Module 2 - Balancing Redox - Oxidation Number Method - 1

Summary

The video script discusses balancing redox reactions, emphasizing the importance of considering charges on atoms and substances. It outlines two methods for balancing: the oxidation number method and the half-reaction method. The script provides a detailed step-by-step guide on how to balance redox equations, including assigning oxidation numbers, identifying oxidation and reduction, determining changes in oxidation numbers, balancing electrons, atoms, and charges. An example is used to illustrate the process, showing how to balance a reaction involving iron and permanganate ions.

Takeaways

• 🔬 Balancing redox reactions involves considering the charges of atoms or substances, which is different from balancing neutral equations.
• 🌐 The law of conservation of mass must be obeyed, along with balancing the number of elements and electrons in the reaction.
• 📐 There are two methods for balancing redox equations: the oxidation number method and the half-reaction method.
• 📖 The oxidation number method tracks changes in oxidation numbers of elements involved in the reaction.
• 📝 Assign oxidation numbers to each atom in the equation as the first step in balancing redox equations.
• 🔍 Identify which substances undergo oxidation and reduction by observing changes in oxidation numbers.
• 🔄 Determine the changes in oxidation numbers for elements involved in the reaction.
• ⚖️ Balance the electrons by adjusting coefficients to ensure the number of electrons lost is equal to the number gained.
• 🌐 Balance the atoms and charges by adjusting coefficients and possibly adding substances like water to the reaction.
• 💧 Adding water to a reaction can help balance the number of oxygen and hydrogen atoms.
• 🔋 Ensure that both the number of atoms and the total charges are balanced in the final equation.

Q & A

Why is it important to consider charges when balancing redox reactions?

Charges are important in redox reactions because they indicate the transfer of electrons, which is the essence of redox processes. Balancing charges ensures that the law of conservation of charge is upheld, meaning the total charge on both sides of the reaction must be equal.

What are the two methods mentioned for balancing redox reactions?

The two methods for balancing redox reactions are the oxidation number method (also known as the oxidation statement method) and the half-reaction method (also known as the ion-electron method).

How does the oxidation number method work?

The oxidation number method works by tracking changes in the oxidation numbers of the elements involved in the reaction. It involves assigning oxidation numbers to each atom, identifying substances undergoing oxidation and reduction, determining the change in oxidation numbers, and then balancing the electrons and atoms.

What is the first step in balancing a redox reaction using the oxidation number method?

The first step in balancing a redox reaction using the oxidation number method is to assign oxidation numbers to each atom in the equation.

How do you identify which substance undergoes oxidation and which undergoes reduction?

You identify oxidation and reduction by observing changes in oxidation numbers. A substance that loses electrons (becomes more positive) undergoes oxidation, while a substance that gains electrons (becomes less positive) undergoes reduction.

What does it mean for a substance to be the oxidizing agent or the reducing agent?

A substance is the oxidizing agent if it causes another substance to be oxidized (loses electrons). Conversely, a substance is the reducing agent if it causes another substance to be reduced (gains electrons).

How do you balance the number of electrons in a redox reaction?

To balance the number of electrons, you equalize the total increase in oxidation numbers with the total decrease. This is done by adjusting the coefficients of the reactants and products to ensure the number of electrons lost by the oxidized substance equals the number gained by the reduced substance.

Why is it necessary to balance atoms and charges after balancing the electrons?

After balancing the electrons, it's necessary to balance atoms and charges to ensure that the law of conservation of mass is upheld. This involves adjusting coefficients and possibly adding substances like water to balance the number of atoms and ensure that the total charge on both sides of the equation is equal.

What role does water play in balancing redox reactions?

Water can be added to a redox reaction to balance the number of oxygen and hydrogen atoms. It also helps in balancing the charges by providing additional protons (H+) or hydroxide ions (OH-) as needed.

Can you provide an example of how to balance a redox reaction involving iron and permanganate ions?

In the given script, iron (Fe) goes from an oxidation state of +2 to +3, and manganese (Mn) goes from +7 to +2. The changes in oxidation numbers are +1 for iron and +5 for manganese. By balancing the electrons, the coefficients for iron and manganese are adjusted to 5 and 1, respectively. Then, water is added to balance the oxygen atoms, and additional hydrogen ions are added to balance the charges, resulting in a balanced redox reaction.

Outlines

00:00

🔬 Balancing Redox Reactions

This paragraph introduces the concept of balancing redox reactions, which involve the transfer of electrons and are not neutral. It explains that in addition to the law of conservation of mass, one must also balance the number of electrons. Two methods are mentioned for balancing redox reactions: the oxidation number method and the half-reaction method. The oxidation number method involves tracking changes in oxidation numbers of elements involved in the reaction. The steps include assigning oxidation numbers to each atom, identifying oxidation and reduction, determining changes in oxidation numbers, balancing electrons, and balancing atoms and charges. An example is given where the oxidation numbers of iron and permanganate are calculated before and after the reaction.

05:02

📚 Identifying Oxidation and Reduction

The paragraph discusses how to identify which substances undergo oxidation and reduction in a redox reaction. It uses the example of iron (Fe) and permanganate (MnO4-) to illustrate the process. Iron's oxidation state increases from +2 to +3, indicating it releases an electron and is being oxidized, thus acting as a reducing agent. Conversely, permanganate's oxidation state decreases from +7 to +2, indicating it gains an electron and is being reduced, thus acting as an oxidizing agent. The paragraph also explains how to determine the changes in oxidation numbers and balance the electrons by adjusting the coefficients of the reactants.

10:04

🌐 Balancing Atoms and Charges

This paragraph focuses on the final steps of balancing a redox reaction, which include balancing the number of atoms and charges. Using the example from the previous paragraph, it shows how to add water (H2O) to balance the oxygen atoms and how to add hydrogen ions (H+) to balance the hydrogen atoms. The charges are then balanced by ensuring that the total positive and negative charges on both sides of the reaction are equal. The final balanced redox reaction is presented, showing the reactants and products with their respective charges, demonstrating that both atoms and charges are balanced.

Keywords

💡Balancing Redux

Balancing Redux refers to the process of ensuring that a redox (reduction-oxidation) chemical reaction is balanced in terms of both the number of atoms and the charge. In the video, this is a central theme as the speaker explains how to balance such reactions by considering both the atoms and their charges, which is a departure from simpler balancing methods taught in high school chemistry.

💡Charges

Charges in this context refer to the electrical property of atoms or ions that is either positive or negative. The video script mentions that charges must be considered when balancing redox reactions, which is different from balancing neutral chemical equations. Charges are crucial for ensuring that the total positive and negative charges on both sides of the equation are equal.

💡Redox Reaction

A redox reaction is a type of chemical reaction that involves the transfer of electrons between two species. The video emphasizes the importance of balancing redox reactions by considering the changes in oxidation numbers and the transfer of electrons, which is a key aspect of understanding redox processes.

💡Oxidation Number

Oxidation number, also known as oxidation state, is a measure of the degree of oxidation of an atom in a substance. In the script, the speaker describes how to assign oxidation numbers to each atom in a redox reaction, which is a fundamental step in the balancing process.

💡Oxidation

Oxidation is a chemical process where a substance loses electrons. The video uses the example of iron (Fe) increasing its oxidation number from +2 to +3, indicating that it has lost an electron and thus undergone oxidation.

💡Reduction

Reduction is the gain of electrons or a decrease in the oxidation state by a molecule, atom, or ion. In the script, manganese (Mn) decreases its oxidation number from +7 to +2, indicating that it has gained electrons and thus undergone reduction.

💡Half-Reaction Method

The half-reaction method is one of the two methods for balancing redox reactions mentioned in the video. It involves breaking the redox reaction into two half-reactions, one for oxidation and one for reduction, and then balancing each half separately before combining them.

💡Ion-Electron Method

The ion-electron method is another term for the half-reaction method. It emphasizes the importance of tracking the movement of electrons in the form of ions during the redox reaction, which is essential for balancing the charges.

💡Permanganate

Permanganate is a chemical ion with the formula MnO4-. In the video script, permanganate is used as an example of a substance that undergoes reduction in a redox reaction, changing its oxidation state and serving as an oxidizing agent.

💡Law of Conservation of Mass

The law of conservation of mass states that matter cannot be created or destroyed in an isolated system. The video script mentions this law to emphasize that, in addition to balancing the charges, the total number of atoms of each element must remain constant in a balanced chemical equation.

💡Balancing Electrons

Balancing electrons is a step in the redox reaction balancing process where the number of electrons lost by one reactant must equal the number gained by another. The video script illustrates this by showing how to balance the electrons transferred between iron and permanganate.

Highlights

The necessity to consider charges in balancing redox reactions.

Redox reactions involve the transfer of electrons, affecting the balance of chemical equations.

Two methods for balancing redox reactions: oxidation number method and half-reaction method.

Oxidation number method tracks changes in oxidation numbers of elements involved in the reaction.

Assign oxidation numbers to each atom in the equation for balancing redox equations.

Identify substances undergoing oxidation and reduction based on changes in oxidation numbers.

Determine the change in oxidation numbers for elements involved in the reaction.

Balancing the electrons involves adjusting coefficients to match changes in oxidation numbers.

Balancing atoms and charges requires adjusting for the presence of ions and their charges.

The example provided illustrates the step-by-step process of balancing a redox reaction.

The importance of balancing both the number of atoms and the charges in a redox reaction.

The role of water in balancing the oxygen atoms in a redox reaction.

The inclusion of hydrogen atoms to balance the charges in the reaction.

The final balanced redox reaction, showing the transfer of electrons and charge balance.

The law of conservation of mass must be obeyed in addition to balancing elements and electrons.

The significance of the oxidation number method in balancing redox reactions involving charged species.

The practical application of balancing redox reactions in chemistry education.

Transcripts

Now let's proceed to balancing Redux

reaction when you have um an example Uh

the first examples you notice that the

substances or the atoms are not neutral

you observe that the atom or the

substance has charges The question is

will those charges affect

Uh the balancing of

the reaction Okay so at this point We

will now consider the charges of these

atoms or substances because usually when

you were um in junior high school or

senior high school you balance equations

that are Uh neutral meaning They don't

have charges but at this point we have

to consider it now ah

at this point We will now um call it as

a redox reaction whenever we balance the

chemical equation We must obey Again the

law of conservation of mass in addition

to balancing the number of elements in

the chemical reaction one must also

consider balancing the number of

electrons in the in the process and

there are Two methods for balancing the

redox re equations So it is the

oxidation number method also known as

oxidation statement method and the half

reaction method also known as the um ion

electron method so in the oxidation

um number

method It is a technique used to balance

Redux reactions which are chemical

reactions involving the transfer of

electrons Now it works by tracking the

changes in oxidation numbers of the

elements involved in the reaction and

there are some steps that you can

utilize in order to obtain the balance

um redox equation so first is Uh You

have to assign the oxidation number to

each atom in the equation so again we

have to assign the oxidation number to

balance the Uh atoms Okay then we have

to identify which substance undergo

oxidation and which substance undergo

reduction after Identifying the

oxidation and reduction we have to Uh

determine the change in the oxidation

number and after we identify the the

change of oxidation number we have to

balance the

electrons Then after such we have to

balance the atoms and charges so let's

have um some examples so first Uh

considered the unbalance Redux reaction

Okay so take note that it is not your

usual chemical equations where you have

neutral substances or neutral atoms in

this example you notice that each or I

think all of the atoms or substances

have Uh charges So how to balance this

Okay based on what I've discussed You

have to first identify the oxidation

number to each atom in the equation so

we have to identify the oxidation number

of each Okay so first is the ion ion is

an ion and it has a charge of positive

two therefore it has an oxidation number

of pos 2 next is you have permanganate

Okay so the permanganate ah you have

manganese and you have oxygen Okay so

the oxygen again rule number seven has

an oxidation number of

negative and for manganese if you

compute this one it has an oxidation

number of solid compute mn

plus 4 Oxygen is equ to -1 by

substitution for

-2

mn -1 So this is -8

mn -1 So this is

mn -1

transpose yung ne 8 magiging pos 8 so

you have pos 7 so therefore the

manganese and oxidation number of pos 7

now after the reaction the Iron now has

an oxidation number of pos

3 and then the manganese now has

oxidation number

positive Okay so at this point we were

able to identify the number each element

in the equation second is we have to

identify which undergo oxidation and

reduction so notice that the ion mula sa

pos 2 naging pos 3 it becomes more

positive the reason for that is it

releases electron since the ion releases

electron it undergo oxidation process

this

oxidation Okay so meaning it is the one

being oxidized and at the same time it

is

Uh the reducing agent or the reductant

on the other hand if you notice that the

Mangan mula sa pos 7 it now becomes pos

2 The Reason mula sa pos 7 to pos 2 is

humaba ang kanyang Ah yung kany naging

less positive siya because it

since it receives electron it undergoes

a reduction

process TH the permanganate or mno4 is

our is being oxidized and

Our oxidizing Agent Third is we have to

determine the changes in oxidation

number so si ion

ah mula sa

positive 2 naging pos 3 So ang change

niya ay 1 lang Okay tapos si manganese

naman mula sa pos 7 naging

positive 2 therefore ang kanyang change

ay pos

5 Okay so now we were able to determine

the oxidation number the change of

oxidation number of the manganese and

the Iron Okay so next we have to balance

the electrons so notice that the change

of electron is not the same okay ang isa

positive Ah isa one Ay yung isa ay 5

para ma-balance iyan Okay gagawin natin

' ba si

ano si ion ay ay isa pero si manganese

ay lima Okay so paano ba natin ito

ma-balance

what we can do is ' ba si Iron ay isa

ang kanyang kulang Okay so therefore

maglalagay tayo ng one ah one ang

kanyang change So maglalagay tayo ng one

Dian sa mga Mangan coefficient na one si

Mangan naman ay five un change Okay

therefore lalag natin ng five

coefficient si

Iron

okay

okay So ngayon we were able to balance

the number of

electrons third ah fifth and last we

have to balance the number of atoms and

charges so notice na si ion

Okay si IR

okay ngayon Meron ka ng five electron ah

five sa reactant and five sa product si

manganese dito merong isa sa reactant at

meron din Isa siya sa ah sa

product Okay pagdating dito kay

oxygen Okay merong apat sa reactant pero

wala sa product

therefore we have to balance Okay notice

na para ma-balance siya magdadagdag tayo

ng

water

H2O para mabalanse sila

therefore Okay kung titingnan natin ang

water ha Titingnan natin ang water Meron

yang dalawang hydrogen at merong apat ah

Meron yang dalawang hydrogen at Meron

yang isang oxygen Okay pero ang kulang

natin ay

AP na oxygen so therefore dahil apat ang

kulang natin na oxygen so Dapat apatin

dito Okay so apatin dito therefore

maglalagay tayo dito ng apat na water

dito Okay para ma-balance ang oxygen So

kung titingan natin ngayon Apat ang

oxygen sa reactant apat din ang sa

product so Balance na ang oxy

however notice na when you add water you

also include aside from oxygen you also

include

hydrogen Ilan ang kang hydrogen

dito 2 4 so 8 so therefore merong 8 dito

sa ano merong 8 dito

sa tawag nito dito sa product pero

walang hydrogen sa

reactant magdadagdag tayo diyan ng 8 so

magdadagdag tayo dito ng 8 na hydrogen

pero that is an ion Okay so para

ma-balance na iyung number of atom and

charges ah atoms so Balance na iyung

atom pero ngayon How about the

charges is this balance so Tingan natin

Okay so you have here ' ba you have ano

ngayun eight hydrogen

plus lima nito tapos isa Dian or kahit

wala na siguro

yan Tapos merong 5 dito tapos 1 Then you

have

4 water Okay Let us check if they are

balanced

Okay let's check muna kung balance ang

mga um elements So you have

hydrogen

ah iron you have manganese and oxygen

kung balance

pa 8 na

hydrogen 2 * 4 you have 8 iron dito ay

five Dito naman ay five habat manganese

dito one Ito naman ay one one lang dito

ha Ito ay charge Hindi siya number of

Element ha charge lang yan dito ay apat

na oxygen apat

diyan reactant and one ' ba may one yan

dito 1 * 4 so 4 so Balance na ang

atoms How about sa

charges icompute natin

Okay so dito ang charge nito ay 1 ' ba

postive 1 yan Tim 8 is + 8

Okay

2 Tim 5 is 10

posi

1 Tim 1 is - 1 Okay so therefore 8 + 10

is 18 plus - 1 you have pos

17 and Dito naman 3 5 you have

15 have 2 * 1 you have 2 both are

positive so ito ay walang charge so zero

lang Ian therefore 15 + 2 plus 0 is ah

pos 17 so ito ay positive 17 sa reactant

sa product din ay pos 17 therefore the

charges are balan thus our balance red

redox reaction will be look like this

8 h

plus plus 5

ion 2 plus plus

permanganate forming 5 ion 3 plus plus

manganese 2 plus plus water So this is

now Your balance red reaction using

oxidation number me