CHEMISTRY COMMUNITY

siannehazel1B

Both open and closed systems can have adiabatic processes since heat is another form of energy (first law) and energy can be exchanged through both kinds of systems.

siannehazel1B

How do we know when to do the difference of sums vs when to use the equation $\Delta G= \Delta H-T\Delta S$ to solve for gibbs free energy?

siannehazel1B

Does the solutions manual use the enthalpy of formation value for Zn²⁺ in replacement for ZnCl because the Cl is just an ion that has a 2- charge? if so, would this also be true when looking for the enthalpy of formation values for all elements attached to an ion?

siannehazel1B

For this problem, why is 2SO₂ the limiting reactant when O₂ takes the same amount of moles while its coefficient is 1? Looking at how the solutions manual determined the limiting reactant for the previous problem, shouldn't O₂ be considered the limiting reactant here?

siannehazel1B

How do we know when we are supposed to write out the equations and use a Hess' law approach to solve for the reaction enthalpy? For this problem, i thought we were supposed to use the difference of sums approach because i didn't initially know how to write the combustion reactions

siannehazel1B

For this problem, how do you know that adding the bond enthalpies of a reaction will give you the change in enthalpy for the production of water in the gas phase? In general, how would you determine what state the element will be formed in?

siannehazel1B

Also, in a first order reaction, the rate of the reaction is doubled while in a second order reaction, the rate of the reaction is quadrupled.

siannehazel1B

The written cell diagram typically mirrors the set up of the battery in that the anode(oxi) is on the left while the cathode(red) is on the right side.

siannehazel1B

The unique rate relates to the production/consumption of one mole of a substance substance (you get this by dividing by its stoichiometric coefficient) while average rate is the overall rate for the whole reaction over a period of time.

siannehazel1B

I understand how to plug all the values into the NERNST equation after I write the half reactions, but I'm confused as to where the solutions manual is getting 0.025693V/n. I thought we were supposed to use either 2.303RT/nF or 0.0592/n?

siannehazel1B

On test 2, will we be given a chart of all the half reactions and their corresponding $E^{\circ}$ values such as the one found in Appendix 2B, or will we have to write our own half reactions and just be given the $E^{\circ}$ ?

siannehazel1B

As i am doing the homework questions (specifically #11-15) I noticed the solutions manual reverses the anode reaction in every problem but only sometimes changes the sign of E^{\circ} . I am confused on why the E^{\circ} sign is not being switched every time the anode reaction is reversed? How do we...

siannehazel1B

In lecture, Dr. Lavelle said we will not explicitly be asked "derive the equation for _____", but for some problems we will need to know the different variations of the original equation in order to solve the problem. So to answer your last question, yes, we have to be able to apply the co...

siannehazel1B

It's safe to just look at what you are given in the question (if enthalpy is in kj/mol in the question then your answer should be in kj/mol, etc.) but you can also assume that you can put just kj for your answer if the question implies that you're only talking about one mole of a substance.

siannehazel1B

a negative q does not necessarily mean that the temperature will decrease as shown by the heat curve: The diagonal lines indicate an increase/decrease in temperature as a result of the change in energy, the flat parts of the graph show that energy is being added/removed however the temperature does ...

siannehazel1B

This formula is useful as it represents what the second law of thermodynamics is, but it is mostly used as the equation from which we derive the other entropy equations we use more frequently for calculations.

siannehazel1B

\Delta G^{\circ} is the change in free energy under standard conditions (25celcius and 1atm) while \Delta G is the change in free energy under varying temp and pressure conditions. If you're calculating \Delta G^{\circ} , your \Delta H^{\circ} and \Delta S^{\circ} also need to be under standard con...

siannehazel1B

I was a little confused in lecture when prof Lavelle said that the maximum work done by a process represents the free energy for that system, can somebody explain this to me conceptually? Also, what does the temp and pressure have to do with this idea?

siannehazel1B

When solving for entropy with changes in volume and temperature, how do we know when we have to multiply R by 3/2 or 5/2 vs when we just use the 8.314 in our equation?

siannehazel1B

When solving for entropy when there is a change in temperature while Volume is constant, does it matter if we calculate the T₂/T₁ in Kelvin or Celcius? If so, which one are we expected to be using?

siannehazel1B

I'm a little confused on why there is a negative relationship between $\Delta H$ and $\Delta S$ ? If $\Delta H= q$ wouldn't that make $\Delta S$ a negative number since $\Delta S= q/T$ ?

siannehazel1B

when you're doing a problem that calls for the change in temperature it doesn't matter what units you use because the difference in temp will be the same no matter what units you're in, but the problem should specify what units if they are needed.

siannehazel1B

how does the equation w=-nRTlnV2/V1 account for the changing pressure and more work being done as opposed to the equation for the irreversible pathway?

siannehazel1B

S = Kb lnW is the standard equation for finding entropy while S = Kb ln2 is simply the standard equation with the degeneracy value plugged in.

siannehazel1B

I had the same question as i was doing the homework questions but i think that is something he will go over in lecture on Friday.

siannehazel1B

You can also change it by adding or removing different amounts of the substances in an open system.

siannehazel1B

Yes, the larger the molecule, the more bonds there are that have to be accounted for when it is being heated.

siannehazel1B

The condensation of the water vapor when it touches your skin releases large amounts of energy(heat) that causes the burns.

siannehazel1B

By definition, an isolated system can't exchange matter or energy with its surroundings and a calorimeter does not allow for this exchange.

siannehazel1B

Will these Cpm and Cvm values always be given for the problem?

CHEMISTRY COMMUNITY

Search found 30 matches

Re: adiabatic process

Calculating Gibbs Free Energy

8.99 [ENDORSED]

8.101 [ENDORSED]

8.57

8.67 [ENDORSED]

Re: Difference between 1st and 2nd order reactions

Re: Cell diagram order

Re: Unique Average Rate vs. Average Rate

14.37

Test 2

Sign of E when anode rxn reverses

Re: Derivations

Re: Units for enthalpy

Re: q and temp increase

Re: formula

Re: Delta G

Gibbs free energy and work

R value in entropy equation [ENDORSED]

Temperature units for Entropy [ENDORSED]

Relationship between Enthalpy and Entropy [ENDORSED]

Re: When to use Kelvin or Celsius

Re: Irreversible vs. Reversible [ENDORSED]

Re: Formula confusion [ENDORSED]

Re: Enthalpy at constant pressure and volume [ENDORSED]

Re: Internal Energy/Open System

Re: 8.29

Re: Boiling water vs. steam

Re: 8.1 part c [ENDORSED]

Re: Problem 8.31