Search found 51 matches

by Emma Li 2C
Sat Mar 17, 2018 12:33 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Oxidation power
Replies: 1
Views: 71

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...
by Emma Li 2C
Tue Mar 13, 2018 11:04 pm
Forum: *Enzyme Kinetics
Topic: Frequency factor A
Replies: 1
Views: 181

Frequency factor A

In collisions, what is the frequency factor A?

Thank you!
by Emma Li 2C
Tue Mar 13, 2018 9:05 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: catalysts and intermediates
Replies: 2
Views: 142

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?
by Emma Li 2C
Sun Mar 11, 2018 10:36 pm
Forum: Calculating Work of Expansion
Topic: Midterm Q3B
Replies: 7
Views: 363

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!
by Emma Li 2C
Sun Mar 11, 2018 10:28 pm
Forum: Calculating Work of Expansion
Topic: Midterm 4a
Replies: 4
Views: 246

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.
by Emma Li 2C
Fri Mar 09, 2018 12:23 pm
Forum: Second Order Reactions
Topic: Half life of second order reactions
Replies: 8
Views: 579

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.
by Emma Li 2C
Sun Mar 04, 2018 9:56 pm
Forum: General Rate Laws
Topic: Rate equations
Replies: 3
Views: 159

Re: Rate equations

we usually don't have to know the derivations!
by Emma Li 2C
Sun Mar 04, 2018 9:52 pm
Forum: Zero Order Reactions
Topic: 15.15
Replies: 3
Views: 169

Re: 15.15

Hmm is exercise 15.15 a first-order reaction?
by Emma Li 2C
Sun Mar 04, 2018 9:40 pm
Forum: First Order Reactions
Topic: half-life
Replies: 2
Views: 135

half-life

Why is the half-life of reactant in a first order reaction independent of initial concentration?

Thank you!
by Emma Li 2C
Sun Feb 25, 2018 9:18 pm
Forum: General Rate Laws
Topic: Rate law equations
Replies: 3
Views: 175

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!
by Emma Li 2C
Sun Feb 25, 2018 1:37 pm
Forum: General Rate Laws
Topic: initial rate law
Replies: 5
Views: 169

initial rate law

Is it always only the reactant concentrations that affect the rate law?

Thank you!
by Emma Li 2C
Sun Feb 25, 2018 11:43 am
Forum: General Rate Laws
Topic: rate of consumption sign
Replies: 2
Views: 135

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!
by Emma Li 2C
Sun Feb 18, 2018 8:32 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Work when pressure is constant
Replies: 6
Views: 413

Re: Work when pressure is constant

Does constant pressure only apply to irreversible reactions?
by Emma Li 2C
Sun Feb 18, 2018 8:21 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Galvanic vs. Voltaic
Replies: 5
Views: 150

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!
by Emma Li 2C
Sun Feb 18, 2018 8:17 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Galvanic vs. Voltaic
Replies: 5
Views: 150

Galvanic vs. Voltaic

What's the difference between a galvanic and voltaic cell?

Thank you!
by Emma Li 2C
Tue Feb 13, 2018 12:09 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Entropy of system vs surroundings
Replies: 1
Views: 149

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!
by Emma Li 2C
Sat Feb 10, 2018 3:13 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Work
Replies: 6
Views: 457

Re: Work

I think doing work means there has to be an opposing force, so a system can't do work in a vaccuum :)
by Emma Li 2C
Sat Feb 10, 2018 3:10 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: isothermal expansion
Replies: 2
Views: 121

isothermal expansion

Why is delta U=0 for the isothermal expansion of an ideal gas? (pg 323)

Thank you!
by Emma Li 2C
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: 101

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?
by Emma Li 2C
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: 226

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.
by Emma Li 2C
Sun Feb 04, 2018 9:09 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: thermodynamically favored
Replies: 6
Views: 737

Re: thermodynamically favored

I think the reaction can proceed spontaneously even when delta H is positive, so maybe it just refers to free energy?
by Emma Li 2C
Sun Feb 04, 2018 9:06 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Delta G°
Replies: 5
Views: 158

Re: Delta G°

I think another way to say it is when the equilibrium constant equals 1!
by Emma Li 2C
Sun Jan 28, 2018 7:31 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Entropy Change equation
Replies: 1
Views: 76

Entropy Change equation

What's the difference between the equation for change in entropy and the equation for heat capacity?

Thank you!
by Emma Li 2C
Sun Jan 28, 2018 6:38 pm
Forum: Phase Changes & Related Calculations
Topic: 8.41
Replies: 6
Views: 260

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.
by Emma Li 2C
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: 189

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...
by Emma Li 2C
Sun Jan 21, 2018 4:59 pm
Forum: Phase Changes & Related Calculations
Topic: Heating curve slope
Replies: 1
Views: 99

Heating curve slope

In the heating curve, why is it that the steeper the slope, the lower the heat capacity?

Thank you!
by Emma Li 2C
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: 94

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.
by Emma Li 2C
Sat Jan 20, 2018 8:28 pm
Forum: Phase Changes & Related Calculations
Topic: Enthalpy
Replies: 2
Views: 117

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!
by Emma Li 2C
Fri Jan 12, 2018 9:46 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Molar heat capacity of gas
Replies: 3
Views: 127

Molar heat capacity of gas

Could you explain why gas has two values for molar heat capacity?

Thank you!
by Emma Li 2C
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: 260

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
by Emma Li 2C
Tue Jan 09, 2018 9:32 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: J vs. KJ [ENDORSED]
Replies: 2
Views: 134

J vs. KJ [ENDORSED]

Does it matter if our answer is in J or KJ for this section?

Thank you!
by Emma Li 2C
Wed Dec 06, 2017 11:28 pm
Forum: Lewis Acids & Bases
Topic: BF3 [ENDORSED]
Replies: 2
Views: 197

BF3 [ENDORSED]

Why is BF3 considered a Lewis acid?

Thank you!
by Emma Li 2C
Wed Dec 06, 2017 11:46 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Relative Acidity
Replies: 3
Views: 256

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!
by Emma Li 2C
Sun Dec 03, 2017 1:02 am
Forum: Administrative Questions and Class Announcements
Topic: Final [ENDORSED]
Replies: 6
Views: 516

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!
by Emma Li 2C
Wed Nov 29, 2017 4:58 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Seesaw [ENDORSED]
Replies: 1
Views: 107

Seesaw [ENDORSED]

What are the angles for a seewsaw molecular shape?

Thank you!
by Emma Li 2C
Tue Nov 21, 2017 3:59 pm
Forum: Balancing Chemical Reactions
Topic: states of molecules in reactions
Replies: 1
Views: 146

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!
by Emma Li 2C
Tue Nov 21, 2017 3:50 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Calculating Equilibrium Constant
Replies: 2
Views: 90

Calculating Equilibrium Constant

Why aren't solids included in calculating for the chemical equilibrium constant?

Thank you!
by Emma Li 2C
Wed Nov 15, 2017 8:20 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: trigonal planar vs. t-shaped
Replies: 5
Views: 575

trigonal planar vs. t-shaped

How do you tell if a molecule (with 4 atoms) has a trigonal planar shape or is t-shaped?
by Emma Li 2C
Tue Nov 14, 2017 11:43 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Shape vs. Electron Arrangement
Replies: 2
Views: 109

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!
by Emma Li 2C
Sun Nov 12, 2017 8:47 pm
Forum: Electronegativity
Topic: Determine Electron Affinity
Replies: 2
Views: 190

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.
by Emma Li 2C
Thu Nov 09, 2017 1:35 pm
Forum: Lewis Structures
Topic: NO3- vs NF3 [ENDORSED]
Replies: 2
Views: 368

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!
by Emma Li 2C
Sat Nov 04, 2017 3:50 pm
Forum: Administrative Questions and Class Announcements
Topic: 14B and 14BL
Replies: 3
Views: 243

14B and 14BL

Is it recommended to take Chem 14B and 14BL in the same quarter?

Thank you!
by Emma Li 2C
Thu Nov 02, 2017 12:06 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Energy in Orbitals
Replies: 2
Views: 132

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!
by Emma Li 2C
Sun Oct 29, 2017 8:02 pm
Forum: Quantum Numbers and The H-Atom
Topic: Ionization Energy
Replies: 3
Views: 217

Ionization Energy

Why do metals have lower ionization energy?

Thank you!
by Emma Li 2C
Sun Oct 29, 2017 4:23 pm
Forum: Quantum Numbers and The H-Atom
Topic: Valence electrons [ENDORSED]
Replies: 7
Views: 431

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!
by Emma Li 2C
Thu Oct 19, 2017 1:04 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Homework Problem 1.15
Replies: 4
Views: 270

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.
by Emma Li 2C
Wed Oct 18, 2017 9:25 pm
Forum: Properties of Light
Topic: Angstrom
Replies: 3
Views: 317

Angstrom

Is 1 Angstrom referring to the radius or diameter of an atom?

Thank you!
by Emma Li 2C
Thu Oct 12, 2017 4:07 pm
Forum: Einstein Equation
Topic: Einstein
Replies: 4
Views: 294

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."
by Emma Li 2C
Wed Oct 11, 2017 4:06 pm
Forum: Photoelectric Effect
Topic: Photoelectric Effect
Replies: 8
Views: 352

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...
by Emma Li 2C
Fri Oct 06, 2017 11:46 am
Forum: Balancing Chemical Reactions
Topic: Diatomic Molecules
Replies: 3
Views: 388

Diatomic Molecules

How would you know which elements exist as diatomic molecules naturally? (Ex: H2, O2)

Thank you!
by Emma Li 2C
Thu Oct 05, 2017 6:20 pm
Forum: Balancing Chemical Reactions
Topic: Combustion [ENDORSED]
Replies: 6
Views: 465

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!

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