Search found 26 matches

by Geoffrey Zhang 3I
Sat Mar 18, 2017 7:05 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Rate Limiting Step
Replies: 2
Views: 288

Re: Rate Limiting Step

It is usually given to us. Otherwise, you can tell by the step that has the larger activation energy. This can be determined by the step that has more bonds that need to be broken/added.
by Geoffrey Zhang 3I
Wed Mar 15, 2017 9:40 pm
Forum: General Science Questions
Topic: Ch 3 in Intro to Organic Chemistry
Replies: 1
Views: 396

Re: Ch 3 in Intro to Organic Chemistry

The most stable form of cyclobutane is the butterfly where 2 carbons are on the same plane and the other two are slightly tilted upwards to decrease the steric strain. This forms kind of a slanted diamond shape. The accepted name is butterfly due to the attached hydrogens resembling the wings.
by Geoffrey Zhang 3I
Fri Mar 10, 2017 7:06 pm
Forum: *Alkanes
Topic: Naming and Line structure 1.10
Replies: 1
Views: 260

Re: Naming and Line structure 1.10

Both seem fine to me. One of the TAs mentioned that in a scenario like this, the question would specify if the answer should include the longest carbon chain or not. If so, 2, 2, 3-trimethylpentane would be the answer.
by Geoffrey Zhang 3I
Fri Mar 03, 2017 9:45 pm
Forum: *Organic Reaction Mechanisms in General
Topic: Section 4.3 problem 4.28
Replies: 1
Views: 222

Re: Section 4.3 problem 4.28

Yes, I believe he expects us to know how to draw out electrophilic additions and bimolecular nucleophilic substitution reactions.
by Geoffrey Zhang 3I
Thu Feb 23, 2017 12:25 am
Forum: General Rate Laws
Topic: Quiz 2 Preparation
Replies: 2
Views: 274

Re: Quiz 2 Preparation

You have to use the integrated rate law for second order reactions. After plugging the values in, you will see that the time it takes are different. I used 1/[A]subscript t = 1/[A]0 + kt
by Geoffrey Zhang 3I
Thu Feb 23, 2017 12:22 am
Forum: *Electrophiles
Topic: Nucleophiles and Electrophiles
Replies: 2
Views: 334

Re: Nucleophiles and Electrophiles

I think the topics elaborate on each other. Just another 2 vocab terms.
by Geoffrey Zhang 3I
Sat Feb 18, 2017 11:18 pm
Forum: First Order Reactions
Topic: fractional reaction order [ENDORSED]
Replies: 2
Views: 513

Re: fractional reaction order [ENDORSED]

Hi,

I'm assuming the concentration of some species don't necessarily have to have a whole number order because it has a particular effect on the reaction rate. The concentration of the molecule can have a 1.5 effect on the reaction rate or 0.5.
by Geoffrey Zhang 3I
Sun Feb 12, 2017 10:02 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagram Symbols
Replies: 4
Views: 435

Cell Diagram Symbols

What is the difference between a comma and a vertical bar? I don't know when to use which when writing a cell diagram. Thank you.
by Geoffrey Zhang 3I
Sat Feb 04, 2017 9:48 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Quiz 1 Preparation Practice Quiz from 2010
Replies: 2
Views: 267

Re: Quiz 1 Preparation Practice Quiz from 2010

Hi, You know that internal energy is U= q+w. So if U decreases by 1763 kJ and it only did 1357 kJ of work, then heat must have been transferred from the system. Another way to do this is algebraicly. You can plug -1763 for U and -1357 for w. Solve for q. Since it will be a negative q answer, that me...
by Geoffrey Zhang 3I
Sat Jan 28, 2017 10:11 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Units for Gibbs free energy
Replies: 1
Views: 217

Re: Units for Gibbs free energy

It should be kJ per mole as in example 9.13 in the book since it's deltaH - (TxDeltaS).
by Geoffrey Zhang 3I
Sat Jan 21, 2017 7:27 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Work is done by the system.... [ENDORSED]
Replies: 1
Views: 250

Re: Work is done by the system.... [ENDORSED]

Yes, when a system does work, it's negative because it is losing energy. Positive when work is done onto the system. I'm not sure if temperature would have anything to do with this, but I could be wrong.
by Geoffrey Zhang 3I
Sat Jan 14, 2017 10:10 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Standard Reaction Enthalpy Property
Replies: 2
Views: 315

Re: Standard Reaction Enthalpy Property

Based off the notes on page 17, I'm pretty sure there isn't much difference except for the fact that standard reaction enthalpy of formation is for one mole of a substance.
by Geoffrey Zhang 3I
Fri Dec 02, 2016 11:40 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: molecular orbital diagram question
Replies: 1
Views: 254

Re: molecular orbital diagram question

For any heterogenous species, you use z < 8, I believe.
by Geoffrey Zhang 3I
Wed Nov 23, 2016 9:05 pm
Forum: Amphoteric Compounds
Topic: Bi2O3
Replies: 1
Views: 373

Re: Bi2O3

Bi2O3 is amphoteric because its next to the diagonal. Also, another way you can look at it is that it can act as an acid or base.
by Geoffrey Zhang 3I
Mon Nov 21, 2016 12:27 am
Forum: Conjugate Acids & Bases
Topic: Chapter 12 Question 1
Replies: 3
Views: 434

Re: Chapter 12 Question 1

A conjugate acid is the acid formed when a base accepts a proton.
A conjugate base is the base formed when an acid donates a proton.

So to find conjugate acids, add a proton or H+ to the molecule
For a) CH3NH2 becomes CH3NH3+

To find conjugate bases, take away a proton
HCO3- becomes CO3 2- charge
by Geoffrey Zhang 3I
Tue Nov 15, 2016 10:36 pm
Forum: Naming
Topic: Naming complexes
Replies: 2
Views: 359

Re: Naming complexes

The (III) stands for a +3 charge on the Nickel. You know this because the overall complex should have a net charge of 0. The pentaammine part (NH3) doesn't need any electrons, but the chloro, which is Chlorine needs 1 more electron to fill its valence. So far we have -1 charge we need to account for...
by Geoffrey Zhang 3I
Wed Nov 09, 2016 10:40 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Molecular Orbital Diagram for HF [ENDORSED]
Replies: 1
Views: 391

Re: Molecular Orbital Diagram for HF [ENDORSED]

You use the molecular orbital diagram for z < 8. HF has a total of 8 valence electrons so you'll get 2 electrons in the sigma 2s orbital, another 2 in the antibonding sigma 2s, another 2 in pi 2px and last 2 in pi 2py. Also remember to draw the orbitals lower for F since it's more electronegative. H...
by Geoffrey Zhang 3I
Wed Nov 02, 2016 10:21 pm
Forum: Sigma & Pi Bonds
Topic: Pi Bonds
Replies: 4
Views: 564

Pi Bonds

Will pi bonds always be in the p orbitals? Are there any other possibilities because I'm having difficulties visualizing it. For example, in the 2014 practice midterm, C and O form pi bonds only in 2p.
by Geoffrey Zhang 3I
Fri Oct 21, 2016 9:13 pm
Forum: Lewis Structures
Topic: Lewis structure for O3 (ozone) [ENDORSED]
Replies: 3
Views: 3854

Re: Lewis structure for O3 (ozone) [ENDORSED]

For your second structure O=O=O the middle oxygen would have ten total electrons.
by Geoffrey Zhang 3I
Fri Oct 21, 2016 9:09 pm
Forum: Ionic & Covalent Bonds
Topic: Homework 3.25 Part C
Replies: 1
Views: 229

Re: Homework 3.25 Part C

For those questions, all I did was write out the elements and their typical charges so Al would have +3 to reach an octet, and then for H it would have -1 to have its octet of 2. then just criss-cross the numbers. So it would look like Al+3 H-1 before. After crossing, it becomes AlH3.
by Geoffrey Zhang 3I
Wed Oct 12, 2016 8:31 pm
Forum: Empirical & Molecular Formulas
Topic: What is the molecular formula of xylitol?
Replies: 2
Views: 502

Re: What is the molecular formula of xylitol?

Hi,

You still need to account for the .378 leftover. 2.378 can be rounded to 2.4, then multiply everything by 5 and you should get C5 H12 O5.
by Geoffrey Zhang 3I
Wed Oct 05, 2016 10:18 am
Forum: DeBroglie Equation
Topic: HW 1.39 Wavelength of baseball [ENDORSED]
Replies: 2
Views: 420

Re: HW 1.39 Wavelength of baseball [ENDORSED]

Hi,

The wavelength of the baseball is so miniscule that you can't see it. Basically, the baseball does move in a sin-wave type trajectory but since that value is so tiny, you can't physically see it. Hope that helps!
by Geoffrey Zhang 3I
Fri Sep 30, 2016 10:02 pm
Forum: Limiting Reactant Calculations
Topic: Limiting Reactant Mole Ratios
Replies: 1
Views: 634

Re: Limiting Reactant Mole Ratios

I didn't really follow your question, but I'll walk through the example you gave. So after you converted to moles (1.87 mol CH4 and 0.4690 mol O2) and balanced your equation, you need to figure out which reactant is your limiting reagent. Based on your balanced equation, you need 2 mol of O2 for eve...
by Geoffrey Zhang 3I
Wed Sep 28, 2016 10:55 pm
Forum: Properties of Light
Topic: Rydberg Formula [ENDORSED]
Replies: 2
Views: 328

Re: Rydberg Formula [ENDORSED]

Hi, I'm pretty sure n1 is initial energy shell and n2 is final energy shell. So in the question, it should state like from n=2 to n=4. n1=2 and n2=4
by Geoffrey Zhang 3I
Sun Sep 25, 2016 4:52 pm
Forum: Administrative Questions and Class Announcements
Topic: Textbooks
Replies: 3
Views: 398

Re: Textbooks

I'm pretty sure the chapter contents will be the same, but the problems might have different numbers. Try comparing the chapter content and problems with someone who has the 6th edition. You should be good with the 5th edition if it's the same material.

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