Write a balanced equation for the redox reactions. (a) The...

Key Concepts

Electron Transfer

Electron transfer is the fundamental process in redox reactions, where electrons are exchanged between different chemical species. The accurate accounting of electrons is crucial in balancing redox equations, as it ensures that the total number of electrons lost in the oxidation half-reaction equals the number gained in the reduction half-reaction. This concept reinforces the law of conservation of charge and is pivotal for understanding reaction mechanisms and energy changes in chemical reactions.

Redox Reactions

Redox reactions, short for reduction-oxidation reactions, involve the transfer of electrons between chemical species. In these processes, one species undergoes oxidation (loss of electrons) while another undergoes reduction (gain of electrons). Understanding redox reactions is essential in chemistry because they underpin a wide variety of chemical processes, including energy production, corrosion, and organic transformations.

Oxidation States

Oxidation states are numerical values assigned to atoms in a compound to help track the electron transfer in redox reactions. By determining the oxidation numbers, one can identify which atoms are oxidized and which are reduced. This systematic approach is crucial for analyzing the electron flow in complex reactions and ensuring that all atoms and charges are balanced in the overall equation.

Half-Reaction Method

The half-reaction method is a widely used strategy for balancing redox reactions. It involves splitting the overall reaction into two separate half-reactions—one for oxidation and one for reduction. Each half-reaction is balanced independently for mass and charge, typically by adding electrons, water, hydrogen ions (in acidic conditions), or hydroxide ions (in basic conditions). The two balanced half-reactions are then combined to give the balanced overall reaction, ensuring that electrons are conserved.

Balancing in Acidic Solutions

When balancing redox reactions in acidic solutions, additional species such as H+ ions and water (H2O) are introduced to facilitate the balancing of hydrogen and oxygen atoms, respectively. This method ensures that all atoms and charges are accounted for and that the reaction adheres to the principles of mass and charge conservation in a medium with an excess of protons.

Transcript

00:01 So we're going to write the redox reaction between aluminum and hydrogen iodide or hydriotic acid.

00:07 So this will give you aluminum iodide and it will give you hydrogen gas.

00:16 Now, if you leave it like this, you cannot balance it in a redux format.

00:22 So you can balance it really easy this way.

00:24 You have three iodines and you have two hydrogens.

00:26 So you need six his.

00:28 And then now i need two i3s.

00:33 So that will give me two times three, six i lines, six i -lines, two hydrogens, two hydrogens, and then i need two aluminums.

00:42 So this is to balance it regularly.

00:45 To balance in the redox format, you need the net -ionic equation.

00:48 So we're going to ride, because this is a redox reaction, we need to balance it in the redox format, plus, h -i, h -plus, will give me a .l plus 3 and h2 gas.

01:08 Now, if you notice, i got rid of the i -minus, because i -minus is in the i -minus ion in both sides, so it's an expected ion, so we can get rid of it.

01:17 So we're going to write this, we're going to balance this as a redox reaction.

01:22 So step one is to split main reaction into half reactions.

01:30 Explain main reaction into two into two half reactions and what you're going to do is you're going to do element to element so we're going to do aluminum to aluminum plus three and then we do h plus to h2 so that's step one step two is to balance any non -hydrogen or oxygen element so anything that's not hydrogen or oxygen gets balanced first.

02:11 So aluminum, one aluminum, one aluminum.

02:13 And this is hydrant, so we balance it later.

02:17 Step 3, balance any oxygen by adding water.

02:28 We don't have oxygen, so we can skip this step.

02:31 Step 4, balance hydrogens by adding, just regular hydrogens, by adding h -buss.

02:44 And this one already has an h plus so we're going to add since i have two hydrants i'm going to multiply this by two it's the five balanced charges by adding electrons so i have three electrons on this side so i'm going to add three electrons so i have a charge of zero on this side a charge of plus three on this side so i'm going to add three electrons and then on the bottom equation i have plus two and then here i have zero so i need to add two electrons so when you write -have reactions, you're able to see what's being oxidized and what's being reduced, which is what a redux equation is.

03:31 Step 6 is to multiply both reactions to get equal number of electrons.

03:42 Number of electrons.

03:45 So i'm going to multiply the first one by 2 and then i'm going to multiply the bottom by 3.

03:51 And that way i have 6 electrons on both reactions.

03:54 So two aluminums plus two yields, not plus.

04:01 So it's going to be yields, 2 al plus 3 plus 6 electrons, and the bottom one will be 6 electrons plus 6 hydrogen ions will give me 3h2.

04:15 And then step 7 is to cancel electrons.

04:21 Because if you cannot cancel the electrons, then it means you do not have a redox reaction.

04:26 Step 8 if you have anything that is duplicate so for any duplicates which this one doesn't have it but we're gonna write it in here because this is this step so for any duplicates meaning let's say we had two waters on both sides or two hydrogens or two h pluses right so for any duplicate if on the same side you're gonna add them if on opposite sides then you're gonna subtract then we're going to subtract all right, so this one, let's check, there's no duplicates.

05:09 So step nine is to combine into one equation into one equation.

05:22 So i have 2 a .l plus 6h bus.

05:29 We yield 2ao plus 3 plus 3h2, which means that they should have been a 3 up here.

05:37 There we go.

05:38 Now that's balanced.

05:39 So this equation, this equation should look pretty much.

05:42 The same except for the iodine right but this method was just balancing it regularly except it was missing the three right this should be six hydrogen and then this equation this way is balancing the redox format since it tells us the redox equation and the last step is to check charges so we have a total charge of six plus in this side and then two times three is six so we have a total charge of six plus on this one so this equation is balanced so for b we have reduction of vo plus 2 to v.

06:19 V.

06:19 Plus 2 in an aesthetic solution.

06:21 And the reducing agent is sync, which means that sink is being oxidized, which means that sink is going to lose electrons, and its common form a sink plus 2.

06:31 It's a normal ion that it forms if you're not given 1.

06:34 So sync commonly forms sync plus 2.

06:37 With the transition metals, if you're ever in doubt, they usually most commonly form plus 2.

06:41 They can form multiple ones, but plus 2 is the most common one.

06:44 And remember the reducing agent means that this is being oxidized.

06:49 So they actually given us the half reactions which is really nice.

06:54 So vo plus two is the first half reaction to be plus three and then sync to sync plus two.

07:02 So now we follow the steps.

07:05 So split a many reaction into two half reactions already have the two half reactions.

07:09 Balance any non -hydrogen oxygen elements.

07:12 So we'll balance panadian first.

07:14 So one and then sync one and one.