for me. What do you remember about first law of thermodynamics? Energy. Okay. Transformation of energy. All right. So, what does it say about transformation of energy? Okay. Can only uh convert from one form to another. What else cannot be created and yes cannot be destroyed. Okay, these are a few important points about first law of thermodynamics. Okay. And then we learn about exothermic and endothermic reaction. So let's put a summary here. Okay. What is exothermic about? All right. release it from where to when? From system to Yes. Okay. Do you remember what is system? The reactants. Okay. Or you think about it as the molecules. Okay. So, what about the surrounding? What are surrounding? Uh everything will run. Okay. The air, the vehicle. Okay. Okay. And if you have a glass rod, the glass rod as well. Right. So I want you to understand that the release of heat is from the system to the surrounding. Okay? So what about endothermic reaction? Absorb heat from surrounding to system. Okay. I take in the heat. The heat will be from the surrounding. I take it in and then I put into the system. Okay. All right. And then we also learn to draw something called uh analy diagram or also known as energy profile diagram. Okay. So let's uh draw the energy profile diagram for both of these. Okay. So in short this will be progress of reaction or you can put as time. Okay. And this will be the energy as the time passes by. Okay. So usually we are going to start with what? Reactants. Okay. So I'll start with reactants from the middle. Okay. I'll start drawing from the middle part. Okay. So what happen in exothermic reaction? Again reactants. What does reactance do? Releases heat to the surrounding. So after the reactants releases the heat, heat will be in the form of energy. Okay. So after the reactance releases the heat, what happen to the energy level? Decrease. So this will be the product. Okay. So likewise in endothermic reaction absorb heat. So after absorbing the heat what happen to the energy level increases. So this will be final product. Okay. And then what do you call this decrease here? Enthalpy change. All right. H stands for enthalpy and the triangle stands for the change. and change of reaction. So what is the symbol for the sign for this enthaly change of reaction? Negative kiloj per mole. So negative is actually because decreasing. Okay. And then what about this part here? Plus positive kilogj per mole. So the plus here is actually because energy is increasing. Okay. So some of you might uh be thinking oh go nobody asked okay but just let you know. Have you seen something like this reactants and then there's a dome and then these are the product. Have you seen something like this? Okay let me redraw this clearly. Some of you said you have not. It looks something like this. Okay it's actually the same thing. This is still energy. This is still the time. Okay. And this will be the reactant. This will be the product. All right. Basically, the difference from the reactant to the product will be your enthalpy change of reaction. Okay. Still the same the difference whether it decreases or increases that will be your enthalpy change of reaction. But what do you call this from the reactant to the highest energy level? Yes. Very good. Some of you still remember. Okay, it is called uh activation energy. All right, you will learn this in chemistry too. Basically, just means that the reactant needs to reach a certain energy level breakthrough. Okay, before it can become a product. All right. So teacher, can I draw it like this? And no problem. Okay, it's the same thing just that because in this chapter we didn't learn about activation energy. So the simplified version like this just showing reactant and product sufficient. Okay. But if you are familiar with this you want to draw the do go ahead it's not wrong. All right. So these are the energy profile everything the energy level the sign we have discussed. Okay. And then we learn about standard enthalpy change of reaction. What does the standard entity change? What are the standard condition? Temperature 25° C. Okay. For this you just understand that we are talking about standard condition for reaction to happen. All right. Standard condition means just imagine scientist doing experiments we conduct it in the lab. So it is the normal condition in the lab. All right. So what are the normal condition in the lab? Temperature 25° pressure 180m. If you have any marity any concentration any liquid solution. Okay. 1 mo per decime cube. Concentration 1 mole per decime cube. Uh if you have carbon, what does your carbon exist as? Graphite. Okay, it's a solid and we normally put it like this a solid graphite. Okay, to show that we don't use diamond for our reaction. Okay. And then to calculate entity change of reaction, you learn one formula. What is the formula that you learn? How to calculate entity change of reaction? MC theta over number of moles. Okay. So I heard some of you said negative MC data over mole. Okay. I would advise you to ignore the sign whether it's negative or positive. Remember what I told you yesterday. All right. Don't need to confuse yourself with any signs in front or behind. Okay? Just calculate what is the temperature change and then look back at the question. If temperature increase, what is the sign? Temperature increase? Temperature increase. Temperature increase negative. All right? Because temperature increase means from low temperature to high temperature it means that I have released the energy to be absorbed. Okay. So if temperature if you measure there is an increase in temperature it's a negative sign. If there's an increase in temperature positive sign. Okay. So don't need to know whether it's negative or positive. Okay. Just look at the temperature change. Okay. Okay. And then we also these are calculations of course. Okay. Anything you want to clarify about yesterday. Okay. Okay. Then we get ready for today's lesson. Okay. Yesterday I introduced you to this. Okay. Remember generally we call all the reactions as entity change of reaction because reaction is a general term. If you do not know what reaction is that you use this symbol R reaction. Okay. But for foundation we are going to specifically learn four types of reactions. And what do they mean? All right. The first one that we are going to learn is atomization. So we went through atomization yesterday. Okay. The purpose of learning this what is the standard standard entropy change of combustion. Sorry. The purpose of learning what are the standard enthalpy changes for this four are because we know that enthalpy changes has a unit kilog per mole. All right. So when we go in deep into these four enthalpy changes we need to understand their per mole refers to what per one mole of what happened. Okay, for example, yesterday we went through atomization. So for atomization, where is the per one mole? Where does the one mole comes from? One mole of one atom gaseous atom form or react formed. class. My advice, serious advice to you, please understand this for if you memorize, you don't understand, you cannot write down the equation, you cannot solve the enthalpy changes, you cannot do the calculation. All right? You have to understand. So when I say atomization, what is the one mole? You will have to understand and quickly tell me one mole of gaseous atom formed what and where is the location whether reactant or product. Okay. All right. So of course the name standard okay will always be under standard condition. Okay. So these are the examples we have went through yesterday. Okay. So for atomization emphasizing again kiloj per mole it means that when one mole of gaseous atom is formed. Okay. So when you balance equation you also have to keep them at one. Cannot touch whatever here that is one. That is why you have to understand what does it mean because you cannot balance this part. Okay, you have to keep this as one. So for example, this value positive 715 kiloj per mole. It means that 715 kiloj of energy is absorbed or released. Absorb one. Continue for me. Very good. One mole of gaseous carbon is formed. Excellent. Okay. We also went through why we balance this in this way. Okay. Because we have to make sure that one mole of gaseous atom is formed. So when we balance, we balance it half. And since gaseous gaseous state I must be in atom it involves a lot of breaking of bonds. Okay breaking bonds to the gas breaking bonds to the atoms. So it is always positive value. I need to absorb a lot of energy and the symbol if you talk about atomization the symbol is no longer R it is 80. So when you look at NT you should know that it is atomization. Okay. All right. So we proceed next standard and change formation. All right. So change formation the symbol is F for formation. So what is standard and change of formation per one mole of compound form. All right. You see you have to know what is the one mole whether it is reacted or formed. All right. So this is per one mole of compound form. Okay let me show you how the equations are achieved because you will need to write the equations on your own later. Okay. For example I have H2O. Okay. And dumping formation means when I form one mole of this compound. So this one mole cannot touch. when I balance. Okay. So, H2O, what is the state symbol for H2O? Agreed? Okay. Next question is ask yourself from the periodic table, what are the elements? The elements individual elements that form water. Oh, individual elements. Next question. Ask yourself under standard condition what does hydrogen exist as what else? H2 always remember. Okay. Don't take for granted just gas molecule gas. Okay. Okay. What does the oxygen exist as in standard condition? Oh, do yes. Very good. Okay. Balance this. Balance this. What? You already have two hydrogen. Balance this. Students. This is chapter one. Like I say, if you learn chapter five, you cannot forget chapter one. Balances. O2. Okay. Can I touch H2O? No. Okay. That is why you have to understand what are they when formation my one is at the compound form. So I cannot touch the one here. Okay. All right. We try to understand this C6 H6 benzene. Okay. So it's in liquid again enthalpy formation means I'm going to form one mole of this compound. So I cannot touch this because this is the definition. Okay. What is the first question you ask yourself? What element? Okay. So what element form please? C H. Next question standard condition what they exist as? So carbon standard condition solid yes must be graphite hydrogen H2 molecule gas balance carbon three hydrogen. Okay. So don't need to memorize the equation because questions will not be only these two. The thing is you understand how we come up with this equation and you know how to write it. Okay. Can I erase this? Okay. Because these are exactly this, right? I'm just showing you what happened. So I erase this. Okay. challenge you equation for standard enthalpy formation of ethano. You know the formula of eano ste. All right. Consider this liquid. Okay. You try first then we discuss. Okay. What are the reactants? C H O. All right. C exist as solid graphite. Must put a solid graphite. Hydrogen molecule gas. Oxygen molecule gas. Okay. Balance. Two carbon, three hydrogen, half oxygen. Very good. All right. So this is what it meant to understand the definition and not to memorize because like I keep on reminding you I will not ask you definition I don't ask you to write down what is the definition but I will ask you to write the equation so you have to know okay all right so enthalpy formation can either be positive or it can also be negative all right the symbol is formation so later we will go into detail next week. Okay. Hassa's law. How to use Hass law to calculate standard and boundary changes. Okay. But before that allow me to move back a few slides. Okay. I I forgot what is this slide number. Can you check for me what SL number is this? Yesterday we learned this and I say we will come back to this. Somebody check your slide. What number is this? 10. Okay. Slide number 10. Okay. Because only after you have learned entropy formation that I can bring this to you. Okay. So yesterday you learned how to calculate enthalpy change of reaction. Remember what is the formula that you use to calculate enthalpy change of reaction? MC theta over N. Okay. So it will give you kiloj per mole. This is the first method. The second method to calculate enthalpy change of reaction is you can use the enthalpy change formation. Okay. It means that sum of enthalpy formation of the product minus sum of enthalpy formation of reactant. For example, if you have A + B produce C plus D, you have this equation. If you want to calculate enthalpy change of the reaction, this whole reaction, you use what is the enthalpy formation of C plus the enthalpy formation of D product. This will be the product. Okay? minus enthalpy formation of A plus enthalpy formation of B this will be reactants okay so that's why product minus reactant but the rule to use this formula is you must have the value of enthalpy formation only formation if you have all the enthalpy formation for your reactants and products then you can use this equation to solve. Okay, just ask you if let's say I have enthalpy formation of A, enthalpy atomization of B, enthalpy formation of C, enthalpy formation of D. Can I use this? Yes, cannot. 10. All right. So this is the second way to calculate enthalpy of reaction which is if you are given all the enthalpy formation. All right. Give you one minute to digest then we move on to the next enthalpy change. Right. I'll move back to this. Okay. So the third and change is neutralization. What do you understand about neutralization? Huh? acid plus uh base produce salt plus water. Okay. What is the common common item common compound in all neutralization? Water common. Okay. All your neutralization must have water as the product. Therefore, your entropy change of neutralization will use when one mole of water is formed. Okay? Not one mole of acid, not one mole of base, not one mole of salt, but one mole of water being formed. Okay? So, when you balance the equation, your water must have one mole. So your kiloj per mole refers to the energy that you release when one mole of water is bought. Okay. So enthropic change is always negative because you are forming new bonds in water. You are breaking all your acid and base and forming water. So the symbol is enthalpy change neu neutralization. Okay. All right. So let's try a few questions. Uh maybe you can try first. I think these are just using back the formula that we discussed yesterday. Can you try question six and seven while I check the attendance then coming back out assist whichever you cannot. Where's attendance? Have I6 who hasn't signed? Eight. Eight. Still seven. Please help me. I think the time Seven. Anyone has been signed? Six. [Music] Not here. Okay. How many are done with question six? Seven. Okay, then give you more time. But don't take forever. You take forever. We cannot finish the cyl. This question requires your knowledge in chapter one. All right? So if you struggle, it means that you have forgotten your chapter one. Right? So this is a very good exercise as well. All right. Can I see how many have done? Okay. Is it okay if we discuss? All right. Okay. So whenever again now we are back to sort of like stoometry do you remember what are stoometry what what is it uh you have a balance equation and then you have to calculate this part what is the ratio of number of moles and you compare and then you solve okay so that's trigonometry okay so now I tell you that I have hydrochloric acid uh Sorry, excuse me. What's your name? What's your name? Sorry. Oh, okay. Okay. So, here I have hydrochloric acid reacting with NOH. They are being mixed. Temperature of the solution increases by 0.68. Okay. So whenever you need to solve a stochometry first thing that you have to come up with is balance equation must have. If you don't have balance equation you don't know how many moles react with how many moles produce how many moles you will not be able to solve them smoothly. Okay. Okay. And then calculate the entity change of the reaction in kilogj per mole. Okay. So what kind of reaction is this? Neutralization. Okay. So I hope you do understand how you come up with the equation but I'm going to show just a little bit. Okay. So the H from SC will add with O from your base and they will produce H2O. All right. So the remaining will be and they will form your salt N. Okay. Okay. And then you try to balance this. Is it balanced? Okay. Okay. Once it is balanced, then only you can continue to solve. Okay. So here I have marity, I have volume, I have marity, I have volume. So what is the first thing that I have to do? Number of moles. Okay. So how do you calcate number of moles from marity and volume? Okay. And then directly times then divide by 1,000. Why you have to divide by 1,000? Yes. To convert cm cube to decime cube. Okay. We are not in chapter one. So I won't go step by step. Just a bit of revision. Okay. So what do you get for this? 0 5.0 * 10 negative three or four. Okay. And then same for this number will be the same and then you will get of course the same answer. Is it? Check for me. Okay. Okay. And then look at the question. The question is asking you to calculate enthalpy change of the reaction in kilogj the mole. So what is the formula to calculate enthalpy change of reaction? Yes. Okay. So we are going to use entity change of reaction is MC theta over number of mole. Okay. So revision again. MC theta is MC theta of one surrounding and surrounding is most of the time it will be one number of mole is this specifically what number of mole should I take acid base salt water only one person got it correct water y divided by water. Yes, this is neutralization. We just learned what is enthaly change of neutralization per one mole of water. So this part will give you kilogj this part will give you mole. So your mole must follow the definition per mole of water. If you are lucky number of moles are the same like this equation. This is the first question definitely is very straightforward. Number of mole is the same. Okay. But if you're unlucky number of moles are different. You have to know that it is supposed to be per mole of water specifically because it is neutralization. Okay. Okay. And then let me continue to solve. What is the mass of water that you are using mass of water? How much? Why 100? Sorry. Okay. Because you have to imagine the reaction. Okay. You have HDL 50 cm cube. You are going to add it and AOH also 50 cm cube. So how much of water do you have when you measure the temperature? 100 50 + 50 100. Okay. It requires your imagination. You are measuring the whole solution. So the whole solution contains 100. Okay. But as I say yesterday, I hope you still remember, I will use kilogram because I want the final answer in kilogj C 4.18 data 01.68 and number 5 * 10 -3. Okay. Because one to one to one. So 55 5 same. Okay. Complete for me. 56. Okay. 848 kilogj per mole. What's missing? Why is it negative? Yes. Check back. Temperature increases. So it's exotic. Temperature of surrounding increases exothermic. Okay. So basically it is like this. I'm measuring the temperature. I have my reactants and product. So reactants my reactants react releases heat captured by the thermometer. That is why temperature eight. Okay. Man know how many have done question seven or also very few. Okay. Maybe I give extra one minute. Okay. After you understand question six, please uh try question seven. Uh may I just ask is the equation given in your slide? No one want you have to come out. Okay. Then I should delete the equation. Check. Okay. So, hydrogen from acid and O from base. So, which one is the acid here? CH3 CO H. Okay. So, this is the acid. I'll take the hydrogen here and I'll take the O here to form my H2O. And then write down what is left. You will have N CH3. Okay. CH3 CO that is how you form the salt is this balance. Yes. Enthalpy change of reaction in specifically it's a neutralization reaction MC theta over number of mole. How much is your M? 0 4 075. Yes. Okay. because only 75 C 4.18 beta 8.3 number of moles 5 * minus 32 three or two some three Okay, luckily before I press. Okay, so what did you get? 52 41 sine still negative because temperature increase. Okay. So just to add up with this you'll get the same number of moles. Okay. So one to one to one ratio. So five to five to five right see okay uh one more slide then I'll give you a break okay to digest everything so first we learn atomization second formation third neutralization and the Last specific enthalpy change will be combustion. What is combustion? Burn burn in oxygen. Okay. So entropy change of combustion. The main character here is one mole of whatever you burn. All right. So this part will be under reactant or product reactant. Okay. The substance is completely burn. It means that whatever you want to react with oxygen is completely burnt. Okay? Meaning to say that now this becomes one mole. Okay? So don't balance this part. All right? You must keep this as one. Combustion is always negative because it produces heat. Okay? A lot of heat is released. So the symbol is combustion. Okay? All right. So if you it's 1:12 we will come back at 1:22. Okay then we will continue. Uh attendance can pass back to me. It's slow. I like it from It's not good. something. Yeah. in this run. What? Oh, singer. Yes. Thank you. S9. Thank you. Because when we talk about the change, we assume that it will need the most. Oh, usually we want to use it usually first. But when you want to form because form means so form when we want to form it to make it the purest but when we want to use it usually you cannot use it so it's water is If reduction if you use it for reduction you will be oh spring I saw you walk just now. What happened? only the floor now can last two days uh Sunday night like I came back then catch Can I please ready? 10 is a co in terms of each element they say yesterday element have the same physical but then each element have like many atom exist but I ask you a question each student has a different student ID. Okay. Make sense. You see? Uh so this question used to trick people. It's not to trade. It is you have to your your English why why this context you can understand but that context you cannot understand. Very confusing. You know you use other words to like represent this. All right. All the words that I use I use in the lecture also. When I say each element, I always use appearing table. Each element I always do. I have to repeat two times. You know, that's why English is poor. I don't blame it on my paper. Okay. All right students, we will start in one. Let's speak. powerful ideally. All right, students get ready. We will start. Okay, get ready. All right. So to calculate okay or to check what is the tenant and theory of combustion okay we use an instrument which is known as a bone calorie meter. Okay if you take physics in your second and third semester you will have the privilege to use this characters the bone calorie meter. Okay. But in practical eight, the last practical of chemistry one, we will use a simpler version, the lab version of a bone calorie meter. Okay? But in physics, you will use the professional version. Okay? So it is known as bone calorie meter. So look at this instrument. All right? So look at this instrument. So here is where I put the sample of what I want to compass, what I want to burn. I'll put it in this cup. Okay. And then there is this ignition wires whereby of course there is a button. So when you press the button the wires will ignite. Ignite means it will start to burn. All right. So after burning you see there is a stirer. What do you think is a function of this stirer? To what? Yeah. Why you want to stir the solution? A even heat distribution to distribute the heat. Okay. And lastly, you will have the thermometer. Okay. That is why we always say that the thermometer measures the temperature of the surrounding. Okay. Because from here you can see that the sample burns. Where will the heat transfer to after I burn my sample? To the surrounding. Okay. So then to the water and then the water is going to stir then only being captured by your thermometer which is your surrounding. Okay. Now can you tell me what will be the weaknesses of this instrument? I want you to analyze. Put on your thinking cup. All right. I'm telling you. Okay. Close your eyes. Imagine this bone calor. It's in a metal steel cup. Okay. It's in a in a metal uh cylinder. You put your sample inside. You can only burn it. Okay. Ignite it with a switch. It starts to burn and then you look at the temperature change. Okay. Okay. So, what will you complain about this instrument? What are the weaknesses? What? Okay. Okay. Heat loss. Where will the heat loss go to? Of course, this is the easiest answer. Whenever you have heat, there will be heat loss. All right. So, where will the heat be lost to? Give me some examples. Huh? Yes. Very good. Container will absorb some heat. Where else? Stir. Yes. Will also absorb heat. What else? Huh? Yes. The wire also absorbs some heat. What else? The cup itself. Okay. Because the first layer is the cup and then after that the air in the cup and then only it will go through this metal uh container another metal container. This is the small one and then it will go through the water will absorb some heat and then the sterile will absorb some heat and then the large container will also absorb some heat. A lot many many layers many many things are able to absorb the heat. So a lot of heat loss. Okay. Anything else you will complain about this? Cannot cannot what? Okay. Very good. cannot observe why you don't need to observe to make sure completely reacted. Okay, so it's a closed container. You will not be able to observe. Okay, you will not be able to know when the reaction has ended. So if let's say this set up without knowing without looking at the sample how can you assume or how can you guess that oh okay already finished I can open it through the change in temperature okay so let's say this is a combustion so how until which level of temperature are you going to stop the reaction it will not go constant Okay. What's going to happen once you start let's say temperature you start from 25° C. Okay. And then once you start the combustion what's going to happen to the temperature increase until under a maximum. And then what's going to happen to the temperature decrease. If you leave it long enough, of course, you know you have boiled water uh before it will use very very very long time for it to go back. Okay. But which level will it go back to? Yes, the lowest it will go is the room temperature. It will go back. Okay. But usually you measure until the highest. Once the temperature starts to drop, it means that it has ended. It is now going back to the room temperature. Okay. So please apply this in practical a okay same thing practical aid you are going to do it in the cup you cannot open the lid once you open the lid all the heat is going to come out all right so you have to look at the temperature change go up go down that means it's ending up anything else okay why do you say incomplete combustion yes okay because it is a Closed lid or closed container. What happen if it is a closed container? Yes. Insufficient oxygen. Okay. So actually all of these the weaknesses as a scientist and somebody who has done experiments before you are able to think of this. Okay. So my bottom line is always don't memorize. You know all of this. No need to memorize. Okay. Okay. So next. Okay. So this will be the bone calorie meter that you are going to use in practical thing. Okay. It uses a simple polyrin cup with a lid and then uh you will put it inside a beaker just to stabilize it. All right. And then you put whatever reactants are needed. You poke a hole. Put in a thermometer. What is the weakness of this? Extra any extra weaknesses? Extra weaknesses uh compared to this. Anything extra that you can add? You didn't capture what I say, right? I already mentioned this. I purposely draw it out. I purposely say anyone can capture not enough all the No about the What is in this setup that is not in this set up? Okay. Yes. Number one, there is no stirer. But do you recommend adding in a glass rod and stir it? Why not? Why heat loss? Explain further. Where will the heat loss? What do you mean loss? Okay. Number one, of course, your ster is going to absorb it. What else? Huh? Okay. It is supposed to be a closed container. So how do you add in a stirer? You have to make another hole. So if you make another hole, what's going to happen? More heat loss. Okay. So that's why not recommended to use ster in practical egg. You will just use your hand to stir. Okay. And this bring us to number two. The difference that I want you to see is that there is extra hole. This one you cannot prevent. You have to put a thermometer there is extra hole. So there will be extra heat loss. Okay. And if let's say okay your compound that you want to burn okay is a liquid in liquid or aquas for example you are burning ethanol aquous or liquid okay so usually they will put it in this container they put something to burn it and use this heat to heat up a beaker of water and then the same thing look at the temperature change from this heating process Yes. All right. Okay. So, the problems with calorie meters we have analyzed together. You guys gave me the answer. Okay. Number one, incomplete combustion. Okay. Because it is a closed container. Okay. And then you can add insufficient oxygen. Number two, there's a lot of heat loss to the surrounding. Okay, we have already discussed where the heat loss goes to. Especially if you have holes, you will have even more heat loss. Okay, and also absorption by everything around it, the cup, the stirer, the metal container on or everything else. Okay, so the third one, incorrect heat capacity. The incorrect heat capacity means that uh like I mentioned just now if you want to calculate 100% of the heat you will need to use the MC theta of water plus MC theta of stirer plus MC everything that absorb the heat. Okay. Okay, just now we have cup and then we have container blah blah blah blah blah. Okay. And of course it is not wrong if you add another one answer saying that you are unable to observe to observe the reaction. Okay. Okay. So I always encourage students okay not things like this that requires your thinking uh not necessarily you must follow 100% of this because it wants you to think. So I want to know what is your answer from things that you analyze. All right. So even like this it's not in this slide but it is acceptable. Okay. All right. We have question 8 9 10 11 and 12. Okay. I'll give you some time to try first and then we will discuss it. 8 9 10 11 12. Okay. We will discuss them together. Okay. Uh I'll try question eight with you first and then you try 9 10 11 12. Okay. So eight is the most direct. So you look at the requirement of the question. I want standard enthalpy combustion. So standard enthalpy combustion. What is the formula that you use? Yes. is still MC data at this moment divided by number of moles. What is the M value? What M value will you use? 0.74 or 200? How many of you say 0.74? How many of you say 200? Okay, majority means I mentioned so many times before. MC data is for water or surrounding. So what is your water or surrounding? Okay. So this 0.74 is for this is the mass of what? System. Where should your system goes through? Down. Okay. Okay. So a lot of students got their answers wrong because they used the wrong value to substitute. They couldn't understand system and surrounding. Okay. So I've emphasized many times top part will most of the time 99.9% of the time be the surrounding water. Okay. So this I will have 0.2 2 again I use kg since it is water specific capacity 4.18 temperature change 8.0 zero. What about number of mole? What is the number of mole of system? Do you need to use the mass and calculate molar mass? No. Why? It's given. Yes. Okay. Be smart. Okay. So, what do you get? Yeah. I am the president 615.8. Okay. So don't forget your unit. Okay. And then symbol sign temperature increase. So minus Okay, you can try question 9 until question 12. Okay, any question about this? Anyone has anything to ask? No, nobody wants to ask teacher uh caling do I need to convert or not? No need. Okay, then I don't need to explain this. Okay. Okay. 9 until 12 you try and we discussing I tunar Dina Jonathan Oral Noel Angelina as Not here. Muhamad Abar Jun Stanley. Click on Lai. How you invest? Elvin Leing Ryan, Cecil, Seline, Sin, Chloe Sling Jing Yong Lin Miras Durali Amina Den Mohamad Howi Chinho the chain. Oh, sorry. You earning jaggy sin. You have seen Yuki William. [Music] Zah Bing. [Music] You miss [Music] Oh, sorry. Josling ninja Jun Jun your lab manual was in B 021 yesterday you talking And linguin Friending [Music] DJs Are you done? How many are done? Okay. Heaven. Hey. Uh, sorry. Discuss. Since when? No more know. Very long ago. Huh? Oh, why you didn't tell me? I didn't Okay, sir. The device is turning. Please wait a moment. She told her Uh, is the TV showing? All right. Sorry. Let's continue. Yeah. already discussed this uh propane gas. Okay. Used for combustion the equation and then target of combustion. Calculate amount of heat energy in kiloj that was produced during the combustion of 300 kg of propane gas. Okay. So what is a formula that you use? Is there any formula that you can use? Can you use MC data? Can you use MC data here? No. Why? You don't have temperature change here. Okay. So, how do you what is the information that you use to solve this question here? The enthalpy change. Okay. I know that enthalpy change of combustion is -2220 kiloj per mole. What does this means? Oh yes. energy 2220 kiloj is released for one mole okay that's why I emphasize the importance of you understanding the unit okay it means that one mole is -2220 kiloj all right so now I want to find how many kilogj do you have the number of moles can you find the number of moles Okay. So from where I have 30 kilogram of propane gas from 30 kilogram can you find number of moles? Yes. Okay. Do you use kilogram? What must you do? Why you must convert to gram? Yes. Very good. Okay. Because your molar mass here is gram per mole. If you want to calculate mole, you have to cancel g and g. All right. So again unit tells you what you need to do whether do you need to convert or you do not need to convert. Okay. So propagating 44.11 680 Double for me please. Thank you. 680.118 mole will produce how much of energy? Okay. So the amount of energy will be 680.118 * by 2.20 two zero. Okay. 150 9861.96 kilogj 1 2 3 1 2 3 Okay. Or if you want to shorten it then it will be 1.51 * 10 uh kilo. Okay. Okay. So next question then calorie meters are calibrated. Oh sorry. In a typical experiment, I have 0.1 cm cube of ethanol completely burned in a calorie meter. Temperature changes from this to this. So, I have a volume 0.1 cm cube. Temperature change 25 to 29°. Hey, how many moles of ethanol has reacted? So, how do you solve this? How many moles of ethanol has reacted? How do you calculate the number of moles? For gain mass over mass, where do you get the mass from? Where do you get the mass from? Huh? The volume. All right. So that's why I put it here. Assume the density of ethanol is the same as density of water. So we learned yesterday that density is 1 g per cm cube. Density of water. Okay. So it gives me 1 g is 1 cm cube. All right. So to calculate number of mole I can assume my cm cube equals to g and then I divided by the mar mass. only 6.08 2.17 and 10 -3 ohm. Okay. Okay. How much heat energy was released during the reaction? All right. So how do you calculate the heat release? Okay, using the enthalpy change. So how change of reaction 1,000 kiloj per mole. So the same thing one mole will release 1,000 kiloj of energy. Okay. Okay. So, how many moles do you have now? 2.17 * n -3 mole. So, how much of energy? 1,00 * 2.17 * n -3. Okay. So, here those of you who can understand 10^ 3. So you will get 2.17 kilo3 right. So how much of heat energy this is the amount of heat energy released. So the negative sign here means released. Okay. And then question 11 enthalpy enthalpy combustion of set is -2059 kiloj per mole when 0.47 g was completely blah blah blah blah blah. Okay. Calculate the amount of heat equals to MC data. Is it what is the m 0.2 2 C8 then 5 22.99 kilogj per mole release so negative okay always check for the key words in order for you to double check your sign. Okay, use the data above and your answers in A to calculate the relative molecular mass of S. Okay, I know that entropy combustion is -2059. Okay, so this 2059 is MC theta over number mole. All right, so what is the value of your MC data? 102.99 I have calculated. So can you calculate number of moles? Okay. So this negative and negative actually cancels off already. So you don't need to write the negative. Okay. Okay. So where's the number of mole 0.12 mole? Okay. from the number of mole. How do you calculate relative molecular mass? I have number of mole. I need to calculate relative molecular mass. What is the extra things you are given? 0.47 mass of set. Okay. So, number of mole is mass 0.47 47 divided by relative molecular mass. So relative molecular mass equals to 112 falling 1.96 any units needed no because I asked for RMM so don't need any units. Okay. Okay. And then there's a question 12. Okay. For question 12. Okay. We are talking about real life application. I want to calculate the energy content of the brain. Okay. I just give you the mass of the brain. Okay. And I tell you the same thing. It raises the temperature of water by how many degrees C? All right. So since I know that entity change of reaction because I want to combust okay I'm combusted and change of combustion I will use MC data over number of moles correct but break can you find number of moles of break? No. Okay. because there's no chemical formula. That is why we replace this with the mass of the food, the brain. Okay. But is it still the same concept? All right. So, what is the mass that you use? Yes. Why? 0.1 mass of water. Think about where you measure the temperature change. Is the temperature change of water? You can always start from the back. Temperature change of water. So specific heat capacity of water. Therefore the mass of water. Okay. Always double check where is your temperature change from. And then divided by the mass of the brake the system that you use. Okay. So you will get 29.6 okay kilogj this will be kilogj right per g oh is it is there any uh which oh I for 1.48 sorry 20.01 zero. Okay. All right. So, for next week's lesson, okay, I'm going to give you a heads up because next week we are going to start with Hass law. How many of you have encounter or had a had a meet Hass law before? How many have of you have used Hass law before? No. Okay. uh Hampton's law is for a lot of students okay it's a bit um hectic okay I wouldn't say that it's difficult okay if you listen to the instructions carefully it is actually very easy the most easy part for you to score mark in final exam is actually has a score but you need to come ready okay you cannot be like this I tell you and then you don't understand what I'm going to say okay so first of all I have already uploaded included in Microsoft Teams. Okay. Have a small question 13 to question 16 template. So you need to have this ready. We are going to answer question 13 to question 16 on this template. I prepare very clearly for you so that you can follow closely. All right. So first you need to get ready with this. Secondly I want you to get ready with the four definitions. Remember the foury changes. What are the four changes? Atomization, formation, neutralization, combustion. Okay, what do I mean by get ready? Get ready means you have to understand there are per one mole is per one mole of water because when we do the questions next week, you will need to come up with the equations. So I want you to understand how the equations are written. Okay. All right. Okay. So these are the preparation for next week and then before you leave uh as promised okay 8 and 9 I will meet you tomorrow and give you back your quiz paper. Yeah. So you can refer to this under quiz I included a comment. All right. So this is how you see it. I have finalized everything the average. So you can see according to your class what is the highest? What is the lowest? What is the average overall for fis1 until fis9 highest lowest average okay I just want to explain this what do I mean by zero stroke 2.5 it means that there is one person who didn't sit for the quiz so got a zero and will not be given a chance to sit for the quiz anymore because a lot of chance has been given so it's a zero But he got a zero because didn't sit for the quiz. But then if I didn't consider this zero, I didn't consider the one who didn't sit for the quiz, then the lowest marks is 2.5. This is how you interpret this. Okay? And then from here you can check look at your quiz marks. So you will know let's say in your class if you got 22 marks it means that you are above average. Okay? and you are above average of everyone else. Okay, don't need to take picture. It is in Microsoft Teams. Okay, don't have this habit of taking pictures everywhere. All right. Hey, uh one last thing. Can I say one more thing?