CHEMISTRY COMMUNITY

Chloe Likwong 2K

Strongest reducing power: most negative value Strongest oxidation power: most positive value For C, find the most negative value (reducing power) as your anode because you'll be subtracting it in the formula [E°(cell) = E°(cathode) − E°(anode)] and the most positive value (oxidation power) as your c...

Chloe Likwong 2K

Also, if there is a solid in the reaction, make sure it is conducting (metal). If not, we then add Pt(s).

Chloe Likwong 2K

We add Pt(s) if the reaction has no conducting (metal) solid.

Chloe Likwong 2K

Melting of ice is a spontaneous reaction, it releases heat. Therefore, it has a negative deltaG.
You can also think about it another way. Liquid water has more entropy than solid ice. Thus, it can imply that deltaG is more (-).

Chloe Likwong 2K

My TA said that you don't include water in the cell diagram because with a galvanic cell, it is implied there's already water.

Chloe Likwong 2K

Just remember that:

Strongest reducing power: most negative value
Strongest oxidation power: most positive value

Chloe Likwong 2K

Also, even if the equation gives you a solid, make sure it's a metal. If not, then you have to use Pt(s).

Chloe Likwong 2K

You would want a metal solid to be the electrode. Pt(s) is inert so it's the usual go-to.

Chloe Likwong 2K

Also, remember that the reducing agent is associated with the oxidation reaction.

Chloe Likwong 2K

Also, the cell diagram itself might be given and we're asked to provide the half-reactions, similarly to problem 14.11 in the 6th Ed. So, you should also know how to work backwards regarding cell diagrams.

Chloe Likwong 2K

Also, Lavelle might give us the cell diagram and ask for the half-reactions, similarly to problem 14.11 in the 6th edition.

Chloe Likwong 2K

This conversation thread provides more info:
viewtopic.php?f=127&t=41698

Chloe Likwong 2K

I believe it is because the reaction is explicitly stated to release energy so -q(reaction)=-[-q(calorimeter)].
It would then be -q(reaction)=q(calorimeter).

Chloe Likwong 2K

In the problem, it doesn't matter whether you convert it or not because you're simply finding the difference (whether you add 273 or not, the difference between the two temperatures would still be 80).

Chloe Likwong 2K

It's listed on the formula sheet; just remember to convert the units to joules in the end.

Chloe Likwong 2K

Kobe_Wright wrote:What would cp be in this equation?

If the substance is anything except water, the Cp is usually given in the question.

Chloe Likwong 2K

They'll be given! Here's the list of equations/values:
https://lavelle.chem.ucla.edu/wp-conten ... ations.pdf

Chloe Likwong 2K

If you're decreasing the overall volume, the pressure will increase, shifting the reaction where there's less moles of gas.

Chloe Likwong 2K

I believe the "steepness" can also depend on the intervals of your x and y axis.

Chloe Likwong 2K

Here are the formulas:

"Fixed" or irreversible reactions has a constant external pressure: w=-P*deltaV
Reversible and isothermal reactions that has a changing pressure: w=-nRTln(V2/V1)

Chloe Likwong 2K

Here's the syllabus for the whole list:
https://lavelle.chem.ucla.edu/wp-conten ... 4BSYLL.pdf

Chloe Likwong 2K

You would cancel the reactants and products if they're on opposite sides of the equation. Make sure to remember that it should be in the same state. You might have to multiply or reverse the reaction in order to cancel some reactants/products. If you multiply, you should also do the same to the enth...

Chloe Likwong 2K

Remember to also make sure that the states are the same if you're cancelling.

Chloe Likwong 2K

Also, remember that they have to be the same state.

Chloe Likwong 2K

Apart from other guidelines, a strong base usually has (OH) in the molecular formula, such as LiOH and KOH.

Chloe Likwong 2K

Similar to finding the equilibrium constant, the reaction quotient requires you to use molarity/concentration.

Chloe Likwong 2K

Equation: CO(g) + H2O(g) ⇌ CO2(g) + H2(g) Question: (d) If the concentration of H2O is decreased, what happens to the equilibrium constant for the reaction? Answer: (d) The equilibrium constant for the reaction is unchanged because it is unaffected by any change in concentration. Can someone please ...

Chloe Likwong 2K

Can someone please explain the concepts behind 11.11c and 11.11d? I know that the coefficients are implied in part d, but I'm uncertain about the impact of it being included/omitted in the ratio and how it affects the overall value. Thanks!

Chloe Likwong 2K

If you're pertaining to 11.13a (6th Edition), you use the reactants. The products, since they're solids, are simply 1 in the equation.

Chloe Likwong 2K

The formula is the same. What's different between the two is the concept behind it. The equilibrium constant K is the ratio at equilibrium; it describes a reaction that is at equilibrium. On the other hand, the reaction quotient pertains to the ratio at any given time of the reaction. This might elu...

Chloe Likwong 2K

To sum up the previous comments, the stronger the bond, the higher the boiling point.

Chloe Likwong 2K

Strong bases usually have [OH-] in the compound.

Chloe Likwong 2K

Adding to the previous comment, there are more bonds present, thus, there are more bonds to break.

Chloe Likwong 2K

Strong bases usually have (OH-) in the compound.

Chloe Likwong 2K

H20 is neutral because if you draw its Lewis Structure, you can see that there is no formal charge on either the oxygen or the hydrogen.

Chloe Likwong 2K

Chlorine is named Chloro because it is inside the bracket; it is a ligand.

Chloe Likwong 2K

If you see OH in a compound, H is usually attached to O.

Chloe Likwong 2K

Knowing an atom's electronegativity will tell you the polarity of the molecule/compound (you will need to know the trend for this). There are exceptions though, because if there's symmetry in the molecular shape, the dipoles can "cancel" each other out. For example, for CCl4, Chlorine is m...

Chloe Likwong 2K

You regard the pairs separately. This is used in determining the electron geometry, which then helps you acquire the hybridization of X.

Chloe Likwong 2K

In addition, Fluorine is more electronegative than Iodine; it holds on tightly to its electrons, which makes the bond shorter, and therefore stronger.

Chloe Likwong 2K

Bonds-
Single: 1 sigma, 0 pi
Double: 1 sigma, 1 pi
Triple: 1 sigma, 2 pi

A sigma bond must be present if a pi bond were to exist.

Chloe Likwong 2K

We don't take into account the number of bonds in finding electron density because they're connected to the same atom, thus, they are simply regarded as a single region. Below is a post similar to yours with more explanation: https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=41&t=37332 Hope th...

Chloe Likwong 2K

Sigma bonds: end-to-end overlap and must form before a pi bond Pi bonds: side-by-side overlap and it cannot exist w/o a sigma bond To further clarify: Bonds- Single: 1 sigma, 0 pi Double: 1 sigma, 1 pi Triple: 1 sigma, 2 pi There are comments in this link that provide more clarification: https://lav...

Chloe Likwong 2K

Sigma bonds: end-to-end overlap and must form before a pi bond
Pi bonds: side-by-side overlap and it cannot exist w/o a sigma bond

To further clarify:

Bonds-
Single: 1 sigma, 0 pi
Double: 1 sigma, 1 pi
Triple: 1 sigma, 2 pi

Chloe Likwong 2K

If one looks at its electron geometry, it is considered to be an octahedral because we take into account the lone pairs of the central atom. However, if we look at its molecular shape, it is square planar because we only consider the bonded pairs of the central atom.

I hope this helps!

Chloe Likwong 2K

It is helpful to know about electron geometry since the two comments above are pertaining to that. Electron Geometry: takes into account the lone pairs of the central atom (thus, it is considered to be a tetrahedral) Molecular Shape: considers bonded pairs only of the central atom (thus, its shape i...

Chloe Likwong 2K

amogha_koka3I wrote:So is this an easy way to look at it: electron geometry/arrangement takes into account lone pairs of the central atom whereas molecular shape simply considers the shared bonds?

Yeah, that is the difference between the two.

Chloe Likwong 2K

There is no class on Wednesday.

Chloe Likwong 2K

I just wanted to verify the answer for question 4.1B. Is the reason why a linear molecule "may have lone pairs" is that said molecule can have lone pairs of electrons as long as the ends have the same amount of pairs? Or is it completely dependent on the central atom having a lone pair or ...

Chloe Likwong 2K

Hi!

The preceding comments are helpful, but I believe that looking at a VSEPR chart would solidify what they're saying.

This link may provide you with a better idea: https://goo.gl/images/bkB9yu

Hope this helps!

Chloe Likwong 2K

Trigonal pyramidal is applicable when there's 3 atoms bonded to a central atom that has a lone pair. It is the ideal structure because the angles are <109 degrees.

Chloe Likwong 2K

Wavelength (lambda): nm or m
Frequency (nu): Hz or s^-1.
Speed of light: m/s

Hope it helps!

Chloe Likwong 2K

Also, remember after filling in the electrons in the order of 4s & 3d, you should move 3d before 4s. So, it will be 3d^n, 4s^n in your final electron configuration.

Chloe Likwong 2K

The mass composition has to add up to 100% or else you would not be able to do the problem.

Chloe Likwong 2K

To provide more clarification: Addition/Subtraction : The answer should have the "smallest number of decimal places." For example: 10.2 + 1.005 + 2.35 = 13.555 = 13.6. (10.2 has one decimal present, thus, we "follow" it) 4.505 - 2.3 = 2.205 = 2.2 Multiplication/Division : One pic...

Chloe Likwong 2K

Try to do what Lavelle teaches us. As of now, he used lines to symbolize bonds not lone electrons; dots signify electrons.

Chloe Likwong 2K

I think we just have to know the general idea of what the f-orbital entails, not the specifics of it.

Chloe Likwong 2K

Yes, it is listed in the equations sheet in the front.

The link below lists all of the given:
https://lavelle.chem.ucla.edu/wp-conten ... ations.pdf

As the previous comment stated, you just have to know when to convert that to another unit.

Chloe Likwong 2K

Looking for patterns may be the way to go.

Look at how the numbers varies for n, l, ml, and ms.

Chloe Likwong 2K

My TA said that it is all of chapter 1 and the first part of chapter 2; I don't know where the cutoff is for the latter though.

Chloe Likwong 2K

I just wanted some clarification regarding question 2.37 part a and b because they're related in some way. Why do they mean by "electrons in the lower energy orbitals will 'shield' the electrons in the higher energy orbitals from the nucleus?" Why do electrons in the lower energy levels do...

Chloe Likwong 2K

Just to verify the preceding comment, my TA said that the conversion will be listed on the test.

Chloe Likwong 2K

For (a), one must remember that subshells are the principal and angular momentum quantum numbers. The symbol for the two would be (n) and (l), with l=n-1. a.) cannot exist because if n=2, values of l can be l=1 or l=0. l=1 is the p-orbital and l=0 is the s-orbital; there is no value of l that can be...

Chloe Likwong 2K

Can someone please explain to me the question: "Describe the orientation of the lobes of the px-, py-, and pz-orbitals with respect to the reference Cartesian axes"

I was wondering how one will depict each of the orbitals, such as the orbitals' specific characteristics if they do have one.

Chloe Likwong 2K

In addition, With values that end in zero but has a decimal point after it, you consider those zeros as Significant Figures. For example, 500. and 4350. has 3 and 4 Significant Figures respectively. Hope that helps! If you do have questions regarding subtraction/addition and multiplication/division ...

Chloe Likwong 2K

To provide more clarification: Addition/Subtraction : The answer should have the "smallest number of decimal places." For example: 10.2 + 1.005 + 2.35 = 13.555 = 13.6. (10.2 has one decimal present, thus, we "follow" it) 4.505 - 2.3 = 2.205 = 2.2 *Thus, for answers regarding subt...

Chloe Likwong 2K

To add on the first reply, if the Percent Yield > 100%, the reason would be is that the product is not pure.

Chloe Likwong 2K

To provide more clarification: Addition/Subtraction : The answer should have the "smallest number of decimal places." For example: 10.2 + 1.005 + 2.35 = 13.555 = 13.6. (10.2 has one decimal present, thus, we "follow" it) 4.505 - 2.3 = 2.205 = 2.2 Multiplication/Division : One pic...

Chloe Likwong 2K

Just reaffirming the reply you got, the Solutions Manual goes by 6.022 x 10^23. Ergo, rounding 6.022 to 6.02 will lead to some of your answers to be off, just as you said.

Chloe Likwong 2K

The two precedent posts make sense, however, when one adds or subtracts, the rule for significant figures differs from the multiplication/division. When one is adding or subtracting, they should take the "smallest amount of decimal places in the data" (this can be found in one of the links...

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