CHEMISTRY COMMUNITY

Nicholas Chin 1G

Nope, it's the same rate equation.

Nicholas Chin 1G

It's a reaction that does not depend on the amount of the reactant. For example, a saturated catalyst reaction, where the rate is limited by the number of open catalysts, is a zero order reaction because increasing the reactant won't do anything.

Nicholas Chin 1G

The delta S total is the delta S of the system plus surroundings.

Nicholas Chin 1G

In some cases, standard E will be zero, so this equation can be used to find Ecell in concentration cells.

Nicholas Chin 1G

I believe it's because the anode proceeds backwards from the standard form of half reactions (i.e. Fe2+ +2 e- -> Fe(s)).

Nicholas Chin 1G

THANK YOU DR. LAVELLE!!!

Dr. Lavelle is genuinely one of the most entertaining and funny professors I've had in a while. I really like how pleased he looks whenever he turns into DJ Lavelle and bops to the music.

Nicholas Chin 1G

It should be released by Sunday, and it's timed for the same 3 hours that we would've been given. I'm sure he'll release more details tomorrow regarding the specific details.

Nicholas Chin 1G

I'm guessing it's still going to be 180 just because that would mess up his scaling if he made it worth that little points.

Nicholas Chin 1G

At least for Ben, he left his in his mailbox in Young Hall.

Nicholas Chin 1G

The one with ln has been rearranged so that you can create a graph of certain values that will result in a straight line, something that can't be done with the previous equation.

Nicholas Chin 1G

You can use the appendix to look at the E values for the two half reactions. Since the equation for Ecell is E(c) = E(cath) - E(anode), then you can determine which reaction is cathode and which one is anode.

Nicholas Chin 1G

Catalysts lower the activation energy, meaning particles that are involved in collisions don't need as much energy to make the reaction go forward, increasing k.

Nicholas Chin 1G

The slope will also give you a different constant value depending on the order of the reaction.

Nicholas Chin 1G

I think it's safe to assume it might just be free response, just like normal.

Nicholas Chin 1G

You can probably just scan it and send it to him, it sounds like this is all gonna be pretty informal.

Nicholas Chin 1G

R = Nk, where N is avogadro's constant and k is boltzmann's constant.

Nicholas Chin 1G

I think it's just to note that it's not the original k that you're dealing with: it includes other constants.

Nicholas Chin 1G

You first balance the oxygens by adding H2O on whatever side needs oxygen. Then you balance the extra hydrogens by adding H+ on the other side. If the reaction occurs in a basic solution, then you add to both sides the same amount of OH- as H+ you added.

Nicholas Chin 1G

Generally, if the reactant energy is higher than the product energy, the reaction is exothermic, and vice versa for endothermic.

Nicholas Chin 1G

I believe that in the context of electrolytic reactions, the anode is always the one that corrodes.

Nicholas Chin 1G

I believe it's based on the E value for the half reactions. The more negative half reaction is the anode and the more positive half reaction is the cathode.

Nicholas Chin 1G

I think if there isn't a salt bridge, there needs to be a porous membrane for ions to diffuse through in order to maintain the charge balance.

Nicholas Chin 1G

Probably negative free energy means positive E(cell) potential. There's also an equation I believe that you should know, it's on the equation sheet.

Nicholas Chin 1G

I think because electrochemistry reactions generally only go forward, since they have a positive E(cell) value.

Nicholas Chin 1G

It's to maintain the charge balance between the anode and the cathode. As electrons move, the ions in solution have to move the opposite direction to counterbalance the difference in charge.

Nicholas Chin 1G

K is a constant for a reaction that tells you the concentrations of products and reactants needed for the reaction to be at equilibrium. Q is not a constant, and can be calculated (and is different) at any point in a reaction. The value of Q compared to K tells you which way the reaction is going at...

Nicholas Chin 1G

These are the fractions that you put in front of the ideal gas constant to get a Cp and Cv value, which are used for constant pressure and constant volume respectively. You can use this to calculate the heat put into a gas and its corresponding temperature change.

Nicholas Chin 1G

Delta H is enthalpy, which is the total heat change in a system. At constant pressures, it can be used interchangeably with q.

Nicholas Chin 1G

An extensive property depends on the amount (i.e. mass, volume). An intensive property is the same regardless how much you have (i.e. density, specific heat capacity).

Nicholas Chin 1G

The c in q = C * delta T is the heat capacity, measured in Joules per Kelvin. The C in q = m * c* delta T is specific heat capacity, which is measured in Joules per Kelvin gram. The difference is that the first c has different values depending on the amount of some material you have, while the secon...

Nicholas Chin 1G

Essentially, the second law of thermodynamics says that the entropy of the universe always increases. Thus, in biology, when there's a reaction that lowers the entropy of the universe (like anabolic metabolism), it must be accompanied or powered by something that increases the entropy more than the ...

Nicholas Chin 1G

Because humans are open systems, so air and other things can freely leave our bodies, making the pressure in our bodies equal to the pressure outside.

Nicholas Chin 1G

Degeneracy is used to help calculate the entropy of a system, which can be used to calculate the Gibbs free energy of a reaction or system.

Nicholas Chin 1G

It's basically a way to determine the positional entropy (disorder) of a system, which does not take into account the temperature.

Nicholas Chin 1G

I believe the water that is produced is water vapor, since for combustion to occur the temperature would have to be most likely above 100 C.

Nicholas Chin 1G

I'm not sure it's the only way, but it's probably the most reliable way.

Nicholas Chin 1G

Autoprotolysis is not just the transfer of a H+ ion between an acid and a base, it's the transfer of an H+ between two identical molecules, one that can act as an acid and a base (like H2O). If you then take the equilibrium constant of the equation 2 H2O -> OH- + H30+, you'll get Kw = [OH-][H30+].

Nicholas Chin 1G

Yes, that is what he meant. If you heat an ice cube very slowly while taking its temperature, you'll notice that when the ice cube transitions to a liquid, the temperature of the sample is staying around 0 degrees, not increasing.

Nicholas Chin 1G

Work is a way of transferring energy, while heat is a form of energy.

Nicholas Chin 1G

Probably just wait and see if he talks about it.

Nicholas Chin 1G

This rule is also only applied if K is a small value (<10^-3).

Nicholas Chin 1G

The R constant is the universal gas constant, and the reason there are different values for it is because the units can vary, from atmospheres to barrs.

Nicholas Chin 1G

The Henderson Hasselbalch Equation is an equation that uses the pKa and concentration of weak acid & conjugate base to quickly determine the pH, without having to go through the ICE table and quadratics.

Nicholas Chin 1G

Temperature changes the equilibrium constant, so make sure you have the right K constant if looking at a chart that gives you multiple.

Nicholas Chin 1G

Strong acids and bases are just things you're going to have to memorize. Generally, strong bases are group 1 and group 2 metals with an OH group, meaning their conjugate ions are the metals. Strong acids are HBr, HCl, HI, HNO3, HClO4, HSO4, and their conjugate ions would just be those without the H.

Nicholas Chin 1G

We get to gases later on so you don't really need to worry about it right now.

Nicholas Chin 1G

Ruby Richter 2L wrote:So basically you're just multiplying the molarity times RT which gives you P?

Yea that's all you're doing.

Nicholas Chin 1G

You determine it by comparing the equilibrium constant (K) with the reaction quotient (Q). If Q is less than K, then there are less products so the reaction is going to the right. If Q is greater than K, then there are more products so the reaction is going to the left. In this case, it doesn't matt...

Nicholas Chin 1G

Calculating Q is the same as calculating for K, which means you include all aqueous solutions and gases, and disregard liquids/solids.

Nicholas Chin 1G

Thank you! I was looking for this answer!

Nicholas Chin 1G

The polyatomic ones.

Nicholas Chin 1G

Spectator ions are generally just group 1 cations or halogens. Since they are stable, they don't want to react.

Nicholas Chin 1G

Salts of weak bases and STRONG acids produce acidic solutions because the conjugate base of the acid is a very weak base while the conjugate acid of the weak base is relatively stronger, so it makes the solution its in acidic.

Nicholas Chin 1G

It's just a real life example of an acidic reaction that he went over in class, and may show up on the test. He just went over the reactions involved.

Nicholas Chin 1G

Yes, it's just because strong acids dissociate more, so there will be more H+ present in a strong acid solution than a weak acid one even if they have the same concentration.

Nicholas Chin 1G

Polydentate refers to ligands that have multiple donor atoms and therefore can bind to a metal at multiple sites. Its significance can be seen in its biological aspects such as heme complexes and other things like that.

Nicholas Chin 1G

I think if you are given a chemical formula, it will have the bracket notation, so you will know it's a chelate complex. As for drawing the right structure, I guess you just follow the lewis structure rules and hope you get it right.

Nicholas Chin 1G

Weak acids and bases will not fully dissociate when in an aqueous solution, strong acids and bases will.

Nicholas Chin 1G

Probably just go to review sessions because those usually have the same concepts as what appear on the exam.

Nicholas Chin 1G

They're basically all referring to the same thing, but just approach it differently. Lewis acids are molecules that accept an electron pair, while lewis bases donate an electron pair. Bronsted acids donate a proton, while Bronsted bases accept a proton. Conjugate acids and bases are a little differe...

Nicholas Chin 1G

I think it has to do with the fact water is less relevant than bisoxalato.

Nicholas Chin 1G

Sigma bonds have better overlap because their tips touch. Pi bonds are side to side interactions so there is less overlap.

Nicholas Chin 1G

Hybridization occurs to stabilize the energy of bonding orbitals. Single electrons can still form a bond, so they don't need to be hybridized.

Nicholas Chin 1G

Cisplatin, the drug used to stop DNA replication, is a square planar.

Nicholas Chin 1G

No, you need to know all of them I'm pretty sure.

Nicholas Chin 1G

Probably roughly the same amount as test 1.

Nicholas Chin 1G

He said that we will never be graded on drawing Lewis structures according to VSEPR model. All you have to do is write out the bond angle and shape and stuff.

Nicholas Chin 1G

Electrostatic potential is just a fancy way of saying an electric field. Polar molecules are one's that have a more negative end and positive end. So polar molecules, with their negative and positive ends, "interact" with an electric field. That is to say that the presence of an electric f...

Nicholas Chin 1G

For this problem, you basically have to determine which molecules are polar and which aren't. So looking at the four molecules, the molecules that aren't symmetric are going to be the polar molecules, and thus have "important" dipole-dipole interactions. In this case, it would be (b) and (...

Nicholas Chin 1G

We know that the bond angles are going to be distorted to slightly less than 120 and 90 degrees, but since we can't actually know how much, we usually say that there the bond angles are 90 and 120. In my discussion session, my TA said there would then be a followup question that asks if there is ang...

Nicholas Chin 1G

Vapor pressure is lower with molecules with strong intermolecular forces. Since H2O has hydrogen bonding, it will have a lower vapor pressure than the other molecule.

Nicholas Chin 1G

I'm not too sure but I think you just look at whether the molecule is polar (aka does it have dipoles that are not cancelled), whether the molecule can form hydrogen bonds, and other type of interactions that he went over in class.

Nicholas Chin 1G

Yea I think for the most part people take it in separate quarters just because it's easier that way.

Nicholas Chin 1G

These two molecules are actually ones that he went over in class the other day. Because CH3(CH2)3CH3 is going to be more rectangular/spread out than the spherical shape of C(CH3)4, the dipole moments for the first molecule will be stronger because separate molecules will be able to get closer to eac...

Nicholas Chin 1G

Because nitrogen has 3 parallel spin electrons in separate orbitals in the 2p subshell, while Oxygen has 3 parallel spin electrons and one antiparallel electron in the same orbital. Because of electron-electron repulsion and the fact that having a half-full 2p subshell is more stable, it is easier (...

Nicholas Chin 1G

It becomes less confusing if you think of bonds as being on a spectrum rather than just either ionic or covalent. Bonds that are considered "covalent" still have ionic characteristics, which is why we talk about how electrons are not equally shared in covalent bonds. Bonds that are conside...

Nicholas Chin 1G

It's a covalent bond where one atom brings both electrons and one atom accepts both.

Nicholas Chin 1G

Coordinate covalent bonds are covalent bonds where one atom brings both electrons and one accepts electrons. Lewis acids (H+) accept two electrons to form a bond, while lewis bases donates both.

Nicholas Chin 1G

Electronegativity is a measure of the tendency of an atom to attract electrons. It has the same trend on the periodic table as atomic radius.

Nicholas Chin 1G

a) 5, b) 4 c) 7 d) 3

Nicholas Chin 1G

Assume that you always apply the octet for any bond except for the exceptions (P, S, Cl)

Nicholas Chin 1G

So just like the d-orbital and s-orbital, the 5s comes first, but after 2 electrons are in the 5s the 4f is actually placed before when you're writing out the electron configuration. You don't really need to worry about it because he said we wouldn't be tested on it.

Nicholas Chin 1G

It's because having 10 electrons in the d orbital and 1 in the s orbital is actually more stable than 9 electrons in the d orbital and 2 in the s orbital. This also applies for 5 electrons in the d orbital.

Nicholas Chin 1G

You can also use formal charge to see if the atom would be more stable with an expanded octet.

Nicholas Chin 1G

It should be the arrows indicated between the various structures because we haven't really learned orgo yet.

Nicholas Chin 1G

Yea, he specifically said in lecture that we will never be tested on this.

Nicholas Chin 1G

In what types of circumstances would it be necessary for us to convert J into these units? Can someone give a sample problem or example? I don't think there's any instance in chemistry where you would have to break down these units and use them, but in physics it can be useful to know these units t...

Nicholas Chin 1G

In addition to Brianna Becerra 1F, you would typically use this equation when being asked for the minimum uncertainty in speed/velocity when given the physical constraints or vice versa. Is minimum uncertainty something different or when we solve this equation we get minimum uncertainty? Minimum un...

Nicholas Chin 1G

We have not learned about a quantum number Z, but the letter Z can represent the nuclear charge of an atom.

Nicholas Chin 1G

Because in the case of the s and p orbitals, the difference between the energy of the orbitals are too great to make a difference when you have a full p orbital vs a full s orbital. In the 3d orbital vs the 4s orbital, the energies are very similar, so the fullness of the subshell makes a difference.

Nicholas Chin 1G

The formula was derived empirically, meaning they looked at the data they collected from performing a spectroscopic experiment with hydrogen and developed a formula that fit the data they had. This means that it's only applicable to hydrogen.

Nicholas Chin 1G

Pretty sure we have to know how to do it at some point, but we're not expected to do it right now.

Nicholas Chin 1G

When I asked my TA they said that we are expected to memorize the names of cations and anions, but I'm not sure if we have to memorize the acids yet since that's something we will cover later.

Nicholas Chin 1G · Re: Weekly Posts Pretty sure it's before 11:59 pm on Sunday

Pretty sure it's before 11:59 pm on Sunday

Nicholas Chin 1G

Although it's usually good practice to go to 4 for mass percentage composition, it actually depends on how many sig figs you have for the mass of elements you use. For example, if you use 12.01 for Carbon, you have 4. But if you use 12.0107, you have 6.

Nicholas Chin 1G

Molarity does not have the units of moles. It has the units mol/L, which is denoted as M in some cases.

Nicholas Chin 1G

If the given mass of the molecular formula is the g/mol, yes the empirical formula is wrong.

Nicholas Chin 1G

In regards to rounding for significant figures, you count out how many figures your answer should have first. So if your sig figs were 1, and your answer was 5.454545, you would only take the 5 in the ones place. Next, you would look one number to the right. You then apply the golden rule of roundin...

Nicholas Chin 1G

So if the wording is "double the volume 90 times," that means you have to multiply 10 mL by 2 90 times. An easy way to do this is just 10 mL * 2^90, which effectively "doubles the volume 90 times" since you multiply by 2 90 times. Now you have a volume initial (10 mL), a molarity...

Nicholas Chin 1G

It's not really a formula, but you would use Avogadro's number multiplied by the diameter of an Ag atom, since 1 mol of Ag is 6.022 x 10^23 atoms. This would give you the length of the fiber assuming that it is only one atom thick and all the atoms are lined up perfectly.

Search found 100 matches