In the following reaction, what is oxidized, reduced, oxidizing agent, and reducing agent? #"2K"_2"Cr"_2"O"_7 + "2H"_2"O + 3S"##rarr##"4KOH + 2Cr"_2"O"_3 + "3SO"_2"#

1 Answer
Apr 11, 2018

Sulfur is the reducing agent and is oxidized, while potassium dichromate is the oxidizing agent and is reduced.

Explanation:

We have the equation:

#2K_2Cr_2O_7+2H_2O+3S->4KOH+2Cr_2O_3+3SO_2#

Oxidation is defined as the loss of electrons or the gain of oxygen, while reduction is defined as the gain of electrons or the loss of oxygen.

Oxidizing agents are substances that can oxidize other substances, and are therefore reduced in the process. Reducing agents are substances that can reduce other substances, but are oxidized in the process.

We will use the definition for oxidation and reduction in terms of oxygen transfer, as it'll save us time from calculating oxidation states.

I see immediately that potassium dichromate #(K_2Cr_2O_7)# turns into chromium(III) oxide #(Cr_2O_3)#, and has lost four oxygen atoms, and so it is reduced in the equation. So, it is also the oxidizing agent in this equation.

Sulfur #(S)# has turned into sulfur dioxide #(SO_2)#, while gaining two oxygen atoms in the process. So, it is oxidized in this equation, and is therefore the reducing agent in this equation.