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Video transcript

in this video we are going to talk about the nature of metal oxides and by nature I mean whether they are acidic or basic in nature well let me kill this suspense metal oxides they are basic in nature and by that I mean they behave as basis some of the metal oxides even get used as antacid and they can be used to cure the buildup off to neutralize the buildup of excess acid in our stomach just like basis so let's see how metal oxides behave as bases so you would recall that when an acid and a base react they will neutralize each other's effect and finally form a salt and water so if you are given with a chemical some random chemical that is reacting with an acid and forming a salt and water then you can be sure that this chemical has to be a base because only a base can react with an acid to form salt and water so now let's take an example of metal oxide and see how it reacts with an acid so for starters I'm going to take the acid HCl and I'm going to react this with sodium oxide ne - OH sodium is a metal and this is a metal oxide now can you imagine what are the products that will be formed in this case pause the video and think about this so here there will be a double displacement reaction the ions will exchange position sodium it will get attracted now to chlorine and finally form sodium chloride any CL which is a soil and hydrogen will get attracted to oxygen and finally will get water h2o let me balance this equation here we have two sodium so two over here two chlorine so two over here two hydrogen one oxygen yes this is balanced so over here you can see that sodium oxide which is a metal oxide this is reacting with an acid to give me and water so based on this previous reaction I can see that metal oxide has to be a base because it's reacting with acid to give salt and water right let's take one more example just to confirm things this time I'm going to take calcium oxide calcium oxide calcium is also a metal and this is a metal oxide and I'm going to react this with the acid HCL okay so here also double displacement reaction will happen and the ions will exchange position calcium will get attracted to chlorine and we will get calcium chloride cacl2 and hydrogen will get attracted to oxygen and we will get h2o okay let's quickly balance this equation so here chlorine is 2 so let's put 2 over here now hydrogen is 2 2 oxygen oxygen calcium calcium so yes this is a balanced chemical reaction here also the metal oxide is reacting with an acid to give me a salt and water and since we are getting salt in water we can see that this metal oxide is a base so we can say in general metal oxides they are basic in nature they behave as bases and this means that they can neutralize acid and form salt and water so metal oxides are basic in nature is that it well not really there are some exceptions this is chemistry there are always exceptions there are some metal oxides that not only behave as bases but can also behave as acids they can behave as acids and react with a base to also give salt and water let's look at their example so first example is aluminium oxide so let me first of all show you how it behaves as a base al2o3 aluminium oxide and let's react this with HCl hydrochloric acid and in this case we will get aluminum chloride which is a salt alcl3 plus water will be formed h2o let's balance this equation so here we have two aluminum so here two now I have 3 to the 6 6 chlorine so 6 HCL now 6 hydrogen so I'll write 3 over here 3 to the 6 3 oxygen 3 oxygen yes this is balanced so for sure aluminium oxide is acting as a base because it is reacting with the acid HCL to give a salt and water so it can only be a base now let's look at an example where aluminium oxide acts as an acid so here I have taken aluminium oxide al2o3 this time I'm going to react this with a base sodium hydroxide and this time I will get a weird salt I'm calling it weird because I always keep forgetting it's formula any lo2 sodium aluminate and with this water will be formed h2o let's balance this equation so here I have two aluminium so I'll make this 2 now 2 sodium I've got 2 over here now this reaction is balanced so over here you can see that aluminium oxide is reacting with the base to give me salt and water and we know that if something reacts with the base to give salt and water that can only be an acid so in this example aluminium oxide is acting as an acid whereas in this example aluminium oxide is acting as a base so yes aluminium oxide is an exception it acts both as an acid and a base we have one more example that is zinc oxide zinc oxide also acts as both acid and base here in this example zinc oxide is reacting with an acid to give a salt in water therefore here it is acting as a base whereas in this example zinc oxide is reacting with a base to give a salt and water so here zinc oxide is acting as an acid so this is also an exception so so far we have seen that metal oxides they are generally basic in nature whereas there are some exceptions some metal oxides are called amphoteric meaning they can act both as acid and base and we saw the examples of them aluminium oxide and zinc oxide okay we started with the example of sodium oxide any two Oh and we saw that this is basic in nature meaning this will react with an acid to give a salt and water and from our previous experiments we have seen that sodium hydroxide naoh this is a base this will also react with an acid to give us salt and water but you might be wondering hey what's the connection between sodium oxide and sodium hydroxide so see the connection is if you mix sodium oxide in water it is going to react it is going to dissolve completely in water and finally we will get sodium hydroxide so the key thing that I am trying to tell you is that there are few metal oxides which are soluble in water soluble in water and then there are few metal oxides that are insoluble in water now what do I mean by soluble and insoluble so see for example if you take a spoon of sugar and you mix it in water the sugar is going to completely dissolve in water and it will be completely mixed something similar happens with certain metal oxides such as sodium oxide or potassium oxide keto or calcium oxide Co these are water soluble these will mix in water and finally we will get hydroxides whereas there are certain other metal oxides that are insoluble in water for example magnesium oxide or al Mooney oxide al2o3 these will not dissolve in water well magnesium oxide it does dissolve in water to a very little extent okay it's almost negligible so for example if you want to make sodium hydroxide what you can do is burn sodium to get sodium oxide just be very careful that this reaction is very explosive okay and then mix the sodium oxide in water and then you will get your sodium hydroxide the base now let's summarize the video in this video we saw what is the nature of metal oxides and we also saw that there are some metal oxides that are both acidic and basic in nature what do we call such oxides as and can you give two examples of such oxides we also saw that some metal oxides are soluble and some are insoluble I hope you can remember one example at least of both of these now if you can answer these questions well and good and if you could not don't worry you can go back and watch the video again