Search found 30 matches

by Vincent Tse 2B
Mon Mar 20, 2017 12:59 am
Forum: Second Order Reactions
Topic: Pre- equilibrium approach [ENDORSED]
Replies: 3
Views: 555

Re: Pre- equilibrium approach [ENDORSED]

You apply the pre-equilibrium approach when the mechanism has its first step as fast; this will create a "bottleneck" effect which results in a build-up of intermediates. You can then assume the first step reaction to be at an equilibrium, and use it to help you get rid of the intermediate...
by Vincent Tse 2B
Mon Mar 20, 2017 12:58 am
Forum: *Electrophilic Addition
Topic: Drawing the Transition State
Replies: 2
Views: 1023

Re: Drawing the Transition State

Using the reaction's name itself, the first step usually consists of the electrophile forming a bond to the electron source and the bond between the electrophile and its former group being broken; usually 2 bonds being broken in the first step, and, thus, why it is also the slow step.
by Vincent Tse 2B
Mon Mar 20, 2017 12:54 am
Forum: *Constitutional and Geometric Isomers (cis, Z and trans, E)
Topic: Determining cis, z, trans, or e [ENDORSED]
Replies: 3
Views: 1455

Re: Determining cis, z, trans, or e [ENDORSED]

The E/Z naming system is used particularly for naming alkenes, determined by identifying the priority group bonded to the carbons: if the priority groups are on the same side, it is Z; if opposite, it is E. Cis and trans refer to conformations and the direction of substituents in either axial or equ...
by Vincent Tse 2B
Mon Mar 20, 2017 12:50 am
Forum: *Cyclohexanes (Chair, Boat, Geometric Isomers)
Topic: Most stable confirmation? [ENDORSED]
Replies: 4
Views: 2133

Re: Most stable confirmation? [ENDORSED]

The chair conformation of cyclohexane is most stable when the substituents are equatorial as this will minimize steric interactions between the "bulkiness" of the substituents and the H-atoms.
by Vincent Tse 2B
Mon Mar 20, 2017 12:48 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Determining reduction or oxidation
Replies: 4
Views: 703

Re: Determining reduction or oxidation

Typically you'll be given cell reduction potentials for redox reactions. With the values, you determine the oxidizing and reducing power of each reaction for the observed species. For example, the more positive the cell reduction potential is, the stronger the reduction power. The less positive, the...
by Vincent Tse 2B
Sun Mar 19, 2017 2:15 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Ideal gas
Replies: 1
Views: 390

Re: Ideal gas

The values you listed correspond to molar heat capacities and are typically used for solving heat in terms of moles (q = nC(v/p)deltaT). The subscripts V and P stand for either constant volume or pressure: so, Cv reads as molar heat capacity at constant volume and Cp as molar heat capacity at consta...
by Vincent Tse 2B
Fri Mar 17, 2017 12:09 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Winter 2016 Final Question 2A
Replies: 2
Views: 456

Re: Winter 2016 Final Question 2A

You might want to review setting up an ICE chart: since we're dealing with pressure, one would consider the initial partial pressures, the change in partial pressures, and the resulting partial pressures at equilibrium. In this problem, however, we are only given information at equilibrium, so we ca...
by Vincent Tse 2B
Thu Mar 16, 2017 1:05 am
Forum: Balancing Redox Reactions
Topic: Final Exam 2014 - Q3A
Replies: 2
Views: 367

Re: Final Exam 2014 - Q3A

You would want to choose elements that will give you the highest possible voltage by looking at their corresponding half-reactions.

I found this post to be very helpful: viewtopic.php?t=5476

Hope it clarifies things!
by Vincent Tse 2B
Tue Mar 07, 2017 12:54 am
Forum: Student Social/Study Group
Topic: CHEM 14BL - LEC 2 Lab Switch
Replies: 1
Views: 425

CHEM 14BL - LEC 2 Lab Switch

Hello,

Does anyone with Lecture 2 for Chem 14BL with a Tuesday lab section (anytime)--preferably 2I--want to switch for a Wednesday lab section from 8am-10:50am (Lab 2N)?

Please let me know! Thanks.
by Vincent Tse 2B
Thu Mar 02, 2017 9:21 pm
Forum: *Organic Reaction Mechanisms in General
Topic: Exergonic Reaction
Replies: 2
Views: 420

Re: Exergonic Reaction

For reaction profiles, organic chemistry usually uses Gibbs free energy to describe energy changes. For a reaction that has a standard reaction Gibbs free energy < 0, it is the same as calling it an exergonic reaction in which the free energy of the reactants is greater than the products; therefore,...
by Vincent Tse 2B
Thu Mar 02, 2017 9:16 pm
Forum: *Organic Reaction Mechanisms in General
Topic: Substituent
Replies: 1
Views: 363

Re: Substituent

I believe so. You can think of a substituent as an atom (or group of atoms/molecule) that is bonded to one of the carbons of the longest carbon chain.
by Vincent Tse 2B
Fri Feb 03, 2017 12:10 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Entropy
Replies: 2
Views: 417

Re: Entropy

At constant pressure, the change in enthalpy will be equivalent to heat (qp).
by Vincent Tse 2B
Fri Feb 03, 2017 11:40 am
Forum: Balancing Redox Reactions
Topic: Balancing for E
Replies: 2
Views: 343

Re: Balancing for E

Typically, balancing a redox reaction ensures that you are accounting for the correct amount of electrons being transferred from one species to another. It is this movement of electrons that generates the energy used for work in terms of voltage (in this case, emf or E). When calculating this availa...
by Vincent Tse 2B
Sun Jan 22, 2017 8:11 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: The Value of R
Replies: 2
Views: 411

Re: The Value of R

It usually depends on the context of the problem and the kind of system you're dealing with. For example, if you're calculating work for a reversible gas expansion, you'll need to know moles, temperature (most likely in kelvins), and the final/initial volumes. Disregarding the volume units--they are...
by Vincent Tse 2B
Sun Jan 22, 2017 3:30 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Entropy and Degeneracy [ENDORSED]
Replies: 1
Views: 240

Re: Entropy and Degeneracy [ENDORSED]

Recall that Entropy (S) --an extensive property that relies on the number of particles--describes the likelihood or probability that the system will be in a particular state. Or, in more common terms, entropy describes how "disordered" a system is. In explaining how "disordered" ...
by Vincent Tse 2B
Fri Jan 20, 2017 11:06 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 8.111 part c [ENDORSED]
Replies: 1
Views: 249

Re: 8.111 part c [ENDORSED]

For chemical reactions, they're best done in a chemical reactor-- typically vessels (e.g. a tank) and you can think of reactors as the system for reactions. Reactors are used because they help maximize the reaction's output by minimizing the extent of certain variables that could affect the efficien...
by Vincent Tse 2B
Tue Jan 17, 2017 10:02 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Homework 8.29: Need Clarification [ENDORSED]
Replies: 3
Views: 591

Homework 8.29: Need Clarification [ENDORSED]

Hello,

I am unsure about the concept(s) behind the following problem:

8.29
Which molecular substance do you expect to have the
higher molar heat capacity, NO or NO2? Why?

Can someone please explain how to approach and answer this problem?

Thanks!
by Vincent Tse 2B
Sun Jan 15, 2017 11:21 pm
Forum: Phase Changes & Related Calculations
Topic: HW 8.67 [ENDORSED]
Replies: 5
Views: 727

Re: HW 8.67 [ENDORSED]

When you consider water, for example, you have to have an idea of what your desire equation should be.. Since we're working with standard reaction enthalpy and standard enthalpy of formation, we have to remember that the formation of a compound must be created from its elements in their most stable ...
by Vincent Tse 2B
Thu Jan 12, 2017 11:51 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard Reaction Enthalpy and Standard State
Replies: 2
Views: 246

Re: Standard Reaction Enthalpy and Standard State

There exists diatomic molecules that naturally occur in the world because forming a bond with another of the same element could increase stability; e.g. H2, N2, F2, O2, I2, Cl2, Br2. For a substance that contains different elements, I think that you would have to draw lewis structures and consider f...
by Vincent Tse 2B
Tue Jan 10, 2017 10:35 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: delta H and delta Q
Replies: 2
Views: 5395

Re: delta H and delta Q

Since heat is not a state property, it isn't continuous. Therefore, heat can't be differentiated or taken as a difference between an initial and final value of heat. (Refer to p. 14 in Course Reader). On the other hand, enthalpy is a state property and is denoted by ΔH; this means that you can add a...
by Vincent Tse 2B
Mon Nov 28, 2016 7:12 pm
Forum: Polyprotic Acids & Bases
Topic: Ka1 vs Ka2 vs Ka3
Replies: 2
Views: 3985

Re: Ka1 vs Ka2 vs Ka3

Referring to page 158 in the course reader, a neutral species (which is in relations to Ka1) would have a higher acidity constant since it's more readily to give up an H+ as opposed to a negatively charged species (say Ka2) since anions would hold onto the H+ more strongly. Therefore, Ka2 would be s...
by Vincent Tse 2B
Mon Nov 21, 2016 2:24 pm
Forum: Amphoteric Compounds
Topic: Amphiprotic substances
Replies: 2
Views: 548

Re: Amphiprotic substances

If you refer to page 148 in the course reader, there is a diagram that highlights all the amphoteric oxides; it's the diagonal band that closely matches the diagonal band of metalloids.

In case it is too hard to see, the following oxides are amphoteric: BeO, Al2O3, Ga2O3, SnO2, PbO2, Sb2O5.
by Vincent Tse 2B
Mon Nov 14, 2016 8:02 pm
Forum: Naming
Topic: When naming metals...
Replies: 2
Views: 437

Re: When naming metals...

If you refer to page 118 in the course reader, it states that the ending -ate is added to complexes with a negative charge.

In other words, a transition metal complex should have -ate added to the metal ion's name only when the entire complex is negative.

Hopefully this helped!
by Vincent Tse 2B
Mon Nov 07, 2016 10:54 pm
Forum: Naming
Topic: So lost on the naming
Replies: 4
Views: 552

Re: So lost on the naming

I'm not sure what you mean by "latin names" for the transition metals, but we are required to know how to name the ligands that bond with the central metal atom. You can review the table on page 117 for this. In a sense, it's similar to naming anions (e.g. chlorine --> chloride) but--since...
by Vincent Tse 2B
Tue Nov 01, 2016 4:06 pm
Forum: Octet Exceptions
Topic: Lewis Acids and Bases
Replies: 3
Views: 671

Re: Lewis Acids and Bases

A lewis base is any species that donates an e- pair whereas a lewis acid is any species that accepts an e- pair.

You might want to refer to the examples given on pages 85-86 in the course reader as they relate this concept to coordinate covalent bonds.

Hope this helped!
by Vincent Tse 2B
Tue Oct 25, 2016 11:49 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration for Ions
Replies: 4
Views: 497

Re: Electron Configuration for Ions

Since you're trying to find the configuration for I^-2, it should just be [Xe] 6s^1
by Vincent Tse 2B
Thu Oct 20, 2016 11:33 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron configuration for ions [ENDORSED]
Replies: 2
Views: 321

Re: Electron configuration for ions [ENDORSED]

I think the important thing to remember is that the electron configurations for ions require your attention on the addition or subtraction of electrons. For example, if you were to write the configuration for the anion Cl^-, it would be [Ar] and not its neutral config. [Ne] 3s^2 3p^5 since the ion a...
by Vincent Tse 2B
Tue Oct 11, 2016 12:56 pm
Forum: Balancing Chemical Reactions
Topic: Diatomic Molecules
Replies: 4
Views: 1399

Re: Diatomic Molecules

A mnemonic that I often use to identify diatomic molecules is this: "Have No Fear of Ice Cold Beer."

Have = Hydrogen (H2)
No = Nitrogen (N2)
Fear = Fluorine (F2)
Of = Oxygen (O2)
Ice = Iodine (I2)
Cold = Chlorine (Cl2)
Beer = Bromine (Br2)

Hope this helps!
by Vincent Tse 2B
Tue Oct 04, 2016 8:17 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Can Bohr be used as Rydberg?
Replies: 1
Views: 284

Re: Can Bohr be used as Rydberg?

Hey Kira! I think you should become familiarized with both formulas as they each have their own subtle characteristics. While both are used for atomic spectroscopy, Bohr's frequency condition is used to typically calculate the frequency associated with the energy difference between two energy levels...
by Vincent Tse 2B
Fri Sep 30, 2016 1:31 am
Forum: Balancing Chemical Reactions
Topic: Writing Reactions
Replies: 5
Views: 777

Re: Writing Reactions

Hey Lexi! I found this site extremely helpful when I was learning how to write chemical formulas, including the various prefixes, suffixes, and rules for certain elements. It has different sections for different topics (e.g. naming polyatomic ions). Hopefully this is a good resource that will help y...

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