) is +1 and that of oxygen (O) is -2

& (+1)+x+4(-2)=0 \\\ & \Rightarrow x-7=0 \\\ & \Rightarrow x=+7 \\\ \end{aligned}$$ (b) In $$\text{C}{{\text{l}}_{2}}{{\text{O}}_{7}}$$​, Let the oxidation number of ‘Cl’ be x. The oxidation state of oxygen (O) is -2. Since the overall charge on the compound is 0, the sum of oxidation states/numbers of all the atoms of the elements in it is equal to 0. $$\begin{aligned} & 2x+7(-2)=0 \\\ & \Rightarrow 2x-14=0 \\\ & \Rightarrow x=+7 \\\ \end{aligned}$$ (c) In $$\text{C}{{\text{l}}_{2}}{{\text{O}}_{6}}$$ Let the oxidation number of ‘Cl’ be x. The oxidation state of oxygen (O) is -2. Since the overall charge on the compound is 0, the sum of oxidation states/numbers of all the atoms of the elements in it is equal to 0. $$\begin{aligned} & 2x+6(-2)=0 \\\ & \Rightarrow 2x-12=0 \\\ & \Rightarrow x=+6 \\\ \end{aligned}$$ Thus, we can conclude from the above calculations that, the oxidation state of Cl in $$\text{KCl}{{\text{O}}_{\text{4}}}$$ and $$\text{C}{{\text{l}}_{2}}{{\text{O}}_{7}}$$ is +7. **So, the correct answer is “Option A and B”.** **Note:** In the process of oxidation, there occurs a loss of electrons during a reaction by a molecule, atom or ion. It occurs when the oxidation state of a molecule, atom or ion of an element/compound is increased. The process opposite to this is called reduction, which occurs when there takes place a gain of electrons or the oxidation state of an atom of an element/compound decreases. \- In $$\text{KCl}{{\text{O}}_{\text{4}}}$$ and $$\text{C}{{\text{l}}_{2}}{{\text{O}}_{7}}$$ compounds, the chlorine element is in its highest oxidation state of +7. These compounds can be easily reduced in a redox reaction and they oxidise the other reactant participating in the reaction. Thus, they are strong oxidising agents.