CHEMISTRY COMMUNITY

Ryan Yee 1J

The rate law for a reaction aA -> bB is -(1/a)(d[A]/dt) = (1/b(d[B]/dt) the negative is there for the reactants to express that they are being used up.

Ryan Yee 1J

Thats not to say that it wont ever occur, its just incredibly unlikely. With that said, catalysts or enzymes lowering the activation energy could make it more likely.

Ryan Yee 1J

The rate constant increases with temperature, and the equilibrium constant for an endothermic reaction will increase with increasing temperature and for an exothermic reaction it will decrease with increasing temperature.

Ryan Yee 1J

In the first instance (-d[A]/adt), it measures the rate of the decrease of the reactant, but the second instance (K[R]^n) was determined experimentally. It still shows the reactant decreasing, but this time including the rate constant, K, so that you can write rate as a function of concentration.

Ryan Yee 1J

It seems to just be a difference in notation (at least, thats what I got from page 600). Take k_r to be equal to k.

Ryan Yee 1J

You should know that an ideal gas will follow the equation, PV=nRT, but also that it is a hypothetical gas whose molecules occupy negligible space and have no interactions. It is because of this that they will obey gas laws always.

Ryan Yee 1J

The general rate law is the equation that you have listed, derived from rate=(-1/a)(d[A]/dt)=(1/b)(d[B]/dt) where a and b are stoichiometric coefficients for reactant A and product B. In the equation you mentioned, k is the rate constant, which is determined experimentally, and the concentrations [A...

Ryan Yee 1J

In an adiabatic system, there is no heat transfer between the system and surroundings, so delta q = 0

Ryan Yee 1J

At low temperatures, thermodynamic control is unfavorable. (Think deltaG=deltaH-t(deltaS)) and increasing temperature would put more favor towards thermodynamic control. Additionally, at lower temperatures, the pathway with lower activation energy is favored because more molecules are able to hit th...

Ryan Yee 1J

Since w=p(deltaV), not knowing the volume would mean you cant calculate work. But since U= q + w, given internal energy and enthalpy, you could calculate work.

Ryan Yee 1J

NO is a catalyst, and since it is present at the start and end of the reaction, then it is not written in the expression.

Ryan Yee 1J

So, the collision model is a model that requires reactants to collide with sufficient energy to form products, and an activated complex is the required energy needed to change the reactants to products. Since temperature is a measure of average kinetic energy, the temperature must be high enough for...

Ryan Yee 1J

Rate constants are positive, but the slopes are negative because rate measures the disappearance of reactant (which is why k is negative). In a first order reaction, the negative of the slope is equal to k.

Ryan Yee 1J

Just basic knowledge of calculus for this final, but calculus in general is helpful to understand the derivation of each of the formulas from one another.

Ryan Yee 1J

The entropy of the container with diatoms would be higher because you have to worry about the orientation when looking at microstates. Since they both have 1 mol of atoms, then the container with diatoms has higher entropy.

Ryan Yee 1J

In all of the half life equations for 0th, 1st, and 2nd order rate laws, the rate constant is in the denominator, and so when you increase the rate constant the half life becomes smaller. Alternatively you can think of it as the rate constant increasing leads to a faster reaction meaning that the de...

Ryan Yee 1J

Because they both have the same geometric shape, the orientation due to asymmetry is the biggest contributor to their different entropies, and the asymmetry just also contributes to polarity.

Ryan Yee 1J

For a process to be reversible, there cannot be any change in temperature or pressure in the initial and final states of the system. But since the piston confines the gas and the gas expands, then the system is irreversible because the pressure changes.

Ryan Yee 1J

The logic that I used in selecting B was that answer B had the highest concentration of both acid and base, and the least amount of water. While the B and D had the same number of moles, B had the least amount of water which means that it could change the temperature the greatest.

Ryan Yee 1J

You would make 2 q=(mass)(specific heat)(change in temperature) and then set them equal to each other (since the heat lost by the coffee is gained by the ice). So now you have (mass of ice)(specific heat of ice)(change in temperature) = (mass of coffee [which should just be mass of cup of water beca...

Ryan Yee 1J

The Van't Hoff equation relates the equilibruim constant to standard condition enthalpy and entropy. You can overlap two instances of the Van't Hoff equation to find the change in enthalpy at two different temperatures.

Ryan Yee 1J

It refers to the natural form of the element, so like all the diatomic gases being bonded to themselves (like oxygen or nitrogen), or the metallic elements being by themselves.

Ryan Yee 1J

They pretty much mean the same thing, and that the process it describes is constant volume.

Ryan Yee 1J

Regular calorimeters (the coffee cup) is done at a constant pressure, while bomb calorimeters are done at constant volume.

Ryan Yee 1J

q equals delta H at constant pressure

Ryan Yee 1J

I'd love to hear if anyone has any examples that they found in the book. But which ones has he mentioned during lecture?

Ryan Yee 1J

Well, entropy is joules/(mol*K), but that shouldn't affect the answer that you got. The only thing that I could see possibly wrong is you added 273 instead of 273.15 for Kelvin conversion from celsius. But that shouldn't affect your answer too much.

Ryan Yee 1J

Put product concentration over reactant concentration raised to the powers of their individual stoichiometric coefficients and then solve for K. If your concentrations given aren't at equilibrium, you're going to have to make an ICE box and solve for the concentrations at equilibrium and then put pr...

Ryan Yee 1J

Oxidation numbers are based on how many electrons an atom has. Increase in this number from reactants to products means reduction while decrease in the number is oxidation.

Ryan Yee 1J

In the example from Dr. Lavelle's lecture, the conversion of diamond to graphite is thermodynamically stable, however it isn't kinetically stable, so diamond remains as diamond despite the conversion being thermodynamically favored. Because the conversion isnt kinetically stable, the reaction does n...

Ryan Yee 1J

Logically, a volume expansion would mean that there are technically more microstates for a system to have, and so entropy would increase.

Ryan Yee 1J

In a closed system, energy can be exchanged in and out of the system, but matter can't. So by adding or removing heat, you can change the energy in the system. In an isolated system, nothing can be exchanged and there isn't a way to change the energy within the system.

Ryan Yee 1J

Elementary ones (like ammonia, water, hydroxide, hydronium) should be known, but other than that, Lavelle normally gives us the complex molecule compositions on the test

Ryan Yee 1J

No it won't, but it could help with your understanding of problems on the final.

Ryan Yee 1J

Yes, because of the equation: delta(G) = delta(G0) + RTln(Q) and since we are at equilibrium, Q=K as well as delta(G0) = -RTln(K). So if you plug things back in, you get delta(G) = -RTln(K) + RTln(K) which equals 0

Ryan Yee 1J

Whenever you change the volume of a gas, the temperature must change if you want to keep the pressure the same. An expansion of gas would cause pressure and temperature to decrease and compression of gas would cause the pressure and temperature to increase. To counteract these and keep the pressure ...

Ryan Yee 1J

If you count up the total molecules in these equations, both sides have equal numbers of the required atoms. The 1/2(N2) means that there is only 1 nitrogen atom, and the 3/2(H2) means there are 3 hydrogen atoms, so they both come together to make 1(NH3)

Ryan Yee 1J

The basic anion will cause the dissociated solution to produce OH-. In this case, basic is the opposite of acidic, not taken to mean 'elementary'

Ryan Yee 1J

The more positive value is reduced so that when you subtract the anode's value it'll remain positive

Ryan Yee 1J

I would just use m1v1=m2v2 to find concentration changes with the given variables, but the ideal gas equation should just be used to solve for a missing variable given the others.

Ryan Yee 1J

It's asking for the dissociation constant of the base. Because its pH is greater than 7, the compound is basic. You have to find the Ka, then divide Kw by Ka to find Kb

Ryan Yee 1J

Increasing pressure by decreasing the volume will cause a shift to the side with fewer moles of gas, and decreasing pressure by increasing volume causes a shift to the side with more moles of gas. If you change the pressure by adding an inert gas into the system, then nothing changes.

Ryan Yee 1J

You have to solve for the value of x most of the time, using K values (including Ka or Kb) set equal to the equilibrium expression. From there you can add x to the products and subtract it from reactants to find final concentrations.

Ryan Yee 1J

There isn't a difference, but because the Kw given is in a different temperature, the concentration of both hydronium and hydroxide should be equal so take the square root of 2.1*10^-14 and that both of the concentrations should be equal to 1.4*10^-7

Ryan Yee 1J

Some chemical equations will be given to us, but certain ones, like combustion, you should have memorized in order to make a chemical equation given the combustible material.

Ryan Yee 1J

Since we take the products over reactants raised to their stoichiometric powers, a multiple of the entire equation would cause for an increase in the same number power for each reactant and product. So if we were to multiply that equation's coefficients by 3 then the resulting K would be K^3

Ryan Yee 1J

When pressure is increased it forces gas molecules closer together, so if the gas atoms can form more complex molecules to take up less space (for more movement) then they can.

Ryan Yee 1J

Yes, from what I gathered in the lecture, its only purpose is to specify the states of the reactants and products in an equilibrium equation and what to include in a K or Q calculation for an equation.

Ryan Yee 1J

Adding a catalyst, in this case, would do nothing because the reaction is already at equilibrium. Catalysts only serve to increase the rate of reaction so if the reaction was not at equilibrium then it would just achieve equilibrium quicker than an uncatalyzed reaction.

Ryan Yee 1J

Every problem should have some method of being able to retrieve the other concentrations. If you aren't explicitly given a concentration, you might be able to use partial pressures in conjunction with moles withe the ideal gas equation. It's honestly just a matter of how much you play with the varia...

Ryan Yee 1J

The pentaamine part goes before the sulfato because amine, the base word without prefixes, starts with A. The order that you write them in is alphabetical.

Ryan Yee 1J

Other polydentate ligands include ethylenediamine, which is bidentate, or porphyrins which are tetradentate. You can tell if a ligand is polydentate based off of whether it has lone pairs on separate atoms within the molecule that can fit the electron density shape of tetrahedral, octahedral, or squ...

Ryan Yee 1J

It all depends on what the transition metal is binding to. If it is binding to the Carbon in CN, then use cyanido. If it is binding to the Nitrogen, then use isocyano.

Ryan Yee 1J

To find which oxidation state the transition metal is in a coordinating compound, you need to sum the charges of the ligands and then subtract the total charge of the compound by the total charge of the ligands. So like in [Fe(CN 6 )] 4- the charges of the ligands equals -6 and the total charge is -...

Ryan Yee 1J

In ethene, the carbon has to hybridize its p and s orbitals, so it can create four bonds. My guess is that in order to hybridize, Carbon requires some energy and so it would only create as many hybridized orbitals as it needs. Since, in ethene, it only needs 3 electrons to form sigma bonds, carbon o...

Ryan Yee 1J

Lone pairs should be treated like they are a bond, so diatomic oxygen having a double bond and two lone pairs per oxygen atom (which is what I'm assuming you're referring to) would be linear with sp hybridization, as the lone pair technically counts as a 'bond'

Ryan Yee 1J

A lewis acid is defined by its ability to accept electrons. So since H- cant accept any more electrons, it would be a lewis base because it can donate an electron pair.

Ryan Yee 1J

Well, neutralization reactions between acids and bases always form water and salt, so since you know that water will always be a product, you can write the conjugate bases and acids for the reactants and attempt to combine them. In the first example, the conjugates are K+ and CH3COO-, which you can ...

Ryan Yee 1J

Bronsted acids and bases are defined by their ability to donate/receive protons, respectively. So in this question, the base is HPO₄^2- and its conjugate acid is H₂PO₄^-

Ryan Yee 1J

A ligand can only be polydentate if it can form two different bonds in a coordination compound. Even though oxygen has two lone pairs, it cannot be bidentate because only one of the pairs can bind to the center atom. Take water, for example. Even though the Oxygen has two lone pairs, it is monodenta...

Ryan Yee 1J

Methyl refers to the CH3 group and Amine refers to the NH2 group (think ammonia but not really). For trimethylamine, the tri refers to the number of methyl groups being bound to the nitrogen (named amine).

Ryan Yee 1J

Well, for the purposes of the question, either way that it goes, the concentration of OH- would be high and result in a basic solution, but I would imagine that carbonate would form both of these compounds, since it is a weak acid and not fully dissociated. Because it isn't fully dissociated, HCO3- ...

Ryan Yee 1J

HCl, HNO3, H2SO4, HBr, HI, HClO4, HClO3 are all the strong acids, and strong bases are most of the group one and two elements bound with hydroxide molecules. Alternatively, if you are given a pKa for an acid/base then it is likely weak, as this means that it does not fully dissociate in water and ca...

Ryan Yee 1J

Since pH = -log[H3O+], you could use antilog to go from pKa to Ka, and then use Ka = [H3O+][A−]/[HA] to solve for the H3O+ that you need. Unfortunately, you will need to be given more information in order to solve for pH this way.

Ryan Yee 1J

I don't recall a little 'a' in that equation. pOH = -log[OH-] and pH = -log[H3O+]. You could have miswritten the equation, or gotten it confused with Ka or pKa (in which pKa = -log(Ka) so maybe thats what happened?)

Ryan Yee 1J

I don't think we have to because they were never mentioned in lecture. Arrhenius acids and bases are extremely narrow in terms of their definition, so I think you'll be ok with the definitions of Bronsted and Lewis acids and bases.

Ryan Yee 1J

Ligands can bind at more than one site if they have more than one pair of electrons to bond, but only if the lone pair is on a separate atom. Water is monodentate despite having two sets of lone pairs. It cannot take two binding positions of a transition metal.

Ryan Yee 1J

It can be polydentate when there are multiple spaces for electrons to bind to a metal. You can tell if a chemical will be polydentate if it has multiple lone pairs to act as donating sites for the metals to grab on to. In HN(CH2CH2NH2)2, each of the nitrogens has a lone pair which can be taken by th...

Ryan Yee 1J

You use Bis, Tris, Tetrakis, and Pentakis when the ligand itself has a prefix on it. These new prefixes will help denote how much of a ligand you have whereas the ones already on the ligand denote how much of an element you have within a ligand. This is to help avoid redundancy when naming.

Ryan Yee 1J

The name of this compound is potassium tetra cyano nickelate (II). This is because it is an ion that forms with potassium and the nickelate coordination compound. The (II) refers to the oxidation state of the nickel in the compound and comes from the charge of the nickel. Because the overall charge ...

Ryan Yee 1J

I feel like anything that he mentioned in lecture is fair game for the final, so I would memorize as many structures as possible, or at least how to derive them from their names just in case he throws a curveball.

Ryan Yee 1J

Its shape is trigonal pyramidal, the O-S-Cl bond angles are the same because they're on opposing sides (and chlorine repels itself equally away from itself), and the values for the bond angles are <109.5, because of the lone pair on sulfur pushing down on the bonding elements.

Ryan Yee 1J

https://socratic.org/questions/what-are-the-resonance-structures-for-so-2 According to this website, all three structure are technically true for SO2, because theoretically we would like for Sulfur to have the two double bonds, but experimental data shows that SO2 likely has one double and one singl...

Ryan Yee 1J

It depends which electrons are used for bonding. If the outermost electrons being used are in the 3s and 3p levels, then the sp hybridization will reflect that and be labeled as 3sp(1,2, or 3). Carbon can form 4 2sp3 hybrid orbitals.

Ryan Yee 1J

Ozone is bent, so its bond angle is slightly less than 120 degrees Azide is linear, so its angle is 180 degrees Cyanate is also linear, so its angle is 180 degrees Hydronium's electron density is tetrahedral, so its angle is slightly less than 109.5 because the lone pair on top pushes down on the hy...

Ryan Yee 1J

The roman numeral refers to the oxidation state of the transition metal in question. In your example, Fe's charge is 2+, so you would use iron (II) when naming it. If its charge were to 3+, you would use iron (III).

Ryan Yee 1J

HCO3 - as an acid, HCO3 - (aq) + H2O(l) <--> H3O + (aq) + CO3 2- (aq) This has HCO3 - acting as the acid and CO3 2- acting as the base, and H2O as the base with H3O + as the acid. With HCO3 - as a base, H2O(l) + HCO3 - (aq) <--> H2CO3(aq) + OH - (aq), This has HCO3 - acting as the base and H2CO3 act...

Ryan Yee 1J

Covalent bonds are similar to sharing of electrons, so when atoms share the the correct amount of electrons with another atom, they also technically get the same amount in return. So, triple bonded nitrogen shares three of their existing electrons with one another, and both can fulfill their octet. ...

Ryan Yee 1J

No, the least electronegative atom goes in the center, but in general, when making possible lewis diagrams for the molecule, you would want this central atom to have a formal charge of 0.

Ryan Yee 1J

Normally you can just use the atomic radius between two bonding atoms to find the bond length, but once you get into double and triple bond territory, the attractive forces increase and bond length decreases. In resonant structures, the bond length is somewhere between the bond lengths of all the bo...

Ryan Yee 1J

Fluorine likely does not, but since chlorine is in the n=3 group, it can form double bonds because of the technical presence of d orbitals.

Ryan Yee 1J

In general, metals with less than 4 electrons (the entirety of the s block and sometimes the first column of the p block) tend to form cations because giving up electrons to attain an octet is easier than gaining electrons. They generally form salts with nonmetals which consist of an ionic bond gene...

Ryan Yee 1J

The depiction of resonant structures makes the molecule more stable. If a molecule can have resonant structures, it is more stable for the molecule to have the hybrid characteristic of all the resonant structures.

Ryan Yee 1J

When drawing the lewis structures for ions, you need to separate the ions in order to denote their charge. So for the first problem, NH4 is a cation, while Cl is an anion. To write that they are different charge, you need to separate them in the lewis structure with a bracket and a charge number wit...

Ryan Yee 1J

Dipole moments result from differences in electronegativity. When the differences in electronegativity fail to cancel out (point in opposite directions) then the electronegativity difference in the molecule creates a dipole moment. CCl4 is nonpolar and does not have a dipole moment because each of t...

Ryan Yee 1J

Polarity just depends on the electronegativity difference between two bonding atoms, and dipole moments are created when the electronegativity difference between two bonding atoms is greater on one side of the molecule than the other. For example, CCl4 is nonpolar because all the bonds dipole moment...

Ryan Yee 1J

It all depends on how many valence electrons an element has in relation to an octet. If an element has 3 or less, it becomes easier to form a cation because losing the 3 electrons requires less energy than gaining 5 to get an octet. If it has greater than 5, it'll likely form an anion because gainin...

Ryan Yee 1J

There exists a g subshell, but theres no purpose to it because of the amount of electrons needed to create such an element would be super unstable. (The atom would have to have 121 electrons, to which the element would have a very hard time existing.) Source: https://www.askamathematician.com/2012/0...

Ryan Yee 1J

Wait so like are you talking about an electron from a px orbital approaching one from a py orbital? But just to rationalize things, there is a lot of space occupied by electrons relative to the nucleus, so I'd imagine that they'd still repel each other (because of likened charge) and perhaps this co...

Ryan Yee 1J

Sine and cosine represent the shape of the wave function because they both describe the relationship between an electron's momentum and position. Since you can only know so much about one while sacrificing information about the other, the relationship is cyclical and represented by sine and cosine f...

Ryan Yee 1J

When doing electron configurations, the D block is one n level down compared to the other blocks. So when writing increasing electron configurations from argon to potassium and calcium, the newest electrons that you add go to the S and P blocks at the n=4 level, but once you get to scandium the next...

Ryan Yee 1J

All of these ions have a full shell, so its only a matter of how much greater the charge of the nucleus is compared to the amount of electrons. P3- has the largest atomic radius because there is not as much of a difference in charge to hold the same number of electrons, S2- has the second largest an...

Ryan Yee 1J

The diffraction patterns arose because of measuring constructive and deconstructive interference when waves were passed through two holes in a barrier. These holes allow for the wave to interact with itself and produce the constructive and deconstructive interference patterns which can be measured t...

Ryan Yee 1J

Quantum numbers are as follows: n can be any integer as a principle electron shell, it cannot be 0; l is the angular momentum quantum number, it can take any values from 0 to (n-1); ml is the magnetic quantum number and can take any number between -l and +l; lastly ms is the electron spin quantum nu...

Ryan Yee 1J

Since this equation applies to light, it would be J/photon.

Ryan Yee 1J

To my understanding, increasing energy per photon increases the frequency and decreases the wavelength for light. This energy per photon is what allows electrons to surpass the threshold energy and increase an energy level. Increasing the number of photons with insufficient energy only increases the...

Ryan Yee 1J

First convert MHz to Hz by multiplying by 10^6, then plug the new frequency into the equation c=(wavelength)(frequency), where c is the speed of light. Then divide by frequency to isolate wavelength.

Ryan Yee 1J

So the metal hydroxide just basically means that the metal 'M' is combined with two hydroxide ions (OH - )2. You want to find the sulfide of this ion, or what the molar mass would be when combined with an S 2- . Taking away the molar mass of hydroxide would mean subtracting 2(17.01) from the origina...

Ryan Yee 1J

Given the molecular formula, find the atomic weights listed under the element in the periodic table. Multiply the element's weight by the appropriate subscript and then add all the weights together. This will give you the molecular weight of a mole of the molecule, and thus its molar mass. You then ...

Ryan Yee 1J

I'd answer in terms of the given information. However, should the number of grams become very large (say 6-7 digits +) I might convert to kilograms. Moles should always be left either as is, or in scientific notation in my opinion.

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