CHEMISTRY COMMUNITY

Marcela Udave 1F

I believe it's because it's a constant temperature.

Marcela Udave 1F

6N.15
Calculate the potential of a cell constructed with two nickel electrodes. The electrolyte in one compartment is 1.0M Ni(NO3)2(aq). In the other compartment, NaOH has been added to a Ni(NO3)2 solution until the pH=11.0 at 298K. See Table 6I.1.

Marcela Udave 1F

Yeah, I plan on doing the homework problems, the tests and midterm questions.

Marcela Udave 1F

I think questions that are also brought up on chemistry community.

Marcela Udave 1F

I believe disproportionation usually involves redox reaction; disproportionation reactions follow the form: 2A → A' + A"

Marcela Udave 1F

I believe the sessions start Saturday but he has yet to give the times.

Marcela Udave 1F

Solid|ion||ion|solid

Marcela Udave 1F

Sorry! What I meant to say was why was C(gr) not included in Sn4+(aq)+2e- → Sn2+(aq) ?

Marcela Udave 1F

You add Pt to the side that doesn't have a solid.

Marcela Udave 1F

The standard cell potential measures the driving force for a given redox reaction.

Marcela Udave 1F

6M.3 Predict the standard potential of each of the following galvanic cells:
For part d, why is C(gr) not included for the anode?
(d) C(gr)|Sn4+ (aq),Sn2+ (aq)||Pb4+ (aq),Pb2+ (aq)| Pt(s)

Marcela Udave 1F

Okay that makes sense. Thank you!

Marcela Udave 1F

Why isn't H2O included in the cell diagram?

Marcela Udave 1F

I think you include it if you have gases and there's no solids.

Marcela Udave 1F

If I'm not mistaken, it's just a matter of preference.

Marcela Udave 1F

If the free energy is zero, then the reaction is at equilibrium meaning that an no more work can be done.

Marcela Udave 1F

I second that, they can get confusing. Tips would be helpful!

Marcela Udave 1F

Potassium chloride or sodium chloride are usually used.

Marcela Udave 1F

If there is less disorder in a system, then entropy is negative.

Marcela Udave 1F

Gibbs free energy is energy available to do work and can be used to determine the spontaneity of a reaction. Entropy is a measure of the molecular disorder of a system.

Marcela Udave 1F

I believe so since if ΔG=0 then it's at equilibrium.

Marcela Udave 1F

I'm not too certain but i think you do.

Marcela Udave 1F

Remember that when an atom gains an electron, its reduction and when it loses electrons its oxidation.

Marcela Udave 1F

Gibbs free energy measures how much potential a reaction has left. Hence if the free energy is zero, then the reaction is at equilibrium, and no more work can be done.

Marcela Udave 1F

Test 2 covers all topics on Gibbs free energy and electrochemistry up to but not including the Nernst equation!

Marcela Udave 1F

https://chem.libretexts.org/Bookshelves ... _Chemistry)/Electrochemistry/Voltaic_Cells/The_Cell_Potential

This link is very helpful in explaining cell potential!

Marcela Udave 1F

I haven't seen any practice problems but do you know if we'll have to have graphical methods for Van't Hoff's equation?

Marcela Udave 1F

The solutions for the midterm are posted on the class website!

Marcela Udave 1F

Enthalpy ('H') refers to the measure of total heat content in a thermodynamic system under constant pressure whereas enthalpy is calculated in terms of change. Keep in mind the the SI unit of enthalpy is joules (J).

Marcela Udave 1F

I included gibbs free energy but also added some material on thermal dynamics.

Marcela Udave 1F

I'm actually struggling with grasping that subject too. I also thought it was oxidizing.

Marcela Udave 1F

Yes, doing all of the homework questions help a lot because you'll realize what you need to improve one and by doing so you can seek aid in one or many of the sessions.

Marcela Udave 1F

Yes, doing all of the homework questions help a lot because you'll realize what you need to improve one and by doing so you can seek aid in one or many of the sessions.

Marcela Udave 1F

When asked for the shape, are we always supposed to say the molecular geometry rather than the electronic geometry?

Marcela Udave 1F

Yes, they are all polar.

Marcela Udave 1F

One of the UA told me they were the same thing.

Marcela Udave 1F

(a) Draw a Lewis structure for each of the following species: CH3 ; CH4; CH3 ; CH2; CH22 ; CH22 . (b) Identify each as a radical or not.

How do you identify if they're radicals or not?

Marcela Udave 1F

The coordination number equals the number of ligands.

Marcela Udave 1F

Why is NO3- nonpolar?

Marcela Udave 1F

They go head to head.

Marcela Udave 1F

Yes you did but it's not the molecular formula but VSEPR formula.

Marcela Udave 1F

By the electronegativity difference between the atoms. If they cancel each other then it's non polar.

Marcela Udave 1F

KylieY_3B wrote:I believe it's for the entire molecule.

Okay! Thank you!

Marcela Udave 1F

https://www.youtube.com/watch?v=dudRIG-dRE4

That video might help clarify resonance structures and bond lengths.

Marcela Udave 1F

So just to clarify, as long as there's resonance then there's delocalized pi bond?

Marcela Udave 1F

Predict the bond angles at the central atom of the following molecules and ions: (a) ozone, O3; (b) azide ion, N3 ; (c) cyanate ion, CNO ; (d) hydronium ion, H3O . For part a.) For the lewis structure of O3, why isn't there double bonds connecting both the oxygen to the oxygen with the lone pair? Al...

Marcela Udave 1F

4.46 Describe the structure of the formamide molecule, HCONH2, in terms of hybrid orbitals, bond angles, and sigma and pi bonds. The C atom is bonded to one H atom, a terminal O atom, and the N atom. The N atom is also bonded to two H atoms. Do you get the sigma and pi bonds for the entire molecule ...

Marcela Udave 1F

I heard that today's lecture was also included.

Marcela Udave 1F

So for this problem we don't describe the hybrid orbitals on each carbon atom? Or by describing the CH2 we identify the hybrid orbital of Acrylonitrile?

Marcela Udave 1F

The test covers everything up to Monday's lecture even if your discussion is on Tuesday. Just wanted to clear things up! Since in the past he has put material on the test from the lecture on Monday so now I know to study up to Monday lecture ! Thanks! Are we supposed to know everything he went over...

Marcela Udave 1F

I think you should use the formal charge when dealing with Lewis structures so you don't loose the habit.

Marcela Udave 1F

If I'm not mistaken oxygen has a double bond with sulfur.

Marcela Udave 1F

b) What is the expected OClO bond angle?
Do you go from oxygen to oxygen and say it's less than 120 degrees?

Marcela Udave 1F

There's a chart in 4.2 that has the electron arrangement, number of atomic orbitals, hybridization of the central atom, and the number of hybrid orbitals. It can be helpful since it gives a breakdown.

Marcela Udave 1F

You use hybridization to explain molecular geometry hence:
linear → sp
trigonal planar → sp²
tetrahedral → sp³
trigonal pyramidal → sp³d
octahedral → sp³d²

Marcela Udave 1F

Note:
Single bonds--> one sigma bond
Double bonds--> one sigma and one pie.
Triple bonds--> one sigma and two pies.

Marcela Udave 1F

I don't think resonance affects it but Im not certain. That being said hybridization to explain molecular geometry.
linear → sp
trigonal planar → sp²
tetrahedral → sp³
trigonal pyramidal → sp³d
octahedral → sp³d²

Marcela Udave 1F

So we don't need to know how to draw the 3D shape right?

Marcela Udave 1F

Just for clarification, a partially positive element does not mind sharing electrons while a partially negative receives the electrons?

Marcela Udave 1F

The atomic size can increase the bond length.

Marcela Udave 1F

I do not know if there's a study group but I wouldn't mind forming a study group.

Marcela Udave 1F

Wait..I was confused. The work function and avogrado's number is for part b. So it all works out.

Marcela Udave 1F

Yes, the empirical and molecular can defiantly be the same.

Marcela Udave 1F

28. Light hits a sodium metal surface and the velocity of the ejected electron is 6.61 x 105 m.s-1. The work function for sodium is 150.6 kJ.mol-1. A. What is the kinetic energy of the ejected electron? I used the fromula EK=1/2 MV^2 and got 1.99*10^-19 but I don't understand how to apply the work f...

Marcela Udave 1F

For Tuesday, do we have to turn in seven problems that relate to quantum?

Marcela Udave 1F

We're encouraged to do as many as we can but to make it easier for the TAs we should only turn in the seven we want graded.

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