Know this before your Chemistry Exam

[00:00:01]Okay, guys. We have 2021 paper two. We are still looking at organic chemistry.

[00:00:08]Okay? So, the question uh B8, this is internal 2022.

[00:00:15]And the question reads, this the the structures below show the structures shown below are members members of one of the homologous series in organic chemistry. Okay? So, they all belong to one one family.

[00:00:34]Okay?

[00:00:35]What's the first question is saying, "Give the general formula for this homologous series." The general formula for all of these Now, how can you know the general formula? Listen.

[00:00:48]These are not hydrocarbons because they contain oxygen. There's oxygen. There's oxygen here.

[00:00:54]And you can't see a double bond here um a carboxyl group. We can't see a double bond. We have We can see a hydroxyl group OH OH OH. So, these are alkanols or alcohols.

[00:01:14]Okay? And the general formula for for all alcohols is C N H 2N + 1.

[00:01:26]Okay? Then OH, which is the hydroxyl group. So, This is the general formula for all uh alcohols.

[00:01:40]Question B, "What is the functional group for the homologous series for the for the homologous series?" Ah, it's simple.

[00:01:55]So, the functional is called high hydroxyl [clears throat] group.

[00:02:04]Okay?

[00:02:05]Hydroxyl group, which is like this.

[00:02:10]This one, OH, is called hydroxyl group.

[00:02:14]Uh C S S is used as a fuel because it burns in oxygen.

[00:02:24]Wow. Write a balanced chemical equation for this reaction. So, this is the complete combustion. And if you look at this, this is ethanol, guys. This is ethanol. It's C2H 1 2 3 4 5, then O what? OH. This is ethanol. So, like in the previous video, we answered the complete combustion of this. So, ethanol, we are asked to write the balanced chemical equation, which is C2 H5 OH O oxygen combustion Remember? So, the complete combustion, what we will produce here is carbon dioxide and water.

[00:03:12]Carbon dioxide and water. And balancing this equation, we have two atoms of carbon this side. This side we have one.

[00:03:20]So, we're going to write a two here. So, I'm a I'll use a different color.

[00:03:33]Write a two here so that the carbon atoms balance.

[00:03:37]Um Hydrogen we have six. Hydrogen we have three here. Oh, we have two, sorry. So, put a three so that also hydrogen atoms balances. The other one is um After hydrogen, there's oxygen. Oxygen here I have six and oxygen here 2 * 2 4 plus this three, seven.

[00:04:00]So, how can we make this seven by introducing a three here because 3 * 2 is 6 + 1 7. So, this is the answer.

[00:04:08]Wow.

[00:04:10]The last question on question B eight which is D, they're saying "Which of the compounds are S or T would have the highest boiling point?"

[00:04:28]This question they usually ask. So, the answer is T.

[00:04:35]Okay? So, D So, compound D compound T. If the question was if they even said "Give a reason for answer." because question I'll be in compound T has the highest number of carbon atoms. 1 2 3, this is two, this is one. So, compound T has the highest boiling point.

[00:05:01]So, compound T has the highest boiling point.

[00:05:17]Okay?