In the following reactions, decide which reactant is...

In the following reactions, decide which reactant is oxidized and which is reduced. Designate the oxidizing agent and the reducing agent. (a) $\mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}(\mathrm{aq})+3 \mathrm{Sn}^{2+}(\mathrm{aq})+14 \mathrm{H}_{3} \mathrm{O}^{+}(\mathrm{aq}) \rightarrow$ $2 \mathrm{Cr}^{3+}(\mathrm{aq})+3 \mathrm{Sn}^{4+}(\mathrm{aq})+21 \mathrm{H}_{2} \mathrm{O}(\ell)$ (b) $\mathrm{FeS}(\mathrm{s})+3 \mathrm{NO}_{3}^{-}(\mathrm{aq})+4 \mathrm{H}_{3} \mathrm{O}^{+}(\mathrm{aq}) \rightarrow$ $3 \mathrm{NO}(\mathrm{g})+\mathrm{SO}_{4}^{2-}(\mathrm{aq})+\mathrm{Fe}^{3+}(\mathrm{aq})+6 \mathrm{H}_{2} \mathrm{O}(\ell)$

In the following reactions, decide which reactant is oxidized and which is reduced. Designate the oxidizing agent and the reducing agent.
(a) $\mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}(\mathrm{aq})+3 \mathrm{Sn}^{2+}(\mathrm{aq})+14 \mathrm{H}_{3} \mathrm{O}^{+}(\mathrm{aq}) \rightarrow$
$2 \mathrm{Cr}^{3+}(\mathrm{aq})+3 \mathrm{Sn}^{4+}(\mathrm{aq})+21 \mathrm{H}_{2} \mathrm{O}(\ell)$
(b) $\mathrm{FeS}(\mathrm{s})+3 \mathrm{NO}_{3}^{-}(\mathrm{aq})+4 \mathrm{H}_{3} \mathrm{O}^{+}(\mathrm{aq}) \rightarrow$
$3 \mathrm{NO}(\mathrm{g})+\mathrm{SO}_{4}^{2-}(\mathrm{aq})+\mathrm{Fe}^{3+}(\mathrm{aq})+6 \mathrm{H}_{2} \mathrm{O}(\ell)$

Key Concepts

Reducing Agent

The reducing agent is the species that donates electrons to another substance and is itself oxidized. This concept is essential for determining which reactant donates electrons and triggers the reduction of its reaction partner.

Redox Reactions

Redox reactions involve the transfer of electrons between chemical species, resulting in changes in their oxidation states. Understanding redox reactions is fundamental to deciphering more complex chemical processes because they depict how substances interact by exchanging electrons.

Oxidation

Oxidation is the process in which a chemical species loses electrons during a reaction, leading to an increase in its oxidation state. This concept is central to identifying which reactants are undergoing electron loss in any redox reaction.

Reduction

Reduction is the process in which a chemical species gains electrons, resulting in a decrease in its oxidation state. Recognizing reduction is key to understanding which reactant gains electrons, thereby being reduced, in a redox process.

Oxidizing Agent

The oxidizing agent is the species that accepts electrons from another substance and is itself reduced. It plays a crucial role in a redox reaction by facilitating the oxidation of another reactant.

Oxidation States

Oxidation states are assigned numerical values that represent the degree of oxidation of an atom in a chemical compound. They are a vital tool for tracking electron transfer during redox reactions and for determining which species are oxidized or reduced.

Transcript

00:01 Hello everyone.

00:02 Thanks for joining as we id the substances oxidized and substances reduced.

00:08 Please remember that the substance oxidized is the reducing agent and the substance reduced is the oxidizing agent.

00:16 Let's begin.

00:18 Okay, we are going to start with this problem and it's pretty easy to see that tin and chromium are our substances in question.

00:30 Let's start with chromium.

00:33 In this substance on the reactant side, chromium, if oxygen contributes a negative 14, and i have a negative 2 overall charge, chromium, and this should be a 2.

00:48 I copied this down wrong.

00:50 I feel terrible for that, but at least i noticed it now.

00:55 There's a 2.

00:56 Chromium is going to have to be a positive 6 to give me a plus 12.

01:04 So chromium is a plus six.

01:08 On the reactant side, and it is a plus six on the product side, or plus three on the product side.

01:18 So chromium is going from a positive six charge to a positive three charge.

01:26 In order to do that, chromium had to gain electrons.

01:32 Therefore, it's reduced and it is the oxidizing agent.

01:47 Okay, next.

01:52 Let's take a look at 10.

01:54 10 is a 2 plus on this side, on the reactant side, and it's a 4 plus on the product side...