CHEMISTRY COMMUNITY

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In the same way, raising logx to 10 will cancel the log because standard log is base 10 (log10x). Ln is loge(x).

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it doesnt matter which order you do, as long as you can isolate an exponent x or y to get the respective rxn order. The numbers of one of the reactants in both trials should cancel out. So, as long as the variable placements are consistent it doesn't matter, right? Or is the placement not a factor ...

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For the Arrhenius Equation, why is A approximately = 1 in most cases in this class?

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This is all based on the equation that Ecell = Eright - Eleft and as Eleft is the oxidation cell, you 'flip' the oxidation cell.

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Even if CCLE crashes (again oof), though, the test saves every 2 minutes so we'll be good!

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Vinita Saxena 2I wrote:Yes, it can change if the temperature changes, that is the only way it can change

Isn't the addition of a catalyst also a way to change it?

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What does Gene Block’s announcement mean for our final in this class as gatherings of more than 100 people?

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And also then why does k = 2k2?

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Why is 2k1k2 / k’1 equal to k (of observed rate law)? Why do these agree with one another?

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n is the mols of electrons transferred! Make sure not to find a common multiple, then, for example if for a reduction 2 electrons are transferred whereas for an oxidation 3 electrons are transferred -> common multiple 6 when balancing equations and 6 electrons are transferred; (n=6).

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You find K2 by using the Vant Hoff equation you wrote down: ln K2/K1=-ΔH°/R [1/T2-1/T1] After finding K2, square root it to find the H3O+ concentration. Use the concentration to find the pH. This pH is the neutral pH at 10 degrees C. Compare that number with 7 to see if a pH of 7 is acidic or basic...

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If your reaction involves conductive metals like Ag and Cu, though, you do not need to involve Pt as a conductor for your cell diagram.

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What's the equation needed to convert K back to Kc? I assumed you would just rearrange the Kc to K equation, but I wanted to ask just to be sure. aren't those the same Not according to the book :( Look at the very last part of section 5J.3, it talks about converting K to Kc when using Van't Hoff eq...

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If you write [A] vs. time for a 1st order run, though, it'll show exponential decay so make sure to have it in ln form!

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Why is there work done in this system, and how do we find Ecell? I keep calculating it to be 0V as the cathode and anode are reducing/oxidizing the same reaction in reverse to one another (?)

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I'm a bit confused as to how to find n in reactions and I'm a bit confused too with what it represents.

For example,
for the reaction Mn + Ti2+ <--> Mn2+ + Ti n=2, but I'm not sure as to why.

Could someone help explain?

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Why are all reaction rates 'positive' if the [reactants] decreases in exchange to an increase in [products] (for a forward reaction, in example)?

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What does the eventual heat death of the universe say about its entropy and enthalpy relationship? Is all of the energy in the universe in its potential energy form?

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Lavelle said that the reaction from diamond to graphite was spontaneous but had a very high activation energy and would occur very slowly. Does this mean that over time, say a few trillions years, the diamond is slowly collecting enough energy to overcome the energy barrier? Or would the reaction e...

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MariahClark 2F wrote:Wouldn’t the reaction be exergonic since it’s giving off energy and not requiring it?

In ATP's case, yes, but not all hydrolytic reactions are exergonic -- when it requires more energy than it gives off.

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Yes, when a battery is dead, the system has reached equilibrium -- though I'm wondering now if it's possible to 'revive' a battery or replace its galvanic cells concentration gradient?

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Do higher cell potentials within a cell indicate anything about the rate of the reaction or just the spontaneity?

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When Platinum is an electrode, as it is carrying electrons, on an atomic level is it getting reduced and oxidized continuously as electrons are passed from atom to arom

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If you look at the lewis structure of ozone, it does have individual oxygen formal charges but the overall formal charge is 0 and there is resonance; the oxidation number of the whole molecule of ozone (not of the individual oxygen atoms that compose it) is thus 0.

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Will we ever examine proton transfer in redox reactions and how that is linked to electron transfer, as that bit has confused me in bio classes?

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Kate Swertfager wrote:Are all diatomic molecules neutral charge?

Diatomic molecules of the same atom (homonuclear) should all be neutral charge.

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If you have three galvanic cells all linked individually with the other two, will the two with the most favorable change in Voltage react together or would there be a system mixed reaction(s)?

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How are Voltage and Current related? Will we ever see an ammeter included in diagrams in this class -- will we relate amperes and volts in an equation?

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Van't Hoff relates a reaction's equilibrium constant Keq with temperature, standard enthalpy, and standard entropy -- so it'd be useful in modeling how the equilibrium constant changes due to T, S, and H changes I assume in a more definite way. [url]https://en.wikipedia.org/wiki/Van_%27t_Hoff_equati...

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I think it just has to do with the ways to write an equation: C is usually put at the center as it is a central atom within this compound, but the more electropositive atom is usually put at the right (C) and the more electronegative at the left (O). Those conditions conflict here, so both ways of w...

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Veronica Lu 2H wrote:Leo goes Ger [censored]
Losing electrons = oxidation
Gaining electrons= reduction

Similarly, OIL RIG helps me:

Oxidation is Loss

Reduction is Gain

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Going off what happened in 14A and in his syllabus, he does not curve the midterm but a 50% in the class is a C, so in that way he does curve the final grade to help those that are close to failing. Does this mean all other grades are curved too? Like how low does an A or an A- go? Or does it not a...

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The Gibbs free energy can predict the spontaneity of a reaction at different circumstances / environmental conditions. In this way, it can predict at what temperature -- for example -- a reaction becomes spontaneous if all other factors are constant.

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Should we familiarize ourselves but not memorize the equations in thermodynamics for the midterm? Or should we focus on memorizing some of them too -- ones that won't be provided on an equation sheet?

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The more material there is capable of increasing disorder, the higher the entropy potential exists.

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Gas molecules are higher energy and occupy the entirety of the volume of a container as they 'bounce' off of one another and off of the container; it has a lot to do with the decreased density and the increased speed of the particles when they're in their gaseous phase.

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Wrev is an ideal situation with constant Temperature; Wirr is the more realistic and non-constant Temperature scenario and thus it does less work.

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Is W2/W1 always equal to V2/V1?

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Today, we talked about in class that in an open system with an exothermique rxn there is expansion work being done.

If it was a closed system, is there no expansion work? Though pressure isn’t constant?

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If the problem indicates that the system is under a constant pressure, then you would use the w=-P∆V equation to calculate the work done. If the problem instead indicates that the reaction is an isothermic expansion where pressure is not constant, then you would use the equation for a reversible re...

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You're given pKb so you can find Kb. However, in the reaction given you need Ka because HF is an acid. Solve for Ka by using Ka*Kb=Kw, K =1*10^-14. Ka is now your equilibrium constant.Then use the given initial concentration of hydrogen fluoride, 0.12M, and complete an ice table using the Ka consta...

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Will it focus more on the new content than what we’ve already learned for Test 1 or just even distribution?

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504999222 wrote:If the pressure goes up, would that mean the volume would go down?

Can’t pressure go up with T going up from PV=nRT with no effect on volume?

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A bomb calorimeter would be an isolated system; a closed system would be the ‘cup’ with the external pressure image.

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This problem involves 982 J = 492 J + w so I calculated the answer to be 490J, but the back of the textbook says its 90 x 10^2 J. Could someone please explain if that's correct?

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Bryan Chen 1H wrote:No, strong acids and bases also have Ka and Kb i think, it is just very large (and they also dissociate completely) so there's no real need to use it in problems

What, hypothetically, would be a situation that we use strong acids'/bases' Ka and/or Kb?

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Basically, this is because steam has undergone a phase change from liquid to water vapor (vaporization). Vaporization requires a lot of energy. When steam touches your skin, it will release a lot of energy as it cools to form liquid water. Water, while at the same energy, does not have the same lat...

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Can someone reiterate how temperature remains constant during a phase transition? Does it then suddenly just spike/fall after the transition is complete? A bit confused just by the process of it all. How is the steam causing burns example applicable?

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The only atoms I can think of capable of making quad bonds are certain transition metals -- 1 s bond, 2 p bonds, and 1 d bond.

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The difference here just has to do with units used, though Kp will include all gases yes.

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K is a fixed value for the reaction, while Q varies if the reaction is/is not yet at equilibrium and we can compare the two values to determine if the reaction is at equilibrium or not.

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Since the acid-base equilibria we're exploring right now is dependent on Kw, at 25 degrees Celsius, how different are reactions with organic life such as the human body where regular temperatures are completely different (37 degrees C for human body).

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The example Dr. Lavelle gave in class was if you added Helium to a reaction occurring within a sealed container. While the pressure of the reaction is increasing, it has no effect on the equilibrium because adding gas doesn't have any effect on the actual concentration of either the products or rea...

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At this point, everything we've done in lecture which seems to cover both outline 1 and 2.

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The video modules are available on the class website too and those really helped me over winter break, so use those too to study and review!

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Tai Metzger 3K wrote:I hope I can help you resolve this haunting question. I believe that it is a physical reaction because no bonds are broken.

I thought, though, that salt dissolving in water meant that the ions bonds were broken -- making the solution homogeneous (?)

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Dear Dr. Lavelle,

The quarter just started, but you've already introduced us to so many resources and have made access to help readily available. With all my other classes, this constant makes me so much less stressed.

Thank you so much!

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This is a question that has haunted me for many years: Is salt (NaCl) dissolving in water a physical or chemical change? In water the ions are technically separated as the sheer [H2O] is powerful enough to separate them (the amount of ion-dipole interactions is more and stronger than the ionic bonds...

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For 5.57 of the Focus 5 Exercises, does anyone know how to complete the last part about finding the [NO]? We're given the initial [] of one reactant and the equilibrium [] of one product, but there's 2 reactants and 2 products and that's two unknowns.

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5.39 on the Focus 5 Exercises involves Table E.2, but I can't seem to find that table in my textbook. Does anyone else have this problem?

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It's also important to remember that the significance of K is only considered strong when it is either >10^3 (strongly favor products) or <10^-3 (strongly favor reactants). Anything in between those two values still favors one side or the other (except for the rare circumstance at 1), but isn't cons...

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Has anyone solved 5I.23? It involves CO(g) + 3H2(g) -><- CH4(g) + H2O(g) and we know the initial [] of CO is 0.2 mol/L and H2 is 0.3 mol/L (the products are 0) and that [CH4] at equilibrium is 0.478, but we don't know anything about [H2O] at equilibrium. How do we solve for Kc with that unknown? I t...

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