Search found 51 matches
- Sat Mar 17, 2018 12:33 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Oxidation power
- Replies: 1
- Views: 244
Oxidation power
For question 5 in test 2, I'm still confused about what oxidation power means. If the standard cell potential of a reduction half reaction is very positive (ex: F2 + 2e --- 2F- E=+2.87), the book says that the oxidized form is strongly oxidizing. Does that mean that on the test when it gave us the r...
- Tue Mar 13, 2018 11:04 pm
- Forum: *Enzyme Kinetics
- Topic: Frequency factor A
- Replies: 1
- Views: 389
Frequency factor A
In collisions, what is the frequency factor A?
Thank you!
Thank you!
- Tue Mar 13, 2018 9:05 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: catalysts and intermediates
- Replies: 2
- Views: 449
catalysts and intermediates
In a multi-step reaction, how can you tell which of the reactants and products that cancel out are catalysts instead of intermediates?
- Sun Mar 11, 2018 10:36 pm
- Forum: Calculating Work of Expansion
- Topic: Midterm Q3B
- Replies: 7
- Views: 1040
Midterm Q3B
Could you explain your thought process for 3b, involving comparing the energy efficiencies of the pots?
I thought that aluminum pots would be more energy efficient because their heat capacity values are the smallest!
Thank you!
I thought that aluminum pots would be more energy efficient because their heat capacity values are the smallest!
Thank you!
- Sun Mar 11, 2018 10:28 pm
- Forum: Calculating Work of Expansion
- Topic: Midterm 4a
- Replies: 4
- Views: 651
Re: Midterm 4a
I think it's because a constant external pressure is characteristic of an irreversible process, and the pressures of the system vs surroundings being at equilibrium is characteristic of a reversible process.
- Fri Mar 09, 2018 12:23 pm
- Forum: Second Order Reactions
- Topic: Half life of second order reactions
- Replies: 8
- Views: 1338
Re: Half life of second order reactions
I was a little confused too seeing that in the table, but I just thought it meant that the book didn't use the half life equation for a second order reaction in one of their examples, or that they just didn't derive the equation for it like they did for the half life of a first order reaction.
- Sun Mar 04, 2018 9:56 pm
- Forum: General Rate Laws
- Topic: Rate equations
- Replies: 3
- Views: 550
Re: Rate equations
we usually don't have to know the derivations!
- Sun Mar 04, 2018 9:52 pm
- Forum: Zero Order Reactions
- Topic: 15.15
- Replies: 3
- Views: 557
Re: 15.15
Hmm is exercise 15.15 a first-order reaction?
- Sun Mar 04, 2018 9:40 pm
- Forum: First Order Reactions
- Topic: half-life
- Replies: 2
- Views: 390
half-life
Why is the half-life of reactant in a first order reaction independent of initial concentration?
Thank you!
Thank you!
- Sun Feb 25, 2018 9:18 pm
- Forum: General Rate Laws
- Topic: Rate law equations
- Replies: 3
- Views: 583
Re: Rate law equations
I think the second one is described as the unique instantaneous rate of a reaction, and the first one as the rate law but they should calculate the same thing!
- Sun Feb 25, 2018 1:37 pm
- Forum: General Rate Laws
- Topic: initial rate law
- Replies: 5
- Views: 614
initial rate law
Is it always only the reactant concentrations that affect the rate law?
Thank you!
Thank you!
- Sun Feb 25, 2018 11:43 am
- Forum: General Rate Laws
- Topic: rate of consumption sign
- Replies: 2
- Views: 430
rate of consumption sign
For exercise 15.3 and 15.5, why isn't the rate of reaction of NO2 and the rate of oxygen consumption negative?
Thank you!
Thank you!
- Sun Feb 18, 2018 8:32 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Work when pressure is constant
- Replies: 6
- Views: 1014
Re: Work when pressure is constant
Does constant pressure only apply to irreversible reactions?
- Sun Feb 18, 2018 8:21 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Galvanic vs. Voltaic
- Replies: 5
- Views: 912
Re: Galvanic vs. Voltaic
Sorry! Is there also a name for the cell that uses the electron current to drive a non-spontaneous reaction?
Thank you!
Thank you!
- Sun Feb 18, 2018 8:17 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Galvanic vs. Voltaic
- Replies: 5
- Views: 912
Galvanic vs. Voltaic
What's the difference between a galvanic and voltaic cell?
Thank you!
Thank you!
- Tue Feb 13, 2018 12:09 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Entropy of system vs surroundings
- Replies: 1
- Views: 400
Entropy of system vs surroundings
For the Gibbs free energy equation, Delta G=delta H-T(delta S), does the change in entropy refer to the entropy of the system, the surroundings, or the total entropy?
Thank you!
Thank you!
- Sat Feb 10, 2018 3:13 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Work
- Replies: 6
- Views: 980
Re: Work
I think doing work means there has to be an opposing force, so a system can't do work in a vaccuum :)
- Sat Feb 10, 2018 3:10 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: isothermal expansion
- Replies: 2
- Views: 385
isothermal expansion
Why is delta U=0 for the isothermal expansion of an ideal gas? (pg 323)
Thank you!
Thank you!
- Mon Feb 05, 2018 8:06 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: question 9.31
- Replies: 1
- Views: 314
question 9.31
For hw question 9.31, Iodine vapor has a higher standard molar entropy than bromine vapor at 298 K. Why does Iodine having a larger mass make it have a larger molar entropy?
- Sun Feb 04, 2018 9:20 pm
- Forum: Phase Changes & Related Calculations
- Topic: enthalpy and entropy when it comes to spontaneous reactions
- Replies: 6
- Views: 777
Re: enthalpy and entropy when it comes to spontaneous reactions
Both affect! Spontaneity depends on whether or not delta G is negative, so I think any combination of positive/negative enthalpy and positive/negative entropy (except when enthalpy is positive and entropy is negative) can produce a spontaneous reaction if it makes delta G negative.
- Sun Feb 04, 2018 9:09 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: thermodynamically favored
- Replies: 6
- Views: 1355
Re: thermodynamically favored
I think the reaction can proceed spontaneously even when delta H is positive, so maybe it just refers to free energy?
- Sun Feb 04, 2018 9:06 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Delta G°
- Replies: 5
- Views: 563
Re: Delta G°
I think another way to say it is when the equilibrium constant equals 1!
- Sun Jan 28, 2018 7:31 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Entropy Change equation
- Replies: 1
- Views: 313
Entropy Change equation
What's the difference between the equation for change in entropy and the equation for heat capacity?
Thank you!
Thank you!
- Sun Jan 28, 2018 6:38 pm
- Forum: Phase Changes & Related Calculations
- Topic: 8.41
- Replies: 6
- Views: 775
Re: 8.41
DamianW wrote:In this problem do you have to account for fusion as well ?
Yes! Since there is a difference in temperature between the ice cube and the water, the ice cube would first melt (enthapy of fusion) and then have a temperature change.
- Sun Jan 28, 2018 6:33 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Work done by Reversible vs. Irreversible Reactions
- Replies: 4
- Views: 665
Re: Work done by Reversible vs. Irreversible Reactions
A reversible process means that the system is at equilibrium, where the pressure of the surroundings and the system are equal. In expansion, a tiny decrease in the surrounding pressure results in a tiny push up by the system on the piston. If expansion continues to occur in very very small steps, we...
- Sun Jan 21, 2018 4:59 pm
- Forum: Phase Changes & Related Calculations
- Topic: Heating curve slope
- Replies: 1
- Views: 441
Heating curve slope
In the heating curve, why is it that the steeper the slope, the lower the heat capacity?
Thank you!
Thank you!
- Sat Jan 20, 2018 10:55 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Textbook Sections 8.7 and 8.10
- Replies: 1
- Views: 193
Re: Textbook Sections 8.7 and 8.10
I was wondering about this as well!
I think that since Professor Lavelle hasn't covered these topics yet in class we should be ok for the exam.
I think that since Professor Lavelle hasn't covered these topics yet in class we should be ok for the exam.
- Sat Jan 20, 2018 8:28 pm
- Forum: Phase Changes & Related Calculations
- Topic: Enthalpy
- Replies: 2
- Views: 349
Enthalpy
For the enthalpy equation: H = U + PV, if change in enthalpy measures the change in heat without work, why is PV added to the internal energy U?
Thank you!
Thank you!
- Fri Jan 12, 2018 9:46 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Molar heat capacity of gas
- Replies: 3
- Views: 328
Molar heat capacity of gas
Could you explain why gas has two values for molar heat capacity?
Thank you!
Thank you!
- Wed Jan 10, 2018 11:28 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Bond Enthalpies
- Replies: 6
- Views: 2357
Re: Bond Enthalpies
Energy is required to break a bond! Like in an endothermic reaction, energy is inputed and so the energy required to break the bonds is positive
- Tue Jan 09, 2018 9:32 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: J vs. KJ [ENDORSED]
- Replies: 2
- Views: 245
J vs. KJ [ENDORSED]
Does it matter if our answer is in J or KJ for this section?
Thank you!
Thank you!
- Wed Dec 06, 2017 11:28 pm
- Forum: Lewis Acids & Bases
- Topic: BF3 [ENDORSED]
- Replies: 2
- Views: 554
BF3 [ENDORSED]
Why is BF3 considered a Lewis acid?
Thank you!
Thank you!
- Wed Dec 06, 2017 11:46 am
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Relative Acidity
- Replies: 3
- Views: 1394
Relative Acidity
For the example Lavelle gave during the lecture, Why is trichloroacetic acid (CCl3OOH, pKa=0.52) a stronger acid than acetic acid (CH3COOH, pKa=4.75)?
Thank you!
Thank you!
- Sun Dec 03, 2017 1:02 am
- Forum: Administrative Questions and Class Announcements
- Topic: Final [ENDORSED]
- Replies: 6
- Views: 1067
Re: Final [ENDORSED]
It could focus on what we learned most recently: acids, bases, salts, chemical equilibrium. And I think that Lewis structures might be another big part since we needed to know how to draw them to answer questions in many of the more recent chapters!
- Wed Nov 29, 2017 4:58 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Seesaw [ENDORSED]
- Replies: 1
- Views: 213
Seesaw [ENDORSED]
What are the angles for a seewsaw molecular shape?
Thank you!
Thank you!
- Tue Nov 21, 2017 3:59 pm
- Forum: Balancing Chemical Reactions
- Topic: states of molecules in reactions
- Replies: 1
- Views: 243
states of molecules in reactions
In a chemical reaction, are we supposed to define the states of the molecules at room temperature or at their state during the reaction? (Ex: H20 is liquid at room temperature but gas after combustion)
Thank you!
Thank you!
- Tue Nov 21, 2017 3:50 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Calculating Equilibrium Constant
- Replies: 2
- Views: 160
Calculating Equilibrium Constant
Why aren't solids included in calculating for the chemical equilibrium constant?
Thank you!
Thank you!
- Wed Nov 15, 2017 8:20 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: trigonal planar vs. t-shaped
- Replies: 5
- Views: 3560
trigonal planar vs. t-shaped
How do you tell if a molecule (with 4 atoms) has a trigonal planar shape or is t-shaped?
- Tue Nov 14, 2017 11:43 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Shape vs. Electron Arrangement
- Replies: 2
- Views: 303
Shape vs. Electron Arrangement
I'm a little confused about the difference between shape and electron arrangement. I know that the shape of the molecule only depends on the bonds/locations of the atoms, and the electron arrangement accounts for lone pairs, but I'm confused about why both types of models are needed.
Thank you!
Thank you!
- Sun Nov 12, 2017 8:47 pm
- Forum: Electronegativity
- Topic: Determine Electron Affinity
- Replies: 2
- Views: 419
Re: Determine Electron Affinity
I think it has to do with Cu being the exception in filling the electron d-block subshells! Because Cu has 10 electrons in the 3d subshell and only 1 electron in the 4s subshell, it would become more stable completing the lone pair in 4s.
- Thu Nov 09, 2017 1:35 pm
- Forum: Lewis Structures
- Topic: NO3- vs NF3 [ENDORSED]
- Replies: 2
- Views: 1669
NO3- vs NF3 [ENDORSED]
How do you tell when to use double bonds and when to just use lone pairs?
NO3- (nitrate ion) has a double bond between N and O, but NF3 has all single bonds and one lone pair.
Thank you!
NO3- (nitrate ion) has a double bond between N and O, but NF3 has all single bonds and one lone pair.
Thank you!
- Sat Nov 04, 2017 3:50 pm
- Forum: Administrative Questions and Class Announcements
- Topic: 14B and 14BL
- Replies: 3
- Views: 430
14B and 14BL
Is it recommended to take Chem 14B and 14BL in the same quarter?
Thank you!
Thank you!
- Thu Nov 02, 2017 12:06 am
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Energy in Orbitals
- Replies: 2
- Views: 281
Energy in Orbitals
Do orbitals on the same energy level or in the same shell (ex; n=3) all have equal amounts of energy?
Thank you!
Thank you!
- Sun Oct 29, 2017 8:02 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: Ionization Energy
- Replies: 3
- Views: 491
Ionization Energy
Why do metals have lower ionization energy?
Thank you!
Thank you!
- Sun Oct 29, 2017 4:23 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: Valence electrons [ENDORSED]
- Replies: 7
- Views: 2604
Valence electrons [ENDORSED]
For elements with 3d and 4s electrons, should the valence electrons include the 3d block as well as the 4s block?
Thank you!
Thank you!
- Thu Oct 19, 2017 1:04 am
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Homework Problem 1.15
- Replies: 4
- Views: 586
Re: Homework Problem 1.15
For the E=-hR/n^2 method!
I kept getting a decimal number too until I tried making the change in energy (calculated from the given wavelength) negative.
I kept getting a decimal number too until I tried making the change in energy (calculated from the given wavelength) negative.
- Wed Oct 18, 2017 9:25 pm
- Forum: Properties of Light
- Topic: Angstrom
- Replies: 3
- Views: 582
Angstrom
Is 1 Angstrom referring to the radius or diameter of an atom?
Thank you!
Thank you!
- Thu Oct 12, 2017 4:07 pm
- Forum: Einstein Equation
- Topic: Einstein
- Replies: 4
- Views: 631
Re: Einstein
I think someone else named them! The book says that Einstein "proposed that electromagnetic radiation consists of particles, which were later called photons."
- Wed Oct 11, 2017 4:06 pm
- Forum: Photoelectric Effect
- Topic: Photoelectric Effect
- Replies: 8
- Views: 806
Photoelectric Effect
For the photoelectric experiment, what is actually happening when light "knocks" electrons off of the metal? I thought that it meant electrons are excited to a higher energy state by photons of a high frequency; however, after reading that electrons can only move to other energy levels wit...
- Fri Oct 06, 2017 11:46 am
- Forum: Balancing Chemical Reactions
- Topic: Diatomic Molecules
- Replies: 3
- Views: 2601
Diatomic Molecules
How would you know which elements exist as diatomic molecules naturally? (Ex: H2, O2)
Thank you!
Thank you!
- Thu Oct 05, 2017 6:20 pm
- Forum: Balancing Chemical Reactions
- Topic: Combustion [ENDORSED]
- Replies: 6
- Views: 1010
Combustion [ENDORSED]
I know combustion reactions require oxygen, but I was just wondering if combustion only occurs if the reactant has both carbon and hydrogen?
Is this reaction in L.7 combustion?
2 C57H110O6 + 163 O2 ->114 CO2 + 110 H2O
Thank you!
Is this reaction in L.7 combustion?
2 C57H110O6 + 163 O2 ->114 CO2 + 110 H2O
Thank you!