CHEMISTRY COMMUNITY

Sebastian2I

Also skim the chapters and focus on the example problems provided therein. They give good explanations and if you don't get something look right above them for an explanation.

Sebastian2I

I would recommend looking over the old Sapling problems and making sure that you can still follow their logic. Carefully read the solutions if there is something you don't get, and keep the constants and equations sheet close at hand so that you can note where to look when you encounter similar prob...

Sebastian2I

Always remember that the reducing agent is the reactant that itself gets oxidized and vice versa. So if you're looking for a strong reducing agent, you're looking for something that really wants to be oxidized i.e. has an extremely low reduction potential.

Sebastian2I

Does anyone have any good tips for preventing rice from getting stuck to the bottom of the pot?

Sebastian2I

Remaining on the subject, if anyone is looking to improve their egg-cooking, Tasty made a great video on how to prepare five different kinds of eggs. I've tried a few myself and found these methods quite effective:
https://www.youtube.com/watch?v=X5oD_thIk3c

Sebastian2I

Apparently the legendary French chef Fernand Point made his apprentices fry eggs over a candle to impress upon them the delicacy of the process (Source: Raymond Sokolov's How to Cook). What an interesting thermodynamics question this would make!

Sebastian2I

Appropriate to the subject we're covering rn: I just learned that you season the skin of a turkey with baking soda because it acts as a catalyst which speeds up the Maillard reaction - giving it a nice brown coloring. If anyone has any more info on the Maillard reaction pls share I've heard it refer...

Sebastian2I

I was just reading the textbook's chapter on catalysts and enzymes and happened across a line describing how the enzyme amylase breaks down starches as you chew them into digestible glucose. As a result, chewing starchy foods for extended periods of time will make them taste sweeter. I suppose this ...

Sebastian2I

I was just reading the textbook's chapter on catalysts and found the passage about how some catalysts can be "poisoned" or inactivated - with lead being a potent poison in this sense. Does this have anything to do with lead poisoning in humans? Does the lead deactivate enzymes that we need...

Sebastian2I

almost_ethan wrote:For some reason, I always find myself stress-baking during finals week--just to get my mind off things.

Can definitely relate. These past couple of weeks I've been cooking a lot more because it helps take my mind off of finals and experimenting in the kitchen always yields interesting lessons.

Sebastian2I

Some tips I just picked up for anyone looking to buff their mashed potato game: - Red Bliss Potatoes are the best for rustic smash potatoes by virtue of their thin skin and waxy texture - If you're after creamier mashed potatoes, go for Yukon Gold, which is less waxy than the Red Bliss - The classic...

Sebastian2I

tholz11 wrote:
Mari Williams 1K wrote:Butterfly pea flower tea changes color with pH! People add lemon juice and it makes it look really cool.

I just bought some! Im very excited to use it haha.

So does this mean that I might be able to perform a titration and drink the leftover indicator once I'm finished? :)

Sebastian2I

Its crazy to think that any cooking we do involves chemistry. Like even cutting an avocado in half sets off a chemical reaction that changes the green flesh of the avocado to a brownish color. CRAZY Quick life hack for this. If you ever want to use half of an avocado and save the rest for later, cu...

Sebastian2I

This isn't exactly a joke but I couldn't think of anywhere else to post it. I was just reading Descartes' Third Meditation for my philosophy class and as he mused on why he innately believes that his sensory perceptions resemble the things from which he attributed them in the outside world, he bring...

Sebastian2I

Claudia_Danysh_2B wrote:Hey for anyone interested in this topic, there's an upper division class called "What's Cooking Chemistry in the Kitchen" I think and it mixes cooking with chemistry!!

Thank you for bringing this up. I will definitely be checking that out :)

Sebastian2I

A good strategy for this kind of reaction is to add twice as much hydroxide as you would need to balance the oxygen for the expression, then add just enough water to the opposite side as would be sufficient to balance hydrogens (Done after balancing for the principle species). For example: Br 2 --> ...

Sebastian2I

Word to the wise for anyone handling frozen meat, try not to refreeze the meat once you have defrosted and opened the package. This is theoretically safe if the meat was carefully defrosted in the fridge and was only out of the freezer for 2-3 days but refreezing multiple times will cause oxidation ...

Sebastian2I

Clarification of last post: You would double one of the half-reactions in order to make the number of electrons involved the same as that of the other half reaction. On this same point, the standard potentials of the cathode and anode do not change when the reactions involved are multiplied by a fac...

Sebastian2I

Nevermind I've got it. If anyone is having trouble understanding this - when converting from cell diagrams to reaction the reaction implied by the diagram needs to be reversed/doubled/etc as necessary to fit the rule that the rightmost reaction must be a reduction (cathode) and the leftmost one must...

Sebastian2I

Yesterday, I brought a bag of sliced apples for lunch with me but by the time I got to eat it, it was already browning. Then I remembered how my mom used to cover apples with lemon juice to keep them fresh all day long! The acidity of the lemon slows down the browning because ascorbic acid reacts w...

Sebastian2I

The solutions manual lists the reduction half-reaction for the diagram C(gr)|H2(g)|H+(aq)∥Cl−(aq)|Cl2(g)|Pt(s) as Cl2(g) + 2e- --> 2Cl-(aq). This makes sense as a reduction reaction, but I thought that the diagrams were written in the order (reactants|products) and this looks like the reverse. Is th...

Sebastian2I

I was just in a problem-solving session for CHEM14BL where we discussed a titration of a solution of hydrochloric acid with one of sodium hydroxide. The end result was a solution of water and sodium chloride for which the pH was zero - since Na+ comes from group 1 and is, therefore, a spectator ion ...

Sebastian2I

My family has an ongoing debate if adding salt to pasta water makes the water boil faster or slower. The argument for faster is that adding salt disrupts the surface tension of the water, and contributes to it boiling faster. The argument for slower is that salt raises the boiling point of the wate...

Sebastian2I

My family has an ongoing debate if adding salt to pasta water makes the water boil faster or slower. The argument for faster is that adding salt disrupts the surface tension of the water, and contributes to it boiling faster. The argument for slower is that salt raises the boiling point of the wate...

Sebastian2I

Great topic and posts! Good & Tasty Chemistry :-) Take a look at: https://www.zmescience.com/science/cooking-delicious-chemistry/ https://www.acs.org/content/acs/en/education/students/highschool/chemistryclubs/activities/food-and-chemistry.html I should look at these for Q&A ideas. I'm gett...

Sebastian2I

Having once shattered a thin glass jar as I tried to heat its contents over a stove, I can personally attest to the importance of this.

Sebastian2I

If anyone is interested in learning about the chemistry behind french fries, and why McDonald's should never have switched from using animal to vegetable fat, I would highly recommend Season 2, episode 9 of Malcolm Gladwell's podcast - Revisionist History. The episode is entitled "McDonald's Br...

Sebastian2I

If you're interested in learning more about the science behind baking and chemistry, I would totally recommend watching a TedEd video about the science of cookies! That video got me interested in baking in the first place since I was excited to learn the science behind it. And as a reward for learn...

Sebastian2I

Also speaking of acidity, if anyone has any good cooking or baking recipes having to do with oranges they would be much appreciated - I currently have a surplus of oranges on my hands.

Sebastian2I

I just made some spicy butternut squash soup and served it alongside some salad with balsamic vinegar. I noticed how the acidity of the salad went well with the relative sweetness of the squash and I remembered Lavelle's reference to this last quarter :)

Sebastian2I

How exactly could one make sure that an electrical current is produced reversibly?

Sebastian2I

I was just reading about non-stove cooking and stumbled across a passage describing how marination not only imbibes food with extra flavor but also breaks down proteins in meat dishes - when the marinade contains an acidic element, as it usually does - essentially "cooking" it without requ...

Sebastian2I

Oh wow! Very interesting to see you put Chem to action and apply it to real world stuff! I suck at cooking but maybe once I get a little further in Chem, I'll be the next Gordon Ramsey??? If you're just getting started I would recommend YouTube for some great instruction in kitchen techniques. Chan...

Sebastian2I

The same email also included questions 4D.15, 4D.17, 4D.19, 4D.21, 4D.23, 4E.5, 4E.7, 4E.9, 4.29, 4.31 from the textbook as good practice for the beginnings of Thermochemistry that will be on the midterm.

Sebastian2I

If you're looking to get into old stuff I would highly recommend The Velvet Underground, King Crimson, The Cure, and Blue Öyster Cult. In terms of new recommendations, Mon Laferte and Kali Uchis are some of my favorites.

Sebastian2I

Does anybody have the answers collected for some of the past weeks' UA sessions? I, unfortunately, haven't been able to make it to many and I am trying to review old worksheets to study for the midterm so I would really appreciate being able to check my work :)

Sebastian2I

In the run-up to the first midterm of Chem 14B, does anyone have any good tips they think might be especially useful at this time?

Sebastian2I

Hey all! I have recently begun teaching myself to cook and have been amazed at how directly the lessons of general chemistry apply to the kitchen. This past weekend I was reading about how you shouldn't blend hot mixtures because the blades will release steam easily causing nasty burns and remembere...

Sebastian2I

The solution manual specifies that because the Ka value for the second ionization is significantly lower than the first it can be ignored when calculating pH. What exactly is the threshold difference in values for this?

Sebastian2I

I suppose this has been said many times over by now but thank you so much for sharing your story, Ashley! I really admire the attitude that you have towards the opportunities in rotations and I myself try to enjoy everything that I learn as an undergraduate because this is probably one of the greate...

Sebastian2I

Hi there! Typically, if the pH at a given time is lower than the pKa, then you will have more protonated species. In this case you will have more HA at this given pH, which has no charge, so the solution will be more neutral at the given pH. The pKa basically tells you what the pH needs to be for t...

Sebastian2I

Thank you! I can see how that makes mathematical sense

Sebastian2I

The first thinking point in this section asks how the extent of deprotonation of a weak acid might be affected by its initial concentration. The best explanation I could think of is that a weak acid would have a relatively robust conjugate base which could deprotonate the water molecules and so affe...

Sebastian2I

Semi-related but whenever I come back to this forum after a while it will refuse to accept my username and password and I have to click on "Forgot password" and submit them again there (This usually works to log me back in). I can live with this if no solution is available but it is a bit ...

Sebastian2I

I have this problem where the counter next to my username always displays one more post than I have actually done - according to my stats when I check them on my profile overview and based on my point count for when grades are assigned. Does anyone know how to fix this?

Sebastian2I

I apologize if this has already been asked and/or answered but since there appears to be no forum for posting questions concerning the Acids and Bases Equilibrium focus, should we post these on the chemical equilibrium page?

Sebastian2I

I struggled with this problem for a really long time and eventually realized that I had made a multiplication error at some point. Whenever you can't find the right answer but your reasoning seems sound after you double-check it, this is usually the case.

Sebastian2I

To clarify, you do not need to use 1/K just because you began with an initial concentration of product rather than reactant. This is accounted for in the fact that the equilibrium expression will subtract the change in X

Sebastian2I

Thank you! Having reexamined the constant of equilibrium expression I can see that the ratio of one reactant's concentration to another's does not come into play so long as their product (the result of multiplication) compared to the concentration of product is the same ratio as the equilibrium cons...

Sebastian2I

If you have a reaction with two reactants and one product, say the ammonium synthesis reaction, and more of a single reactant is added, would all of this be used up in synthesizing product? Could you ever have a situation where the adding of just one reactant could result in excess of that reactant ...

Sebastian2I

In addition to reviewing your notes and making sure to read the textbook sections, I would definitely recommend watching YouTube tutorials on the topics because they clarified a lot of the things which I didn't understand from just the other two. I have found that looking for outside tutelage on a t...

Sebastian2I

I could also really use some study support over the break to prepare for the next quarter. Please let me know if you go ahead with it!

Sebastian2I

I'm planning on spending some quality time with my cats and the family. In terms of book recommendations, I'm reading Dune by Frank Herbert right now and it's incredibly interesting - also recommend anything by Haruki Marukumi. Weird stories take your mind off the insanity of the real world :)

Sebastian2I

Considering the Lewis and VSEPR model for compounds helps a lot in this regard because it depicts the direction of atoms' pull on electrons, so it's easier to see if two dipole moments cancel.

Sebastian2I

I think Professor Lavelle mentioned that our very first lecture in 14B will be about calculating equilibria for weak acids and titration.

Sebastian2I

On this same note, the general assumption when dealing with anions forming part of a coordination compound is that they are in their most common oxidation state, which can typically be determined by examining their placement in the periodic table. Chlorine and Fluorine for instance form a -1 anion, ...

Sebastian2I

Are there any exceptions to the atom-spacer-spacer-atom condition for chelation or can this be considered absolute?

Sebastian2I

Dear Dr. Lavelle, I would like to thank you for a truly amazing quarter and for providing me with an excellent introduction to science at a collegiate level. My high school did not have any AP, IB, or Honors Chem courses, so exploring concepts and phenomena is as great of detail as we did was an utt...

Sebastian2I

Please disregard the above post. For anyone confused by this distinction, the Ka of an acid is given by calculating the quantity of the reactants from its interaction with water and dividing the resulting value by the quantity of the products. As such, a higher Pka is indicative of a more acidic com...

Sebastian2I

How is it possible to end up with negative Ka values for extremely strong acids when it is calculated from the concentrations of products and reactants? Wouldn't all values concerned have to be positive?

Sebastian2I

To be clear is the dipole-dipole interaction between water molecules and acids the only reason that reaction occurs? In the absence of this attractive force, it is my understanding that particularly strong acids would still deprotonate but would they not form H30+?

Sebastian2I

Thank you for the explanation! This was all extremely helpful!

Sebastian2I

I beleive that since the Cl molecules have a -1 charge because of their 3 lone pair electrons, the shape of the molecule is asymmetrical which means that the dipole moments do not cancel. It might also have something to dow with the fact that the electronegativity difference between Cl and C is hig...

Sebastian2I

Please disregard my previous post. If anyone is confused on this subject: A bond is polar if it is between any two atoms of differing electronegativities (the tendency to attract additional electrons). Since all atoms have differing electronegativities, any bond other than those between two of the s...

Sebastian2I

The solution to this problem says that CH2Cl2 is polar because the hydrogen bonds are of a different magnitude than the Cl bonds. Is this a reference to the difference in formal charge between these atoms and the carbon atom?

Sebastian2I

Would the hybridization scheme then be sp3?

Sebastian2I

How many σ-bonds and how many π-bonds are there in (a)H2S and (b)SO2? The answer key gives the solution to this problem as 2 sigma bonds and one pi bond, with a resonance structure that has 2 of each. I drew the Lewis structure and the placement that results in a zero charge is the one in which the ...

Sebastian2I

Does anyone else (with the online textbook) have the exercises for this section showing up with molecular formulas missing all over the place? As an example, exercise 13 for me looks like this: Draw the Lewis structure, VSEPR formula, molecular shape, and bond angles for each of the following specie...

Sebastian2I

Does a single "E" in a VSEPR formula represent a single electron or a single region of non-bond electron density?

Sebastian2I

Slight digression but I ran into a problem with this question where I looked up the molecular formula for thionyl chloride and then looked at the images associated with it to check my work, and the depiction I found had no lone pairs on the central sulfur atom. Calculating formal charge debunks this...

Sebastian2I

I know that OClO will have a lone pair on the central Oxygen atom and this is responsible for the bond angles slightly less than 120 because it is a distorted trigonal planar shape, but does the additional unpaired electron on the same Oxygen play any role in repulsion? Is the electron structure tet...

Sebastian2I

Thanks! This really helped!

Sebastian2I

Also if two resonance structures exist for which one has only one formal charge but it's located on the central atom and the other has two formal charges but they're located on the outlying atoms which one is more preferable? Does limiting the number of formal charges take precedence or keeping form...

Sebastian2I

In question five didn't it say that the extra electrons associated with the model should be given to the atom with the greater electronegativity? Yet Cl is more electronegative than O and it's also at the center. Could someone explain when to apply one principle and when to apply the other?

Sebastian2I

Thanks! I must remember to take formal charge into consideration whenever I run into something like this.

Sebastian2I

Draw the Lewis structure of each of the following reactive species, all of which are found to contribute to the destruction of the ozone layer, and indicate which are radicals: (a) chlorine monoxide, ClO. I understand how this species is radical because the number of valence electrons available is o...

Sebastian2I

I ran into the same problem and I also think that the answer key in the online textbook is likely mistaken. I have noticed that its missing answers for certain questions and the explanation from the physical one makes the most sense.

Sebastian2I

Does an exception like this occur in every period down the periodic table when a second electron occupies the 2px orbital? Like are the ionization energies of Sulfur, Selenium, Tellurium, and Polonium all slighter lower than those of Phosphorous, Arsenic, Antimony, and Bismuth respectively? If no, w...

Sebastian2I

To be clear, by "unpaired electrons" the problem is referring to instances of orbitals only occupied by one electron in the ground state of an atom, right?

Sebastian2I

I understand that we won't need to use orbitals with l values higher than 3 for this class but the textbook said that these were the only values that chemists needed in practice so is there some continuity in the nature of higher-level orbitals? Does the pattern of sub-orbital shapes repeated itself...

Sebastian2I

Thanks so much! This was definitely helpful!

Sebastian2I

The number of protons (atomic number) of each element determines the nuclear charge.

Sebastian2I

Also, don't forget to take into account the two different magnetic fields that electrons can occupy inside the same orbital - for every space allotted by calculating the total potential values of ml, there can be a maximum of two electrons, according to the Pauli exclusion principle.

Sebastian2I

Just to be clear, the energy in which higher values of n are described as "higher" refers to the energy necessary to excite an electron from the ground state to that level, right? Or is this different for multi-electron systems? Additionally, as you examine progressively higher values of n...

Sebastian2I

Would/will it become important for us to understand how changes in electron configuration occur at the orbital level following ionic or covalent bonding?

Sebastian2I

I seem to recall seeing a Lewis diagram with two lines (each representing two shared electrons) linking two atoms. Does this occur and, if so, under what conditions/between which elements is it most likely to be found?

Sebastian2I

Thanks so much! This was extremely helpful!

Sebastian2I

On question 23 of the Sapling Homework, it says that the "electron affinity" is equal to the difference between the energy of the electron released and the photon. Would this make the electron affinity the same as the work function?

Sebastian2I

I followed these steps and ultimately arrived at a situation where I knew everything except the values of n1 and n2 inside the brackets. Is there no other way of solving other than guessing and checking? Am I missing some extremely obvious trick of algebra?

Sebastian2I

Could someone explain how to arrive at the correct uncertainty in position? I used 10m/s as the uncertainty in speed because the problem said +/-5 and 8 as the mass to get 80*deltax >= h/(4pi) and got 6.59*10ˆ-37. I assume I got the uncertainty in velocity wrong but if so how would I get it correctly?

Sebastian2I

Was anyone able to calculate the correct number of photons emitted over the time interval? I used the equation corresponding to the wave model of light to find the number of Joules per photon emitted but I'm not sure how to get the correct number of photons.

Sebastian2I

Although Prof. Laurence advised us against fixating upon material outside the realm of the lectures, I have noticed that for many of the textbook problems knowledge of chemical formulas by compound name has been required. How important will it be for us to know how to do this on midterms and the fin...

Sebastian2I

The police are monitoring an automobile of mass 2.0t(1t=103kg) speeding along a highway. They are certain of the location of the vehicle only to within 1 m. What is the minimum uncertainty in the speed of the vehicle? Can you use as your defense the argument that the uncertainty principle prevents t...

Sebastian2I

Thank you very much! This has definitely been extremely helpful!

Sebastian2I

Could someone please explain how to determine the initial and final energy levels from the wavelength? I was able to find the change in energy which should have taken place (deltaE = 1.94*10ˆ-18 J) but I am not sure how to proceed from here.

Sebastian2I

Is the photoelectric effect specific to samples of metal because of the distinct electron structure of metallic bonding? Additionally, could the photoelectric effect be related to the idea of the atomic spectra i.e. the threshold energy for displacing an electron corresponds to a particular value of...

Sebastian2I

These explanations were really helpful in picturing the intensity of light! However, I looked it up myself when I ran into this question and found a diagram saying that the intensity of light could be conceptualized as the amplitude of the waves. I think this works in conjunction with the idea of li...

Sebastian2I

Hi! This is semi-related but I was a little confused with part a of this same question. Does determining the net ionic equation just refer to finding the balanced chemical equation for the reaction? Are there any other steps to be taken?

Sebastian2I

Thank you guys so much! I'll get through the modules in preparation for Friday and next week's lectures and then review the light properties modules after to round out my understanding of everything.

Sebastian2I

Should I watch these three module videos or just proceed from Molarity and Dilution to the Photoelectric Effect? Are these videos essential to understanding the subsequent content?

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