Specify which of the following equations represent...

Specify which of the following equations represent oxidation– reduction reactions, and indicate the oxidizing agent, the reducing agent, the species being oxidized, and the species being reduced a. $\mathrm{CH}_{4}(g)+\mathrm{H}_{2} \mathrm{O}(g) \rightarrow \mathrm{CO}(g)+3 \mathrm{H}_{2}(g)$ b. $2 \mathrm{AgNO}_{3}(a q)+\mathrm{Cu}(s) \rightarrow \mathrm{Cu}\left(\mathrm{NO}_{3}\right)_{2}(a q)+2 \mathrm{Ag}(s)$ c. $\mathrm{Zn}(s)+2 \mathrm{HCl}(a q) \rightarrow \mathrm{ZnCl}_{2}(a q)+\mathrm{H}_{2}(g)$ d. $2 \mathrm{H}^{+}(a q)+2 \mathrm{CrO}_{4}^{2-}(a q) \rightarrow \mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}(a q)+\mathrm{H}_{2} \mathrm{O}(l)$

Specify which of the following equations represent oxidation– reduction reactions, and indicate the oxidizing agent, the reducing agent, the species being oxidized, and the species being reduced
a. $\mathrm{CH}_{4}(g)+\mathrm{H}_{2} \mathrm{O}(g) \rightarrow \mathrm{CO}(g)+3 \mathrm{H}_{2}(g)$
b. $2 \mathrm{AgNO}_{3}(a q)+\mathrm{Cu}(s) \rightarrow \mathrm{Cu}\left(\mathrm{NO}_{3}\right)_{2}(a q)+2 \mathrm{Ag}(s)$
c. $\mathrm{Zn}(s)+2 \mathrm{HCl}(a q) \rightarrow \mathrm{ZnCl}_{2}(a q)+\mathrm{H}_{2}(g)$
d. $2 \mathrm{H}^{+}(a q)+2 \mathrm{CrO}_{4}^{2-}(a q) \rightarrow \mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}(a q)+\mathrm{H}_{2} \mathrm{O}(l)$

Key Concepts

Redox Reaction

A redox reaction is a chemical reaction in which electrons are transferred between two species. This process results in changes in the oxidation states of the reactants, involving both oxidation and reduction occurring simultaneously.

Oxidation

Oxidation is the process in which a chemical species loses electrons, leading to an increase in its oxidation state. This fundamental process is one half of a redox reaction and is essential for understanding how substances transform during electron transfer reactions.

Reduction

Reduction is the process where a chemical species gains electrons, resulting in a decrease in its oxidation state. It complements oxidation in redox reactions, and together they describe the complete cycle of electron transfer.

Oxidizing Agent

An oxidizing agent is the substance that accepts electrons during a redox reaction, thereby causing another species to undergo oxidation. Since it gains electrons, the oxidizing agent itself is reduced in the process.

Reducing Agent

A reducing agent is the substance that donates electrons during a redox reaction, thus enabling the reduction of another species. In doing so, the reducing agent is oxidized, highlighting its role in electron donation.

Transcript

00:01 This question is going to take a look at an important chemical process or type of reaction called a redox reaction or oxidation and reduction.

00:10 And we're going to look at this with respect to a couple of different examples here.

00:14 So the first example we're going to take a look at is going to deal here with methane and reacting with water.

00:23 So there should be a two there.

00:24 So methane is going to react with water to form carbon monoxide and hydrogen gas.

00:28 And one way that you can identify whether an oxidation reduction has taken place in reaction is look at what happens to the bonding between a species and oxygen.

00:39 So if we look at what happens to methane, or more specifically the carbon in methane, it loses bonds to hydrogen and as a product gains a bond to oxygen or gains a triple bond to oxygen.

00:54 But in any case, it's gaining bonds to oxygen throughout the course of the reaction.

00:59 Whenever something gains bonds to oxygen, it has been oxidized or it's undergone oxidation.

01:06 So methane has been oxidized here.

01:10 So anytime we talk about oxidation, it's a loss of electrons.

01:15 So where do those lost electrons go? they have to go then to the water.

01:20 And if we look at what happens to the hydrogen specifically in the water molecule, as it progresses throughout the reaction, it loses bonds to oxygen to become hydrogen gas.

01:33 And anytime also we see a loss of bonds to oxygen, just as gaining of bonds to oxygen means oxidation's taken place.

01:41 If we lose bonds to oxygen, that means a species has undergone reduction.

01:47 And so water here is reduced or undergoes reduction.

01:51 It's the species that's reduced.

01:53 There are a couple of other terms.

01:55 You should be familiar with, oxidizing agent, reducing agent.

02:00 So an oxidizing agent is always the thing that gets reduced throughout the course of a reaction.

02:06 So who is reduced? water.

02:09 Therefore, water is our oxidizing agent in this example.

02:14 A reducing agent gets oxidized.

02:17 Who is oxidized? methane was.

02:20 Therefore, methane is the reducing agent in this example.

02:29 In the second example, we're looking at silver nitrate and copper reaction here.

02:36 And here it kind of is a little more useful to look at assigning oxidation numbers to be able to see where the electrons are transferred in this reaction.

02:45 So copper in its elemental form has an oxidation number of zero.

02:50 Throughout the course of the reaction, it becomes copper nitrate.

02:54 Nitrate ion has a minus one charge and since there are two of them, they contribute minus two over to the molecule.

03:01 So copper then has a plus two charge in the copper nitrate molecule.

03:08 So anytime there's an increase in oxidation number throughout the course of the reaction from reactant to product, copper goes from zero to plus two.

03:18 That's an increase in oxidation number.

03:21 That's a sign that oxidation has taken place.

03:24 Therefore, copper is oxidized in this reaction.

03:29 And if we go to our terminology up here, oxidizing or reducing agent? oh, i bet you can see here, okay, the thing that gets oxidized is our reducing agent.

03:40 Therefore, since copper is oxidized, it is the reducing agent in this example.

03:46 How about the silver? all right? the silver goes from a plus one charge in the silver nitrate ion to, remember copper was zero in its elemental form, so silver in its elemental form will be zero...

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