CHEMISTRY COMMUNITY

Maggie Eberhardt - 2H

is this going to be important for the final?

Maggie Eberhardt - 2H

what is the Arrhenius equation and what is it used for?

Maggie Eberhardt - 2H

I know that the two equations can de derived from each other, but I was wondering about when each is used as well. I think the differential is simply a mathematically derived version of the rate law, and the integrated one is a mathematically integrated version of the rate law.

Maggie Eberhardt - 2H

I love you

Maggie Eberhardt - 2H

do you think these are examples we should memorize or mores just be familiar with for the exam?

Maggie Eberhardt - 2H

what is a reaction profile exactly?

Maggie Eberhardt - 2H

can someone explain their importance/use?

Maggie Eberhardt - 2H

what do we use the integrated rate law for? and differential?

Maggie Eberhardt - 2H

what does this mean in terms of how we go about solving these type of problems? in simple terms, why do I care if a mechanism is slow or fast at equilibrium or other stages?

Maggie Eberhardt - 2H

does anyone know if catalysis applies to the reverse reaction as well? Like, would a catalyst also affect how quickly products can form back into reactants

Maggie Eberhardt - 2H

can someone explain the justification behind each answer to this question? I don't understand exactly how to differentiate between standard E cell potential and just E cell potential

Maggie Eberhardt - 2H

it is part of a reference electrode known as a calomel electrode (Hg2Cl2). basically, using liquid mercury as an electrode takes advantage of its redox reactions

Maggie Eberhardt - 2H

so in problems like 7A.3, we just take the unique rate and multiply it by the stoichiometric coefficient to determine the rate of each reactant/product right? just clarifying here, since I'm not 100% confident on the concept of unique rates

Maggie Eberhardt - 2H

chemistry
chemistreye
chemistrwhy

Maggie Eberhardt - 2H

sorry to sort of make everyone reiterate, but is there a set of rules we can follow to know exactly what the oxidation number of a molecule is? I hear a lot of different strategies/things to check but no one seems to be certain. Thanks!

Maggie Eberhardt - 2H

I think we're just supposed to infer it

Maggie Eberhardt - 2H

a more negative number indicates a greater number of electrons (higher negativity), however with oxidation/reduction, you have to look at each element in the molecule's oxidation number to figure out if it is being reduced or oxidized because a more negative molecule doesn't necessarily mean its bee...

Maggie Eberhardt - 2H

my TA mentioned that you use the same equation, only a derived version that involves heat capacity. I know that's not very descriptive sorry I don't have my notes on me right now :/

Maggie Eberhardt - 2H

I'm still confused about what the difference is between standard entropy and just finding entropy or change in entropy, can someone explain it?

Maggie Eberhardt - 2H

oxidation is the loss of electrons by a molecule and reduction is the gain of electrons

Maggie Eberhardt - 2H

I think the HCl is being reduced and the Cl2 is being oxidized but I'm really not sure

Maggie Eberhardt - 2H

I think you're supposed to use the integral equation with the change in volume from V2 to V1 and the external pressure as a constant on the outside.

Maggie Eberhardt - 2H

a redox reaction is a combination of a reduction reaction and an oxidation reaction

Maggie Eberhardt - 2H

When calculating Q, do we exclude solids and liquids as when we calculate K? (I'm mostly referring to problem two on the Pizza Rolls review packet)

Maggie Eberhardt - 2H

I would also like to know

Maggie Eberhardt - 2H

for constant pressure, you can use ∆H=q, or ∆U=q+w, or q=nCp*∆T where C is heat capacity with constant volume
for constant volume, you can use q=nCv*∆T, where C is heat capacity with constant volume

don't know if this helped but hopefully you got something!

Maggie Eberhardt - 2H

can someone explain to me how the answer to this problem (0.341 J/Kxs) is positive even though the equation you use to solve it is -(rate of heat generation)/temperature = -100/293???

Maggie Eberhardt - 2H

4A.5 asks: A piston confines 0.200 mol Ne(g) in 1.20 L at 25 8C. Two experiments are performed. (a) The gas is allowed to expand through an additional 1.20 L against a constant pressure of 1.00 atm. (b) The gas is allowed to expand reversibly and isothermally to the same final volume. Which process ...

Maggie Eberhardt - 2H

I mean, any question that asks to calculate the work can technically use the integral work equation since it's where the -pdV comes from, so so far I've found that 4A.3 and 4A.5 help to practice!

Maggie Eberhardt - 2H

ALSO I know that 4.2 is not homework, but I would still like to know

Maggie Eberhardt - 2H

and if not, what are some ways to increase energy in an open system? because I'm lost

Maggie Eberhardt - 2H

4A.2 asks to name three ways you can increase energy in an open system and I know one is to add or remove the amount of substance in the system, but I'm wondering if the other ways to affect a system that he discussed in lecture apply to open systems? Like, could heating or cooling an open system in...

Maggie Eberhardt - 2H

a state function just means that it's the STATE of the sample, whatever it is, that matters

Maggie Eberhardt - 2H

I didnt understand this either but according to google, "A bomb calorimeter is a type of constant-volume calorimeter used in measuring the heat of combustion of a particular reaction. Bomb calorimeters have to withstand the large pressure within the calorimeter as the reaction is being measured...

Maggie Eberhardt - 2H

so just to clarify, the environment that the reaction is occurring in stays the same temperature despite the sample changing phases?

Maggie Eberhardt - 2H

which method is the most accurate?

Maggie Eberhardt - 2H

I have also been wondering about this same thing, but the best answer I can think of through reasoning is that it's accurate because it's being used as a standard so if one uses the standard reactions it will give a sturdy answer since they are all on the same page

Maggie Eberhardt - 2H

that symbol indicates the "difference between"

Maggie Eberhardt - 2H

I think gases have more energy because the molecules move faster and do not have a defined space they take up

Maggie Eberhardt - 2H

I have another similar question with 5J.3 - can someone explain why adding/removing a certain amount of a compound might affect its equilbrium?

Maggie Eberhardt - 2H

In 5J.1, it asks "Consider the equilibrium CO(g) 1 H2O(g) ∆CO2(g) 1 H2(g). (a) If the partial pressure of CO2 is increased, what happens to the partial pressure of H2? (b) If the partial pressure of CO is decreased, what happens to the partial pressure of CO2? (c) If the concentration of CO is ...

Maggie Eberhardt - 2H

Sorry if this is a stupid question, but when/why do we use ICE table?

Maggie Eberhardt - 2H

I was just wondering when we apply Le Chatelier's Principle ?

Maggie Eberhardt - 2H

Can someone explain to me what exactly the equilibrium quotient means and how to calculate it? thanks!

Maggie Eberhardt - 2H

Name the ligands and then the central metal cation in one word. The ligands should be in alphabetical order, ignoring the prefixes, and the central metal cation should be last with its oxidation state. If there is a cation in front of the brackets that bonds to the coordination compound, name the e...

Maggie Eberhardt - 2H

I'm not sure, but it might be due to the slight negative charge that C would have in the CH3 molecule, causing H to be attracted more to that central atom and H+ being alone only wants electrons so it has greater withdrawing power

Maggie Eberhardt - 2H

I think it's because the cations want to accept electron pairs in order to eventually a achieve a charge of 0 which would make it most stable. An electron accepting molecule is the definition of a Lewis acid

Maggie Eberhardt - 2H

A higher electronegativity allows for delocalizing of charge of lone pairs, so it makes the molecule generally more stable.

Maggie Eberhardt - 2H

You can find many lists online, and there are also quizlets of them. But I think the main ones we need to know are listed below:
Acids: H2SO4,HBr,HCl,HNO3,HI,HClO3,HClO4
Bases: groups 1 and 2 oxides and group 2 hydroxides

Maggie Eberhardt - 2H

If you want to calculate the dissociation constants of the acids/bases then I guess you wouldn't have to memorize which are the strong ones, but considering there are only about six strong acids and the bases follow the trend of groups 1 and 2 on the periodic table, memorization might make your life...

Maggie Eberhardt - 2H

Yes!
Pi bonds must exist between overlapping p-orbitals

Maggie Eberhardt - 2H

Does anyone have any tips/tricks for memorizing how to name coordination compounds? Or could someone quickly summarize all the rules and aspects we have to note when naming?

Maggie Eberhardt - 2H

H.13, Focus 3 3.69, Example 5G.2, Box 6E.1, all mention acid rain/have practice problems for acid rain

Maggie Eberhardt - 2H

I don't have a mnemonic for memorizing them but the table from Lavelle's course website is really nice to study with/make flashcards from! There's also a few quizlets that have good games/quizzes to help you memorize them faster

Maggie Eberhardt - 2H

I've been wondering the same thing and I'd say it's safe to know the formula for different molecules based on the name since nomenclature was a section covered early on in the textbook for fundamentals, however, on past exams the formulas have been given

Maggie Eberhardt - 2H

The H is attached to one of the O atoms instead of Cl because it forms the hydroxide group at the end of the molecule which creates the most stable structure.

Maggie Eberhardt - 2H

usually, lone pairs will create some sort of dipole moment because lone pairs cause greater electron repulsion, resulting in uneven charges in the molecule. But if you're unsure, I'd draw the Lewis Structure to see exactly how the lone pairs line up

Maggie Eberhardt - 2H

I'm not sure exactly what you mean by "main examples" but the Marshmallow review sheet that was posted by some UAs has a lot of practice problems for most of the topics that are supposed to be covered on the final.

Maggie Eberhardt - 2H

I think it depends on the order of the atoms, as it does with the anions. For example, CN- is cyano but NC- is isocyano.

Maggie Eberhardt - 2H

I don't believe there is a limit, per se, but I don't think we'll be dealing with any molecules/compounds with an expanded octet that has more than like 12 valence electrons

Maggie Eberhardt - 2H

The numerical value comes from the concentration of those values. So it's the concentration of the products divided by the concentration of the reactants. Those values can be calculated depending on what you are given in the specific problem.

Maggie Eberhardt - 2H

Basically, the easier the acid/base dissociates, or ionizes, the stronger it is. One way to find this is to calculate the dissocation constant.

Maggie Eberhardt - 2H

I believe it only occurs in order to make the overall charge of the molecule neutral and not with every hydrated transition metal cation

Maggie Eberhardt - 2H

Do you mean a polydentate?

Maggie Eberhardt - 2H

The -ate is because it is an anion

Maggie Eberhardt - 2H

I'm not positive but in short, yes.The delocalized electron means the bond length is unaffected.

Maggie Eberhardt - 2H

I was also wondering this because I know sometimes they will point away from each other and it's nonpolar, but in other molecules it will be polar. I think if a molecule has dipole moments that aren't all pointing the same way, they do not cancel. But, if they all point the same way, they cancel.

Maggie Eberhardt - 2H

Are hydrogen bonds the strongest IMF? I'm pretty sure they are but I don't 100% understand why?

Maggie Eberhardt - 2H

Matt F wrote:Is this the same for melting points? So stronger IMF's also lead to higher melting points?

yes I believe IMF's also lead to higher melting points

Maggie Eberhardt - 2H

Lone pair-lone pair repulsion is the strongest kind of repulsion and I think what you're referring to as just lone pair repulsion is actually lone pair-atom repulsion which is the second strongest repulsion.

Maggie Eberhardt - 2H

How come CO2 is non polar and the dipole moments point away from each other but CH2Cl2 is polar and the dipole moments point away from each other too? Do all dipole moments have to be facing the same way in order for dipole moments to cancel completely?

Maggie Eberhardt - 2H

So just to clarify, we only have to find the formal charge when it asks us to? Or should we always draw lewis structures using formal charge?

Maggie Eberhardt - 2H

To decide whether a bond is ionic or covalent, you look at the difference in electronegativity. If the difference is greater than 2 the bond is covalent and if its 1.5 or less its ionic.

Maggie Eberhardt - 2H

I was confused as to whether we have to know this for the midterm or not? He said we cover acids and bases later on in the quarter but we still did this in lecture last week so is this on the midterm?

Maggie Eberhardt - 2H

I know he covered this in lecture but I found it a bit confusing. What happens when the difference is between 1.5 and 2?

Maggie Eberhardt - 2H

What is polarizability and how do we find it?

Maggie Eberhardt - 2H

The question asks to draw the Lewis Structure of ICl5. I'm not sure if I'm supposed to put five Chlorines around the Iodine or if two of the Chlorines are bonded. Please help!

Maggie Eberhardt - 2H

He does not post slides :(

Maggie Eberhardt - 2H

I'm pretty sure you only have to draw the resonance structures when it asks you to

Maggie Eberhardt - 2H

I'm wondering what the difference is between ionic and atomic radii. Do only ions have ionic radii? Or do all atoms have it? When I'm finding either, it seems like I'm just looking for how many electrons an element or ion has, because that would determine the size of the radius of the atom. Is that ...

Maggie Eberhardt - 2H

I believe that whole period carries the exception for electron configurations, but I'm not 100% sure.

Maggie Eberhardt - 2H

if that is what your TA assigned. I was told that both Quantum World and Chemical Bonds problems were okay.

Maggie Eberhardt - 2H

I'm not too confident on this topic either, but I'm pretty sure you remove or add an electron to the highest energy level depending on whether you want a cation or anion. For example, to change Zinc from its ground-state to Zn+, you take the ground state configuration [Ar]3d^104s^2 and remove an ele...

Maggie Eberhardt - 2H

Principal quantum numbers is the n values or shell, which determines energy and size. The angular momentum refers to the l values or shape. For example, the s-orbital is l=0, p-orbital is l=1, d-orbital l=2, and f-orbital l=3.
Hopefully this helps get the problem started!

Maggie Eberhardt - 2H

thanks!!

Maggie Eberhardt - 2H

2A.13 For each of the following ground-state atoms, predict the type of orbital (1s, 2p, 3d, 4f, etc.) from which an electron will need to be removed to form the 11 ions: (a) Zn; (b) Cl; (c) Al; (d) Cu. I believe the answer for Cl is that electron is removed from the 3p orbital so it becomes [Ne]3s2...

Maggie Eberhardt - 2H

2A.3 Give the ground-state electron configuration expected for each of the following ions: (a) S2-; (b) As3+; (c) Ru3+; (d) Ge2+.

On the syllabus it says to skip c, but can anyone tell me how to do it?

Maggie Eberhardt - 2H

Can someone help me with these configurations? I get confused about ground vs excited states in electrons.

1E.11 Write the ground-state electron configuration for each of the following atoms: (a) sodium; (b) silicon; (c) chlorine; (d) rubidium.

Thanks!

Maggie Eberhardt - 2H

Which elements are considered exceptions/how do we know if an element is an exception?

Maggie Eberhardt - 2H

How do we know if an electron is in a ground state or an excited state? I'm still a bit confused on this topic

Maggie Eberhardt - 2H

So I understand that l values are based on n and ml values are based on l values, but my question is, how do we know which value of l that ml equals? For example, if l is 3, the allowed values for ml are -3, -2, -1, 0, 1, 2, 3. But how do we know which of those values actually IS the orientation of ...

Maggie Eberhardt - 2H

What exactly is quantum mechanics? I don't understand what it applies to

Maggie Eberhardt - 2H

Light has no mass. Since photons have momentum, p, the equation can be applied to photons, but DeBroglie's is meant for electrons or specifically particles that have rest mass.

Maggie Eberhardt - 2H

As stated in the previous replies, the DeBroglie equation can only be used for objects that have rest mass, which does not apply to light. The equations λν = c or the E = hν are applicable to light. Is light the only thing without rest mass? And I'm also confused as to how rest mass apply to electr...

Maggie Eberhardt - 2H

I was wondering if anyone could help me solve this one, I honestly have no idea where to start. (Just to repeat it) M.7 Solid boron can be extracted from solid boron oxide by reaction with magnesium metal at a high temperature. A second product is solid magnesium oxide. (a) Write a balanced equation...

Maggie Eberhardt - 2H

Hey Yuchien, I solved this problem using dimensional analysis. First, I found the amount of moles of CuSO4 in 250 mL of a 0.20 solution, which is 0.05 moles of CuSO4. Then, we have to convert that into moles CuSO4.5H20 with a conversion factor of 1 mole CuSO4 for every 1 mol of CuSO4.5H20, which al...

Maggie Eberhardt - 2H

The formula of Magnesium Sulfate Heptahydrate is MgSO 4 \cdot 7H 2 0 (Magnesium ion has a +2 charge, Sulfate has a -2 charge and heptahydrate is 7H 2 O since the prefix hepta indicates 7) a) We first start by finding the formula mass of the magnesium sulfate heptahydrate which is 246.48 g/mol To fi...

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