CHEMISTRY COMMUNITY

Jessica Jones 2B

For the amplitudes it will be based on the activation energy. The slowest step will have the highest activation energy and therefore the highest amplitude. The other steps will be lower and you can not be expected to know which of the remaining ones are higher than the other unless they give us valu...

Jessica Jones 2B

the pre exponential factor is the A, which is the collision frequency. so you would use the equation k= Ae^(-Ea/RT)

Jessica Jones 2B

For this problem do we not have to get the concentrations to have the same units? If not, why?

Jessica Jones 2B

for this equation in terms of temperature you always use Cp or Cv instead of R. All the other ones(Volume and Pressure) are just R.

Jessica Jones 2B

and for the mass of the water it will be 1g based on the fact that density= 1g/ml

Jessica Jones 2B

you'll want to do qice=-qtea so it would be n*deltaHfus + mCdeltaT = -(mCdeltaT) and substitute in variables to solve for unknown

Jessica Jones 2B

deltaG is just the amount of energy available to do work at non standard conditions while deltaG(degree sign) is standard gibbs free energy at 25 degrees and 1 atm.

Jessica Jones 2B

because it is not used up in the reaction. They way I determine which is the catalyst is by seeing if it starts as a reactant in the first step and remains a product in a later step.
Intermediates will usually be formed as a product and then canceled out as a reactant.

Jessica Jones 2B

the first law of thermo is that the internal energy of an isolated system remains constant. From this concept, we get deltaH= q + w. The reason why qsys + qsurr= 0 is because when energy leaves a system, the surroundings gain energy(as energy is never created nor destroyed) and so from this can use ...

Jessica Jones 2B

the one with the highest molarity is always the cathode!
so from this figure out half rxns from the tables and fill it in from there!

Jessica Jones 2B

you would solve for concentration (M= moles/Volume) so do ((grams/g/mol))/Liters). In the problem it should say what order which will decide if you square it or just use that. If it is first order R= k[conc] and second order would be k[con]^2 and then you substitute in values and solve for k.

Jessica Jones 2B

You should be able to use either. As long as you identify the anode and cathode correctly

Jessica Jones 2B

This would depends on the units you are trying to cancel. If pressure were in atm you would use .0826 so that the units would cancel

Jessica Jones 2B

You would use the (deltaH of bonds broken - deltaH of bonds formed). In order to figure out which bonds are broken and formed you look at the lewis structures. You could just break every bond in reactants and from every bond in the products if that is easier for you.

Jessica Jones 2B

For this problem why can't we just do the normal standard potential? Meaning just deltaH=Hproducts- Reactants ?

Jessica Jones 2B

When drawing the reaction profiles how do we know what step would have a higher activation energy(and therefore a larger amplitude) just based on the elementary steps?

Jessica Jones 2B

fyi this will not be on the final! only pre-equilibrium approach

Jessica Jones 2B

Q is the concentrations when they are not at equilibrium, so you would set it up the same as the equilibrium constant.

Jessica Jones 2B

No! we will only use pre equilibrium approach

Jessica Jones 2B

Yes it would change if you were considering reactants(forward reaction) and then looking at products(reverse reaction). Your rate law would include the elements in either the reactants or products depending on if it is forward or reverse reaction.

Jessica Jones 2B

Yes I thought that was true as well but for problem 5.71, it asks you to figure out which molecule is the catalyst from the equations? How do I do this?

Jessica Jones 2B

How are you able to determine which molecule is the catalyst?

Jessica Jones 2B

For this question where did the minus .59 in the solutions manual come from?

Jessica Jones 2B

For this problem I am confused why they have 1030K-1000K because the equation is (1/T1)-(1/T2) and this is the opposite of what they did?

Jessica Jones 2B

Advice: Never trust an atom, they make up everything.

Jessica Jones 2B

I told a chemistry joke once, but there was no reaction...

Jessica Jones 2B

Na: "That was sodium funny!"
Ne: "I slapped my neon that one!"

Jessica Jones 2B

Just kidding!! It's an equation :)

Jessica Jones 2B

For this problem, I am having trouble understanding where the 0.693 came from in the first step of solutions manual?

Jessica Jones 2B

For this question I understand that you use Appendix 2b cell values to rank them but I'm confused about how you pick which reaction to use. For example, Fe3+---> ... Fe2+--->... etc. These all have different values and change the order of the strongest reducing agent based on which one you choose.

Jessica Jones 2B

Could someone please explain where the KOH came from in the galvanic cell?

Jessica Jones 2B

I was wondering why sometimes they use ...||Fe3+,Fe| and sometimes they don't use a comma. for example, ...||Au+|Au
In which situations do you use a comma or a line?

Jessica Jones 2B

Will we need to recognize when to put these metals on the ends/ does it matter which metals we pick? Most often seems like Pt

Jessica Jones 2B

When doing a galvanic cell, how do you know which direction to put the oxidizing and reducing agents? Meaning if the reducing agent was Fe3+ to Fe. Would we write Fe3+|Fe or Fe|Fe3+ ?

Jessica Jones 2B

I was under the impression that for a monoatomic gas, C= 3/2 * R, for a diatomic gas, C= 5/2 * R, and for a polyatomic gas, C= 7/2 * R, but in the solution manual polyatomic is 3* R. Could someone explain this?

Jessica Jones 2B

I understand how to calculate and use the equations to find deltaG, but could someone please explain what Gibbs Free Energy means conceptually?
Thank you so much!!

Jessica Jones 2B

Yes w=-pdeltaV is for irreversible work and w=-nRTln(v2/v1) is used for isothermal, reversible expansion.
You would most likely use deltaU= w + q to calculate internal energy and would therefore need to solve for w and for q.

Jessica Jones 2B

for reversible reactions, does deltaStot(or universe) always equal 0?

Jessica Jones 2B

This is because a negative G, corresponds to the reaction being spontaneous, and therefore favorable.

Jessica Jones 2B

Hi! In the solutions manual I have seen them go back and forth between using deltaS=nCpln(t2/t1) and deltaS=nRln(t2/t1). I am confused on if we are supposed to be using Cp or R? or base it on the problem. Do you only use Cp when doing the (3/2*R) or (5/2*R)?

Jessica Jones 2B

there is an error in the solutions manual! check lavelle's list on his website

Jessica Jones 2B

I have similar question because you use the equation deltaS= Cp(ln(T2/T1), but I am confused as to if we are supposed to include the moles/grams in the equation or ignore them all together?

Jessica Jones 2B

When finding the deltaS for a freezing reaction, would you use -deltaHfusion instead of +deltaHfusion?

Jessica Jones 2B

To do this problem, you have to manipulate the coefficients to be able to cancel out and result in the end equation they want. Also keep in mind that when you multiply the equation by a number you also multiply the deltaH value by the same number. Also when you switch the products to reactants, vice...

Jessica Jones 2B

We do this because you need to account for the phase change as a separate entity and then you also do the q= mCdeltaT for the temperature change and add these energies together. It requires much more energy to create a phase change then just to simply raise the temperature.

Jessica Jones 2B

You will need to account for the phase change from ice to water, deltaHfusion.
So your q-ice would include both the mCdeltaT and deltaHfusion.

Jessica Jones 2B

I am very confused as to why the solutions manual has it as -15kJ + 22 kJ when I would expect it to be -15kJ - 22 kJ?
wouldn't it be (delta U)= (delta H)-(P delta V)?

Jessica Jones 2B

Do we use different equations for constant pressure and constant volume?

Jessica Jones 2B

enthalpy is the amount of heat released or absorbed at a constant pressure. Heat is a form of energy

Jessica Jones 2B

yes it would be endothermic!

Jessica Jones 2B

Here is helpful link:
https://www.chemguide.co.uk/physical/eq ... elier.html

Jessica Jones 2B

The concentration changing will not change the equilibrium constant because this is a constant. This means that when you increase a certain concentration, the entire reaction will shift to go back to equilibrium. For example A + B = C. If you increase A, B will decrease in order to regain the equili...

Jessica Jones 2B

First you will create the first reaction which is Na2O + H2O ----> 2NaOH, Then you go through the second reaction which is NaOH ----> NA+ + OH-. Based on this reaction you can find the concentration of [OH-] because the pH is 13.25 making pOH 0.75 and the concentration is 10^-.75, which gives you .1...

Jessica Jones 2B

There are several exceptions around the metalloids that are also considered amphoteric. These are on page 469 and include Be, Al, Ga, In, Sn, Pb, Bi.

Jessica Jones 2B

You should know the strong acids: HCl, HBr, HI, HNO3, HCl3, HCl4, and H2SO4 and the strong bases: NaOH, KOH, RbOH, CsOH, Ca(OH)2, Sr(OH)2, Ba(OH)2
Everything else you should recognize as a weak acid or base.

Jessica Jones 2B

Oxidation involves losing e-. This means that when you lose e- you will have a more positive charge, resulting in a greater desire to attract electrons. Because lewis acids accept electrons, this means that the more oxidized, the more acidic it will be.

Jessica Jones 2B

I understand the ways to determine acid strength (size of atoms,number of oxygens, electronegativity) but how do you determine the strength of a base?

Jessica Jones 2B

Metals in water form basic oxides
Nonmetals in water form acidic oxides
Metalloids + a few extra ones are amphoteric
Check out page 469 for these exceptions!

Jessica Jones 2B

you would also use bis- tris- tetras-, etc if the compound is a polydentate. So you use these prefixes 1. if the name already includes a di, try, etc or 2. if it is a polydentate.

Jessica Jones 2B

When solving the ICE box, if you get a equation with x^3 when setting it up equal to Kc, are we expected to be able to solve for x without at calculator?

Jessica Jones 2B

Fyi 29 was not an assigned problem!

Jessica Jones 2B

500.K is referring to the temperature. 500 Kelvin

Jessica Jones 2B

In chapter 17 question 35, why is it trident ate instead of bidentate?

Jessica Jones 2B

When the overall compound is negative, you add an -ate suffix to the central transition metal when naming it.
example [Cr(NH3)2] is just diamminecromium but [Co(NH3)2]^-1 is diamminecromate

Jessica Jones 2B

When writing the names, do we use the old name or the new IUPAC name convention?

Jessica Jones 2B

Another factor is if there is a single bond and a double bond, the length of all the bonds is between a single bond and a double bond.

Jessica Jones 2B

All atoms in the 3p and past that like 4p,5p,6p, etc all have access to the d orbitals and can form more bonds than just their expected amount.

Jessica Jones 2B

When n=infinity, E=0, and as the energy levels descend, your energy will always be a more negative number.

Jessica Jones 2B

When using the de broglie for an electron we use the known mass 9.11^-31 kg.
Remember to always use SI units when solving, which are kg.

Jessica Jones 2B

When asked for resonance, do you need every single possibility or just a few options?

Jessica Jones 2B

The 2 come from doubling the uncertainty because it is +/- 1x10^-3. This means that you must add the uncertainty +1.0x10^-3 and -1.0x10^-3(but make this positive for the addition)

Jessica Jones 2B

The +/- is the indeterminacy of the velocity. You add both the +5 and -5(but keep it positive for the addition) together and your indeterminacy of velocity variable is equal to 10 an you would substitute this in for the variable.

Jessica Jones 2B

When l=3, it corresponds to the f-orbital where there are 14 electrons, 7 orbitals.
l=0 s
l=1 p
l=2 d
l=3 f

Jessica Jones 2B

In most problems, it clearly states the order of this change, but if it does not you would use the equation: E= -hR/n^2
Stay away from V= R[1/n1^2 - 1/n2^2] because it will not clearly demonstrate what is truly happening in the problem.

Jessica Jones 2B

Light has both wave properties and particle properties at all times. Certain experiments proved both of these things. For example, in the photoelectric experiment, the light acted as a particle. On the other hand, we know light has wave like properties based on spectroscopy, which was shown in the e...

Jessica Jones 2B

When do we know to us the ryberg constant 2.178 x10^-18 vs 3.29x 10^15. I understand that the first one is R times planck's constant but I don't understand how to choose which to pick?

Jessica Jones 2B

I have a question regarding units. How do kg cancel out when divided by J?

Jessica Jones 2B

This formula ties into the wavelength series, such as Lyman: n=1, Balmer: n=2, and Pashen: n=3. Your n initial and n final will correlate to these series.

Jessica Jones 2B

When finding the molar mass of a molecule after balancing the equation, do you ignore the stoichiometric coefficients? For example, 4NH3 would you multiply by 4 or just find the molar mass of NH3?

Jessica Jones 2B

For F3 are we going to be expected to know the molecular formula for nitric acid or is this a later topic?

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