CHEMISTRY COMMUNITY

Bronson Mathos 1H

Hello, I was a bit lost doing Sapling Problems 9 and 10 of week 2 and I was wondering if someone could explain what would make the predominant species at a certain pH charged, neutral, or unknown?

Bronson Mathos 1H

Hello, during week 2, the ionization constant of water(1.0x10^-14) was given to us, and I was wondering what the significance of this constant is and if we need to have this memorized for future exams?

Bronson Mathos 1H

Hello, I am struggling with differentiating the processes for solving equilibria problems of weak and strong acids and bases problems and I was wondering if someone could explain the key differences in solving for weak or strong acid and bases problems?

Bronson Mathos 1H

Hello, I am a bit lost on determining the pH of acids and bases and was wondering when one knows that taking the -log will wield the pH or the pOH?

Bronson Mathos 1H

Hello, in Friday's lecture, professor said that the second method (using bond enthalpies to calculate enthalpy change) was the least favorable method of the three to find enthalpy change, and I was wondering if one of the other two methods was considered the best?

Bronson Mathos 1H

Hello, I am a bit lost on the applications of the quadratic equation in chemical equilibrium and I was wondering if this equation can be applied to other scenarios besides finding molar concentration?

Bronson Mathos 1H

In the first lecture of week 2, Professor Lavelle mentions the autoprotolysis constant of water being 1.0x10^-14, and I was wondering if this is an important constant we need to remember, or is it a constant that we only need for certain problems and will likely be given to us?

Bronson Mathos 1H

Hello, I saw on one of the Sapling feedbacks from week 1 that a chemical equilibrium problem required the use of Hess's Law. I may have missed this at some point and was wondering if someone could explain to me in basic terms what this law does.

Bronson Mathos 1H

Hello, I believe I may be getting my variables mixed up, but I was wondering if the equilibrium constant Kc and the reaction quotient referred to the same value?

Bronson Mathos 1H

Hello, I am having a bit of difficulty understanding how to use the ice box and was wondering if someone could explain how I would use it in these chemical equilibrium problems?

Bronson Mathos 1H

Hello, I am just a bit confused on the functionality of the Ideal Gas Law and was wondering if when using the law in a calculation, it would be safe to assume that P/R is directly proportional to K?

Bronson Mathos 1H

Hello, I just had a question regarding chemical equilibrium and was wondering if it is correct to assume that although the concentrations of reactant and product are not changing at equilibrium, reactants and products are still forming at the molecular level?

Bronson Mathos 1H

Hello, I was reviewing the response of equilibria to change and was wondering if the only change that causes K to change is a change in temperature?

Bronson Mathos 1H

Hello, I am just a bit confused and was wondering, in the equation for the ideal gas law PV=nRT, why is the temperature T regarded as a constant?

Bronson Mathos 1H

Hello, I just need some confirmation on today's lecture and I was wondering that since pure substances are not included in K expression, and since gases have a partial pressure constant Kp, do liquids simply not have any form of equilibrium constant?

Bronson Mathos 1H

Hello, I was just wondering if electron configurations of ions are done by simply doing the same electron configuration except adding or removing an electron from the last orbital?

Bronson Mathos 1H

Hello, I'm a bit lost on the exceptions to the octet rule, and I was wondering if someone could just give me a general rule to know when an atom is exempt from the rule?

Bronson Mathos 1H

Hello, I was just wondering if there is anything we need to know about the Stern and Gerlach Experiment beyond the fact that it was used to discover the electron spin( the 4th quantum number) of an electron in an orbital?

Bronson Mathos 1H

Hello, I was just wondering if we are asked to balance a chemical reaction and the product is given in the form of a name such as iron(III) oxide, are we still going to be provided with the chemical formula as well , or do we have to know what the chemical formula is? And if not, how would I go abou...

Bronson Mathos 1H

Hello, I'm just a tad lost on what makes a molecule more or less acidic, is it the gain or loss of protons or is it solely based on the pH of the molecule?

Bronson Mathos 1H

Hello, when the notes state that a Bronsted acid is a proton donor, does that equate to the same idea as a Lewis acid being called an electron recipient? Or are the two different?

Bronson Mathos 1H

Hello, I would just like some clarification on how the strength of acids are determined and I was wondering in particular are weaker acids more likely to lose their H+ or are strong acids more likely to do so?

Bronson Mathos 1H

Hello, I was wondering if anyone could give me any tips on determining the coordination number of atoms, or just clarify if the only thing we need to determine a coordination number is to know the number of bonds to the atom?

Bronson Mathos 1H

Hello, I would just like to clear something up from my notes and was wondering that since sigma bonds allow for the bound atom to rotate and pi bonds do not allow their bound atom to rotate, does that mean when both bonds are together, say in a double or triple bond, does that mean the bound atom do...

Bronson Mathos 1H

Hello, I've been reviewing for finals and found I understood very little on hybridization and I was just wondering if someone could briefly explain how I should approach problems that ask how to determine the hybridization of an atom?

Bronson Mathos 1H

Hello, I was wondering if I could get some help with determining molecular shape, more specifically the bent shape, and I was wondering if someone could explain what makes a molecule form the bent shape?

Bronson Mathos 1H

Ligands are considered any electron rich species, so my question is when do we consider a species to be electron rich so that it can also be considered a ligand?

Bronson Mathos 1H

Hello, I was looking over past notes and saw that we are expected to know when bond angles are greater or less than a certain common bond angle and I was hoping someone could explain how we would go about doing this?

Bronson Mathos 1H

Hello, after seeing my midterm score I believe I may not be very keen on drawing Lewis structures and I was wondering if anyone could give me some tips or a basic outline that will help me draw Lewis structures in the future. Thanks in advance!

Bronson Mathos 1H

Hello, I am just a bit lost on non-polar molecules and was wondering if someone could explain what makes these molecules non-polar, thanks!

Bronson Mathos 1H

Hello, I would just like some clarification on when we draw molecular shape, and I was wondering if for the three dimensional depictions do dashed lines indicate a bond with an atom facing behind the rest of the molecule and then do bold bonds indicate a bond with an atom closest to your view?

Bronson Mathos 1H

Hello, I am a little lost on making Lewis structures and was wondering if it is possible to have an unpaired electron in a Lewis structure?

Bronson Mathos 1H

Is there a difference between Lewis acids and bases and cations and anions? Because I have noticed they seem to have the same properties of either donating or accepting electrons and I would just like some clarification on the difference between the two. Thanks!

Bronson Mathos 1H

Will we ever need to make calculations using the Schrodinger's wave function equation? Or will we only need it to describe atomic orbitals?

Bronson Mathos 1H

Hello, I had a question regarding dipole-dipole and dipole-induced dipole interactions, which is in regards to their value of -2kJ per mol. So my question is that is the value of dipole-dipole interactions and dipole-induced interactions exactly the same? Or is the dipole-induced dipole slightly les...

Bronson Mathos 1H

Concerning quantum numbers, will we ever be asked to determine the spin of the fourth quantum number ms? Or will we only be asked if a certain ms is possible in a set of all four quantum numbers?

Bronson Mathos 1H

I solved this using the N, O, and F rule of hydrogen bonding by locating and counting all the possible points on the structure where a hydrogen bond could occur and that total should give you your answer as the question implies that the water molecules would bond to urea using hydrogen bonds.

Bronson Mathos 1H

In determining hydrogen bonds, in addition to bonding with N, O, and F, is a hydrogen atom bonding with another hydrogen atom considered a hydrogen bond?

Bronson Mathos 1H

Hello, I just need some clarification on octet exceptions and was wondering if there are any exceptions to the octet rule we need to know besides the first three elements of the periodic table?

Bronson Mathos 1H

If we are ever asked about dipole moments on the midterm or final, is coulombs or debye a preferred unit or is using either acceptable?

Bronson Mathos 1H

Hello, I am just a bit lost on understanding the various elements grouped by last occupied shells, and I was wondering if anyone could explain in simple terms how to navigate/find the various s, p, and d blocks, and maybe provide an easy method to grasp the trends in the periodic table? Thanks!

Bronson Mathos 1H

I just need some clarification on the amount of energy of an electron depending on its location on the orbitals of an atom. So my question is: Is the energy of an electron highest when it is in the orbital closest to the nucleus, or when it is the farthest orbital away from the nucleus as a valence ...

Bronson Mathos 1H

During Friday's lecture, professor in an example called some elements forming ionic bonds a salt, and elements forming covalent bonds a molecule. Is it safe to say any elements forming ionic bonds are salts and any elements forming covalent bonds are called molecules?

Bronson Mathos 1H

Personally, I find myself being mostly distracted by my phone while at home and being at home can lower your sense of urgency to do your work. I would recommend removing your phone from your workspace, and if that's not possible then try to set screen time limits on the apps that distract you. I'd a...

Bronson Mathos 1H

Yes, I believe all elements in group 13 do not have to form an octet when forming bonds as they are exempt from the octet rule.

Bronson Mathos 1H

Hi, would someone mind elaborating/explaining what nodal planes are and their involvement in quantum numbers?

Bronson Mathos 1H

I believe this topic is related to the diffraction patterns of light in the experiment covered in the wave properties of electrons module, as the interaction of waves after they passed through the two slits of the barrier can produce constructive or destructive results depending on how the waves of ...

Bronson Mathos 1H

I believe you generally should make it positive because the negative symbol simply indicates that the energy of light is being emitted and the electron is slowly returning to ground state, and not an actual negative quantity.

Bronson Mathos 1H

There will be 12 questions on the midterm, but Professor wrote it as 11+1 in his email, so one may be extra credit or a free question but I am not sure.

Bronson Mathos 1H

For this problem, since the question says the kinetic energy is zero, we can reason that the energy of a photon hitting the metal surface is equal to the threshold energy. And with this idea, you simply use the given energy 3.607x10^-19J and the equation E=hc/wavelength and solve for wavelength. I h...

Bronson Mathos 1H

Hi, I was just looking for a brief explanation/clarification on core electrons as mentioned in today's lecture about writing electron structures. When you use a core electron in writing a configuration, do you have to use the element that is at the end of the previous row? Or can you use any previou...

Bronson Mathos 1H

For this question, you first need to determine the total energy per photon of the lamp using the equation E=hv(E=hc/lambda). Using this equation you should get: E=(6.626x10^-34J*s)(2.998x10^8m/s)/(420x10^-9m)=4.7x10^-19J*photon^-1. Using the given information that the lamp is rated at 32W(J*s^-1) we...

Bronson Mathos 1H

In order to solve this problem, I started off by using the equation M initial x V initial=M final x V final, and with this equation you plug in all known values to find that M final is unknown, meaning you must solve for it and you should get 0.05 moles per liter. From here, you use this molarity an...

Bronson Mathos 1H

I believe your only error in this solution is when you solve for the uncertainty in momentum you said it was 8.1746x10^-9, and when I calculated the uncertainty I did exactly the same process as you did and got the uncertainty in momentum to be 8.1746x10^-6. And using this value I solved for the unc...

Bronson Mathos 1H

I am not certain if there is a constant or number to compare to the uncertainty of the kinetic energy, but for this problem I simply looked at the two kinetic energies that we were asked to solve for and I realized that the exponents of the portion in scientific notation were of the opposite sign, w...

Bronson Mathos 1H

This number 3.37x10^-19 J is not a constant you need to memorize, it is the energy emitted by a single excited sodium atom when it generates a photon, which is the solution found in part A of 1.7, and is significant as it is used in this problem to find the amount of energy emitted by 5.00 mg of the...

Bronson Mathos 1H

In this question, you do convert 125km*hr^-1 to m*s^-1: 125km*hr^-1x(1hr/60min)x(1min/60sec)x(1000m/1km)=34.7m*s^-1. And then you simply use this speed in Debroglie's wave equation to find the wavelength :Wavelength=h/p=h/mv. Wavelength= (6.626*10^-34J*S)/((275kg)(34.7m*s^-1))= 6.94*10^-38m.

Bronson Mathos 1H

In part B, you are asked to calculate the amount of energy emitted by 5.00mg of sodium at the given wavelength, and in order to do this, you simply convert the 5.00mg of sodium to moles(you must first convert mg to g) and then to particles and then multiply this result by the energy emitted from a s...

Bronson Mathos 1H

The two words are "wave" and "particle", and photons is not the answer because the question is asking about how the results of the effect were interpreted, and it was interpreted using a detector to detect electrons emitted by the photons striking them, meaning electrons were bei...

Bronson Mathos 1H

In order to solve this problem you basically need to find the energy of the photons and subtract the threshold energy from the energy of the photons in order to find the excess energy, which is the kinetic energy. First you must calculate the frequency of the light, by dividing the speed of light(c)...

Bronson Mathos 1H

Are we required to memorize the wavelengths for each part of the electromagnetic spectrum? Because on the post-assessment module for Atomic Spectra, question 44 asks what region the wavelength of this solution would fall under and I was just wondering if we would have to know which region by heart.

Bronson Mathos 1H

I had trouble with this problem too, the issue here is the given work function of 150.6kJ/mol. This work function is the threshold energy to remove an electron, but I realized that it is given in kilojoules and only applies to a mole of an atom. Therefore, I converted kilojoules to joules (150600J) ...

Bronson Mathos 1H

You do not have to do every single question, you may only do the ones that you think you should do as they are not being collected, but remember that Lavelle does pull some questions from the textbook homework and places them on exams.

Bronson Mathos 1H

The copper metal is not included in the chemical reaction as it is a catalyst, meaning it is used to simply speed up the chemical reaction going on in the equation. But the copper catalyst can be represented on the top of the arrow in between the reactants and the product.

Bronson Mathos 1H

Sapling is correct here because if 291.7 was put into the scientific notation of 2.917x10^-2, the decimal would move to the left instead of the right when you take it out of scientific notation, meaning that if the exponent of the notation was -2, then the number would be 0.02917 and not 291.7. So, ...

Bronson Mathos 1H

In this scenario, yes you can simply count each element as any drawing or depiction of a molecule will be in its molecular formula unless specified otherwise in the question.

Bronson Mathos 1H

On problem G7 of the textbook homework, does this concept simply involve calculating 5.45% of 510g in order to determine the mass of KNO3 in this solution? If so, is there some type of formula I missed because this idea seems too good to be true.

Bronson Mathos 1H

I believe you should generally leave the volume in liters as it makes it easier to solve for molarity which is measured in moles per liter, and to follow SI units as well.

Bronson Mathos 1H

When the professor did his example of the combustion of butane, he showed that butane reacted with O2. If we were every given a problem that told us a compound was burned or combusted is it safe to assume we can always place an O2 molecule on the reactant side of a chemical equations?

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