 The second oxide we have, that is nitric oxide, NO. It's oxidation state, state is plus 2, OK? It is prepared by the direct combination of nitrogen and oxygen in electric arc, direct combination of nitrogen and oxygen in electric arc. Electric arc, why we use? Because we know this N202 does not combine at room temperature. If you remember, it requires very high temperature in the order of 3,000 degrees Celsius, OK? And that electric arc will produce a very high temperature with a high heat over there. So that is why it requires, OK? So it forms 2NO, electric arc. Basically, whenever you see this electric arc, it means high temperature we need for this reaction. And for that high temperature, we're using this electric arc, OK? This is one method. Another one is it is also prepared by the oxidation of ammonia with platinum catalyst. Oxidation of ammonia with platinum catalyst. The reaction is 4 NH3 with reaction with 4 NH3 with 5 O2. With platinum catalyst. And when you heat this around 750 degrees Celsius, you get NO nitric oxide plus H2O. This is the reaction we have. Now, this reaction or this method, we call it as host-walled process. Host-walled process. Properties cut less, slightly heavier than air, soluble in water. If you count the number of electrons for NO, it is an odd electron. It is an odd electron molecule, 8 plus 7, 15, OK? NO, odd electron molecule. Hence, it is paramagnetic in nature. The structure of NO, if you see, we have N double bond O. Oxygen has two lone pairs. Nitrogen has one lone pair and one electron. One note you write down into this. In liquid and solid form, nitrogen has, sorry, nitric oxide, NO. In liquid and solid form, nitric oxide, NO. Tendency 2 form, a dimer, that is N2O2. And it becomes diamagnetic and becomes diamagnetic. Next molecule, we have nitric acid, HNO3, nitric acid. Write down, in laboratory, it is prepared by, in laboratory, it is prepared by heating a mixture of alkali nitrate with concentrated S2SO4. Alkali nitrate with concentrated S2SO4. This converts into KHSO4 plus HNO3, laboratory method of preparation. For large-scale production, we use the method and the name is post-worlds process. Write down, in this reaction, we have already done it for the preparation of nitric oxide and NO. In this reaction, what happens? Ammonia is getting oxidized in presence of platinum. Ammonia is getting oxidized. So reaction, if I write down NH3 plus 502 in presence of platinum around 750 degrees Celsius temperature, 6 is not fairing pressure we use. It gives you nitric oxide NO plus H2O, and energy comes out into this, okay? Delta H, isothermic reaction. This nitric oxide is further oxidized by O2 and it gives you nitrogen dioxide, NO2. I am not writing down the balanced reaction, okay? I am just giving you the product, okay? I know further it will get oxidized by oxygen because we have excess oxygen here, converts this into nitrogen dioxide. Now, this nitrogen dioxide is dissolved in water and it gives you HNO3 plus nitric oxide, okay? Nitric oxide. So this is the preparation method. We have O2O process, okay? We get this and then it oxidized and then reacts with water. Property is colorless liquid, colorless liquid and gives a pungent smell, pungent smell, very strong oxidizing agent, strong oxidizing agent. It reacts with most of the metals except the noble metals, except the noble metals. This reaction is very important for this. You see the two reactions I am writing it down. Copper reacts with HNO3. It gives three molecules of CuNO3 whole twice plus will get nitric oxide plus will get H2O. Another reaction is when this copper reacts with HNO3, it gives again CuNO3 whole twice plus NO2 plus H2O. This is the product we get. Two different oxides we are getting. One is nitric oxide and other one is nitrogen dioxide. Now, why these reactions are important? Because we get nitric oxide when the acid is diluted, okay? Nitrogen dioxide will get where it is concentrated. This question they have asked many times in the exam. Even this particular reaction, they have asked in need exam directly. You must know what is the product we get with concentrated acid and dilute acid. Similarly, one more reaction we have, I will write down here. This is also very important. Zinc reacts with HNO3. It gives four ZNNO3 whole twice plus H2O plus N2O. Another reaction is ZN plus four HNO3. It gives ZNNO3 whole twice plus H2O plus two NO2. Here we are getting dinitrogen oxide. Here we are getting nitrogen dioxide. This is possible when this acid is diluted and this acid is concentrated. You must remember this reaction with dilute acid what gas you are getting and with concentrated what gas you are getting. Important thing is this only. I will give you options with this oxides only. Nitrogen oxides. Next point, note you write down. Metals like chromium and aluminium. Metals like chromium and aluminium. Forms chromium and aluminium. Forms a passive film or layer of oxide. Passive film or layer of oxides. Hence does not dissolve in concentrated HNO3. This is also important. Does not dissolve in concentrated HNO3. Concentrated HNO3 also oxidizes some of the nonmetals like carbon phosphorous sulphur iodine. Some of the nonmetals like carbon phosphorous sulphur iodine. C plus HNO3 concentrated. It gives carbonic acid H2CO3 plus nitrogen dioxide plus water. This is carbonic acid. When phosphorous reacts with concentrated HNO3, this gives S3PO4 plus nitrogen dioxide plus H2O. This is the two reactions we must remember. What is the structure of HNO3? The last point for today. The structure of HNO3. HNO3, the structure is N double bond O, single bond O and OH. This is the structure we have. N double bond O, O and H. This hydrogen is the acidic hydrogen. Yes, acidic hydrogen. Since only one acidic hydrogen we have, this is monobasic acid. This is a monobasic acid. It can release only one H plus into the solution. It is a planar molecule. It is a planar molecule. This bond is a coordinate bond. You must remember one thing. For the elements belongs to the second period. The coordinate bond can be represented by this, a single bond or an arrow like this. Both are same thing. But for third period element, like we have discussed in phosphorous oxides, for the elements of third period, the coordinate bond is defined by either a double bond or an arrow like this. This is a coordinate bond we have. N coordinate bond with O. That is why we do not have any lone pair on this network. This is the structure of HNO3. We have done this. Few things are left in this chapter. That is phosphorous. Some compounds of phosphorous. Then we will finish this. We will do it next class. We will wind up the class here. We will let you know regarding the next class whenever we have. Is there one doubt? Not sure. There is a second. Hello. There is a lone pair in oxygen. You can draw the resonating structure here. This oxygen we have here, lone pair. You can draw the resonating structure. That is not a thing. Any doubt? Tell me. You had said that for nitrous oxide, it can be contaminated by NONH3 and H2O vapors. To remove ammonia and water vapor, what do we use? Ammonia and water vapor, if you have any acidic compound you can use. Like the molecule which can produce H+. You can use that to remove ammonia and water vapor. Got it. Anything is there? We will wind up the class. For these chapters, I am telling you, NCRT, you must read line by line. Don't leave NCRT for problem solving. You can refer to any of the books. NCRT, each and every line you should know. We will wind up the class here. Take care. Thank you. Thank you, sir.