CHEMISTRY COMMUNITY

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Heat capacity is the energy required to raise the temperature of a substance by 1 degree C, and it is an extensive property. Specific heat capacity is the energy required to raise one gram of substance by 1 degree C, and is an intensive property. The difference lies in that one in extensive and one...

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heat capacity is q=c(delta t) specific heat capacity is q=mc(delta t) basically specific heat capacity is specific to your sample because it incorporates mass. To clarify, these are the equations you would use to find q using heat capacity or specific heat capacity. The actual heat capacity and spe...

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An example would be the expansion of a balloon. Say the pressure outside the balloon decreased, the volume of the balloon would increase as it expanded. However, it is still a closed system because the balloon never actually lost any matter, it just reacted to outside conditions.

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It could be either conceptual, such as just describing what it means, or he could make integrate it into an actual problem to test if we really understand what it entails. Question 5 dealt with an adiabatic process in a problem, so I'd say it's definitely fair game for the final.

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Agreed, during 14A with Lavelle his final was pretty evenly split. Also, the TA's mentioned that all material will be covered equally on the final (to an extent, as obviously we can't cover every single topic in one test).

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To clarify, if volume is constant but Pext is changing, would work still be done by the system? Such as if your lungs had 3L of air in them at 1 atm, then after you dive down under water the pressure is 2 atm but your lungs still remain at 3L. Could we just use w=-nRTln(P1/P2) to find work, or is it...

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You would use w=-Pext(deltaV) when pressure is constant, and w=-nRTln(V2/V1) when pressure is changing as well.

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How come the answer is 4390 C and not 4395 C, if they originally started at 25 C?

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Search up "helium melting exothermic" on google, and Dr. Lavelle's Chemistry Community explanation is the first answer to come up. It's really long and complicated so I won't attempt to copy it down, but it should help out!

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We don't actually need to know how much the internal energy changed, as it will be proportional to the change in volume. Because is it a gas, P1V1=P2V2. We will only ever have one unknown, so we can figure out how much the internal pressure has changed based on delta V.

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I don't think so, we never went over it in class and it isn't on the syllabus. At most I think we'd just need to know that they exist.

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Ok, so we essentially just look for the lewis base in the reaction. Thank you!

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What is a nucleophile, and how would we determine what molecule is acting as one if we are given an equation?

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Scott Chin_1E wrote:Does Wmax usually occur when the system is at equilibrium?

No, at equilibrium Delta G and Ecell are equal to zero, and therefore work at equilibrium would be equal to zero. This makes sense, as at equilibrium there would be no electrons flowing between the anode and the cathode.

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You can also remember that in a galvanic cell, the electrons flow from left to right. Since the oxidation is the process of losing electrons, it must occur in the left side of the cell, which is the anode.

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Conceptually, it is an intensive property because the unit of voltage is V, which is the amount of joules consumed per charge of one coulomb (J/C). No matter how big the size of the sample or cell you have, the energy consumed by per coulomb will be the same as it's just a ratio.

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The redox reaction is occurring in a basic (alkaline) environment, as we can tell by the OH- in the reaction. KOH (aq) is a very common alkaline solution and is the solution present in the anode.

Hope this helps!

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I don't think we would ever have a situation when both the reactant and the product are in solid form, as Dr. Lavelle stated that anytime something gets oxidized it will turn into an aqueous solution. For the purpose of our course I believe we only need to know when both the reactant and product are...

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We would use an inert conductor, such as platinum, when one of the half reactions have no conducting solids in the reactants or products. An example of this would be Fe 3+ (aq) going to fe 2+ (aq). Because there is no solid for the electrons to go through, we need to place one there that can conduct...

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Can you explain why delta S universe can be zero during a reversible process, but is always positive for a spontaneous process? I thought it was always positive no matter what.

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Agree with Matthew above, work is definitely done in an irreversible process, it's just much smaller as the changes in the volume are much smaller than those in a reversible process, and occurs much more slowly.

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Like Dr. Lavelle said, sometimes you do not need to fully calculate delta G in order to determine if the reaction is spontaneous. Often if you know delta h and delta s then you can tell automatically if a reaction is spontaneous. For example, if delta h is positive and delta s is negative, we know t...

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Actually I think K can be any value, its just a ratio of products to reactants at equilibrium. When K>1 its favored to have more products than reactants at equilibrium, and visa versa when K<1. K=1 is really rare because you'd have to have exactly the same concentration of products and reactants.

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How come the system isn't necessarily at equilibrium when delta G naught is zero?

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What exactly is G, and how does it differ from delta G in terms of what we use it for?

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I don't think the specific heat capacities of NO and NO2 are the same, in fact I believe that of NO is slightly larger. This is due to the fact that even though NO2 has a larger molar heat capacity, one gram of NO is a higher percentage of its molar mass that 1 gram of NO2 is of its molar mass.

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Does the energy that gets transferred into heat always have to be equal to or greater than the energy converted into work, or can either be larger than the other?

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So if the difference is that reversible reactions occur at equilibrium, what makes a reaction that occurs at non-equilibrium irreversible?

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So in number 7, would it be endothermic because it is absorbing heat?

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How come with Hess' Law we subtract the enthalpies of the reactants from that of the products, but when calculating bond enthalpies we essentially subtract the products from the reactants?

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How do we distinguish between an isolated system and a closed system?

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For a value of l greater than 4, what would the orbital be? Are there orbitals beyond f orbitals that we don't cover in this class, or is it simply that any l that is 5 or above is considered an f orbital?

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In a case where the central atom is bonded to two outer atoms via double bonds, would the hybridization of the central atom be sp, because there are only two sites where the atoms are bonded, or sp3, because there are four bonds?

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So does that mean that all acids are Lewis acids, but not all acids are Bronsted acids? And the same for bases.

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Do delocalized pi bonds only occur in a molecule with a 6-carbon ring, or can they occur any time there are overlapping p orbitals?

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Then how come HF is a stronger base than HOH, even though fluorine is more electronegative than oxygen? Does the strength of an acid increase as we go across the periodic table?

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No, as long as all of the ligands are present and bonded to the metal, it doesn't matter where they are on the lewis structure.

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Wouldn't we only use ferrate if the compound is an anion? I think if the compound is neutral or a cation then we use iron, correct?

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Is there any way to tell if a molecule is a chelating complex just by looking at the molecular formula? Or do we need to see the Lewis structure to be sure?

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For a molecule that has 2sp^2 hybridization like in C2H4 shown above, what is the difference between that and sp^2 hybridization? What does the first coefficient actually represent?

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I know you can have multiple pi bonds, but can you have multiple sigma bonds? In all of our examples it seems that there is only ever one sigma bond.

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In order to determine if the bond itself is polar, we look at the difference in electronegativity of the elements involved along with the characteristics of these elements (does it dissolve in water, etc.). If asked if the entire molecule is polar or nonpolar, that is when we look at if the molecule...

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It was actually SiO2, but nevertheless it is still polar, as the difference in electronegativity was greater than 1.5.

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How would we know when to call it trigonal pyramidal and when to call it tetrahedral?

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Is there any way for us to tell exactly what magnetic quantum number an electron would have within an orbital without doing an experiment? Will we ever be asked which magnetic quantum number an electron has?

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Then how come even when the 4s orbitals are filled first, they still have a higher energy than the 3d orbital, hence why we write 3d before 4s?

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What about with Chromium and Copper, when the 4s orbital isn't completely filled and an electron gets transferred to the 3d orbital? Do we still list the 3d orbitals ahead of the 4s?

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Also, is the only thing that would change in different equations for different elements the Rydberg constant? Or would the entire makeup of the quantum equation for that element be different from what we learned for hydrogen?

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Are we only going to learn the quantum equation for Hydrogen, or are we expected to know it for others, such as carbon an oxygen?

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What is the difference between molarity and molality?

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In a multistep problem, should we use sig figs with every step, or only when it comes to the final answer? Will we be penalized if we use more than the amount of sig figs in intermediate steps but have the correct amount for the final answer?

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