CHEMISTRY COMMUNITY

Tony Ong 3K

Thank you so much this quarter Joyce!!!
Definitely the greatest TA to have walked this Earth.

Tony Ong 3K

thank you sensei, you are much appreciated

Tony Ong 3K

Will the final have pseudo equilibrium constants on it where we have to calculate it?

Tony Ong 3K

9.101 A heat pump heats a house in winter by extracting heat from the cold outdoors and releasing it into the warm interior. For the transfer of a given amount of heat, (a) how do the entropies of the interior and exterior of the house change (increase or decrease)? (b) Which change is greater? Assu...

Tony Ong 3K

What would be the process to solve this question: Suppose 2 mole ice cube at -10 C is placed in 20.0mole of water at 20 C. Enthalpy of fusion of ice is 6.01kj/mol and molar heat capacities of ice and water at constant pressure are 37.7 J/K/mol and 75.3 J/K/mol. Calculate temperature after thermal eq...

Tony Ong 3K

of course it is...it's part of the outlines...

Tony Ong 3K

Yes, always take into account the slowest step. The rate law would be the rate constant times the reactants of that step.

Tony Ong 3K

Why does NO have greater residual entropy than BF3 at 0K???

Tony Ong 3K

a) The standard Gibbs free energy of formation of Ti3+(aq) is 215 kJ/mol at 25 degrees C. Calculate the standard
potential of the Ti3+/Ti couple.
b) Will Ti+ disproportionate in aqueous solution?

Why is the 215kj/mol switched to -215jk/mol in part a of this problem's solution?

Tony Ong 3K

Write the half-reactions and the balanced equation for the cell reaction for each of the following galvanic cells:
(d) Pt(s) |O2(g)| H+(aq) || OH-(aq)| O2(g) | Pt(s)

How do I find the half reactions and balanced ???

Tony Ong 3K

The reaction taking place in a nicad (nickel–cadmium) cell is Cd(s) +
2 Ni(OH)3(s) S Cd(OH)2(s) + 2 Ni(OH)2(s), and the cell potential when fully
charged is +1.25 V. What is the reaction Gibbs free energy?

Tony Ong 3K

you can also think of it as expansion work is done by the system to the environment therefore the value for work is negative.

Tony Ong 3K

an agent which is becoming oxidized essentially loses its electrons and becomes a more positive charge whereas ones that become reduced gain electrons and become more negatively charged

Tony Ong 3K

does anyone know if we can argue our midterm scores?

Tony Ong 3K

Q: What do you do with a sick chemist?
A. First you try to helium, then you try to curium, but if this fails then you have to barium.

Tony Ong 3K

Q: What do chemists call a benzene ring with iron atoms replacing the carbon atoms?
A: A ferrous wheel:
Fe - Fe
/ \
Fe Fe
\ /
Fe - Fe

Tony Ong 3K

Outside his buckyball home, one molecule overheard another molecule saying, "I'm positive that a free electron once stripped me of an electron after he lepton me. You gotta keep your ION them."

hahahhahahhaa

Tony Ong 3K

hehe this ones a goood one

Q: What did the scientist say when he found 2 isotopes of helium?
A: HeHe

hehe get it?

Tony Ong 3K

Q: Did you hear oxygen went on a date with potassium?
A: It went OK.

Tony Ong 3K

Q: What is the chemical formula for "coffee"?
A: CoFe2

hehehehehe

Tony Ong 3K

Did you hear the joke about the chemist?
Me neither.

Tony Ong 3K

What should you do if no one laughs at your chemistry jokes?
Keep telling them until you get a reaction.

Tony Ong 3K

Two chemists walk into a bar.
One says, “I’ll have an ‎H2O.” The other says, “I’ll have an ‎H2O, too.” The second chemist dies.

*H202 is hydrogen peroxide

Tony Ong 3K

as a means to check if your approximations are correct,
remember the 5% rule at the end!

Tony Ong 3K

pKA usually deals more with weak acids which cannot dissociate fully as opposed to strong acids where we can automatically calculate the pH because we know it dissociates completely.

Tony Ong 3K

I believe that negative delta H is exothermic so it gives off heat and positive delta H is endothermic, so it requires heat. But would that be the same for negative delta G and positive?

Tony Ong 3K

Moreso on that, think of water, or any other forms of pure liquids, as solvents. Usually, solvents are larger in concentration than its solute constituents. Therefore, even during equilibrium the relative concentration of solvents remain the same.

Tony Ong 3K

Keep in mind that when approximating, Professor Lavelle said that it should be less than 10^-3 values. The 5% rule is simply a mechanism to check whether or not your approximations are valid.

Tony Ong 3K

Kc is regarding molar concentrations whereas Kp is for homogeneous gas equilibria.

If in any case you're required to convert from Kp to Kc or vice versa, you can use the formula:
Kp=Kc(RT)^deltaN

Tony Ong 3K

during lecture, Professor Lavelle pointed out that changing pressure does not change the Kc value, but changing the temperature is what changes the Kc value.

Tony Ong 3K

nope no difference! Hope that helped because I have to sleep now!

Tony Ong 3K

you can also think of it in the sense that endothermic reactions REQUIRE energy and thus can be in the form of heat where exothermic reaction RELEASES energy, which can be in the form of heat as well.

Tony Ong 3K

Hello Professor Lavelle!
I appreciate your dad hat and your quirky humor. You bring light upon the clouded world of chemistry. I cannot wait to take 14B with you.
But for now, I must depart and I hope your winter break is brimming with chemistry among your family members and friends.

Tony Ong 3K

does not matter but I would say just to be safe follow the order given in the name

Tony Ong 3K

either is fine... -o or -ido are both acceptable suffixes.

Tony Ong 3K

yes lone pairs dictates the molecular shape.
For instance, let us assume that a central atom has a steric number of 4. This means that its electron arrangement is tetrahedral, however say it has 2 lone pairs. This means that the molecular shape is angular.

Anyhow, Have a nice night!!!

Tony Ong 3K

they're both the same thing, just defined differently
bronsted acid is proton donor while lewis definition of acid is electron acceptor

Tony Ong 3K

yes, they always completely dissociate

Tony Ong 3K

Polar bonds have partial charges due to the unequal distribution of charges/electrons whereas nonpolar bonds have an equal distribution. Usually symmetrical molecules are nonpolar because the charges are evenly distributed. All Carbon-Hydrogen bonds are nonpolar.

Tony Ong 3K

i believe neither; it is just more spread out, and thus entropically favored.

Tony Ong 3K

nonpolar compounds have a tendency to aggregate together...such is the case in a cell's lipid bilayer, where the nonpolar, hydrophobic tails face inwards towards another while the hydrophilic, polar heads face outwards. This is key towards regulating a cell's metabolism.

Tony Ong 3K

you want to draw out the lewis structure always to determine what the Steric Number is for the central atom...then you can determine shape from there. Don't cheat your way with shortcuts!!!! It'll be your ultimate downfall! oh and steric number means bonded pairs of electrons (double bond counts as ...

Tony Ong 3K

you want to draw out the lewis structure always to determine what the Steric Number is for the central atom...then you can determine shape from there. Don't cheat your way with shortcuts!!!! It'll be your ultimate downfall! oh and steric number means bonded pairs of electrons (double bond counts as ...

Tony Ong 3K

My TA Joyce emailed out her notes and it's incredibly useful for the VSPER Model chart, detailing lone pairs, electron density, and molecular shape that you should memorize!

Tony Ong 3K

NO CLASS WOOOO ENJOY YOUR THANKSGIVING!!!

Tony Ong 3K

I thought dipole moments would only be taken into consideration when drawing VSPER models?? Isn't lewis structures mainly just the elements present in a molecule and its lone pairs of electrons?

Tony Ong 3K

don't worry about deriving the Schrodinger's equation because that requires 2nd level derivatives but for now, the quantum numbers that we use
(n, l, ml, ms) are derived from the Schrodinger's equation.

Tony Ong 3K

no those are for VSPER models.
Lewis structures is a 2D structure that depicts the lone pair electrons that may exist in a molecule

Tony Ong 3K

In combustion, the reactants is always whatever they give you with Oxygen (O2) and the products is H20 and CO2...however, make sure to balance the equation my friend!

Hope this helps ?? Lemme know if it doesn't I will respond with more explanations :)
Goodnight

Tony Ong 3K

For uncertainty of velocity, if they give you that the speed is 373.23 plus or minus .34 m/s, is the uncertainty in velocity 373.23 or .34 or how do you calculate it??

Tony Ong 3K

How many questions are on the midterm?

Tony Ong 3K

You can also think of degeneracy as when we learned the quantum numbers. The values of Ml represent the number of degeneracy. In a 2s orbital, n=2 and l=0, therefore the only value for Ml is 0. Therefore there is 1 degeneracy. In a 3p orbital, n=3 and l=1, therefore the values for Ml is -1, 0, 1. Th...

Tony Ong 3K

Normally, the ones with less than 4 valence electrons loses its electrons while the ones over 4 valence electrons want to gain electrons. Both want to fulfill the octet rule in the least possible manner of gaining or losing electrons possible if that makes sense.

Tony Ong 3K

Something that is also interesting is that Chlorine actually has a higher electron affinity than Fluorine. Fluorine is smaller than Chlorine, therefore there is less space availalbe in its 2p orbital. Chlorine's outer orbital is a 3p, so therefore there's more space for electrons to be shared in thi...

Tony Ong 3K

Do we have to understand the concepts of black body for the midterms? I don't remember Professor Lavelle going over this thoroughly or at all during class?

Tony Ong 3K

All values and equations are given to you! But I suggest for the sake of time on your tests to memorize the more commonly used values such as Planck's constant (h) or the speed of light (c) or even the mass of an electron 9.109*10^-31 kg.

Tony Ong 3K

You can think of the Kinetic Energy as the "excess" energy emitted if that helps. Professor Lavelle mentioned that there can only be Kinetic energy released if the E (photon) > Work function. So knowing this, if E(photon) equals threshold/work function, then kinetic energy is 0. So wheneve...

Tony Ong 3K

First you use molar mass of KMnO4 to find its moles. Convert 5.00 g KMnO4 into moles by dividing by the molar mass, (5.00 g KMnO4)/(158.04 g/mol KMnO4)= 0.0316 mol KMnO4. Then divide by the volume of the solution made to find the concentration, (0.0316 mol KMnO4)/(.15000 L)= 0.211 mol/L KMnO4 soluti...

Tony Ong 3K

That is strange! I would say to always keep the habit of putting the correct sig figs regardless because it's 1 point off per question on the midterms and finals!

Tony Ong 3K

For a line at 102.6nm, you convert into meters and then do following: V=c/λ =(3.00*10^8ms^-1)/102.6*10^9m= 2.922 * 10^15 s^-1 Then use Rydberg to find values for N : V=R[(1/n1^2)-(1/n2^2)]. We know that hydrogen has n1= 1, so 1/n2^2= 1/1^2 - V/R 1/n2^2= 1 - ( 2.922 * 10^15 s^-1)/(3.29 * 10^15 s ^-1)...

Tony Ong 3K

If you look in Dr. Lavelle's Outline 1: Review of Chemical and Physical Principles objectives that we should know by the end of the section, it just states that we should be able to "write symbols for elements given their names." So I'm sure at this point in time, we do not need to memoriz...

Tony Ong 3K

Multiplying by the subscripts would change the chemical structure of the molecule and make an entirely different molecule. However when you multiply by the stoichiometric coefficients, you're essentially multiplying the subscripts as well because the stoichiometric coefficients apply to the entire m...

Tony Ong 3K

If I understood your question correctly, then in order to figure out the theoretical yield of a specific product, you would have to use the moles of the limiting reagent and multiply by the molar ratio of the product to the limiting reagent given in the chemical equation to find the maximum moles of...

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