Search found 55 matches

by Dang Lam
Thu Mar 15, 2018 10:57 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: catalysts
Replies: 5
Views: 226

Re: catalysts

Yes, catalyst can appear in the overall rate law, intermediates are the ones that cannot appear in the overall rate law
by Dang Lam
Thu Mar 15, 2018 10:54 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: k' reverse reaction constant
Replies: 6
Views: 306

Re: k' reverse reaction constant

can someone explain to me why K=k/k'?
by Dang Lam
Thu Mar 15, 2018 10:53 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Slow vs Fast Reactions
Replies: 2
Views: 137

Re: Slow vs Fast Reactions

yes we will
by Dang Lam
Thu Mar 08, 2018 4:15 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Finding the intermediate(s)
Replies: 5
Views: 175

Re: Finding the intermediate(s)

Wayland Leung wrote:Why do we not include any intermediates in the overall rate law when the intermediates are a part of the slow step?

From my understanding, we don't include the intermediate in the rate equation because we cancel the it out when we combined the elementary equations to get the overall equation.
by Dang Lam
Thu Mar 08, 2018 4:08 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: 15.17
Replies: 6
Views: 347

Re: 15.17

When we're solving for the order of a reactant in an equation, we usually go about by finding the experiments in the table in which that reactant's concentration changes and where the other reactants are held constant. However, if one of the reactants is independent of the rate, how does this affec...
by Dang Lam
Thu Mar 08, 2018 4:06 pm
Forum: General Rate Laws
Topic: 15.17 type problems
Replies: 4
Views: 198

Re: 15.17 type problems

Yes you can look at the data and tell the order of the reactant but Dr.Lavelle requires some sort of work or explanation in order to receive full credit. You can use the ratio of concentration to rate to show work.
by Dang Lam
Tue Mar 06, 2018 1:02 pm
Forum: General Rate Laws
Topic: Unique Reaction Rates [ENDORSED]
Replies: 32
Views: 61010

Re: Unique Reaction Rates [ENDORSED]

If all of the stoichiometric coefficients were different, the unique rate can still be the same using any of them to calculate it because we are multiplying the (change in concentration/change in time) by 1/coefficient. This therefore allows us to calculate the unique rate using any of the species ...
by Dang Lam
Wed Feb 28, 2018 10:01 pm
Forum: Second Order Reactions
Topic: Question 51 in the homework [ENDORSED]
Replies: 4
Views: 731

Re: Question 51 in the homework [ENDORSED]

Chem_Mod wrote:This is to show that the first step is the most important overall for determining reaction rate, as it is slower than the second, making it rate-limiting.

so which reaction (slow or fast) should we use to write our rate law?
by Dang Lam
Wed Feb 28, 2018 9:55 pm
Forum: Zero Order Reactions
Topic: Units [ENDORSED]
Replies: 7
Views: 901

Re: Units [ENDORSED]

yes because for oth order, the rate law is written as:
rate = k[A]^0
which is equal to rate = k
since the unit for rate = mol/l*s, the unit for k is therefore mol/l*s
by Dang Lam
Wed Feb 28, 2018 9:53 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Determining order
Replies: 1
Views: 104

Determining order

For example 15.2 in the textbook, how did they determine the order of H3O+? Like I am confused with the method they were using with fc and ln. Can someone please explain? Thank you
by Dang Lam
Mon Feb 19, 2018 10:11 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: 14.33 (b)
Replies: 4
Views: 291

Re: 14.33 (b)

You flip the sign of deltaG because the deltaG given is for the formation of Tl3+. The question asks for the standard potential of the Tl3+ /Tl couple, which when written like that indicates that Tl3+ is the reactant and Tl is the product, making it the flipped version of the formation of Tl3+. Tha...
by Dang Lam
Mon Feb 19, 2018 10:10 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: anode?
Replies: 5
Views: 233

Re: anode?

Anode is the one being oxidized. Oxidizing agent is a substance that has the ability to make other substances oxidized, meaning this substance causes the other substances to lose electron.
by Dang Lam
Mon Feb 19, 2018 10:04 pm
Forum: Balancing Redox Reactions
Topic: 14.23 part b
Replies: 1
Views: 145

Re: 14.23 part b

the cathode half reaction is :
2Hg2+ + 2e- --> Hg2 2+
we know Hg2+ is a cathode because it is being reduced (oxidation number decreased from the given equation)
by Dang Lam
Mon Feb 19, 2018 9:58 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Inert conductor
Replies: 2
Views: 92

Inert conductor

How do we know when to include an inert conductor into our cell diagram?
by Dang Lam
Mon Feb 19, 2018 12:15 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: 14.33 (b)
Replies: 4
Views: 291

Re: 14.33 (b)

for part a, why did we have to flip the sign of delta G to negative instead of keeping it positive like given? Also how did they come up with the equation for part a?
by Dang Lam
Mon Feb 12, 2018 11:15 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: delta u [ENDORSED]
Replies: 3
Views: 217

Re: delta u [ENDORSED]

how do you know if delta u =0 though? is it because there is no change is temperature? since deltaU = 3/2 R deltaT, and since deltaT = 0, deltaU is therefore =0 as well?
by Dang Lam
Mon Feb 12, 2018 11:11 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Degeneracy (W) [ENDORSED]
Replies: 8
Views: 470

Re: Degeneracy (W) [ENDORSED]

I have seen some problems in which W also sometimes is calculated using Avogadro's number. When would this be the case instead of doing 2^molecules in the system? When you have n moles. Using a similar example I did in class: 4 moles of CO would have a residual entropy of: S = k ln W where W = 2 4 ...
by Dang Lam
Mon Feb 12, 2018 11:09 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: entropy of vaporization of water [ENDORSED]
Replies: 3
Views: 294

Re: entropy of vaporization of water [ENDORSED]

to elaborate on that, given that enthalpy is a state function, we don't care about the path taken. Regardless, we will get the same answer if we take the final state - initial state. Therefore, this idea allows us to calculate enthalpy of h2o vaporization through multiple steps.
by Dang Lam
Mon Feb 12, 2018 11:02 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Entropy [ENDORSED]
Replies: 5
Views: 303

Re: Entropy [ENDORSED]

can you elaborate on why entropy increases when molecules are broken down please?
by Dang Lam
Wed Feb 07, 2018 9:47 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: deltaS question
Replies: 7
Views: 264

Re: deltaS question

Yes, Cp is use for ideal gas only!!!
by Dang Lam
Wed Feb 07, 2018 9:46 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 9.13
Replies: 6
Views: 226

Re: 9.13

there's an error in the solution manual. You should be using Cv :)
by Dang Lam
Wed Feb 07, 2018 9:44 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Homework 9.19 [ENDORSED]
Replies: 5
Views: 447

Homework 9.19 [ENDORSED]

Calculate the standard entropy of vaporization of water at 85 C, given that its standard entropy of vaporization at 100. C is 109.0 J K 1 mol 1 and the molar heat capacities at constant pressure of liquid water and water vapor are 75.3 J K 1 mol 1 and 33.6 J K 1 mol 1, respectively, in this range. C...
by Dang Lam
Thu Feb 01, 2018 5:31 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: Perfect Crystal
Replies: 9
Views: 316

Re: Perfect Crystal

Can someone explain why entropy of a "perfect crystal" is 0 (S=0)?
by Dang Lam
Thu Feb 01, 2018 5:30 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: G=H-TS
Replies: 4
Views: 313

Re: G=H-TS

Yes, Dr.Lavelle actually went over all the cases in which delta G can be both positive and negative
by Dang Lam
Thu Feb 01, 2018 5:27 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Why should deltaG=0?
Replies: 4
Views: 381

Re: Why should deltaG=0?

simple words: set delta G=0 to find the Temperature (T) that will make delta G equal 0. Given that, we know that if we increase T, delta G will be smaller and smaller. So anything Temperature that is > then the T you found will give delta G a negative number
by Dang Lam
Tue Jan 23, 2018 11:50 am
Forum: Phase Changes & Related Calculations
Topic: Specific heat capacity
Replies: 3
Views: 167

Re: Specific heat capacity

yes, sub1 would require less heat to raise the temperature than sub2
by Dang Lam
Tue Jan 23, 2018 11:48 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: standard enthalpy of formation
Replies: 3
Views: 133

Re: standard enthalpy of formation

so does this mean that delta Hf is similar to delta Hrxn?
by Dang Lam
Tue Jan 23, 2018 11:46 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Enthalpy
Replies: 2
Views: 122

Re: Enthalpy

it depends on the specific heat capacity. based on your equation, q=mc*deltaT, you would calculate q using the mass (m) of the substance
by Dang Lam
Tue Jan 23, 2018 11:41 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Isolated system
Replies: 8
Views: 292

Re: Isolated system

No you cannot because there is no volume change.
by Dang Lam
Thu Jan 18, 2018 11:12 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hess's Law
Replies: 5
Views: 228

Re: Hess's Law

i don't think it has to do with specific heat.
by Dang Lam
Thu Jan 18, 2018 11:09 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.29 heat capacity
Replies: 3
Views: 130

Re: 8.29 heat capacity

I believe it has to do with the increase in molecular motion and disorder.
by Dang Lam
Thu Jan 18, 2018 11:03 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: enthalpy
Replies: 3
Views: 174

enthalpy

Is delta Hf the same as delta Hrxn?
by Dang Lam
Wed Jan 10, 2018 11:54 pm
Forum: Phase Changes & Related Calculations
Topic: qp=deltaH
Replies: 8
Views: 425

Re: qp=deltaH

I think you should focus mostly on deltaH
by Dang Lam
Wed Jan 10, 2018 11:52 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

Because you are breaking the bonds, meaning energy is required and that mean positive value
by Dang Lam
Wed Jan 10, 2018 11:50 pm
Forum: Phase Changes & Related Calculations
Topic: chapter 8
Replies: 6
Views: 268

Re: chapter 8

Yes, I was very confused when trying to do the homework when I started with number 3 and was completely lost
by Dang Lam
Sun Dec 03, 2017 3:17 pm
Forum: Hybridization
Topic: Clarification on hybridization
Replies: 3
Views: 243

Re: Clarification on hybridization

yes! remember AXE?
A = central atom
X = bonded atom
E = bonded lone pairs
by Dang Lam
Mon Nov 27, 2017 8:03 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordination number [ENDORSED]
Replies: 3
Views: 228

Re: Coordination number [ENDORSED]

although there are other alternative ways to figure out coordination number, I personally think it is easier to draw the lewis structure to avoid careless mistakes
by Dang Lam
Mon Nov 27, 2017 7:59 pm
Forum: Ideal Gases
Topic: Chemical equilibrium [ENDORSED]
Replies: 9
Views: 780

Re: Chemical equilibrium [ENDORSED]

yes, because we are dealing with equilibrium reactions.
by Dang Lam
Mon Nov 27, 2017 7:01 pm
Forum: Lewis Acids & Bases
Topic: Lewis Acids and Bases
Replies: 2
Views: 181

Re: Lewis Acids and Bases

Yes, I think you should study that in case
by Dang Lam
Mon Nov 27, 2017 7:00 pm
Forum: Ideal Gases
Topic: I deal gas law formula
Replies: 3
Views: 380

I deal gas law formula

Can someone explain the formation of the ideal gas law formula?
by Dang Lam
Sat Nov 25, 2017 4:39 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: CH2CHCN geometry
Replies: 3
Views: 3339

Re: CH2CHCN geometry

Is there a different way to draw this structure or that is the only one. Also I noticed that the way the formula is written matched with the drawing so is that like a hint on how to draw a lewis structure for a molecule?
by Dang Lam
Fri Nov 24, 2017 3:04 pm
Forum: Ideal Gases
Topic: Kp and Kc
Replies: 7
Views: 543

Kp and Kc

What is the differences between Kp and Kc? Can someone help?
by Dang Lam
Sat Nov 18, 2017 7:49 pm
Forum: Hybridization
Topic: Why is (CH3)2Be is sp? [ENDORSED]
Replies: 7
Views: 3585

Re: Why is (CH3)2Be is sp? [ENDORSED]

Can you please explain why we can put Be in the middle? thanks
by Dang Lam
Mon Nov 13, 2017 8:33 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: AXE
Replies: 3
Views: 169

Re: AXE

A = central atom
X= an atom bonds to A
E= lone pair on A
by Dang Lam
Mon Nov 13, 2017 8:31 pm
Forum: Hybridization
Topic: Polar/nonpolar [ENDORSED]
Replies: 14
Views: 1426

Re: Polar/nonpolar [ENDORSED]

It has to do with electronegative. A nonpolar bond is a bond arises when the electronegativities of two atom are the same, aka the dipole moment = 0, or they cancels each other out. Polar bond is the opposite of that
by Dang Lam
Mon Nov 13, 2017 8:26 pm
Forum: Hybridization
Topic: sigma/pi bond
Replies: 4
Views: 255

sigma/pi bond

Clarification: So when you have a double bond, the first bond would be consider sigma bond and the second one would be pi bond? For tripple bond, the first one would be sigma and the other two would be pi?
by Dang Lam
Thu Nov 09, 2017 12:30 am
Forum: Lewis Structures
Topic: N2O LEWISH STRUCTURE
Replies: 3
Views: 260

N2O LEWISH STRUCTURE

Can someone show me how to draw the lewis structure for N2O? How do you figure out which structure has the lowest energy?
by Dang Lam
Wed Nov 01, 2017 5:19 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Nodal Plane -Test3
Replies: 2
Views: 196

Nodal Plane -Test3

Are we going to get tested on nodes for test 3?
by Dang Lam
Wed Oct 25, 2017 9:41 pm
Forum: Trends in The Periodic Table
Topic: Electron Affinity and Ionization Energy
Replies: 3
Views: 266

Re: Electron Affinity and Ionization Energy

-Ionization Energy = Energy needed to remove an e-
-Election Affinity = Energy released when an e- is being added
They have the same trend because it takes a lot of energy to remove/add an e- to a stable atom, aka in this case the noble gas.
by Dang Lam
Wed Oct 25, 2017 9:35 pm
Forum: Trends in The Periodic Table
Topic: f-orbitals
Replies: 6
Views: 1410

f-orbitals

Does anyone know when does the "f-orbital"start and can you give an example? thanks
by Dang Lam
Thu Oct 19, 2017 2:21 pm
Forum: Properties of Light
Topic: Formulas [ENDORSED]
Replies: 5
Views: 272

Re: Formulas [ENDORSED]

You can use both equation because one of them is just the derived equation of the other. However, it is better to use the equation E=-hR/n^2 to find the energy of each "n" level then find the ∆E by subtracting the Einitial from the Efinal. From there you can find the wavelength using E=hv....
by Dang Lam
Tue Oct 17, 2017 11:36 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Homework #1.11
Replies: 2
Views: 173

Homework #1.11

The question asks "What is common to the lines within a series (lyman/balmer,etc..) that makes grouping them logical?
by Dang Lam
Wed Oct 11, 2017 3:58 pm
Forum: Properties of Light
Topic: Speed of Light [ENDORSED]
Replies: 8
Views: 453

Re: Speed of Light [ENDORSED]

I prefer to use 2.998x10^8 because it gives a more accurate and precise answer. It's like when we calculated the moles in the previous chapter, we carried all the decimal points until the final answer then we rounded it. But if you feel more comfortable using 3.00x10^8 then it should be fine too. :)
by Dang Lam
Sun Oct 08, 2017 9:19 pm
Forum: Significant Figures
Topic: Significant figures Clarification [ENDORSED]
Replies: 3
Views: 273

Re: Significant figures Clarification [ENDORSED]

What I would do is that I would write down all the digits in the first calculation and carry them all the way down to the final answer. Then I round it
by Dang Lam
Sun Oct 08, 2017 9:17 pm
Forum: Balancing Chemical Reactions
Topic: Balancing Chemical equations too slow... any advice? [ENDORSED]
Replies: 18
Views: 1536

Re: Balancing Chemical equations too slow... any advice? [ENDORSED]

Usually, I skim through the equation and do a quick calculation from each side (reactant and product).

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