CHEMISTRY COMMUNITY

CHEM 14B Lover

For #11, I read your explanation but am confused still. dStotal = dSpressurechange + dStemperaturechange For dSpressurechange, we use S=nRln(P1/P2), to see how entropy changes as a result of pressure changing along with something (either V or T). I assumed that V would be changing in this part 1 of ...

CHEM 14B Lover

During the test of an internal combustion engine, 3.00 L of nitrogen gas at 18.5 C was compressed suddenly and irreversibly to 0.500 L by driving in a piston. In the process, the tempeerature of the gas increased to 28.1 C. Assume ideal behavior. What is the change in entropy of the gas? My understa...

CHEM 14B Lover

The textbook version has dS = C ln (T2/T1) without the n. Could someone explain why there's a difference in the 2 formulas?

CHEM 14B Lover

The units for Ea are J/mol or kJ/mol etc. What is the /mol referring to? Is it per mole of product? What if 2 products are made? Does that mean per .5 mole of each product? (and energy per .333 mole if there were 3 products etc.)

CHEM 14B Lover

Will be asked to find pH given Ka and Ka2 of a diprotic acid? How would we set up an ice tablee in that case?

CHEM 14B Lover

Because bronsted acids and bases don't directly affect H+ and OH- concentration, how do they affecrt pH?

CHEM 14B Lover

Why does irreversible free expansion mean delta S = 0?

CHEM 14B Lover

Why does higher pressure mean less entropy? Couldn't there still be an equal volume of gas but at higher pressure?

CHEM 14B Lover

Any combination of units work AS LONG AS they are related by the correct units in gas constant R. Conversely, to use R you either have to convert given values' units so they work for R or convert R into a different form of itself with the right units.

CHEM 14B Lover

Breaking Br2 into 2Br doesn't automatically make the 2Br a gas.

CHEM 14B Lover

Can't there be expansion with constant pressure? Wouldn't that still be work done?

CHEM 14B Lover

This also assumes that the number of water and steam particles are equal. Don't intuit that steam burns less because typically when you put your hadn in 100C water your hand is in contact with a lot more molecules than if you had your hand above the steam from boiling water.

CHEM 14B Lover

Standard conditions temp in kelvin! Because 25 C + 273

CHEM 14B Lover

"The energy lost as work is replaced by heat"; but you say these reactions normally happen in a heat bath? What if there isn't a heat bath? Would it simply not be isothermal reversible?

CHEM 14B Lover

Why does no temperature change = no change in U?

CHEM 14B Lover

I think you can also consider whether or not the molecule is in its most oxidised state. If it is then it's in a lowest energy configuration (I think).

CHEM 14B Lover

I think a lot of questions just require you to think the gas is ideal to apply formulas. IRL lot of energy is lost to heat or sound etc. so even if it's not stated explicitly you basically assume gas is ideal all the time.

CHEM 14B Lover

In lecture, professor said that most elementary reactions are 1, 2, or 3 (but even rarely 3) order because the more orders means the more physical molecules have to bump into each other at the same time with enough energy for the reaction to occur. My question is, in that case, what about 1 M or 1 m...

CHEM 14B Lover

Why is isothermal deltaU = 0? A formula explanation would be nice if there is one!

CHEM 14B Lover

Thank you :)

CHEM 14B Lover

Is the reaction mechanisms individual steps the only elementary steps? What else can elementary reactions be?

CHEM 14B Lover

When is it valid to substitute rate constant k? What formulas relate k to k' for a pseudo rate law?

CHEM 14B Lover

Is n the total number of e- moved after balancing the half reactions?

CHEM 14B Lover

Is the rate law constant's (k) units different when in a pseudo rate equation since there is only one concentration that contributes to its units? (assume other reactants' concentration changes don't affect pseudo rate)

CHEM 14B Lover

What are the units of for pseudo rate law constant (k')?

CHEM 14B Lover

What are the appropriate units when plotting ln[conc] for a first order reaction?

CHEM 14B Lover

Why is the electrolytical cell +/- on the electrodes different? Isn't current going the same way?

CHEM 14B Lover

In HW, 6L 1.9, it says the balance the reaction between potassium permanganate and iron2 chloride. How do we know the change in manganese's oxidation state (from +7 to +2)? Should we just know? +7 is deducible but not +2 (I think).

CHEM 14B Lover

Could someone explain to me in words (to help me conceptualise) what Gibbs Free energy is?

CHEM 14B Lover

If a gas changes volume and temperature during a compression, for the entropy formulas that involve a constant T or V to find deltaS using changes in T or V, how do you know what value to use?

CHEM 14B Lover

For ideal gases, why is Cp 5/2R and Cv 3/2R

CHEM 14B Lover

Are phase changes spontaneous (based on entropy or Gibbs energy)? and how does that fit into the formulas?

CHEM 14B Lover

To clarify, Cp is larger than Cv because Cp = heat supplied to heat the system + work down to expand the gas above. Is this correct? Does this also mean Cv=Cp if the system proceeds in a vacuum?

CHEMISTRY COMMUNITY

Search found 33 matches

Re: Review Session-Thermo-files- Wednesday-Q11-clarification [ENDORSED]

HW 4F.11

dS = nC ln(T2/T1) [ENDORSED]

Activation energy units

Ka and Ka2

pH and pOH

Re: isothermal irreversible free expansion

Re: Entropy change: V, P, T

Re: units

Re: Enthalpy of phase change

Re: ΔH vs ΔU?

Re: steam at 100ºC burn worse

Re: Is there a significance with 298 degrees Kelvin?

Re: Internal energy

Re: Delta U

Re: Determine if molecule is in most stable form

Re: Assuming ideal gas

Molarity and rates

Isothermal

Re: DOWNLOAD SESSION WORKSHEETS HERE - Sun 7-9PM (Karen)

Elementary Step

Converting

Nernst

Rate Constant

Units pseudo rate law

Units for lnconc

Electrolytic cell

Knowing oxidation states

Gibbs

Entropy using statefunctions

Ideal Gas C

Spontaneity

Cv vs Cp