CHEMISTRY COMMUNITY

taywebb

What would you do with a dead scientist? Just Barium.

taywebb

You can add them when it is a completed redox reaction where all of the electrons cancel out, but in that problem, the equations were not equivalent, so we could not add the E*'s together.

taywebb

You might have to label the axes of the graphs and the slope if given the reaction order.

taywebb

I believe that is the units for specific heat capacity because it has grams in it.

taywebb

They are both just different ways to reach an associated reaction mechanism or rate, but he said not to worry about steady-state, so I would just focus on pre-equilibrium problems. You will get the same answer both ways.

taywebb

After you have identified the reactant(s) in large excess, making them negligible in terms of the rate law. Are there any fundamental differences when composing a pseudo-first-order rate law vs. a normal first-order rate law?

taywebb

Because the outside environment is providing that heat directly, making this a naturally occurring reaction, no extra energy must be put in to make this reaction occur, so it is spontaneous.

taywebb

If your determined Q is less than K, then the reaction shifts forward.

taywebb

The actual rates would be equal, but not the rate constants

taywebb

I would assume no because catalysts increase a rate, so including it in the rate would not make sense

taywebb

First, you find k using the second order half-life equation, then you isolate t in the integrated rate law to solve for it. Because we already have the ratio of initial to final concentrations, you can use that to relate the two fractions together, making [A]t the same as [A]0. You can then subtract...

taywebb

I know we have to know how to derive the integrated rate laws, but will we have to solve for the half-life formulas as well? or will we just have to recognize which half-life formula is for which order?

taywebb

You would have to be given enough information to calculate it, specific units that go along with a specific order, or data to graph.

taywebb

From the practice problems and textbook, I think it is safe to assume they will give us A in a chart or just in the question of the problem.

taywebb

Should water be included in cell diagrams? If not, y?

taywebb

Is the oxidizing agent in a redox reaction always the couple that has a higher standard cell potential (being that it is more positive on the table)?

taywebb

Can anyone explain to me how they came up with the reduction and oxidation half-reactions for the cell diagram Pt(s)|H2(g)|HCl(aq)|Hg2Cl2(aq)|Hg(l)? I am confused at how they got Cl- as a separate component when it is not in the cell diagram and why the coefficient for H2(g) becomes 1/2 in the oxida...

taywebb

When calculating Gibbs free energy with the Delta G = -nFE equation and you are canceling units, is it necessary to change volts to J.C^-1 or can we keep the final answer in C.V?

taywebb

What will Gibbs free energy be when the reaction is at equilibrium?

taywebb

Do galvanic cells have to have a salt bridge?

taywebb

*When balancing redox reactions, is it necessary to balance the oxygen atoms before the hydrogen ones?

taywebb

For part c, the internal energy change of formation is the change in enthalpy of formation plus work. Why is this? I'm just confused on if the enthalpy of formation is replacing heat in this equation?

taywebb

If the problem does not note a pressure change can we assume that no change in pressure was made?

taywebb

When I fill in the table to find the [OH-] using the already given [H3O+] I keep getting 6.7x10^-14, but the solutions manual says the answer is 1.5x10^-14. I am just dividing 10^-14 by the given molarity (1.5). This is for the i part of the table. Can anyone explain what I am doing wrong?

taywebb

Does anyone know what actually changes K? I know changing the reaction and the temperature changes it, but does anything else change it?

taywebb

When increasing and decreasing partial pressure and concentration in a chemical equilibrium reaction, does the number of moles matter? or do they only matter when considering increasing or decreasing pressure on the whole system?

taywebb

Can anyone explain what I am doing wrong on this question: 29. A researcher fills a 1.00 L reaction vessel with 1.84 x 10-4 mol of BrCl gas and heats it to 500 K. At equilibrium, only 18.3 % of the BrCl gas remains. Calculate the equilibrium constant, assuming the following reaction is taking place....

taywebb

Here's what I could gather from looking at the solutions manual. We first have to recognize that the decomposition of X2 has an equilibrium equation of X2 <-> 2X, making the partial pressure ratio 1:2. Since the initial pressure is 0.10 bar, we must multiply it by the fraction of molecules that have...

taywebb

Clarity on how pressure vs. temperature affects the K value?

taywebb

Just for further clarification, when there are all gases, so you use Kp and partial pressure, the format for K would be Kp = and then use parenthesis with P and the molecule as the subscript, but for Kc and concentrations, the format for K would be Kc= and then use brackets?

taywebb

When an electron jumps from a lower energy level to a higher energy level does it gain or lose energy?

taywebb

I'm not sure where to put this so I'm putting it here.

Can anyone explain to me what a porpfyrin ligand is? Might be spelled wrong, but still confusing!

taywebb

If anyone has the same test #2 as me, I am confused on question 4c. It says to calculate the wavelength of the ejected electron, which I assumed would just be de Broglie (wavelength = h/mv). However, when I did that, I got the answer 3.64 x 10-10 m, but my TA wrote the 7.09 x 10-7 m as the write ans...

taywebb

A really simple way to think about this is just knowing that the angular quantum number (l) specifies the subshells. If only n is given you can just use the formula 2(n)^2 to determine the number of electrons. If l is given it can mean multiple things. If l = 0, it is the s orbital, which has 1 subs...

taywebb

Does H2Se have dipole-dipole forces as well as London dispersion forces?

taywebb

Can someone provide examples of compounds that are both amphoteric and amphiprotic and some that are one or the other? I understand what they are as defined terms, but some examples would be very helpful.

taywebb

Is the oxidation state the same as an oxidation number? or do the oxidation numbers of each element determine the compound's state?

taywebb

The book says the greater the electronegativity of A, the stronger the acid HA is, however, F if the most electronegative element, but the book also says that HF is the weakest acid. Can someone explain why?

taywebb

If I am making zinc nitrate what base do I use?

taywebb

Can someone differentiate when to use the Lewis acid definition of an acid vs. the Bronsted Lowry definition?

taywebb

I think there is a good probability of that showing up on the final mostly because he explicitly mentioned it in class. Also, it is really good information to know for checking your answer and comparing relative acidity.

taywebb

That helps! my only issue is if we are unsure of the Ka. Should we just go off of electronegativity and size of the atom? This still confuses me a little bit.

taywebb

Does anyone know if there are ways to figure out if the bond angles are not the standard 90, 109.5, 120, 180 and how we would denote on the final if they were more or less than that?

taywebb

Can anyone explain 2.45 to me? I understand how to get the lewis structure and what is a sigma and pi bond, but why is the C hybridization 2sp2 for a sigma bond and 2p for a pi bond?

taywebb

Can someone please explain to me the difference between hybridization of the central atom and the hybrid orbitals used by the central atom? (If there is a difference?)

taywebb

Does anyone know the lewis structure and geometric shape for SeF3+?

taywebb

When determining the number of sigma and pi bonds in a molecule, do you have to put them only for the most common resonance structure? (Referring to homework problem 2F #3 for the SO2 lewis structures)

taywebb

When describing how a hybrid orbital is oriented on the test, would it be necessary to put the degrees? (Ex: 120 degrees for trigonal planar)

taywebb

I understand why H is an exception to the octet rule, but can someone explain why Hi, Le, and Be are as well?

taywebb

Would the configuration of Ni as [Ar]3d84s2 be considered wrong on a test? Is it always preferred to fill the shell in order to make it more stable?

taywebb

This really cleared things up for me! Does this mean that zinc has 12 valence electrons?

taywebb

I'm still slightly confused. The solutions manual says that Mn has 7 valence electrons, but it is in the 7th group, so you're saying that it would have 9?

taywebb

Can anyone confirm my understanding of ionic and covalent bonding in regards to lewis structures? I believe that when you have an ion you use ionic bonding with the brackets and if the atoms are a neutral charge you use covalent bonding? Is there anything more specific to drawing these diagrams?

taywebb

I was confused about this as well. Thank you so much for the clarification! Does anyone know in what depth we need to know these bonds for the test? (just in terms of specific elements or molecules or even just sketching them out)

taywebb

So, based on this response, it would be No because the uncertainties of a large moving object are small?

taywebb

Yeah if you do the full problem out (by dividing Avogadro's number) you end up with 2.501 x 10^-19 J of energy as the work function, which after plugging it in to get the frequency of incident light gets you 6.78 x 10^14 Hz!

taywebb

Will I ever have a need to convert Hertz to Joules? or would they stay separate?

taywebb

Just double checking that if I had 1.1 of something rounding to 1 would be ok, even though it is more than 0.05?

taywebb

Can someone help me with a quick review of zeros in sig figs? I always get confused as to which zeros count as significant and which ones do not.

taywebb

Hi Guys!!
I definitely recommend making quizlets with basic SI units, conversions, and terms so that you can drill yourself on basic stuff before it gets too confusing!

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