CHEMISTRY COMMUNITY

reva_bajjuri

does anyone know if there is an error in the answer for this problem? I found the Ecell value to be -0.52v and the solution has it to be -.50v. The solution shows the anode and cathode electrode potentials to be .27 and -.79, respectively, but it adds them to get -.50. If there is an error, can some...

reva_bajjuri

Or could someone just explain why you base your half reactions on the reverse solubility reaction (Ag+(aq)+Br-(aq)->AgBr(s))

reva_bajjuri

6L.7 Write the half-reactions and devise a galvanic cell (write a cell diagram) to study each of the following reactions:

(a) AgBr(s)⇌Ag+(aq)+Br−(aq),a solubility equilibrium

Could someone explain why the anode of this cell is AgBr->Ag(s)+Br- even though Ag is being reduced?

reva_bajjuri

does it matter what order the species are listed in on either side of || (salt bridge) symbol?

reva_bajjuri

also, this is 6k.3, not 6k.5

reva_bajjuri

(d) Reaction of chlorine in water:

Cl2(g)→HClO(aq)+Cl2(g)

for this problem, you're supposed to balance the equations using the skeletal reaction above. Could someone please share their work for this problem. I don't understand how Cl2 can be on both sides of the reaction.

reva_bajjuri

i think that the compounds dissolve in water and those substances are spectator ions that don't change oxidation state during the reaction

reva_bajjuri

do you have a specific problem that you're talking about? because for the problems I've been seeing, the cathode substance was in the numerator for calculating Q

reva_bajjuri

the electrochemical series organizes different substances based on the strengths of their oxidizing abilities. The higher a substance is on the table, the better it is at oxidizing other substances. If one substance is higher than another on the list, then it can oxidize the substance.

reva_bajjuri

could you post a picture of your specific question? I think sapling gives people slightly different questions

reva_bajjuri

for acidic environments, you can add H+ and for basic, you can add OH-. in both cases, you can add H2O. I think this is always something you can do, it's just a matter of doing it strategically so you end up with a balanced equation

reva_bajjuri

for this one, first use the activities to find q. the Ecell standard value for the hydrogen galvanic cell is 0 by definition, so you can use these two pieces of information and plug it into the Nernst equation

reva_bajjuri

A galvanic (voltaic) cell consists of an electrode composed of chromium in a 1.0 M chromium(III) ion solution and another electrode composed of gold in a 1.0 M gold(III) ion solution, connected by a salt bridge. Calculate the standard potential for this cell at 25 °C. Refer to the list of standard r...

reva_bajjuri

in part c it says that constant temperature and pressure are maintained

reva_bajjuri

Consider the following reaction at 298 K. 2H2(g)+O2(g)⟶2H2O(g)Δh=−483.6 kJ Calculate the following quantities. Refer to the standard entropy values as needed. could someone please explain why you cannot use S=qrev/T to find the entropy change for the system, but you can for the surroundings. In the ...

reva_bajjuri

4.17 A technician carries out the reaction 2SO2(g)+O2(g)→2SO3(g)at 25°C and 1.00 atm in a cylinder fitted with a piston and maintained at constant pressure. Initially, 0.030 mol SO2 and 0.030 mol O2 are present in the cylinder. The technician then adds a catalyst to initiate the reaction. (a) Calcul...

reva_bajjuri

i also don't understand how the answer has the temperature of the system going up. since the reaction of the system is exothermic, shouldn't the temperature of the system go down and the temperature of the surroundings go up?

reva_bajjuri

4.15 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 25 °C, what is the final te...

reva_bajjuri

could someone explain how you can tell if positional or thermal entropy contribute more to the entropy change of a system or surroundings?

reva_bajjuri

are there any sapling problems from the most recent sapling assignment that are going to be on the midterm?

reva_bajjuri

Hi! I remember Dr. Lavelle stating that some of these are more reliable than the others, and I was wondering which ones are more accurate and why. Thank you! I think the bond enthalpies method is the least stable because the bond enthalpy values for a lot of different bonds is from the averages of ...

reva_bajjuri

I think that when you have endothermic phase changes (solid to liquid to gas), the imf between molecules become weaker and they are able to occupy more microstates, increasing entropy. when you have exothermic ones, molecules are generally brought closer together into more stable positions with less...

reva_bajjuri

For part a, it's important to note that G is negative for spontaneous reactions. Therefore, a positive enthalpy value works opposite of a negative G (which is what is needed for the dissolving to be favored). For part b, the entropy change is likely to be positive because the substance is going from...

reva_bajjuri

hey!! i think the major points of the second law are that entropy is a measurement of the "disorder" of a substance and that the universe is a closed system containing the system and surroundings. Therefore, many reactions cause an increase in the entropy of the universe. The only object/s...

reva_bajjuri

for this problem, because the change in internal energy is equal to 0, you can deduce that q of the system is equal to 0. (in these kinds of expansions, volume is constant, so work is also equal to 0). Because q of the system is equal to 0, q of the surroundings is also equal to 0. Because S=q(surr)...

reva_bajjuri

i think Cv's units are joules/kelvin, not joules/mol-Kelvin, so there's no need to multiply by the number of moles.

reva_bajjuri

i'm kind of confused on what the question is asking, but i think you have to first calculate q because the phase change does not occur until it reaches that temperature. since enthalpy is a state function, you will get the correct value after calculating q in each step because enthalpy doesn't depen...

reva_bajjuri

i would recommend going through the textbook sections corresponding to the lectures and taking notes. i feel like it goes a lot more in depth and breaks the concepts down

reva_bajjuri

i think they talk about this relationship in section 4c.2 of the textbook

reva_bajjuri

for a reversible expansion, is entropy done on the surroundings? also, is there any relationship between the work done on the system and the entropy released by the system during a reversible expansion?

reva_bajjuri

if you are going from a solid to liquid, liquid to gas, or solid to gas, the phase change is endothermic and you would add the enthalpy of the phase change. if you are going from a gas to liquid, liquid to solid, or gas to solid, the phase change is exothermic so you would subtract the enthalpy of t...

reva_bajjuri

Do standard enthalpies ever change, or are they always the same for a specific molecule no matter the reaction? standard enthalpies are the same for substances regardless of the reaction they may be a part of! the whole idea is to standardize these values so they are known in the equations of unkno...

reva_bajjuri

wait to bomb calorimeters not exchange heat/energy with the surroundings?

reva_bajjuri

I think you would convert your grams to moles of nitrogen gas, use pv=nrT to solve for volume, then plug it into the equation w=pv. someone correct me if I'm wrong though because I'm not 100% sure. I am assuming this is an irreversible expansion

reva_bajjuri

so just to be clear, a "stoichiometric amount of bromine" means the exact amount of bromine necessary for the reaction to proceed (no excess?)

reva_bajjuri

could you explain how you convert the mass units to Kilojoules in the first step?

reva_bajjuri

does increasing the temperature always favor the production of the products/increase the k value?

reva_bajjuri

6. H₂ + Br₂ → 2HBr If 120mL of H₂ gas at STP combines with a stoichiometric amount of bromine and the resulting hydrogen bromide dissolves to form 150mL of an aqueous solution, what is the molar concentration of the resulting hydrobromic acid? hi!! this is a question from Justin's week 1 workshop. c...

reva_bajjuri

Screen Shot 2021-01-18 at 11.50.02 PM.png Screen Shot 2021-01-18 at 11.51.59 PM.png could someone please explain why in the very last step of this sample problem in the book, the vaporization enthalpy of br2 is added instead of subtracted (i thought it should be subtracted since its in the reactant...

reva_bajjuri

could someone explain how its possible to change the volume and hold constant pressure or change the pressure and hold constant volume? i thought those two things were inversely related and that one couldn't change without the other

reva_bajjuri

okay someone correct me if i am wrong, but i think monoatomic substances only have translational ke, linear molecules have translational and linear rotational energy, and nonlinear molecules have translational and nonlinear rotational also i have a follow up question. in this case does the term line...

reva_bajjuri

could someone explain the difference between the heat capacity at constant volume vs constant pressure? i am just confused because i thought volume would be constant if pressure was and vice versa according to the ideal gas equation.

reva_bajjuri

when you are calculating the molar internal energy for a molecule, do you only account for rotational energy if it is diatomic or polyatomic? for example if you had to find the internal molar energy of argon, would you only use the equation for translational energy or does it also have rotational en...

reva_bajjuri

hi! the difference between strong acids and weak acids (and strong bases and weak bases) is that the first dissociates completely in solution to form Hydronium(or hydroxide ions) and the second only dissociates partially. The conjugate bases of strong acids are very weak bases with almost no affect ...

reva_bajjuri

for this problem, you're first going to want to set up your ice table. since you are given the equilibrium concentration for oxygen, you'll find that this is equivalent to your x value. you then will plug in this x value to find the equilibrium concentration for so3 and so2. finally, you will have t...

reva_bajjuri

in the example he talked about, it was an acid which produced a hydronium concentration much lower than 10^-7. if you just took the -log of this number, it would give you a number much greater than the neutral solution you started with. this doesn't make sense because adding an acid to a neutral sol...

reva_bajjuri

okay i see now thank you!!!

reva_bajjuri

[*][img]

F9F1911A-057A-4F7A-9C79-C238146ECAB4_1_105_c.jpeg

[/img]

could someone tell me what i did wrong for this problem? i solved for k with the given equilibrium concentrations but i keep getting an x value greater than the initial concentrations

reva_bajjuri

At a certain temperature, the given reaction has an equilibrium constant of kp=337 . PCl3(g)+Cl2(g)↽−−⇀PCl5(g) PCl5 is placed in a sealed container at an initial pressure of 0.0330 bar . What is the total pressure at equilibrium? could someone explain how to start this question? im confused since th...

reva_bajjuri

could you maybe share your work for this problem? When i was doing this one i kept getting the wrong answer because i subtracted x instead of 2x, so that might be the problem. It's probably a small error if you got the other concentration to be correct

reva_bajjuri

If the concentration or partial pressure of one reactant changes, does that affect any other reactants in the reaction (or if one of these changes for one product, are the other products affected?)

reva_bajjuri

Yes Q is the ratio of [P]/[R] when the reaction is not at equilibrium and K is that ratio when the reaction is at equilibrium. They are calculated the same way with the same formula. Side note reminder, when Q<K reaction will proceed to the right (products) and when Q>K reaction will proceed toward...

reva_bajjuri

if you have a problem in which you are given k and all the initial concentrations of reactants and products and you are asked to find the equilibrium composition (where k is significantly smaller than the initial concentration of the reactant(s)), can you disregard x in your equation?

reva_bajjuri

^^To build off of the above post, the fact that reactions shift in a certain direction to minimize changes is the reason that K does not change when variables such as pressure or concentration are adjusted (only temperature).

reva_bajjuri

so would double bonds count towards the oxidation number too?

reva_bajjuri

if an electron is said to be at the "first excited energy level" is that n=1 or n=2

reva_bajjuri

i know that s orbitals dont have angular nodes but do they have radial ones?

/

reva_bajjuri

^^that is correct. you usually would expand the octet if there is a higher charge on an atom/an unlikely charge. for example, fluorine having a +1 charge would be an example of an unlikely charge on an atom.

reva_bajjuri

does anyone know which atoms on guanine the chlorine atoms in cisplatin bind to? also, do there need to be adjacent guanine base pairs for cisplatin to work

reva_bajjuri

: Screen Shot 2020-12-12 at 9.02.13 PM.png (39.06 KiB) Viewed 318 times

could someone explain how you find the oxidation state of iron given this structure? the answer is +2

reva_bajjuri

: Screen Shot 2020-12-12 at 8.57.27 PM.png (32.04 KiB) Viewed 284 times

for this structure, would <120degrees be a possible bond angle because of the vsepr structure of the oxygen double bonded to the carbon? because this was on the marshmallow review and the answer key said it was not an option

reva_bajjuri

can someone explain why the molecular shape of the heme complex is square planar and not tetrahedral

reva_bajjuri

can someone explain why sulfur acts as a lewis acid and not a lewis base since there is a lone pair on the lewis structure. i know that nonmetal oxides are lewis acids but I'm still confused

reva_bajjuri

could someone explain why cyanide cannot form two coordinate covalent bonds? prof. lavelle said that in the lecture from last week

reva_bajjuri

this is kind of a random question, but why is the name for a central atom connected to 6 atoms "octahedral" instead of "hexagonal'?

reva_bajjuri

how do you know which compounds are named with latin nomenclature and which ones are not.

reva_bajjuri

If there are no neutral compounds in the coordination compound, then will the oxidation number and coordination number always be the same?

reva_bajjuri

When group 13 halides are part of the coordination compounds, how do you know how to change the suffix (ex. how do you know if chloride becomes chloro vs chlorido)

reva_bajjuri

could someone explain why the coordination number for [Cd(en)Br2] is 4 and not 3.

reva_bajjuri

does anyone know why exactly the ring structure is stable/what the benefit of forming a ring is?

reva_bajjuri

are all of the hydrogens perpendicular to the plane the carbon sigma bonds are in?

reva_bajjuri

okay, that makes sense. could someone give me an example of when sp3d hybridization would take place.

reva_bajjuri

so for the above ethylene structure are all of the hydrogens in the same plane?

reva_bajjuri

An organic compound that is distilled from wood has a molar mass of 32.04 g/mol. Its composition by mass is 37.5% carbon, 12.6% hydrogen, and 49.9% oxygen. For this problem, I got the molecular formula ch4o which i believe is correct. I was just confused on how you are supposed to know the structure...

reva_bajjuri

this is mostly in reference to number 17 on sapling, but could someone explain the relationship between the number of carbon atoms in the central carbon chain of an organic structure and whether or not the hydrogen atoms (or whatever other atom might be attached) are in the same plane? i don't reall...

reva_bajjuri

Select the choice that contains all carbon atom hybridizations that are represented in the structures of C3H4 . sp and sp2 sp, sp2, sp3, and sp3d2 sp, sp2, and sp3 sp, sp2, sp3, and sp3d The answer to this question is sp, sp2, and sp3. could someone explain why the carbon hybridizations dont have d ...

reva_bajjuri

The question is asking for the three lewis structures for c3h4. I did one with a triple bond between the central carbon atom and another carbon atom and I did a structure with the central carbon double bonded to two other carbon atoms. I cannot figure out what the third one could be so if anyone has...

reva_bajjuri

what is the difference between electron structure and molecular structure?

reva_bajjuri

when a structure had both lone pairs and bonds, how do you know which angles are bigger and which are smaller (the angles between lone pairs, between lone pairs and bonds, or between bonds)

reva_bajjuri

two lone pairs would not make it linear. for this problem, think of the molecular structure to be ax4 (tetrahedral). however, the lone pairs take the place of two atoms in this structure, making it bent as well.

reva_bajjuri

i'm pretty sure the lone pair on the Nitrogen would have no effect on the molecular structure because it is not a central atom.

reva_bajjuri

could someone explain why structures with double bonds are bent instead of linear?

reva_bajjuri

okay i was just confused because on sapling it said the most likely resonance structure was one with more nonzero formal charges. the only difference was that it lacked a lone pair

reva_bajjuri

for the carbamate ion(and all other ions w resonance structures) are structures with no lone pairs favored over those with lone pairs? even if the one with lone pairs has lower formal charges?

reva_bajjuri

okay makes sense! is there anywhere i can find all of the exceptions we should be aware of for this class?

reva_bajjuri

could someone explain why for the configuration of certain d block metals (ex. copper) why an electron is donated from the s orbital to the unpaired d one.

reva_bajjuri

[Rn]7s26d2
for part d, the answer for the ground state electron is thorium, but the last two electrons are in the d subshell. could anyone explain why this is the electron configuration for thorium.

reva_bajjuri

the answer key says that the configuration for part b is excited but i cannot understand why. since all of the electrons in the 2p subshell are in their own orbitals, doesn't that make them ground state

reva_bajjuri

because delocalized electrons are not really associated with one atom, does that mean they have more energy than localized electrons?

reva_bajjuri

does an atom need to be bonded for it to have a formal charge?

reva_bajjuri

could someone explain the difference between the formal charge of an atom and the oxidation number of an atom?

reva_bajjuri

are hydrogen, helium, lithium, or beryllium capable of donating the electron pair for coordinate covalent bonds or are they more likely to receive the electron pair? also generally speaking, which atoms are most likely to donate electrons for coordinate covalent bonds?

reva_bajjuri

Is selenium also an exception to the octet rule? I remember learning this in high school chemistry but didnt see it mentioned anywhere in the lectures or textbook.

reva_bajjuri

i think the answer is 10 orbitals. if you look at the periodic table, you should be able to find the answer by counting all the blocks in the first two energy levels. these are all orbitals that could be occupied by an atom with its n=2 shell completely filled.

reva_bajjuri

boron only has 3 valence electrons and therefore it is most energetically favorable to only form 3 covalent bonds. however in some other instances (such as the formation of amines), another atom can donate electrons to boron, allowing it to form a full octet

reva_bajjuri

do expanded octets usually correspond with resonance lewis structures or are those two things unrelated?

reva_bajjuri

for this problem, would you use the 4 sig figs in the conversion from joules to electo volts or are those not significant figures?

reva_bajjuri

A blue line is observed at 486.1 nm in the spectrum of atomic hydrogen. Determine the values of n for the beginning and ending energy levels of the electron during the emission of energy that leads to this spectral line. i am totally lost w this question. could someone explain what other info i need...

reva_bajjuri

thank you!!! also hey roomie

reva_bajjuri

could someone explain the difference/relationship between these three concepts?

Search found 117 matches