CHEMISTRY COMMUNITY

Ya Gao

The activated complex refers to the transition state. Based on reactants and products as given, the transition state can be figured out (which atom should be linked to which atom etc.)

Ya Gao

If a molecule is produced and consumed in the next step, it's an intermediate.
If a molecule appears on the reactant side and the product side, it's a catalyst.

Ya Gao

Heat capacity of water is high because the hydrogen bonds that make up water are considered strong bonds. They are hard to break.

Ya Gao

Entropy is a extensive property because it depends on the number of moles involved ( involves mass, size )

Ya Gao

Yes, because catalyst lowers the activation energy which works in both the forward and reverse reactions.

Ya Gao

You cannot determine the rate law by justing looking at the balanced equation unless it is an elementary step.

Ya Gao

I would say it will be helpful to know how to derive those equations.

Ya Gao

Intermediate can be determined by looking at the separate steps of a reaction. If one molecule is produced in one step and consumed in the following step, then the molecule can be considered an intermediate.

Ya Gao

You can calculate the unit of k based on the rule that the rate of reaction has an unchanging unit which is mol*L-1*s-1

Ya Gao

Half life of a second order reaction is dependent on the initial concentration since the the half life equals to 1/k[Ao]

Ya Gao

Yes and it not only works for first order reactions. It is the case for all reactions.

Ya Gao

Yes! I think in class, it is put as rate of constant k depends of temperature and activation energy.

Ya Gao

To see if a metal will dissolve in the solution, you need to list out the corresponding cathode and anode reaction. In this way, the overall cell potential can be calculated. If the overall cell potential is positive, then the medal will dissolve in the solution.

Ya Gao

There are two ways to calculate the cell potential. 1st: list out the anode and cathode reaction and copy the corresponding cell potential to these two reaction. Cell potential of this reaction equals to cell potential of the cathode reaction minus the cell potential of the anode reaction. 2nd: list...

Ya Gao

Hey guys, I'm having trouble solving question 14.37a.
Determine the potential of the following cell: Pt(s)|H2 (g. 1.0 bar) | HCl (0.075M)||HCl(1.0 mol\L) |H2(1.0 bar)|Pt(s)
Can someone please tell me how to put in the data. Thanks!

Ya Gao

Hey guys, I'm having trouble getting the right answer for question 14.5d. A little clarification would be helpful. Thanks!
P4=H2PO2- + PH3 under basic condition.

Ya Gao

The question states that 'We expect a reaction to be spontaneous if it is exothermic at a very low temperature.' I wonder if we need to know the sign of ∆S to figure out if the ∆G is negative.For the next true or false question, it said that We can expect an endothermic reaction to be favorable at a...

Ya Gao

Both endothermic and exothermic reactions involve forming bonds but exothermic reactions are favored because even though it is forming bonds, the energy of the products is lower than the energy of the reactants.

Ya Gao

Diatomic atoms have more entropy than monatomic molecules because there are more possible states to be occupied and the rotational and vibrational energy contribute to the greater entropy.

Ya Gao

Hey, do you know where are the simple answers posted?

Ya Gao

I think the standard pressure is 1bar but because 1atm is so close to 1bar, we consider 1atm the standard pressure as well.

Ya Gao

I think what you are asking what is the minimum temperature when the reaction is spontaneous? The reason that ∆G is 0 because when ∆G is negative, the reaction is spontaneous, therefore, to figure out the minimum temperature, we set the limit:∆G=0, so any temperature above the limit will have a ∆G a...

Ya Gao

Can someone explain why ∆S=q/T=nR ln(V2/V1)? I know that ∆S=klnW2/W1, so does nR equals k then?

Ya Gao

I think the easy way the understand it is the possible arrangement atoms can have under specific environments.

Ya Gao

I'm confused about how can we find out if a reaction is reversible or not. Are we gonna be given information about it?

Ya Gao

When the molecules are in gas phase, there are many more possible states they can occupy compared to the possible states molecules can occupy when they are in liquid phase or solid phase. With more possible states, the entropy will be higher.

Ya Gao

It means that when a gas is working as an ideal gas, its Cv and Cp will be 3/2R and 5/2R. It can be found on the equation sheet.

Ya Gao

As we know, change in internal energy equals w+q and w=-q*∆V. For gases, when it's under constant pressure and there is a net change in the number of moles, there will be a change in the volume. According to PV=nRT, P∆V=∆nRT. Therefore, when a reaction under constant pressure and has a net change in...

Ya Gao

I'll say use liter for volume and atm for pressure.

Ya Gao

Hey, how do you know the molar heat capacity is 5/2R and 3/2R ? Can you explain a little bit?

Ya Gao

Hey, if a work is done by the system, it is considered negative because the system as a whole is losing energy. Since condensation requires energy, work has to be done to the system so that condensation can occur. Hope that helps.

Ya Gao

Hey, P∆V represents work done to the system. Since w=FxD and F=PxA D (distance) and A (area), we can get the equation w=P ∆V.
Hope it helps.

Ya Gao

Hey, I believe ligand is what is attached to the transition metal and the coordination complex is the metal with the ligands.

Ya Gao

Hey guys, on the final there was a question that asks for the shape ( not electron density) of nitrogen atoms.What does the shape mean??

Ya Gao

Hey, I think professor Lavelle mentioned in class that solution can have negative pH when it is superacid.... Hope it helps.

Ya Gao

Hey, there are two hydroxide ion per Ba(OH)2 because if we write out the balanced equation: Ba(OH)2----Ba2+ + 2OH-, for every Ba(OH)2 molecule ionized, two hydroxide ions is produced. That's why you need to multiply it by 2. Hope it helps.

Ya Gao

Hey, I believe in class, professor Lavelle said that species like NH3, NaCl are electron rich, so they will replace H2O ligands and form coordination compounds. Hope it helps.

Ya Gao

Hey, dipole moment is resulted from an uneven distribution of electrons between atoms. When the electronegativity difference between the atom is big, the dipole moment will be big and when the electronegativity difference is small, the dipole moment will be small. Hope it helps.

Ya Gao

For ion CO3 2-, I think it is bidentate because if you draw the lewis structure of it, you will see that two out of the three oxygen have lone pairs around them and do not have a formal charge of 0. So for these two oxygen atoms, they would want to form bonds. For water molecule, if you draw out the...

Ya Gao

The number is related to the number on the periodic table because the number represents which orbital the valence electron is, for example, H1s, the valence electron of hydrogen atom is in the 1s orbital. Hope that helps.

Ya Gao

I have a question about how many pi bonds are formed in benzene. In class, professor Lavelle said that there are three pi bonds formed in benzene because there are three double bonds formed between C-C, but what about the unhybridized 2p electrons, don't they also form pi bonds with each other? Do w...

Ya Gao

Yeah, for questions about hybridization, you need to find out the number of electron densities around the central atom by drawing the Lewis structure. After you find out the number of electron density around the central atom, you can figure out the hybridization because regions of electron density e...

Ya Gao

Tetrahedral is when the central atom has only four bonds around it(no lone pairs) and trigonal pyramid is when the central atom has three bonds and one lone pair around it. Hope it helps.

Ya Gao

In these kinds of questions I always assume the way the molecule is written as the way it is bonded.

Ya Gao

Hey, highly distorted electron means the electron is loosely held by the atom or ion, therefore it can easily be distorted. Ions that cause large distortions are described as having high polarizing power, in this case, small highly charged ions. Hope it helps.

Ya Gao

I think the 3d diagrams are the actual shape of the electron orbitals because they are based on mathematical equations. Hope it helps.

Ya Gao

I think it depends on what the central atoms are. Like we said before, if the central atom is P, S, or Cl, they can have extra electrons around them because they do have a d orbital. And if there are two central atoms, they still have have more electrons depending on what they are. Hope it makes sen...

Ya Gao

Well, 4pi must have come from some kind of experiment or something. For now, I don't think we are able to understand how scientists derived the specific function, but maybe we will, in the future.

Ya Gao

To the question about d orbital, 3d orbital comes after 4s orbital. About where different orbitals are, you can refer to the energy level of different orbitals on page 43. About why electron spin is +-1/2, I believe the values are derived from experiment... but exactly why +- 1/2, I have no idea :(

Ya Gao

Can somebody please tell me why there is a negative sign in the equation ∆E=-hR/n2. I didn't quite get that in the class and why n approaches infinity the energy of the electron will be 0? Doesn't it have to receive a ton of energy to be excited to the outer levels?? I'm so confused.

Ya Gao

I think this question is asking for all the conditions that apply to the situation. Since electrons can be ejected when the energy of the photon is equal or greater than the energy needed to remove the electron which is work function, so choice B and C both are correct.

Ya Gao

So if the amplitude of the light is higher, does the light become brighter?

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