CHEMISTRY COMMUNITY

Vincent Chiang 1L

Most likely for the exam you will be given whether the elementary reaction is fast or slow.

Vincent Chiang 1L

Aldehydes' C is bonded to either 1 or 2 H. Ketones' C is bonded to 2 C.

Vincent Chiang 1L

If T increases, k increases, and if k increases, A increases. This should mean that as T increases, A should increase.

Vincent Chiang 1L

A compound is an intermediate if it is produced in one step of the reaction and is consumed as a reactant in a later step, but does not appear in the overall reaction. If it appears as one of the reactants at the beginning and later appears as a product in a subsequent step, the compound is instead ...

Vincent Chiang 1L

Rate constant is just a constant of proportionality relating how the concentrations of the participants of the reaction relate to the rate of reaction. The rate itself just shows how fast the concentration of one of the participants changes, in units of concentration/pressure per unit time. The rate...

Vincent Chiang 1L

Yes, when writing the overall rate law, you shouldn't include intermediates, only substances that are in the overall reaction.

Vincent Chiang 1L

What was the question? I'm not in 1I, but I might be able to help if I see the question.

Vincent Chiang 1L

These rankings are not based off the placement of the elements in the periodic table. They are based on the standard reduction potentials of each, given in the table provided on the test. Elements with a stronger reducing power will have a lower reduction potential, therefore; organize them based o...

Vincent Chiang 1L

Supposedly everything on the HW is fair game, but I think for the tests themselves, the questions before the Integrated Exercises are enough (at least that's how it has been). The integrated HW should be done for finals prep, however.

Vincent Chiang 1L

My TA said that the order is not always followed that way. For the purpose of this class, I don't think the order will be stressed upon.

Vincent Chiang 1L

I don't think that matters, as long as you place the right compounds into the right anode or cathode.

Vincent Chiang 1L

Does the order in which we write the galvanic cell components matter? More specifically, is there a reason why I2(s) is in the third position in the given answer, which is Pt(s) | I-(aq) | I2(s) || Ce4+(aq), Ce3+(aq) | Pt(s) ?

Vincent Chiang 1L

My TA said that the questions on the test won't necessarily be given all in acidic conditions. To find out how many H+, H2O, and OH- to add, you'd have to find the oxidation numbers and charges of both sides of the equation, and then add the necessary ions and water molecules to balance the equation...

Vincent Chiang 1L

The KOH is there as a salt bridge to allow for the flow of ions.

Vincent Chiang 1L

The KOH is there as a salt bridge to allow for flow of ions.

Vincent Chiang 1L

Exercise 9.17 (which is on Trouton's Rule) is skipped on the outline, so I don't think so.

Vincent Chiang 1L

No, but they have to be reversible to return to equilibrium.

Vincent Chiang 1L

Max potential of a cell is the maximum potential difference between two half cells in an electrochemical cell.

Vincent Chiang 1L

The first step is to heat the reactants to 100 degrees Celsius using the formula delta S = C(P,m)*ln(T2/T1).

Vincent Chiang 1L

I'd say your best bet is to familiarize yourself with the Constants and Equations sheet, since that'll be given to us on the test. As for which equations are used in a given circumstances, practicing questions helps the most.

Vincent Chiang 1L

Container A's change in entropy is higher than that of Container C since Container A's monatomic particles have greater disorder than Container C's diatomic molecules. Complexity of the molecules are important, but in this question's case, we are looking at the rigidity of the structure.

Vincent Chiang 1L

I believe in irreversible, the pressure is changed immediately, whereas in reversible, the pressure is changed slowly.

Vincent Chiang 1L

For part a, the SSM shows that to find change in H, we should multiply 1.25 mol by 358.8 kJ/mol. However, the book gives us that the change in enthalpy is 358.8 kJ. Why are the two units different?

Vincent Chiang 1L

On the same question but regarding units, can molar heat capacity be J/(mol.C)? It thought it had to be J/(mol.K)...

Vincent Chiang 1L

Endothermic reactions have a positive change in enthalpy, and exothermic reactions have a negative change in enthalpy. Because a gas to liquid change is exothermic, the change in enthalpy is negative.

Vincent Chiang 1L

If I'm understanding your question correctly, the value of the standard enthalpy of sublimation of carbon is, it's +717 kJ*mol^(-1), which was written in the question. If I didn't interpret your question correctly, can you clarify the question?

Vincent Chiang 1L

I think it will be tested, since Professor Lavelle put that topic on the outline.

Vincent Chiang 1L

Although both systems' matter do not have contact with the environment an thus cannot exchange matter, a closed system is one in which the matter can exchange energy with the environment, whereas an isolated system is one in which the matter cannot exchange energy with the environment.

Vincent Chiang 1L

In this question's case, yes. In general, the change in internal energy can be found by adding the two energies, while paying attention to the signs on the energy changes.

Vincent Chiang 1L

Not sure if this will help, but Section 8.8 is where enthalpy questions start, which is what we started going over in class. So I guess 8.29 and on?

Vincent Chiang 1L

After configuring the ICE box and then solving for x, I eventually arrive at x = 2.40, 2.6. Why does x have to be 2.4, and why can't it be 2.6?

Vincent Chiang 1L

When drawing Lewis structures of compounds with ligands, do we need to draw in each ligand's valence electrons?

Vincent Chiang 1L

When there is an overall charge that is not zero in the compound.

Vincent Chiang 1L

Why does (x^2)/([Molarity of CH3COOH] - x) round to (x^2)/[Molarity of CH3COOH]?

Vincent Chiang 1L

On exercise 12.17 d, Bi2O3 is listed as an amphoteric oxide in the SSM. However, as an oxide, Bi is listed as an acidic oxide on Professor Lavelle's lecture notes (the periodic table of oxide figure). Why do the two differ? Does it have something to do with the number of O bonded to the Bi?

Vincent Chiang 1L

Sigma bonds occur when two orbitals, each with 1 electron, overlap end to end to form 1 sigma bond. They allow bound atoms to rotate. Pi bonds occur when two orbitals, each with 1 electron, overlap side by side to form 1 pi bond. Unlike sigma bonds, pi bonds do not allow bound atoms to rotate. When ...

Vincent Chiang 1L

Oops, I'm sorry I meant ligand.

Vincent Chiang 1L

Lavelle uses atm for the purposes of Chem 14A (at least it says so in his course reader).

Vincent Chiang 1L

EDTA is a ligate, so it has 4 binding sites with oxygen and 2 binding sites with nitrogen.

Vincent Chiang 1L

They all should have the same number of each atoms, so I'm pretty sure you can use any, unless I'm not understanding your question right?

Vincent Chiang 1L

There could be more than one sigma bond, but for the purposes of this class, I'm pretty sure we only have to be concerned with the fact that there is usually only one sigma bond (something about how it's hard to draw two orthogonal sigma bonds?).

Vincent Chiang 1L

When I asked my TA, he said that it was intentional that Lavelle labeled the molecule as HOCO as a hint? Generally, it could be written as CHO2.

Vincent Chiang 1L

I think it depends on the bond angles? For example, for part a on the first question, the molecule has a bond angle of 120, which should mean a trigonal planar, or basically 3 electron domains around the central atom. The diagram only shows 2 bonded pairs (which would otherwise be bond angle 180) s...

Vincent Chiang 1L

Can someone explain to me what the dashed lines and/or solid triangles between two atoms signify, and when to draw them? Thanks in advance.

Vincent Chiang 1L

The following question was presented: "Copper is an interesting element as it has 10 elections in its 3d subshell and only one in its 4s subshell. What are the quantum numbers (n and l) that are associated with this last 3d^10 electron? Also, write all the possible values that a spin quantum nu...

Vincent Chiang 1L

According to my TA, noble gases have very low electron affinities.

Vincent Chiang 1L

The example of benzene in lecture shows an example of the electrons involved in multiple bonds, as the structure shows a dotted circle within the carbon ring.

Vincent Chiang 1L

When you draw the sulfate ion (SO4)^2-, how can the sulfur share six electrons and have a total of 12? I thought the max was 8... Thanks in advance.

Vincent Chiang 1L

Can someone explain to me what it means when Lavelle says that paired electrons have opposite spins and parallel electrons have the same spins? I'm trying to visualize it but it's hard picture.

Vincent Chiang 1L

In the Rydberg equation, does (n1)^2 always have to be the lower energy level? Or can it be the first given energy level (for example if the problem says it went from energy level n = 4 to n = 2, can n1 be 4)?

Vincent Chiang 1L

Based on the SSM, for the second row in the table, why don't the number of sig figs match? 5.0E14 Hz is 2 sig figs, and 600 nm is 1 sig fig... Thanks in advance.

Vincent Chiang 1L

In discussion we discussed energy levels and changes in energy (delta E), absorption, and emission. We were told that E (photon) = delta E. I understand that absorption of photons results in increased energy levels (n), with delta E being positive. I was curious, in emission, since photons are eject...

Vincent Chiang 1L

Caproic acid is composed of C, H, and O. 0.225 g of this sample is combusted. 0.512 g of CO2 is produced. 0.209 g of H2O is produced. What is the empirical formula? This question was given during discussion section. I found how many moles of each product were produced (both were 0.0116 mol), but I d...

Vincent Chiang 1L

May seem like a silly question, but I noticed during lecture notes that every time the professor displayed a chemical equation, he'd always have each molecule's state of matter in parentheses. Is it incorrect to write a chemical equation without writing the states of matter? Thanks in advance.

Search found 54 matches