 Hi everyone. This is Pratik from Centrum Academy. We will be looking at a problem today which has been a question in our previous year's paper. This question is from carbonates compounds and the question is for two marks. I have just picked up how this question would generally look like in your question paper had you been writing this paper. So these papers are generally printed in Hindi and English both and therefore I have taken out both the versions of the question. So let's read this question. It says a compound X on heating with excess concentrated sulphuric acid at 443 Kelvin gives an unsaturated compound Y. X also reacts with sodium metal to evolve a curlerless gas Z. Identify XYZ, write the equation of the chemical reaction of formation of Y and also write the role of sulphuric acid in the reaction. So whenever you read such a question a very good idea is to actually write what is given to us. So you simply mention the given parts. So you say X on excess concentrated sulphuric acid. So X in presence of concentrated sulphuric acid at 443 Kelvin. So I am also going to mention the temperature here 443 Kelvin actually ends up giving out an unsaturated compound Y. So Y and I can make a small note below. I can say this is as unsaturated. Good. Now as soon as we know this the second thing that it also mentions is that X also reacts with sodium metal to evolve a curlerless gas. So X plus sodium metal gives a curlerless gas Z. Now Z is curlerless so there are multiple options that we can think about right. So one of the first things the first clues that we can actually understand is form concentrated sulphuric acid. If you know from our syllabus concentrated sulphuric acid is one such chemical which actually does dehydration to alcohols. So therefore our X has to be an alcohol and Y has to be some sort of an alkene. So I am going to mention that with the yellow color for you to write. So this is the rough that we actually would do. Now if X is an alcohol let's check if the second reaction works out. Does an alcohol with a sodium metal give some curlerless gas and we know that yes it does give and this would be a hydrogen gas released. So one thing we are very sure that yes hydrogen gas can suit the answer. Now which alcohol it is and which alkene it is this can be according to you know our own assumptions or something that we can actually work out on. Now if you have to write this answer once we have understood this rough work what we will actually do is basically begin writing the answer saying that yes we have identified A X to be an alcohol. So you mention it in words and you also it's a good idea to choose one alcohol. Ideally we will choose the lowest of the alcohols and therefore we will call this as ethanol. If you have written ethanol, ethyl alcohol instead of ethanol that also works. So you should clearly mention ethyl alcohol and write its chemical formula as C2H5OH. So X is identified the second thing that you actually it's a good idea to mention is the B part where you write this as Y and you say that this is an alkene. Now if you have taken up alcohol please note that the alkene that you should write should be a corresponding alkene and therefore the only option that you have is C2H4. And you should definitely write its name and this is actually an ethene. So you can mention the chemical formula in ethene as part C. Now you have to identify Z and we know that Z is actually hydrogen gas. So you can mention Z as hydrogen gas and you can write its formula also as H2. Now once we have written all this entire answer please note that they have also mentioned write the equation of the chemical reaction of formation of Y. So it is very important to write this equation so we will write this as C2H5OH in presence of concentrated H2SO4 and at 443 Kelvin actually ends up giving C2H4 plus water. So please note that I have clearly mentioned water here it's important to write both the compounds together. And now the last question that they have mentioned is to write the role of sulfuric acid. So we will write sulfuric acid is a dehydrating agent here works as a dehydrating agent. Now please note that once this entire answer is written I am also going to share how the marking scheme is there for this particular question. The first three parts are in together total as one mark. So essentially if we are able to write anything that is about sorry give me a second. So if you are writing any two of these parts you will realize that we should be writing about one mark on that. Now let's look at the second part of this which is C2H5OH. Now in this portion you will realize that the first part is actually given a half a mark and the second part is given half a mark. So out of these three if you are able to identify any two of them you should be able to get one mark here and you should be able to get half a mark here and half a mark here. And this is the model answer that you should write for a two marker question. Thank you so much signing off. We will be looking at some more questions in the following videos. Thanks a lot.