Search found 52 matches

by Ya Gao
Sun Mar 18, 2018 4:09 pm
Forum: General Rate Laws
Topic: 15.85 Drawing structures for activated complex
Replies: 3
Views: 373

Re: 15.85 Drawing structures for activated complex

The activated complex refers to the transition state. Based on reactants and products as given, the transition state can be figured out (which atom should be linked to which atom etc.)
by Ya Gao
Sun Mar 18, 2018 4:06 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Catalyst and Intermediate
Replies: 7
Views: 379

Re: Catalyst and Intermediate

If a molecule is produced and consumed in the next step, it's an intermediate.
If a molecule appears on the reactant side and the product side, it's a catalyst.
by Ya Gao
Sun Mar 18, 2018 4:03 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat Capacity of Water
Replies: 4
Views: 279

Re: Heat Capacity of Water

Heat capacity of water is high because the hydrogen bonds that make up water are considered strong bonds. They are hard to break.
by Ya Gao
Mon Mar 12, 2018 3:49 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Why is entropy extensive?
Replies: 5
Views: 357

Re: Why is entropy extensive?

Entropy is a extensive property because it depends on the number of moles involved ( involves mass, size )
by Ya Gao
Mon Mar 12, 2018 3:35 pm
Forum: *Enzyme Kinetics
Topic: Catalysts
Replies: 11
Views: 463

Re: Catalysts

Yes, because catalyst lowers the activation energy which works in both the forward and reverse reactions.
by Ya Gao
Thu Mar 08, 2018 7:06 pm
Forum: General Rate Laws
Topic: Stoichiometric coefficients and order
Replies: 5
Views: 228

Re: Stoichiometric coefficients and order

You cannot determine the rate law by justing looking at the balanced equation unless it is an elementary step.
by Ya Gao
Thu Mar 08, 2018 7:05 pm
Forum: General Rate Laws
Topic: Integrated Rate Laws
Replies: 6
Views: 209

Re: Integrated Rate Laws

I would say it will be helpful to know how to derive those equations.
by Ya Gao
Thu Mar 08, 2018 6:58 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Intermediate [ENDORSED]
Replies: 7
Views: 205

Re: Intermediate [ENDORSED]

Intermediate can be determined by looking at the separate steps of a reaction. If one molecule is produced in one step and consumed in the following step, then the molecule can be considered an intermediate.
by Ya Gao
Mon Mar 05, 2018 1:56 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: Units of k
Replies: 8
Views: 283

Re: Units of k

You can calculate the unit of k based on the rule that the rate of reaction has an unchanging unit which is mol*L-1*s-1
by Ya Gao
Mon Mar 05, 2018 1:51 am
Forum: Second Order Reactions
Topic: Half-life of second order reactions
Replies: 2
Views: 100

Re: Half-life of second order reactions

Half life of a second order reaction is dependent on the initial concentration since the the half life equals to 1/k[Ao]
by Ya Gao
Mon Mar 05, 2018 1:46 am
Forum: First Order Reactions
Topic: Half-life of first order reactions
Replies: 3
Views: 135

Re: Half-life of first order reactions

Yes and it not only works for first order reactions. It is the case for all reactions.
by Ya Gao
Sun Feb 25, 2018 11:36 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: The rate of a reaction
Replies: 5
Views: 209

Re: The rate of a reaction

Yes! I think in class, it is put as rate of constant k depends of temperature and activation energy.
by Ya Gao
Sun Feb 25, 2018 11:31 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Dissolving [ENDORSED]
Replies: 3
Views: 146

Re: Dissolving [ENDORSED]

To see if a metal will dissolve in the solution, you need to list out the corresponding cathode and anode reaction. In this way, the overall cell potential can be calculated. If the overall cell potential is positive, then the medal will dissolve in the solution.
by Ya Gao
Sun Feb 25, 2018 11:14 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Cell potential calculation
Replies: 4
Views: 137

Re: Cell potential calculation

There are two ways to calculate the cell potential. 1st: list out the anode and cathode reaction and copy the corresponding cell potential to these two reaction. Cell potential of this reaction equals to cell potential of the cathode reaction minus the cell potential of the anode reaction. 2nd: list...
by Ya Gao
Sun Feb 18, 2018 10:51 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14.37
Replies: 1
Views: 69

14.37

Hey guys, I'm having trouble solving question 14.37a.
Determine the potential of the following cell: Pt(s)|H2 (g. 1.0 bar) | HCl (0.075M)||HCl(1.0 mol\L) |H2(1.0 bar)|Pt(s)
Can someone please tell me how to put in the data. Thanks!
by Ya Gao
Sun Feb 18, 2018 7:27 pm
Forum: Balancing Redox Reactions
Topic: 14.5d
Replies: 2
Views: 117

14.5d

Hey guys, I'm having trouble getting the right answer for question 14.5d. A little clarification would be helpful. Thanks!
P4=H2PO2- + PH3 under basic condition.
by Ya Gao
Mon Feb 12, 2018 3:42 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: practice test 6A&6B
Replies: 1
Views: 71

practice test 6A&6B

The question states that 'We expect a reaction to be spontaneous if it is exothermic at a very low temperature.' I wonder if we need to know the sign of ∆S to figure out if the ∆G is negative.For the next true or false question, it said that We can expect an endothermic reaction to be favorable at a...
by Ya Gao
Mon Feb 12, 2018 12:05 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: delta H
Replies: 4
Views: 134

Re: delta H

Both endothermic and exothermic reactions involve forming bonds but exothermic reactions are favored because even though it is forming bonds, the energy of the products is lower than the energy of the reactants.
by Ya Gao
Mon Feb 12, 2018 12:00 am
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Entropy
Replies: 6
Views: 238

Re: Entropy

Diatomic atoms have more entropy than monatomic molecules because there are more possible states to be occupied and the rotational and vibrational energy contribute to the greater entropy.
by Ya Gao
Sun Feb 11, 2018 7:53 pm
Forum: Administrative Questions and Class Announcements
Topic: Practice Midterm Winter 2018
Replies: 10
Views: 2040

Re: Practice Midterm Winter 2018

Hey, do you know where are the simple answers posted?
by Ya Gao
Sun Feb 04, 2018 7:11 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: standard states
Replies: 3
Views: 130

Re: standard states

I think the standard pressure is 1bar but because 1atm is so close to 1bar, we consider 1atm the standard pressure as well.
by Ya Gao
Sun Feb 04, 2018 7:04 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: delta G
Replies: 3
Views: 106

Re: delta G

I think what you are asking what is the minimum temperature when the reaction is spontaneous? The reason that ∆G is 0 because when ∆G is negative, the reaction is spontaneous, therefore, to figure out the minimum temperature, we set the limit:∆G=0, so any temperature above the limit will have a ∆G a...
by Ya Gao
Thu Feb 01, 2018 12:40 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: ∆S=q/T
Replies: 2
Views: 126

∆S=q/T

Can someone explain why ∆S=q/T=nR ln(V2/V1)? I know that ∆S=klnW2/W1, so does nR equals k then?
by Ya Gao
Mon Jan 29, 2018 1:24 am
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Microstates [ENDORSED]
Replies: 3
Views: 216

Re: Microstates [ENDORSED]

I think the easy way the understand it is the possible arrangement atoms can have under specific environments.
by Ya Gao
Fri Jan 26, 2018 10:31 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: reversible and irreversible reactions
Replies: 4
Views: 132

reversible and irreversible reactions

I'm confused about how can we find out if a reaction is reversible or not. Are we gonna be given information about it?
by Ya Gao
Fri Jan 26, 2018 10:15 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Entropy of gas vs liquid vs solid
Replies: 7
Views: 1388

Re: Entropy of gas vs liquid vs solid

When the molecules are in gas phase, there are many more possible states they can occupy compared to the possible states molecules can occupy when they are in liquid phase or solid phase. With more possible states, the entropy will be higher.
by Ya Gao
Sun Jan 21, 2018 12:26 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.31
Replies: 3
Views: 105

Re: 8.31

It means that when a gas is working as an ideal gas, its Cv and Cp will be 3/2R and 5/2R. It can be found on the equation sheet.
by Ya Gao
Fri Jan 19, 2018 11:24 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: PV=nRT
Replies: 4
Views: 170

Re: PV=nRT

As we know, change in internal energy equals w+q and w=-q*∆V. For gases, when it's under constant pressure and there is a net change in the number of moles, there will be a change in the volume. According to PV=nRT, P∆V=∆nRT. Therefore, when a reaction under constant pressure and has a net change in...
by Ya Gao
Thu Jan 18, 2018 10:16 pm
Forum: Calculating Work of Expansion
Topic: units for calculating work
Replies: 6
Views: 124

Re: units for calculating work

I'll say use liter for volume and atm for pressure.
by Ya Gao
Wed Jan 17, 2018 7:44 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 8.31
Replies: 3
Views: 121

Re: 8.31

Hey, how do you know the molar heat capacity is 5/2R and 3/2R ? Can you explain a little bit?
by Ya Gao
Wed Jan 17, 2018 7:31 pm
Forum: Calculating Work of Expansion
Topic: 8.17 Work done by a system
Replies: 6
Views: 239

Re: 8.17 Work done by a system

Hey, if a work is done by the system, it is considered negative because the system as a whole is losing energy. Since condensation requires energy, work has to be done to the system so that condensation can occur. Hope that helps.
by Ya Gao
Wed Jan 17, 2018 7:24 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Enthalpy Equation
Replies: 3
Views: 184

Re: Enthalpy Equation

Hey, P∆V represents work done to the system. Since w=FxD and F=PxA D (distance) and A (area), we can get the equation w=P ∆V.
Hope it helps.
by Ya Gao
Sun Dec 10, 2017 5:21 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Ligands [ENDORSED]
Replies: 1
Views: 142

Re: Ligands [ENDORSED]

Hey, I believe ligand is what is attached to the transition metal and the coordination complex is the metal with the ligands.
by Ya Gao
Sun Dec 10, 2017 2:47 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: shape [ENDORSED]
Replies: 2
Views: 289

shape [ENDORSED]

Hey guys, on the final there was a question that asks for the shape ( not electron density) of nitrogen atoms.What does the shape mean??
by Ya Gao
Tue Dec 05, 2017 9:25 pm
Forum: Calculating the pH of Salt Solutions
Topic: negative pH
Replies: 2
Views: 263

Re: negative pH

Hey, I think professor Lavelle mentioned in class that solution can have negative pH when it is superacid.... Hope it helps.
by Ya Gao
Tue Dec 05, 2017 9:23 pm
Forum: Lewis Acids & Bases
Topic: 12.29
Replies: 2
Views: 152

Re: 12.29

Hey, there are two hydroxide ion per Ba(OH)2 because if we write out the balanced equation: Ba(OH)2----Ba2+ + 2OH-, for every Ba(OH)2 molecule ionized, two hydroxide ions is produced. That's why you need to multiply it by 2. Hope it helps.
by Ya Gao
Thu Nov 30, 2017 8:23 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: TM cations in solutions
Replies: 2
Views: 171

Re: TM cations in solutions

Hey, I believe in class, professor Lavelle said that species like NH3, NaCl are electron rich, so they will replace H2O ligands and form coordination compounds. Hope it helps.
by Ya Gao
Thu Nov 30, 2017 8:13 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Dipole moments
Replies: 2
Views: 139

Re: Dipole moments

Hey, dipole moment is resulted from an uneven distribution of electrons between atoms. When the electronegativity difference between the atom is big, the dipole moment will be big and when the electronegativity difference is small, the dipole moment will be small. Hope it helps.
by Ya Gao
Tue Nov 21, 2017 11:58 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Homework question 17.33
Replies: 4
Views: 211

Re: Homework question 17.33

For ion CO3 2-, I think it is bidentate because if you draw the lewis structure of it, you will see that two out of the three oxygen have lone pairs around them and do not have a formal charge of 0. So for these two oxygen atoms, they would want to form bonds. For water molecule, if you draw out the...
by Ya Gao
Tue Nov 21, 2017 11:43 am
Forum: Hybridization
Topic: 4.95
Replies: 3
Views: 170

Re: 4.95

The number is related to the number on the periodic table because the number represents which orbital the valence electron is, for example, H1s, the valence electron of hydrogen atom is in the 1s orbital. Hope that helps.
by Ya Gao
Thu Nov 16, 2017 12:31 pm
Forum: Hybridization
Topic: the number of pi bonds
Replies: 3
Views: 166

the number of pi bonds

I have a question about how many pi bonds are formed in benzene. In class, professor Lavelle said that there are three pi bonds formed in benzene because there are three double bonds formed between C-C, but what about the unhybridized 2p electrons, don't they also form pi bonds with each other? Do w...
by Ya Gao
Thu Nov 16, 2017 12:23 pm
Forum: Hybridization
Topic: HW 4.33
Replies: 1
Views: 119

Re: HW 4.33

Yeah, for questions about hybridization, you need to find out the number of electron densities around the central atom by drawing the Lewis structure. After you find out the number of electron density around the central atom, you can figure out the hybridization because regions of electron density e...
by Ya Gao
Sun Nov 12, 2017 5:27 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Tetrahedral vs Trigonal Pyramid
Replies: 2
Views: 190

Re: Tetrahedral vs Trigonal Pyramid

Tetrahedral is when the central atom has only four bonds around it(no lone pairs) and trigonal pyramid is when the central atom has three bonds and one lone pair around it. Hope it helps.
by Ya Gao
Sun Nov 12, 2017 4:22 pm
Forum: Lewis Structures
Topic: atomic structure of HOCO
Replies: 8
Views: 326

Re: atomic structure of HOCO

In these kinds of questions I always assume the way the molecule is written as the way it is bonded.
by Ya Gao
Sun Nov 05, 2017 7:30 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Highly Polarizable
Replies: 4
Views: 287

Re: Highly Polarizable

Hey, highly distorted electron means the electron is loosely held by the atom or ion, therefore it can easily be distorted. Ions that cause large distortions are described as having high polarizing power, in this case, small highly charged ions. Hope it helps.
by Ya Gao
Sun Nov 05, 2017 7:24 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Lewis Structures
Replies: 6
Views: 260

Re: Lewis Structures

I think the 3d diagrams are the actual shape of the electron orbitals because they are based on mathematical equations. Hope it helps.
by Ya Gao
Thu Nov 02, 2017 12:36 am
Forum: Octet Exceptions
Topic: Octet Exceptions
Replies: 4
Views: 213

Re: Octet Exceptions

I think it depends on what the central atoms are. Like we said before, if the central atom is P, S, or Cl, they can have extra electrons around them because they do have a d orbital. And if there are two central atoms, they still have have more electrons depending on what they are. Hope it makes sen...
by Ya Gao
Wed Oct 18, 2017 9:17 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Heisenberg Uncertainty Equation
Replies: 7
Views: 357

Re: Heisenberg Uncertainty Equation

Well, 4pi must have come from some kind of experiment or something. For now, I don't think we are able to understand how scientists derived the specific function, but maybe we will, in the future.
by Ya Gao
Wed Oct 18, 2017 8:56 pm
Forum: Quantum Numbers and The H-Atom
Topic: Quantum Numbers
Replies: 4
Views: 416

Re: Quantum Numbers

To the question about d orbital, 3d orbital comes after 4s orbital. About where different orbitals are, you can refer to the energy level of different orbitals on page 43. About why electron spin is +-1/2, I believe the values are derived from experiment... but exactly why +- 1/2, I have no idea :(
by Ya Gao
Fri Oct 13, 2017 12:43 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: why is Bohr Frequency equation negative
Replies: 4
Views: 430

why is Bohr Frequency equation negative

Can somebody please tell me why there is a negative sign in the equation ∆E=-hR/n2. I didn't quite get that in the class and why n approaches infinity the energy of the electron will be 0? Doesn't it have to receive a ton of energy to be excited to the outer levels?? I'm so confused.
by Ya Gao
Wed Oct 11, 2017 11:23 pm
Forum: Photoelectric Effect
Topic: Photoelectric Effect Module Question 18 [ENDORSED]
Replies: 3
Views: 226

Re: Photoelectric Effect Module Question 18 [ENDORSED]

I think this question is asking for all the conditions that apply to the situation. Since electrons can be ejected when the energy of the photon is equal or greater than the energy needed to remove the electron which is work function, so choice B and C both are correct.
by Ya Gao
Mon Oct 09, 2017 4:49 pm
Forum: Properties of Light
Topic: Amplitude of the wave [ENDORSED]
Replies: 7
Views: 488

Re: Amplitude of the wave [ENDORSED]

So if the amplitude of the light is higher, does the light become brighter?

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