CHEMISTRY COMMUNITY

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The two terms have the same meaning. The professor uses them interchangeably.

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Think about equations where we have included the reaction coefficient, Q. Particularly: delta G = delta G prime + RTlnQ

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Intensive properties are true of a substance regardless of its mass; extensive properties depend on the condition of its mass.

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All of the units must be the same since we are supposed to add and subtract them without any other conversions.

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b) If we are talking about something inside a coil, then it is probably in a closed system since it is not exposed to anything necessarily. I am not a refrigerator repair-person so I cannot say this for sure, although it would be my best guess. d) The same principle applies: the gas is within someth...

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I believe we can assume that all reactions are reversible unless stated otherwise. I have read that extensively on this forum. One way you can tell if it is irreversible is if the reaction occurs instantly or at a near-instantaneous rate.

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Happy Heart Day!

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If something has a concentration or a partial-pressure, then I think it is safe to include it on the K expression.

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The w term is positive when something is responsible for doing work on the gas in question.

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Is it fair to call it an isolated system, though? I thought you can transfer heat to it. That involves some form of non-isolation, no?

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I do not recall hearing the term "isometric" in the lectures, although I may have missed it. Based on its components, I would assume that it has something to do with sameness of measurements.

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"Spontaneously" means that a decrease in entropy in the universe will never be favored. I see this as evidence that the total volume of the universe is constantly expanding, therefore increasing its entropy.

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Adiabats occur rather instantaneously. This quick time frame disallows the transfer of heat since this takes time.

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Non-state functions depend on the path taken by reactants in various forms. For example, the total work exerted by a system relies on all of the work done at every point in the process. This result is not net but cumulative.

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Wait but if Q=K then wouldn't the reaction be non-spontaneous?

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Consider what happens in the universe (system + surroundings) as a whole when the exchange occurs.

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Someone said you can finish all of the HW and Chem Comm questions to pass this class. Basically, as long as you try your best, you can pass this class. I would recommend trying on tests and quizzes since that might bump up your score, but otherwise, you can still pass. I hope this helps; I myself ha...

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Talking to TAs and whatnot at office hours helps! I hear the discussion section review sessions offer relevant questions as well. Do your best and let come what may!

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The most-ordered ones have the lowest delta S values.

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What is strange is that I did not have to convert kPa to atm for this one to be right. Does that mean that that does not matter? The R constant does not have atmospheric units, after all.

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The heat capacity lets you calculate how much energy is gained by that specific amount of water depending on the temperature change.

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Irreversible reactions occur rather instantly.

I also have a question: is there energy that is irreplaceably lost during an irreversible reaction? What is the significance of that distinction?

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It primarily tells us about the spontaneity of the reaction, although it does not say anything about the rate of the reaction. Like what has already been said, this can also tell us if the system is in energetic equilibrium.

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I think they must be synchronous. I would be surprised if they are not recorded, though, since time zones might introduce issues.

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It depends on the sign of delta G. I think it is important to note that the magnitude of delta G does not affect the reaction rate.

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delta S for vaporization is just the heat necessary to vaporize the given amount of material over the temperature that it vaporizes.

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If heat capacity is below zero, then transferring energy to it would cause its temperature to decrease. Perhaps there is a substance that, the more you apply heat to it, the more its heat energy is applied to different forms of energy.

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I think residual energy can be thought of as energy that exists after the main reaction occurs. It includes heat and other various forms of energy such as kinetic energy and the like.

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The difference is implied in the equation. Adding RTln(Q) to the one with the degree sign accounts for the difference. It probably involves temperature and concentrations.

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q and w are not necessarily 0 as well, they just occur in a manner such that U does not change from its original state. deltaU = 0 implies that there is not a temperature change in the system.

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It is spontaneous if it results in a less-energetic system. If Gibbs Free Energy for a reaction is negative, meaning that the system loses GFE, then the reaction is "favorable" or "spontaneous"

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Constants like that are often inferred from graphs. If you plot the PV and NT values on a graph, the result will be a constant value that equals the value that you stated. Since Boltzmann found this out, he named it after himself, as he is entitled but not required to do.

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I would refer to the equation: U = 3/2 * n * R * T. If any of the parameters in the equation change, then there is a corresponding change in the internal energy. Also, U = w + q. If w or q changes, then U changes.

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Try plugging those pressure values into the reaction quotient, Q. The procedure is similar to that used in the acids/bases equilibrium problems from earlier in the quarter.

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Abiabats occur quickly and involve zero heat transfer. Recall that isobaric processes often occur gradually for the pressure on both ends to remain the same, although the heat transferred is non-zero. Isotherms have the same temperature, although heat can be transferred.

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I think it's due to symmetry. If you flip a symmetrical molecule around, then it occupies the same position if you flip it around.

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n represents moles, but it all depends on the units of C. If C requires mass in grams, then n should be in grams.

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This is really helpful! It is interesting to see the differences that different constants introduce to the equations.

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Anything that is path-dependent is NOT a state function. If it can be graphed and produces an integral that depends on the area under its curve, then it is NOT a state function. This includes WORK.

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14BL offers a considerable amount of work considering that it is a 3-unit course (at least, relative to 14B), but the content is relevant to the chemical industry. To my surprise, nothing from 14B is in 14BL: the two courses cover completely separate content. That being said, chemistry is chemistry.

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If q is not reversible then there must have been heating lost during the transfer of energy from an external source to the subject gas. Ideal gases retain all heat transferred to them, apparently.

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Usually, if I make a silly mistake, then I probably was not paying attention to the problem that much. Making a list of things you need to focus on right before taking the test has helped me keep those things in mind while taking the test. Writing things down helps!

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Well there are many parameters that are involved. It often depends on what the problem asks you. But if you look at changes in volume, you can infer a few things about it. For example, if the volume increases, there are more possible configurations of molecules so the entropy increases. delta S woul...

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Yes, the same rules apply. Make sure that the units are all the same when you solve the problem! I didn't notice it the first time I went through it.

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I like watching videos about topics until I feel like I understand it well enough to work on problems without looking at my notes.

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We ca"n""n"ot ig"n"ore "n" as lo"n"g as it is i"n" a"n" equatio"n"

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I have a question: where did the equation S = C*ln(T2/T1) come from? I don't recall that being presented in the lectures. It is the equation that must be used for this problem. I think I have answered my own question. For changing temperatures, delta S = nCln(T2/T1) is applicable. The problem accou...

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I have a question: where did the equation S = C*ln(T2/T1) come from? I don't recall that being presented in the lectures. It is the equation that must be used for this problem.

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If the question is asking about vaporization, then we know that the liquid must rise in temperature until it reaches 100 degrees Celcius. At that point, as it vaporizes, all of the energy being inputted into it is increasing its entropy. You can follow the same logic to determine the change in entro...

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When is Midterm 2 for non-international students, exactly?

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The 1atm specification is given for gaseous substances, specifically.

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Do you all think that the chemicals in mosquito spray are harmful enough to justify not using them? Would spraying chemicals all over yourself be better than a bite or two? Curious to know what you all think. Parasites, of course, are also an issue for consideration.

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pH refers to the concentration of H+ in a solution.

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If I get a 50% in a chemistry class then you all need to keep me far, far, far, far away from the nearest box of chemicals!

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I usually start from the inside-out when naming a LOOOOOONG molecule like the ones we've encountered in the lectures and notes. There's also a lot of inductive reasoning involved when determining the charge number for metal cations.

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I believe the reason involves the total formal charges of all of the atoms in the compound.

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The difference is in the terminologies. Reactions with Bronsted acids/bases are defined in terms of proton transmission, while reactions with Lewis acids/bases are defined in terms of their exchange of electron pairs.

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Yep. If an acid is a monoprotic acid, then it is only able to offer one hydrogen ion to a solution.

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Dear Doctor Lavelle:

Thank you, Doctor Lavelle!

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I believe you would need to take the other molecules into consideration. I usually go about determining the charge of a molecule using the formal-charge analysis method for each atom and then adding the results.

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The suffix "-protic" refers to the number of protons a molecule has. We use this term for compounds like H3PO4 and other similar molecules.

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Well if you have a diagram and there are more OH- molecules in a solution than there are H+ molecules, then you know the solution is more basic, and vice versa. pH is affected in increments of whole numbers based on base-10 changes/differences in the concentrations of the molecules. I wouldn't like ...

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As long as you understand the fundamental properties of logarithms, you're fine. You just need to apply them!

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I think the exact number depends on the properties of the compound, but in general, the number is less than 109.5º

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What matters in the end, my friend, is the relative concentrations of H+ and OH-, so if you get molecules that are slightly stronger at providing H+ molecules over OH- molecules, then the solution should overall be acidic.

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I scream at the top of my lungs and then calmly enter the room

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The oxygens would not be able to accept H's probably because those are the sites that are reserved for hydrogen bonding when there are other nucleic acids present (particularly adenine). And yes, the nitrogen sites should be amphiprotic.

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As a chemist myself, I must say that the temperature does indeed influence the pH of the solution. At high temperatures, the volume of a given solution will expand. This causes the concentrations of solutes to decrease even though the amount of solute remains the same; the opposite occurs at low te...

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It depends on whether or not the conjugate acid or the conjugate base from the salt is the component of a strong acid or a strong base and whether the resulting conjugate substances are stronger than each other or not. For example, if a salt has a nitrate in it, then it is likely going to cause the ...

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The compounds with oxygen must be considered with a different thought process than the ones without oxygen. In the former group, the H is bonded to the oxygen and not the halogen, so the electronegativities of the halogens must be considered as they influence electron distribution and therefore the ...

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I'm gonna make MEMES baybeeEEEEEE!!!!

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I think polydentate ligands are compounds that can offer multiple atoms within themselves to bond with a metal atom or cation. They have many atoms that have electron pairs or distributions that can bond to the central atom.

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https://link.springer.com/content/pdf/1 ... 769517.pdf

Here's an article I found using Google Scholar about Element 112.

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Ka denotes the relativities of products and reactants while considering the dissociation of strong or weak acids. The stronger the acid, the stronger the dissociation, and the products are more present. This results in a high Ka value for strong acids, and a low Ka value for weak acids. pKa is just ...

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As a chemist myself, I must say that the temperature does indeed influence the pH of the solution. At high temperatures, the volume of a given solution will expand. This causes the concentrations of solutes to decrease even though the amount of solute remains the same; the opposite occurs at low tem...

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I would assume that we would not need to be familiar with the complex terminology. But I would recommend becoming familiar with the prefixes for the molecules that possess multiple ligands, as well as knowing what the term "dentate" refers to. If I am not mistaken, the term is used to deno...

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You can determine whether or not the bond angles are larger and smaller than the ones listed with quantitative certainty by noting if the given molecule has unpaired electrons. If it does, then the bond angles are smaller and are more compressed than the fully-bonded models.

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The term "delocalization" refers to the resonance possibilities of the double bond. If the double bond can exist between multiple sets of atoms, then, in reality, the double bond exists between all of them at different times: the double bond may be between two atoms at one moment, and then...

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No need to fear: I am here!

The important thing to keep in mind when answer #20 is that there are some elements on the periodic table which are able to possess more electrons than the octet rule states that it can possess. Is As one of the elements? If you answer this question, all else will follow.

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This one is rather straightforward. All you are doing is adding carbon atoms to your initial structure. This does not change the hydrogen arrangements in the rudimentary lewis structure as you are only inserting carbon atoms.

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Each of the structures for the molecule you wrote is a resonance structure for that compound. Some of the carbon atoms in that compound may bond to each other in a variety of ways: these ways include single, double, and triple bonds. You may also arrange them in a ring structure if that is possible ...

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1) Use the percentage values given to calculate the empirical formula of the compound, and then use the molar mass number to see if the molecular formula is any different. To do this, divide the percentage values by the molar masses of their corresponding atoms as if those values were true whole num...

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The electronegativities cancel when the opposing dipoles align symmetrically and are of the same strengths. Think of it as adding and subtracting integers and seeing if the value is zero or not. But in this case, they must also be properly oriented.

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Ask yourself the following: if you could rotate the molecule around one linear axis, which set of molecules would align with the axis?

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Knowing the values, though, might help you determine whether or not a small hydrogen-bonding molecule can have higher values of attraction than a larger non-hydrogen bonding molecule. The numbers say that hydrogen bonds are about 10x stronger than a typical force of disperison. H-bonds are not only ...

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You shouldn't be worried if you think you've done enough to prepare for the class; that's what I tell myself when I get concerned about not doing well in a class. If you're worried then you should change your habits: study more, study more effectively, and talk to the TAs if you can.

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We know that the covalent character of an atom decreases as it becomes more polarizable; this is directly correlated with the number of electrons that an atom has. As this number increases, an atom exhibits more ionic traits and can form stronger bonds.

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The bigger the atom, the more it is capable of forming a highly-attractive bond with another atom. The professor gave us the following equation last week to express this correlation: Ep (interaction potential energy) = - (a1)(a2) / r^6; the a's represent the "polarizability" of an atom whi...

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The professor said that we don't have to apply quantum numbers to "n" values greater than four for this class. Someone else should verify that, though.

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Y'all should check out "Night Court"

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The compound with the smaller Group 17 element is might be more soluble in water because it would take fewer water molecules to surround and dissolve the compound compared to the other one. You should also keep in mind that there is an equation that states that larger atoms are capable of forming st...

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Hello!

The second midterm will be covering many more topics than the first midterm, so in terms of content, there should be a lot more to study for!

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The octet rule does not necessarily apply here because Group 13 elements are able to attain stable formal charge configurations through other means. One example of this is the configuration of BF3, in which boron only needs a total of 6 electrons to be stable.

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One of the only times the professor mentioned anything about diagonals was when he said that fluorine is the most electronegative element and that it is in the right uppermost corner of the periodic table. I do not believe that we need to be familiar with the specifics of any diagonal trends though.

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The configuration for Palladium is an exception to the general trend. The reason why it has a full d-orbital is that the atom is in a more stable state when the d-orbital is full as opposed to when it has a full 5s2.

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Remember: acids tend to donate protons and accept electrons, and bases tend to accept protons and donate electrons. Keeping this in mind, look at the charges of the molecules and determine whether or not they are suitable to either accept or donate protons!

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Quantum states refer to the mathematical models that chemists use to chart the probability that an electron can be found orbiting an atom in a specific manner. The professor gave a few lectures in which he talked about the purpose of quantum numbers in the process of figuring out the characteristics...

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A good place to start might be the consideration of the trend that the least-electronegative atom in a molecule is likely to be found at the center of that molecule. If you are going off of a written molecular formula, try using this principle while arranging the groups of molecules given in bracket...

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I would say that it depends on the molecule/enzyme that is being denatured. Since H+ and OH- are entities that are both charged, it would make sense for both of them to be capable of denaturing compounds that have charged/polar areas.

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Perhaps you can play around with the arrangement of the atoms in the molecule with a particular emphasis on the central atom.

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