## Search found 69 matches

Sun Jan 24, 2021 8:39 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling Week 2 #7
Replies: 8
Views: 41

### Re: Sapling Week 2 #7

I also faced some difficulties while answering this question. What should we consider as included in the solution in NaClO? I'm confused by the wording of this question.
Sun Jan 24, 2021 8:36 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: X Approximations
Replies: 23
Views: 66

### Re: X Approximations

if you don't want to do the 5% test, you can check if Ka or Kb given is less than 10-4. usually we can use approximations if they are less than 10-4.
Sun Jan 24, 2021 8:33 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Approximately x
Replies: 18
Views: 43

### Re: Approximately x

After reading this thread I am a little confused. What does it mean to approximate x as 0? Could you do this on any of the homework problems? I solved all of them with the quadratic equation. How would you do it the other way? when you list out the ICE table, you can assume that the reactant change...
Sun Jan 24, 2021 8:29 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling Question 3
Replies: 8
Views: 51

### Re: Sapling Question 3

just to add on to the discussion, when i did my calculations, i remember double checking to see if we can use approximation. but since Ka of this acid is 8.40×10−4, I remember I had to solve the quadratic equation to get the accurate answer. This might be the reason you didn't get the right answer. ...
Sun Jan 24, 2021 8:13 pm
Forum: Ideal Gases
Topic: Q and K relationship
Replies: 22
Views: 93

### Re: Q and K relationship

Hello! to simplify things I usually just remember them as one since basically the calculations are the same. but the only difference to remember is that K is for when the reaction is at equilibrium and Q is anything beside that.
Sun Jan 24, 2021 12:36 am
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8545
Views: 1474662

### Re: Post All Chemistry Jokes Here

saw this on instagram lmao
Sun Jan 17, 2021 1:53 am
Forum: Ideal Gases
Topic: Sampling hw #4
Replies: 15
Views: 140

### Re: Sampling hw #4

just to add on to the discussion, you can refer to the professor's lecture 2 for guidance. he gave a very similar example during class i remember.
Sat Jan 16, 2021 8:25 am
Forum: Ideal Gases
Topic: pure substance
Replies: 4
Views: 40

### pure substance

can anyone recall why isn't gas considered a pure substance but solid and liquid are? I think Dr. lavelle mentioned in lecture but I can't quite recall. Thank you!
Sat Jan 16, 2021 8:21 am
Forum: Ideal Gases
Topic: n/V = concentration
Replies: 19
Views: 75

### Re: n/V = concentration

besides the discussion above, you can also think of it similar to the density formula: density = mass / volume. In this case, mass would be similar to n and concentration would be like density, if that helps understand the equation better.
Sat Jan 16, 2021 8:16 am
Forum: Ideal Gases
Topic: Kc vs Kp
Replies: 109
Views: 940

### Re: Kc vs Kp

just to add on to the discussion above,
it also depends on what is given to you. if the question gave you conditions in barr or atm, then go for Kp. if the question gave you concentration, then go for Kc.
Sun Jan 10, 2021 7:25 pm
Forum: Ideal Gases
Topic: PV=nRT
Replies: 74
Views: 451

### Re: PV=nRT

P = Pressure (in atm)
V = Volume (in L)
n = # of moles
R = gas constant
T = Temperature (in K)

remember to use SI units!
Sun Jan 10, 2021 7:23 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Units
Replies: 27
Views: 105

### Re: Units

i don't think there is a preference as long as your value is correct. but usually we use atm or bars out of convenience.
Sun Jan 10, 2021 7:21 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: How do you write the K for an equation with heterogeneous equilibria?
Replies: 10
Views: 60

### Re: How do you write the K for an equation with heterogeneous equilibria?

you would only need to consider the aq formed components. gases and solids would not be considered!
Sun Jan 10, 2021 7:18 pm
Forum: Ideal Gases
Topic: partial pressures
Replies: 14
Views: 63

### Re: partial pressures

partial pressure is the gas pressure when this gas alone occupies the container at the same temperature. if it helps the total pressure of an ideal gas is the sum of all partial pressure of the gasses included.
Wed Dec 16, 2020 6:02 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: [OH-] and pOH difference
Replies: 9
Views: 56

### Re: [OH-] and pOH difference

[OH-] is the concentration of OH- ions in the solution. pOH represents how alkaline a solution is. Mathematically, we can get pOH by calculating -log [OH-].
Sun Dec 13, 2020 5:32 am
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: bond type for Resonance structure
Replies: 1
Views: 16

### bond type for Resonance structure

I'm confused about how to characterize the bond types and count the # of bonds for a resonance structure. for example, how many pai bonds does the resonance for SO2 have? This resonance contains two possibilities and each has 1 pai bond. how do we characterize the bonds in the resonance as a whole i...
Sun Dec 13, 2020 4:55 am
Forum: Determining Molecular Shape (VSEPR)
Topic: textbook problem 2E 25
Replies: 2
Views: 26

### textbook problem 2E 25

in textbook problem 2E 25, the answer said that SF4 is a non polar molecule. however when I drew out the VSEPR, the molecule has a lone pair on S atom and shouldn't it be polar? thanks!
Sat Dec 12, 2020 11:55 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Seesaw vs. trigonal pyramidal
Replies: 22
Views: 150

### Re: Seesaw vs. trigonal pyramidal

seesaw has 1 lone pair and 4 bonding pairs, that's a total of 5 areas of electron density.
trigonal pyramidal has 1 lone pair and 3 bonding pairs, that's a total of 6 electron density. hope that helps!
Fri Dec 11, 2020 12:32 am
Forum: Biological Examples
Replies: 2
Views: 35

In class, Dr. Lavelle gave an example of cisplatin. I was just wondering why does Guanine replaces the Cl on cisplatin and not the NH3?
Thu Dec 10, 2020 11:23 pm
Forum: Administrative Questions and Class Announcements
Topic: lockdown browser for final
Replies: 1
Views: 18

### lockdown browser for final

quick question, do we need to use respondus lockdown browser for the final? because I didn't see the link where you could check if your respondus is all set up under the FINAL tab on CCLE.
Thu Dec 10, 2020 2:27 am
Forum: Hybridization
Topic: hybridization orbitals
Replies: 1
Views: 16

### hybridization orbitals

Dr. Lavelle in class said whenever we have a hybridized orbital it is always going to be 90 degrees to the unhybridized orbital. I'm confused as to why it that? can someone please explain. thank you!!
Wed Dec 09, 2020 11:53 pm
Forum: Hybridization
Topic: hybridization
Replies: 1
Views: 13

### hybridization

I understand how hybridization works, but I'm confused about what's the driving factor for hybridization to occur. for example, Dr. Lavelle gave an example of CH4 in class and said Carbon atom would be hybridized to sp3. So what's driving this hybridization process? how did the electrons just move t...
Wed Dec 09, 2020 12:56 am
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8545
Views: 1474662

### Re: Post All Chemistry Jokes Here

Looking back at my screenshots from Dr. Lavelle's class, I found THIS!! this must be the cutest H2O I've ever seen lmaooooo!! looks just like Mickey Mouse :))))))
Tue Dec 08, 2020 9:18 am
Forum: Determining Molecular Shape (VSEPR)
Topic: bond angle
Replies: 3
Views: 21

### bond angle

quick question, does it mean that the chemical bonds are more stable if the bond angle is larger?
Sun Dec 06, 2020 10:10 am
Forum: Lewis Acids & Bases
Topic: Lewis Acids & Bases
Replies: 12
Views: 88

### Re: Lewis Acids & Bases

Just to add to the discussion above: I usually think that Lewis acid and base as a bigger, more general group and it includes the traditional acid and base concept we’ve been taught in high school. Some of the compounds might not be traditionally considered as an acid but it may be considered as a L...
Sun Dec 06, 2020 10:07 am
Forum: Polyprotic Acids & Bases
Topic: Strength of Acids
Replies: 3
Views: 118

### Re: Strength of Acids

Just to add on to the discussion above:
I find this on google and I think it explained the concept well: https://www.shmoop.com/study-guides/che ... d-strength
Hope this helps!!!
Sun Dec 06, 2020 10:00 am
Forum: Conjugate Acids & Bases
Topic: Conjugate acids vs conjugate base
Replies: 12
Views: 74

### Re: Conjugate acids vs conjugate base

To find the conjugate base, you remove a proton, which would give you SO4-. To find the conjugate acid, you add a proton, which would give you H2SO4. Hope that helps!
Sun Dec 06, 2020 9:56 am
Forum: Lewis Acids & Bases
Topic: Lewis Acid
Replies: 4
Views: 54

### Re: Lewis Acid

Yes you are definitely right that Lewis acid is an electron acceptor. I think for the second part about proton production, you are right as well. Dr. Lavelle gave an example about HCl in class. He said that HCl only exhibits Lewis acid characteristics in aqueous form. So i guess this also depends on...
Sun Nov 29, 2020 8:52 am
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge and Ions
Replies: 7
Views: 81

### Re: Formal Charge and Ions

if you are talking about a covalent compound, then the last part is correct because it would provide a more stable structure. As for ionic compounds, I don't think the formal charges apply to that, or is it just we haven't covered yet. I think what we discussed in class about formal charge only appl...
Sun Nov 29, 2020 8:50 am
Forum: Electronegativity
Topic: General Explanation
Replies: 9
Views: 98

### Re: General Explanation

from my understanding, yes higher electronegativity generally means the element is more reactive. Take F for example, the element with the highest electronegativity, it has 7 valence electrons and only need 1 more to achieve an Octet, and thus it is very reactive.
Sun Nov 29, 2020 7:47 am
Forum: Resonance Structures
Topic: Valence Electrons [ENDORSED]
Replies: 43
Views: 328

### Re: Valence Electrons[ENDORSED]

excluding the d block, you can just look what column is the element in. elements in the first column has 1 valence electron and etc. for the d block, you can write out its electron configuration and see how many valence electrons it have.
Sun Nov 29, 2020 7:44 am
Forum: Lewis Structures
Topic: Lewis Structure XeF_2
Replies: 4
Views: 294

### Re: Lewis Structure XeF_2

I think you can still draw the structure horizontally it doesn't really matter. as long as you represent the bond angle is roughly 180 degree I think it works either way you draw it.
Sun Nov 29, 2020 7:40 am
Forum: DeBroglie Equation
Topic: Purpose of DeBroglie Equation
Replies: 11
Views: 121

### Re: Purpose of DeBroglie Equation

the equation is meant to describe the wave properties of matter. It is also used to describe the mathematical relationship between the velocity, wavelength and momentum of a particle. this equations applies to both electrons and photons and contributes to the discussion of the dual property of both.
Wed Nov 18, 2020 4:24 am
Forum: Lewis Structures
Replies: 4
Views: 53

for question 2c1 on the textbook. the answer said that only a and b are radicals. but what about c? OH has 7 electrons in total, doesn't that make it a radical, with an unpaired electron on O?
Sun Nov 15, 2020 10:23 pm
Forum: Bond Lengths & Energies
Topic: sapling #4
Replies: 3
Views: 29

### sapling #4

hi! for this question, I understand the part about carbon nitrogen bond, since the bond length is closer in value to the carbon-nitrogen double bond. But for carbon oxygen bond, the value is approximately the average of carbon oxygen double and single bond. So what kind of ample bond character does ...
Sun Nov 15, 2020 10:17 pm
Forum: Resonance Structures
Topic: Resonance
Replies: 11
Views: 98

### Re: Resonance

besides what listed above, it's also favorable to have negative formal charges on more electronegative atoms.
Sat Nov 14, 2020 7:24 pm
Forum: Octet Exceptions
Topic: Expanded Octets
Replies: 5
Views: 33

### Re: Expanded Octets

Just to add on to the discussion above, I think it's atoms in period 3 or higher have d-orbitals in their valence shells, so they can accommodate additional electrons.
Sat Nov 14, 2020 6:27 am
Forum: Octet Exceptions
Topic: How to tell
Replies: 6
Views: 93

### Re: How to tell

Just to add on to the discussion above: I found this on a chem learning website that says there are three general exceptions to the Octet rule: 1. Molecules, such as NO, with an odd number of electrons; 2. Molecules in which one or more atoms possess more than eight electrons, such as SF6; and 3. Mo...
Sat Nov 14, 2020 6:20 am
Forum: Ionic & Covalent Bonds
Topic: London Dispersion Forces
Replies: 11
Views: 77

### Re: London Dispersion Forces

Hi! just to add on to the discussion above. I think what separates LDF from other intermolecular forces is that it exists in all kinds of molecules, no matter what other intermolecular bonds are there. while they are the weakest, some molecules are held together only/mainly by LDF, such as the halog...
Sat Nov 14, 2020 6:15 am
Forum: Resonance Structures
Topic: delocalized electrons
Replies: 4
Views: 40

### delocalized electrons

Hello! I've been a little troubled by the term "delocalized" when describing electrons in resonance structures. I understand how resonance structures are formed, but I don't see in what sense are these electrons delocalized? can someone please explain! thank you!
Sun Nov 08, 2020 7:09 pm
Forum: Limiting Reactant Calculations
Topic: Excess reactant affecting limiting reactant
Replies: 7
Views: 78

### Re: Excess reactant affecting limiting reactant

Just to add on to the discussion above, I think there always is a limiting reactant. so if O2 is the excess reactant, you'll have to calculate which is the limiting reactant since it's not always the case where you only have two reactants. But I agree that there is always a limiting reactant in ques...
Sun Nov 08, 2020 8:29 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: The word "energy" used in different scenarios
Replies: 3
Views: 42

### Re: The word "energy" used in different scenarios

yeah I agree that it should be referring to electrons, especially in this scenario you are describing. And from what we've learned in class, I think most of the times when we say "energy" we would be referring to electrons, since they are the ones moving around and generally exhibiting ene...
Sun Nov 08, 2020 8:24 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: delta V. in. Heisenberg questions
Replies: 6
Views: 129

### Re: delta V. in. Heisenberg questions

yeah it's 10 not 5. I googled this question and found a 2017 post on chemistry community where Chem_Adm confirmed this. There's also a section on Dr.Lavelle's website that includes all the textbook corrections. You can also refer to that! Hope this helps!
Sun Nov 08, 2020 8:08 am
Forum: Einstein Equation
Topic: E=pc vs E=hv
Replies: 15
Views: 160

### Re: E=pc vs E=hv

I think both can be used to calculate the energy of an electron, it just depends on the information you're giving in the question. From my experience, I think the equation we need to be careful with is E=mc squared.
Sun Nov 08, 2020 8:03 am
Forum: Properties of Electrons
Topic: Electron Spin
Replies: 7
Views: 65

### Re: Electron Spin

we usually consider the first electron to spin up (+1/2) and the second electron to spin down (-1/2). but I think Dr. Lavelle mentioned in class that these are just math models that scientists employed to represent the opposite spin of electrons in the same sub shell and they don't really exist.
Thu Nov 05, 2020 5:40 pm
Forum: Administrative Questions and Class Announcements
Topic: Fall 2020 Midterm 1 Instructions
Replies: 20
Views: 1084

### Re: Fall 2020 Midterm 1 Instructions

Is there a way to see what question we missed on midterm 1? Thank you!
Mon Nov 02, 2020 5:08 am
Forum: Quantum Numbers and The H-Atom
Topic: quantum number-s- vs p- orbitals
Replies: 3
Views: 44

### quantum number-s- vs p- orbitals

I know Dr.Lavelle went through this in lectures, but I don't think I really understand it: so for electrons in the same shell, why does s- electrons have a lower energy than p-electrons in the same shell? if the outer electrons feel a reduced electrostatic attraction, then why is the order of energy...
Sun Nov 01, 2020 6:07 pm
Forum: Properties of Electrons
Replies: 4
Views: 39

Hi guys, I have a question regarding diffraction. I understand that as Dr. Lavelle puts it, if light acts as particles, there would be two patterns shown at the spot of the openings, but instead we get this diffraction pattern. I just don't understand why this diffraction pattern shown in the diagra...
Sun Nov 01, 2020 5:58 pm
Forum: DeBroglie Equation
Topic: Diffraction Pattern
Replies: 9
Views: 105

### Re: Diffraction Pattern

just to add on to the discussion above, I find the textbook's summary of this very helpful: the textbook mentioned the wave-particle duality of electromagnetic radiation, and said the photoelectric effect means that electromagnetic radiation has particle like properties, and that diffraction means e...
Sun Nov 01, 2020 5:50 pm
Forum: DeBroglie Equation
Topic: Finding the mass of a molecule
Replies: 6
Views: 85

### Re: Finding the mass of a molecule

by diatomic structure, this question is referring to H2. so in order to find the mass of one H2 molecule, you just take the molar mass of H2, which is 2.014, and divide that by Na (Avagadro's constant), because this constant is referring to the number of molecules in one mole of substance. divide th...
Wed Oct 28, 2020 8:11 am
Forum: Empirical & Molecular Formulas
Topic: textbook F13
Replies: 2
Views: 27

### textbook F13

In an experiment, 4.14 g of phosphorus combined with chlorine to produce 27.8 g of a white solid compound. (a) What is the empirical formula of the compound? (b) Assuming that the empirical and molecular formulas of the compound are the same, what is its name? I had trouble getting the right answer ...
Wed Oct 28, 2020 1:02 am
Forum: Properties of Electrons
Replies: 7
Views: 5591

Just want to share: for part c, I was really confused whether you could use the 2.50 x 10^6 hz from part b because that was not given in the main question. but it turned out that the problem can't be solved just using what's given in the main question. Also, when I plugged in 9.11 x 10^-31 for mass ...
Wed Oct 28, 2020 12:53 am
Forum: Properties of Electrons
Replies: 7
Views: 5591

In the initial question, wouldn't you need to convert the velocity of the electron 3.6x10^3km.s^-1 into m.s^-1 so it would be 3.6m.s^-1 to be in SI units or am I mistaken? for part a of this question, yes you would need to convert that to SI units, but it's 3.6x10^6 m/s. the value should be getting...
Sat Oct 24, 2020 8:55 pm
Forum: Limiting Reactant Calculations
Topic: Actual yield
Replies: 20
Views: 194

### Re: Actual yield

for most of the questions I've seen, they usually give you the actual yield, mass/molar mass, and some clues to find the actual chemical equations. with these, you could calculate the theoretical yield and there you get your yield percentage.
Sat Oct 24, 2020 8:47 pm
Forum: Limiting Reactant Calculations
Topic: Double Check my Understanding
Replies: 10
Views: 140

### Re: Double Check my Understanding

Hello, I also would like to pose a question in terms of understanding with limiting reactant questions; if we ignore the stoich coefficients, we would be focusing on just the mass, correct? So while the moles of a compound do indicate the amount of an element in terms of mass, we still need to keep...
Sat Oct 24, 2020 8:39 pm
Forum: Balancing Chemical Reactions
Topic: States of matter in chem equations
Replies: 13
Views: 115

### Re: States of matter in chem equations

I think we do need to include the state of matter at the bottom right of each substance. Most of the questions would give you the state of matter, if not I think we can rely on past experience.
Sat Oct 24, 2020 8:35 pm
Forum: Limiting Reactant Calculations
Topic: Theoretical Yield
Replies: 12
Views: 97

### Re: Theoretical Yield

the definition for theoretical yield says "amount", so I think we should automatically assume the answer should be in grams if the question didn't say otherwise. Prof.Lavelle also said in class that the unit should be grams I remember.
Fri Oct 23, 2020 12:18 am
Forum: Properties of Electrons
Topic: question about circular wave model
Replies: 2
Views: 30

### question about circular wave model

attached is a screenshot from lecture 8 when discussing the circular standing wave model. I understand that waves at the same phase could be connected and can become a stable model. But I don't understand how the circular lightwaves are formed here. there was a motion picture showing the circular wa...
Sat Oct 17, 2020 7:20 am
Forum: Electronegativity
Topic: Determining Polarity
Replies: 4
Views: 573

### Re: Determining Polarity

this molecular is nonpolar. because C H I have similar electronegativity and the structure of the molecule is tetrahedral. tetrahedral molecules can "cancel out" the bonds because of it being symmetrical.
Sat Oct 17, 2020 7:16 am
Forum: Electronegativity
Topic: Hydrogen
Replies: 6
Views: 173

### Re: Hydrogen

I think it's because H only has 2 protons. and also, Hydrogen is not a very typical atom. although it's placed in the upper right corner on the periodic table, it doesn't follow some of the trends that apply to most other atoms.
Sat Oct 17, 2020 7:13 am
Forum: Electronegativity
Topic: periodic table
Replies: 16
Views: 128

### periodic table

can someone summarize the major trends that can be found in the periodic table? Thank you!
Sat Oct 17, 2020 7:05 am
Forum: Resonance Structures
Topic: Resonance
Replies: 2
Views: 320

### Re: Resonance

to check whether a molecule has a resonance or not, draw the lewis structure and see if you can find multiple possibilities that satisfy the requirement. N2H2 doesn't have a resonance structure because there's only one way to meet all the requirements.
Sat Oct 17, 2020 7:02 am
Forum: Ionic & Covalent Bonds
Topic: Boiling point
Replies: 4
Views: 175

### Re: Boiling point

NH3 can be considered as a special case because it has hydrogen bond which is relatively strong. NH3 and PH3 have similar molar mass.
Sat Oct 17, 2020 6:50 am
Forum: Ionic & Covalent Bonds
Topic: Carbon
Replies: 4
Views: 212

### Re: Carbon

I think the most bonds two C atoms can form is 3. they can't form 4 bonds because of bond angle and organizations I think
Thu Oct 08, 2020 10:12 am
Forum: Ionic & Covalent Bonds
Topic: Is ionic or covalent stronger?
Replies: 31
Views: 394

### Re: Is ionic or covalent stronger?

throughout ap chem I was taught ionic bonds are stronger than covalent bond in most cases. In response to the previous comment about nacl in aq form, when dissolved, the ionic bonds in nacl were broken, so I don't think it's comparable in that way.
Thu Oct 08, 2020 10:07 am
Forum: Ionic & Covalent Bonds
Topic: Bond Forming
Replies: 8
Views: 211

### Re: Bond Forming

things tend to get stabilized when they reach equilibrium; to break this requires energy. when enough energy is given to cross the activation energy barrier, then a binding would happen
Thu Oct 08, 2020 10:04 am
Forum: Ionic & Covalent Bonds
Topic: Hydrogen bonds
Replies: 4
Views: 138

### Re: Hydrogen bonds

it would count as a Hydrogen bond if H is bonded to either one of NOF
Thu Oct 08, 2020 10:00 am
Forum: Ionic & Covalent Bonds
Topic: Ionic bonds in solutions
Replies: 9
Views: 191

### Re: Ionic bonds in solutions

ionic bonds are broken. but dissolution is a physical process because ionic bond is a type of intermolecular bond. no intramolecular bond is broken here and there are no new compounds generated.
Thu Oct 08, 2020 9:50 am
Forum: Ionic & Covalent Bonds
Topic: Physical properties
Replies: 4
Views: 345

### Re: Physical properties

I think compounds bonded together by ionic bonds generally have higher boiling points; and also they can conduct electricity when dissolved in water, but covalent compounds can't.