CHEMISTRY COMMUNITY

Vuong_2F

So an aqueous solution isn't considered a liquid? Yes, they are different. To sum it up, you would omit a species from the equilibrium expression if it's in a solid(s) or pure liquid (l) state. If they are in an aqueous (aq) or gas (g) state, then you would include the species in the equilibrium ex...

Vuong_2F

the notation for cell diagrams is (anode) II (cathode), and I've heard some TAs say that on each side it should be written as reactant/product but in reality, there's kind of inconsistencies with the order in which they are written. so just assume that the species on the left are being oxidized and ...

Vuong_2F

when there is no conducting solid in reactants or products, add platinum as a common inert conductor

Vuong_2F

Why is that? Why is the anode reaction reversed? i believe it is because when you are given two equations and their potential values, it is the standard reduction potential values for both. therefore for the anode cell reaction where oxidation is taking place, you must reverse it to account for the...

Vuong_2F

You can identify a zero order reaction by looking at experimental data or looking at the graph, which should yield a linear line for the plot of [A] vs time

Vuong_2F

a zero order reaction graph of [A] v. time would turn out to be a negative slope linear line

Vuong_2F

0 order indicates that the rate of reaction is independent of the concentration of the reactants

Vuong_2F

is there any significance in knowing the difference between a homogeneous and a heterogeneous catalyst?

Vuong_2F

how does changing temperature affect the reaction constant?

Vuong_2F

what's the difference between a catalyst and an intermediate?

Vuong_2F

how can determine if a species is a catalyst?

Vuong_2F

605395381 wrote:k is unit-less because it is a ration of concentrations of products and reactants

thanks for all the answers everyone but i forgot to clarify in my original question that i'm referring to the k that is in rate laws. i thought that k in the context of kinetics had units?

Vuong_2F

for 6L.5b, why is there platinum added to the reaction I-(aq) --> I2(s) ? i thought inert conductors were only needed when there is no conducting solid or liquid in the reaction. what constitutes a 'conducting' solid?

Vuong_2F

what factors can affect the value of k?

Vuong_2F

how do you derive the integrated rate law?

Vuong_2F

what are the units of k?

Vuong_2F

how is electrochemistry applicable in biology? please give examples!

Vuong_2F

how would you derive the nernst equation?

Vuong_2F

how would you predict if a metal will dissolve in a solution? (it's one of the bullet points in the outline)

Vuong_2F

Eugene Chung 3F wrote:the deltaG for a cell is the amount of useful work obtainable from a system at constant T and P.

thanks for your answer! how is work related to cell potential though?

Vuong_2F

i have written in my notes from wednesday (feb 26), that for the following reaction 2NO2 --> 2NO + O2 , the differential rate equation -½ d[NO2]/dt = ½ d[NO]/dt = d[O2]/dt is preferred over d[NO2]/dt = d[NO]/dt = 2d[O2]/dt

can someone explain why the first one is preferred over the latter?

Vuong_2F

how exactly do ions move across the salt bridge? why is a salt bridge and the movement of ions necessary in the first place?

Vuong_2F

Eugene Chung 3F wrote:electrons will flow from area of high concentration to an area of low concentration. So, the concentration difference makes potential.

so once there is no concentration difference, there is no more potential?

Vuong_2F

according to the textbook, the standard E cell is defined through deltaG(standard) = -n*F*E(cell, standard) where deltaG(standard) is defined as the difference of the molar Gibbs free energies of the products and reactants all in their standard states (all gases at 1 bar, all participating solutes a...

Vuong_2F

how would you calculate pH using the nernst equation?

Vuong_2F

how do the concentrations change as current flows from anode to cathode?

Vuong_2F

how is work related to free energy or cell potentials?

Vuong_2F

how come when you multiply a chemical equation, the gibbs free energy changes but the standard potential remains unaffected?

Vuong_2F

in which direction are electrons and ions flowing with respect to the anode/cathode? why are the ions moving in the direction that they are moving?

Vuong_2F

when is platinum used as an inert conductor? during lecture, he mentioned that there were other inert conductors, do we need to know them? also how come sometimes it's only added on one side of the cell diagram and other times it's on both sides?

Vuong_2F

why are commas used sometimes instead of the normal vertical lines?

Vuong_2F

if the direct value of the standard potential for a specific equation isn't given, how would you calculate it indirectly?

Vuong_2F

what's the step-by-step for making a cell diagram? what are the usually the trickiest questions they can ask us about this?

Vuong_2F

Can someone explain how to solve #11 on the practice questions? What steps do you need to take? 1) since you're dealing with an acid, you want to convert the pKb to Ka 2) given the concentration of the acid, you can set up an ice table to help you write the equilibrium expression 3) after setting u...

Vuong_2F

I also can't get the answer for q and w; it seems like he subtracted 23.3 and 9.12 to get 14.2, but I don't understand why you wouldn't add the work values you get for each part of the problem together instead. Edit: it seems that work will be positive if the system is being compressed, like in the...

Vuong_2F

what’s a state function?

Vuong_2F

what’s the difference between intensive and extensive properties? what are some examples of them?

Vuong_2F

what are some examples of closed versus isolated systems??

Vuong_2F

how would you calculate enthalpy if the pressure isn’t constant?

Vuong_2F

can someone explain what enthalpy is?

Vuong_2F

Method 2 that Lavelle went over in class, aka the one that uses bond enthalpies to calculate the enthalpy.

Vuong_2F

Hess's Law states that regardless of the multiple stages or steps of a reaction, the total enthalpy change for the reaction is the sum of all changes (demonstrating that enthalpy is a state function).

Vuong_2F

One of the bullet points on the outline says "Define the standard state of a substance and recognize when a substance is in its standard state." How exactly would you know whether a substance is in its standard state or not.

Vuong_2F

Hi can someone please summarize how to use Method 2? Also, will there ever really be a case where only Method 2 is applicable (would Lavelle test us on this method specifically)?

Vuong_2F

For reactions where substances are not in their most stable/standard phase, how would you account for that when calculating enthalpies?

Vuong_2F

Correct me if I'm wrong but I think it's because they are gases, not aqueous.

Vuong_2F

You typically use this principle if there is a scenario where equilibrium conditions are disturbed (whether it be by temperature, pressure, etc). Applying the principle will help you determine the effect of the change.

Vuong_2F

chari_maya 3B wrote:How do you convert from Kc to Kp?

Lavelle hasn't mentioned anything about this in lecture so I'm not sure if this is necessary information, but the relationship between the two is Kp=Kc(RT)^Δn

Vuong_2F

Kc is the equilibrium constant when it's found using concentrations, while Kp is the equilibrium constant when it's found using partial pressures.

Vuong_2F

ICE tables show the concentrations of reactants and products at different points in a chemical reaction. We usually use ICE tables to determine the K of the reaction. I stands for initial concentration, C stands for change in concentration, and E stands for equilibrium concentration. Once you fill o...

Vuong_2F

How does carbon dioxide lead to respiratory acidosis?

Vuong_2F

sarahsalama1G wrote:Additionally, has anyone been able to find the acid rain problems in the textbook?

Someone on another post said H.13, Focus 3 3.69, Example 5G.2, Box 6E.1 all mention acid rain/have practice problems for acid rain.

Vuong_2F

Cisplatin is one biological example of how coordination compounds are relevant. But I believe we should also know the biological functions of Cr, Fe, Co, Mn, Ni, Cu, Zn. The outline for this unit mentions knowing that Co functions in vitamin B12 specifically. What is the biological function of vita...

Vuong_2F

I think the best way to approach this if you are having difficulty is to memorize the common polydentates like oxalate and ethylenediamine. What are the common polydentates that we need to know? The ones listed in the textbook are ethylenediamine (en), diethylenetriamine (dien), oxalato (ox), and e...

Vuong_2F

Can someone give examples for how to apply these roots when naming complexes?

Vuong_2F

I think it would be fair to say that we should the common strong acids and the trend for the strong bases.

Vuong_2F

Neutralization always forms water and, in most cases, a salt.

Vuong_2F

Yes, that's just the rule. The cation has the same name as its element and the anion will have the suffix -ide.

Vuong_2F

I don't think there is a relationship between the two, and if there were, I don't believe Lavelle has mentioned it so you don't need to worry about it.

Vuong_2F

That's all there is to it, the coordination number is the number of ligands attached to the central atom.

Vuong_2F

005162520 wrote:Why are sigma and pi bonds relevant?

They are used to predict the behavior of molecules in molecular orbital theory.

Vuong_2F

Nathan Rothschild_3D wrote:How do you tell ML again and can someone explain what it is?

ML is the magnetic quantum number (it indicates which orbital the electron is in). It depends on the angular momentum quantum number, or L. Valid values for ML are -L, .. 0, .. L.

Vuong_2F

905289082 wrote:What is the relevance of having a sigma vs. a pi bond? is there an effect on bond strength and energy?

They are used to predict the behavior of molecules in molecular orbital theory. In general, sigma bonds are stronger than pi bonds simply because there is more overlap.

Vuong_2F

Nathan Rothschild_3D wrote:If a lone pair is a radical would it have a weaker repulsion than a complete lone pair?

I'm assuming so because a radical would occupy less space than a complete lone pair. Please correct me if I'm wrong though!

Vuong_2F

KTran 1I wrote:Will we need to have the specific bond angles for each molecular shape memorized for Test 2?

Yes you do.

Vuong_2F

I still don't fully understand. If you're going horizontally across a row does atomic radius increase or decrease? And how about going down a column? Going horizontally across a period, the radius decreases. Going vertically down a column, the radius increases. The vertical trend plays a dominant r...

Vuong_2F

A regular covalent bond is when two atoms both contribute one of their electrons to the bond. A coordinate covalent bond is when only one of the atoms is contributing the electrons to the bond. One example is carbon monoxide (CO) where two of its bonds are regular covalent, but the third is a coordi...

Vuong_2F

I believe cancelling out has to do with the symmetry of a molecule. For example C2Cl4 has no net dipole moment because the molecule is symmetric so the moment cancels out When you say symmetric what does that exactly refer too, perhaps the shape of the element? Yes, if you draw out the molecule, yo...

Vuong_2F

Charge and size of the ions in a compound can affect its lattice energy: increases in charge and size both lead to an increase in lattice energy.

Vuong_2F

Test 2 is cumulative only for material covered after the midterm.

Vuong_2F

The larger the molecule, the larger the electron clouds will be, which allows for a stronger temporary dipole and greater London dispersion forces.

Vuong_2F

Jasmine 3L wrote:I don't really understand this too. Like how does it relate to melting and boiling point?

Polarizability determines the strength of the bonds. The stronger the bonds, the more energy is required for a change in state (from solid to liquid or liquid to gas).

Vuong_2F

Try searching up bond angle charts! First determine the VSEPR structure then you can find out what angle the bonds are at.

Vuong_2F

Be is the central atom and the two Br atoms are placed symmetrically around Be, therefore the molecule is nonpolar.

Vuong_2F

So if there is more than one Lewis structure with formal charge of 0, are they considered resonant?

Vuong_2F

The number is front of the letter is the principal quantum number, n. For your orbital angular momentum number (l), the letters correspond to a value. s=0, d=1, p=2, and f=3.

Vuong_2F

Why are s-block metals typically more reactive than p-block metals?

Vuong_2F

a) magnesium has a charge of +2 and arsenic has a charge of -3. Therefore, you will need 3 of Mg and 2 of As to balance out the charges, which gives you the formula Mg_{3}{As_{2}} b) The charge of indium is given as (III), or +3, and sulfur has a charge of -2. Therefore, you will have the formula In...

Vuong_2F

They don't necessarily contribute to Lewis structures but you can look at your Lewis structure to determine what bonds you have. The first bond is always a sigma bond, and any bonds added after that are generally pi bonds.

Vuong_2F

Not sure if this is what you're looking for but...

c = $\lambda$ $\nu$
E(photon) = h $\nu$
$\frac{1}{2}$ m* $v^{2}$ = E(photon) - $\phi$
$\lambda$ = h/p

Vuong_2F

Positive is represented by an up arrow, which means that it's spinning counterclockwise. Negative is represented by a down arrow, which means that it's spinning clockwise.

Vuong_2F

The following are some that are isoelectronic to the H atom: He+, Li2+, Be3+ and B4+.

Vuong_2F

Pauli exclusion states that no orbital can have more than 2 electrons. For example, if the 1s orbital was filled with 2 electrons then you cannot add another one to it, you would have to go to the next orbital, which is 2s. In addition to that, two electrons in the same orbital must have different s...

Vuong_2F

The textbook goes over this in F.6. Do we need to know this? If we do, can someone explain the concept more clearly?

Vuong_2F

Why is the second (and third and fourth, etc) ionization energy usually so much larger than the first one?

Vuong_2F

It depends on the speed the electron is traveling at. You can calculate the wavelength using De Broglie's equation (h/mv).

Vuong_2F

The waves are "in phase," so that the amplitude of the resulting wave is equal to the sum of the individual amplitudes of the original waves

Vuong_2F

According to the class constants and equations sheet:
Mass of electron = 9.109383 * 10^-31 kg
Mass of neutron = 1.674927 * 10^-27 kg
Mass of proton = 1.672622 * 10^-27 kg

Vuong_2F

The question is: In the spectrum of atomic hydrogen, several ines are generally classified together as belonging to a series (for example, Balmer series or Lyman series). What is common to the lines within a series that makes grouping them together logical? I know that the Balmer series is visible l...

Vuong_2F

^ Because 10^-38 is a smaller value than 10^-15, therefore it is not measurable.

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