CHEMISTRY COMMUNITY

Gabi_Maldonado_1B

Does a reaction always have to be either controlled by thermodynamics OR kinetics?

Gabi_Maldonado_1B

Does a reaction always have to be either controlled by thermodynamics OR kinetics?

Gabi_Maldonado_1B

In short: kinetics is related to the speed or rate of reactions and does not deal with the favorability of reactions. Thermodynamics, however, considers the energetic favorability of a reaction.

Gabi_Maldonado_1B

Just clarifying: Is molecularity just dependent on the number of reactants regardless of whether or not they are the same type of reactant (ex: 2A and A+B are both bimolecular)?

Gabi_Maldonado_1B

A pseudo rate law involves limiting the amount of one reactant in order to observe its affect on the overall reaction/the reaction's dependence on it. The other reactants in the reaction will be in excess in order to focus more highly on the reactant with the smallest amount.

Gabi_Maldonado_1B

In order to find the integrated rate law, we must integrate the differential rate law I believe so there is a way to derive each from the other.

Gabi_Maldonado_1B

I believe it is because the slowest step has the greatest impact on the rate of reaction and therefore will influence the overall rate law the most.

Gabi_Maldonado_1B

Hi! I'm trying to decide whether I should switch to in person lectures for this class. Does anybody have any particular preference or thoughts on whether one environment is more conducive to learning? I know the in person discussion section has really helped me but I'm not sure whether in person lec...

Gabi_Maldonado_1B

Can someone clarify what a glass electrode is? I've seen it in our notes(lecture 2/18) and I have forgotten its meaning since lecture.

Gabi_Maldonado_1B

I remember discussing electroplating in high school but I forgot how it works in its connection to electrochemistry. Can someone explain how it's done and the reaction process?

Gabi_Maldonado_1B

Hi, should we just know those two bullets on electrolysis that he mentioned in lecture 2/18? I remember going into greater detail in high school chemistry so I just want to make sure we don't have to go beyond knowing the definition.

Gabi_Maldonado_1B

I'm thinking of making flashcards, but other than that, how are you studying or remembering the spontaneity rules for when (ΔH and ΔS are positive/negative)? Anybody have any tricks or mnemonics?

Gabi_Maldonado_1B

Will we have to work with integrals and derivatives on the second midterm? I have yet to see them on anything other than the derivations we did in class (but I still have some textbook problems to finish).

Gabi_Maldonado_1B

I didn't really know what to call this so excuse the vague "form" word I chose, but I was wondering whether the degree symbol (° - indicating that the substance is in its standard state and the reaction is taking place at 298K, 1atm,etc.) appearing on one part of the equation for example d...

Gabi_Maldonado_1B

Hi just clarifying where the Midterm 2 content starts. Should I be studying the first law of thermodynamics or does it start before/after that?

Gabi_Maldonado_1B

Hi, I was just looking at the SI units listed for this unit including Ampere (a unit for electric current), Coulomb ( unit for electric charge) and Volt (unit of potential). I was just hoping for some context to help me differentiate electric current from electric charge and further solidify my unde...

Gabi_Maldonado_1B

Can galvanic and voltaic cell be used interchangeably? If not what is the difference between the terms?

Gabi_Maldonado_1B

As I was posting that question I think I might have figured out the answer to my own question. Is it related to the fact that E° is an intensive property?

Gabi_Maldonado_1B

For an example that we did in class on 2/16 I noticed that we multiplied everything in the Fe 3+ half reaction by 2 but it did not affect the E value. Can someone explain why we don't need to alter the E value when we multiply the entire reaction by 2?

Gabi_Maldonado_1B

Is another word for battery a galvanic cell? Can they be used interchangeably? Or, is a battery an example of a galvanic cell (or vise versa)?

Gabi_Maldonado_1B

Thanks! I accidentally confused equations from this unit and last unit.

Gabi_Maldonado_1B

Hi I think I have the right methodology to solve number 5 but I keep getting an incorrect answer. I started by using PV=nRT to find the number of moles (converting celcius to K and kPa to atm and then using the R value .08206). Then I multiplied the number of moles by the molar heat capacity and del...

Gabi_Maldonado_1B

After finding the number of moles u find the heat capacity(C) by multiplying the molar heat capacity (Cm) by the number of moles found.

Gabi_Maldonado_1B

I made that same mistake! Thanks a bunch.

Gabi_Maldonado_1B

Hi, the following question is a question from my friend studying chemistry at a different college, I wasn't completely sure about my answer, so I thought I'd ask here. Can someone offer an answer and explanation for this question? An oxalate ion functions as a bidentate ligand. How does a very highl...

Gabi_Maldonado_1B

Can someone talk me through how to solve 19 on the Achieve HW? A constant‑volume calorimeter was calibrated by carrying out a reaction known to release 0.959 kJ of heat in 0.700 L of solution in the calorimeter (q=−0.959 kJ) , resulting in a temperature rise of 3.24 ∘C . In a subsequent experiment, ...

Gabi_Maldonado_1B

When do I use the -PΔV equation versus the -nRT ln (V1/V2)?

Gabi_Maldonado_1B

I'm writing down important concepts and types of calculations as a part of my studying and I was wondering why we set the q of one substance equal to the negative q of the second in certain types of problems.

Gabi_Maldonado_1B

Why are we supposed to calculate the q(ice) and add it to the heat of fusion for this reaction. I remember in the textbook I had added the q(water) to the heat of fusion because the ice melted and the heat of water was then used because it had reached its liquid state. Does this change based on the ...

Gabi_Maldonado_1B

I keep on getting the incorrect answers for question 10, but I'm following the correct procedure that they give in the feedback of adding the q(ice)+H fus=-q(water). I was hoping someone could show the preliminary values they got for this equation (including the "Tfinal" as a variable not ...

Gabi_Maldonado_1B

Can someone remind me when we should be using the unit joules and when we need to use kJ?

Gabi_Maldonado_1B

What problems on the homework cover material that will be on the midterm?

Gabi_Maldonado_1B

Hi just curious... do we need to be able to complete all of the textbook problems on outline 3 or did we not cover the entirety of the unit yet? I remember him saying something about outline 3 but I'm not completely sure if I have the right information.

Gabi_Maldonado_1B

Are monoprotic acids often used in our calculations to maintain a 1:1 molar ratio between the reactants and products for the ICE box?

Gabi_Maldonado_1B

I agree with the answers posted above. I think that the cold pack will absorb heat from our skin, thus cooling that area of our bodies down and warming up the ice pack. The icepacks don't stay ice cold for an extended period of time because of the heat transfer.

Gabi_Maldonado_1B

I noticed myself getting tripped up over the Ka and Kb values and using the wrong ones on this weeks Achieve HW. Can someone please clarify if you should be using strictly Kb, pOH and [OH-] values in order to compute values for bases and Ka, pH and [H3O+] for acids (excluding the use of pOH to find ...

Gabi_Maldonado_1B

Why are we able to write (GR) for graphite in equations for which Carbon is at its most stable state?

Gabi_Maldonado_1B

On question 5 for this weeks Achieve HW I keep getting incorrect answers. Can someone talk me through how to solve this question? The Kb for an amine is 6.694×10−5. What percentage of the amine is protonated if the pH of a solution of the amine is 9.233 ? Assume that all OH− came from the reaction o...

Gabi_Maldonado_1B

My TA brought up the concept of Law Mass Action but I kind of lost him in his explanation of its connection to Chemical Equilibrium. Can someone break down the concept and its connection to K?

Gabi_Maldonado_1B

Can someone simply explain our use for Le Chatelier's Principle?

Gabi_Maldonado_1B

How do you determine the inital concentration for SO2, given the moles of SO3?

Gabi_Maldonado_1B

Something that I get confused with when setting up the ICE box is the determining what the change in concentration is and whether to write -x, +x,+2x...etc. Specifically for problems such as 9 on week 1 achieve hw, when the reaction is at equilibrium and then there is a change to the concentration, ...

Gabi_Maldonado_1B

Hi I keep getting the wrong answer for 2 and I think its because my ICE box set up is incorrect. Can some one talk me through how they set up the ice box for this question?: At a certain temperature, 0.600 mol SO3 is placed in a 4.00 L container. 2SO3(g)↽−−⇀2SO2(g)+O2(g) At equilibrium, 0.110 mol O2...

Gabi_Maldonado_1B

If I understand you correctly, I don't think that the conjugate seesaw is related to the pOH + pH equation, in that the pH of the conjugate acid or base, when added to the reactant acid or base will equal 14.

Gabi_Maldonado_1B

Amphiprotic refers to its ability to donate and accept protons. (I remember it by thinking amphiPROTic --proton). Amphoteric is defined as a substance with acidic and basic properties. This term is less specific to protons and the molecules behavior in relation to donating and accepting them.

Gabi_Maldonado_1B

There is an inverse relationship between Volume and Pressure. This is evident in the PV=nrT equation and can be tested. As pressure increases, volume will decrease and vise verse.

Gabi_Maldonado_1B

I typically recognize a weak acid when I see a -COOH group, indicating an organic acid. Or, by knowing that the following are strong acids: HCl, HBr, HI, HNO3, HClO3, H2SO4, therefore any acids that do not fall into this group can be considered weak acids.

Gabi_Maldonado_1B

In the equation 2 H20 --> OH- + H3O+, one of the two water molecules functions as an acid while the other functions as a base because one molecule donates a proton while the other accepts it.

Gabi_Maldonado_1B

A salt is an ionic compound (usually made up of a nonmetal and a metal -- so this is something you can look out for in the molecular formulas). There are acidic and basic salts. This can be determined by creating a chemical equation that represents the formulation of the salt. For example, to create...

Gabi_Maldonado_1B

In my understanding, an oxoacid is an acid containing oxygen molecule(s). The greater amount of oxygen molecules, otherwise stated as the greater electronegative atoms in an oxoacid, makes the pKa value smaller and the acid stronger because the electronegativity difference places a greater positive ...

Gabi_Maldonado_1B

Is the coefficient referring to the period in which it is occurring always necessary, or is it just for additional information?

Gabi_Maldonado_1B

Can someone clarify the definition for conjugate acids and bases? Do they have a purpose?

Gabi_Maldonado_1B

In the case that you are just given a formula, create a lewis dot structure for the molecule. From there, determine whether the molecule is proton or electron donor and label it as a Bronsted or Lewis acid or base. Drawing out the dot structure can indicate this by having lone pairs for example.

Gabi_Maldonado_1B

I think it is also helpful to look for lone pair electrons. That would indicate a lewis base because those electrons can be donated.

Gabi_Maldonado_1B

I think it is also helpful to look for lone pair electrons. That would indicate a lewis base because those electrons can be donated.

Gabi_Maldonado_1B

If you're looking for equations that are missing from the formula sheet on the website, formal charge is not there. (FC=V-(L+S/2)

Gabi_Maldonado_1B

A bidentate ligand binds at two sites. Similarly, the prefixes tri-, tetra-, penta-, etc. can be used to describe the number of sites to which a ligand binds. this is significant in determining the coordination number of a central atom.

Gabi_Maldonado_1B

How are you studying for the final? I'd like to incorporate some new techniques into my studying this year.

Gabi_Maldonado_1B

Hi! Finding Oxidation number isn't something I'm very comfortable with. Can someone explain to me how they go about it step by step?

Gabi_Maldonado_1B

To add to the last response, I think that the locations of the atoms, whether they are adjacent or across from each other can have significance as to whether or not the molecule is polar. This wasn't explicitly explained in this example but he also discussed molecules (trans- and cis-dichloro-ethene...

Gabi_Maldonado_1B

Yes! From my understanding, coplanar should mean that the atoms lie in the same plane. Geometries such as trigonal planar, square planar and linear are all examples of these and can help you determine whether a molecule is coplanar.

Gabi_Maldonado_1B

Generally, I'm a little confused with why hybridization occurs, and what purpose it serves.

Gabi_Maldonado_1B

What does a 2 in front of the hybridization mean? (ex: 2sp)

Gabi_Maldonado_1B

Is the shape of I3 - linear because the electron arrangement is tetrahedral? with the lone pair electrons in the trigonal spaces?

Gabi_Maldonado_1B

What are the other possible names for electron arrangements?

Gabi_Maldonado_1B

Can the f- orbital ever be utilized to create an expanded octet? Or is it just the d-orbital?

Gabi_Maldonado_1B

Can the f- orbital ever be utilized to create an expanded octet? Or is it just the d-orbital?

Gabi_Maldonado_1B

The octet rule applies to atoms with electrons in the s- and p- orbitals. Therefore, when there is an expanded octet which functions as an exception to the octet rule there are electrons available in the d- orbital. Since the d-orbital has 10 electrons, it follows that there is availability for 10 m...

Gabi_Maldonado_1B

Yes, the midterm isn't cumulative. Specifically, the lecture from 10/18 started the new material for midterm 2. This started with the topic Electron Configuration of ions.

Gabi_Maldonado_1B

If electronegativity is the tendency to attract electrons and Ionization energy is the energy required to remove them, are Electronegativity and Ionization energy conflicting or opposite characteristics?

Gabi_Maldonado_1B

Is the reason for these elements being the exception to the octet rule because they only have electrons in the s-orbital?

Gabi_Maldonado_1B

Electronegativity is the attraction that an element will have to an electron. This affects the element's tendency to form covalent bonds. Electronegativity increases as you go towards the right in the periods of periodic table and up the groups.

Gabi_Maldonado_1B

I typically look at the periodic table. Specifically the group that the element is in 1,2, and so on, are great indicators of the number of valence electrons. Just be sure to recognize whether the element is in the s,p or d group and take this into account.

Gabi_Maldonado_1B

Adding to the last post, ionic bonds are typically between a metal and a nonmetal, in which one atom donates electrons to the other. My understanding is that covalent bonds typically occur between nonmetals and therefore it is not possible for an ionic bond to become a covalent bond.

Gabi_Maldonado_1B

In order to determine the number of spectral lines possible we subtract the lowest possible energy level from the energy level that is given in the question. But, can someone explain how and why this reflects the number of spectral lines produced?

Gabi_Maldonado_1B

Hi! Personally, I like to cater towards studying through the learning strategy that I most benefit from. For example, I learn and retain concepts best when I write or rewrite them. Other people I know are visual or audio focused learners so if this is you maybe try watching or listening to the lectu...

Gabi_Maldonado_1B

To clarify: The 3d level will have less energy than the 4s energy level until electrons are filled in this level. So, there shouldn't be a situation in which we are writing an electron configuration of an atom where 4s is written before 3d, because once there are electrons in these levels 3d becomes...

Gabi_Maldonado_1B

When filling the p,d, and f orbitals with electrons, is it correct to put electrons in each orbital with parallel spins, before pairing the electrons in orbitals and reversing the spin of the second one?

Gabi_Maldonado_1B

Can someone explain the difference between constructive and destructive interference to me? What exactly is being represented in the graphs of waves overlayed on the slides from Lavelle's lecture?

Gabi_Maldonado_1B

If a an e- changes energy level to n=1 to emit light in the ultraviolet region, n=2 to emit light in the visible region and n=3 to emit light in the infrared region, what other changes in energy level emit light in the remaining regions? (ex: what does a change to the n=4 level result in? what chang...

Gabi_Maldonado_1B

In order to derive DeBroglie's equation, my TA set these two equations equal to each other. Why are we able to do this and are there other contexts in this unit where we should be using E=mc^2?

Gabi_Maldonado_1B

In the different orbitals, the electrons cannot all be spinning in the same direction, therefore for each suborbital, one will be spinning upwards (+1/2) and the other will spin down (-1/2). I don't think it matters whether the first electron in the orbital you name is spinning up or down, as long a...

Gabi_Maldonado_1B

What's the definition of a nodal plane? I don't remember hearing the term in high school chemistry.

Gabi_Maldonado_1B

In my discussion today my TA discussed the DeBroglie equation but stated that it shouldn't be an equation that we are frequently solving light problems with. Why is this? Why can't the DeBroglie equation be as widely used as the other equations we were given in class?

Gabi_Maldonado_1B

In the equation for the Kinetic energy of an electron, what units should mass be in? kg? Can we take the value from the mass of the electron right of the constant and equations sheet?

Gabi_Maldonado_1B

In the equation for the Kinetic energy of an electron, what units should mass be in? kg? Can we take the value from the mass of the electron right of the constant and equations sheet?

Gabi_Maldonado_1B

In the Photoelectric effect experiment, it was said that the intensity of light was increased with the hope of successfully emitting electrons. Does the intensity refer to the number of photons released?

Gabi_Maldonado_1B

Is the reason that the energy level values are quantized because fractions of an energy level can't exist?

Gabi_Maldonado_1B

I just wanted to clarify: Increasing the intensity of the light or energy, failed to emit electrons but, when frequency was increased, this caused for electron emission. And, because frequency and wavelength have an inverse relationship, this means that lower wavelength lights can increase the amoun...

Gabi_Maldonado_1B

Hi! Everyone explained what quantized means very well so I won't repeat that. But, I thought another helpful example that he gave in class was the comparison to the continuous equation of f=ma. In this equation there are no limits on what the values of the mass or acceleration can be (it isn't limit...

Gabi_Maldonado_1B

Me too! I haven't take chemistry in about 3 years. I'm finding that in reviewing Professor Lavelle's Audiovisual focus topics (which he assigns anyway) have been super helpful before heading to class. That way, I have more than one opportunity to digest the information (in lectures and in his videos).

Gabi_Maldonado_1B

Hi! How can Professor Lavelle see that we are completing our 5 posts per week? Do I need to change my profile from my UID to my name or am I set?

Gabi_Maldonado_1B

Should I be constantly be rounding my answers in different steps of solving for my final answer, or should I just keep a high number of sig figs in my answers until I reach the final step and round to the given number of sig figs?

Gabi_Maldonado_1B

When the molar mass given has a period of uncertainty such as the one in question 9 (molar mass of 110±10 g/mol), what value should I use in my calculations? Will I be able to get the correct answer using just 110g/mol?

Gabi_Maldonado_1B

Hi! A helpful and simple trick I learned in high school was the Atlantic and Pacific trick. If you picture a map of the US and recognize that the Atlantic is on the east or left hand side and the Pacific is on the West or right hand side, you can connect this to what side of the number you should be...

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