CHEMISTRY COMMUNITY

rkang00

Is having a catalyst in the rate law allowed? Or is it not, like intermediates aren't?

rkang00

For the electrochem worksheet 8d, why don't we include the OH- in the cell diagram?

rkang00

Does the rate constant k of the exp determined overall rate law equal to the rate-determining step's rate constant? What about when we assume pre-equilibrium?

rkang00

The height of the waves depend on Ea, don't they? (higher = slower, lower = faster)

rkang00

Do we include H+/OH- in cell diagrams ONLY if they're present in the balanced redox rxn? I'm a bit confused as to when to put them.

rkang00

Do catalysts not show up the overall rxn, but can start out in individual mechanism steps - get consumed - then get re-formed? What are the key features that define a catalyst in a rxn mechanism?

rkang00

When drawing profiles, how do we draw the troughs of multiple mechanisms? Don't we have to know whether each step is exo/endothermic, and do we have to know something about stability?

rkang00

Is the 'unique' of the unique rate indicating that every single rxn has its very own unique rate, like a human fingerprint?

rkang00

So if a reactant's order is zero, its concentration will change linearly regardless of its concentration?

rkang00

I'm not sure how to explain what an intermediate is; is it a species that forms during mechanism, but is not in the products nor reactants of the overall rxn? Is there more to this definition?

rkang00

If there are H+ or OH- or water left over from balancing half-rxns, do we have to list them in the cell diagram as well?

rkang00

Why do we not use commas to separate solids undissolved in solution? 7th edition 6L 7c uses a single line instead of a comma; is it because the solid dissolved is not part of the electrode?

rkang00

How do we know which rxns to use for neutralization redox rxns? I find it hard to tell which ones I should use. Is there a way to solve these problems in general? I think if I can just know what rxns to use, I could do the rest.

rkang00

How do we know when solids are undissolved in solutions but not acting as electrodes? the I2 is an example, and the 7th edition, 6L #7a is another problem too.

rkang00

What goes across, if anything does at all, the porous disk of a concentration cell? Do inert anions go across to the more positive side to keep the cell neutral?

rkang00

Does anyone know what the half-rxns are for this problem and how to solve it?

rkang00

Can someone explain how to balance rxns like these with only one species on reactants or products side?

rkang00

How is the delta G and the standard state delta G (with degree sign) differ? Is the standard state delta G constant for a specific rxn while delta G (w/o the degree) could be different?

rkang00

How does entropy change with volume, pressure, and temperature changes? Basically: what happens to entropy if one of the three factors increases/decreases?

rkang00

If a system is isolated with + amount of energy, will it there be no change even after time passes?

rkang00

It says that a way to continue a rxn without adding more reactant is to remove the product, since more reactants will be consumed to form products to minimize the effects of the loss. Isn't this an indefinite way to continue a rxn? At some point you'll run out of reactants to consume, even with Le C...

rkang00

Then is the 5/2R and 3/2R for monoatomic ideal gases a given rule?

rkang00

Can someone explain how the cis and trans compounds have different orientations? cis has 12 and trans has 3, and I'm not understanding how we're supposed to obtain the number of orientations. Is it because cis has the two red atoms next to each other while the trans must have them across each other?

rkang00

Typically if a system is compressed, is the sign for work + and - for expansion?
If so, what's the reason?

rkang00

Does anyone see an error in this problem? I don’t know where the K came from, we only had Celcius to work with.

rkang00

When putting signs for bond enthalpies, is it usually + on the reactants side and - on the products sign?

rkang00

For phase change enthalpies, do we have to change signs for them as well depending on which side of the rxn they're on?

rkang00

I know that K changes with temperature but how does it change? Does K increase with temperature or are they inversely related? Or does it depend on case by case?

rkang00

I've been seeing multiple formulas for converting kp to kc - are these just multiple forms of a single formula? Or is there a universal formula for converting kp to kc in any given problem?

rkang00

In a problem where we have to calculate the pH of a solution of a weak acid + its salt, do we have to take the cations into account? for example the problem in class professor Lavelle told us - the thing with nitrous acid + potassium nitrite. Do we have to take the potassium ions into account? Or do...

rkang00

When we try to solve for the change in concentration (x), I guess the only way to solve it is through using the quadratic equation?

rkang00

Does anyone know how this problem is to be done?

rkang00

I think that's when you increase the heat of the rxn. Does anyone know what happens when the temp is lowered?

rkang00

Is there a place to not use the ideal gas formula? I heard somewhere that ideal gases may not apply to every case.

rkang00

What’s the difference between K, Kc, and Kp? The textbook seems like it’s considering K and Kp one and the same.
Also, what does the C in Kc mean?

rkang00

I know for cations of the same row we compare charge and same column we compare atomic radii, but if we're comparing cations of different rows and columns which takes precedence over the other? I had this part of the test wrong.

rkang00

What about in formulas? I'm not sure when to use H2O or OH2.

rkang00

If water is a ligand, how do we write it? There seems to be two ways of writing it: H2O and OH2, but I'm not clear on which style applies to which scenario.

rkang00

It says in the textbook that anionic ligands that end in -ide, -ate, -ite change their endings to -ido, -ato, ito respectively. I don't think this was covered in class; is this something different? When do we use this for?

rkang00

Then can an acid/base be considered Bronsted AND Lewis at the same time?

rkang00

When forming pi or sigma bonds, does it matter which orbitals are used? As in, can only an s & p orbital form sigma and p&p form pi bonds? (it's just a theoretical example)

rkang00

If a molecule's dipole moments cancel out, does this mean that structures with resonance have no net dipole movement? I think that was the case for neutral sulfite (SO3); it has resonance but the real molecule in reality has the bond length equal to the average of the bond lengths of the resonance s...

rkang00

The lecture notes tell us that there's usually no spacing when naming coordination compounds. Does this mean that writing with spaces in a test will result in loss of points? Also, we add an O to the end of an anion only if it's within the coordination sphere, right?

rkang00

How does the number of resonance structures determine bond length? Do we end up having more bond lengths to average out?

rkang00

How many bond angles in a seesaw-shaped structure are 90 degrees wide? I know the structure has both 90 and 120 degree angles but I'm not sure of how many of each are there.

rkang00

If a test asks us to find the number sigma and pi bonds of a molecule that has a resonance structure I assume we have to find the numbers of bonds for each structure to get full credit?

rkang00

Is taking 14B and 14BL finals on the same day doable? I'm just asking out of curiosity, please let me know!

rkang00

On 7th edition, 2F.15 there's a question about s-character. What's s-character of the hybrid orbitals? Apparently it affects bond angles.

rkang00

How does a sigma or pi bond being able to/unable to rotate influence bonding? Why is it important to note?

rkang00

If dipole moments that cancel each other result in nonpolarity does this mean that symmetric atoms and molecules are generally nonpolar?

rkang00

Are VSEPR shapes formed so that there's maximum repulsion between atoms?

rkang00

Why are the bond energy signs all negative? They're all attractive forces that result from subtraction but I don't get why they're results of subtraction and why they're negative.

rkang00

How do you know that an atom has only one additional bond in addition to an octet? is the number of remaining orbitals the way to determine it? (take bromate for example - how do you know it's just 5 bonds on bromine and not 6)

rkang00

How are the bond lengths of resonant atoms (nitrate, nitrite) the same when the resonant structures have different bond lengths?

rkang00

Wait, so we have to get the mass of each molecule separately b/c the mass of N2 (14.0067x2) is the molar mass, not the mass of the individual N2 molecule? I also got that question wrong, so I was confused about it

rkang00

So we just have to follow the periodic table in numerical order? That's not what I remembered - or did I hear something wrong?

rkang00

Does this mean that generally 4s orbitals will lose electrons before 3d electrons are lost?

rkang00

How would the size of isoelectronic atoms compare? for example which would be bigger: Ne or Na+? Would this be dependent on nuclear charge?

rkang00

Okay but when do you use the equation for? I never fully understood where to use it (if anyone knows if it explains in the textbook let me know)

rkang00

Are De Broglie wavelengths used for large particles? How do we know when to use the De Broglie equation to get a wavelength? It's confusing when to use the De Broglie or the E=hv equation.

rkang00

For one of the d-orbitals (I think dx) why was the orbital a ring again? The rest are in cones so I don't get why dx is a ring

rkang00

It might have to do with the principal quantum number and orbital number. There's another number that I can't recall right now but they're in the textbook - the notations are n, l, ml.

rkang00

Why do we have to add a negative sign though? is it just an indication of a difference in energy levels?

rkang00

If an electron is ejected with zero kinetic energy, what would it look like in real life? How would the electron actually move? Also, if kinetic energy is zero I guess this means that the work function (threshold energy) and hv are equal to each other?

rkang00

In the lecture, there's a constant reference to 'work function'. What is that, is that the threshold energy with a circle-with-a-line-through-it as a symbol?

rkang00

in a spectroscopy experiment, there are three components: E = hv, work function, and Ek. If the electron has no kinetic energy, does it mean that the electron is detached but doesn't move? How would it look like in real life?

rkang00

Ok so let's say the figures given in a problem are 250.0ml, .0350M, 33g. So would the final answer have to be in 2 sig figs, but we don't round during calculations?

rkang00

Can molecules be calculated in moles as well? I thought moles only applied to atoms - or am I mistaken?

rkang00

Just wondering, what's the difference between titrations and dilutions? I swear I learned it in high school but I just can't remember - I often get confused between the two.

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