Search found 69 matches
- Sat Mar 16, 2019 8:31 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Catalyst effect on activation energy
- Replies: 1
- Views: 210
Catalyst effect on activation energy
If a catalyst doubles the reaction rate, what's the new activation energy? Would it be half?
- Sat Mar 16, 2019 8:15 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Frequency factor units
- Replies: 2
- Views: 683
Frequency factor units
What would the units of the frequency factor be?
- Sat Mar 16, 2019 7:53 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Collision model
- Replies: 3
- Views: 344
Collision model
What is the collision model and activated complex model?
- Sat Mar 16, 2019 7:32 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Pre-equilibrium approach q
- Replies: 3
- Views: 650
Pre-equilibrium approach q
Given general reaction mechanism like
Step 1 (Fast): 2A + B -> C
Step 2 (Slow): C + D -> 2E
Would the expression for the rate of formation of the product E using the pre-equilibrium approach be equal to (2k1k2/k1')[A]^2[B][D] ?
This is question 12 from Lyndon's practice final btw
Step 1 (Fast): 2A + B -> C
Step 2 (Slow): C + D -> 2E
Would the expression for the rate of formation of the product E using the pre-equilibrium approach be equal to (2k1k2/k1')[A]^2[B][D] ?
This is question 12 from Lyndon's practice final btw
- Sat Mar 16, 2019 7:08 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Determining catalysts
- Replies: 2
- Views: 274
Determining catalysts
If given a general reaction mechanism like
Step 1 (Fast): 2A + B -> C
Step 2 (Slow): C + D -> 2E
How do we determine what the intermediates and catalysts are?
This is question 12a on Lyndon's practice final btw
Step 1 (Fast): 2A + B -> C
Step 2 (Slow): C + D -> 2E
How do we determine what the intermediates and catalysts are?
This is question 12a on Lyndon's practice final btw
- Sat Mar 16, 2019 1:03 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Galvanic cells and K
- Replies: 3
- Views: 331
Re: Galvanic cells and K
Joon Chang 2F wrote:You can use the equation
Would that be the same if you're asked to find Ka?
- Sat Mar 16, 2019 12:55 pm
- Forum: Balancing Redox Reactions
- Topic: Acidic v basic conditions
- Replies: 3
- Views: 409
Acidic v basic conditions
If you're balancing redox reactions, does it matter if it's acidic or basic conditions?
- Sat Mar 16, 2019 12:40 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Galvanic cells and K
- Replies: 3
- Views: 331
Galvanic cells and K
If we're just given a galvanic cell with the cell potential, how do we find K for the cell?
- Sat Mar 16, 2019 12:15 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Porous disk
- Replies: 1
- Views: 156
Porous disk
What's the purpose of the porous disk in a concentration cell?
- Fri Mar 15, 2019 9:32 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Test 2 Q 7 [ENDORSED]
- Replies: 5
- Views: 994
Test 2 Q 7 [ENDORSED]
Why is the change in Gibbs free energy negative when ice melts? Isn't it gaining heat or in other words, isn't delta H positive?
- Fri Mar 15, 2019 9:21 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Delta G of galvanic cells
- Replies: 2
- Views: 529
Delta G of galvanic cells
Why do we know that the delta G of galvanic cells will always be less than 0?
- Fri Mar 15, 2019 9:08 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: When to use Nernst
- Replies: 3
- Views: 396
When to use Nernst
I'm confused as to when the Nernst equation would be applicable? When do we know to use it?
- Fri Mar 15, 2019 8:27 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Q6 on the midterm
- Replies: 3
- Views: 564
Q6 on the midterm
For question 6 on the midterm, how do you know that the reaction will do expansion work?
- Thu Mar 14, 2019 3:46 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Reaction mechanisms and slowest step
- Replies: 1
- Views: 204
Reaction mechanisms and slowest step
How do you determine which step is the fastest and which is the slowest? I'm specifically asking for the pre-equilibrium approach. Are we usually given that information? Or is there a way to figure it out with the information we're given? Like in class we were given 2NO + O2 -> 2 N02 with the observ...
- Wed Mar 13, 2019 10:36 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Reducing power
- Replies: 4
- Views: 469
Reducing power
How do you determine reducing and oxidation power?
- Wed Mar 13, 2019 9:02 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Deadline to post
- Replies: 7
- Views: 815
Deadline to post
When is the last day to finish posting on Chemistry Community? For it to count for points this quarter.
- Mon Feb 25, 2019 10:49 pm
- Forum: Balancing Redox Reactions
- Topic: Solution to balancing this redox reaction
- Replies: 1
- Views: 239
Solution to balancing this redox reaction
Balance the following redox reactions in acidic solution.
Br–(aq) + MnO4–(aq) -> Br2(l) + Mn2+(aq)
I got 5Br- + Mn04- + 8H+ -> 5/2(Br2) + Mn^2+ + 4H2O and I just want to know if it's correct
Br–(aq) + MnO4–(aq) -> Br2(l) + Mn2+(aq)
I got 5Br- + Mn04- + 8H+ -> 5/2(Br2) + Mn^2+ + 4H2O and I just want to know if it's correct
- Mon Feb 25, 2019 10:20 pm
- Forum: Balancing Redox Reactions
- Topic: Oxidation number calculation
- Replies: 1
- Views: 197
Oxidation number calculation
How do you find the oxidation number of certain atoms in a molecule? Are there just some oxidation numbers that are certain?
- Mon Feb 25, 2019 8:17 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Vant Hoff Equation
- Replies: 3
- Views: 392
Vant Hoff Equation
Will we be given the Vant Hoff equation for the test? I can't find it on the posted equation sheet
- Mon Feb 25, 2019 7:55 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Value of K in Gibbs free energy equation
- Replies: 3
- Views: 697
Value of K in Gibbs free energy equation
In the equation delta G = -RT*ln(K), K is the equilibrium constant right? But it's stated that a reaction is at equilibrium when delta G equals zero or when K equals 1. There are many reactions that have an equilibrium constant that is not equal to one but is in equilibrium. So I'm confused with thi...
- Mon Feb 25, 2019 7:42 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gibbs free energy at equilibrium
- Replies: 2
- Views: 275
Gibbs free energy at equilibrium
Why is delta G 0 at equilibrium? I don't understand conceptually why that's the case
- Mon Feb 25, 2019 7:28 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Delta S in relation to Gibbs free energy
- Replies: 1
- Views: 275
Delta S in relation to Gibbs free energy
Why does a positive delta S favor the forward process in a reaction?
- Wed Feb 13, 2019 1:03 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Practice problem help
- Replies: 2
- Views: 1394
Practice problem help
I was wondering if my answers are correct for this practice problem. Specifically a and c. The exothermic reaction of carbon disulfide with chlorine is as follows: CS2 (g) + 3Cl2 (g) ⇋ CCl4 (g) + S2Cl2 (g) delta H = -238 kJ Predict the effect of the following changes to the system on the direction o...
- Wed Feb 13, 2019 12:20 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Delta S equations
- Replies: 3
- Views: 1797
Delta S equations
I'm confused about the different delta S equations. When does delta S equal q/t vs nRln(V2/V1) vs nCln(T2/T1)?
- Wed Feb 13, 2019 12:11 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Isothermal work
- Replies: 2
- Views: 2158
Isothermal work
What does it mean that an isothermic reaction has maximum work? Why is that the maximum?
- Tue Feb 12, 2019 11:18 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: When a system can only be prepared in one way
- Replies: 2
- Views: 543
When a system can only be prepared in one way
What does it mean that a system can only be prepared in one way? And why does that mean S=0?
- Tue Feb 12, 2019 10:51 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: n in degeneracy
- Replies: 8
- Views: 2563
n in degeneracy
When calculating degeneracy, does the number of available particles mean the number of UNIQUE available particles? For example would n=2 or 1 if the molecule is 02?
- Tue Feb 12, 2019 10:47 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: Difference in entropy: N2 or CO
- Replies: 1
- Views: 755
Difference in entropy: N2 or CO
My TA was talking about the difference in entropy when comparing N2 and CO. Why does CO have more positive entropy? N2 also has two atoms so wouldn't they be able to take up the same amount of states?
- Tue Feb 12, 2019 10:36 pm
- Forum: Calculating Work of Expansion
- Topic: delta U = 3/2nR(delta T)
- Replies: 2
- Views: 2554
delta U = 3/2nR(delta T)
I have the equation delta U= 3/2 nR delta T = 0 written in my notes and I can't remember what that's in reference to. When does that equation apply?
- Tue Feb 12, 2019 10:17 pm
- Forum: Calculating Work of Expansion
- Topic: Uses of different formulas
- Replies: 3
- Views: 439
Uses of different formulas
How do I know when to use w=-pv vs w= -nrT ln(V2/V1) ?
- Tue Feb 12, 2019 9:27 pm
- Forum: Phase Changes & Related Calculations
- Topic: Phase Change and Temperature
- Replies: 3
- Views: 455
Phase Change and Temperature
Why doesn't temperature change during a phase change? I understand how to interpret the heating curve for water but why is a substance able to absorb so much heat without changing temperature?
- Tue Feb 12, 2019 9:25 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: Degeneracy at its max
- Replies: 2
- Views: 544
Degeneracy at its max
What does it mean that entropy is a maximum at equilibrium? Why is it at its maximum?
- Tue Feb 12, 2019 9:24 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Reversible v irreversible
- Replies: 4
- Views: 781
Reversible v irreversible
What does it mean when an expansion is isothermal/reversible? What would be an example of an irreversible expansion?
- Mon Jan 21, 2019 2:18 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: pKa confusion
- Replies: 2
- Views: 259
pKa confusion
So when Ka is less than 10^-3, it is a weak acid right? So how does pKa work and what's the scale? If pKa is small, then is it a strong acid? And is it the same for pKb?
- Mon Jan 21, 2019 1:32 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Strong acids and bases
- Replies: 4
- Views: 489
Strong acids and bases
Are we supposed to just know the list of strong acids and bases? Or is there a way to figure out if the acid/base is strong and completely dissociates based on the chemical equation we're given?
- Mon Jan 21, 2019 12:32 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Change in temperature's effect on K
- Replies: 4
- Views: 352
Change in temperature's effect on K
I'm confused as to why heating will favor R formation if the reaction is exothermic. If the reaction releases heat, wouldn't the extra heat favor P formation?
- Mon Jan 21, 2019 10:55 am
- Forum: Administrative Questions and Class Announcements
- Topic: TA posted slides (dis 1B)
- Replies: 1
- Views: 241
TA posted slides (dis 1B)
So I'm in discussion 1B and my TA (Wang) posts his slides on here and I don't know how to access them. Does anyone knows what I'm supposed to specifically search for or where I can find them?
- Mon Jan 21, 2019 10:43 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Pure substances
- Replies: 3
- Views: 310
Pure substances
Why aren't solids and liquids included in K expression? Wouldn't it significantly change K?
- Mon Jan 21, 2019 10:35 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Kp vs Kc
- Replies: 7
- Views: 770
Kp vs Kc
When you're calculating K and all the R and P are gases, does it really matter whether or not you use partial pressure or molar concentrations? You would get the same calculation right?
- Fri Dec 07, 2018 6:49 pm
- Forum: Lewis Acids & Bases
- Topic: Lewis v Bronsted
- Replies: 2
- Views: 166
Lewis v Bronsted
How do the different definitions of Lewis acids and Bronsted acids help us conceptualize acids and bases? Would each term be applicable in different problems?
- Fri Dec 07, 2018 6:36 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: TM and oxidation states
- Replies: 1
- Views: 226
TM and oxidation states
Why are transition metals able to have many oxidation states?
- Fri Dec 07, 2018 5:41 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Oxidation state
- Replies: 1
- Views: 221
Oxidation state
I'm confused about how to calculate the oxidation state of a molecule. I don't know if we went over rules in lecture and I just missed it? But when we were talking about the coordination number of the molecule [Fe(CN)6]^4- he mentioned that the oxidation state is +2 and I have no clue where he got t...
- Fri Dec 07, 2018 5:15 pm
- Forum: Sigma & Pi Bonds
- Topic: Rotation
- Replies: 5
- Views: 1048
Rotation
What does it mean that sigma bonds allow bound atoms to rotate? What are they rotating between and why don't pi bonds allow rotation of bound atoms?
- Fri Dec 07, 2018 5:01 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
- Replies: 1
- Views: 293
Hydrogen bonding
Why is hydrogen bonding one of the strongest types of intermolecular forces?
- Fri Dec 07, 2018 4:49 pm
- Forum: Bond Lengths & Energies
- Topic: Shape of molecule
- Replies: 4
- Views: 776
Shape of molecule
Why are the instantaneous dipoles in rod-shaped molecules stronger than those in spherical molecules?
- Fri Dec 07, 2018 12:22 am
- 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 [ENDORSED]
- Replies: 1
- Views: 281
Interaction potential energy [ENDORSED]
When would we need to calculate this on an exam? And what useful information does it provide?
- Fri Dec 07, 2018 12:05 am
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: Induced dipole-induced dipole
- Replies: 1
- Views: 299
Induced dipole-induced dipole
How does dispersion work? How can a dipole be induced then induce another?
- Thu Dec 06, 2018 11:41 pm
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Polarizing power
- Replies: 1
- Views: 355
Polarizing power
Which ions cause large distortions? Do the ions increase in polarizing power as they increase in atomic radius?
- Thu Dec 06, 2018 11:30 pm
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Distorted electrons
- Replies: 2
- Views: 461
Distorted electrons
What does it mean that highly distorted electrons are highly polarizable?
- Thu Dec 06, 2018 11:04 pm
- Forum: Octet Exceptions
- Topic: Radicals
- Replies: 2
- Views: 629
Radicals
So I understand that a radical is a compound with an unpaired electron but I don't understand how this occurs. Why would a radical form? Are there few compounds that can support an unpaired electron? And when Lavelle says that they only exist for a short time, what happens to them?
- Thu Dec 06, 2018 10:50 pm
- Forum: Trends in The Periodic Table
- Topic: Expanded Valence Shells
- Replies: 3
- Views: 604
Expanded Valence Shells
Which atoms accommodate more than 8 valence electrons? And why? I know that P, S, and Cl have expanded valence shells but why? And what are the others that have expanded valence shells?
- Fri Nov 09, 2018 12:00 am
- Forum: Trends in The Periodic Table
- Topic: Atomic radius
- Replies: 3
- Views: 397
Atomic radius
Why does the atomic radius decrease across a period and increase down a group? I'm confused about the relationship between electrons/shells and size.
- Thu Nov 08, 2018 11:52 pm
- Forum: Ionic & Covalent Bonds
- Topic: Proportionality of bond strength
- Replies: 3
- Views: 531
Proportionality of bond strength
Why isn't a double bond twice as strong as a single bond? It seems like there isn't a linear relationship between the amount of bonds and bond strength. Why is that?
- Thu Nov 08, 2018 11:49 pm
- Forum: Ionic & Covalent Bonds
- Topic: Bond strength and state of matter
- Replies: 2
- Views: 576
Bond strength and state of matter
Is there an explicit relationship between the strength of a bond and whether it's a solid, liquid, or gas?
- Fri Nov 02, 2018 12:54 am
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Probability of finding an electron
- Replies: 1
- Views: 201
Probability of finding an electron
I don't quite understand how you would calculate the probability of finding an electron. I understand that it's psi squared but what does that mean exactly? What would you need to know to calculate that?
- Fri Nov 02, 2018 12:51 am
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Ionization energy
- Replies: 1
- Views: 571
Ionization energy
Why is removing a second electron always harder than the first? Does this logic apply to the third electron, meaning the third is even harder to remove than the second?
- Fri Nov 02, 2018 12:47 am
- Forum: Formal Charge and Oxidation Numbers
- Topic: 6th edition: 3.23
- Replies: 1
- Views: 183
6th edition: 3.23
How can chlorine exist in both positive and negative oxidation states? And how do you find the maximum and negative oxidation number that chlorine can have?
- Fri Nov 02, 2018 12:32 am
- Forum: Trends in The Periodic Table
- Topic: Group 13 elements
- Replies: 1
- Views: 142
Group 13 elements
In lecture, Lavelle said that group 13 elements need 5 electrons to complete their octet. What does this mean? They only need 5 electrons in total or need 5 more to complete an octet?
- Fri Nov 02, 2018 12:28 am
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Degenerate orbitals
- Replies: 3
- Views: 382
Degenerate orbitals
Can someone explain the definition of degenerate orbitals? How do you find how many degenerate orbitals a specific orbital has?
- Fri Oct 26, 2018 1:06 am
- Forum: *Shrodinger Equation
- Topic: Schrodinger and quantum numbers
- Replies: 3
- Views: 680
Schrodinger and quantum numbers
How does Schrodinger's equation related to orbitals and quantum numbers?
- Fri Oct 26, 2018 12:01 am
- Forum: DeBroglie Equation
- Topic: Measurable wavelength properties
- Replies: 5
- Views: 584
Measurable wavelength properties
Lavelle worked through an example in class about the wavelength of a car moving at a certain velocity. He asked if the car has "any measurable wavelength properties." What does that mean and how do you determine if there are measurable wavelength properties?
- Thu Oct 25, 2018 10:56 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: H spectrum
- Replies: 3
- Views: 448
H spectrum
What does it mean that the empirical equation En= -hr/n^2 only works for the H spectrum?
- Thu Oct 25, 2018 10:54 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Bohr frequency condition v empirical equation for H atom
- Replies: 1
- Views: 292
Bohr frequency condition v empirical equation for H atom
I'm confused in regard to the connection between the Bohr frequency condition and the empirical equation for H-atom. Do they give you the same solution? The change in energy? And you just use either one depending on what information you're given? Or are they two separate, unconnected formulas?
- Fri Oct 12, 2018 3:35 am
- Forum: Significant Figures
- Topic: sig figs urgent question!
- Replies: 12
- Views: 2200
Re: sig figs urgent question!
Zeros between non zero digits are always significant
- Fri Oct 12, 2018 3:31 am
- Forum: Significant Figures
- Topic: Atlantic Pacific Rule
- Replies: 2
- Views: 1431
Re: Atlantic Pacific Rule
If there's a decimal point, start counting digits from the left starting with the first non-zero digit. If there isn't a decimal point, start counting digits from the right side starting with the first non-zero digit. Just think of a map: Pacific = left, Atlantic = right.
- Fri Oct 12, 2018 3:28 am
- Forum: Empirical & Molecular Formulas
- Topic: F13
- Replies: 3
- Views: 728
F13
F 13 asks for the name of the compound for which we find the empirical and molecular compound. Are we expected to know how to determine the name of compounds given this information? If so, what are the rules for the nomenclature?
- Fri Oct 05, 2018 3:04 am
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: 6th edition: E15
- Replies: 2
- Views: 265
6th edition: E15
E. 15 asks "The molar mass of the metal hydroxide M(OH)2 is 74.10 g*mol-1. What is the molar mass of the sulfide of this metal?"
I'm confused by the term "sulfide" in this question. Is there a typo in the book or can a sulfide refer to something other than the anion of sulfur?
I'm confused by the term "sulfide" in this question. Is there a typo in the book or can a sulfide refer to something other than the anion of sulfur?
- Fri Oct 05, 2018 2:20 am
- Forum: Significant Figures
- Topic: Scientific Notation
- Replies: 7
- Views: 419
Scientific Notation
How do we know when to write solutions using scientific notation? I usually do so as a default but when checking the solutions manual, I noticed that sometimes answers like (for example) .0623 is left just like that and not written as 6.23 * 10^2. Is there a reason for that? Are there specific rules...
- Fri Oct 05, 2018 2:15 am
- Forum: SI Units, Unit Conversions
- Topic: E23 (6th Edition)
- Replies: 4
- Views: 303
Re: E23 (6th Edition)
Yes, you're right. You would only have to use Avagadro's number if it asked you to calculate the number of molecules or formula units as it did in question E21. In this case, the question is just asking for the number of moles so no need to use Avagadro's number.