CHEMISTRY COMMUNITY

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Q: What is the dullest element?
A: Bohrium

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Q: What do chemists call a benzene ring with iron atoms replacing the carbon atoms?
A: A ferrous wheel!

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The rate laws only use the reactants because they are based on the initial rate of the reaction which is when no product has been created, or if it has it is so little that it is negligible. Therefore, you only need to account for the reactants in the equation.

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https://cen.acs.org/physical-chemistry/ ... eb/2018/06

Geochemistry! Cool article about chemistry in nature!

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https://www.sciencedaily.com/releases/2 ... 093626.htm

I thought this article was an interesting mix of chemistry and biology! Wanted to share!

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Can you use the standard cell potentials to determine which way would be spontaneous and then use that to find which is the cathode and which is the anode?

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The book describes corrosion and ion selective electrodes/glass electrodes In a lot of detail that wasn’t talked about in class. Should we try to understand this in the same detail as in the book or is what we learned in class okay?

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A positive cell potential means that reaction is spontaneous, while a negative one means it is non spontaneous.

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That seems like a typo. The H+ shouldn't just disappear.

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In the table in the appendix, you can look at the E of each. You then use those numbers to determine which one is the cathode and which is the electrode in order for E cell to be positive. This then tells you which one is reduced (whichever one is the cathode) and which one is oxidized (whichever on...

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It looks right to me!

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Carbon isn't included because it is being used as an electrode but does not effect the redox reaction.

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I thought this was interesting and shows the interdisciplinary nature of STEM fields!

https://engineering.nyu.edu/news/nyu-re ... duce-waste

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What did the cashier say to Gibbs when he bought an energy drink?

"Don't worry about it. It's free.”

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Gibbs free energy is the maximum potential amount of reversible work that can be performed on a thermodynamic system. So a change in this means more or less work can be done on the system which affects the systems change in enthalpy, temperature, and/or change in entropy.

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The equation ∆G=∆H-T∆S shows that even if ∆H and ∆S are negative, T can change the value of the second term and affect spontaneity. More specifically, if ∆S is negative, then the second term would be positive, and if T were great enough, it would make ∆G positive, which would make it non spontaneous...

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We can not determine spontaneity based on delta H because the total free energy (delta G) is also affected by t∆S, so at certain temperatures, the free energy would still be positive and it would not be spontaneous. Basically there is another term which must be accounted for in order to determine sp...

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A negative delta G means that free energy is being released from the system. This means it is spontaneous (rather than requiring energy to be added to the system which would be non spontaneous). Also, since energy is being released, it increases the entropy in the universe by putting more energy int...

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Yes, I think you use the equation which allows you to plug in the given information. In other words, you decide which equation to use based on the information given in the problem.

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I think that they occur when there is an outside stimuli that causes it. I don't think they are just naturally occurring. But I'm not totally sure.

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I think they are both ways to find a change in total enthalpy of the system, so it depends on the given information to see which one is easiest to use.

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I think you can choose!

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16 sodiums walk into a room. Who's next?

Na Na Na Na Na Na Na Na Na Na Na Na Na Na Na Na Na... BATMAN

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If Avogadro calls, tell him to leave his number.

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An endothermic reaction requires energy, while an exothermic reaction releases energy.

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How do you use the equilibrium constants to predict solubility? Do you just see which way the reaction favors, and if it is the side with (aq) you know it is going to be soluble but if it favors the other direction then it won’t?

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In the textbook, there is a question asking to predict the effect of compression on the equilibrium composition of the reaction CO2 (g) + H2O (l) —> H2CO3 (aq).

Since H2O is a liquid, that means there is one gaseous/ aqueous molecule on each side, so would compression not affect the equilibrium?

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What kind of dogs do chemists have?

Laboratory retrievers.

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What do you call a wheel made of iron?

A ferrous wheel.

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Can someone help explain when you use Ka, Kb, or Kc? Are Ka and Kb used whenever H30+ or OH- is a product?

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I tried to write a joke about the periodic table... but I wasn’t quite in my element.

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I think it is more significant that gases effect activity (which is a concept that is a little more complicated so Dr. Lavelle said we don’t need to really focus on it) and activity is how equilibrium constants are found so therefore gases explain equilibrium constants.

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Yes that is right. You add x proportional to the coefficients in the equation.

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So Kw is equal to [H+][OH-]. Is pKw always equal to 14? And if so, why?

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Salts that are acids lower the pH of the solution, while salts that are bases raise the pH of the solution. For the most part, for salts that are acids the cation is the ion that reacts with water, while for salts that are bases it is the anion that reacts with water.

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They are BeO, Al2O3, Ga2O3, SnO2, Sb2O5, and PbO6.

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I think we should probably be familiar with the main ones which are in a chart on page 724 of the 7th edition book!

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Also for the s and p block, as you move left to right across the period, the oxidation number goes +1, +2, +3, + or -4, -3, -2, -1.

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So single bonds are sigma bonds. They are an overlap of two orbitals in one place. They can rotate. Pi bonds occur for double and triple bonds. Double bonds have 1 sigma and 1 pi bond, while triple bonds have 1 sigma and 2 pi bonds. Pi bonds basically are an overlap of two orbitals in two places. Th...

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Yes exactly. The true bond length is a mix of the single and double bond because of resonance.

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The formal charge on the other two Iodine atoms is 0, so you need to have 3 lone pairs for the formal charge to be -1 on the central atom in order to give the molecule the -1 charge.

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Do Double bonds count as 1 single region of electron density or two?

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Square Planar is when you have 4 bonds but 6 regions of electron density.

Seesaw is when you have 4 bonds but 5 regions of electron density.

Does that help?

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But bond order just refers to how many bonds there are between two atoms, so it isn't hard! Just requires counting.

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When we draw a dipole, do we use the modern convention or the other one? In other words, should the arrow point towards the negative charge or the positive one?

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When I tell chemistry jokes, I normally get a good reaction.

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Do you want to hear a post about Nitric Oxide?

NO

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They don't have to be double bonds, there just have to be three regions of electron density.

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Well a single bond has 2 electrons, so I would assume it means that. A double bond has 4 electrons, so that would be its electron density. But i'm not totally sure.

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Basically VESPR is the 3D representation of the lewis structure. However, we won't be asked to draw them, we just have to be able to name the shape and draw the lewis structure.

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I know my friends don't like chemistry jokes... but I tell them periodically.

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In High School, I thought we learned the hydrogen bonding was the weakest form of bonding, but my notes show that Dipole-Dipole bonds are actually weaker. Why is that?

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Polarizability is how easy it is to pull electrons from one atom in a molecule towards the other. When this happens, a dipole moment occurs, because the electrons are pulled towards one of the atoms, making it more positively charged. Dispersion forces have fluctuating electron distributions, where ...

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A professor at UCSC was able to make a plastic that doesn't leach chemicals into its surroundings (like PVC does)! This can have massive environmental effects if companies will start using her new nonmigratory plasticizers.
https://www.eurekalert.org/pub_releases ... 103118.php

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OMG! Did you hear that Magnesium and Oxygen are a couple?!

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OMG! Did you hear that Oxygen and Magnesium are a couple?!

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Fluorine is really unstable when it has a positive charge, so much so that I don't really think it ever happens. So it is a bad thing because it just isn't realistic or really possible.

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Nobel Prize in Chemistry Goes to a Woman for the Fifth Time in History I know this is from earlier this month, but I think it is super cool and wanted to share! https://www.nytimes.com/2018/10/03/science/frances-arnold-nobel-prize-chemistry.html?rref=collection%2Ftimestopic%2FChemistry&action=cl...

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That is confusing to me too, because I thought if it has a high polarizing energy, it will be more likely to give an electron away/ take an electron, making an ionic bond more likely.

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I'm a little confused. What is ionization energy and how is it different from electronegativity?

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So basically for A), we know that there is 1 valence electron that will be in an s orbital, so they wrote ns^1 to mean at any energy level, the orbital will be the s shape, and there will be one electron in the orbital. For B), we know that the valence shell of any of the atoms (at any energy level)...

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To add on to that, it basically helps calculate the orbital that a specific electron is in by telling us where the electron will probably be.

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We don't need to know how to do equations with the wave function, but it is important to know that the wave function squared is gives you the probability of finding an electron in a certain area (that energy shell).

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I think it is basically the same equation, but it is just trying to determine the change in frequency when it is excited, rather than the frequency at a certain instant.

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This is confusing to me too... Do you mean that if there is energy absorbed from the light by the metal that is exactly the same as the work function, the electrons are excited but remain with the metal rather than being ejected?

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Hi there,

In the textbook, Robert Millikan's experiment to determine the charge of an electron using oil droplets was explained, but I don't really understand it. How could the "smallest increment of charge between droplets" be the charge of one electron? What does that mean?

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I'm struggling as well, but I think you have to use stoichiometry to solve for grams of Cu(OH)2 starting with 2.00 g NaOH and then again with the .80 mL of Cu(NO3)2 to determine which is the limiting reactant. However, I'm having some trouble making the equation at the moment.

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In some of the homework problems they asked for the formulas of compounds given their names (E7 in particular asks "epsom salts consist of magnesium sulfate heptahydrate. Write its formula.) I'm not sure how to do that. Can anyone help?

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You can use the equation Vinitial*M initial = Vfinal*M final to solve for M final

You find M initial by converting the 5.00 g KMnO4 to moles per liter using the known 150 mL volume and stoichiometry.

Then you put that concentration and volume into the equation and solve for M final.

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