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Elements and Isotopes.txt | Now in each case because this is a carbon atom it must have the same number of Z. The atomic number must be the same. In other words, all three have six protons. But notice carbon twelve has six neutrons. Carbon 13 has seven neutrons and carbon 14 has eight neutrons thereby giving the atomic mass six plus 612, six plus 713 and six plus eight is 14. So that makes sense because to get the atomic mass to get the a you have to add up the protons and neutrons. |
Elements and Isotopes.txt | But notice carbon twelve has six neutrons. Carbon 13 has seven neutrons and carbon 14 has eight neutrons thereby giving the atomic mass six plus 612, six plus 713 and six plus eight is 14. So that makes sense because to get the atomic mass to get the a you have to add up the protons and neutrons. Now there is a unit that scientists created to deal with very, very small amounts of atoms. Now the AMU, or atomic mass unit is the unit of mass used for elements and compounds. Now by definition we define that one atom, a single atom of carbon. |
Elements and Isotopes.txt | Now there is a unit that scientists created to deal with very, very small amounts of atoms. Now the AMU, or atomic mass unit is the unit of mass used for elements and compounds. Now by definition we define that one atom, a single atom of carbon. Twelve is composed of twelve AMU and everything else is relative to this amount. For example, an H atom is one AMU and it's relative to this. In other words, this is twelve times that's heavier in terms of AMU than an H atom. |
Elements and Isotopes.txt | Twelve is composed of twelve AMU and everything else is relative to this amount. For example, an H atom is one AMU and it's relative to this. In other words, this is twelve times that's heavier in terms of AMU than an H atom. A single h atom. Now, note that this is one atom of carbon. That's a very tiny amount. |
Crystalline Solids and Amorphous Solids .txt | So, from experiencing the world around us, we know that solids come in many different forms, sizes and shapes. Now, in this lecture, we're going to look at exactly that. We're going to examine the different type of structures formed by solids. So two main types of structures exist, and we'll talk about Crystalline Solids or simply crystals and amorphous solids. So let's begin with the crystalline solids. So all Crystalline Solids or simply crystals have a very well ordered shape or structure. |
Crystalline Solids and Amorphous Solids .txt | So two main types of structures exist, and we'll talk about Crystalline Solids or simply crystals and amorphous solids. So let's begin with the crystalline solids. So all Crystalline Solids or simply crystals have a very well ordered shape or structure. And because of that, they have a very sharp melting point. What that means is that the melting point's range is very small. It melts over a very, very small range of temperature. |
Crystalline Solids and Amorphous Solids .txt | And because of that, they have a very sharp melting point. What that means is that the melting point's range is very small. It melts over a very, very small range of temperature. Now. Four main types of Crystalline solids or simply crystals exist. Ionic Crystalline solids. |
Crystalline Solids and Amorphous Solids .txt | Now. Four main types of Crystalline solids or simply crystals exist. Ionic Crystalline solids. Metallic Crystalline solids. Molecular Crystalline solids and network covalent crystalline solids. Now, let's begin with our ionic crystals. |
Crystalline Solids and Amorphous Solids .txt | Metallic Crystalline solids. Molecular Crystalline solids and network covalent crystalline solids. Now, let's begin with our ionic crystals. Now, these crystals consist of ions that are held together by electrostatic forces. Electrostatic forces are forces between positively charged ions and negatively charged ions of different atoms. Now, let's see in some examples. |
Crystalline Solids and Amorphous Solids .txt | Now, these crystals consist of ions that are held together by electrostatic forces. Electrostatic forces are forces between positively charged ions and negatively charged ions of different atoms. Now, let's see in some examples. Sodium chloride is an ionic crystal. Lithium chloride is also an ionic crystal. Calcium chloride or calcium dichloride is also an ionic crystal. |
Crystalline Solids and Amorphous Solids .txt | Sodium chloride is an ionic crystal. Lithium chloride is also an ionic crystal. Calcium chloride or calcium dichloride is also an ionic crystal. And basically, whenever an alkaline metal or an alkaline earth metal reacts with a halogen, these guys will always produce, or will most of the time actually will always produce ionic crystals. Now let's look at metallic crystals. Now, these guys consist of single metal molecules that are held together by a sea of electrons. |
Crystalline Solids and Amorphous Solids .txt | And basically, whenever an alkaline metal or an alkaline earth metal reacts with a halogen, these guys will always produce, or will most of the time actually will always produce ionic crystals. Now let's look at metallic crystals. Now, these guys consist of single metal molecules that are held together by a sea of electrons. And examples include any type of alkali metal or alkaline earth metal. For example, a composite which actually isn't an alkaline or alkali metal, but is a transition metal, but still it's a metal that has a metallic solid structure. Other examples are sodium metal or potassium metal or leafy metal or calcium metal. |
Crystalline Solids and Amorphous Solids .txt | And examples include any type of alkali metal or alkaline earth metal. For example, a composite which actually isn't an alkaline or alkali metal, but is a transition metal, but still it's a metal that has a metallic solid structure. Other examples are sodium metal or potassium metal or leafy metal or calcium metal. Any of these guys have a metallic like structure or metallic crystal structure. So now let's look at the third type of Crystalline Solids known as molecular solids. Now, these crystals, or these Crystalline solids consist of molecules held together by intermolecular forces called down their balls forces. |
Crystalline Solids and Amorphous Solids .txt | Any of these guys have a metallic like structure or metallic crystal structure. So now let's look at the third type of Crystalline Solids known as molecular solids. Now, these crystals, or these Crystalline solids consist of molecules held together by intermolecular forces called down their balls forces. And examples include ice. In other words, when you freeze ice, when you take energy away from water and form ice, the water molecules form a very structured formation. And this creates what we know as ice. |
Crystalline Solids and Amorphous Solids .txt | And examples include ice. In other words, when you freeze ice, when you take energy away from water and form ice, the water molecules form a very structured formation. And this creates what we know as ice. And ice are called molecular crystals or molecular solids. The fourth and final type of Crystalline Solids we're going to look at are network covalent crystals. Now, these consist of network of atoms or molecules held together by covalent bonds. |
Crystalline Solids and Amorphous Solids .txt | And ice are called molecular crystals or molecular solids. The fourth and final type of Crystalline Solids we're going to look at are network covalent crystals. Now, these consist of network of atoms or molecules held together by covalent bonds. These covalent bonds can be both non polar and polar covalent. Now, an example is diamonds. So what's the structure of a diamond? |
Crystalline Solids and Amorphous Solids .txt | These covalent bonds can be both non polar and polar covalent. Now, an example is diamonds. So what's the structure of a diamond? Diamond consists of solely carbon atoms held together by covalent bonds. These Sigma covalent bonds are very strong, and that's exactly why our diamonds are so strong. It's very hard to break diamonds. |
Crystalline Solids and Amorphous Solids .txt | Diamond consists of solely carbon atoms held together by covalent bonds. These Sigma covalent bonds are very strong, and that's exactly why our diamonds are so strong. It's very hard to break diamonds. Now let's look at the second type of structures of solids. And these guys are known as amorphous solids. Now, these guys don't really have a well structured shape and because of this, they melt over a very wide range of temperatures. |
Crystalline Solids and Amorphous Solids .txt | Now let's look at the second type of structures of solids. And these guys are known as amorphous solids. Now, these guys don't really have a well structured shape and because of this, they melt over a very wide range of temperatures. Examples of this include some plastics and some glass. Now, we should also mention that there is another type of solid or another type of formations that solid solids form. And this is called polymers. |
Crystalline Solids and Amorphous Solids .txt | Examples of this include some plastics and some glass. Now, we should also mention that there is another type of solid or another type of formations that solid solids form. And this is called polymers. Now, we can have both polymers of amorphous solids and polymers of crystalline solids. Now, when we melt polymer solids very quickly, we get amorphous solids. When we melt polymers very slowly over a very long range of time, we get crystalline solids. |
Crystalline Solids and Amorphous Solids .txt | Now, we can have both polymers of amorphous solids and polymers of crystalline solids. Now, when we melt polymer solids very quickly, we get amorphous solids. When we melt polymers very slowly over a very long range of time, we get crystalline solids. Now, some examples of biopolymers biological polymers include DNA proteins which are basically composed of many amino acids. Macromolecules such as carbohydrates glycogen, for example, starch. All these guys are examples of biological polymers. |
Electromotive force.txt | So that means in electrochemical cells called voltaic cells, electrons flow from the Higher electric potential electrode, the lower electric potential electrode. So that means they travel from the anode electrode to the cathode electrode. So we can define something called the electromotive force or simply EMF as the difference in this electric potential between the anode and the cathode. So to really understand what the Electric Motor Force is, we have to explore a concept called Electric Potential Energy. So electric potential energy, or simply electrical work is equal to the charge of an object times the change in electrical potential. Now, we just said the change in electrical potential between the animal and the capital is simply EMF. |
Electromotive force.txt | So to really understand what the Electric Motor Force is, we have to explore a concept called Electric Potential Energy. So electric potential energy, or simply electrical work is equal to the charge of an object times the change in electrical potential. Now, we just said the change in electrical potential between the animal and the capital is simply EMF. So this is our EMF. So in order to understand what the EMF is, we have to really understand what charges and what electrical work or electrical potential energy is. So let's look at electrical work first. |
Electromotive force.txt | So this is our EMF. So in order to understand what the EMF is, we have to really understand what charges and what electrical work or electrical potential energy is. So let's look at electrical work first. So electrical potential energy is similar to gravitational potential energy. So we know that any two objects say this marker and this marker will pull each other and this pull will be due to their masses. And the pull or the force is given by the gravitational constant. |
Electromotive force.txt | So electrical potential energy is similar to gravitational potential energy. So we know that any two objects say this marker and this marker will pull each other and this pull will be due to their masses. And the pull or the force is given by the gravitational constant. Time mass one times mass two divided by the distance between them. Now, the electrical potential energy is similar to this concept, except now they will pull each other not due to mass, but due to charge. So if this object has a charge one and this object has charge two, and their charges are opposite, then they will pull each other. |
Electromotive force.txt | Time mass one times mass two divided by the distance between them. Now, the electrical potential energy is similar to this concept, except now they will pull each other not due to mass, but due to charge. So if this object has a charge one and this object has charge two, and their charges are opposite, then they will pull each other. Now, if the charge are the same charge, they will push away. And that's the difference between electrical potential energy and gravitational potential energy. So let's look at what charge is. |
Electromotive force.txt | Now, if the charge are the same charge, they will push away. And that's the difference between electrical potential energy and gravitational potential energy. So let's look at what charge is. Charge is simply the amount of electrons found in some object. And charge is measured in units called coulombs. And one electron. |
Electromotive force.txt | Charge is simply the amount of electrons found in some object. And charge is measured in units called coulombs. And one electron. One electron has a charge of 1.622 times ten to the negative. 19 coulombs. So that means two electrons will be two times this amount, three electrons, three times this amount, and so on. |
Electromotive force.txt | One electron has a charge of 1.622 times ten to the negative. 19 coulombs. So that means two electrons will be two times this amount, three electrons, three times this amount, and so on. Now, my question is, how many electrons are found in one coulomb of charge? Well, to find that answer, we must divide one coulomb by 1.622
times ten to 19 coulombs per electron. And that will give us 6.24 times 18 electrons. |
Electromotive force.txt | Now, my question is, how many electrons are found in one coulomb of charge? Well, to find that answer, we must divide one coulomb by 1.622
times ten to 19 coulombs per electron. And that will give us 6.24 times 18 electrons. So this many electrons will be found in one coulomb of charge. That means a coulomb is a pretty big amount of charge. So whenever someone says one coulem of charge moves from this position to this position, that means 6.24
times ten to the 18 electrons move from this position to this position. |
Electromotive force.txt | So this many electrons will be found in one coulomb of charge. That means a coulomb is a pretty big amount of charge. So whenever someone says one coulem of charge moves from this position to this position, that means 6.24
times ten to the 18 electrons move from this position to this position. That's what a coulomb is. That's what charges it's. The movement of electrons from some point A to some point B. |
Electromotive force.txt | That's what a coulomb is. That's what charges it's. The movement of electrons from some point A to some point B. So, now that we know what electrical work is and what charges, we can rearrange this formula to give us the change in electric potential. So, by bringing this guy over to this side, we get electrical work divided by charge. And by the way, electrical work, like any work, has the units of Joules. |
Electromotive force.txt | So, now that we know what electrical work is and what charges, we can rearrange this formula to give us the change in electric potential. So, by bringing this guy over to this side, we get electrical work divided by charge. And by the way, electrical work, like any work, has the units of Joules. So the units of electrical work divided by charge is Joules divided by Coulomb. And this equals our changing electrical potential, which is also the voltage difference. And which is also what we said before is the electromotive force or EMF. |
Electromotive force.txt | So the units of electrical work divided by charge is Joules divided by Coulomb. And this equals our changing electrical potential, which is also the voltage difference. And which is also what we said before is the electromotive force or EMF. Now, whenever we talk about the EMF of an electrochemical cell, we could also call our EMF the cell voltage because we're talking about an electrochemical cell. And the cell voltage shows how much work can be done for every coulomb produced by a redox reaction in an electrochemical cell. So that basically says that when in an electrochemical cell, one coolant of charge moves from the anode to the cathode, x amount of work can be done. |
Electromotive force.txt | Now, whenever we talk about the EMF of an electrochemical cell, we could also call our EMF the cell voltage because we're talking about an electrochemical cell. And the cell voltage shows how much work can be done for every coulomb produced by a redox reaction in an electrochemical cell. So that basically says that when in an electrochemical cell, one coolant of charge moves from the anode to the cathode, x amount of work can be done. So let's now look at the difference between this battery or this electric chemical cell and this smaller electrochemical cell. So let us examine the difference between this D battery and the AAA battery. Well, according to this label, it says that our electromotive force of this deep battery is exactly 1.5 volts. |
Electromotive force.txt | So let's now look at the difference between this battery or this electric chemical cell and this smaller electrochemical cell. So let us examine the difference between this D battery and the AAA battery. Well, according to this label, it says that our electromotive force of this deep battery is exactly 1.5 volts. So EMF of D is 1.5
volts. What is the EMF of the AAA battery? Well, the EMF of this guy is also 1.5 volts. |
Electromotive force.txt | So EMF of D is 1.5
volts. What is the EMF of the AAA battery? Well, the EMF of this guy is also 1.5 volts. So EMF is 1.5 volts. That's weird. How come this more expensive larger battery has the same EMF as the smaller and cheaper battery? |
Electromotive force.txt | So EMF is 1.5 volts. That's weird. How come this more expensive larger battery has the same EMF as the smaller and cheaper battery? Well, let's examine exactly what EMF is. Remember, EMF is the amount of energy produced when warm Coulomb travels from this anode to this cathode. Or said another way, when 6.24
times ten to the 18 electrons travel from this point to this point, they produce 1.5 joy or joules of work. |
Electromotive force.txt | Well, let's examine exactly what EMF is. Remember, EMF is the amount of energy produced when warm Coulomb travels from this anode to this cathode. Or said another way, when 6.24
times ten to the 18 electrons travel from this point to this point, they produce 1.5 joy or joules of work. So what this means is that in this battery and in this battery, when one Coulomb charge travels from the animals to the cathode, both batteries produce the same amount of work. The same energy is released to do work. So what's the difference between the D and the AAA? |
Electromotive force.txt | So what this means is that in this battery and in this battery, when one Coulomb charge travels from the animals to the cathode, both batteries produce the same amount of work. The same energy is released to do work. So what's the difference between the D and the AAA? Why is this more expensive? Well, it's more expensive because it's bigger. It could hold more charge. |
Electromotive force.txt | Why is this more expensive? Well, it's more expensive because it's bigger. It could hold more charge. That's the difference. This guy holds much more charge and eventually the charge here will run out. But this guy will still have enough charge. |
Electromotive force.txt | That's the difference. This guy holds much more charge and eventually the charge here will run out. But this guy will still have enough charge. So the charge and electrons will continue traveling from here to here. So this guy literally houses more electrons and that's why it's more expensive. So, for example, this battery will be able to run a light bulb for say, 15 minutes, while this guy will run a light bulb for say, 4 hours. |
Henderson Hasselbalch example .txt | In this example, we begin with 0.05 molar of Peruvic acid and 0.07 molar of sodium Peruvine. Our ka for our acid is 3.1 times ten to negative three. We want to find the PH of our buffer solution. Once we mix these two guys, there are two methods we can use use to find the PH of the buffer solution. Our first method involves the Henderson Hasselblack formula. And if you haven't seen this formula before or you don't know where it comes from, check out the link below. |
Henderson Hasselbalch example .txt | Once we mix these two guys, there are two methods we can use use to find the PH of the buffer solution. Our first method involves the Henderson Hasselblack formula. And if you haven't seen this formula before or you don't know where it comes from, check out the link below. The second method is to simply use the Ka. So let's do the first method first. So our PH is equal to PKA plus or log of concentration of conjugate base divided by the concentration of conjugate acid. |
Henderson Hasselbalch example .txt | The second method is to simply use the Ka. So let's do the first method first. So our PH is equal to PKA plus or log of concentration of conjugate base divided by the concentration of conjugate acid. This equals, remember, PKA is simply negative log of Ka. So this equals negative log of Ka. And our Ka is 3.1
times tens of eight. |
Henderson Hasselbalch example .txt | This equals, remember, PKA is simply negative log of Ka. So this equals negative log of Ka. And our Ka is 3.1
times tens of eight. So we plug it into here plus log of this guy over this guy we get 0.07 over 0.05
approximately equals we plug this into our calculator and we get 2.65. So that's our PH. Now let's find using the same PH using the Ka. |
Henderson Hasselbalch example .txt | So we plug it into here plus log of this guy over this guy we get 0.07 over 0.05
approximately equals we plug this into our calculator and we get 2.65. So that's our PH. Now let's find using the same PH using the Ka. So remember, our equation for conjugate acid and conjugate base is conjugate acid plus our water gives us conjugate base plus our hydronium ion. So let's write the equilibrium equation for this guy. So, Ka, our acid ionization constant is equal to the concentration of hydronium times the concentration of Pyruvate divided by the concentration of pyruvic acid. |
Henderson Hasselbalch example .txt | So remember, our equation for conjugate acid and conjugate base is conjugate acid plus our water gives us conjugate base plus our hydronium ion. So let's write the equilibrium equation for this guy. So, Ka, our acid ionization constant is equal to the concentration of hydronium times the concentration of Pyruvate divided by the concentration of pyruvic acid. Now, initially we begin with some amount of this guy and some amount of this guy, right? We don't have any of this guy. Or we approximate this guy to be zero. |
Henderson Hasselbalch example .txt | Now, initially we begin with some amount of this guy and some amount of this guy, right? We don't have any of this guy. Or we approximate this guy to be zero. At the end of our equilibrium, this guy is x. And since this and this is a ratio of one to one, this guy must be x two. So the concentration of this guy increases by x. |
Henderson Hasselbalch example .txt | At the end of our equilibrium, this guy is x. And since this and this is a ratio of one to one, this guy must be x two. So the concentration of this guy increases by x. The concentration of this guy increases by x, and the concentration of this guy decreases by x because this guy dissociates into this guy. So we get our hydronium concentration, we represent as x. Our pyruvate concentration we present as x because we begin with this concentration divide by since we begin with this amount of Peruvic acid and then some dissociates into the conjugate base, we say that it's 0.5 minus x. |
Henderson Hasselbalch example .txt | The concentration of this guy increases by x, and the concentration of this guy decreases by x because this guy dissociates into this guy. So we get our hydronium concentration, we represent as x. Our pyruvate concentration we present as x because we begin with this concentration divide by since we begin with this amount of Peruvic acid and then some dissociates into the conjugate base, we say that it's 0.5 minus x. Now we approximate because the x is much smaller than 0.5 or 0.7 or 0.5. We approximate this to be 0.7. X divided by 0.5 equals our Ka. |
Henderson Hasselbalch example .txt | Now we approximate because the x is much smaller than 0.5 or 0.7 or 0.5. We approximate this to be 0.7. X divided by 0.5 equals our Ka. So equals 3.1 times ten negative three. We bring the 0.5
over. Then we divide by 0.7 and we get x equals 0.221. |
Henderson Hasselbalch example .txt | So equals 3.1 times ten negative three. We bring the 0.5
over. Then we divide by 0.7 and we get x equals 0.221. And notice that this is indeed much smaller than 0.5 or zero point 75. So our approximation was accurate. Now, to find a PH, we basically plug in the concentration into our PH into our negative log. |
Avogadro’s Number and Moles .txt | Today we're going to look at a very simple concept but one that's confused very often. We're going to look at avocado's number and moles. Now, avogadjo's number, just like any other number, is simply a number but it's a very large number. More specifically, it's 6.022 times ten to 23. So it's a very, very big number. Now, avogatro number is usually used in relation with moles. |
Avogadro’s Number and Moles .txt | More specifically, it's 6.022 times ten to 23. So it's a very, very big number. Now, avogatro number is usually used in relation with moles. Now, a mole which is represented by lowercase N is a group that consists of an avogadro's number of anything. Now, in the same way that a dozen represents a group of twelve, a mole represents a group of this many things. Now, we could have a dozen roses, a dozen eggs, a dozen chickens, a dozen chairs, cars, books, people. |
Avogadro’s Number and Moles .txt | Now, a mole which is represented by lowercase N is a group that consists of an avogadro's number of anything. Now, in the same way that a dozen represents a group of twelve, a mole represents a group of this many things. Now, we could have a dozen roses, a dozen eggs, a dozen chickens, a dozen chairs, cars, books, people. In the same way we can have a mole of anything. Now, the only thing is a mole is usually used for very small things. For example, we can talk about a mole of protons, a mole of electrons, a mole of atoms, a mole of molecules. |
Avogadro’s Number and Moles .txt | In the same way we can have a mole of anything. Now, the only thing is a mole is usually used for very small things. For example, we can talk about a mole of protons, a mole of electrons, a mole of atoms, a mole of molecules. Because these things are very very small it usually doesn't make sense to say a mole of people because that's impossible. We can't have a mole of people because we only have 7 billion people in the world. So moles are used for very small quantities of something. |
Avogadro’s Number and Moles .txt | Because these things are very very small it usually doesn't make sense to say a mole of people because that's impossible. We can't have a mole of people because we only have 7 billion people in the world. So moles are used for very small quantities of something. For example, we can talk about a mole of atoms which is 6.22 times ten to 23 atoms. But we can't really or it doesn't make sense to talk about a mole of books or a mole of x because I don't think we have this many eggs in the world. Maybe we do, but it's just a very large number. |
Avogadro’s Number and Moles .txt | For example, we can talk about a mole of atoms which is 6.22 times ten to 23 atoms. But we can't really or it doesn't make sense to talk about a mole of books or a mole of x because I don't think we have this many eggs in the world. Maybe we do, but it's just a very large number. Now, moles and a bogondo's number can be used to answer the following questions. For example how many molecules of water are in 20 grams of water? Now, to answer this question we have to first figure out how many moles are in 20 grams of water. |
Avogadro’s Number and Moles .txt | Now, moles and a bogondo's number can be used to answer the following questions. For example how many molecules of water are in 20 grams of water? Now, to answer this question we have to first figure out how many moles are in 20 grams of water. And then we multiply that by our avocado's number remembering that 1 mol of anything is this many atoms or molecules in our case. Now, let's take our amount in grams of water and divide it by our molecular weight of water which we can find on the periodic table which is 18 grams/mol. The way we found that is we simply added up the atomic weight of oxygen plus two atomic weights of H because we have two H atoms. |
Avogadro’s Number and Moles .txt | And then we multiply that by our avocado's number remembering that 1 mol of anything is this many atoms or molecules in our case. Now, let's take our amount in grams of water and divide it by our molecular weight of water which we can find on the periodic table which is 18 grams/mol. The way we found that is we simply added up the atomic weight of oxygen plus two atomic weights of H because we have two H atoms. So 16 for oxygen and two times one for H two gives us 18 grams/mol for a single water molecule. So 20 grams of water divided by 18 grams/mol we see that the grams cancel, the moles go on top and we get one point moles of water. So this means within our 20 grams of water there are one point eleven moles of water. |
Avogadro’s Number and Moles .txt | So 16 for oxygen and two times one for H two gives us 18 grams/mol for a single water molecule. So 20 grams of water divided by 18 grams/mol we see that the grams cancel, the moles go on top and we get one point moles of water. So this means within our 20 grams of water there are one point eleven moles of water. Now, we know that in 1 mol of anything there are this many molecules. So to find the number of molecules in one point eleven moles of water we simply multiply this number by Avogastro's number. So we get 6.22 times ten to the 23 atoms. |
Avogadro’s Number and Moles .txt | Now, we know that in 1 mol of anything there are this many molecules. So to find the number of molecules in one point eleven moles of water we simply multiply this number by Avogastro's number. So we get 6.22 times ten to the 23 atoms. Or actually, in our case, this should be molecules. Molecules per mole, times one point eleven moles of water. So the moles cancel and we're left with 6.68 times tens of 23 molecules of water. |
Avogadro’s Number and Moles .txt | Or actually, in our case, this should be molecules. Molecules per mole, times one point eleven moles of water. So the moles cancel and we're left with 6.68 times tens of 23 molecules of water. So this is how many molecules are found in 20 grams of water. Now, suppose I asked the question, how many atoms are found in 20 grams of water? Well, that means we take this number and multiply it by three. |
Avogadro’s Number and Moles .txt | So this is how many molecules are found in 20 grams of water. Now, suppose I asked the question, how many atoms are found in 20 grams of water? Well, that means we take this number and multiply it by three. Why? Well, this is a molecule, but an atom represents a single atom within this molecule. So we have one atom, two three atoms, one oxygen and two H atoms. |
Resonance Forms Example .txt | Now, this lecture we're going to do three examples shown here, and our goal will be to find as many resident forms as possible. So remember, whenever we're trying to do resonance and we're trying to find resonant forms, we're only moving electrons. The atoms never actually move. So let's redraw this molecule with the atoms being in the same exact place as shown here. So we have the H atom, the C, the H atom here. We have our N atom and the two H's here. |
Resonance Forms Example .txt | So let's redraw this molecule with the atoms being in the same exact place as shown here. So we have the H atom, the C, the H atom here. We have our N atom and the two H's here. So notice our atoms haven't actually moved. But what has happened? Well, what can we do here? |
Resonance Forms Example .txt | So notice our atoms haven't actually moved. But what has happened? Well, what can we do here? Well, look at this plus charge here. We don't like having charges. Charges means destabilization. |
Resonance Forms Example .txt | Well, look at this plus charge here. We don't like having charges. Charges means destabilization. We want to stabilize this lowest dot structure by removing this plus one charge. The way we can do that is basically take this double bond here, or take these two electrons, a pair of electrons, and use arrow formulasm to move these electrons here. Remember, an arrow, a double headed arrow simply means that a pair of electrons is being moved. |
Resonance Forms Example .txt | We want to stabilize this lowest dot structure by removing this plus one charge. The way we can do that is basically take this double bond here, or take these two electrons, a pair of electrons, and use arrow formulasm to move these electrons here. Remember, an arrow, a double headed arrow simply means that a pair of electrons is being moved. So these two electrons are being moved from here on to here. And so let's draw our two electrons here. Now, what has happened is this N now has five electrons, and that means this has been neutralized to a neutral charge. |
Resonance Forms Example .txt | So these two electrons are being moved from here on to here. And so let's draw our two electrons here. Now, what has happened is this N now has five electrons, and that means this has been neutralized to a neutral charge. But now this carbon has a positive charge. And so let's draw a plus charge here. And this concludes our resonance forms. |
Resonance Forms Example .txt | But now this carbon has a positive charge. And so let's draw a plus charge here. And this concludes our resonance forms. For this molecule, we have two major resonance forms. So let's go to part two. In part two, we have the following molecule, where we have two oxygen, carbon, carbon, and three HS. |
Resonance Forms Example .txt | For this molecule, we have two major resonance forms. So let's go to part two. In part two, we have the following molecule, where we have two oxygen, carbon, carbon, and three HS. So our goal will be to draw as many resonance forms or as many major resin forms as possible. So let's begin by moving electrons. Well, what's one way that we can move electrons here? |
Resonance Forms Example .txt | So our goal will be to draw as many resonance forms or as many major resin forms as possible. So let's begin by moving electrons. Well, what's one way that we can move electrons here? Well, we can basically take a pair of electrons here. We can create a double bond here, and these two electrons can be moved onto this oxygen, and we will create the following molecule or compound. Remember, our atoms have not actually moved, so our atoms remain the same. |
Resonance Forms Example .txt | Well, we can basically take a pair of electrons here. We can create a double bond here, and these two electrons can be moved onto this oxygen, and we will create the following molecule or compound. Remember, our atoms have not actually moved, so our atoms remain the same. What does move are electrons. So now this has essentially flipped. Now we have a negative charge on this upper oxygen and a neutral charge on the bottom. |
Resonance Forms Example .txt | What does move are electrons. So now this has essentially flipped. Now we have a negative charge on this upper oxygen and a neutral charge on the bottom. Well, what's another way that we can rearrange things? Well, we can surely take this bond here, the double bond, the pair of electrons, and move it onto this oxygen here. So let's do that. |
Resonance Forms Example .txt | Well, what's another way that we can rearrange things? Well, we can surely take this bond here, the double bond, the pair of electrons, and move it onto this oxygen here. So let's do that. So once again, keeping in mind that the resonant form represents an arrow that looks like this. And once again, no atoms are moved. Now, we have the following picture. |
Resonance Forms Example .txt | So once again, keeping in mind that the resonant form represents an arrow that looks like this. And once again, no atoms are moved. Now, we have the following picture. In this picture, we have now developed a minus on top, a minus on the bottom, and we have a plus one on the carbon. So now we have the following species. Now, notice here we have only one negative charge, one negative charge. |
Resonance Forms Example .txt | In this picture, we have now developed a minus on top, a minus on the bottom, and we have a plus one on the carbon. So now we have the following species. Now, notice here we have only one negative charge, one negative charge. But in this rest and form, we have two negative charges and a positive charge. Remember, whenever we have a lot of charge, a lot of charge stabilizes the structure. And that basically means that these two resonant forms will be more important than this resin form. |
Resonance Forms Example .txt | But in this rest and form, we have two negative charges and a positive charge. Remember, whenever we have a lot of charge, a lot of charge stabilizes the structure. And that basically means that these two resonant forms will be more important than this resin form. So these are our major resonant forms. Now let's jump to part three. In part three, we basically have a very similar structure to this, except now we have an H bonded to our oxygen, so we have a neutral atom. |
Resonance Forms Example .txt | So these are our major resonant forms. Now let's jump to part three. In part three, we basically have a very similar structure to this, except now we have an H bonded to our oxygen, so we have a neutral atom. So let's continue and let's draw what's one other way that we can draw this in terms of resonance? Well, we can surely take this pair of electron, place it here, and these electrons will move on to this oxygen, and we will develop the following lewis dot structure or resin four. Remember, our atoms don't actually move. |
Resonance Forms Example .txt | So let's continue and let's draw what's one other way that we can draw this in terms of resonance? Well, we can surely take this pair of electron, place it here, and these electrons will move on to this oxygen, and we will develop the following lewis dot structure or resin four. Remember, our atoms don't actually move. Atoms stay the same. But now we have the following picture. So here we have an H two. |
Resonance Forms Example .txt | Atoms stay the same. But now we have the following picture. So here we have an H two. Now, notice what happens. This has 12345. So this develops a plus one charge. |
Resonance Forms Example .txt | Now, notice what happens. This has 12345. So this develops a plus one charge. This develops a negative one charge. And so an overall net charge on this higher molecule is still zero, just like it is here. So let's draw one other resin form for this molecule or compound. |
Resonance Forms Example .txt | This develops a negative one charge. And so an overall net charge on this higher molecule is still zero, just like it is here. So let's draw one other resin form for this molecule or compound. What's another way we can draw it? Well, what if we just simply take this bond and move it back here? Well, let's try that. |
Resonance Forms Example .txt | What's another way we can draw it? Well, what if we just simply take this bond and move it back here? Well, let's try that. So we will have the following picture. Now, this carbon will develop a plus one charge. This will be neutral. |
Resonance Forms Example .txt | So we will have the following picture. Now, this carbon will develop a plus one charge. This will be neutral. Let's build our electrons here. And this guy here will have a negative charge. So we're going to have an overall net charge of zero. |
Resonance Forms Example .txt | Let's build our electrons here. And this guy here will have a negative charge. So we're going to have an overall net charge of zero. So what happened here? Well, here we have electrons that went onto here. So this concludes our major resonance structures. |
The pH scale .txt | And that's because pure water dissociates into H plus and hydroxide. So at any given time, we can measure the concentration of of this guy in terms of molar amount. Now, if you want to learn more about how H plus relates to acids and oh, Myers relates to bases, check out the link below. So what happens when we add some substance to our pure water, our PR substance? Well, for example, suppose we add HDL to our water. What happens? |
The pH scale .txt | So what happens when we add some substance to our pure water, our PR substance? Well, for example, suppose we add HDL to our water. What happens? Well, Htl dissociates its a Hydride ion and a chloride ion. So our concentration or amount in molar of H plus will increase because we have the H coming from water and the H coming from HDL. And so our concentration of our solution will increase. |
The pH scale .txt | Well, Htl dissociates its a Hydride ion and a chloride ion. So our concentration or amount in molar of H plus will increase because we have the H coming from water and the H coming from HDL. And so our concentration of our solution will increase. Now we can measure the concentrations in terms of molar amount, but the values we get can range from anywhere from ten to the negative 14 molar. That's a very small number. That's one divided by 100 trillion. |
The pH scale .txt | Now we can measure the concentrations in terms of molar amount, but the values we get can range from anywhere from ten to the negative 14 molar. That's a very small number. That's one divided by 100 trillion. And they could become as large as ten molar. Okay, so this becomes a problem. This is very inconvenient because say if you want to graph concentration in molar versus temperature, a graph would not be possible because our y scale would be just too big. |
The pH scale .txt | And they could become as large as ten molar. Okay, so this becomes a problem. This is very inconvenient because say if you want to graph concentration in molar versus temperature, a graph would not be possible because our y scale would be just too big. The range would be too big. So scientists came up with a way or a convenient way of expressing the concentration of our hydrogen ions in solution. And this convenient way is called a PH scale. |
The pH scale .txt | The range would be too big. So scientists came up with a way or a convenient way of expressing the concentration of our hydrogen ions in solution. And this convenient way is called a PH scale. The PH scale is defined by the following formula. PH of our solution is equal to negative log of the concentration of hydrogen ions. And that's equivalent to saying negative log of the concentration of hydronium ions. |
The pH scale .txt | The PH scale is defined by the following formula. PH of our solution is equal to negative log of the concentration of hydrogen ions. And that's equivalent to saying negative log of the concentration of hydronium ions. Because this guy and this guy are really one and the same. So let's see why logs are convenient. But first, let's see what logs are. |
The pH scale .txt | Because this guy and this guy are really one and the same. So let's see why logs are convenient. But first, let's see what logs are. Logs are simply another way of representing exponents. And if you want to find an exponent, you use logs. For example, suppose we're given this equation here. |
The pH scale .txt | Logs are simply another way of representing exponents. And if you want to find an exponent, you use logs. For example, suppose we're given this equation here. So ten to the negative four is equal to one over 10,000, which is another way of saying 0.1. Okay? So on a lock scale, this can be represented in the following way. |
The pH scale .txt | So ten to the negative four is equal to one over 10,000, which is another way of saying 0.1. Okay? So on a lock scale, this can be represented in the following way. Where this is our base, our result and our exponent. We get log base ten, log base ten. In the inside we get our result. |
The pH scale .txt | Where this is our base, our result and our exponent. We get log base ten, log base ten. In the inside we get our result. So 0.0001
and that equals to our exponent negative four. Here, to make this positive, I simply multiply both sides by negative one and I brought the negative to this side. And that's why this guy is positive. |
The pH scale .txt | So 0.0001
and that equals to our exponent negative four. Here, to make this positive, I simply multiply both sides by negative one and I brought the negative to this side. And that's why this guy is positive. So for example, suppose if I had the ten and I had this value, but this was my unknown, I could simply use this to find my exponent. That's why logs are convenient whenever you don't know our exponent, but you know the result and you know the base. You can use longs to find the exponent. |
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