CHEMISTRY COMMUNITY

hannahdaijo_4H

Why is standard cell potential sometimes equal to the difference between the standard potentials of the two electrodes and sometimes its the sum of the standard potentials of the cathode and the anodes?

hannahdaijo_4H

Are fast and slow steps directly related to the reaction constant? As in large reaction constants are indicative of a fast step and small reaction constants are indicative of slow steps?

hannahdaijo_4H

I don't completely understand what the chemical reaction for this problem would be. The solutions manual seems to use (unbalanced) Al + O2 --> AL (OH)3. Is OH the product because a given condition is that the reaction is in basic solution?

hannahdaijo_4H

Or is this just a variation of the Nernst equation?

hannahdaijo_4H

Can anyone possibly explain how the solutions manual arrives at 0.06V = Enot - (0.025693/1)(2.303)log(H+)? particularly the numbers plugged in for (RT/nF)lnH+

hannahdaijo_4H

Should we be familiar with the process of corrosion, particularly due to exposure to water and oxygen, and corrosion prevention for the final?

hannahdaijo_4H

Can the change in enthalpy be used to determine whether the forward reaction or reverse reaction is favored? (as in 4.45 7th edition)

hannahdaijo_4H

Can the change in enthalpy be used to determine whether the forward reaction or reverse reaction is favored? (as in 4.45 7th edition)

hannahdaijo_4H

For part c of this problem, where you have to solve for the final volume of the pressure constant cylinder including excess reactant, why wouldn't you calculate the volume using the excess reactant in addition to the volume for all of the reactants used in the reaction?

hannahdaijo_4H

The negative log of the H+ concentration essentially gives you the new "neutral" pH at the second temperature. So as was said above, pH 7 > pH x, so pH 7 is basic

hannahdaijo_4H

Why is it that, when identifying oxidized and reduced elements and determining their oxidation numbers, sometimes the oxidation numbers are given for homonuclear diatomic molecules and sometimes its given for just the singular element? Like in 6K.1 (a), the oxidation number for Cr is 6+ (which is wh...

hannahdaijo_4H

How much of outline 4 will be on this test (if any at all)? Is it just the material having to do with Gibbs free energy or the content prior to that as well?

hannahdaijo_4H

According to Lavelle's lecture, E not is the standard reduction potential and gives voltage difference between two standard electrodes which are always the same, as in these values are empirically predetermined and can be found on a table. Ecell is the cell potential but I don't think it can be empi...

hannahdaijo_4H

What exactly is the difference between rotational and vibrational energy? If a molecule has one does it also always have the other?

hannahdaijo_4H

Should we memorize the conversion factor for atm L to joules?

hannahdaijo_4H

If a process is reversible, does that mean that it's also essentially always in equilibrium?

hannahdaijo_4H

How do you determine an element's most stable form (as it pertains to standard enthalpy of formation)?

hannahdaijo_4H

What dictates what form water products will take? The combustion equations given in 4D.3 of the 7th Edition textbook give one equation where the water product is gas and one where it is liquid.

hannahdaijo_4H

So if the chemical equilibrium equation consists only of gases and K isn't specified as Kc or Kp, you'd most likely use P subscripts?

hannahdaijo_4H

This question gives a chemical equation and asks you to write the expression for K, and the solutions manual uses P subscript molecular formula rather than just the molecular formula and concentrations. Are these two forms interchangeable when the question doesn't specifically ask for concentrations...

hannahdaijo_4H

What exactly is the difference between the reaction quotient and the equilibrium constant?

hannahdaijo_4H

Should we know how to calculate Ka/Kb, pKa/pKb, or just understand them conceptually with relation to acid and base strength?

hannahdaijo_4H

For question 6B.5c, why do you multiply M of Ba(OH)2 by 2?

hannahdaijo_4H

(With regard to weak acids and bases) why is it that for proton transfer reactions such as those in J.17, some of the atoms in the weak acid or base are not included in the chemical equation? I think I remember prof explaining this in lecture, but I don't exactly remember the explanation.

hannahdaijo_4H

So if we can memorize strong acids/bases, is it necessary to memorize common weak acids/bases? Or, like the original poster said, can we just assume that anything now on the list of strong acids/bases is a weak acid/base?

hannahdaijo_4H

With problems using ammonia, when would ammonia be a Bronsted acid versus a Bronsted base? Is it just a given that when NH3 reacts with water it acts as a base and becomes NH4-?

hannahdaijo_4H

For oxyacids, what is it about molecules with more oxygen atoms that make the molecules more acidic?

hannahdaijo_4H

When identifying bond types in a molecule, would you always use the lowest energy lewis structure? Because for this question, the solutions manual essentially gives two answers, one for a lewis structure with resonance and one for without, and the two would yield different answers about the number o...

hannahdaijo_4H

For the lewis structure of (CH3)2Be, where beryllium is connecting the two methyl groups, does that connecting atom need to have a complete octet or not/is Be just an exception to the rule where it can exist with only four valence electrons?

hannahdaijo_4H

So the only way to identify whether a molecule is trans or cis is by the molecule's systematic name rather than merely by the molecular formula?

hannahdaijo_4H

Could someone help explain trans/cis molecules and what dictates which structure a molecule is? The book (7th edition) uses dichloroethene (C2H2Cl2) as an example of trans and cis molecules.

hannahdaijo_4H

Like the other posters said, Dr. Lavelle said to memorize basic VSEPR model bond angles and the general reasons behind them. But in addition he said to understand conceptually the bond angles for molecules with lone pairs on the central atom.

hannahdaijo_4H

When drawing resonance structures, is it necessary to label the atoms numerically like the solutions manual does? (e.g. the solution for 2B.17 7th edition)

hannahdaijo_4H

Do sigma and pi bonds directly correspond with bond length AND bond energy?

hannahdaijo_4H

Do axial bond angles only exist in conjunction with equatorial bond angles?

hannahdaijo_4H

But in the same vein, why is the answer for 2E.1 (7th ed) that there MAY be lone pairs on the central atom rather than there are none?

hannahdaijo_4H

What do you mean by "an extra ten electrons?" I thought that the total amount of electrons an expanded octet could hold was twelve?

hannahdaijo_4H

The concept is sort of similar to how as you move across a period on the periodic table the atomic radius becomes shorter because the charge is greater so there's more attraction between the valence shell and the nucleus. Similarly, the more bonds there are, the shorter the distance between atoms

hannahdaijo_4H

I know that relative to dipole-dipole and hydrogen bond IMFs, London dispersion forces are the weakest. But since LDFs depend on charge, is there ever an instance where an LDF is stronger than a dipole-dipole force?

hannahdaijo_4H

I know p-orbitals have one nodal plane (I think), but do d-orbitals always have two nodal planes or does it depend on the orientation of planes?

hannahdaijo_4H

Is the mass of an electron something we should memorize?

hannahdaijo_4H

The textbook says, "...the intensity of radiation is an indication of the number of photons present, whereas E = hv is a measure of the energy of each individual photon." But in 1B. 9 (of the 7th edition), the question asks for the number of photons that can be generated and how many moles...

hannahdaijo_4H

I think he said it was experimentally verifiable because the electron does exhibit detectable wavelength properties, whereas in the prior problem the car (?) didn't have any detectable wavelength properties because the wavelength was too small.

hannahdaijo_4H

Personally I prefer handwriting everything, even if it does get messy, because I find that when I physically write out notes or problems, it processes and sticks much better than typing something out and then going back to try to look at that. Plus, since most of the stuff in lecture is also in the ...

hannahdaijo_4H

I think that essentially, the shorter the wavelength, the higher the frequency of the wave, hence the higher energy and vice versa.

hannahdaijo_4H

When I was first taught to balance chemical reactions, we were told to draw out basic symbols to represent each atom/molecule (like circles or x's) so that you could more tangibly recognize when the equation is balanced. So that may help, but also like Jillian said, starting with the least represent...

hannahdaijo_4H

I think someone asked this in class and the professor essentially said, for now at least, we'll be given the formula's alongside the names and do not need to memorize polyatomic ions.

hannahdaijo_4H

If you assume a 100g sample, it's then easier to analyze the percent composition factors and work through the problem quantitatively and qualitatively.

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