CHEMISTRY COMMUNITY

KarlaArevalo2F

Hey friends, attached are the pictures of the 1pm Lecture!

KarlaArevalo2F

thank you both!

KarlaArevalo2F

We are given that this is a first order reaction, 2A -> B + C, given that [A]0 = 0.153 mol/L and that after 115sec the conc. of B rises to 0.034 mol/L. How would we go about solving for [A]?

KarlaArevalo2F

Ahhh!! thank you so much! I kept reading other explanations but yours was much clearer!

KarlaArevalo2F

What is the best way to approach problems asking to solve for rates and orders given a chart?

KarlaArevalo2F

How does one find n to plug into the Nernst?

KarlaArevalo2F

I was wondering this too. How would you go about solving for Q?

KarlaArevalo2F

We use Pt (s) when the reaction lacks a conducting metal, so if we have (aq)|(g)||(aq)(aq) we would add Pt(s) to both sides

KarlaArevalo2F

what is reduced is the oxidizing agent and what is being oxidized in the reducing agent. Its basically flipped

KarlaArevalo2F

Can someone explain why the solution manual is using the formula deltaG=-RTlnK + RTlnQ instead of deltaG= deltaGnot + RTlnQ.

KarlaArevalo2F

Why dont we multiply the E value in relation to the number of moles ?

KarlaArevalo2F

Flip the anode because we should be looking at its reverse reaction

KarlaArevalo2F

In some aspects no, however, if the reaction is reversed then the sign is flipped other than that I think that it remains the same.

KarlaArevalo2F

the slope refers to the rate, so lower heat capacities = steeper slope because it can reach the next phase quicker and higher heat capacity, more shallow because more energy and time is needed to reach next phase change

KarlaArevalo2F

-delta H means the system is exothermic and is releasing heat (surrounding absorb that heat) and + delta H means the system is endothermic and requires heat

KarlaArevalo2F

will we be required to know this conversion or will it be given in the problem?

KarlaArevalo2F

Will class be review or will we be continuing learning different material/ expanding?

KarlaArevalo2F

also, does any one know where we can get more practice problems besides Lyndon's?

KarlaArevalo2F

when is his review session?

KarlaArevalo2F

i also agree that it is the number of particles to the number of different positions they can occupy

KarlaArevalo2F

I remember that Dr. Lavelle mentioned that water vapor burns are more painful, however, can someone explain as to why they are worse/ more painful?

KarlaArevalo2F

i think we look at the absolute values to determine which does more work. the sign is associated with what is doing the work; for example work is positive if its being done on a system and negative if its being done by a system.

KarlaArevalo2F

hi becky, how did you derive this equation?

KarlaArevalo2F

melting and vaporization are considered endothermic because molecules must be broken up using heat, the definition of being an endothermic reaction.

KarlaArevalo2F

enthalpy is positive for endothermic because there is the need for heat, while enthalpy is negative for exothermic because heat is being released (exo=exit/out)

KarlaArevalo2F

enthalpy is positive for endothermic because there is the need for heat, while enthalpy is negative for exothermic because heat is being released (exo=exit)

KarlaArevalo2F

remember state properties are only looking at the initial and final and nothing in between.

KarlaArevalo2F

since K is temp. dependent, if a rxn needs heat (endothermic) the products will be favored. if a rxn is releasing heat (exothermic) the reactants will be favored. I see it as if you need heat you need more energy to produce, and if you give off heat, you are favoring your reactants

KarlaArevalo2F

I thought NH3 was amphoteric because it can act as both a base and an acid depending on what it reacts with
for example in 2Na + 2NH3 = 2NaNH2 + H2, NH3 acts as an acid because it donates a proton
in NH3 + HCl = NH4+Cl-, NH3 is accepting a proton meaning it acts as a base

KarlaArevalo2F

I too recall him saying 'shifting' is used more when referring when the reaction is not at equilibrium and prefers the term 'leans towards right/left' to indicate if it favors products or reactants.

KarlaArevalo2F

Thank you both!

KarlaArevalo2F

thank you for your explanation! My point of confusion is using the quadratic formula in the chart. May you please explain..

KarlaArevalo2F

What is the difference between Kc and Qc? I know K has the brackets while Q uses partial pressures, however, what is the distinction?

KarlaArevalo2F

How would one understand to complete an ICE chart for problem 11.49? I have gotten the initial for NH3 but how would we know what steps to follow after? (First time seeing ICE charts :( )

KarlaArevalo2F

It might be a redundant question, but do we need to create a new account or do anything in particular for 14B to make sure our posts get recorded? Do we continue using the same account we created for 14A? (just want to make sure to not lose my points..)

KarlaArevalo2F

How do we easily find out if the coordination compound is polydentate?

KarlaArevalo2F

Is there an easy way to the oxidation number for ions like sulfate? This is the first time I take chem in my life (HS didnt offer it) so I feel behind in knowing oxidation numbers. Group 1 has an oxidation number of +1 Group 2: +2 Group 13 (with Boron): +3 Group 14: +4/-4 Group 15: -3 Group 16: -2 ...

KarlaArevalo2F

Just by looking at a structure and/ or formula, how can we tell if it will be a polydentate or form chelates?

KarlaArevalo2F

How would we solve for the concentration? I am stuck as to how to even start.

KarlaArevalo2F

Is there a difference between the Brønsted and conjugated acids and bases? How do you tell them apart?

KarlaArevalo2F

Is there an easy way to the oxidation number for ions like sulfate? This is the first time I take chem in my life (HS didnt offer it) so I feel behind in knowing oxidation numbers.

KarlaArevalo2F

when talking about bronsted think of protons (sharing of H+ ion):
bronsted base- accepts protons; bronsted acid- donates protons
when talking about lewis think lone electron pairs:
lewis base- donates e- pair; lewis acid- accepts e- pair

KarlaArevalo2F

Yes, because they are attached to the central, causing a share of electrons. They are what create the sphere

KarlaArevalo2F

Does anyone have an easy way to find the hybridization of the central atom they are able to share? Much appreciated.

KarlaArevalo2F

using the 3D model its checking for symmetry and not all polar bonds have nonpolar molecules

KarlaArevalo2F

104904344 wrote:And sigma bonds are stronger than pi bonds, right?

yes due to the larger amount of overlap between the two orbitals

KarlaArevalo2F

there is more overlap in sigma bonds than in pi bonds which makes for the stronger bond

KarlaArevalo2F

Will the final be cumulative or just from midterm to the end?

KarlaArevalo2F

its the same thing, both are where electrons can be found

KarlaArevalo2F

its best to know each shape and the angles corresponding to them

KarlaArevalo2F

I believe he mentioned we should know the general ones like 90, 180, and for bent it should be slightly less than 109.5 but not the exact angle

KarlaArevalo2F

Im sorry, but can someone explain why a structure cannot be tetrahedral planar if it were planar and the angles were 90 degrees apart? Why isnt that a VSEPR shape?

KarlaArevalo2F

I think the bond angles will give you the geometry if they are all the same. If they differ then that may lead to there being lone pairs. But we should get a molecular shape diagram and it'll become apparent if there are lone pairs because it would not follow the basic geometry (no lone pairs)

KarlaArevalo2F

I think we might (should) get like the general shapes and structures on the formula sheet, at least that is what a past chem prof. gave us not to sure

KarlaArevalo2F

I believe that nonpolar molecules exist as long as the dipoles cancels out and there is not net charge towards an atom. Having at least one dipole moment not canceling out will result in a polar molecule.

KarlaArevalo2F

I believe bond order refers to the number of bonds between two atoms. a single bond would have a bond order of 1, double bonds have a bond order of 2, and triple bonds have a bond order of 3

KarlaArevalo2F

I believe Sulfur has a higher affinity than Oxygen because sulfur is able to have an expanded octet, meaning it can have more than 8 electrons because it still has the 3d subshell while oxygen strictly follows the octet guideline (can only have 8 electrons).

KarlaArevalo2F

So the book says that nodal planes separate the two lobes of a p-orbital where the wave function is 0. How come s orbitals do not have a nodal plane? s orbitals do not have a nodal plane because it is the only orbital that has a symmetrical electron probability distribution and is a spherical shape...

KarlaArevalo2F

Why is 3d a lower energy level than 4d after Z=20? Isn't the periodic table arranged so that energy levels increase as you go? 1s^2, 2s^2, 2p^6,3s^2,3p^6,4s^2,3d^10,4p^6....?

KarlaArevalo2F

What does it mean for energy levels to be degenerate ? Is it that there are multiple orbitals, like in p?

KarlaArevalo2F

During the exams, will we have to memorize 1 J= 1 kg*m*s^-1 or would it be given to us?

KarlaArevalo2F

How can light gain a mass when in motion, but has no mass when stationary?

KarlaArevalo2F

How is the mass of light calculated? I know it can only have a mass when it is in motion and not when it's stationary.

KarlaArevalo2F

I recall Dr. Lavelle mention how light is able to act as both a particle as well as a wave? How is this possible?

KarlaArevalo2F

You would want to start off by dividing with the smallest number, then multiply all of the numbers by the same whole number to get the least whole number possible.

KarlaArevalo2F

Something I always do when balancing is I always write down each element on both the reactant and product sides along with the amount of each there is and add a coefficient accordingly to balance both sides. Image added just in case wording isn't clear.

KarlaArevalo2F

It's always best to use the most amount of sig figs when continuing a problem, but always refer to the sig fig rules (which is mostly using the least number of sig figs I believe) when writing the final answer.

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