CHEMISTRY COMMUNITY

Edmund Zhi 2B

thank you dr lavelle!

Edmund Zhi 2B

Reaction intermediates are formed but are consumed later on to produce the actual products and are therefore not part of the net overall reaction

Edmund Zhi 2B

A lot of questions don't give us the value of A how do we go about calculating it or is it not necessary?

Edmund Zhi 2B

I believe that coefficients determine the order of reactants in the rate law when we are dealing with elementary reactions. Elementary reactions are when chemical species react directly to form products with a single reaction step and single transition state. I believe this is correct, yes. They ar...

Edmund Zhi 2B

I thought coordination compounds were cool

Edmund Zhi 2B

We are not being asked to find both the forward and reverse, we are only being asked to find the rate for the formation of NOBr, which is the forward reaction.

Edmund Zhi 2B

A certain beta blocker is eliminated in a first-order process with a rate constant of 7.6 * 10^-3 min^-1 at normal body temperature (37 C). A patient is given 20. mg of the drug. What mass of the drug remains in the body 5.0 h after administration? How do we use the integrated rate law/rate low to f...

Edmund Zhi 2B

If you're talking about k as in the initial rate, increasing temperature increases k because it increases the movement of the molecules and causes them to interact and collide more frequently.

Edmund Zhi 2B

The differences are just the effect that the concentration of one reactant has on the overall reactant rate, that is, whether or not a change in concentration will have no effect on the rate, have a linear change, or cause a squared rate of change

Edmund Zhi 2B

They are simply the same notation

Edmund Zhi 2B

The order of reactions are determined by comparing different experiments. By keeping all but one reactant constant, you can determine the order of the varying reactant by seeing it's effect on the initial rate.

Edmund Zhi 2B

Using either would be ok, right? As long as we use the correct constants (ex 0.025693/n vs 0.0592/n)

Edmund Zhi 2B

We are given 1.0M Ni2+ in one solution, and I have calculated that 6.5 x 10*-12 M of Ni2+ is in the other compartment. How do I determine which is the anode and which is the cathode?

Edmund Zhi 2B

When we include partial pressures in the value of Q, why do they have to be in atmospheres? For example, in Question 5N.3 (c), we are given 250torr and 125 torr but the answer key divides them by 760 to convert to atm.

Edmund Zhi 2B

705121606 wrote:I also had trouble with this one, I read on another chemistry community question that when the ecell is negative we have to flip the cell around

Update: I looked at the solutions manual and they did consider the cell to be flipped. Guess the textbook is wrong

Edmund Zhi 2B

In this question, we are given M(s)|M2+(aq)||Cu^2+(aq)|Cu(s) as the cell diagram and are asked to find E(M2+/M) given E(cell) = -0.689. Now normally, we would consider the right side to be the cathode, right? So in that case, we setup the equation to as E(cell) = E(cathode) - E(anode) -0.689 = 0.337...

Edmund Zhi 2B

I'm just curious as why Li is a stronger reducing agent than K, which is a stronger reducing agent than Na (I know based off the half-reaction cell potentials). Why isn't it the other way around if there is more shielding in the lower alkalines and they become more likely to be oxidized, lose an ele...

Edmund Zhi 2B

For part a, we are given

2NO3- + 8H+ + 6Hg -> 3Hg2 2+ + 2NO + 4H2O.

In the answer key's cell, they do not include NO at all, instead, they include NO3- and O in the cathode. Why is this?

Edmund Zhi 2B

Are we supposed to ignore coefficients and balancing everything when we calculate cell potentials? If so why?

Edmund Zhi 2B

According to the textbook, "In general, the more positive the standard potential, the more strongly oxidizing is the oxidizing member of the redox couple and the more likely that member will be to undergo reduction itself." Does this mean that when given two half reactions, we put the more...

Edmund Zhi 2B

Delta G is dependent on other variables, where as ΔG°is a fixed value, where the fixed values are at standard conditions.

Edmund Zhi 2B

In the anode, we are given O2(g) and H+(aq) in contact with each other. I'm confused as to why we put O2 and H+ on the same side of the half reaction...can someone explain how do we determine the half-reaction for these types of problems?

Edmund Zhi 2B

What are different causes of a galvanic cell reaching a voltage of 0?

Edmund Zhi 2B

So then are values of E just relative to the value determined by the half reaction involving hydrogen?

Edmund Zhi 2B

In compounds with only one element the oxidation number is 0

Edmund Zhi 2B

Use common oxidations states such as that of very electronegative atoms like oxygen, nitrogen, and fluorine, and then fill in the rest to make sure that the charges add up to the overall charge of the molecule

Edmund Zhi 2B

Aren't work (w) and heat (q) the only path functions? Can't we just think about that instead of trying to remember all the state functions?

Edmund Zhi 2B

This situation would probably never happen because it's not possible to add heat and have no change in pressure or volume.

Edmund Zhi 2B

Are we required to know this for the exam? I don't see it in our learning objectives but there have been homework problems on it

Edmund Zhi 2B

Hydrochloric acid oxidizes zinc metal in a reaction that produces hydrogen gas and chloride ions. A piece of zinc metal of mass 8.5 g is dropped into an apparatus containing 800.0 mL of 0.500 m HCl(aq). If the initial temperature of the hydrochloric acid solution is 25C, what is the final temperatur...

Edmund Zhi 2B

Why do we use fractions when writing balanced equations for these questions involving Gibbs free energy and formation? These coefficients affect answers and calculations greatly and I was wondering if using answers that we calculated using a different balanced equation is still acceptable (homework ...

Edmund Zhi 2B

We aren't required to know the second equation for the midterm; this is covered in chapter 5, which Lavelle hasn't gone over yet

Edmund Zhi 2B

Just make sure that in calculations, if you end up with L * atm, multiply it by a conversion to joules. It's 101.3 I believe

Edmund Zhi 2B

Basically we need to know all of chapter 4. The concepts he hasn't covered are all part of chapter 5.

Edmund Zhi 2B

We are asked to find which has higher molar entropy, NH3 or Ne. Why is the answer NH3 even though Ne has a higher molar mass, and heavier molecules have more entropy. I suspect it might be because NH3 is more complex, but then, which characteristic of molecules do we look at first when determining w...

Edmund Zhi 2B

In different problems I have to let deltaS = deltaH/T, or -deltaH/T. What is the difference between positive and negative delta H and how do I conceptualize it? Does it have to do with which viewpoint you're taking, the system or surroundings? How do I tell?

Edmund Zhi 2B

I know that Cp = Cv + nR, and for monoatomic ideal gases that Cv = 3/2R, but I'm struggling to understand WHY this is so. Why is a change in entropy based on change in temperature at a constant pressure GREATER than entropy change at constant volume. Can someone please help me understand this concep...

Edmund Zhi 2B

I think you mean "change in entropy." The reason why entropy is always increasing in the universe is because of the big bang theory and how the universe is always expanding, and therefore occupying a forever increasing number of possible states.

Edmund Zhi 2B

You might be struggling because we haven't gone over too many practice problems in class. If your TA is able to provide practice problems, or when Lavelle goes over some in class once thermochem and thermodynamics are completely covered, I think you'll have more of an understanding of how to do ever...

Edmund Zhi 2B

When substances change phases, their specific heats also change. If this is water, for example, the specific heats of water and steam are different and therefore need to be calculated separately and then added together for total heat added.

Edmund Zhi 2B

I actually got the same thing as the answer key. At first, I was getting the same things as you were. If I am correct, you're using 7/2R, and then 5/2R, following the example 4C.1 on page 266. However, these values of Cv,m and Cp,m are for a diatomic gas, Kr in the question is a monoatomic gas. Ther...

Edmund Zhi 2B

Moreover, Cv,m is 3/2R for a monoatomic gas (this is for part B)

Edmund Zhi 2B

For part a, I believe it's 343K for the final temperature and 935.1J for the change in enthalpy, and part b it's 374K for the final temperature and 947.6J for the change in enthalpy. Wouldn't the change in enthalpy just be 765J because in example 4C.1 on page 266, the solution states that "the...

Edmund Zhi 2B

Which gas has the higher molar heat capacity, NO or NO2?

How are we supposed to know this/figure this out, and where in the textbook does it talk about this or are we supposed to apply other concepts from other units?

Edmund Zhi 2B

An insulated water bottle can be considered isolated because neither matter nor energy can be exchanged with the surroundings

Edmund Zhi 2B

The R constant will vary based on the other units given to us within a problem. Our formula sheet should always have a value of R that we will need to use in any problem on an exam.

Edmund Zhi 2B

Freezing is exothermic yes

Edmund Zhi 2B

Calculate the pH of 0.15 m H2SO4(aq). Here is my work for this problem: 0.15M H2SO4 generates 0.15M H3O+ (to be added in later in the problem) and 0.15M HSO4-. Ka of HSO4- is 1.2 * 10^-2 1.2 * 10^-2 = x^2/(0.15-x) 0 = x^2 + 0.012x -0.0018, used quadratic equation to solve for x = [H3O+] = 0.0368 Add...

Edmund Zhi 2B

You write the equation as [Al(H2O)6]3+ + H2O <-> [Al(H2O5)OH]2+ + H3O+. A proton leaves one of the water molecules surrounding the Aluminum and is transferred to another water molecule not attached to the Al. That's why I wrote the compound on the right as [Al(H2O5)OH]2+, to show where the proton wa...

Edmund Zhi 2B

For part D on this problem, where we are asked to find the pH, pOH, and percentage protonation of 0.0073 M codeine given that the pKa of its conjugate acid is 8.21, I'm getting the correct answer for pH and pOH, 3.96 and 10.04, but I'm getting a percentage of 1.5% instead of the answer key's 2.5%. I...

Edmund Zhi 2B

I am getting 3.2 x 10^-15 as well, I believe there is an error in the answer key

Edmund Zhi 2B

I ran into the same problem as well but I don't think anything in the 5E.1 table is meant to help us with the problem?

Edmund Zhi 2B

Adding X atoms would cause more reactants to form to relieve stress on the equilibrium from an increase in products, but in the image there are actually less X2 molecules in container 2, so that answer is incorrect.

Edmund Zhi 2B

For part b on homework 5J.11, we are given reactoin X2(g) <-> 2X(g), where x is a halogen and we want to find out if the reaction will shift left or right with a temperature increase. How do we know? Where in the book can we read about this?

Edmund Zhi 2B

I like to think of this mathematically in terms of the equilibrium constant. Because a number in the denominator is decreasing, O2, which is also in the denominator, must increase to compensate for this to maintain the same K.

Edmund Zhi 2B

Also having trouble with this problem. I follow your work until you plug into the Kc formula. Could you explain how you solved for x? Could you also explain why you omitted the x variable in the denominator with 0.06? I didn't mean to omit it; there should be an x variable there. I solved for x by ...

Edmund Zhi 2B

Ok, I realized that I was dividing by the wrong number and I got the same answers as the book. However, I came up with 2 different values of x: 0.0423, and 0.0189. These numbers are both positive, so how do I determine which one to use? The book uses 0.0189 EDIT: I think I figured it out, it's becau...

Edmund Zhi 2B

I've set up an ice table so that the equilibrium concentrations are as follows: [SO2] = 0.02M - x [NO2] = 0.04M - x [NO] = 0.02 + x [SO3] = 0.03 + x And I've set up the equilibrium concentration as Kc = [NO][SO3]/[SO2][NO2], and letting these equal 85. My expanded equation for Kc is (x^2 + 0.05x + 0...

Edmund Zhi 2B

Another way to derive the meaning is to think about the actual formula of K, [products]/[reactants]. If K is high (greater than 10^3), this means that [products] is a greater value than [reactants] and thus a large K means that equilibrium lies on the right, the side of the products. Same concept ap...

Edmund Zhi 2B

Yup, it is a ratio!

Edmund Zhi 2B

There are different values and units that will vary based on the units of the other variables given in a certain equation. We will probably get these on the formula sheet just like lavelle's 14a

Edmund Zhi 2B

I believe you should look at the states of matter and try and determine from that

Edmund Zhi 2B

Pure substances do not have concentrations and do not impact equilibrium constants because they have no concentration that changes in the reaction

Edmund Zhi 2B

It is consistent with the short reasoning. The short reasoning is just a simplified version of the true complex explanation that he showed in class. The short reasoning was used in high school to introduce us to the concept

Edmund Zhi 2B

BrO- is more likely to pick up a hydrogen because it is the conjugate base of a weak acid and equilibrium will be more likely to lie the left. This makes it a STRONGER base than C17H19O3N since it is considered a weak base and is not too likely (but still can) pick up a proton with the lone pair on ...

Edmund Zhi 2B

You should also know that hemoglobin is mostly used for oxygen transport, while myoglobin is used mostly for oxygen storage.

Edmund Zhi 2B

In the reaction, H2O2 + SO3 -> H2SO5, how do you identify which one is the lewis acid and which one is the lewis base? I know what the definitions are, but how do you determine which of the reactions is the electron "donor" and which one is the "acceptor" since they merge into on...

Edmund Zhi 2B

The reason why we use electronegativity to determine that HClO is a stronger acid than HBrO is because the hydrogen isn't bonded to the halogen, it's bonded to the oxygen. Now, considering electronegativity, we see that the more electronegative atom will delocalize the electrons/charge more, causing...

Edmund Zhi 2B

I got an answer that is different from the textbook as well and is the same as the ones you all got. I've checked my work multiple times. Maybe there's an error in the solutions?

Edmund Zhi 2B

Sara Richmond 1D wrote:What specific biological examples would we know for the final? And what should we know about them?

Box 9C.1 in the textbook may have examples that we could be tested on.

Edmund Zhi 2B

Why do we sometimes use Ferrate in the name and sometimes use Iron? How do we distinguish between the two?

Edmund Zhi 2B

They are sort of opposites of each other.

Edmund Zhi 2B

Are we going to have to apply this knowledge for the final or do we just have to memorize it?

Edmund Zhi 2B

HCl is larger and less electronegative than HF. The bond length is therefore longer and less strong, and easier to dissociate in water, where as the H and F are very tightly bonded in H-F

Edmund Zhi 2B

Yes because water is amphoteric and you would have to look at what it's reacting with

Edmund Zhi 2B

Yes I believe so because you have to know that these have 100% dissociation rate, any other acid we would probably be given the dissociation rates in the problem

Edmund Zhi 2B

In cis molecules, different side groups are on the same side. In trans molecules, the side groups are on opposite sides, like a trans plane. These exist in compounds with a double bond, which can't rotate.

Edmund Zhi 2B

Argon's more electrons can potentially form stronger London dispersion forces than the fewer electrons in Neon

Edmund Zhi 2B

Can someone clarify what coordination compounds are and why they are important/exist?

Edmund Zhi 2B

For I3- ,why is the VSEPR formula X2E3 and not AX2E3? Would saying the latter be incorrect?

Edmund Zhi 2B

The three lone pairs are actually able to hang around the equator of the molecule, forming a triangle. The other two I atoms can form a 180 degree angle around the axial plane, minimizing repulsion between them.

Edmund Zhi 2B

In atoms such as CH2F2, where not all the atoms surrounding the central atom are the same, how are bond angles affected? Are they all still about 109.5 degrees or does the greater size of fluorine repel the hydrogens a little bit? If so, which bond angle is greater? H-C-F, H-C-H, or F-C-F? How do we...

Edmund Zhi 2B

Hydrogen bonding is not the bond between hydrogen and another atom. It is the bond that occurs due to a difference in dipole moments between a partial positive hydrogen and a partial negative N, O, or F.

Edmund Zhi 2B

Having a lone pair has a greater effect on repulsion because if you think about it, only one atom will be fighting for electrons, where as if there was a bond, two atoms would be exhibiting a nuclear force on the electrons. This means that the lone pair will be pulled closer to the nucleus, and the ...

Edmund Zhi 2B

We haven't gone over molecules with lone pairs yet. But in H2O, there are 4 regions of electrons. The two lone pairs repel the bonding pairs and the shape is actually bent.

Edmund Zhi 2B

Can someone please explain why AsF3 has a boiling point of 63C while AsF5 has a boiling point of -53C?

Edmund Zhi 2B

Can someone please explain why CHI3 has a higher melting point than CHF3?

Edmund Zhi 2B

I think the numbers that Lavelle gave in lectures are just averages or typical values to give us an idea of relative strengths. Keep in mind that these numbers are experimentally determined.

Edmund Zhi 2B

Molecules are more polar than other molecules when the differences in electronegativity are greater. For example, C-H is a less polar bond than O-H.

Edmund Zhi 2B

Number of bonds shouldn't be what you're looking at, it should be the differences in electronegativity.

Edmund Zhi 2B

In our lesson about the wave properties of electrons, we learned that electrons passing through a crystal also show diffraction patterns, indicating that electrons exhibit wave characteristics too, just like light. However, we never applied this to protons and neutrons, and in the audio-visual focus...

Edmund Zhi 2B

On the audio-focus visual assessments, there are a lot of questions asking about the specifics of the experiment itself, like its purpose and stuff about its conditions (ex whether or not it needs to be done on a vacuum). Will we have to know these specifics for the midterm because the problems from...

Edmund Zhi 2B

Asking this question is like asking why the elements in the 2p block don't use 3s for expanded octets. But what you're saying does make sense, and I am equally as confused. I think we are supposed to focus on this part of the definition of the expanded valence model: that there are EMPTY d orbitals ...

Edmund Zhi 2B

Elements such as Oxygen and Fluorine in the upper right hand corner of the periodic table exhibit high electronegativity because 1) Basically, they are really close to filling their valence shell (the 2p orbitals) 2) Increased electrostatic attraction to the nucleus due to more protons than the elem...

Edmund Zhi 2B

Does the sum of all the formal charges on individual atoms in a compound (the most stable version) ALWAYS equal the actual charge on the entire compound? Like in periodate, where the formal charges on all the oxygens are -1, and the central iodine has a charge of +3, making the sum of the formal cha...

Edmund Zhi 2B

Keep in mind the difference between Formal Charge versus oxidation states. What formal charge attempts to do is determine the lowest possible energy configuration for a covalent compound. That is, the most stable. If you're thinking about oxidation states, it is an exaggeration of a charge in a mole...

Edmund Zhi 2B

You could think of resonance structures as the underlying idea behind molecules, resonance hybrids are what occur in actuality

Edmund Zhi 2B

The charge on a molecule is determined by counting the number of electrons that are actually in the compound and then subtracting the sums of all the valence electrons of the individual atoms.

Edmund Zhi 2B

I have found that two versions of the lewis structure have formal charges close to 0. In one, I have Bromine double bonded to an Oxygen atom (this means that Bromine has expanded its octet into the d orbital) with 6 valence electrons on Bromine and 4 on Oxygen. I believe I have done everything right...

Edmund Zhi 2B

You could also take a look at the formal charges (after making sure all electrons are there) and find that they would not be close to 0. The most optimal lewis structures have formal charges close to 0.

Search found 118 matches