Chemistry Paper 2: ALCOHOLIC FERMENTATION & ORGANIC CHEMISTRY Exam Questions and Solutions

[00:00:00]In the previous video, the previous video, we answered question B9 under organic [clears throat] chemistry. And it so it was about the processes that are involved when ethanol is oxidized, ethanol is when you remove water from ethanol, which is dehydration, when ethanol undergoes complete combustion. So, I mentioned that the only process that was missing was fermentation.

[00:00:26]>> [sighs] >> Okay.

[00:00:28]>> [clears throat] >> Now, here is the question under fermentation.

[00:00:34]Ethanol is a product of many fermentation reactions.

[00:00:38]The molecular formula of ethanol is C2H5OH.

[00:00:43]Okay?

[00:00:45]Draw First question which is question A, draw the displayed molecular structure of ethanol.

[00:00:53]The molecular structure is this one is the formula, molecular formula C2, H5, OH of ethanol.

[00:01:03]The structural formula, you always start with the carbon atoms, which you and if it's a single, C to C.

[00:01:10]Then, this side, you add this hydroxyl.

[00:01:17]OH is not hydroxide here, it is called hydroxyl group. This is the functional group for um all alcohol, all alkanols or alcohols. So, we have hydrogen here, hydrogen here, hydrogen here, hydrogen here, and hydrogen here. So, they completely surround the the number of carbon atoms. So, we have 1 2 6. Six numbers of hydrogen uh atoms.

[00:01:54]So, this one is not a hydrocarbon because there is oxygen.

[00:02:00]Okay?

[00:02:02]Let's go to B.

[00:02:05]So question B is saying When ethanol is heated with potassium dichromate five, it is converted to ethanoic acid. Yeah, true.

[00:02:20]So listen.

[00:02:24]Ethanol undergoes oxidation.

[00:02:28]The first one oxidation, you form ethanoic acid. And also when it is when you use potassium dichromate six, not seven, six.

[00:02:41]Um it you will form also form ethanoic acid. So what they're saying is what type of reaction is this? Oh-oh. This is a oxidation reaction.

[00:02:56]Okay? Oxidation reaction.

[00:03:00]Number two, B2.

[00:03:05]Give one safety rule to be observed when handling ethanoic key acid.

[00:03:12]Give one safe um rule when handling ethanoic acid in the in the lab.

[00:03:22]So one of the safety rules is that wear appropriate appropriate safety gear.

[00:03:41]Okay? So So wear appropriate safety gear such as gloves, goggles, all right, and other and others. So wear appropriate safety safety gear.

[00:03:54]That is the the safety the safety rule that you can observe when handling with ethanoic acid in the lab.

[00:04:04]Okay?

[00:04:05]Question C.

[00:04:07]So, question C is saying ethanoic acid reacts with ethanol in the presence of a catalyst in the presence of a catalyst to produce a new substance a new substance. Give the name of Give the name and deduce the formula of the new substance.

[00:04:28]Guys, when if this ethanol reacts with ethanoic acid, the product >> [snorts] >> will be an ester and the reaction is called esterification reaction.

[00:04:42]Okay? Esterification reaction. So, the product will be since you have ethanol ethanol and um ethanoic acid ethanoic acid Okay. So, the name of an ester ester. So, since this reaction is called esterification when ethanol when an alcohol react with a carboxylic acid is called esterification.

[00:05:21]So, the name of the compound that will be formed starts with the name of the alcohol. So, it will be ethyl ethyl then this one ether ethyl um ethyl ether ethanoate So, they end with C um no it. The The The The the the esters. So, it will be ethyl ethanoate. Why? Ethyl from an alcohol, then the last party from a carboxylic acid. So, if we use we use um methyl methanol, it will be methyl ethanoate. If you use propanol, propyl propano- ethanoate. Okay? It's simple as that.

[00:06:16]Now, what is the chemical formula? What is the formula formed for ethyl ethanoate? Okay?

[00:06:24]Ethyl ethanoate, water is removed during this reaction. So, So, the formula that will be formed for ethyl ethanoate is since ethanol is C2 H5 OH.

[00:06:45]Then for this um ethanoic acid is CH3 CH3 COO H. Okay? CH3COOH.

[00:07:01]Then water is formed.

[00:07:05]Water is removed. So, carboxylic acid remove loses the OH and this one the H.

[00:07:13]So, when combining, let me just mention this so that it helps you in the exam.

[00:07:19]Just remove the hydroxyl group here and from here just remove the H to form water. So, when this and this one react, what will be formed is we will form water. And just join what is remaining. Let's start with the acid which is C H3 COO C2 H5.

[00:07:47]So, this one is for carboxylic acid, and this one is for um is for the alcohol. So, this is the formula, which is further simplified as How many carbon atoms do you have here?

[00:08:03]When you look nicely, you have 1 2 3 4.

[00:08:08]Since you have two here, 2 3 4. So, the formula for ethyl ethanoate can be C4 How many hydrogen atoms? You have three 3 + 5 8. So, it can be C4H8 O, how many oxygen? Two.

[00:08:28]So, C4 C4H8O2 as the simplified formula for ethyl ethanoate.

[00:08:36]Okay?

[00:08:38]So, this is the name, and this is the formula, or this one.

[00:08:45]Simple.

[00:08:47]Um Next question is Compare Compare the rate of reaction of ethanol uh What is this?

[00:09:13]Ethanoic acid Yeah, okay. Ethanoic acid is a weak acid.

[00:09:18]It can react with a metal such as sodium and magnesium.

[00:09:23]So, you have acid, which is ethanoic acid. So, an acid and a a metal.

[00:09:32]That's the key. The products are a salt.

[00:09:38]a salt and hydrogen gas.

[00:09:44]A salt and hydrogen gas. Now, what are they asking? They're saying compare the rate of reaction of ethanol with sodium and with magnesium. So, what you can say is uh since this is question what?

[00:10:01]D one.

[00:10:04]So, with sodium mm ethanol will react vigorously with the water.

[00:10:31]Okay? Vigorously with water while or than than with the um that is this is potassium magnesium than with magnesium.

[00:11:05]Okay?

[00:11:06]>> [clears throat] >> So, this is very simple. The reason The The reason is like this uh is is is [clears throat] like this.

[00:11:14]Magnesium Oh, ethanol will react vigorously with um not with water, sorry.

[00:11:25]With sodium.

[00:11:31]With producing producing hydrogen gas here and the salt than with magnesium. The reason is very simple.

[00:11:42]The reason is sodium is more reactive than magnesium.

[00:11:47]If you place them in the reactivity reactivity series of metal, sodium is above magnesium. So, the reaction of this acid with sodium will be more vigorously than vigorous than with magnesium. Okay?

[00:12:07]than with magnesium.

[00:12:09]Then um The last second question is um What will be observed when aluminum is added to to ethanoic acid? Give a reason for this observation.

[00:12:28]When aluminum is added to ethanoic acid >> [clears throat] >> So, So, when aluminum is added to ethanoic acid The product The product will be Oh, let me just say Let's just say So, we can say a lot of observations and what will happen.

[00:13:14]But, what we will say, bubbles will be uh bubbles will be observed.

[00:13:30]>> Bubbles of observed as the hydrogen gas is produced.

[00:13:49]Okay? Then the other product will be Since we've used aluminum and um ethanol, it will be it will be aluminum So, the other product will be aluminum We've used ethanoic acid, so it will be ethano- ethanoate.

[00:14:36]Aluminum ethanoate as will be the uh the salt in this case as our salt. Then um the other product will be hydrogen gas.

[00:14:48]Okay?

[00:14:49]Then the other question is the other question is Give one use.

[00:15:03]This is three.

[00:15:06]Give one use of aluminum based on the observation made in in in D. Aluminum ethanoate. So, aluminum ethanoate in the observation here aluminum ethanoate is used um is used in the manufacture of anti >> [cough] >> antiperspirant.

[00:15:38]Okay.

[00:15:40]Antiperspirant.

[00:15:43]Now, antiperspirant, this is a product that is applied to the skin, usually under the armpit arms, to prevent um perspiration. Perspiration, which is sweating or producing a bad odor. So, this is an anti-perspirant.

[00:16:07]So, aluminum is an alloy that is used as more like a deodorant to prevent a bad odor. So, and it is used in the manufacture of anti-perspirant.

[00:16:21]Okay.

[00:16:22]So, it is used in the manufacture of So, you can say it is used in the manufacture of Based on the observation here.

[00:16:39]There are a lot of uses of aluminum, but here they've said use um the usage should be based on the observation we've made.

[00:16:49]Okay. So, it is used in the manufacture of anti- perspirant.

[00:17:01]Okay.

[00:17:06]That's it. Do you have another question?

[00:17:08]No, that's it. So, these are the solutions to question C C3.

[00:17:14]Okay.