Let's start another topic of physical chemistry chemical kinetics now kinetics means velocity or speed of speed and chemical means chemical reaction we study here rate of chemical reaction or velocity of chemical reaction now let us understand what is chemical kinetics a branch of chemistry or a branch of physical chemistry which deals with the study of rate of chemical reaction is known as chemical kinetics rate of chemical reaction is known as rate of chemical reaction We call a branch of chemistry as chemical kinetics We study the rate and mechanism of chemical reactions What is chemical kinetics? It is the branch of chemistry Chemistry which deals with the study of study of rate of chemical reaction chemical reaction is known as known as chemical kinetics chemical kinetics islamic chemical kinetics when the chemical reaction is known as chemical kinetics we have to study about rate of chemical reaction on the basis of chemical kinetics point of view certain chemical reactions are classified into three groups we have divided chemical reactions into three groups and we have divided them into three groups on the basis of chemical kinetics point of view chemical reactions are divided into three major types three major types fast reaction, fast reaction, another intermediate reaction, intermediate reaction, and third one is, third one is slow reaction, slow reaction. According to the point of view of chemical kinetics, we have divided chemical reaction into three types Fast reaction, intermediate reaction and slow reaction Now I will describe about these three types of reaction First one is fast reaction 1. Fast reaction What kind of reaction is fast reaction?
The reaction which completes within the fraction of second For example, we call fast reaction as the reaction which completes within the fraction of second For example, we call fast reaction as the reaction which completes within the fraction of second within the fraction of a second is known as fast reaction fast reaction within the fraction of second matter so kitchen money this reaction always a fast reaction money and the example of fast reaction money many explosive reaction neutralization reaction precipitation reactions are the examples of fast reaction example man Many explosive, explosive reaction. Explosive reaction, neutralization reaction, neutralization reaction, precipitation reaction, precipitation reaction. They completed within the fraction of second. You know, the fraction of second completes.
And let's take an example like this. NaOH is a neutralization reaction plus HCl. Let's take it.
reaction karai one a NaCl plus H2O and another precipitation reaction AgNO3 plus NaCl reacts to give AgCl your PPT white PPT plus NaNO3 these are the examples of fast reaction intermediate reaction two number intermediate reaction The next type is intermediate reaction What is intermediate reaction? The reaction which completes within measurable time period which completes in measurable time period If it completes within the time period we can measure then that reaction is intermediate reaction The reaction which completes in measurable time period is known as intermediate reaction. This is an example of intermediate reaction.
Hydrolysis of stir, decomposition of hydrogen peroxide are the example of intermediate reaction. hydrolysis of stir, decomposition of H2O2 hydrogen peroxide are the example of intermediate reaction means if any reaction is completed in a measurable time period, then intermediate reaction is called H2O2 hydrogen peroxide double bond O C2H5 ethyl acetate if we hydrolyze it in presence of acid and if we hydrolyze acidic medium if we hydrolyze ester COOH and C2H5OH alcohol and carbojile convert it into acid This reaction is in miserable time period. So we have to keep it in intermediate.
For example, if we decompose H2O2, it decomposes into H2ONO2. This decomposes in water plus oxygen. This also decomposes in miserable time period.
These are the examples of intermediate reaction. Now we will talk about slow reaction. Another type of chemical reaction is slow reaction.
Part number, slow reaction. How to say slow reaction? The reaction which takes long time to complete It takes a lot of time to complete the reaction Normally we don't see any reaction We don't see any change But after a long time we can see some changes That is slow reaction It takes a long time The reaction which takes long time to complete to complete is known as known as slow reaction an example of slow reaction rusting of rusting of iron slow reaction is the wrapping of food or fruit or aging of human being or aging of animal They all have to be in slow reaction Some of them are in erosion of soil erosion Some of them are in fading of statue or train They all have to be in slow reaction It took a long time to have that reaction These are the types of chemical reaction on the basis of chemical kinetics point of view We have three types of reaction Fast reaction, intermediate reaction and slow reaction within the fraction of second complete one like fast reaction miserable time period lag like intermediate reaction and long time to complete this the very some I like me to disappear like a man duration to slow reaction one so yes Kovarim is Next, we will see the rate of reaction of chemical kinetics We will define the rate of chemical reaction We will describe it in two terms Chemical reaction is the medium of a solution We will take the concentration of the solution If there are solid gases like moles, we can also use the term amount We will define the ratio of the two terms One is rate of reaction in terms of amount and another one is rate of reaction in terms of concentration First, rate of reaction in terms of amount What is rate of reaction?
When any chemical reaction occurs, reactants continuously decrease and products continuously increase This is called as time change What is the difference between time change and time change? Reactants decrease and products increase When time change occurs, reactants in the back are decreasing Product was initially zero As time changes, products increase The amount of reactant is also changing with per unit time The amount of product is also changing with per unit time If we describe the amount of reactant or product with per unit time Rate of reaction in terms of amount Change in amount of reactant or product per unit time change in amount of reactant or product per unit time is known as rate of reaction in terms of amount it is defined as it is defined as change in amount of reactant or product reactant amount and product amount increase there are two changes amount of reactant and product per unit time per unit time in this set we have written rate of reaction in terms of amount change in amount of reactant or product which we have taken by change in time change in time how much amount has changed rate of reaction amount is change in amount of reactant or product per unit time now in its unit We need units for this. We will measure the amount in moles.
We will measure the amount of reactant and per unit in moles. Change in amount is the final amount minus initial amount. Then what happens? The amount above 2 is the mole.
Change in time. We can measure time in any unit in chemistry. It can be second, minute, hour, day. In any unit.
What is the unit? Mole bar. time.
So, we can use the units of time. So, what we can say is, mol per time, time may be second, minute, hour, anything can be used. So, this unit is mol per time. And mol per second, mol per minute, mol per hour, time is given. So, this is the unit of time.
Rate of reaction in terms of amount is mol per time. We can do the same thing. We have seen rate of reaction in terms of amount. Next we will see rate of reaction in terms of concentration. Let's restart.
Another unit or another rate of reaction. In another group, it is concentration group. Next, rate of reaction in terms of concentration.
Concentration of reactant continuously decreases and concentration of product continuously increases. with time. Time is not decreasing or increasing.
Actually, it is changing. It is defined as change in concentration of reactant or product per unit time. per unit time change in concentration of reactant or product which is also related to per unit time how much time has changed so we need to use rate of reaction in terms of concentration rate of reaction rate of reaction equals to change in concentration concentration of reactant or product which we have taken by change in time change in time the concentration changes in time if we take out the two terms, then the rate of reaction is there similarly, in the case of unit what is the change in concentration of reactant or product change in concentration means concentration of final species either reactant or product product minus concentration of initial species initial case of this go to reactant or product and the unit of concentration is mol per liter we will measure mol per liter or molarity concentration is mol per liter mol per liter by change in time time is equal to How many units are there?
Unit equals to mol per liter per time Time may be in second, minute or hour Concentration is the rate of reaction per unit per liter per time concentration case this is the answer and amount case is mol per time only liter is not coming in amount case mol per time and in this case mol per liter per time this is about simple rate now how it is increasing and decreasing we will describe it in some other video from above expression rate of reaction is the rate of reaction is the disappearance of reactant or formation of product per unit time that is all we have to say what we have seen is therefore rate of reaction is the rate of disappearance, disappearance of reactant, rate of disappearance of reactant or rate of appearance or formation, formation of product. We have written it in two words. Rate.
Rate of disappearance of reactant, the amount of reactant will disappear and rate of formation of product, the amount of product will increase. Suppose, we have a reaction, A gives B. E is. reactant LMA reactant and B is product product B is product what else we can suppose initially product is zero at time zero time reactant is not product product is zero after time after certain time when time interval increases amount of reactant decreases, it decreases continuously and amount of product continuously increases which increases, let us put it in a time, time t1, concentration of A becomes A1 it decreases and the concentration of A becomes A1 and at that time T1 concentration of B, B1 similarly at another time, time T2, in this time T1 and T2, A is still decreasing and it becomes A2 at time T2, concentration of A is A2 and B is increasing, concentration of A is B2 After time, A decreased and B increased Let us see this in a curve If we see A here, it is decreasing If we see A here, it is decreasing If we see B here, it was initially zero This is reactant and this one is product. This is time.
This is concentration. First, how much concentration of A was there? From here, it is zero. From here, A's concentration was initially zero.
After certain time, on increasing time, amount of A continuously decreases. And there at the same time, amount of B is also decreasing. B continuously increases B come out and continuously body rack was a man ago product amount continuously body to have a closer finally a becomes zero when you will finally and beats I suppose at this I if you send emails you'll am a little bit a connoisseur so our Islam ladies driver so you would have any reactions of course go to initial t1 time a1 and t2 time for a2 and a similarly for product t1 time b1 and t2 time b2 late late A1 be the concentration concentration of A at time t1 and A2 be the concentration of concentration of A at time T2 time.
Then rate or rate of reaction. In terms of reactant, A continuously decreases. Rate of disappearance of A. If we take this, what is the rate of reaction?
We will look at this. Final. Change in concentration of A by change in time. Change in concentration means final minus initial.
And final means A2 minus A1 by final time T2 minus T1. And we will introduce minus sign. And this is equal to del A by del T2. T minus del A by del T in terms of reactant case.
Now why did we write negative sign? Why did we write negative sign? Let's see.
The rate, let's see in this. The concentration of A decreases with time. This is the time concentration of A decreases.
If that decreases, then here A2 is smaller than A1. Kinegi. A1 is smaller than A2 and A2 is smaller than A1 if it is like this then the rate becomes negative your total rate is negative but actually rate is not negative so to make it positive we need to introduce negative sign in case of reactant because reactant amount continuously decreases Final concentration minus initial concentration. That will give us negative sign. But the rate will never be negative.
To make the rate positive, we will introduce a negative sign. So, the negative sign is before the negative sign. This is the result. Now, we will write the product case. Similarly, in the product case, similarly, B1 be the rate sorry b1 be the concentration of concentration of B at time t1 and b2 be the concentration of concentration of B at time t2.
t2 is the time concentration. we have already discussed b2. Now let us see the rate of reaction.
rate of reaction or as lucky when a B is the product B continuously from by Dagosha when issue rate of disappearance the one you say rate of formation rate of formation formation of B B company so many yes company final minus initial b2 minus b1 by t2 minus t1 here can they answer the time saga beyond the b2 to lose her when she b2 is greater than b1 If the rate is positive, then we do not need to introduce negative sign. It is equal to del B by del t. In terms of product, we need to introduce positive sign.
In reactant, we need to introduce negative sign. Because the amount of reactant decreases with time, but the amount of product increases with time. So we have written both rates.
rate of disappearance of A in terms of reactant and another one is rate of formation of B in terms of product product is the rate of reaction and we have found its expression rate of chemical reaction in stoichiometry suppose we are finding a specific reaction in this equation suppose a specific reaction suppose a specific reaction here H2 plus I2 this is 2HI, suppose we have a reaction here this is reaction balancer, what we see in this reaction is that 1 mole hydrogen disappears at the same time 2 mole hydrogen iodide formed or appear The rate of disappearance of hydrogen is equal to the rate of formation of hydrogen iodide This is 1 mole disappear and this is 2 mole disappear If we have to equate the rate of both of them, what should we do? If the rate of this is half and the rate of this is double, then we have to multiply it by 2 and divide it by 2 We have to do this 1 mole of hydrogen disappears and 2 mole of HI formed. 2 mole of HI one round. So in other words, other words, rate of formation of h i is double or twice is double the rate of double the rate of disappearance disappearance of h2 hydrogen iodide one rate hydrogen disappear rate one that doubles to make it like this rate of reaction equal to reactant minus del H2 by del T equal to del HI by del T 1 mole hydrogen disappear 2 mole hydrogen iodide is equal to 2 Now we have to make two equal rate or we have to multiply the rate of this or we have to divide the rate of hydrogen iodide by 2 If we divide by 2, then the rate of reaction is equal This is in terms of reactant and this one is in terms of product of the product If we take all of these, rate of reaction rate of reaction by taking all the spaces equivalent to spaces equivalent to each other.
If we write the reaction like this, rate equal to or equivalent rate we will call it as rate equal to this is disappeared. del H2 by del t equal to minus this one is also disappears or decreases del I2 by del t equal to 1 by 2 del HI by del T. This rate is called equivalent rate. This is I2. Del I2 equivalent rate.
Now let's generalize this. Let's suppose any reaction. In general, AA plus BB gives Cc plus DT.
One general reaction, general chemical reaction. rate, disappearance of A, disappearance of A, minus del A by del T, similarly another rate, disappearance of V, minus del V, V by del t is the another rate formation of C the form by Rasa formation of C or appearance of silly when a C form by when a del C by del t is the rate formation of D when a leonine del D by delta these are the individual rates so pain or say individual rate rate of disappearance of a one a minus delta a by del t and the rate of disappearance of B one minus delta B by DT and similarly rate of formation of C one one a delta C by DTS minus with a no use a product with a buyer for the command increase with answer it's the rate of formation of D one one delta D by del T or any this we can write the equivalent rate for all the molecules next, rate of reaction equivalent to each other or rate of reaction equivalent to each other we can write the equivalent rate for all the molecules or rate equal to minus the previous coefficient minus 1 by a del a by del t we will divide by the coefficient this is 1 mole if it is 2 then we will divide by 2, if it is 3 then we will divide by 3, if it is t then we will divide by t and if it is a then we will divide by a this is 1 mole equal to, we have to do all the equivalents in this case b is 1 by b minus del b by del t Next, we have to define the equivalent rate of the product Now we have to define the equivalent rate of the product rate of reaction per one mole each of reactant or product is known as known as equivalent rate equivalent rate this is equivalent rate We have taken out the equivalent rate of 1 mole and the individual rate of 1 mole From this we have to do some calculations and numericals Using these two, we will look at an example of this In a reaction, H2 plus I2 gives to HI The rate of disappearance of H2 is 10 to the power minus 6 mole per liter per second What would be the rate of appearance of HI? We have to find out the rate of disappearance of one of the two.
What are they given here? Given ma? rate of disappearance of H2 rate of disappearance of H2 is equal to we can write this value as minus del h2 by del t equal to 10 to the power minus 6 mol per liter mol per liter per second.
What we have found is rate of formation or appearance formation of h i. Del h i by del t equal to what? we know rate of reaction equivalent to each other rate of reaction equivalent to each other this is the rate of reaction equivalent to each other rate equal to minus del h2 by del t equal to minus del i2 by del t equal to 1 by 2 del hi by del t this is what we know we can write equivalent to each other this is what we know we can write equivalent to each other this is what we know We have given the value of this and we have asked for the value of this.
So now we will write two terms in this. Now we will write these two terms. What did we write? del h2 by del t minus equal to 1 by 2 del h i by del t.
Here value of this, its value is 10 to the power minus 6 equal to 1 by 2 del h i by del t. And let's write this directly, del h i by del t. Rate of formation or rate of appearance of h i equal to 2 into 10 to the power minus 6 and unit is mole per liter per second. And its answer is this. we have to calculate this 2x10-6 mol per liter per second we have to calculate this by using rate rest of the material let us discuss about average rate average rate is rate of reaction at a particular interval of time we call it as average rate same as rate of reaction but at a particular interval of time time like five minute to ten minute rate we call it average rate one minute to two minute rate we call it certain particular interval of time we call it average rate rate of reaction or it is defined as change in concentration of reactant our product product per unit time at a certain interval of time at a certain interval of time this is certain interval of time like family given other average rate of reaction money is mava next we use the suppose a reaction suppose our reaction is A gives B here A is reactant and B is product reactant and B is product yes time equal to t1 this one is a1 and this one is b1 time equal to t2 is a2 and this one is b2 means its average rate is equal to Average rate equal to u time.
T1 time to T2 time. We need rate. So we call it average rate. Average rate equal to minus.
Del. A by del t equal to del V by del t Average rate is del A by del t equal to del V by In terms of reaction, negative sign is introduced and in terms of product time, it is positive This is called average rate Now, how to measure average rate graphically? To determine the average rate graphically Determine the average rate. Average rate graphically, graphically a curve is drawn, drawn by taking concentration in y axis.
and time in x-axis. The slope of curve gives the average rate. You would normally curve draw, right? You should curve draw x-axis and this one is y-axis. In x-axis, time.
and in y-axis concentration if we draw a curve in both axis, it will be like this the slope of this curve is average rate we can also draw this curve like this and this is the time T1 and this one is T2. Maybe later. This is concentration. Concentration is decreasing.
First, A1 and A2. This is the slope. What will happen?
P by B and slope equal to P by B. A2 minus A1 by T2 minus T1 is equal to average rate We can find out graphically from this If we take a slope of any of these places, we can get the average rate from that slope We plot the concentration versus time and what is given by the curve? The curve slope is given as the average rate We can calculate graphically like this Another rate is instantaneous rate. Now, instantaneous rate is a rate of a particular instant of time.
It is defined as change in concentration concentration of reactant or product product per unit time time at a particular instant of time at a particular instant of time what happens here? change in time tends to zero time change tends to zero let us try instantaneous rate again suppose a reaction A gives B A is reactant and B is product. And in this time t1 time a a1 and b b1. Similarly at time t2, t2 time a2 and b b2.
Now we have instantaneous rate. Instantaneous rate equal to, what we call time tends to zero, limit del t tends to 0 minus del a by del t equal to limit del V by del t sorry limit del t tends to 0 when you go in with tends to 0 time tends to 0 SLM like a little something minus D a by D T small change or infinitesimal change it indicates the infinitesimal change and in it indicates the large sense equal to D V by dT is the expression of instantaneous rate dA by dT minus dA by dT equal to dB by dT This is the expression of instantaneous rate Time tends to zero, this is a infinitesimal change This is the expression of time tends to zero, this is a infinitesimal change Now let us find out graphically To determine graphically Find the instantaneous Read graphically, a curve is drawn by taking concentration along y-axis and time along x-axis x-axis R tangent is drawn on curve at that particular instant of time at that particular instant of time the slope of tangent slope of tangent gives the instantaneous rate by taking concentration in y-axis and time in x-axis draw a curve and draw a tangent at the point of time draw a curve at x-axis and y-axis and the time at y-axis draw a curve If we draw a curve at this time, then we can draw a tangent at this time. Now let us find the slope of this tangent. What is the slope of this tangent?
It is the instantaneous rate of reaction. Slope of tangent equal to instantaneous rate of reaction. rate the slope your instantaneous rate is the slope of tangent we can get it from the slope of tangent in case of instantaneous rate of reaction we draw a curve and the tangent is drawn from the point of curve and the instantaneous rate of reaction is obtained from the slope of tangent this is the rate of instantaneous rate of average rate another heading is factors affecting the rate of reaction which factors affect or which factor increases the rate of reaction or which factor decreases the rate of reaction factors affecting the rate of reaction we will describe the factors that affect the rate of reaction in this case, we will describe the main factors that affect the rate of reaction we will describe the factors that affect the rate of reaction on the nature of reactant nature of reactant another one is concentration Concentration of reactant. Concentration of reactant.
Third one. Surface area. Area of reactant.
Surface area of reactant. D. Catalyst. Catalyst. E. Temperature.
temperature and f sign light light or radiation main these are the main factors that affect the rate of reaction is six what effect role i'm going to describe here so first nature of reactant concentration of reactants surface area of reactant catalyst temperature and light or radiation effect or less and custody rate of reaction like balance and auto-cassette consumption manicure economy one by one described so first factor affecting the rate of reaction first factor One is nature of reactant. Nature of reactant. Reactant depends on nature.
What is nature of reactant? What is nature of reacting species? If the reacting species are ionic in nature or the reacting species contains ionic bond, the rate of reaction is fast. So, rate of reaction is fast. And if the rate of reaction is fast, the rate of reaction is fast.
reacting species contains covalent bond or covalent in nature then rate of reaction will be slow because ionic bonds will be fast formed and break down easily but covalent bond process is long process and break down process is also long process so covalent bond species rate will be slow what we will say is rate of reaction increases if the nature of reactants are ionic or we also call it as Electrovalent. So, the reaction rate is fast in ionic nature. In this example, we can say that some of the fasts are neutralization reaction, neutralization reaction, precipitation reaction, precipitation reaction, and fast reaction. These are fast reactions.
Rate of reaction is slow if the nature of reactants are covalent If the nature of reactants is covalent, then the rate of reaction will be slow For example, organic reaction Reaction or slow reaction. Organic reaction is slow reaction because organic reaction contains covalent bond. If covalent bond is there, then your reaction is slow. Nature of reactant is not important.
I know nature of reactant is fast and covalent nature of reactant is slow. Another factor, concentration of reactant. 2 number, concentration of reactant.
concentration of reactant also depends on the concentration of reactant on increasing concentration rate of reaction increases if concentration increases rate of reaction increases on increasing concentration number of reacting species increases which increases the effective collision number of reacting species increases effective collision increases if effective collision increases rate of reaction increases more number of reacting species converted into product many number of reacting species converted into product so rate of reaction increases on increasing concentration increasing concentration concentration number of reacting species increases concentration increase number of reacting species body increases which increases the increases the effective collision. The more number of reacting spaces increase, the more the collision increases. Collision increases means effective collision. Effective collision which increases the effective collision. As a result, rate of reaction increases.
Rate of reaction increases. The more the number of molecules, the more the rate of reaction and if we decrease the concentration, the rate of reaction decreases Now let's look at some examples Conch HCl reacts vigorously with CaCO3 then Kankh SL reacts vigorously with calcium carbonate then dilute SL Dilute SL has low number of reacting species and it can't react vigorously But Kankh SL has a lot of reacting species and it reacts fast So if we increase concentration rate of chemical reaction increases Now we will discuss about another factor Another factor another factor is surface area of reactant how to define surface area of reactant on increasing surface area, if we increase surface area of a solid, then number of molecules exposure increases many molecules are present on surface, exposure increases and if you increase the number of molecules, the rate of reaction increases automatically and the rate of reaction increases so what happens here? on increasing surface area rate of reaction increases increases and vice versa If we decrease surface area, rate of reaction decreases How to increase?
On increasing surface area, number of molecules exposed increases which increases the effective collision to give product Can we give product by effective collision? Generally, if we convert calcium carbonate solid into powder, surface area increases by 10 to the power 6 times If we convert some of the material into powder, the surface area increases by 10 to the power 6 times If 10 to the power 6 times surface area increases, the rate of reaction increases In this example, dilute HCl reacts vigorously with Powder CaCO3 then lump of CaCO3 or piece of CaCO3 Converting in powder form will give a fast reaction But it will be more solid than solid Solid will have less surface area and powder form will have more surface area As we make small pieces, surface area will increase If we convert powder into powder, surface area of powder increases 10 to the power 6 times So the reaction is very fast So the rate of reaction increases when surface area increases Next another factor is catalyst What does catalyst do? Catalyst may or may not or may increase or decrease can be increased or decreased.
First, what is catalyst? Catalyst is a third chemical substance which increases or decreases the rate of chemical reaction without itself being consumed. Generally, catalyst increases the rate of reaction. The chemical substance increases the rate of reaction.
chemical substance which increases or decreases which increases or decreases the rate of chemical reaction without itself being consumed If you don't consume it, then you can increase or decrease the rate of chemical reaction That is why we call it as catalyst There are two types of catalysts catalyst are of following two types two types one is positive catalyst positive catalyst positive catalyst one of the catalyst which increases the rate of reaction positive catalyst increases the rate of reaction by providing alternative pathway having lower activation energy activation energy is less than this. It increases the rate of reaction increases the rate of reaction rate of reaction by providing alternative pathway having lower activation energy lower activation energy this means lower activation energy another path is found out which has less activation energy that is why positive catalyst increases the rate of reaction another type of catalyst is negative catalyst negative catalyst The catalyst which decreases the rate of reaction. It decreases the rate of reaction by providing alternative pathway having higher activation energy.
It increases the rate of reaction by providing alternative pathway having higher activation energy. It decreases the rate of reaction. Generally, we understand that the rate of reaction of catalyst is increased We generally use positive catalyst to increase the rate of reaction We will also see the energy profile diagram of the catalyst Now we will see how the catalyst increases the rate of reaction We will make two curves Here this is x axis and this one is y axis ER means energy of reactant which means energy of reactant we will take activation energy of this this activation energy is not used in catalyst This is Ea, activation energy. This path is uncatalysed.
If we don't use catalyst, we need to supply this much energy to create this reaction. This is uncatalysed. If we use catalyst, it is an alternative path.
This is Ea. Ea'is the catalysed path Ea'is the catalysed path EP is greater than ER So this reaction is known as endothermic reaction. This is called endothermic reaction.
In this figure, energy profile diagram of catalyzed N. Uncatalyzed, catalyzed and uncatalyzed endothermic reaction endothermic reaction similarly now we have seen one thermic is x y in this suppose here e r energy of reactant this is energy of product here is ER is greater than EP so this is exothermic for this we need EA activation energy if we use catalyst EA dash this is uncatalysed uncatalyzed and this one is catalyzed catalyzed path and here is progress of progress of reaction progress of reaction here energy energy is increasing and figure what we see here is that we should not use catalyst but we should use activation energy to provide the catalyst when she was an exothermic reaction energy profile diagram energy profile diagram of catalyzed and uncatalyzed exothermic reaction This is catalyzed and uncatalyzed. This is exothermic and this is endothermic reaction energy profile diagram.
By using positive catalyst, we can decrease activation energy. By decreasing activation energy, we can reduce the energy variation and the rate of reaction becomes faster. We can make only one of these. If you want to make specific one, you can make it. Another factor is temperature.
In general, on increasing temperature 10 degree Celsius, 10 degree Celsius rate of reaction increases by two to three times. Doi dekhi thin times rate of reaction what sir. Which can be described on the basis of your temperature coefficient curve what I describe.
Which can be described. on the basis of temperature coefficient curve we can see temperature coefficient curve and temperature coefficient means Now we will plot the curve and see how the temperature is increasing from the curve plot. Now we have started plotting the curve. This is x-axis and this one is y-axis.
And this energy is zero. This is where the energy increases. We have energy of activation here.
If we cross energy of activation here, the reactants will convert into powder. And this will convert into powder if it reaches here. And this temperature is T Kelvin temperature.
So, fraction of molecules. fraction of molecules here zero energy molecules are not there, more are there but the energy of activation is not there if we increase the temperature the energy of the molecules in the middle increases the molecules reach here all of them reach here and the energy of the molecules If this is x, then this will be 2 to 3 x This is T plus 10 Kelvin We can call this temperature coefficient curve or maximum distribution curve This is the number of molecules on increasing, previously there were 13 molecules in T Kelvin We can call this increasing temperature mobility increases which increases the effective collision if effective collision increases, the activation energy is not reached if we increase the reaction rate of many molecules, the reaction rate increases if this was x before, now the reaction rate is 2 to 3 2 to 3 times the reaction rate is increasing as the temperature increases, the reaction rate increases next, another factor another factor's 6 number is light light or radiation this is the factor light or radiation this also changes the rate of reaction so what happens here rate of reaction increases by using light not all of them increases only photochemical reactions increase the rate rate of reaction rate of reaction increases increases on increasing intensity of light in photochemical chemical reaction. and the intensity of light decreases, the rate increases.
Like photosynthesis and formation of hydrogen chloride in the presence of sunlight, the reaction increases and the rate increases. These are the factors affecting the rate of reaction. I have already described six of them.
The main factors are 1. Nature of reactant If the reactants are ionic in nature, the reaction is fast. And if the reactants are ionic in nature, the reaction is fast. the reactants are covalent in nature the rate of reaction is slow another concentration concentration only on increasing concentration rate of reaction increases concentration number of reacting species increases which increases the effective collision so rate of reaction also increases another surface area of reacting, reacting species are reactant. On increasing surface area number of molecule exposed increases which increases the effective collision or which increases the rate of reaction that increases the rate of reaction and if we change a piece of powder form, its surface area 10 to the power 6 times more another catalyst, catalyst generally increases the rate of reaction by providing alternative pathway having lower activation energy, lower activation energy theory, rate of reaction, we will work on increasing it, another temperature, temperature, on increasing temperature, average kinetic energy of reacting species increases, which increases the mobility of molecules or reacting species, as a result, rate of reaction increases, in general, in general, on increasing 10 degree Celsius or 10 Kelvin, rate of reaction increases by 2 to 3 times n Another one is, last one is light or radiation. Last factor is light or radiation.
On increasing intensity of light, rate of photochemical reaction increases. These are the factors that affects the rate of reaction. Next, another heading is rate law equation.
Rate law equation. Rate of reaction depends upon the concentration of reacting species. yes much i depend garcer rate of reaction depends upon the concentration of reactant or reacting species concentration of reacting species concentration concentration my depending garcer suppose a reaction suppose a reaction, suppose we have a reaction A plus BB gives product suppose we have a reaction now in this rate of reaction May not depends on the all concentration. Term A of A and all concentration. term B of B The rate of chemical reaction depends on A and B Let us see how much it depends on A and B experimentally rate of reaction depends on the concentration of depends on this one.
Let's write m concentration of A and n concentration of B. We have written m and n in this way. m and n may or may not be equal to A and B. It can be equal to or not equal to.
If this is the case, then rate is directly proportional to a power m and b power n. That is, the power above this is a. We can also not do it with a.
We can also not do it with a. We can also not do it with m and m. Then rate is equal to k a power m and b power n.
Here, m and n may or may not be equal to a and b. the exact value of the stoichiometric coefficient can be the same or not So we will take the value of the stoichiometric coefficient as the rate and concentration of the experimentally moving zone How to define the rate and concentration of the stoichiometric coefficient? The value of m and n can be the same or not So we will define the rate like equation Rate like question is defined as the mathematical expression which shows how the rate of reaction related with concentration.
How does it relate to concentration? It is defined as or rate like equation equation is defined as defined as the mathematical expression expression which shows how the rate of reaction depends with concentration concentration that is all we need to know how the rate of reaction depends with concentration how concentration depends with concentration that is all we need to know that is all we need to know that is all we need to know rate law equation that is all we need to know Next, rate constant. What is rate constant?
And what is velocity constant? Suppose a reaction A gives product. concentration of concentration is to take me specificly proportional to rate to the real scenario for personal server and press my only like him in the case go lucky you rate directly proportional to a power young era young for a company so I can go be power Ian and here rate equal to k a power m B power Ian where k is proportionality proportionality constant constant and is known as and is known as rate constant your proportionality constant lambda rate constant one so real logic defined when when a equal to b equal to one mol per liter one mole per liter if the concentration is equal to one mole per liter then rate equal to k one power m and one power n one is equal to one and rate equal to k and k equal to rate k equal to rate we will define this rate constant is defined as rate of reaction when concentration of reacting species is unit or concentration of reacting species is 1 mole per liter from above expression rate constant may be defined as rate constant may be defined as rate of reaction when concentration of reacting species is unity or unit value.
When unit value is there, we call it rate constant. So this is the definition. Now we have to find out the units.
Next, units of rate constant. Let us start with the units of rate constant. Suppose, we start with reaction.
A plus B gives product. Now, if we write rate law equation, then k equal to k, a power m and b power n. a power m and b power n. If a equal to b, then rate equal to k, a power m plus n.
Rate equal to k. a power m plus base m times m plus n. Now we need to find the unit. We will find the unit by using different methods. We will find the unit by using different methods.
For the first order, we will find the unit by using different methods. For the first order, we will find the unit by using different methods. m plus n equals to zero.
m plus n equals to zero. m plus n is zero. If m plus n is zero, then we have to write rate equal to k a power zero.
a power zero. We have to write k unit. So, k equal to rate by a power zero.
k equal to a power zero. A power zero is one. Only rate. k equal to rate unit is mol per liter and per time which time is in which unit and k equal to mol per liter per time rate constant of zero order is mol per liter per time The unit can be different like time can be in minutes or seconds So the unit of rate and time is same So we will find out the first order, second order and third order For first order, m plus yon equal to 1 These two sums must be 1 Then rate equal to 1 to our k a power 1 and k equal to rate by a power 1. Now rate means mole per liter per time and concentration concentration means mole per liter.
Liter liter cancel and mole mole cancel equal to only 1 by time or k1 rate constant for first order indicates the per time per time is the unit of first order now let us see second order for second order m plus n equal to 2 m plus n equal to 2. This is the 2 of the two. Then rate equal to k a power 2 or k equal to rate by a power 2. Let's keep this. Rate is mole per liter per time and unit of concentration is mole square by liter square. and here mole and 1 mole cancel 1 liter and 1 liter cancel equal to what is liter by time by mole and equal to what is liter per time per mole what is k2 for second order integrated rate constant rate sorry rate constant for second order liter per time per mole is k units a liter per time per mole is the grammar third order question for third order third order m plus n equal to 3 sum of the m and n is 3 and rate equal to fourth order rate equal to k a power 3 and k equal to rate by a power 3 unit of rate mol per liter and a cube means mol cube per liter cube and if we cancel this then what will be left?
liter square, liter square, liter 1 cancel and mol, mol cancel and liter time, liter time, liter square time per time per mole square. What is this? K3. Third order. Liter square per time per mole square.
Or liter square per mole square per time. third order rate constant units so what we have described? zero order, first order, second order and third order units next order of reaction order of reaction is the sum of concentration terms rate like equation.
So rate like equation means the sum of all the powers of concentration term in rate like equation. in rate like equation is known as known as order of reaction rate like equation is the sum of power order of reaction is experimental parameter parameter it cannot be obtained by theoretical reaction we can do experimentally and its value may be in may be its value may be 0 or fraction or negative or positive we can choose we can choose order of reaction depends with physical condition of reaction if we change the physical condition like pressure temperature concentration change order of reaction may be changed it is it depends with physical character of reaction like temperature, pressure, concentration, catalyst if we change these, order of reaction can be changed simply order of reaction is the sum of the powers of concentration term in rate like equation order of reaction is experimental parameter its value can be 0, negative, whole number, positive or fraction order of reaction depends on physical properties if we change physical parameters, order may be changed now we will write the expression suppose a reaction Suppose a reaction, we will call it a reaction. A, A plus B, B gives product. Here rate law equation, rate equal to K, A power M and B power N.
Here M plus N equal to order of reaction. Rate law equation, concentration is given as a. power, we will call the sum as order of reaction.
If m plus n equal to 0 if the value of m plus n is 0, the reaction is 0 order if m plus n equal to 1, the reaction is first order first order is the if m plus n equal to 2 the reaction is second order is the if m plus n equal to 3 the reaction is third order the higher order reaction are here higher order reaction are here higher order Reactions are higher order reactions are very rare molecularity another term is molecularity molecularity is the first first order and molecularity is same molecularity is the theoretical parameter we can measure the reaction of a molecule molecularity is number of reacting spaces simultaneously collide to give product. How many molecules and how many reacting species have simultaneously collided to give product. How many are involved. We call that molecularity. Number of reacting species or molecules reacting species simultaneously collide to give Product is known as molecularity.
It is theoretical parameter. It can be obtained. from a balance balance it can be obtained from balance chemical chemical reaction it can be obtained from balance chemical reaction and the value of molecularity is non-zero positive integer it is not zero, it is not negative, it is only positive whole numbers value of molecularity molecularity is non-zero positive integer non-zero positive integer molecularity is an invariant species or invariant product physical properties do not depend on it does not it does not depends with Physical properties Physical properties It is an invariant product It does not depend on any physical properties This was about molecularity If molecularity of Clarity of reaction is 1 It is not 0, it is 1 The reaction is the reaction is unimolecular unimolecular similarly if molecularity of reaction is 2 the reaction is bimolecular bimolecular if the molecularity of reaction is 3 The reaction is termolecular or trimolecular and so on.
Higher molecularity are rare. What is higher molecularity? It is rare. Why is it not happening? Let's see.
One molecule can produce a product from here. The probability of two colliding is high. If three come in the same place, the probability of three coming is lower. And if four come, the probability of three coming is higher.
The probability of these four molecules colliding at the same time is very rare So the higher molecularity is rare Lower molecularity is the only one that increases And this is about molecularity Next, difference between order and molecularity or molecularity and order How to do the difference between the two? First, what do we call order? order is the sum of the concentration term in rate law equation and molecularity is the number of reacting species simultaneously collide to give product which i could definition and either order theory you keep the order is experimental parameter but molecularity is theoretical parameter and order can be calculated from experiment or practical and molecularity can be calculated from balanced chemical equation and value of order maybe zero negative fraction and the value of molecularity non zero positive whole number order of reaction depends with physical properties like temperature, pressure, concentration, catalyst all depends on each other and molecularity is invariant product or it does not depends with physical properties or does not change with changing physical properties like pressure, temperature, concentration, catalyst all does not change with changing physical properties like pressure, temperature, concentration, order and molecularity.