Search found 25 matches

by Richmund Tan 1L
Mon Mar 07, 2016 2:38 pm
Forum: *Cyclohexanes (Chair, Boat, Geometric Isomers)
Topic: Chair conformation
Replies: 2
Views: 317

Re: Chair conformation

Also, don't forget that if there are no substituents, it doesn't matter if the chair is facing either the left or the right. Structurally, they are just the same, though one may look like a mirror image of the other.
by Richmund Tan 1L
Fri Mar 04, 2016 1:55 pm
Forum: *Constitutional and Geometric Isomers (cis, Z and trans, E)
Topic: Identifying Cis/Trans and Z/E Molecules
Replies: 1
Views: 235

Re: Identifying Cis/Trans and Z/E Molecules

Cis/trans are applicable to molecules with double bonds as you cannot rotate double bonds without breaking them. Naming can occur in a multitude of molecules, such as butane. Therefore, you are not just limited to pentene.
by Richmund Tan 1L
Fri Feb 26, 2016 4:16 pm
Forum: *Alkanes
Topic: Cis- versus Trans-
Replies: 2
Views: 229

Re: Cis- versus Trans-

Additionally, cis- and trans- can refer to bonds in 3-dimensional space. If identical bonds are facing in the same direction of the z-axis (given the positive z axis points towards you), the bonds would be considered cis-. However, if one bond points in the positive z direction and the other bond po...
by Richmund Tan 1L
Fri Feb 19, 2016 11:41 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Equilibrium
Replies: 1
Views: 197

Re: Equilibrium

Pseudo equilibrium can be regarded as 'false equilibrium'. In other words, pseudo equilibrium involves intermediates, while the true equilibrium will put the rate constant in terms of the true products and reactants. Pre equilibrium is a method which we use to determine a reaction mechanism. The app...
by Richmund Tan 1L
Fri Feb 12, 2016 3:50 pm
Forum: First Order Reactions
Topic: Units of Reactions. [ENDORSED]
Replies: 5
Views: 366

Re: Units of Reactions. [ENDORSED]

Units of k for a zero order reaction is just M*s^-1 because the Rate = k. There is no concentration that affects the equation. Units of k for a first order reaction is s^-1 because Rate = k[A]. Since there is one concentration value, s^-1 must multiply with M to give us a rate of M*s^-1. Finally, un...
by Richmund Tan 1L
Fri Feb 05, 2016 12:23 pm
Forum: Balancing Redox Reactions
Topic: Balancing with OH
Replies: 1
Views: 144

Re: Balancing with OH

Yes, you can add in the OH in the end. Just make sure to combine the H and OH to make water and then cancel that from both sides of the equation.
by Richmund Tan 1L
Sun Jan 31, 2016 11:23 pm
Forum: Van't Hoff Equation
Topic: Relevance of K in Van't Hoff Equation
Replies: 1
Views: 422

Re: Relevance of K in Van't Hoff Equation

The Van't Hoff Equation is especially useful in relating K, the equilibrium constant, to the standard enthalpy change with regards to the change in temperature. Also, it is helpful in determining how a chemical reaction can change when temperature changes if the enthalpy change is constant.
by Richmund Tan 1L
Wed Jan 27, 2016 3:42 pm
Forum: Administrative Questions and Class Announcements
Topic: Material provided in all Chem 14A/14B quizzes and exams
Replies: 10
Views: 19615

Re: Material provided in all Chem 14A/14B quizzes and exams

Is there a pdf copy of the exact formula sheet with bond enthalpies that will be given on the quiz?
by Richmund Tan 1L
Fri Jan 22, 2016 12:33 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: enthalpy
Replies: 1
Views: 262

Re: enthalpy

q only equals delta H when the reaction is occurring at a constant pressure that involves solids and/or liquids. This is because P times delta V is insignificant due to the constant pressure and the volume of the reactants equals the volume of the products.
by Richmund Tan 1L
Mon Jan 11, 2016 2:43 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy Change for Reactions without bonds breaking/forming
Replies: 2
Views: 185

Re: Enthalpy Change for Reactions without bonds breaking/for

I would say typically no, energy would not be created nor used if bonds are neither broken nor formed and the energy will not change at all due to the Law of Conservation of Energy. However, knowing that this is chemistry, there might be some exception to the rule out there, so if anyone could enlig...
by Richmund Tan 1L
Wed Jan 06, 2016 11:49 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: How do we use the bond Enthalpies to calculate the reaction?
Replies: 1
Views: 242

Re: How do we use the bond Enthalpies to calculate the react

To calculate bond enthalpies we will need to calculate the delta H for the reaction. Since no equation was supplied, I'm not entirely sure what you are asking. However, assuming that you are referring to calculating the bonds formed for C6H6, you will need to draw out the Lewis structure. From there...
by Richmund Tan 1L
Fri Dec 04, 2015 11:49 pm
Forum: Administrative Questions and Class Announcements
Topic: Materials Provided on Final Exam
Replies: 1
Views: 5334

Materials Provided on Final Exam

Dr. Lavelle, Do you have a viewable copy of all the formulas, Ka values, and any other supplementary materials that will be provided on the final exam? This would be very helpful so I will be able to target which formulas I need to memorize that will not appear on the supplementary sheets. Thank you!
by Richmund Tan 1L
Tue Dec 01, 2015 11:01 am
Forum: Air Pollution & Acid Rain
Topic: Reducing Acid Rain
Replies: 4
Views: 1168

Re: Reducing Acid Rain

Additionally, if we are able to reduce our carbon footprint by reducing our dependence on fossil fuels, we can reduce acid rain. That's why it's important for us to be green! If we use renewable energy resources, such a solar, hydroelectric, and wind power, to name a few examples, we will be able to...
by Richmund Tan 1L
Wed Nov 25, 2015 1:40 am
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Using Ka Kb and Kw to find K
Replies: 1
Views: 2612

Re: Using Ka Kb and Kw to find K

Ka is the acid ionization constant, and Kb is the base ionization constant. They can be likened to either the Lewis or Bronsted-Lowry definitions of acid/base. I assume that when you state "K", you are referring to "Keq/Kp". There really is no Keq/Kp for acid/base questions. You'...
by Richmund Tan 1L
Tue Nov 17, 2015 2:44 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Module Survey Question
Replies: 1
Views: 126

Module Survey Question

Hello, I had a question regarding this problem: 10. What is the equilibrium constant expression, K, for the balanced chemical equation: A ⇌ 2 B A. K = [A]/2[B] B. K = [A][B] 2 C. K = [A] / [B] 2 D. K = [B] 2 / [A] E. None of the above I understand that that correct answer could be D, but if it does ...
by Richmund Tan 1L
Tue Nov 10, 2015 1:18 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Cutoff for determining when to assume "small enough"
Replies: 2
Views: 259

Cutoff for determining when to assume "small enough"

Hi guys, On Monday's lecture, the Professor discussed that when Kp is small enough, we can assume that the -x value is trivial, and thus, we can ignore it, letting us avoid the cubic equation. Does anyone know what the threshold value is for Kp to be considered "small enough"? Thanks in ad...
by Richmund Tan 1L
Fri Nov 06, 2015 11:26 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kp Units
Replies: 1
Views: 311

Kp Units

Hi guys!

When calculating the Kp value, specifically for gases, I noticed that our Professor would use atm. Does anyone know if other units are appropriate, such as torr or mg Hg, or must we always convert to atm before calculating Kp?
by Richmund Tan 1L
Tue Nov 03, 2015 11:37 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: H-F Diagram
Replies: 4
Views: 1149

Re: H-F Diagram

Thanks Jonathan! This is very helpful!
Do you have a strong background in chemistry because this is excellent!

Jonathan Shih 1A wrote:Here it is attached in the image!Image
by Richmund Tan 1L
Sat Oct 31, 2015 6:51 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: H-F Diagram
Replies: 4
Views: 1149

H-F Diagram

Hi guys,

While I was practicing MO diagrams, I came across Hydrogen Fluoride (HF) and I was wondering what the proper MO diagram would be since H only has 1 electron in the 1s orbital. If anyone knows the proper MO diagram, it would be very helpful. Thank you!
by Richmund Tan 1L
Fri Oct 23, 2015 5:04 pm
Forum: Hybridization
Topic: p orbital/ hybridization
Replies: 1
Views: 190

Re: p orbital/ hybridization

Hello there, I believe I can answer your third question. The Pi bonds overlap side by side, and if you recall the diagram Dr. Lavelle drew on the board, these overlapping sides are located on the z axis (if you imagine the board to be the 2-D space that covers x and y, and the 3-D space comes out an...
by Richmund Tan 1L
Fri Oct 16, 2015 11:03 am
Forum: Ionic & Covalent Bonds
Topic: Diatomic Molecules
Replies: 3
Views: 315

Diatomic Molecules

Just to confirm,

Are the following diatomic molecules?
H2
N2
O2
F2
Cl2
Br2
I2
by Richmund Tan 1L
Fri Oct 09, 2015 2:58 pm
Forum: Ionic & Covalent Bonds
Topic: Valence Electrons
Replies: 3
Views: 378

Re: Valence Electrons

I believe that normally you would need to "backwards solve" if you are given a polyatomic ion or molecule and you know the final charge. Even elements like carbon and nitrogen may have different charges than +4 and -3 respectively. In general, group 3 has a +3 charge and group 12 has a +2 ...
by Richmund Tan 1L
Fri Oct 09, 2015 2:52 pm
Forum: Ionic & Covalent Bonds
Topic: Ionic Character and Covalent Character
Replies: 4
Views: 862

Re: Ionic Character and Covalent Character

Also, although we haven't discussed it yet, ionic character and covalent character can be determined by electronegativity. I believe that if the electronegativity is greater than 1.7, it's considered an ionic character. Hopefully we will go more in depth on this topic soon.
by Richmund Tan 1L
Thu Oct 01, 2015 12:52 pm
Forum: DeBroglie Equation
Topic: WavelikeProperty Threshold Value
Replies: 2
Views: 288

Re: WavelikeProperty Threshold Value

Thanks! I also had a follow up question regarding one of the homework problems. For chapter 1 #39, the book asks us to determine the wavelength of a baseball that's 5.15 ounces and 92 mph. I found the answer with the De Brogelie equation to be 1.1x10^-34 m, but since you state the cutoff is 10^-15, ...
by Richmund Tan 1L
Wed Sep 30, 2015 1:02 pm
Forum: DeBroglie Equation
Topic: WavelikeProperty Threshold Value
Replies: 2
Views: 288

WavelikeProperty Threshold Value

Hello, In the lecture today, Dr. Lavelle discussed that an electron has wavelike properties since the wavelength is 10^-12. However the second example with a wavelength of 10^-35 clearly does not have wavelike properties. My question is whether there is a specific value in which an object no longer ...

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