CHEMISTRY COMMUNITY

JacobHershenhouse3G

Lyndonthis is so helpful, thanks

JacobHershenhouse3G

Because at a higher concentration the electrical potential is higher (E) so you can reasonably state that the higher E is the cathode if you want your Ecell to be positive.

JacobHershenhouse3G

K is the equilibrium constant and kr is the rate constant, symbolizing different constant values with different meanings, applied in different equations but they are related. K is equal to the overall forward rate constant over the reverse rate constant because at equilibrium the forward and reverse...

JacobHershenhouse3G

Think about the steps of a given reaction being considered fast or slow. The two contingencies are at either ends of the spectrum, just like how acids and bases can be strong or weak. So, the rate of the whole reaction is determined mostly by the slowest step of the reaction because the fast step(s)...

JacobHershenhouse3G

It seems that you have the right idea and the book may have a typo. the oxidation state on a lone ion is the charge so it makes sense that In3+ is reduced to In2+ with the gain of an electron.

JacobHershenhouse3G

You just have to think about it in terms of the anode and cathode and keeping in mind that the material is the same at both. So the sum of the standard potentials cancel because they are equal and opposite in magnitude.

JacobHershenhouse3G

Think about gibbs free energy as the energy still availible (non-expansion) for the system to do work. This definition is why gibbs free energy is a useful concept and explains spontaneity.

JacobHershenhouse3G

H is set to be an arbitrary zero because the cell potential is a different between the the voltage of two points. This way we can compare cell potential of different setups. Its all relative

JacobHershenhouse3G

When you're solving for k at different temperatures, you're going to be using standard enthalpy and entropy values, so these dont change based on temperature. Thinking back to the first midterm though, we can remember that k does depend on temperature so that's how this concept can be applied to the...

JacobHershenhouse3G

I don't think we are expected to know extraneous values, but you should know how to use them in equations/apply them and what they mean when given.

JacobHershenhouse3G

e is an irrational number in math that has the special property: de^x=e^x (derivative equals the value). As well, natural log is the log base e of x so it applies here that anything set to the power of its own log "cancels" and leaves you with the value of the log! Hope this helps :)

JacobHershenhouse3G

Its possible to have 0 entropy, when there is no degeneracy at absolute zero. At higher temperatures, vibrational, translational, transitional entropy are spontaneous and add to the total entropy. This is why we have been considering entropy at 0 K because then the S= K In(W) holds true (does not in...

JacobHershenhouse3G

You can think about Gibbs free energy as a conglomeration of enthalpy, temperature, and entropy because they are all related to energy and the amount of work a system can do, so the GFE equation brings them all together. Hope this helps :)

JacobHershenhouse3G

We will probably not be asked to derive equations, I would focus on the practice homework problems dealing with thermochemistry instead of studying the proof.

JacobHershenhouse3G

Big difference! w is representative of work, while W represents degeneracy. They are each used in various equaitons we've looked at in class; work is more related to energy, while degeneracy is closely tied to entropy. Hope this helps! :)

JacobHershenhouse3G

As a pre med student, this makes me feel much more confident in this course and in the pre med process. Thank you for sharing your experience and I will definitely learn from it!

JacobHershenhouse3G

I know that deltaU= q + w but how do you differentiate if work and temperature is applied to or by the system from the surroundings? I seem to keep messing up signs and would like some clarification.

JacobHershenhouse3G

Hello, I'm just wondering if we should know all of the pressure unit conversions for the midterm/ if it will be given on the exam. Some of the homework problems include conversion steps so I'm not sure.

JacobHershenhouse3G

The thing that works best for me with solving problems like this is to think about it like solving a puzzle. Each equation that is given gives you one piece of what you need to find your answer (or else it wouldnt have been a given). So, looking at each one, find the part thats important and move to...

JacobHershenhouse3G

Kc and Kp are not interchangeable. Kc is found and can only be used in relation to concentrations and Kp is related to the partial pressures of products and reactants. Hope this helps!

JacobHershenhouse3G

Don't let yourself be confused by similar notation because they mean dramatically different things. p just means -log, so in this case you are taking the negative log of a constant and of a concentration, therefore it is evident that the interpretation of these numbers mean different things. Both va...

JacobHershenhouse3G

Yes! These units are equivalent, no stoichiometry needed! Molarity is more often used because it's quicker to write M compared to writing out mol*L^-1 every time. Hope this helps!

JacobHershenhouse3G

Simply use the equation %deprot= [H3O+]/initial[reacting acid] or %prot [OH-]/initial[reacting base]. The 5 % rule is a check on if the change (-x) to the initial concentration of the given acid or base is significant or negligible (if negligible, then the simplification of our k equation is alright...

JacobHershenhouse3G

Right, so in this problem, you have to work at it from both ends. First, you must write out the full acidic reaction of having HClO2 in water (HClO2 + H2O == ClO2- + H3O+). From here, you can use given variables to find the equilibrium concentrations of the products from the pH (10^-pH=[H30+]=[ClO2-...

JacobHershenhouse3G

You must use the context of the problem (your knowns) to determine if the k or kc value is applicable in your problem solving process. K is related to the pressure of a certain gas (bar, torr, pascal, atm etc.), while kc is used when concentrations are given for a gas or aqueous solution (M, mol/L, ...

JacobHershenhouse3G

Depending on how small the following ka's are, you may be able to approximate by only solving the equilibrium concentrations of the first ka, but only if the ka's are very small and you know the difference in equilibrium concentrations will be negligible. Otherwise, if you are told to go through the...

JacobHershenhouse3G

Remember that Q is the constant at any given point in time and has applications that dont involve the changing of equilibrium concentrations. The important thing to note is that BOTH K and Q change when you alter volume or temperature (to reflect the change in equilibrium concentration values). So, ...

JacobHershenhouse3G

Think back to the ideal gas law PV=nRT. Pressure and volume are directly related Using what we know about exothermic and endothermic reactions, we can determine if the reaction shifts left or right but whats of superlative importance is that you know that temperature DOES change equilibrium. Think r...

JacobHershenhouse3G

Be careful here! You are using concentration values, not molar values when you are plugging values into the ICE table as you solve for x. This is because the end goal is the equilibrium concentrations of reactants and products, not the number of moles. Yet, you have the right idea using the stoichio...

JacobHershenhouse3G

Yes! Kc will change if you alter volume (compression), but be careful because Kc does not change when you change pressure in the case that, instead of changing the volume to affect pressure, you change pressure by adding or removing inert gas from the system ({C=[num of moles]/[Volume]} concentratio...

JacobHershenhouse3G

The reason you put ...-2x, -x, +x, +2x... in the change box of your ice table is because we know that the change in concentration from initial state to final state (equilibrium) is consistent across molecules and proportional to the molar ratio of reactants and products (the coefficients), and we kn...

JacobHershenhouse3G

Yes K and Q have the same formula. More importantly, though, they represent different things that, when compared, yield answers to the direction of the reaction at a certain point in time. K=constant (at equilibrium only), Q=constant (at any point in time throughout the reaction). Each specific valu...

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Re: LYNDON'S PORK RAMEN REVIEW

Re: Reduction/Concentration cells

Re: k & K

Re: Reaction mechanisms

Re: 6th edition 14.35

Re: E° is 0 for Concentration Cells

Re: Max work

Re: Standard cell potential of H

Re: Constants

Re: Cell Potential

Re: K=e^lnK

Re: Entropy at 0 K

Re: Gibbs free energy

Re: Integrals

Re: Work equations

Re: Advice from a Medical Student [ENDORSED]

work done by system or on system

Pressure Units

Re: Hess's Law

Re: kc vs kp

Re: pKa vs. pH

Re: Units for concentration

Re: 5% rule and % ionization

Re: 6th edition, 12.57

Re: Number 93 Ch.11

Re: Polyprotic acids

Re: effect on equilibrium by changing volume

Re: Changing Temperature

Re: ICE Table [ENDORSED]

Re: compression vs pressure

Re: ice table

Re: Q and K [ENDORSED]