Question

Which of the following are the most powerful oxidizing agents?
A) ${{\text{H}}_{\text{2}}}{\text{S}}{{\text{O}}_{\text{4}}}$
B) ${{\text{H}}_3}{\text{B}}{{\text{O}}_3}$
C) ${\text{HP}}{{\text{O}}_3}$
D) ${{\text{H}}_3}{\text{P}}{{\text{O}}_4}$

Answer 1

The species which causes the oxidation of another species and itself undergoes the reduction is known as the oxidizing agent. The oxidizing agent is also known as oxidant. Redox reaction is the reaction in which one species undergoes the oxidation while another species undergoes the reduction. In the redox reaction, the species which gains the electrons or whose oxidation number is decreasing acts as the oxidizing agent. The reducing agent is the species which causes the reduction of another species and itself undergoes the oxidation. It is also known as reductant.

Complete step-by-step answer:
Here all given are the acids. The sulfuric acid is represented using the formula ${{\text{H}}_{\text{2}}}{\text{S}}{{\text{O}}_{\text{4}}}$, boric acid is ${{\text{H}}_3}{\text{B}}{{\text{O}}_3}$, ${\text{HP}}{{\text{O}}_3}$ is metaphosphoric acid, and${{\text{H}}_3}{\text{P}}{{\text{O}}_4}$ is phosphoric acid.

Here, we have to determine the oxidation state of the sulphur in sulphuric acid ${{\text{H}}_{\text{2}}}{\text{S}}{{\text{O}}_{\text{4}}}$as follows:
The oxidation state of the hydrogen is +1 and oxygen is -2 and consider x is the oxidation state of sulphur in sulphuric acid.

${\text{2}}\left( {{\text{ + 1}}} \right){\text{ + x + 4}}\left( {{\text{ - 2}}} \right){\text{ = 0}}$
${\text{2 + x - 8 = 0}}$
${\text{x = + 6}}$
Here, sulphur is present in the +6 oxidation state.
Now, we have to determine the oxidation state of boron in boric acid ${{\text{H}}_3}{\text{B}}{{\text{O}}_3}$ as follows:
The oxidation state of the hydrogen is +1 and oxygen is -2 and consider x is the oxidation state of sulphur in sulphuric acid.

$3\left( {{\text{ + 1}}} \right){\text{ + x + 3}}\left( {{\text{ - 2}}} \right){\text{ = 0}}$
${\text{3 + x - 6 = 0}}$
${\text{x = + 3}}$
Here, boron is present in the +3 oxidation state.

Now, we have to determine the oxidation state of phosphorus in metaphosphoric acid ${\text{HP}}{{\text{O}}_3}$ as follows:
Consider x is the oxidation state of phosphorus.
$\left( {{\text{ + 1}}} \right){\text{ + x + 3}}\left( {{\text{ - 2}}} \right){\text{ = 0}}$
${\text{1 + x - 6 = 0}}$
${\text{x = + 5}}$
Here, phosphorus is present in the +5 oxidation state.

Now, we have to determine the oxidation state of phosphorus in phosphoric acid ${{\text{H}}_3}{\text{P}}{{\text{O}}_4}$ as follows:
Consider x is the oxidation state of phosphorus in phosphoric acid.
$3\left( {{\text{ + 1}}} \right){\text{ + x + 4}}\left( {{\text{ - 2}}} \right){\text{ = 0}}$
${\text{3 + x - 8 = 0}}$
${\text{x = + 5}}$
Here, phosphorus is present in the +5 oxidation state.

The element with higher positive oxidation state easily undergoes the reduction reaction and acts as the powerful oxidizing agent.

Now, option (A) ${{\text{H}}_{\text{2}}}{\text{S}}{{\text{O}}_{\text{4}}}$ where sulphur is in +6 oxidation state which is highest oxidation state among the all given acid hence, sulphur easily undergoes the reduction reaction and acts as a strongest oxidizing agent among all given acids. Hence, option (A) is the correct answer to the question.

Now, option (B) ${{\text{H}}_3}{\text{B}}{{\text{O}}_3}$ where boron in is +3 oxidation state which is not highest oxidation state among all given acids hence, is it not strongest oxidizing agent among given acids, therefore, option (B) is incorrect.

Now, option (C) ${\text{HP}}{{\text{O}}_3}$ where phosphorus in is +5 oxidation state which is not highest oxidation state among all given acids hence, is it not strongest oxidizing agent among given acids, therefore, option (C) is incorrect.

Now, option (D) ${{\text{H}}_3}{\text{P}}{{\text{O}}_4}$ where phosphorus in is +5 oxidation state which is not highest oxidation state among all given acids hence, is it not strongest oxidizing agent among given acids, therefore, option (D) is incorrect.

Hence the correct answer is option ‘A’.

Note: The most common oxidation state of the hydrogen is +1 and oxygen is -2. The total oxidation number of the compound or species is equal charge present on it. The species which is electron deficient is easily undergone the reduction and causes oxidation of the other species hence acts as a strong oxidizing agent while species which in lower oxidation state acts as a strong reducing agent.