Search found 102 matches

Wed Feb 12, 2020 4:48 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Summary of Units
Replies: 3
Views: 28

Re: Summary of Units

Will it matter on the midterm what we leave our answers in, if not specified explicitly in the problem?
Wed Feb 12, 2020 4:36 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: State Functions
Replies: 4
Views: 25

Re: State Functions

The state functions one is PDTV HUGS

I forget what he said but I think its something like when I'm Pressured and Depressed, I like to watch TV and get HUGS

P=pressure
D=Density
T=Temperature
V=Volume
H= Enthalpy
U=internal energy
G=Gibbs free energy
S= Entropy
Wed Feb 12, 2020 4:31 pm
Forum: Phase Changes & Related Calculations
Topic: Delta H Fusion
Replies: 8
Views: 40

Re: Delta H Fusion

It is divided in to multiple steps because delta H Fusion only calculates the phase change value. But the solid first needs to heat up to 0.0 Celsius which is one Delta H value and then you must add the n*DeltaHFusion to calculate the Delta H of the overall rxn.
Wed Feb 12, 2020 4:24 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Entropy of the System for irreversible expansions
Replies: 6
Views: 28

Re: Entropy of the System for irreversible expansions

Also, When is the change in internal energy zero for an irreversible expansion? Internal energy is zero when Temperature is constant because there is no energy transfer if there is no change in temperature ( Internal energy measure the heat transfer) so there is none if temperature isn't changing. ...
Wed Feb 12, 2020 4:17 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Isothermal Reversible
Replies: 6
Views: 24

Re: Isothermal Reversible

Yes, I believe so and that's why it always says isothermal reversible reaction. I don't think you will see it just say reversible without saying isothermal or constant temperature explicitly stated.
Wed Feb 12, 2020 4:14 pm
Forum: Phase Changes & Related Calculations
Topic: internal energy
Replies: 2
Views: 23

Re: internal energy

Constant temperature (isothermal) indicates that delta U is 0. Constant pressure allows you to set q equal to delta H, and the work is -PdeltaV. And internal energy=0 when the process is isothermal because internal energy is heat transfer. So if the temperature is not changing then there will be no...
Wed Feb 12, 2020 3:57 pm
Forum: Administrative Questions and Class Announcements
Replies: 4
Views: 364

Thank you guys so much!!
Wed Feb 12, 2020 3:56 pm
Forum: Ideal Gases
Topic: STP
Replies: 7
Views: 38

Re: STP

STP is 25 degrees Celsius that's why its 298K. At 0 degree celsius its 273.15K because to go from celsius to kelvin you add 273.15
Wed Feb 12, 2020 3:40 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: pizza rolls 5c
Replies: 2
Views: 16

Re: pizza rolls 5c

I believe their explanation was that room temperature= 298K and water vaporizes at 298K therefore you can calculate entropy. I think its similar to the problems we have had where you have to divide entropy up in to steps (since it is a state function) and you can navigate your way to the DeltaSvap o...
Wed Feb 12, 2020 3:35 pm
Forum: Phase Changes & Related Calculations
Topic: rate of reactions
Replies: 3
Views: 27

Re: rate of reactions

I don't think so, but if it comes up, a rate just means it is per some time measurement. Ex. 26kJ per second
Wed Feb 12, 2020 3:34 pm
Forum: Phase Changes & Related Calculations
Topic: Heating curve
Replies: 5
Views: 33

Re: Heating curve

For the sloped lines in a heating curve ( the solid, or liquid is heating up) for the straight horizontal lines the phase change is occurring. When calculating the sloped lines you use q=mCDeltaT but when you are at a phase change ( straight line), you use n*DeltaHfusion
Wed Feb 12, 2020 3:26 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Four Cases
Replies: 2
Views: 41

Re: Four Cases

You probably won't necessarily need to know them by heart but you can logically think about them while solving the problem, ask yourself how can I make the Gibbs free energy negative and therefor more spontaneous. You do this by looking at the equation algebraically.
Wed Feb 12, 2020 3:15 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Mnemonic Devices
Replies: 2
Views: 31

Re: Mnemonic Devices

The state functions one is PDTV HUGS

I forget what he said but I think its something like when I'm Pressured and Depressed, I like to watch TV and get HUGS

P=pressure
D=Density
T=Temperature
V=Volume
H= Enthalpy
U=internal energy
G=Gibbs free energy
S= Entropy
Tue Feb 11, 2020 3:19 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: C in nCv ln (T2/T1)
Replies: 5
Views: 25

Re: C in nCv ln (T2/T1)

C in Cv is heat capacity and will most likely be the heat capacity of a monoatomic gas : Cv= 3/2R
Tue Feb 11, 2020 3:18 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 4.7 Homework Help regarding signs of work
Replies: 1
Views: 22

Re: 4.7 Homework Help regarding signs of work

Hi! This comes from the original equation deltaH= q+w Step1: isolate q So q=DeltaU-w Step2: To get Delta H we are assuming that the reaction is occurring under constant pressure (qp) Therefore DeltaH= DeltaU-w Step3: BUT w=-PexDeltaV so the we have - -Pex which becomes positive to get: DeltaH= Delta...
Tue Feb 11, 2020 3:10 pm
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: higher entropy cis or trans
Replies: 6
Views: 848

Re: higher entropy cis or trans

IMG_0853 2.jpg I drew them out so that it's easier to visualize the 12 cis and the 3 trans in case anyone is also struggling like me; the above comment definitely helped me understand this problem a lot better, thank you so much! I circled the X so that it's easier to see how each molecule differs ...
Tue Feb 11, 2020 3:08 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Replies: 18
Views: 53

Sanjana Borle 2K wrote:Yes, in an adiabatic process q equals to zero because there is no transfer or heat between a system and its surroundings.

^^ this correct and then would imply that deltaU (change in internal energy is = w (work)) since q=0
Mon Feb 03, 2020 4:42 pm
Forum: Calculating Work of Expansion
Topic: units
Replies: 9
Views: 29

Re: units

w as work is presented in Joules or can be kJ if the problem specifies it. W as degeneracy though does not have units because it is just the number of microstates possible.
Mon Feb 03, 2020 4:40 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 4A.13
Replies: 2
Views: 20

Re: 4A.13

So like said above the first part of info (the first q stated) gives us qcal and allows us to solve for the specific heat capacity of the calorimeter. You would do this by using the same equation you stated as q=CdeltaT, but rearrange it as C= cal/delta T. Then you can use this value of C to solve t...
Mon Feb 03, 2020 1:19 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Reversible Reaction
Replies: 2
Views: 15

Re: Reversible Reaction

Can someone please explain what makes a reaction reversible. I am just a little confused about qualifies as a reversible reaction. A reaction is reversible when it is in equilibrium with its surroundings. This occurs when the work is isothermal (at a constant temperature) and the expansion is rever...
Mon Feb 03, 2020 1:08 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Isobaric Reversible Expansion
Replies: 4
Views: 23

Re: Isobaric Reversible Expansion

Are you asking for this equation : -nRTlog (V2/V1) or how he derived this?
Mon Feb 03, 2020 1:05 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Double bonds
Replies: 4
Views: 20

Re: Double bonds

I'm not sure if this is the answer you're looking for, but you can't break one bond of a double bond. You have to break the whole thing and reform it as a single bond. You'll have different bond enthalpies for the same atoms bonded with a single bond versus a double bond. ^^ This is true, so you ha...
Tue Jan 28, 2020 7:04 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: reaction enthalpy
Replies: 14
Views: 41

Re: reaction enthalpy

It is negative, because bonds are being formed and the rxn is exothermic. Forming bonds is more favorable, because it doesn't require an input of energy breaking bonds does. The reaction being endothermic or exothermic in Thermochemistry is based on what is happening to the surroundings. To break b...
Tue Jan 28, 2020 6:59 pm
Forum: Calculating Work of Expansion
Topic: 4A.3
Replies: 7
Views: 49

Re: 4A.3

On part C of this problem, why would the change in internal energy of the system be different then how much work is done in the compression? w= -Pex(deltaV) where Pex= constant external pressure delta V= Vfinal-Vinitial ( the expansion/compressiom of the system) when deltaV is positive , the intern...
Tue Jan 28, 2020 6:52 pm
Forum: Calculating Work of Expansion
Topic: 4A.3
Replies: 7
Views: 49

Re: 4A.3

Sorry this is for 4A.1 but I didn't know where else to ask. How can we tell if a system is open, closed, or isolated? Mainly, what is the difference between closed and isolated? I got those two mixed up Micah- a closed system by definition according to the textbook "has a fixed amount of matte...
Tue Jan 28, 2020 6:47 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Best Method of the 3 Given?
Replies: 7
Views: 25

Re: Best Method of the 3 Given?

Method 2 is the least accurate method but can be used if you are given bond enthalpies. For method 3 everything must be in a standard state and you will receive the standard reaction enthalpy. So I think if it doesn't specify to solve for the standard reaction enthalpy and just asks for the reaction...
Tue Jan 28, 2020 6:41 pm
Forum: Ideal Gases
Topic: Kc vs Kp
Replies: 33
Views: 120

Re: Kc vs Kp

when a chemical equation is written and all the reactants and products are gases, do you use Kp rather than Kc? in what cases do you use Kc rather than Kp? Kc should be used normally, but the question will clarify if it wants molar concentrations or partial pressures. Therefore pay attention to the...
Tue Jan 28, 2020 6:38 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Closed vs isolated systems
Replies: 24
Views: 64

Re: Closed vs isolated systems

A closed system cannot exchange mass with its surroundings but it can exchange energy, while an isolated system cannot exchange either. So what would be an example of a closed system and an example of an isolated system? An example of a closed system is an ice pack, like the shakeable ones that are...
Sun Jan 26, 2020 11:18 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: pKa/pKb
Replies: 3
Views: 18

Re: pKa/pKb

pKa and pKa are the -log of Ka/Kb. You can convert pH to Ka using 10^-ph. You can do the same with pOH by converting pOH to Kb using 10^-pOH. And Just for clarification they are related to pH because they are dissociation constants, they show how much an acid or base dissociate which then determine...
Thu Jan 23, 2020 4:23 pm
Forum: Phase Changes & Related Calculations
Replies: 3
Views: 15

Lavelle is going to teach us the dynamics of Thermochemistry first so that we have an understandable foundation of what is going on. Then we are going to start calculations, but ultimately everything on the syllabus will covered so just follow what is assigned, it will all be important
Thu Jan 23, 2020 4:21 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Shifting Forward or Reverse
Replies: 7
Views: 22

Re: Shifting Forward or Reverse

When you reduce a reactant, why does the equilibrium shift in the reverse direction? When you reduce something in the reaction the equilibrium shifts towards it not away from it because now you are making less of that and therefore equilibrium will shift that way to try and reduce the effect on the...
Thu Jan 23, 2020 4:07 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Changes in pressure
Replies: 5
Views: 26

Re: Changes in pressure

Adding an inert gas doesn't shift equilibrium because the inert gas doesn't react with anything in the reaction therefore it will be present in the reactants and products equally. However Pressure and and volume will change the concentrations of the system because think about having a big container ...
Thu Jan 23, 2020 4:03 pm
Forum: Phase Changes & Related Calculations
Topic: - and + H values
Replies: 5
Views: 28

Re: - and + H values

delta H has a negative or positive value because it is whether a reaction is absorbing heat (breaking down molecules) or giving off heat (consolidating molecules). If you're going from a solid to gas it will be endothermic and delta H will be positive because you need to break down the solid to tran...
Thu Jan 23, 2020 3:57 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: pKa to Kb
Replies: 12
Views: 41

Re: pKa to Kb

What makes logical sense for me is to think, pka=-log(Ka), therefore Ka=10^-pka. Then we know Kw= Ka x Kb and so you should rearrange the equation so that Kw/Ka=Kb and now you have your Kb value! Make sure you take it slow and pay close attention.
Thu Jan 16, 2020 8:29 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Peer Learning Worksheets
Replies: 3
Views: 49

Peer Learning Worksheets

Hey, are there any key words or ways to find worksheets that the TAs handed out in their step up sessions? I am unable to attend most of them because I have work.
Thu Jan 16, 2020 8:21 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Weak and strong acids/bases
Replies: 2
Views: 10

Re: Weak and strong acids/bases

Strong acids and strong bases completely dissociate to form ions in solution but weak acids and bases don't completely ionize therefore the reaction is reversible.
Thu Jan 16, 2020 7:52 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Water in Equilibrium Constant Eq.
Replies: 3
Views: 12

Re: Water in Equilibrium Constant Eq.

Dina 2k wrote:if a different solvent was used, besides water, would it be included in the calculations?

I believe solvents aren't ever included in the equilibrium constant
Thu Jan 16, 2020 7:49 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Protonation & Deprotonation
Replies: 9
Views: 33

Re: Protonation & Deprotonation

Tue Jan 14, 2020 8:50 pm
Forum: Administrative Questions and Class Announcements
Topic: Test 1
Replies: 7
Views: 38

Re: Test 1

He'll let us know for sure, but it's all the material covered up until the Friday before the Test. So, for test 1, it will most likely be all the information presented up until this Friday, January 17. Agreed! But to answer your question I would guess no because he will probably cover that when we ...
Tue Jan 14, 2020 8:49 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Endothermic and exothermic reactions
Replies: 11
Views: 36

Re: Endothermic and exothermic reactions

Also, the way I think about it is that endothermic reactions like heat because they absorb it, so more heat will help the reaction favor the products. If the reaction is exothermic, it "doesn't like heat" so it lets it go, and wouldn't want to create more products if the temperature rises...
Tue Jan 14, 2020 8:46 pm
Forum: Administrative Questions and Class Announcements
Topic: Are Lectures Bruincasted?
Replies: 10
Views: 59

Re: Are Lectures Bruincasted?

Where can you view modules? If you enter CCLE and click on Lavelle's chemistry class it will take you to his website where you will type in the password and then scroll down towards the bottom where it says Chemical equilibria Pre-Assessment, video, and post assessment. Lavelle has these modules fo...
Tue Jan 14, 2020 8:43 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Lyndon Bui Workshops
Replies: 7
Views: 102

Re: Lyndon Bui Workshops

Hi! While I can't find any of his worksheets on Chem Community, it seems that he'll often use worksheets as the backbone of his workshops. Lyndon has workshops in Covel 210 on Mondays from 6-8. If you attend, I'm sure you will receive some of his practice problems. Thank You! I'd love to go to his ...
Tue Jan 14, 2020 2:59 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Lyndon Bui Workshops
Replies: 7
Views: 102

Lyndon Bui Workshops

Hi! Has Lyndon given out any worksheets yet? If so can someone please share what the key words are to find them? Thank you! ((:
Tue Jan 07, 2020 4:17 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5G.11
Replies: 3
Views: 34

Re: 5G.11

If a solid or liquid is in the reaction then it does not get represented or more likely it gets counted for as the number 1. However its important to pay attention to the fact that you must stick to the Kc equation of [products]/[reactants] so if the products are both solids or liquids then Kc will ...
Tue Jan 07, 2020 4:13 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium Constant for Solids/Gases
Replies: 5
Views: 33

Re: Equilibrium Constant for Solids/Gases

For the modules, if we were given an equation like A (g) + B (g) --> C (s), why do we write the equilibrium constant as 1/[A][B] instead of just [A][B]? I thought we were supposed to just take solids and liquids out of the equilibrium constant. It is still written as 1/[A][B] because A & B are ...
Tue Jan 07, 2020 4:09 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Converting Kc to Keq
Replies: 2
Views: 19

Re: Converting Kc to Keq

I believe that Keq is the generalized 'equilibrium constant' but Kc and Kp are forms of Keq (they are not different). Kc refers to concentrations and Kp refers to partial pressures but they both equilibrium constants (forms of Keq).
Tue Jan 07, 2020 4:07 pm
Forum: Administrative Questions and Class Announcements
Topic: Homework 1
Replies: 18
Views: 120

Re: Homework 1

Homework will be due Friday in lecture but for the weeks following it will be due in discussion sections. Remember for homework you get to choose your 5 problems to turn in and each week you can turn in problems from a section that is 'relevant' to what we are learning in class.
Tue Jan 07, 2020 4:05 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Effects of Concentration on Equilibrium
Replies: 6
Views: 41

Re: Effects of Concentration on Equilibrium

If the concentration of a product or reactant is changed while a reaction is in equilibrium, will the reaction then be temporarily shifted out of equilibrium? yes, changing the concentration of the reactant or products will temporarily offset the equilibrium making it shift to the right or left bec...
Sun Dec 08, 2019 3:59 pm
Forum: Significant Figures
Topic: pH sig figs
Replies: 9
Views: 61

Re: pH sig figs

sig figs of pH are counted AFTER the decimal point, and this is due to the log function. so if there are supposed to be 3 sig figs the pH in correct sig figs could be 4.567
Sun Dec 08, 2019 3:57 pm
Forum: Sigma & Pi Bonds
Topic: Sigma Vs Pi
Replies: 10
Views: 63

Re: Sigma Vs Pi

Sigma bonds consist of two orbitals, one electron overlap from end to end, and can rotate. Pi bonds also have two orbitals with one electron overlap, but its side by side, and they cannot rotate. In addition to this, know that a sigma bond is a single bond, a double bond has one sigma bond and one ...
Sun Dec 08, 2019 3:55 pm
Forum: Hybridization
Topic: lone pairs in hybridization
Replies: 6
Views: 42

Re: lone pairs in hybridization

a lone pair acts as other section of electron density in hybridization, so yes they matter. A molecule with 3 bonds and 1 lone pair has 4 regions of electron density and therefore has sp3 hybridization.
Sun Dec 08, 2019 3:54 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: melting point
Replies: 4
Views: 32

Re: melting point

Joseph Saba wrote:Determine it by the intermolecular forces of the molecules as compared with another.

And the stronger the IM forces, the higher the melting and boiling points are because the forces are harder to break to switch in to different phases.
Sun Dec 08, 2019 3:52 pm
Forum: Administrative Questions and Class Announcements
Replies: 5
Views: 77

In the lecture 4's final period the TA was grading the finals as they were coming in, so maybe even sooner. We won't get our physical copies back until next quarter though.
Wed Dec 04, 2019 9:12 pm
Forum: Bronsted Acids & Bases
Topic: Correct equation for 6A.3?
Replies: 4
Views: 35

Re: Correct equation for 6A.3?

I got the correct answers for all the parts in 6A.3, yet I wanted to double check to make sure my chemical equations for the proton transfer equilibria were correct because that wasn't in the solutions manual. a) H 2 SO 4 + H 2 O <-> H 3 O + + HSO 4 - b) C 6 H 5 NH 3 + + H 2 O <-> H 3 O + + C 6 H 5...
Fri Nov 29, 2019 3:28 pm
Forum: Student Social/Study Group
Topic: Preparing for the final
Replies: 25
Views: 161

Re: Preparing for the final

Definitely attend as many step-up and workshop sessions as possible. Also join group chats that you can ask questions in, watch videos online, review notes, and fill in the learning objective outlines because then you conceptually know and can explain everything as well.
Fri Nov 29, 2019 3:15 pm
Forum: Lewis Acids & Bases
Topic: Proton acceptor and proton donor?
Replies: 33
Views: 139

Re: Proton acceptor and proton donor?

Bronsted acids are proton donors and Bronsted bases are proton acceptors. Lewis acids and Bases have to do with non-bonding electrons.
Fri Nov 29, 2019 3:00 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: coordination number
Replies: 8
Views: 37

Re: coordination number

Coordination numbers are how many bonds (of ligands) attached to the central atom, I don't believe lone pairs count
Fri Nov 29, 2019 2:58 pm
Forum: Administrative Questions and Class Announcements
Topic: Material for the final exam
Replies: 4
Views: 42

Re: Material for the final exam

Mandeep Garcha 3C wrote:If it is like the midterm, I assume we will not learn anything new on the last lecture before the final.

I believe this is probably very likely, so he may use the last lecture to review but also make sure you attend as many review sessions as you can!
Fri Nov 29, 2019 2:49 pm
Forum: SI Units, Unit Conversions
Topic: midterm/final
Replies: 18
Views: 246

Re: midterm/final

It should be mostly calculations, but also you should know the quantum world photoelectric effect and descriptions of trends and so on. Its fair game to be asked to explain IM Forces and other things.
Fri Nov 29, 2019 2:44 pm
Forum: Lewis Acids & Bases
Topic: HCl vs HF
Replies: 19
Views: 98

Re: HCl vs HF

F is more electronegative than Cl so it is less likely to give off the H+ ion. This means that HCl can disassociate easier, making it the stronger acid. This exactly explains why, but in addition HCl is a stronger acid than HF because HCl has a longer/weaker bond between the H and Cl making it easi...
Sun Nov 24, 2019 3:55 pm
Forum: Naming
Topic: 9C.3
Replies: 2
Views: 45

Re: 9C.3

I feel like we won't be given this chart and will have to know the general trends, hopefully after a lot of practice these rules pf prefixes and suffixes will start to become routine is the goal I would assume.
Tue Nov 19, 2019 2:37 pm
Forum: Ionic & Covalent Bonds
Topic: Study Group
Replies: 8
Views: 92

Re: Study Group

Are you guys still meeting??
Tue Nov 19, 2019 2:35 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: interaction potential energy
Replies: 2
Views: 27

Re: interaction potential energy

Will we have to use this equation on the test at all??
Tue Nov 19, 2019 2:23 pm
Forum: Determining Molecular Shape (VSEPR)
Replies: 1
Views: 32

Does anyone have any extra worksheets or resources to get more practice of the material that is going to be on Test 2?
Tue Nov 19, 2019 1:58 pm
Forum: Hybridization
Topic: test 2
Replies: 6
Views: 49

Re: test 2

tonyhu wrote:Is hybridization going to be the main topic on test 2?

Hybridization will not be on the test. I would not focus on studying this until after the test, focus on the topics from 3F.4, 3F.5, and 2E-F
Tue Nov 19, 2019 1:56 pm
Forum: Administrative Questions and Class Announcements
Topic: Test #2
Replies: 22
Views: 243

Re: Test #2

205192823 wrote:So do we technically need to do chapters 2D, 2E, and 2F, since the midterm was up until 2D right?

Also section 3F.4 and 3F.5 !!
Wed Nov 13, 2019 9:11 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Self Check 2E.3A
Replies: 2
Views: 27

Re: Self Check 2E.3A

2E.3.A asks for the molecule HCN, not NH3, is that correct? In this case you would first draw the lewis structure that is C as the central atom connected with a single bond to H on one side and a triple bond to N on the other side and N has 1 pair of lone electrons. Then the shape is Linear because ...
Wed Nov 13, 2019 9:05 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 2E.5 b
Replies: 4
Views: 24

Re: 2E.5 b

Because it is ClO2+ ion there are 18 valence electrons because the + means to subtract 1 electron. Therefore draw the lewis structure with Cl as the central atom and O atoms connected by double bonds to Cl, then 2 sets of lone electron pairs on each O and 1 set of lone electron pair on the Cl. Then ...
Wed Nov 13, 2019 9:01 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Tetrahedral VSPER model
Replies: 7
Views: 57

Re: Tetrahedral VSPER model

A central atom with four bonding regions will always be known as a tetrahedral for its domain geometry BUT if there are lone pairs attached to the central atom this will change. Eventually we will cover molecular geometries which will allow us to name molecules with lone pairs attached to the centra...
Wed Nov 13, 2019 8:58 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Will we need to know these VSEPR shapes as well?
Replies: 10
Views: 79

Re: Will we need to know these VSEPR shapes as well?

I believe we will learn these terms on Friday in Lecture and eventually they will be what we name our VSEPR models as, because they are more specific and telling of the actual shape of the molecule.
Wed Nov 13, 2019 8:55 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPER shape for IF4-
Replies: 5
Views: 35

Re: VSEPER shape for IF4-

Because IF4- has 4 bonding sites and 2 lone pairs of electrons, it technically has 6 regions of electron density. Since there are 6 regions of electron density then the Domain geometry is Octahedral, but the Molecular geometry is Square Planar due to the 2 lone pairs. We have not yet covered this in...
Fri Nov 08, 2019 4:50 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge Shortcut
Replies: 3
Views: 29

Re: Formal Charge Shortcut

Count the bonds around the atom as 1 electron and then count each lone pair as 2 electrons (count each dot you drew individually) and you want this to add up to the number of valence of electrons of the actual element. However if this is on a test then you should show the actual calculation.
Fri Nov 08, 2019 4:36 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Atoms to Moles
Replies: 6
Views: 100

Re: Atoms to Moles

To go from Atoms to moles you take the number of atoms and divide it by avogadros number over 1 mol then you can convert it to what every molecule you need.
Fri Nov 08, 2019 1:15 pm
Forum: Electronegativity
Topic: Trend of Electronegativity
Replies: 22
Views: 106

Re: Trend of Electronegativity

Fluorine is the most electronegative element. Electronegativity decrease down a column and across a row (right to left). Or oppositely it increases up a column and left to right across a row.
Fri Nov 08, 2019 1:06 pm
Forum: Balancing Chemical Reactions
Topic: Balancing This Equation
Replies: 11
Views: 107

Re: Balancing This Equation

Write a balanced combustion reaction for solid nicotine (C10H14N2). (Hint: The reaction produces N2 gas). How can we balance it when both sides don't have Oxygen? Or does it? How are we supposed to figure this out? Combustion reactions always are a compound +O2 and produce CO2+H20 So this should lo...
Fri Nov 08, 2019 1:02 pm
Forum: SI Units, Unit Conversions
Topic: Kj
Replies: 6
Views: 60

Re: Kj

Yes, Kj to J is the same as Kg to grams and there are 1000J in 1 Kj
for dimensional analysis you should do 1Kj *1000J/1Kj (cancel the units)
Tue Nov 05, 2019 10:56 am
Forum: Lewis Structures
Topic: When to draw Resonance Structures
Replies: 14
Views: 82

When to draw Resonance Structures

For the midterm, should we always draw the resonance structures or will we be okay with drawing the most stable structure? I guess more clearly I am wondering if Dr. Lavelle will specify "draw the Lewis Structure and its resonance forms" or should we still draw the resonance structures if ...
Sun Nov 03, 2019 10:04 am
Forum: Dipole Moments
Topic: Content on the Midterm [ENDORSED]
Replies: 3
Views: 69

Re: Content on the Midterm[ENDORSED]

The midterm will cover everything from the first 3 outlines. Review through 2D of the Chemical Bonds chapter, this will include Quantum and so on. Look on his website for the chapter outlines, it will really help understand what content will be covered.
Sun Nov 03, 2019 10:02 am
Forum: SI Units, Unit Conversions
Topic: midterm 1
Replies: 5
Views: 64

Re: midterm 1

Everything from Outline 1: Review of Chemical & Physical Principles and Outline 2: The Quantum World will be on the midterm. Almost everything from Outline 3: Chemical Bonds will be on the midterm cutting off at Focus 2D. everything you need to know about the outlines is on Dr. Lavelle's websit...
Sun Nov 03, 2019 9:56 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Week 4 HW questions
Replies: 4
Views: 93

Re: Week 4 HW questions

You choose! Lavelle always says that you can turn in anything that is relevant to what we are currently learning, so I would probably do 5 problems from the chapter I am struggling the most in.
Sun Nov 03, 2019 9:54 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Writing e- Configurations
Replies: 15
Views: 89

Re: Writing e- Configurations

If the question doesn't explicitly state "write the full electron configuration" then you should be fine using short hand notation. If it's not stated then you choose what you feel more comfortable using.
Sun Nov 03, 2019 9:46 am
Forum: Student Social/Study Group
Topic: Midterm Length
Replies: 7
Views: 91

Re: Midterm Length

The midterm is Wednesday Nov 6 from 6-8pm. The midterm is 2 hours long with 8 questions. These are the room assignments: 14A-1, 10am class: Last name A-L in HAINES 39. Last name M-Z in CS50. 14A-3, 12noon class: Last name A-M in MOORE 100. Last name N-Z in FRANZ 1178. 14A-4, 2pm class: Last name A-L...
Wed Oct 23, 2019 4:28 pm
Forum: Trends in The Periodic Table
Topic: Location of elements
Replies: 12
Views: 113

Re: Location of elements

I think it will be valuable to know, you can look it up online and you will be able to see that the metals, non metals, noble gases etc. are grouped together. This will be good to know when we start getting asked about characteristics of elements and what happens during the reaction, etc. You should...
Wed Oct 23, 2019 4:24 pm
Forum: Lewis Structures
Topic: Drawing lewis structures
Replies: 5
Views: 282

Re: Drawing lewis structures

How do you draw lewis structures when there are positive and negative molecules? I remember we had to put the negative parts as far away from each other as possible, but are there any specific rules for these? Positive charges will subtract an electron in a lewis structure and negative charges will...
Wed Oct 23, 2019 4:21 pm
Forum: Ionic & Covalent Bonds
Topic: Back and Fourth Arrows
Replies: 6
Views: 244

Re: Back and Fourth Arrows

When are doubled headed arrows used in chemical formulas, or in other words, arrows pointing in both directions? Is it when a reaction is reversible? In that case when is it acceptable to use these arrows against using arrows just pointing one way? Yes, that is correct. If the arrows point both way...
Wed Oct 23, 2019 4:18 pm
Forum: Ionic & Covalent Bonds
Topic: Week 4 Homework
Replies: 9
Views: 103

Re: Week 4 Homework

You should do whatever homework you feel you need the most work on. If you aren't ready to move on past quantum then continue to do those problems but if you feel confident then move on to Chemical Bonds homework. It is up to you which you will turn in.
Wed Oct 23, 2019 4:16 pm
Forum: Lewis Structures
Topic: Finding Valence Electrons
Replies: 8
Views: 51

Re: Finding Valence Electrons

Valence electrons correspond to the elements group #
Fri Oct 18, 2019 9:21 am
Forum: Einstein Equation
Topic: Joules units
Replies: 6
Views: 103

Re: Joules units

Hello can anyone explain to me why Joules in Planck's Constant is kg x m^2 x s? Thanks. Joules in Planck's Constant is expressed as such because it helps for unit cancellation, depending on what you are solving for one of these two expressions will be easier to visually see how you obtain your fina...
Fri Oct 18, 2019 9:17 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: how to prepare
Replies: 22
Views: 143

Re: how to prepare

Definitely take advantage of the step-up sessions! But also, many of the equations and conversions will be given to you on the front sheet of tests. Therefore it will be more helpful to try and focus on the mechanics of the problems and overall idea, instead of stressing too hard on memorizing each ...
Fri Oct 18, 2019 9:09 am
Forum: Properties of Light
Topic: What are the units of hertz
Replies: 41
Views: 239

Re: What are the units of hertz

1 Hz = 1 cycle/second but is expressed as 1s^-1 most typically which will help you many times to clearly see unit calculation. Also when you end up with the unit s^-1 if the problem doesn't clearly say to express it like that, it is appropriate to change it back to Hz.
Fri Oct 18, 2019 9:05 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: G orbital
Replies: 6
Views: 42

Re: G orbital

I believe it is probably best to know of the G-orbital and have a basic knowledge of it's features and such. However, I don't think you need to be an expert on this topic. Just know it exists.
Wed Oct 16, 2019 1:13 pm
Forum: Properties of Light
Topic: Planck's Constant
Replies: 2
Views: 41

Re: Planck's Constant

Planck's Constant is usually expressed as 6.626 x 10^-34 J.S.
But often it is most useful for cancelling units as: 6.626 * 10^-34 kg.m^2.s^-1
Wed Oct 09, 2019 6:33 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Showing work in detail
Replies: 7
Views: 128

Re: Showing work in detail

I would highly recommend using units on each step of your dimensional analysis so you can clearly see the units cancelling out, showing that you did the work correctly. This will help the grader as well as yourself so you are able to explicitly navigate your way to the right units.
Wed Oct 09, 2019 6:29 pm
Forum: Significant Figures
Topic: Range of Sig Figs
Replies: 8
Views: 71

Range of Sig Figs

Does anyone know if Lavelle accepts a range for accuracy on sig figs. For example if your answer comes out to 2.99487 but need it to be 4 sig figs, would it be 3.000 or 2.995? Are both answers acceptable?
Wed Oct 09, 2019 6:26 pm
Forum: Properties of Light
Topic: Speed of Light constant
Replies: 7
Views: 34

Re: Speed of Light constant

I think ideally it would be easier to use 3.00x10^8 m/s for the speed of light because 1. that is what Lavelle uses and 2. because it's slightly easier to remember as well as write down when you are working at a faster pace to complete a test or so on. It should not throw off your sig figs and I'm n...
Wed Oct 09, 2019 6:20 pm
Forum: Properties of Light
Topic: Homework Problems
Replies: 3
Views: 43

Re: Homework Problems

The chapter we are on begins on page #1 in the book and you will find the problems for 1A on pages 9-10. As you keep on working you will find that the rest of the chapter and problems follow in order.
Wed Oct 09, 2019 6:16 pm
Forum: Empirical & Molecular Formulas
Topic: E15 Homework Problem
Replies: 3
Views: 53

Re: E15 Homework Problem

To go about this problem: 1. Look at the given information M(OH)2 = 74.10 g/mol 2. M is a variable that currently is unspecified (it is just some random metal) BUT you know the elements O and H, therefore find the molar mass for (OH)2 = 34.01 g/mol 3. Now that you know the molar mass of (OH)2, you c...
Thu Oct 03, 2019 1:26 pm
Forum: Properties of Light
Topic: Quantum homework
Replies: 4
Views: 65

Re: Quantum homework

Homework for each week will be due in your discussion section after this Friday. However each week you will have the option to turn in problems from the previous week sections (e.g. this Friday we have homework from the review section problems but our test is in our discussion sessions NEXT week, so...
Wed Oct 02, 2019 3:19 pm
Forum: Balancing Chemical Reactions
Topic: States of Matter in a Chemical Equation [ENDORSED]
Replies: 11
Views: 104

Re: States of Matter in a Chemical Equation[ENDORSED]

PranaviKolla3G wrote:Also, what are all the shorthand notations for the states of matter? (ex: for solids, it is (s))

For solids (s), Aqueous Solutions (aq), Liquids (l), and Gases (g)
Tue Oct 01, 2019 11:29 am
Forum: Empirical & Molecular Formulas
Topic: 5 Homework Problems Due
Replies: 21
Views: 220

Re: 5 Homework Problems Due

For this week we only have 5 problems due and they will be turned in at the beginning of your lecture on Friday. They can be any 5 from any section that he listed. In the future however, you will do 5 from any of the sections or problems he lists and they will be due in your discussion section. To a...