Class 10 Chemistry (India)
Oxidation and reduction (Conventional definition)
Let's understand the old definition of oxidation and reduction. Created by Ram Prakash.
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- So it isn't necessary for either oxygen or hydrogen to be involved in either oxidation or reduction, as long as there is a gain or loss of electrons, right?(5 votes)
- Yep, it isn’t always necessary that oxygen or hydrogen is involved as long as electrons are lost or gained.
Oxidation can also be defined as the addition of a non-metal or electronegative element.
Reduction is also the addition of a metal or electropositive element.(7 votes)
- if hydrogen can both gain or lose an electron, then why is loss of hydrogen an oxidation reaction?(3 votes)
- remember that this is an old definition
You are right in saying that hydrogen can gain an electron(like a non metal] and loose an electron(like a metal]
It means that loss of hydrogen can either be an oxidation or reduction reaction
It just depends on the reaction
According to modern definition oxidation is simply removal of electrons
Using this definition you will be able to easily find whether loss of hydrogen is oxidation or reduction
in this link https://www.khanacademy.org/science/class-11-chemistry-india/xfbb6cb8fc2bd00c8:in-in-redox-reactions/xfbb6cb8fc2bd00c8:in-in-oxidation-number/v/oxidation-state-trends-in-periodic-table
Sal explains at3:43why hydrogen is a special case
Hope it helps!(1 vote)
- MnO2 + 4HCl → 2 + 2H2O + Cl2
Identify the substance oxidized in the above . equation.
(d) MnO2(1 vote)
- here HCl is oxidized to Cl2
This is because hydrogen is removed from HCl
which is considered as oxidation according to classical idea
therefore option B is the answer
Also MnO2 gets reduced to 2H2O
since oxygen is removed and hydrogen is added(1 vote)
- The definitions given in my book are the 'old' ones, describing only addition/ removal of oxygen/ hydrogen. Which definition is more widely accepted?(0 votes)
- The second one. The old one is just a subset of the 2nd definition.(0 votes)
- what are oxidising and reducing agents ?(0 votes)
- Species that get oxidized or undergo the loss of electrons are reducing agents . As they help the other species (element, compound, molecule) to get reduced, they are called reducing agents, and oxidizing agents are those which undergo the gain of electrons or reduction for the other species in the reaction to get oxidized(0 votes)
- oxidation is oxygen added/hydrogen removed and reduction is oxygen is oxygen removed/hydrogen added ? this is definitely not the right definition of oxidation and reduction.
Oxidation : losing electron, increase in oxidation number (because electron is negative charged, atom become positive charged, thus the oxidation number increased)
Reduction : gaining electron, decrease in oxidation number(0 votes)
- The definitions he talked about were the conventional definitions and now they are old and are now not in use but that does not mean that the old definitions were wrong.(5 votes)
we humans are very curious we have been trying to find out patterns in almost everything we look up at stars and see if there is any pattern in them and indeed we did find some patterns over there and similarly we have been trying to look up at all the chemical reactions and trying to see if there is any pattern that exists between them and we did find many patterns over there and today we are going to talk about one of those patterns so we saw that there are some certain chemical reactions in which oxygen gets added and then there are certain chemical reactions in which oxygen is removed and we gave them special names we call them oxidation and reduction reactions oxidation meaning oxygen is getting added oxidation oxygen is added and reduction is the opposite of that it just means that oxygen is removed well there are many more things happening under oxidation and reduction and that's what exactly we are going to talk about in this particular video so let's begin first let's look at a few examples and see if we are able to identify oxidation reactions and reduction reactions so here I have a few examples but before I solve and show it to you why don't you pause the video and see it for yourself now if you have given it a try let's see this is my first example here I see that magnesium is reacting with oxygen to give me magnesium oxide so here I can see that oxygen is getting added to this metal here right so this reaction is going to be oxidation oxygen is getting added right now this is the second example here I see that zinc oxide is reacting with carbon and giving zinc and carbon monoxide so if I focus on zinc so see initially it was combined with oxygen but finally it has lost the oxygen so zinc is losing its oxygen so we can say that zinc is going through a reduction reduction reaction okay but over here in the same reaction if you focus on the carbon see carbon was without oxygen to begin with but after the reaction it is combined with oxygen so okay there is oxygen addition happening to carbon so yeah so this means that in the same reaction we can see that carbon is going through oxidation reaction and yes a same reaction can have both oxidation and reduction and we call such type of reactions as redox reactions and only we will talk about this reaction in much detail in a separate video now let's come back to the third reaction over here we see copper oxide is reacting with hydrogen to give us copper and water so if I focus on copper so before reaction it was combined with oxygen but after reaction it has lost its oxygen that means oxygen is being lost by copper so over here I will say that copper is going through reduction reaction reduction reaction but if we focus on this hydrogen see hydrogen did not have oxygen to begin with but after the reaction it is combined with an oxygen so I will say that hydrogen is going through oxidation reaction oxidation now this is the fourth one here we see that oxygen is getting added to copper and we get copper oxide so this reaction is oxidation reaction copper is going through oxidation reaction over here we see that oxygen is getting added to sodium and we get sodium oxide so here I would say sodium is going through oxidation reaction so now we have solved our problem now let's look at what else is there in oxidation and reduction so so far we have seen the oxygens addition is termed as oxidation and oxygens removal is termed as a reduction but you know what we can even define oxidation and reduction in terms of hydrogen yes we say whenever hydrogen is removed we call it as oxidation reaction and whenever hydrogen is added we call it as a reduction reaction and I know that you might be wondering like why are we talking about hydrogen where as how doesn't even coming from and why is the effect of hydrogen opposite of oxygen I mean in case of oxidation oxygen needs to be added whereas hydrogen needs to be removed or in case of reduction oxygen needs to be removed whereas hydrogen needs Harrod so why is this opposite effect happening so don't worry I will try to give you some insights about these questions towards the end of the video but for now let's try to understand this new definition and try to solve some problems now here I have some examples and before I solve it why don't you pause it and try it yourself just remember one thing okay the effect of hydrogen will be opposite of the effect of oxygen meaning in case of oxidation oxygen was getting added whereas in terms of hydrogen we will say that hydrogen will be getting removed similarly in case of reduction oxygen was getting removed whereas in case of hydrogen we will say hydrogen will be getting added so now go ahead pause the video and try it yourself now if you have tried it let's see in the first equation I have a compound over here that has many hydrogen's and after the reaction I see that it has lost some hydrogen so meaning this compound is losing hydrogen hydrogen is being removed from here so which reaction will this be so remember removal of hydrogen could be thought in terms of addition of oxygen and any addition of oxygen is oxidation so here this compound is going through oxidation let's write it down this compound is going through oxidation similarly over here I see carbon monoxide is reacting with hydrogen and hydrogen is getting added to it we get one single compound right so here I would say that says hydrogen is getting added over here then this reaction will be so addition of hydrogen can be thought in terms of removal of oxygen which is reduction reaction so here carbon monoxide is getting reduced let me just write it this is getting reduced okay now let's look at the third example here I see that you know methane was reacting with oxygen so to see methane had four hydrogens but after the reaction I see carbon has lost all the hydrogen's here carbon has lost all the hydrogen's right so which reaction is this hydrogen is getting lost removed okay so hydrogen removed is like saying oxygen added which is oxidation so yeah here carbon is getting or see iced so now we have spoken a lot about oxidation and reduction reaction we have defined them both in terms of oxygen and also in terms of hydrogen we still have a question see we name the reactions in which oxygen was getting added as oxidation why did we give the same name to the reactions in which hydrogen was getting removed but see in reality both of these definitions are kind of old definitions and the new definition of oxidation and reduction is based on electron loss or electron gain and that will help you understand where is hydrogen coming from so let's talk about that very briefly so if you take an element and you burn it in air it reacts with the oxygen present in the air to form an oxide and I have some examples here over here you can see that magnesium when burned in air it reacts with the oxygen to form magnesium oxide and since over here oxygen is getting added to magnesium we call this reaction as oxidation reaction addition of oxygen now when we were defining oxidation as addition of oxygen we did not know anything about electrons we did not know what is happening between the electrons of these two elements are they being transferred or shared or anything at all but later on when we found out we saw something like this when magnesium was combining with oxygen it had to lose his electrons to oxygen similarly in the case of sodium oxide when sodium was getting added to oxygen both the sodium atoms they were losing one one electron to oxygen similarly we saw in all the oxidation reactions that the elements they were losing electrons to oxygen either fully or either partially but they were losing electrons so this helped us upgrade our definition of oxidation reactions we no longer depend on oxygen for that matter as long as in a reaction an element is losing electron we see that element is going under oxidation reaction and it could be doing so because of any reason because of oxygen because of hydrogen because of sulphur nitrogen any other compound as long as it loses electron we will call it oxidation so it turned out and whenever we add oxygen the element loses electron whenever we add oxygen similarly whenever hydrogen is removed the element was losing electron so that is also termed under oxidation you could find something very similar for sulfur for nitrogen for other compounds also but now you know why hydrogen came into picture or you have some idea at least now see this is a new definition for oxidation and reduction and we are not going into detail of it there is much more to this and we have discussed that in a separate video in this particular video we are only talking about the conventional definition of oxidation and reduction which is oxidation is where oxygen gets added or hydrogen is removed and reduction are those reactions in which oxygen is removed or hydrogen is added