CHEMISTRY COMMUNITY

jessicahe4Elavelle

Do catalysts affect the equilibrium constant or the amount of products/reactants formed?

jessicahe4Elavelle

Does anyone know when final grades are usually posted on my.ucla?

jessicahe4Elavelle

yes so the correct answer would have been phosphoric acid

jessicahe4Elavelle

Do we have to know how to derive the rate formulas using the derivative/integration?

jessicahe4Elavelle

Did Lyndon already post his review worksheet for the final? If yes, where can I find it?

jessicahe4Elavelle

I heard from a UA that there will be one question from each unit and then 2 questions that include several topics at the same time.

jessicahe4Elavelle

Lyndon's and Karen's sessions are the best in my opinion!

jessicahe4Elavelle

The general rule is to choose the problems from the chapters we are currently studying. But I am sure that you can email your TA and talk to him/her about it

jessicahe4Elavelle

Endergonic refers to a positive change in Gibbs Free energy while endothermic refers to a positive change in enthalpy.

jessicahe4Elavelle

Do we have to memorize how to draw the galvanic cells?

jessicahe4Elavelle

Are there any tips on balancing redox reactions in acidic AND basic environment?

jessicahe4Elavelle

We got our midterms back yesterday after our lecture ! The TAs handed them back

jessicahe4Elavelle

we are doing redox reactions right now and that falls into Outline 5-Electrochemistry

jessicahe4Elavelle

What are the topics we have to know for our upcoming test ?

jessicahe4Elavelle

the formula for is delta G = delta H - T delta S. So if:
- delta H is positive and delta S is negative, delta G will definitely be positive
- delta H is negative and delta S is positive, delta G will definitely be negative

jessicahe4Elavelle

a bomb calorimeter is an isolated system because no matter or heat can be exchanged through it.

jessicahe4Elavelle

The equation for the work is Pext x change in volume, so if the volume is constant, the change in volume is zero therefore pressure is multiplied by zero which is w=0

jessicahe4Elavelle

All the values of R are in the equation sheet provided to us. To see which R to use, you should check the units, specifically if it uses atm or joules or Torr.

jessicahe4Elavelle

Ronald Thompson 1F wrote:Is there a solutions guide as well?

Lyndon said that he is not going to post any solutions so you should go to his review session in order to get the solutions.

jessicahe4Elavelle

It is always best to draw Lewis structures so that you don't get confused or forget some bonds if you're visualizing structures in your head.

jessicahe4Elavelle

The best way to prepare in my opinion is reading the concepts in the book, understanding the sample problems and finally doing ALL homework problems assigned to us. Practice is key.

jessicahe4Elavelle

The NA represents the number of molecules or atoms in the system, so if there are 2 molecules of C02, for example, the NA would be 2. If you have one mole of CO2, the amount of molecules of CO2 is given by avogadro's number so NA would be Avogadro's number.

jessicahe4Elavelle

If there are an even amount of moles on either side the reaction is unaffected by a change in pressure.

jessicahe4Elavelle

Le chateliers principle applies on to reactions at equilibrium as it determines how a change in the system at equilibrium will affect the direction of the reaction.

jessicahe4Elavelle

Standard enthalpy of reaction is the enthalpy change that occurs in a system for a reaction in which it’s reactants and products are in their standard state.

jessicahe4Elavelle

The only factor that can change the equilibrium constant is temperature. Pressure can not change Equilibrium constant but it changes the direction of the reaction only if the change in pressure was caused by a change in volume because in that case there was a change in concentration.

jessicahe4Elavelle

Only a change in pressure that is caused by a change in volume affects the direction of the reaction because for an increase in volume, for example, causes a decrease in pressure (PV=nRT) and consequently a change in concentration. On the other hand, if the pressure changes because extra inert gases...

jessicahe4Elavelle

No, first and second group cations do not affect pH so we shouldn't take them into account. Also the anions Cl, Br and I do not affect pH.

jessicahe4Elavelle

To distinguish weak acids from strong acids you should just essentially memorize the list of strong acids (they are 7 in total HCl - hydrochloric acid, HNO3 - nitric acid, H2SO4 - sulfuric acid, HBr - hydrobromic acid, HI - hydroiodic acid, HClO4 - perchloric acid and HClO3 - chloric acid). The stro...

jessicahe4Elavelle

Ice tables can be used for both molarity and partial pressure because the concept is basically the same (Initial pressure, change in pressure and equilibrium pressure). For partial pressure you would just use Kp instead of Kw.

jessicahe4Elavelle

I think you might be getting confused because I thought that the ICE and quadratic method was used solely to calculate the pH or pOH of weak acids and bases because for strong ones you just know that they dissociate completely.

jessicahe4Elavelle

No, Ka and Kb are used to calculate the pHs and pOHs of weak acids and bases but we are only working with strong acids and bases that dissociate completely in an aqueous solution.

jessicahe4Elavelle

I think that you should memorize all the strong acids (they are 7: HCl, HBr, HI, HClO3, HClO4, H2SO4, HN03). Strong bases are basically all the metal oxides and metal hydroxides

jessicahe4Elavelle

A cation is a positive ion, so an atom that has lost one or more electrons thus becoming positively charged

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Water is for sure formed only when a strong base is present in the neutralization reaction. In this case ammonia is a weak base.

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Chronium - assists insulin in control of blood sugar
Iron - facilitates electron transfer in the oxidation of carbohydrates, proteins and fats
Cobalt - for Vitamin B12
Manganese, Nickel, Copper and Zinc - critical for enzime function.

jessicahe4Elavelle

For the acids, there are in total 7 strong acids that you should just memorize: HCl, HBr, HI, HNO3, HClO3, HClO4, H2SO4. (so the rest would be weak acids). The strong bases, instead you can recognize them as they are always a metal hydroxide (e.g. LiOH, NaOH, KOH...).

jessicahe4Elavelle

Basically, electrons in an atom fluctuate over time and in one instant electrons may accumulate on one part of a molecule making side of the molecule more negative and leaving the other side more positive, becoming, therefore, an instantaneous dipole. An instantaneous dipole moment on one molecule w...

jessicahe4Elavelle

In the Bronsted definition, an acid is a proton donor while a base is a proton acceptor. In the Lewis definition instead, an acid is an electron acceptor while the base is the electron donor. While the definition may be different, both Lewis and Bronsted pretty much refer to the same thing.

jessicahe4Elavelle

Are we supposed to memorize electronegativity values? I know the general trend but if it asks for example: which pair has the most ionic character between CH4 and CF4, how am I supposed to know the electronegativity difference exactly.

jessicahe4Elavelle

A σ bond has cylindrical symmetry while a π bond has a nodal plane that includes the bond axis.

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Intramolecular forces are harder to break because it would be breaking the actual bonds between atoms. Intermolecular forces are forces between different molecules and include things like London dispersion forces, Van der Waals forces, and dipole-dipole interactions and are easier to break.

jessicahe4Elavelle

Electrons are negatively charged and repulse other electrons. A lone pair causes an area of high electron density so electrons repel each other more strongly than bonding pairs causing a distortion in the shape (lower angle).

jessicahe4Elavelle

The larger the molar mass, the more electrons the atom has. In larger atoms, the valence electrons are farther from the nuclei than in smaller atoms so they are less tightly held and can more easily form temporary dipoles. Also, an atom that has a large cloud of electrons is more easily distorted an...

jessicahe4Elavelle

Yes cations’ polarizing powers depend on the power of its charge. Smaller atoms have their charges more concentrated in a smaller region so their polarizing power is stronger.

jessicahe4Elavelle

Yes, you should draw the Lewis structures first the way we always do it (counting valence electrons and following the octet rule) and see which structures contain single, double or triple bonds. The single bonds have the greatest length followed by double and then triple bonds.

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A coordinate covalent bond is a bond in which one atom provides both electrons in a shared pair for both atoms.

jessicahe4Elavelle

The s-block elements are all located in Group 1 and 2 and they all contain 1 or 2 electrons in their outer shell. They have lower ionization energies so they have the tendency of losing electrons more readily and react with other elements.

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Radicals are molecules that contain one unpaired electron. To answer this question it would be best if you draw the Lewis structures for which one and see which molecule has an unpair electron. You can also identify them by the fact that their number of valence electrons is odd (meaning that at leas...

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Doctor Lavelle says that in these cases we cannot determine directly whether the two atoms will engage in covalent or ionic bonding through that simple rule, and we have to look at the specific cases.

jessicahe4Elavelle

I think we should know on a general level. Just remember that alkali metals are in group 1. Group 2 are the alkaline earth metals, from group 3 to 12 are transition metals and group 17 contains the Halogens.

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The Zeff is the net positive charge that valence electrons experience from the protons in the nucleus. (a) is false because Zeff is largely dependent on the number of electrons in the atom. This is because the electrons in lower energy levels can shield electrons in higher energy orbitals thus decre...

jessicahe4Elavelle

I am attaching my notes from the lecture down below. I hope that helps!

jessicahe4Elavelle

What topics will the test next week (Test 2) cover? Only the Quantum World?

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A friend of mine asked the TA and he said that extra posts do not roll over the following week.

jessicahe4Elavelle

You should keep as many significant figures as possible when doing your calculations (I usually keep at least 6 decimal places) and then round everything at the very end. Hope this helps

jessicahe4Elavelle

I think it is better to say particle model. A photon is basically a quantized particle of light.

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The M is an unidentified metal that you have to find. The problem gives you the molar mass of M(OH)2 so what you have to do is subtract the molar mass of OH2 off of the molar mass of the entire thing to find the metal M. After doing the calculation you will find that the molar mass of the metal is 4...

jessicahe4Elavelle

I think that formula units and molecules are pretty much interchangeable, but formula units refer to ionic compounds like NaCl while molecules refer to molecular compounds. Atoms, instead, are used for single elements or ions.

jessicahe4Elavelle

There are 4 major rules regarding zeros and significant figures. 1. Zeros that are between two non-zero digits are significant. (ex. 303 - 3 significant figures) 2. Leading zeros are not significant. (ex. 0.4 - 1 significant figure) 3. Trailing zeros that are to the right of the decimal are signific...

jessicahe4Elavelle

How do we get the info that the composition of caffeine is c(8)H(10)N(4)O(2)? I thought that that was what we were trying to find.

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