 One more question to write down. One mole of an ideal gas is allowed to expand. One mole of an ideal gas is allowed to expand reversibly and adiabatically. Write down the question. One mole of an ideal gas is allowed to expand reversibly and adiabatically from a temperature of 27 degrees Celsius. Adiabaticity. From a temperature of 27 degrees Celsius, if the work done by the gas in the process is 3 kJ, if the work done by the gas in the process is 3 kJ, what is the final temperature? CV is given. 20 kJ, CV value is this. One mole of an ideal gas is allowed to expand reversibly and adiabatically from a temperature of 27 degrees Celsius. If the work done by the gas in the process is 3 kJ, final temperature is what? CV value is given, 450 is one of the option we have. What is CV? Yeah, it's 450. 450 is the answer given in CV. It's 150 answer, 450 is the answer given in CV. The answer is 150 Kelvin, check your calculation. Yeah, it's 150. Yeah, it's 150. It's 150. The question is what? The question is final temperature. The final temperature is equal to final temperature. What are you getting? 177. 177. What? The options are 150, 150, 400. One mole of an ideal gas is allowed to expand reversibly and adiabatically from a temperature of 27 degrees Celsius. Over and you have to go to the next table. Okay, then. What we need to use NCB data? Okay, next slide down. Second law of fruit is, right? So before going into the statement of this law, first two, three things we need to understand. Right? Sir, what happened in the first law? What do you expect more? What do you expect more? Sir, there is no actual statement to it. What did you do in the last class? Sir, what do you expect more? Sir, what do you expect more? Sir, what does this mean? Sir, they have a proper statement. Sir, they have a proper statement. Sir, they have a proper statement. Sir, they have a proper statement. Sir, I see you. First of all, I want you to understand this second law of thermodynamics, One thing we have to understand here, that is spontaneous and non-spontaneous process. What is this spontaneous process? Which does not require any extra movement. What are you going to do? On its own. On its own. What is this process if I take you to the roof and push to come down? What is this process? Spontaneous. Spontaneous. It's spontaneous, its process is, like you said it's correct. It is a process which takes place on its own. Far after proper initiation. Initiate and then leave. That process will be done. Right? So diesel petrol if you burn it, then it will be done by itself. So that is also spontaneous. One process where you have now. Spontaneous. It's non-fire. Yeah, so that's what it is. Either it takes place on its own or after proper initiation. Initiate and then leave. If it is happening, it is spontaneous. Diesel, diesel it is spontaneous. That's what it is. Yeah. I was taken on fire and spontaneous. No, no, no. I said the process is when the fuel catches fire. Right? So that requires initiation. No, no, no. No, no, no. No, no, no. No, no, no. No, no, no. No, no, no. No, no, no. No, no, no. No, no, no. No, no, no. No, no, no. Yeah, right. No, no, no. No, no, no. No, no, no. Yes, yes. Okay, guys. See, first of all, for any process, try to understand this. For any process to take place, there are two criteria we have. Okay? One is don't write now. One is energy criteria. And other one is for a randomness. Energy and area of randomness. Any process, if it is going from high energy to low energy state, that is spontaneous process because low energy state is what? Stable state. Right? Energy criteria means what? Any exothermic process. We can understand exothermic process is an energy raising process and we are going from high to low energy state so it is possible. Right? But we also know there is also endothermic process possible. Right? So endothermic process also takes place. Right? But in this process, we are going from low to high energy state. Right? But still since it is taking place, so there are other factors also which because of that factor only this process is taking place. So what is that factor? Okay? So for example, you see if water, H2O liquid, when you heat this, it converts into a vapor phase, right? H2O gas. Right? So here we have more energy, less energy, but this process takes place. Right? So what is the factor for this that we need to understand? Exothermic process is what? Suppose we have what example we can take exothermic energy releases, right? H2O, vapor. So CO plus H2O, CO is minus. So that is exothermic. No, that is endothermic. Combustion of hydrocarbons, exothermic process, energy comes up. Combustion of hydrocarbons, many examples are there. Combustion of hydrocarbons, energy comes out into this. Okay? Exothermic process. So exothermic process, fine. Endothermic process we have here. Like I said, here we have more energy and here we have less energy. But since the process is taking place, obviously we have some other factor because of that this process is taking place and that factor is nothing but the randomness. The randomness of any system we define by a thermodynamic term we call it as entropy. Don't write this now. Just let me explain this what we are going to do. Right? So entropy. So now we have two factors for a reaction to take place of process take place. One is energy factor and another one is entropy. So energy we call it as enthalpy, delta H. And entropy is S, delta H. So for any process if you have to understand whether the process is taking place or not you have to consider these two factors. Entropy and entropy, right? In reactions also, right? In reactions also. Now actually if the process is I will come back to this point. Is spontaneous process takes place on its own or of a proper initiation? No, it is not like non-expertimist process does not take place. Condition for any process of take place whether it is spontaneous or not. I am just trying to make you understand what factor we need to consider to understand the physicality of any process. So we have two factors in helping at randomness. That is improper here. So when we have these two thermodynamic terms so you have to consider these two factors to understand about the process. So what we did in here, we combined these two factors with the help of temperature and we have given a new thermodynamic term which formula is this and this we call it as Gibbs free energy. You try to understand the significance of this. Why we require this Gibbs free energy? If this delta G is not there then you have to consider two factors delta H and delta S. So what we did, we combined these two factors and we have given a new thermodynamic term. And with this thermodynamic term we can understand whether the process is spontaneous, physical or not. That is the significance of Gibbs free energy. Because entropy depends upon double, we will discuss that later. This is the whole thing which we need to understand about here. Another process is spontaneous and non-inspontaneous process. So spontaneous process are those process which takes place on its own or after a proper initiation. So this is the unit for delta S. Delta S is joule per mole per degree or calories. It is energy, see first of all. What is this unit of this? Energy. Energy. What is this? Energy. This should also be energy. Right. So this is equals to energy per Kelvin is delta S. Yeah. Take it. Okay. So a spontaneous process are those process which takes place on its own or after a proper initiation. For example, flow of water down the hill. Right. Non-inspontaneous process are those process for which we need to put some extra effort into it. And continuously it does not mean that non-inspontaneous process does not take place. Okay. It takes place by some external source, external energy. You stop that energy, the process won't take place. When you switch on the motor in the household, the water goes into the tank, into the roof. Right. Through the pipe. If you switch off the motor, the water does not flow into the pipe. Right. Because we are going from low energy to high energy. Right. Low potential to high potential. For that you need to give some energy into it. Right. So this process is what? This is non-inspontaneous process. You should switch off the motor, the water does not flow. Right. But when the water comes down the hill, it's high to low. Easily it can come out. Right. So that's why it is an spontaneous process. So first of all you just keep this in mind that non-inspontaneous process does not mean that the process does not take place. It takes place when you supply energy into it. So both process possible. One requires continuous energy, supply of energy. And one, it takes place on its own or after a proper initiation. Correct. Right. So for any process we have two factors like I discussed. Energy and randomness. Energy means enthalpy, randomness means entropy. These two conditions, we are combining these two conditions, these two thermodynamic term and we have given a new thermodynamic term that is Gibbs free energy. And on the basis of this only we will define whether the given reaction is feasible or not. And the condition for that is what delta G less than 0. Right. Delta G is equals to 0, the system is at equilibrium. So why and how we get that condition delta G less than 0 that also we will discuss. Right. So first of all you write down this term spontaneous process. Spontaneous process. Spontaneous process. Write down. There's a process which has a natural tendency. Process which has a natural tendency to occur by its own. To occur by its own. Or after a proper initiation under a given set of conditions. Example you write down. Flow of electricity. Flow of water down the hill. All these are, all these process does not require any initiation. Right. Burning of fuels. Carbon. Requires initiation. Burning of fuels or carbon. Requires initiation. Right. That is also spontaneous but it requires initiation. Okay. Write down this line. Spontaneity means, Spontaneity means feasibility of a process. But Potential difference. Even like the flow of water. Even also the heat flows in because of difference in temperature. That is also spontaneous. Two objects at different temperature well comes into contact. Heat. Transportation. That is also spontaneous. But there's a continuous energy. Even the flow of water. There's continuous gravitational energy. So, So, So, So, So, So, So, So, So, So, So, So, So, So, So, So, So, So, So, So, So, So, So, So, So, So, So, And where are we Okay. Distinct. Another thing, So, So, So, So, so, So, heat flows from high temperature to low temperature that is spontaneous current electricity flows from high potential to low potential that is also spontaneous. So, whenever you have potential difference flow of current will be there potential difference is 0 there is no current no flow still gravity is there. So, gravity we are not considering in that way so, all the process becomes on its context is not taking place right. So, that is not we are considering. So, example what did you write all these three examples we have carbon and fuel burning is also spontaneous, but requires initiation next point you write down spontaneity means the feasibility of a process and the process can be very slow or extremely fast resting of iron is also an spontaneous process very slow right one note you write down all natural process are spontaneous and irreversible in nature irreversible in nature next point non spontaneous process write down it is a process it is a process which does not occur on its own which does not occur on its own or or by any initiation example flow of heat from cold to hot body diffusion of gas from low pressure to high pressure diffusion of gas from low pressure to high pressure one note you write down flow of heat from cold to hot body cold to hot air spontaneity is not taking place it is hot to go to school is hot to go to school Can you say that any any any reaction is non-sporters no it is a different it is non-sporter this one yes see water when you boil it converts into vapor right so boiling is a non-inspontaneous process but evaporation is an inspontaneous process in that also the water is converting into vapor water both the process one is spontaneous other one is non-inspontaneous boiling is non-inspontaneous evaporation is spontaneous we are getting vapor only driving force here it is what in in both the process driving force is entropy because of entropy only the process is taking place because gaseous particles has more entropy than liquid particles it has more random motion now when you see if you have two gases one at high energy other low energy so high energy more randomness will be there so that gaseous particles will have high entropy right so both process evaporation and boiling evaporation is spontaneous boiling is non-inspontaneous continuously we have to provide the heat okay non-inspontaneous but in both the process we are getting vapor the driving force is still same and that is entropy not energy right that's why we have two conditions two factors for any process to take place one is enthalpy other one is entropy to understand the process is feasible or not you need to consider these two factors and later on to you know reduce our effort to combine these two factors and we have given a new term that is history energy okay so right now next one note you write down it is not always true that non-inspontaneous process it is not always true that non-spontaneous process does not occur at all non-inspontaneous process does not occur at all it may take place when when the energy supplied from any external source from any external source okay