Search found 54 matches

by Vincent Chiang 1L
Sat Mar 17, 2018 8:35 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Elementary Reaction
Replies: 2
Views: 214

Re: Elementary Reaction

Most likely for the exam you will be given whether the elementary reaction is fast or slow.
by Vincent Chiang 1L
Sat Mar 17, 2018 8:29 pm
Forum: *Ketones
Topic: Ketones vs Aldehydes
Replies: 2
Views: 320

Re: Ketones vs Aldehydes

Aldehydes' C is bonded to either 1 or 2 H. Ketones' C is bonded to 2 C.
by Vincent Chiang 1L
Sat Mar 17, 2018 3:51 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: A?
Replies: 6
Views: 439

Re: A?

If T increases, k increases, and if k increases, A increases. This should mean that as T increases, A should increase.
by Vincent Chiang 1L
Sun Mar 11, 2018 11:46 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Intermediates
Replies: 3
Views: 129

Re: Intermediates

A compound is an intermediate if it is produced in one step of the reaction and is consumed as a reactant in a later step, but does not appear in the overall reaction. If it appears as one of the reactants at the beginning and later appears as a product in a subsequent step, the compound is instead ...
by Vincent Chiang 1L
Sun Mar 11, 2018 11:43 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Rate constant
Replies: 6
Views: 197

Re: Rate constant

Rate constant is just a constant of proportionality relating how the concentrations of the participants of the reaction relate to the rate of reaction. The rate itself just shows how fast the concentration of one of the participants changes, in units of concentration/pressure per unit time. The rate...
by Vincent Chiang 1L
Sun Mar 11, 2018 11:39 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Intermediates in Rate law
Replies: 3
Views: 236

Re: Intermediates in Rate law

Yes, when writing the overall rate law, you shouldn't include intermediates, only substances that are in the overall reaction.
by Vincent Chiang 1L
Sun Mar 04, 2018 11:26 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: test 2 last Q
Replies: 3
Views: 164

Re: test 2 last Q

What was the question? I'm not in 1I, but I might be able to help if I see the question.
by Vincent Chiang 1L
Sun Mar 04, 2018 11:19 pm
Forum: Balancing Redox Reactions
Topic: Test 2, Q5
Replies: 4
Views: 149

Re: Test 2, Q5

These rankings are not based off the placement of the elements in the periodic table. They are based on the standard reduction potentials of each, given in the table provided on the test. Elements with a stronger reducing power will have a lower reduction potential, therefore; organize them based o...
by Vincent Chiang 1L
Sun Mar 04, 2018 11:15 pm
Forum: Second Order Reactions
Topic: Week 9 HW and test promblems
Replies: 5
Views: 342

Re: Week 9 HW and test promblems

Supposedly everything on the HW is fair game, but I think for the tests themselves, the questions before the Integrated Exercises are enough (at least that's how it has been). The integrated HW should be done for finals prep, however.
by Vincent Chiang 1L
Sun Feb 25, 2018 11:18 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: how to write a cell diagram [ENDORSED]
Replies: 6
Views: 439

Re: how to write a cell diagram [ENDORSED]

My TA said that the order is not always followed that way. For the purpose of this class, I don't think the order will be stressed upon.
by Vincent Chiang 1L
Sun Feb 25, 2018 11:16 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14.13c
Replies: 4
Views: 144

Re: 14.13c

I don't think that matters, as long as you place the right compounds into the right anode or cathode.
by Vincent Chiang 1L
Fri Feb 23, 2018 1:42 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14.13(b)
Replies: 2
Views: 94

14.13(b)

Does the order in which we write the galvanic cell components matter? More specifically, is there a reason why I2(s) is in the third position in the given answer, which is Pt(s) | I-(aq) | I2(s) || Ce4+(aq), Ce3+(aq) | Pt(s) ?
by Vincent Chiang 1L
Mon Feb 19, 2018 8:26 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Acidic vs. Basic
Replies: 2
Views: 120

Re: Acidic vs. Basic

My TA said that the questions on the test won't necessarily be given all in acidic conditions. To find out how many H+, H2O, and OH- to add, you'd have to find the oxidation numbers and charges of both sides of the equation, and then add the necessary ions and water molecules to balance the equation...
by Vincent Chiang 1L
Mon Feb 19, 2018 8:20 am
Forum: Balancing Redox Reactions
Topic: 14.15c
Replies: 2
Views: 135

Re: 14.15c

The KOH is there as a salt bridge to allow for the flow of ions.
by Vincent Chiang 1L
Mon Feb 19, 2018 8:19 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14.15.c
Replies: 2
Views: 120

Re: 14.15.c

The KOH is there as a salt bridge to allow for flow of ions.
by Vincent Chiang 1L
Sun Feb 11, 2018 11:44 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: troutons rule
Replies: 3
Views: 176

Re: troutons rule

Exercise 9.17 (which is on Trouton's Rule) is skipped on the outline, so I don't think so.
by Vincent Chiang 1L
Sun Feb 11, 2018 10:29 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Maximum Potential
Replies: 2
Views: 112

Re: Maximum Potential

Max potential of a cell is the maximum potential difference between two half cells in an electrochemical cell.
by Vincent Chiang 1L
Sun Feb 04, 2018 11:28 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 9.19
Replies: 2
Views: 92

Re: 9.19

The first step is to heat the reactants to 100 degrees Celsius using the formula delta S = C(P,m)*ln(T2/T1).
by Vincent Chiang 1L
Sun Feb 04, 2018 9:35 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Equations
Replies: 2
Views: 127

Re: Equations

I'd say your best bet is to familiarize yourself with the Constants and Equations sheet, since that'll be given to us on the test. As for which equations are used in a given circumstances, practicing questions helps the most.
by Vincent Chiang 1L
Sun Feb 04, 2018 8:06 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: 9.35
Replies: 2
Views: 106

Re: 9.35

Container A's change in entropy is higher than that of Container C since Container A's monatomic particles have greater disorder than Container C's diatomic molecules. Complexity of the molecules are important, but in this question's case, we are looking at the rigidity of the structure.
by Vincent Chiang 1L
Sun Jan 28, 2018 10:11 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: Reversible and Irreversible Pathways
Replies: 4
Views: 169

Re: Reversible and Irreversible Pathways

I believe in irreversible, the pressure is changed immediately, whereas in reversible, the pressure is changed slowly.
by Vincent Chiang 1L
Fri Jan 26, 2018 12:38 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Exercise 8.45
Replies: 1
Views: 105

Exercise 8.45

For part a, the SSM shows that to find change in H, we should multiply 1.25 mol by 358.8 kJ/mol. However, the book gives us that the change in enthalpy is 358.8 kJ. Why are the two units different?
by Vincent Chiang 1L
Thu Jan 25, 2018 10:44 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 8.31
Replies: 5
Views: 223

Re: 8.31

On the same question but regarding units, can molar heat capacity be J/(mol.C)? It thought it had to be J/(mol.K)...
by Vincent Chiang 1L
Sun Jan 21, 2018 9:52 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.67 gas to liquid
Replies: 2
Views: 103

Re: 8.67 gas to liquid

Endothermic reactions have a positive change in enthalpy, and exothermic reactions have a negative change in enthalpy. Because a gas to liquid change is exothermic, the change in enthalpy is negative.
by Vincent Chiang 1L
Sun Jan 21, 2018 9:42 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.67
Replies: 2
Views: 150

Re: 8.67

If I'm understanding your question correctly, the value of the standard enthalpy of sublimation of carbon is, it's +717 kJ*mol^(-1), which was written in the question. If I didn't interpret your question correctly, can you clarify the question?
by Vincent Chiang 1L
Sun Jan 21, 2018 9:37 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Homework 8.85
Replies: 1
Views: 88

Re: Homework 8.85

I think it will be tested, since Professor Lavelle put that topic on the outline.
by Vincent Chiang 1L
Sun Jan 14, 2018 10:57 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Closed Versus Isolated System
Replies: 3
Views: 162

Re: Closed Versus Isolated System

Although both systems' matter do not have contact with the environment an thus cannot exchange matter, a closed system is one in which the matter can exchange energy with the environment, whereas an isolated system is one in which the matter cannot exchange energy with the environment.
by Vincent Chiang 1L
Sun Jan 14, 2018 10:48 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 8.5
Replies: 2
Views: 129

Re: 8.5

In this question's case, yes. In general, the change in internal energy can be found by adding the two energies, while paying attention to the signs on the energy changes.
by Vincent Chiang 1L
Sun Jan 14, 2018 10:45 pm
Forum: Phase Changes & Related Calculations
Topic: Good hw questions to practice?
Replies: 2
Views: 142

Re: Good hw questions to practice?

Not sure if this will help, but Section 8.8 is where enthalpy questions start, which is what we started going over in class. So I guess 8.29 and on?
by Vincent Chiang 1L
Sat Dec 09, 2017 11:02 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Test 4 #6
Replies: 1
Views: 214

Test 4 #6

After configuring the ICE box and then solving for x, I eventually arrive at x = 2.40, 2.6. Why does x have to be 2.4, and why can't it be 2.6?
by Vincent Chiang 1L
Sat Dec 09, 2017 9:34 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Lewis Structures of Compounds with Ligands
Replies: 1
Views: 117

Lewis Structures of Compounds with Ligands

When drawing Lewis structures of compounds with ligands, do we need to draw in each ligand's valence electrons?
by Vincent Chiang 1L
Sat Dec 09, 2017 9:31 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Naming of coordination compounds
Replies: 1
Views: 149

Re: Naming of coordination compounds

When there is an overall charge that is not zero in the compound.
by Vincent Chiang 1L
Thu Dec 07, 2017 8:25 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: 12.55(a)
Replies: 1
Views: 90

12.55(a)

Why does (x^2)/([Molarity of CH3COOH] - x) round to (x^2)/[Molarity of CH3COOH]?
by Vincent Chiang 1L
Wed Dec 06, 2017 4:06 pm
Forum: Amphoteric Compounds
Topic: Bi2O5 vs Bi2O3 [ENDORSED]
Replies: 2
Views: 473

Bi2O5 vs Bi2O3 [ENDORSED]

On exercise 12.17 d, Bi2O3 is listed as an amphoteric oxide in the SSM. However, as an oxide, Bi is listed as an acidic oxide on Professor Lavelle's lecture notes (the periodic table of oxide figure). Why do the two differ? Does it have something to do with the number of O bonded to the Bi?
by Vincent Chiang 1L
Thu Nov 30, 2017 12:37 am
Forum: Sigma & Pi Bonds
Topic: Sigma and Pi bonds
Replies: 5
Views: 320

Re: Sigma and Pi bonds

Sigma bonds occur when two orbitals, each with 1 electron, overlap end to end to form 1 sigma bond. They allow bound atoms to rotate. Pi bonds occur when two orbitals, each with 1 electron, overlap side by side to form 1 pi bond. Unlike sigma bonds, pi bonds do not allow bound atoms to rotate. When ...
by Vincent Chiang 1L
Thu Nov 30, 2017 12:30 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: EDTA and Bonding Sites [ENDORSED]
Replies: 5
Views: 359

Re: EDTA and Bonding Sites [ENDORSED]

Oops, I'm sorry I meant ligand.
by Vincent Chiang 1L
Wed Nov 29, 2017 12:10 am
Forum: Ideal Gases
Topic: Pascal vs Atmosphere
Replies: 3
Views: 332

Re: Pascal vs Atmosphere

Lavelle uses atm for the purposes of Chem 14A (at least it says so in his course reader).
by Vincent Chiang 1L
Sun Nov 26, 2017 11:34 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: EDTA and Bonding Sites [ENDORSED]
Replies: 5
Views: 359

Re: EDTA and Bonding Sites [ENDORSED]

EDTA is a ligate, so it has 4 binding sites with oxygen and 2 binding sites with nitrogen.
by Vincent Chiang 1L
Sun Nov 26, 2017 11:28 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Determining Molecular Shape
Replies: 3
Views: 164

Re: Determining Molecular Shape

They all should have the same number of each atoms, so I'm pretty sure you can use any, unless I'm not understanding your question right?
by Vincent Chiang 1L
Mon Nov 20, 2017 12:21 am
Forum: Hybridization
Topic: Sigma Bond
Replies: 3
Views: 208

Re: Sigma Bond

There could be more than one sigma bond, but for the purposes of this class, I'm pretty sure we only have to be concerned with the fact that there is usually only one sigma bond (something about how it's hard to draw two orthogonal sigma bonds?).
by Vincent Chiang 1L
Mon Nov 20, 2017 12:06 am
Forum: Lewis Structures
Topic: Organic Lewis Structures
Replies: 2
Views: 166

Re: Organic Lewis Structures

When I asked my TA, he said that it was intentional that Lavelle labeled the molecule as HOCO as a hint? Generally, it could be written as CHO2.
by Vincent Chiang 1L
Sun Nov 12, 2017 11:41 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Book Questions 4.1&4.2
Replies: 4
Views: 139

Re: Book Questions 4.1&4.2

I think it depends on the bond angles? For example, for part a on the first question, the molecule has a bond angle of 120, which should mean a trigonal planar, or basically 3 electron domains around the central atom. The diagram only shows 2 bonded pairs (which would otherwise be bond angle 180) s...
by Vincent Chiang 1L
Sun Nov 12, 2017 11:37 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Drawing VSEPR Models
Replies: 2
Views: 121

Drawing VSEPR Models

Can someone explain to me what the dashed lines and/or solid triangles between two atoms signify, and when to draw them? Thanks in advance.
by Vincent Chiang 1L
Mon Nov 06, 2017 8:43 pm
Forum: Quantum Numbers and The H-Atom
Topic: Spin Quantum Number Question
Replies: 2
Views: 169

Spin Quantum Number Question

The following question was presented: "Copper is an interesting element as it has 10 elections in its 3d subshell and only one in its 4s subshell. What are the quantum numbers (n and l) that are associated with this last 3d^10 electron? Also, write all the possible values that a spin quantum nu...
by Vincent Chiang 1L
Mon Nov 06, 2017 8:37 pm
Forum: Trends in The Periodic Table
Topic: Electron Affinity - P, Na, Ar
Replies: 4
Views: 245

Re: Electron Affinity - P, Na, Ar

According to my TA, noble gases have very low electron affinities.
by Vincent Chiang 1L
Sun Oct 29, 2017 5:04 pm
Forum: Resonance Structures
Topic: Delocalized
Replies: 7
Views: 417

Re: Delocalized

The example of benzene in lecture shows an example of the electrons involved in multiple bonds, as the structure shows a dotted circle within the carbon ring.
by Vincent Chiang 1L
Sun Oct 29, 2017 4:56 pm
Forum: Lewis Structures
Topic: Sulfate Ion
Replies: 4
Views: 198

Sulfate Ion

When you draw the sulfate ion (SO4)^2-, how can the sulfur share six electrons and have a total of 12? I thought the max was 8... Thanks in advance.
by Vincent Chiang 1L
Sun Oct 22, 2017 11:14 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Paired & Parallel Configurations
Replies: 2
Views: 146

Paired & Parallel Configurations

Can someone explain to me what it means when Lavelle says that paired electrons have opposite spins and parallel electrons have the same spins? I'm trying to visualize it but it's hard picture.
by Vincent Chiang 1L
Sun Oct 22, 2017 11:03 pm
Forum: Properties of Electrons
Topic: Rydberg Equation [ENDORSED]
Replies: 6
Views: 394

Rydberg Equation [ENDORSED]

In the Rydberg equation, does (n1)^2 always have to be the lower energy level? Or can it be the first given energy level (for example if the problem says it went from energy level n = 4 to n = 2, can n1 be 4)?
by Vincent Chiang 1L
Fri Oct 13, 2017 12:33 am
Forum: Properties of Light
Topic: Exercise 1.9 Sig Fig
Replies: 3
Views: 206

Exercise 1.9 Sig Fig

Based on the SSM, for the second row in the table, why don't the number of sig figs match? 5.0E14 Hz is 2 sig figs, and 600 nm is 1 sig fig... Thanks in advance.
by Vincent Chiang 1L
Fri Oct 13, 2017 12:18 am
Forum: Properties of Electrons
Topic: Energy Levels [ENDORSED]
Replies: 2
Views: 223

Energy Levels [ENDORSED]

In discussion we discussed energy levels and changes in energy (delta E), absorption, and emission. We were told that E (photon) = delta E. I understand that absorption of photons results in increased energy levels (n), with delta E being positive. I was curious, in emission, since photons are eject...
by Vincent Chiang 1L
Thu Oct 05, 2017 7:52 pm
Forum: Empirical & Molecular Formulas
Topic: Caproic Acid Question
Replies: 1
Views: 1093

Caproic Acid Question

Caproic acid is composed of C, H, and O. 0.225 g of this sample is combusted. 0.512 g of CO2 is produced. 0.209 g of H2O is produced. What is the empirical formula? This question was given during discussion section. I found how many moles of each product were produced (both were 0.0116 mol), but I d...
by Vincent Chiang 1L
Mon Oct 02, 2017 9:11 pm
Forum: Balancing Chemical Reactions
Topic: States of Matter in Chemical Equations
Replies: 4
Views: 282

States of Matter in Chemical Equations

May seem like a silly question, but I noticed during lecture notes that every time the professor displayed a chemical equation, he'd always have each molecule's state of matter in parentheses. Is it incorrect to write a chemical equation without writing the states of matter? Thanks in advance.

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