Search found 102 matches
- Fri Mar 13, 2020 12:28 pm
- Forum: General Rate Laws
- Topic: 7A.15a
- Replies: 4
- Views: 344
Re: 7A.15a
For A, you have to ensure that only the concentrations for A are changing. Therefore, the concentrations for B must be the same (The concentration of C doesn't matter in this question specifically, so only worry about B). Based on this logic, you can use a combination of experiments such as Rate 2 a...
- Fri Mar 13, 2020 12:22 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Slow Step Mechanism
- Replies: 7
- Views: 516
Re: Slow Step Mechanism
I think it really depends on the step mechanism itself. However, for our exam purposes, I believe they will most likely have the slow step in the middle somewhere (my speculation).
- Fri Mar 13, 2020 12:20 pm
- Forum: Administrative Questions and Class Announcements
- Topic: ENDGAME Review Session
- Replies: 71
- Views: 5870
Re: ENDGAME Review Session
Thank you for everything Lyndon!!!
- Fri Mar 13, 2020 12:18 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Slow Step Determination
- Replies: 5
- Views: 391
Re: Slow Step Determination
They will tell you if a step is low usually. You can use that information to decide that the slow step is what determines the rate of the reaction.
- Fri Mar 13, 2020 10:04 am
- Forum: Administrative Questions and Class Announcements
- Topic: Final
- Replies: 2
- Views: 252
Re: Final
I think open book means you have access to lecture notes, but I don't think it includes chemistry community. I am unsure about your other questions; Lavelle may speak on those in later emails!
- Sun Mar 08, 2020 10:19 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: Rate Laws
- Replies: 3
- Views: 263
Re: Rate Laws
No, I believe you have to calculate it based off of the rate law equation, or through the method of initial rates.
- Sun Mar 08, 2020 10:16 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: 7C.7: Rate laws
- Replies: 2
- Views: 254
7C.7: Rate laws
The answer key does not include rate laws for the reverse reaction; however, in the book it says every forward reaction has a reverse reaction associated with it. So, I am wondering when do we use/write down a reverse reaction rate and when do we not?
- Sun Mar 08, 2020 10:14 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: how?
- Replies: 3
- Views: 332
Re: how?
You can use the method of initial rates that we learned in class to determine n and k!
- Sun Mar 08, 2020 10:11 pm
- Forum: First Order Reactions
- Topic: 7B.3
- Replies: 2
- Views: 217
Re: 7B.3
You just use stoichiometric relations to find the concentration of A. If 0.034M B was created, that means that two times that amount of A was used in creating B. Therefore, you subtract 0.068 from 0.153 to find [A]t (0.085M).
- Sun Mar 08, 2020 10:06 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell Diagrams
- Replies: 6
- Views: 449
Re: Cell Diagrams
Also, when the states are the same, you put the higher charge on the left and lower charge on the right
- Mon Mar 02, 2020 4:31 pm
- Forum: Balancing Redox Reactions
- Topic: Balancing Redox Reaction in 6L.3(d)
- Replies: 1
- Views: 175
Re: Balancing Redox Reaction in 6L.3(d)
I used the following half reaction:
2H2O + 4e- + O2 --> 4OH-
I used this half reaction because the cell diagram shows that there is an O2 and an OH-. This is why I didn't use the other half rxns that include species like H+.
2H2O + 4e- + O2 --> 4OH-
I used this half reaction because the cell diagram shows that there is an O2 and an OH-. This is why I didn't use the other half rxns that include species like H+.
- Sun Mar 01, 2020 3:58 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Textbook question 6N.7
- Replies: 1
- Views: 191
Re: Textbook question 6N.7
I found this helpful: viewtopic.php?f=142&t=60522
- Sun Mar 01, 2020 10:59 am
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Problem 6N.1 part b
- Replies: 4
- Views: 449
Problem 6N.1 part b
Both the half reactions for In3+/In2+ and U3+/U4+ use only one electron and it balances out correctly. So, why does the solution manual uses 2e- for n?
- Sat Feb 29, 2020 3:55 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Pt in cell diagrams
- Replies: 3
- Views: 254
Pt in cell diagrams
When does the Pt go on both sides of the cell diagram and when does it not? For example, in Problem 6M.5 the Pt is only on the right side of the diagram.
Also, in general, how do you determine when to use Pt? Are there specific rules for it?
Also, in general, how do you determine when to use Pt? Are there specific rules for it?
- Sat Feb 29, 2020 1:42 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: 6L.7b half reactions [ENDORSED]
- Replies: 1
- Views: 138
6L.7b half reactions [ENDORSED]
I used different half rxns and got the same E. Does it matter which ones you use? If so, how would you tell for this problem?
The overall rxn is: H+ + OH- --> H20
The answer key uses O2 in the half rxns
I used the following half rxns:
2H+ + 2e- --> H2
H2 + 2OH- --> 2e- + 2H20
The overall rxn is: H+ + OH- --> H20
The answer key uses O2 in the half rxns
I used the following half rxns:
2H+ + 2e- --> H2
H2 + 2OH- --> 2e- + 2H20
- Sat Feb 29, 2020 1:29 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Problem 6L.7a: Cell Diagram Notation
- Replies: 1
- Views: 187
Problem 6L.7a: Cell Diagram Notation
In the answer key, the Ag(s) and AgBr(s) are separated by "|" however, I thought we only use that line when two species are in different phases. Can someone clarify why we use the "|" between Ag(s) and AgBr(s) in this question?
- Sun Feb 23, 2020 6:26 pm
- Forum: Balancing Redox Reactions
- Topic: Balancing Redox EQs
- Replies: 10
- Views: 696
Re: Balancing Redox EQs
It depends on if the reaction is occurring in an acidic or basic solution. If it is an acidic solution you use H+ and if it is a basic solution you use OH-
- Sun Feb 23, 2020 6:23 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Units for delta G calculations w/E
- Replies: 1
- Views: 149
Re: Units for delta G calculations w/E
A lot of times we separately divide the final answer by moles in order to get those units. It's similar to how in the thermo unit, when we calculated delta H of formation we divided by mol to get J/mol even though you normally get just joules by doing products-reactants.
- Sun Feb 23, 2020 6:18 pm
- Forum: Van't Hoff Equation
- Topic: Notes from 02/14/2020
- Replies: 1
- Views: 176
Re: Notes from 02/14/2020
Sending it right now!
- Sat Feb 22, 2020 5:16 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: 5G.21
- Replies: 4
- Views: 567
Re: 5G.21
I would use the equation: G=-RTlnK. You calculate G using appendix 2A, and solve for K.
- Sat Feb 22, 2020 5:09 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Salt Bridge
- Replies: 10
- Views: 644
Re: Salt Bridge
A salt bridge comes is significant to a galvanic cell because it eases the charge buildup. It allows the ions to transfer when which allows the solutions to stay neutral overtime.
- Fri Feb 14, 2020 11:19 pm
- Forum: Calculating Work of Expansion
- Topic: Reversible vs Irreversible
- Replies: 13
- Views: 904
Re: Reversible vs Irreversible
In terms of entropy, when a system is reversible it means that the delta S total is = 0.
- Fri Feb 14, 2020 11:01 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Delta S
- Replies: 6
- Views: 384
Re: Delta S
Delta S total = 0 to in a reversible reaction not delta S. Remember Delta S implies Delta S of the system.
- Fri Feb 14, 2020 10:48 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: State functions
- Replies: 5
- Views: 278
Re: State functions
Yes! Lyndon told us this during a review session (capital letters indicate a state function): "if you are Depressed or Pressured, all you want is TV and HUGS." State functions are: density, pressure, temperature, volume, enthalpy, internal energy, gibbs free energy, and entropy.
- Fri Feb 14, 2020 10:29 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Entropy in reversible and irreversible
- Replies: 3
- Views: 293
Re: Entropy in reversible and irreversible
I don't think it matters for entropy. I believe we always use the RTln(V2/V1).
- Sun Feb 09, 2020 11:35 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: using ICE tables
- Replies: 3
- Views: 324
Re: using ICE tables
I believe it is just for molarity, that way all the values in your ICE table are consistent and comparable.
- Sun Feb 09, 2020 11:33 am
- 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: W
- Replies: 4
- Views: 238
Re: W
No, I believe that W is the number of ways a molecule can be arranged. That's why BF3 has W=1 not three. Whereas COF2 has W=1 because the oxygen can be in 1 of three positions.
- Sun Feb 09, 2020 11:32 am
- 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: Residual Entropy
- Replies: 5
- Views: 116
Re: Residual Entropy
I believe residual entropy is the energy that remains even when a sample is brought to 0 Kelvin caused by disorder in the sample.
- Tue Feb 04, 2020 4:21 pm
- Forum: Calculating Work of Expansion
- Topic: Problem 4.7a
- Replies: 1
- Views: 85
Problem 4.7a
How do you calculate the delta n? And what is the delta n?
- Mon Feb 03, 2020 5:32 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Problem 4C.3a
- Replies: 1
- Views: 81
Problem 4C.3a
The answer key doesn't have an answer for the change in enthalpy. Can someone with the solutions manual confirm or deny if the answer is +765J for delta H? If it isn't, how do we find the correct answer?
- Sat Feb 01, 2020 6:28 pm
- Forum: Calculating Work of Expansion
- Topic: Reversible Process
- Replies: 2
- Views: 130
Re: Reversible Process
Yes! When external pressure is constant, it is an irreversible process.
- Sat Feb 01, 2020 6:27 pm
- Forum: Calculating Work of Expansion
- Topic: Work positive or negative
- Replies: 5
- Views: 214
Re: Work positive or negative
When the system does work on something outside of the system, it is negative work because they system is losing energy (ex. the piston moves out/expansion). When something else is doing work on the system, it is positive work because the system is gaining energy (ex. piston moves in/compression). I ...
- Sat Feb 01, 2020 6:25 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: reversible vs irreversible expansion
- Replies: 4
- Views: 183
Re: reversible vs irreversible expansion
For an irreversible expansion, the external pressure is constant and for reversible expansion, external pressure can change.
- Sat Feb 01, 2020 6:24 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Elements
- Replies: 8
- Views: 182
Re: Elements
When we talk about oxygen or nitrogen gas, we always assume it is in its diatomic form. This is because it the diatomic form the standard state. Therefore, I think of it as being like the standard or 0 kJ/mol because the element is just naturally just found in that state.
- Sat Feb 01, 2020 4:25 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Problem 4D.7
- Replies: 1
- Views: 53
Problem 4D.7
The question asks for the delta U, but they just give us the delta H and the equation. I don't understand how you calculate this? Can we just assume delta U = delta H? And if so, why?
- Thu Jan 23, 2020 12:10 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Test 1 Material
- Replies: 3
- Views: 217
Re: Test 1 Material
No, definitely not for Test 1. We just need to know in terms of enthalpy (delta H).
- Thu Jan 23, 2020 12:08 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Sig figs for pH/pOH, constants and concentrations
- Replies: 2
- Views: 100
Re: Sig figs for pH/pOH, constants and concentrations
This is another link you can refer to: https://lavelle.chem.ucla.edu/wp-conten ... ussion.pdf
- Wed Jan 22, 2020 5:21 pm
- Forum: General Science Questions
- Topic: Test 1: Sig Figs
- Replies: 7
- Views: 411
Test 1: Sig Figs
Do sig figs count on the test 1? If so, how do sig figs work with pH and decimals points. For example, if pH = 5.1 and the question asks for the [H+], how many sig figs would the [H+] have?
- Tue Jan 21, 2020 3:15 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Problem 5.39
- Replies: 1
- Views: 100
Problem 5.39
The question asks to use Table 5E.2. Is it supposed to be 5G.2? Because I can't find a Table 5E.2.
- Tue Jan 21, 2020 3:12 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Table 5G.2
- Replies: 1
- Views: 88
Table 5G.2
Is the K in the second column just K calculated with partial pressures instead of concentrations?
- Wed Jan 15, 2020 11:29 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Le Chatelier overview
- Replies: 3
- Views: 120
Le Chatelier overview
Does Le Chatelier's Principle encompass a change in product/reactant concentration, pressure, and temperature? Or is it just a change in product/reactant concentration?
- Wed Jan 15, 2020 11:26 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Dilute solution cutoff
- Replies: 2
- Views: 122
Re: Dilute solution cutoff
Practically, I would not worry about a cutoff especially for the purpose of this class, because liquids like water are not included in the equilibrium constant expression.
- Wed Jan 15, 2020 11:22 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Units in ICE Table
- Replies: 8
- Views: 275
Re: Units in ICE Table
No, it has to be concentration. If you just use moles it will mess up your calculations when the stoichiometric coefficient is something other than 1 due to the ^n part of the equilibrium equation.
- Wed Jan 15, 2020 10:57 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Ka and Kb
- Replies: 5
- Views: 171
Re: Ka and Kb
No, the B versus the A subscript are just indicative of whether the reaction is an acid or base.
- Wed Jan 15, 2020 5:43 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 5I.29 Barr units
- Replies: 3
- Views: 149
5I.29 Barr units
When the problem gives the partial pressure of one of the compounds in barr units do we divide by the volume to get the initial concentration value? I know in this question it isn't much of an issue because it is 1.0L, but I'm asking for future chem problems.
- Wed Jan 08, 2020 6:13 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Partial Pressures
- Replies: 4
- Views: 175
Re: Partial Pressures
Nope! Only the mole fractions of all the components of a mixture must add to 1, but we are not dealing with that (right now at least).
- Wed Jan 08, 2020 6:11 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Finding K without aq
- Replies: 4
- Views: 183
Re: Finding K without aq
I think the K would just be 1. On a ChemLibre website it just says that solids and liquids are essentially just 1, so for a reaction with all solids and liquids I assume 1 makes the most sense.
- Wed Jan 08, 2020 6:08 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: K for Gases
- Replies: 12
- Views: 397
Re: K for Gases
For a reaction that involves just gases you would use Kp.
- Wed Jan 08, 2020 6:07 pm
- Forum: Ideal Gases
- Topic: R constant in PV=nRT
- Replies: 9
- Views: 325
Re: R constant in PV=nRT
I think it will most likely by R=8.314 J/(Kmol) because that is what Lavelle gave on the formula/constant sheets in 14A. In general just look at the units to figure out what to use, or to see if you need to manipulate the constant.
- Wed Jan 08, 2020 5:27 pm
- Forum: Ideal Gases
- Topic: K
- Replies: 10
- Views: 548
Re: K
Yes, it should be! Because, the only reason we use Kp versus Kc is based on the phases of the reactants/products (and whether the concentration or partial pressure is give to us for gases).
- Wed Jan 08, 2020 5:24 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: changing K
- Replies: 4
- Views: 210
Re: changing K
Yes! Kp and Kc are really both just different input values to get to K so they must have similar implications in practice.
- Sun Dec 08, 2019 4:39 pm
- Forum: Dipole Moments
- Topic: Hydrogen bonding AND Dipole-Dipole?
- Replies: 3
- Views: 384
Re: Hydrogen bonding AND Dipole-Dipole?
Yeah I personally think it is a little redundant, but I believe we are still required to write both.
- Sun Dec 08, 2019 4:07 pm
- Forum: Lewis Acids & Bases
- Topic: Mg(OH)2 Considered strong or weak base?
- Replies: 5
- Views: 3280
Re: Mg(OH)2 Considered strong or weak base?
I put that it was a strong base because the hydroxides of Group 1 and 2 elements are strong bases.
- Wed Dec 04, 2019 9:07 pm
- Forum: Naming
- Topic: Problem C.3 part (d)
- Replies: 2
- Views: 241
Re: Problem C.3 part (d)
Why does the diaqua go before the bisaxalato?
- Wed Dec 04, 2019 8:48 am
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: 6B.9 (i)
- Replies: 1
- Views: 136
6B.9 (i)
I have to find the pH with the information that [H30+] is 1.50 mol/L. The correct answer is a pH of 0.176, but I keep getting -0.176. What am I doing wrong?
- Thu Nov 28, 2019 8:12 pm
- Forum: Conjugate Acids & Bases
- Topic: 6A.1) c)
- Replies: 2
- Views: 240
Re: 6A.1) c)
Yes it can act as a base because it has the potential to receive an H+! So, the conjugate acid would be H2CO3.
- Thu Nov 28, 2019 8:09 pm
- Forum: Dipole Moments
- Topic: Hydrogen Bonding
- Replies: 20
- Views: 1197
Re: Hydrogen Bonding
Matt Sanruk 4F wrote:And O has two hydrogen bonding sites right?
Yes, that's usually correct, but it still depends on how O is arranged on the molecule/compound.
- Thu Nov 28, 2019 7:00 pm
- Forum: Polyprotic Acids & Bases
- Topic: strength of polyprotic acids/bases
- Replies: 2
- Views: 181
Re: strength of polyprotic acids/bases
No I don't think so. Being labeled polyprotic vs monoprotic just refers to how much one CAN donate; not how they normally donate. https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Acids_and_Bases/Monopro...
- Thu Nov 28, 2019 6:56 pm
- Forum: Naming
- Topic: -ido vs -o
- Replies: 5
- Views: 351
Re: -ido vs -o
I think chloro is the correct form (rather than chlorido) when it is a ligand in a coordination compound. Same with fluoro and cyano.
- Thu Nov 28, 2019 6:53 pm
- Forum: Acidity & Basicity Constants and The Conjugate Seesaw
- Topic: Constant K(a)
- Replies: 4
- Views: 291
Re: Constant K(a)
Yes we should know how to calculate Ka especially since we have the equation for it. Just insert the concentrations.
- Fri Nov 22, 2019 12:56 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: What are Ligands?
- Replies: 6
- Views: 226
Re: What are Ligands?
A ligand is just something that attaches onto a transition metal central atom in a coordination compound.
- Fri Nov 22, 2019 12:54 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: polar vs non polar
- Replies: 6
- Views: 423
Re: polar vs non polar
I personally always draw out the formula (unless it's a common compound that I know is non polar or polar like CH4 or H2O respectively). The reason is that a lot of times there are lone pairs that are not reflected in the compound's formula that are discovered only after drawing the structure. For e...
- Thu Nov 21, 2019 5:24 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bond angles for trigonal bipyramidal and octahedral
- Replies: 2
- Views: 138
Re: Bond angles for trigonal bipyramidal and octahedral
Seesaw: <120 degrees for equatorial atoms and very slightly 180 for the axial atoms.
T-shaped: <90 degrees
Square pyramidal: 90 degrees for atoms on the equatorial plane.
Square planar: 90 degrees.
T-shaped: <90 degrees
Square pyramidal: 90 degrees for atoms on the equatorial plane.
Square planar: 90 degrees.
- Thu Nov 21, 2019 5:22 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: Hydrogen Bonding Homework Problem
- Replies: 2
- Views: 287
Re: Hydrogen Bonding Homework Problem
To form a hydrogen bond, the NOF atoms need to have a free lone pair. In butanol, the OH is on the end so it has a free long pair to form hydrogen bonds. However, in diethyl ether the oxygen is in the middle of the atom and has no lone pairs therefore it cannot form a hydrogen bond.
- Tue Nov 19, 2019 8:59 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Problem 3F.3c
- Replies: 2
- Views: 112
Problem 3F.3c
How do you know the arrangement of the H and Cl for a compound like CH2Cl2?
- Wed Nov 13, 2019 7:44 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: 2E.15
- Replies: 3
- Views: 217
2E.15
For problem b, why is it not less than 120 degrees instead of 120 degrees for the atoms in the trigonal plane? I thought that because there is a lone pair, the Cl-Te-Cl bond angle would be less than 120 degrees?
- Wed Nov 13, 2019 7:39 pm
- Forum: Properties of Light
- Topic: Midterm Solution Q2.A
- Replies: 2
- Views: 210
Re: Midterm Solution Q2.A
We have to divide by Avagadro's number to get it from J/mol to J/atom, where atom is 1 Au atom.
- Wed Nov 13, 2019 7:37 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: 2E.5 b
- Replies: 4
- Views: 141
Re: 2E.5 b
I'm not exactly sure about radicals and shapes, but I know that for 2E.5 when they ask OClO they aren't asking about a molecule ClO2, they are just taking about the bond formed between those three atoms (O, Cl, and O). Hope that helps!
- Wed Nov 13, 2019 5:34 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Memorizing and Recognizing Molecular Shapes
- Replies: 4
- Views: 250
Re: Memorizing and Recognizing Molecular Shapes
Yes I believe we will. I think Lavelle will go over the other shapes in class (like with the long pairs).
- Wed Nov 13, 2019 5:33 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Memorization
- Replies: 15
- Views: 1059
Re: Memorization
Yes, we definitely will for the exam/final.
- Sun Nov 10, 2019 6:40 pm
- Forum: General Science Questions
- Topic: London
- Replies: 4
- Views: 347
Re: London
The London Forces! It's a type of intermolecular force and it is interchangeable with dispersion forces, van der waals, and induced dipole-induced dipole forces.
- Sun Nov 10, 2019 6:38 pm
- Forum: Student Social/Study Group
- Topic: Midterm Average
- Replies: 12
- Views: 884
Re: Midterm Average
I remember seeing the midterm average on the last slide of last lecture's powerpoint. I think that was last year's midterm average so I'm sure he will release that stat for our quarter too.
- Sun Nov 10, 2019 6:36 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Calculating formal charge
- Replies: 4
- Views: 284
Re: Calculating formal charge
I think that when calculating formal charge, the concept is not to look at how many electrons an atom has, rather it is to look at the number of SHARED bonds that an atom is involved in.
- Sun Nov 10, 2019 6:34 pm
- Forum: Dipole Moments
- Topic: Electronegativity
- Replies: 3
- Views: 225
Re: Electronegativity
Electronegativity is not an interaction between molecules. Electronegativity is a relative measure of an atom's tendency to pull electrons to itself. On the other hand dipole-dipole is an interaction that is characterized by the partial charge of one atom being attracted to the opposite partial char...
- Sun Nov 10, 2019 6:30 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: Boiling point
- Replies: 5
- Views: 388
Re: Boiling point
Since boiling point is the change from liquid to the solid state it is identified when all the intermolecular bonds are broken. Therefore, the stronger the intermolecular forces (IMF) are the higher the boiling point will be. Hydrogen bonding is one of the stronger intermolecular forces and causes h...
- Sat Nov 02, 2019 1:16 pm
- Forum: Photoelectric Effect
- Topic: Work Function
- Replies: 6
- Views: 402
Re: Work Function
Sometimes the work function is given in joules per mole; however, we need it to be just joules in the problem for the equation. Therefore, ensure to divide the joules/mole number by avagadro's number before you input that value into the problem!
- Sat Nov 02, 2019 1:09 pm
- Forum: Bond Lengths & Energies
- Topic: HW: 2D Q5c
- Replies: 2
- Views: 114
Re: HW: 2D Q5c
Yes, you use the electronegativity difference to determine if a bond is ionic, covalent, polar covalent, etc. Anything with an EN difference > 2.0 is ionic. In terms of determining C-O vs C-S and which is greater you would need to compare the electronegativity of O and S. Remember that we learned th...
- Sat Nov 02, 2019 11:37 am
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Ionization Energy
- Replies: 3
- Views: 173
Re: Ionization Energy
Online it says that the two primary exceptions are that 1) N has an ionization energy greater than O and 2) Be has an ionization energy greater than B. Those are probably the most important to remember since they are located in the first three periods of the periodic table.
- Sat Nov 02, 2019 11:35 am
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Work function units
- Replies: 5
- Views: 335
Re: Work function units
I have also seen questions that give the work function in the units eV, and in that case just remember that you can convert from eV to Joules using the conversion factor give on the conversion sheet which is 1ev is equal to 1.602 × 10-19 J.
- Sat Nov 02, 2019 11:31 am
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Cu and Cr
- Replies: 11
- Views: 597
Re: Cu and Cr
Yes! Because all of the elements in that group have the same valence electron orbital formation; therefore, all of them will exhibit similar characteristics when it comes to arranging valence electrons.
- Fri Oct 25, 2019 9:58 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Formal Charge
- Replies: 4
- Views: 209
Re: Formal Charge
So formal charge is different from ionic charge. Formal charge takes into consideration the bonding in terms of electrons for each individual atom in the compound. Therefore, Cl in a compound does not always have a formal charge of -1. It could also have a formal charge of 0. We don't have to know h...
- Fri Oct 25, 2019 9:54 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Midterm Topics
- Replies: 5
- Views: 245
Re: Midterm Topics
Professor Lavelle has not put up any information about the midterm yet. However, until then I would look over everything we have covered in class so far (and compare your notes with peers to ensure you did not miss anything). I believe the midterm will also cover the content from Exam #1, but I woul...
- Fri Oct 25, 2019 9:51 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: second quantum number
- Replies: 2
- Views: 114
Re: second quantum number
Yes! Those l values will always correspond to their respective s, p, d or f subshells. The only thing that changes when you move up shells (ex. n=2 to n=4) is the possibility of subshells or l-values that work for that shell. For n=2, an electron can be in l=0 or 1 and for n=4, an electron can be in...
- Fri Oct 25, 2019 9:49 pm
- Forum: Lewis Structures
- Topic: Drawing Lewis Structures
- Replies: 2
- Views: 109
Re: Drawing Lewis Structures
That's correct! Because the compound is neutral and abides by the normal electron states of the atoms.
- Fri Oct 25, 2019 2:11 pm
- Forum: Lewis Structures
- Topic: Formal Charges
- Replies: 4
- Views: 183
Re: Formal Charges
Also remember that if you are calculating the total formal charge of an ionic compound by adding all the individual formal charges of the elements, you want the final value to equal to the charge of the ionic compound. For example in SO4 2- the final value should add to -2 NOT ZERO. Instead, to dete...
- Fri Oct 25, 2019 2:07 pm
- Forum: Lewis Structures
- Topic: Double Bonds
- Replies: 6
- Views: 191
Re: Double Bonds
Before considering formal charge, you usually use double bonds when you are trying to make every element satisfy the octet rule. So for example, if a compound has only 24 electrons and with your initial Lewis Structure with only single bonds you notice you are at 26 electrons, you would most likely ...
- Fri Oct 18, 2019 12:10 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: 1D. Quantum Numbers and Orbitals
- Replies: 2
- Views: 145
Re: 1D. Quantum Numbers and Orbitals
The number of orbitals in a subshell can be determined by ml which is equal to 2l+1. Therefore, because we know that l equal to 0 refers to the s-orbital, 1 is the p-orbital,...3 is the f-orbital, we can use this information in the question. For a) since we are looking at p, which has an l value of ...
- Fri Oct 18, 2019 12:01 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Nodal Planes
- Replies: 10
- Views: 292
Re: Nodal Planes
Nodal planes are any areas where the is zero probability of electron density. Therefore, there will be no electrons in that area.
- Fri Oct 18, 2019 12:00 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: 1D. Quantum Numbers and Orbitals
- Replies: 1
- Views: 119
Re: 1D. Quantum Numbers and Orbitals
The question is basically testing you on if you know the meaning of l in the context of orbitals. Remember that l equals 0 refers to the s subshell, 1 to p, 2 to d, and 3 to f. And within each of the subshells, s has 1 orbital, p has 3, d has 5, and f has 7. Therefore, for D24a the answer should be ...
- Fri Oct 18, 2019 11:52 am
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: 1D. Quantum Numbers and Orbitals
- Replies: 2
- Views: 140
Re: 1D. Quantum Numbers and Orbitals
No, Lavelle said we are not required to know how to draw any of the orbitals. Although, I think it's probably good to be familiar with what they look like (especially s and p)
- Fri Oct 18, 2019 11:49 am
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Orbitals and Probability
- Replies: 2
- Views: 125
Re: Orbitals and Probability
psi by itself represents a wave function, or the position of a wave at (x,y,z). In simpler terms, one can just think of it as the height of a wave, or its position. psi^2 represents the probability of finding an e-. Also, Professor Lavelle mentioned in class that psi^2 is always positive because, #1...
- Sun Oct 13, 2019 5:56 pm
- Forum: Photoelectric Effect
- Topic: confirmation.
- Replies: 5
- Views: 227
Re: confirmation.
Basically yeah. It always depends on the threshold frequency; any frequency less that the threshold value won't be enough energy to eject the electron.
- Sun Oct 13, 2019 5:48 pm
- Forum: Properties of Light
- Topic: Speed of light.
- Replies: 10
- Views: 344
Re: Speed of light.
Yes - I believe at this point we will consider the speed of light/radiation as a constant because there are no changing mediums in the problems we are dealing with.
- Sun Oct 13, 2019 5:31 pm
- Forum: Photoelectric Effect
- Topic: Problem 1B.15 (c)
- Replies: 1
- Views: 177
Problem 1B.15 (c)
How do you do 1B.15(c)? You are given that the frequency of the minimum radiation needed to eject an electron is 2.50 x 10^16 Hz and the velocity of an electron that is emitted from a metallic surface by a photon is 3.6 x 10^3 km/s. I thought this was a simple problem but I keep getting 1.2x10^-8 m ...
- Sun Oct 13, 2019 5:26 pm
- Forum: Properties of Electrons
- Topic: Friday Lecture
- Replies: 2
- Views: 62
Re: Friday Lecture
Yeah! Essentially, electrons are described as a circular standing wave around the nucleus. Therefore, the connected line indicated a wave in line or in phase, which is stable whereas the disconnected line is a wave out of phase which is not stable. It is basically explaining why electrons have quant...
- Sun Oct 13, 2019 2:09 pm
- Forum: Properties of Light
- Topic: speed of light
- Replies: 10
- Views: 364
speed of light
Does the speed of light always stay the same? If not, under what circumstances can it change?
- Mon Oct 07, 2019 2:17 pm
- Forum: Properties of Light
- Topic: 1A- Electromagnetic Radiation
- Replies: 4
- Views: 239
Re: 1A- Electromagnetic Radiation
What exactly is meant by option C: "The extent of the change in the electrical field at a given point decreases"? I don't know what it has to do with electromagnetic radiation.
- Thu Oct 03, 2019 10:32 pm
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Avogadro's number
- Replies: 9
- Views: 558
Re: Avogadro's number
If you want to get into specifics, Avagadro's number is the number of Carbon-12 atoms in 1 mol of Carbon-12 (6.022x10^23 atoms). I believe that's how the number was determined way back in the day!
- Thu Oct 03, 2019 10:27 pm
- Forum: Significant Figures
- Topic: Sig Fig Addition and Subtraction
- Replies: 5
- Views: 495
Re: Sig Fig Addition and Subtraction
I think it depends, but definitely follow rules both depending on the step you are on. Usually, you do sig figs at the end of a sequence (like in dimensional analysis); in that case you usually do the normal sig figs rules at the very end of the multiplication. But if you are adding and subtracting ...
- Thu Oct 03, 2019 10:55 am
- Forum: Balancing Chemical Reactions
- Topic: Products of combustion reactions
- Replies: 7
- Views: 308
Re: Products of combustion reactions
I believe combustion reactions always only produce H20 and CO2. I have never seen anything other than that. The only other product other than H20 and CO2 that I can think of would be heat.