Which of the following reactions are redox reactions? In...

Which of the following reactions are redox reactions? In those that are, identify the oxidation and reduction processes. (a) $\mathrm{N}_{2}+3 \mathrm{Mg} \stackrel{\Delta}{\longrightarrow} \mathrm{Mg}_{3} \mathrm{N}_{2}$ (b) $\mathrm{N}_{2}+\mathrm{O}_{2} \longrightarrow 2 \mathrm{NO}$ (c) $2 \mathrm{NO}_{2} \longrightarrow \mathrm{N}_{2} \mathrm{O}_{4}$ (d) $\mathrm{SbF}_{3}+\mathrm{F}_{2} \rightarrow \mathrm{SbF}_{5}$ (e) $6 \mathrm{HCl}+\mathrm{As}_{2} \mathrm{O}_{3} \rightarrow 2 \mathrm{AsCl}_{3}+3 \mathrm{H}_{2} \mathrm{O}$ (f) $2 \mathrm{CO}+\mathrm{O}_{2} \rightarrow 2 \mathrm{CO}_{2}$ (g) $\mathrm{MnO}_{2}+4 \mathrm{HCl}-\mathrm{MnCl}_{2}+\mathrm{Cl}_{2}+2 \mathrm{H}_{2} \mathrm{O}$ (h) $\left[\mathrm{Cr}_{2} \mathrm{O}_{7}\right]^{2-}+2[\mathrm{OH}]^{-} \rightleftharpoons 2\left[\mathrm{CrO}_{4}\right]^{2-}+\mathrm{H}_{2} \mathrm{O}$

Which of the following reactions are redox reactions? In those that are, identify the oxidation and reduction processes.
(a) $\mathrm{N}_{2}+3 \mathrm{Mg} \stackrel{\Delta}{\longrightarrow} \mathrm{Mg}_{3} \mathrm{N}_{2}$
(b) $\mathrm{N}_{2}+\mathrm{O}_{2} \longrightarrow 2 \mathrm{NO}$
(c) $2 \mathrm{NO}_{2} \longrightarrow \mathrm{N}_{2} \mathrm{O}_{4}$
(d) $\mathrm{SbF}_{3}+\mathrm{F}_{2} \rightarrow \mathrm{SbF}_{5}$
(e) $6 \mathrm{HCl}+\mathrm{As}_{2} \mathrm{O}_{3} \rightarrow 2 \mathrm{AsCl}_{3}+3 \mathrm{H}_{2} \mathrm{O}$
(f) $2 \mathrm{CO}+\mathrm{O}_{2} \rightarrow 2 \mathrm{CO}_{2}$
(g) $\mathrm{MnO}_{2}+4 \mathrm{HCl}-\mathrm{MnCl}_{2}+\mathrm{Cl}_{2}+2 \mathrm{H}_{2} \mathrm{O}$
(h) $\left[\mathrm{Cr}_{2} \mathrm{O}_{7}\right]^{2-}+2[\mathrm{OH}]^{-} \rightleftharpoons 2\left[\mathrm{CrO}_{4}\right]^{2-}+\mathrm{H}_{2} \mathrm{O}$

Key Concepts

Oxidizing and Reducing Agents

In redox reactions, the oxidizing agent is the substance that gains electrons (thereby reducing itself) and causes the other species to be oxidized, while the reducing agent is the substance that loses electrons (thereby oxidizing itself) and causes the other species to be reduced. Understanding these roles is crucial for analyzing and balancing redox reactions.

Oxidation State

The oxidation state (or number) is a tool used to keep track of electron transfer in reactions. It is a number assigned to an element in a compound or ion that represents the hypothetical charge an atom would have if all bonds were completely ionic, helping to identify the changes associated with oxidation and reduction.

Reduction

Reduction is the complementary process to oxidation, where an atom, ion, or molecule gains electrons, leading to a decrease in its oxidation state. In a redox reaction, the species that gains electrons acts as the oxidizing agent.

Oxidation

Oxidation is the process in which an atom, ion, or molecule loses electrons. This process is marked by an increase in the oxidation state of the species involved. Oxidation reactions often occur simultaneously with reduction reactions in redox processes.

Redox Reaction

A redox reaction is a type of chemical reaction that involves the transfer of electrons between species, resulting in a change in the oxidation states of the elements involved. These reactions are characterized by one species undergoing oxidation (losing electrons) while another undergoes reduction (gaining electrons).

Transcript

00:02 Hi there.

00:03 In this problem, we are given several reactions, and we are supposed to identify which ones are oxidation reduction reactions, and then explain what is being oxidized and what is being reduced.

00:16 So let's go ahead and get started.

00:18 For letter a, we have n2 reacting with 3 magnesium to produce mg3, n2.

00:35 All right, to determine if this is a redox reaction, i am going to assign oxidation numbers.

00:42 Nitrogen and magnesium on the reactant side both have oxidation numbers of zero because they are uncombined elements.

00:50 On the product side, nitrogen forms an ion with a negative three charge, so that will also be its oxidation number and magnesium positive 2.

01:00 So if we look at this, this is a redox reaction because the magnesium, changes from an oxidation number of zero to an oxidation number of positive two.

01:14 So it is oxidized because it lost two electrons.

01:24 And nitrogen went from an oxidation number of zero to an oxidation number of negative three.

01:31 So it was reduced.

01:36 Let's look at letter b.

01:39 Letter b, we have nitrogen reacting with oxygen.

01:44 And that is forming 2no as the product.

01:52 Again, let's assign oxidation numbers.

01:55 Uncombined elements are zero.

01:57 Oxygen is negative 2, which means the nitrogen here must be a positive 2.

02:04 All right, so yes, this is a redox reaction because we have a change in oxidation numbers from the reactant side to the product side.

02:12 So that means a transfer of electrons.

02:15 Nitrogen goes from zero to positive two, so that means it is oxidized, and the oxygen goes from zero to negative two, so it is reduced.

02:43 All right, let's move on to letter c.

02:48 In letter c, we have 2 and 02, and that produces n2 04.

03:04 We know oxygen is negative 2, and since there are two of those, the oxidation number for the nitrogen on the reactant side is positive 4.

03:14 On the product side, the oxidation number for oxygen is still negative 2.

03:19 The nitrogen in this compound must be a positive 4.

03:23 So we notice there is not a change in oxidation numbers, so therefore this is not a redox reaction.

03:33 Let's look at letter d.

03:36 Letter d, we have sbf3, and that reacts with fluorine gas f2 to produce sb f5.

03:54 Assigning oxidation numbers, fluorine is a halogen, so it has an oxidation number of negative 1.

03:59 That means the antimony must have an oxidation number plus 3.

04:04 Fluorine is an uncombined element, so it is zero.

04:07 On the product side, flooring is negative 1.

04:10 Sb is positive 5.

04:13 All right.

04:15 So as we look at these, the fluorine is reduced from zero to negative one.

04:26 And the antimony goes from an oxidation number of plus three to an oxidation number of plus five.

04:33 So it is oxidized.

04:37 So yes, this is an oxidation reduction reaction.

04:45 Moving on to letter e.

04:48 In letter e, we have six hcl reacts with as203.

05:00 To produce 2 ascl3 plus 3h2o.

05:12 Let's assign oxidation numbers and see if we have a redox reaction here.

05:17 Chlorine is negative 1 and hydrogen has an oxidation number plus 1.

05:20 In our second compound, oxygen always has an oxidation number of negative 2 unless it's in a peroxide.

05:28 That means the as, the arsenic must be a plus 3.

05:33 On the product side, chlorine negative 1, as plus 3.

05:41 Oxygen negative 2, hydrogen positive 1.

05:45 None of our elements change oxidation numbers from the reactant side to the product side.

05:50 So this is not an oxidation reduction reaction.

05:56 Moving on to letter f...

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