CHEMISTRY COMMUNITY

Lauryn Shinno 2H

On the lecture slide, it said "rate written as a function of concentration often referred to as rate law". Does that mean that a rate law is the same as a differential rate law?

Lauryn Shinno 2H

I know Dr. Lavelle went over these briefly in class, but what are they, and do we need to know how to draw them?

Lauryn Shinno 2H

When do you leave the equilibrium constants and when do you substitute k/k'? For example, in the one Dr. Lavelle did in lecture, he got rate=2k2*K*[NO]^2*[O2]. He then replaced K with k1/k1' to get rate=2k2*k1/k1'*[NO]^2*[O2]. Do you always replace K or are there times where you have to leave it in?

Lauryn Shinno 2H

Can we always assume that microscopic reversibility is being applied?

Lauryn Shinno 2H

In lecture, Dr. Lavelle went over how to find the rate constant for reactions with multiple reactants. At the end, he said that k[A]^N*[B]0^M*[C]0^L=k'[A]. Could you do this with B and C as well? ex. k[A]0^N*[B]^M*[C]0^L=k'[B]

Lauryn Shinno 2H

Will we need to be able to set up graphs to find the order of a reaction on the final? If so, how do you do it?

Lauryn Shinno 2H

Given NiSO4(aq), how do you know that the SO4^2- ion will not oxidize?

Lauryn Shinno 2H

For part a, I keep getting 2649868 for Q, but the answer in the manual is 10^6. Is the reaction quotient always going to be rounded to a multiple of 10?

Lauryn Shinno 2H

In part a, to find Q, the book multiplies the reactant concentration of H+(0.075 M) by the reactant partial pressure of H2 (1 bar) divided by the product of the product concentration of H+ (1 M) multiplied by the product partial pressure of H2 (1 bar). Why are we allowed to multiply concentration by...

Lauryn Shinno 2H

When do you include platinum in the cell diagram?

Lauryn Shinno 2H

I understand cell diagrams go anode||cathode, but what about the order of the anode ions and cathode ions? I've heard to write it reactants|products and to put it in order depending on the phase with the solids on the outside. However, in 14.13 part b, the cell diagram is Pt(s)|I^-(aq)|I2(s)||Ce^4+(...

Lauryn Shinno 2H

The question asks you to calculate the standard reaction Gibbs free energy for a. 2Ce^4+(aq)+3I^-(aq)—>2Ce^3+(aq)+I3^-(aq). How do you find the moles of electrons transferred? Also, I understand that Ce^4+ is getting reduced, but how is 3I^- getting oxidized? It's oxidation number doesn't change.

Lauryn Shinno 2H

I think if it is a constant temperature you can assume that it is a reversible reaction because irreversible reactions have changing temperatures.

Lauryn Shinno 2H

Reversible is expansion/compression against constant pressure, while irreversible is infinitesimal steps of expansion/compression against a changing pressure. Therefore, irreversible does more work, but does not actually happen in real life.

Lauryn Shinno 2H

I think if you used the Cp value 5/2*R you would get a value around 20.785. The value they gave us during the exam was 20.81, so I think if you used either you would get around the same answer.

Lauryn Shinno 2H

Why are all the units J.K^-1.mol^-1? For example, in part d, I did [(3 mol)*(151.0 J.K^-1.mol^-1)+(1mol)*(82.59 J.K^-1.mol^-1)]-[(4 mol)*(143.1 J.K^-1.mol^-1)] which equals -36.81 J.K^-1.mol^-1. However, since you're multiplying mol by J.K^-1.mol^-1, shouldn't the units just be J.K^-1?

Lauryn Shinno 2H

The answer key uses delta S=nR(ln(T2/T1)). When can you use this instead of delta S=cln(T2/T1)?

Lauryn Shinno 2H

For 9.13 in the 6th edition, it says "During the test of an internal combustion engine, 3.00 L of nitrogen gas at 18.5 degrees C was compressed suddenly and irreversibly to 0.5 L by driving in a piston. In the process, the temperature of the gas increased to 28.1 degrees C. Assume ideal behavio...

Lauryn Shinno 2H

What does it mean when it says that the calorimeter is calibrated (for example 8.23 and 8.25 in 6th edition)?

Lauryn Shinno 2H

The textbook switches between giving the answer in kJ and J. Does it matter which one I use?

Lauryn Shinno 2H

For 8.57 in the 6th edition, it gives us the standard enthalpies of combustion. In the solution manual, it writes balanced combustion equations for the given reaction and then adds the reactions together to find the final enthalpy. Do we need to do this? I literally added the given enthalpies of com...

Lauryn Shinno 2H

I think it is the enthalpy when all reactants and products are in their standard state at 1 atm. The standard state for a gas is 1 atm, the standard state for a solution is 1 M, and the standard state for a pure liquid or solid is the pure liquid or solid.

Lauryn Shinno 2H

Exothermic reactions favor the formation of products and give off heat. Endothermic reactions favor the formation of reactants and require heat.

Lauryn Shinno 2H

Catalysts don't affect Kc because they only make reactions faster. They don't change the concentrations of the reactants or products.

Lauryn Shinno 2H

On Outline 1, it says we have to be able to identify reactions where the ideal gas law can be used as an approximation. What does this mean?

Lauryn Shinno 2H

On outline 1 it mentions biological examples, such as ATP hydrolysis and osmotic pressure. What should we know about these?

Lauryn Shinno 2H

Can someone explain arylamines, alkylamines, methyl-, and ethyl-? Also, do we have to know these?

Lauryn Shinno 2H

Why are solids not included in the ICE table?

Lauryn Shinno 2H

What does it mean when it asks if Cl2 or F2 is thermodynamically more stable relative to its atoms? How do you know?

Lauryn Shinno 2H

If given the initial concentration/pressure of the reactant(s), are the initial concentrations/pressures of the products always going to be 0 in the ICE table?

Lauryn Shinno 2H

You can use bond length when referring to an A-H bond like HBr and HCl. However, HBrO2 and HClO2 have the same A-H bond being broken (O-H). Therefore, you have to use electronegativity to determine their strengths instead.

Lauryn Shinno 2H

It means that there is a difference in electronegativity between the two atoms the bond is connecting.

Lauryn Shinno 2H

My TA's notes have Iron (Ferrate), Copper (Cuprate), Lead (Plumbate), Silver (Argentate), Gold (Aurate), and Tin (Stannate). I would know those, just to be safe.

Lauryn Shinno 2H

Given lewis structures, how can you tell if one acid is stronger than another?

Lauryn Shinno 2H

I think amphoteric oxides have both basic and acidic character. For example, H20 can be both an acid and a base, meaning it can donate or accept electrons. They are found diagonally on the periodic table between the metals and the nonmetals near the metalloids.

Lauryn Shinno 2H

Hi in the 6th edition of the textbook, toolbox 17.1 says "If there is an ambiguity in which atom is linked to the metal atom, then kE is added to the name in parentheses, where E denotes the connecting atoms (and k is kappa):[Fe(NCS)(OH2)5]2+ thiocyanato(kN)pentaaqua(III) iron [Fe(NCS)(OH2)5]2+...

Lauryn Shinno 2H

The homework question says: Noting that the bond angle of an sp3 hybridized atom is 109.5 degrees and that of an sp2 hybridized atom is 120 degrees, do you expect the bond angle between two hybrid orbitals to increase or decrease as the s-character of the hybrids is increased? Can someone explain wh...

Lauryn Shinno 2H

How do you determine where each sigma and pi bond goes?

Lauryn Shinno 2H

Does everything have dipole-dipole forces unless atoms of the same element are arranged symmetrically around the central atom?

Lauryn Shinno 2H

For molecules, such as CH2Cl2, that can be drawn in multiple ways, how do you know which one is correct? For example, you could put the two hydrogens and two chlorines next to each other around the central carbon or you could alternate them. This would affect whether the molecule is polar or not, so...

Lauryn Shinno 2H

How do you represent double bonds using the VSEPR method with wedges?

Lauryn Shinno 2H

No, I believe Dr. Lavelle said this is the only non SI unit we should know.

Lauryn Shinno 2H

Hi, in class Dr. Lavelle brought up the equation Ep is proportional to alpha1*alpha2/r^6. What does this mean?

Lauryn Shinno 2H

When you get to period 3, even though the periodic table makes it look like 4s should go before 3d, it goes afterwards because the 3d orbital has less energy than 4s after 4s is filled. However, when doing the diagram using Aufbau's rule, 4s goes before 3d.

Lauryn Shinno 2H

Hi my TA mentioned that we might have to know how to draw the different orbitals like 3px, 3py, and 3pz. Can someone explain how to do this?

Lauryn Shinno 2H

Is this the heisenberg uncertainty principle?

Lauryn Shinno 2H

Hi can someone explain how you know if an element is a metal, metalloid, and nonmetals? Also, do we have to know this?

Lauryn Shinno 2H

Can anyone explain why carbon has a higher electron affinity than nitrogen?

Lauryn Shinno 2H

The problem asks you to place the ions in order of increasing ionic radius: S^2-, Cl^-, P^3-. I understand that ionic radii decrease from left to right across a period, but I don't get what the exponents do. How do they affect the size of the radius?

Lauryn Shinno 2H

It asks which element is predicted to have the following ground-state electron configuration: [Rn]7s^2 6d^2. First, why is the 7s before 6d? Also, the answer is Thorium, which I thought was in the f-block? How does that work?

Lauryn Shinno 2H

For Chapter 2, are there sections I can skip? For example, Atomic Radius, Ionic Radius, Ionization Energy, Electron Affinity, Inert-Pair Effect, Diagonal Relationships, General Properties of the Elements, etc.

Lauryn Shinno 2H

I believe Professor Lavelle said that we just need to understand what it is, and problems where you would have to solve a Schrodinger Equation are too complicated for this course.

Lauryn Shinno 2H

The question asks what is the ground-state electron configuration expected for each of the following elements: (a) silver; (b) beryllium; (c) antimony; (d) gallium; (e) tungsten; (f) iodine? I feel like we didn't go over this in class, and I was wondering if we would have to know this for test two.

Lauryn Shinno 2H

In the equation E=hv, I know E stands for energy, but specifically what energy? Like threshold energy or energy of the photons?

Lauryn Shinno 2H

How do you solve this? Molybdenum metal must absorb radiation with a minimum frequency of 1.09 x 10^15 s-1 before it can emit an electron from its surface. b. If molybdenum is irradiated with 194 nm light, what is the maximum possible KE of the emitted electrons?

Lauryn Shinno 2H

How do you solve this? Light hits a sodium metal surface and the velocity of the ejected electron is 6.61x10^5 m.s-1. The work function for sodium is 150.6 KJ.mol-1. a. What is the KE of the ejected electron? b. How much energy is required to remove an electron from one sodium atom? c. What is the f...

Lauryn Shinno 2H

For part c, I got NH6PO4, which is correct. However, the answer says NH6PO4 or [NH4][H2PO4]. How do you convert NH6PO4 into [NH4][H2PO4] and do we have to know this?

Lauryn Shinno 2H

I think in class, he said you could use either. However, sometimes it makes more sense to use one instead of the other. For example, when you're doing an experiment, you would normally measure 16.2 mL rather than 0.0162 L. Both answers would be correct though.

Lauryn Shinno 2H

I think the TAs said you have until Sunday to complete your posts, so you still have time to get your 3 points. Otherwise, yes, I believe it counts as 0 points for week 1 if you don't do them.

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