Search found 159 matches

by Se-Young Lee
Sat Mar 15, 2014 7:20 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Control vs Favorable
Replies: 6
Views: 869

Re: Control vs Favorable

Thermodynamic control would be a reaction's ability to go to either reactants or products (reversibility) at certain high temperatures.
by Se-Young Lee
Sat Mar 15, 2014 7:15 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: final 2007 Q6A
Replies: 5
Views: 804

Re: final 2007 Q6A

T is most definitely steric strain-- though we did not learn about Van der Waals interactions, we do have a general sense of its concept: it's the sum of all repulsive or attractive forces between molecules, excluding recognizable interactions such as covalent, ionic, and hydrogen bonding.
by Se-Young Lee
Mon Mar 10, 2014 7:38 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: free energy
Replies: 2
Views: 427

Re: free energy

A real world analogy I like to use, is thinking of free energy as an analog to potential energy, as we learned in class; I, however, like to extend the analogy a bit, and think of various factors that affect, say, a ball dropping from a certain height. In our world, we have something called air resi...
by Se-Young Lee
Mon Mar 10, 2014 7:15 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: End-of-Chapter 13.15 (c) [ENDORSED]
Replies: 4
Views: 641

Re: End-of-Chapter 13.15 (c) [ENDORSED]

Ah, this was incredibly helpful-- thank you professor! In theory, however, (not regarding the price of the metals), would platinum have been a valid, if not a better answer? Obligatory second question: In the cathode, since two (fairly conductible) solids are already in vitro, must we include an add...
by Se-Young Lee
Fri Mar 07, 2014 7:44 pm
Forum: Balancing Redox Reactions
Topic: inert metal
Replies: 2
Views: 495

Re: inert metal

Furthermore, it is generally safe to assume, that inert metals such as platinum are used whenever electron-conducting solids are not present in the reaction (i.e., when the two states of a particular cell (anode or cathode) are both in the aqueous state)
by Se-Young Lee
Fri Mar 07, 2014 4:58 pm
Forum: *Cyclohexanes (Chair, Boat, Geometric Isomers)
Topic: So, I was able to make a boat in Chem3D...
Replies: 2
Views: 1559

Re: So, I was able to make a boat in Chem3D...

Hey, yes-- since the boat conformation isn't stable for cyclohexane, I simply used the "clean up" option under the "structure" menu.
by Se-Young Lee
Thu Mar 06, 2014 11:10 pm
Forum: *Amines
Topic: including (or not including) the 1
Replies: 6
Views: 785

Re: including (or not including) the 1

Third confirmation, 1 can be ignored.
by Se-Young Lee
Thu Mar 06, 2014 11:07 pm
Forum: *Cyclohexanes (Chair, Boat, Geometric Isomers)
Topic: So, I was able to make a boat in Chem3D...
Replies: 2
Views: 1559

So, I was able to make a boat in Chem3D...

I know a lot of you have been confused about some of the last questions in the Organic Chemistry workbook, where it asked to change a cyclohexane in the chair conformation to a cyclohexane in a boat conformation, simply by changing its orientation in space, but this is clearly impossible to do. I'm ...
by Se-Young Lee
Thu Mar 06, 2014 10:59 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: final 2007 3c
Replies: 2
Views: 359

Re: final 2007 3c

Asking whether a system is thermodynamically feasible is the same thing as asking "is this system spontaneous under the given conditions?"-- but of course, 'thermodynamically feasible' (i.e. delta G < 0) does not necessarily mean kinetically feasible, which is the case of a diamond -> grap...
by Se-Young Lee
Thu Mar 06, 2014 10:56 pm
Forum: Administrative Questions and Class Announcements
Topic: *Additional Forum Features*
Replies: 25
Views: 3700

Re: *Additional Forum Features*

Ah! Why haven't I seen that before… thanks ch1995!
by Se-Young Lee
Thu Mar 06, 2014 10:50 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: final 2008 3.
Replies: 4
Views: 577

Re: final 2008 3.

Pb is the anode, Cu is the cathode-- A "Cathode" is the electrode where "Reduction" takes place, and an "Anode" is the electrode where "Oxidation" takes place.
by Se-Young Lee
Thu Mar 06, 2014 10:48 pm
Forum: Administrative Questions and Class Announcements
Topic: *Additional Forum Features*
Replies: 25
Views: 3700

Re: *Additional Forum Features*

On the topic of additional forum features, I think a "bookmark" button would be nice, to save posts that we'd like to view at a later time, or to see answers to posts when more people have viewed and answered the question. Also, as mentioned before, a "resolved" button that tells...
by Se-Young Lee
Wed Mar 05, 2014 8:12 pm
Forum: *Alkanes and Substituted Alkanes (Staggered, Eclipsed, Gauche, Anti, Newman Projections)
Topic: staggered v. eclipsed
Replies: 3
Views: 2174

Re: staggered v. eclipsed

Also note the meaning of dashed and wedged lines-- in the eclipsed molecular structure, each constituent on the first carbon (chlorine, bromine, and hydrogen) is parallel to the like constituents on the other carbon. Of course, just by looking at the line structures alone, it can be quite difficult ...
by Se-Young Lee
Wed Mar 05, 2014 8:03 pm
Forum: Administrative Questions and Class Announcements
Topic: *Additional Forum Features*
Replies: 25
Views: 3700

Re: *Additional Forum Features*

I think it would be interesting to allow images to be uploaded, so that we could draw out certain diagrams or mechanisms for clarification of concepts.
by Se-Young Lee
Wed Mar 05, 2014 7:58 pm
Forum: Second Order Reactions
Topic: Propene and Hydrogen bromide collision
Replies: 7
Views: 1426

Re: Propene and Hydrogen bromide collision

Ah, thank you for this answer! (very helpful)
by Se-Young Lee
Sun Mar 02, 2014 10:27 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: adding water
Replies: 3
Views: 1168

Re: adding water

This is a very good question-- I'd like for Dr. Lavelle to go over this in detail, but as the previous poster mentioned, adding water to concentration cells would alter the molarity of the reactants in question, therefore having an effect on the value of the voltage potential.
by Se-Young Lee
Sun Mar 02, 2014 10:22 pm
Forum: *Nucleophiles
Topic: Identifying the ambident nucleophile
Replies: 2
Views: 954

Re: Identifying the ambident nucleophile

Yes, and furthermore, recall that the term 'ambident nucleophile' refers strictly to anionic nucleophiles whose negative charge is delocalized by resonance over two UNLIKE atoms, and also two LIKE, but unequivalent atoms. This is why in some of the problems that we've encountered, huge structures wi...
by Se-Young Lee
Sun Mar 02, 2014 10:10 pm
Forum: *Nucleophiles
Topic: More lone pairs around the atom/molecule
Replies: 7
Views: 707

Re: More lone pairs around the atom/molecule

Also, it is incredibly difficult to generalize in the fashion you mentioned due to the fact that not all lone pairs of electrons possess equal energies-- for instance, a highly electronegative atom will tend to draw its lone pairs of electrons toward its nucleus, thus keeping electron density high r...
by Se-Young Lee
Sun Mar 02, 2014 10:03 pm
Forum: *Cycloalkenes
Topic: what exactly is meant by "aryl carbocation"?
Replies: 6
Views: 791

Re: what exactly is meant by "aryl carbocation"?

Ah, that's interesting-- so what exactly are the different classes of aromatic rings in existence?
by Se-Young Lee
Sun Mar 02, 2014 5:15 pm
Forum: *Cycloalkenes
Topic: what exactly is meant by "aryl carbocation"?
Replies: 6
Views: 791

what exactly is meant by "aryl carbocation"?

The definition of a carbocation is quite clear, since it is simply a carbon atom with a sp2 hybridized, trigonal planar molecular geometry (due to electron deficiency), but I am not sure about what the term "aryl" refers to.
by Se-Young Lee
Sat Mar 01, 2014 11:20 pm
Forum: Second Order Reactions
Topic: Propene and Hydrogen bromide collision
Replies: 7
Views: 1426

Propene and Hydrogen bromide collision

In the case of the collision between Propene (H3C-CH=CH2) and Hydrogen bromide (H-Br), is the collision always oriented toward the electron-rich pi bond due to the fact that the carbon atoms don't necessarily require additional electrons (as according to formal charges)? Furthermore, why couldn't th...
by Se-Young Lee
Sat Mar 01, 2014 11:12 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Standard cell potential and ionization energy
Replies: 3
Views: 694

Re: Standard cell potential and ionization energy

Somewhat- an atom/species with larger electron affinity/electronegativity will tend to pull electrons with a greater force, hence producing larger reduction potential, but the explanation is actually quite more complicated than simply correlating electron affinities and standard cell potential, sinc...
by Se-Young Lee
Sat Mar 01, 2014 11:04 pm
Forum: *Alkanes
Topic: order
Replies: 2
Views: 332

Re: order

You are correct. The proper name is 1-ethyl 2,4-dimethylcyclohexane.
by Se-Young Lee
Sat Mar 01, 2014 11:01 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Stability and Activation Energy
Replies: 1
Views: 638

Stability and Activation Energy

Would it be a safe assumption to make, that molecular stability is correlated to higher activation energy?
by Se-Young Lee
Sat Mar 01, 2014 11:00 pm
Forum: Experimental Details
Topic: steric factors and speed of the reaction
Replies: 1
Views: 1405

steric factors and speed of the reaction

based on steric factors alone, would it be safe to assume that atomic ions would have greater chances of forming bonds due to larger availability of its electrons, and therefore, produce faster reactions? I would assume that this logic would be consistent with the observation that many acid/base rea...
by Se-Young Lee
Sat Mar 01, 2014 10:55 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: can we find catalysts for all reactions?
Replies: 1
Views: 481

can we find catalysts for all reactions?

Are we able to find catalysts to all reactions, or are there reactions where catalysts are not known/have not been discovered?
by Se-Young Lee
Sun Feb 16, 2014 10:03 pm
Forum: Calculating Work of Expansion
Topic: Methane Combustion Q1B page 226
Replies: 3
Views: 1056

Re: Methane Combustion Q1B page 226

Well, if you combust a lot of gas in a closed room at a temperature below 373.15K, the water vapor will quickly condense to liquid water as it cools down to the ambient temperature. (Recall that heat flows from hot to cold, and that the temperature of a particular system depends on its surroundings,...
by Se-Young Lee
Tue Feb 11, 2014 9:43 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: 13.103
Replies: 3
Views: 492

Re: 13.103

I'm not sure what the question is, but in general, if you take the difference of two standard E values, and get a maximum E cell value, the equation you reversed is the anode.
by Se-Young Lee
Tue Feb 11, 2014 9:29 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: 2012 Midterm Question 3A
Replies: 5
Views: 975

Re: 2012 Midterm Question 3A

Correct me if I'm wrong, but isn't there only ONE position that HBr(g) can be in, since it is linear?


HBr is a hetero-nuclear molecule, and so whether the molecule is bonded like H-Br:, or like :Br-H matters.
by Se-Young Lee
Tue Feb 11, 2014 9:23 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: Degeneracy
Replies: 1
Views: 695

Re: Degeneracy

How would you know the degeneracy of molecules like CH4 or O2 or BH2F? Ah, good question-- "degeneracy" means, in simple terms, "equal energy levels in different states"-- what that means, is take a molecule, like BH2F. Boron will be the central atom, surrounded by three atoms i...
by Se-Young Lee
Tue Feb 11, 2014 12:45 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: Question about 8.79
Replies: 1
Views: 1009

Re: Question about 8.79

8.79 Suppose that you create two tiny systems consisting of three atoms each, and each atom can accept energy in quanta of the same magnitude. (a) How many distinguishable arrangements are there of two quanta of energy distributed among the three atoms in one of these systems? (b) You now bring the...
by Se-Young Lee
Tue Feb 11, 2014 12:33 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Equilibrium Constant hw 10.85
Replies: 2
Views: 490

Re: Equilibrium Constant hw 10.85

To clarify the earlier answer, a large value of K (K>1) implies that the concentration of products is greater than that of the reactants. A small value of K (K<1) implies that the concentration of the reactants is greater than that of the products. If the problems gives you that at 600K, K = 1.7x10^...
by Se-Young Lee
Tue Feb 11, 2014 12:16 pm
Forum: Calculating Work of Expansion
Topic: Isothermal Expansion Against Vacuum
Replies: 2
Views: 535

Re: Isothermal Expansion Against Vacuum

Think about it this way: temperature is defined as the measure of the average kinetic energies of the molecules in a system. Heat flow, is the change in the kinetic energies of the molecules, or the temperatures of two systems in contact. A vacuum has no molecules by definition, so it would be impos...
by Se-Young Lee
Tue Feb 11, 2014 12:14 pm
Forum: Calculating Work of Expansion
Topic: Methane Combustion Q1B page 226
Replies: 3
Views: 1056

Re: Methane Combustion Q1B page 226

The question in the course reader asks to calculate the work done due to the irreversible expansion of methane gas when combusted. However, in the given solution, the balanced combustion equation puts water in a liquid phase thus making delta n = -2 instead of 0. How am I supposed know when to make...
by Se-Young Lee
Tue Feb 11, 2014 1:29 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: boiling point of methanol
Replies: 3
Views: 1018

Re: boiling point of methanol

Thank you for the link! Unfortunately, I've been unable to find explanation for a lower boiling point despite predicted high boiling due to strong bonds--
by Se-Young Lee
Mon Feb 10, 2014 11:43 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: boiling point of methanol
Replies: 3
Views: 1018

boiling point of methanol

I encountered an issue while looking at the appendix: methanol, CH3OH, is able to form hydrogen bonds, which in theory should raise its boiling point higher than that predicted by Trouton's rule-- and yet it's lower. Could anyone explain why?
by Se-Young Lee
Sat Feb 08, 2014 7:19 pm
Forum: Balancing Redox Reactions
Topic: 13.3 a) Error
Replies: 4
Views: 620

Re: 13.3 a) Error

With the 8 electrons, the charge on the left is -2, and the charge on the right is 0.
by Se-Young Lee
Sat Feb 08, 2014 5:25 pm
Forum: Balancing Redox Reactions
Topic: 13.3 a) Error
Replies: 4
Views: 620

13.3 a) Error

Hello professor,

I'd just like to point out that there is an error in the solutions manual for chapter 13 number 3 part a: the solutions manual writes the balanced form of the oxidation equation as S2O3^2- + 5H2O -> 2SO4^2- + 10H^+ + 8e^- , when there should in fact, be 10 electrons. Thank you-
by Se-Young Lee
Fri Feb 07, 2014 8:46 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: kPa and deltaS=nRln(p1/p2)
Replies: 2
Views: 356

Re: kPa and deltaS=nRln(p1/p2)

Also, notice how all units of pressure, whether they be in atm, bar, Torr or Pascals, operate in the same ratio due to the fact that each are scalar multiples of one another. A clarifying point: 1520 Torr/ 760 Torr = 2atm/1atm = (roughly) 2 bar/1 bar = (roughly) 202 KPa/101 KPa =2/1
by Se-Young Lee
Fri Feb 07, 2014 8:37 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Estimating the Boiling Point Q8.21
Replies: 1
Views: 974

Re: Estimating the Boiling Point Q8.21

Hi, To estimate the boiling point using Trouton's rule, I understand that the rule becomes: T is greater or equal to deltaH /deltaS. On question 8.21 from the textbook, it asks us to find the estimate of the boiling point of diethyl ether, with standard enthalpy of vaporization given. So I looked u...
by Se-Young Lee
Thu Feb 06, 2014 10:42 am
Forum: General Science Questions
Topic: Bose-Einstein condensate and light
Replies: 2
Views: 1037

Bose-Einstein condensate and light

Cooling matter down close to absolute zero produces a different state of matter that exhibits strange properties in which each individual atom loses its identity and establishes a new "quantum identity" in which all atoms unify into a single bulk. In a fascinating video that I watched, sci...
by Se-Young Lee
Thu Feb 06, 2014 9:47 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Why does heating water require more heat than copper?
Replies: 2
Views: 302

Re: Why does heating water require more heat than copper?

Also, looking at the chemical aspect of a copper compound as compared with water, copper's metallic bond is quite strong, but the atoms within a copper metal is locked in place via a face-centered cubic crystal structure, allowing for less degrees of rotational, vibrational, and translational freedo...
by Se-Young Lee
Thu Feb 06, 2014 9:34 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Equipartition Theorem
Replies: 2
Views: 309

Re: Equipartition Theorem

The 'Equipartition Theorem', or "theorem of equipartition of energy" states that "molecules in thermal equilibrium have the same average energy in relation to each individual degree of freedom of their motion" (reliable online source)-- what's the practical application for this? ...
by Se-Young Lee
Thu Feb 06, 2014 9:15 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Molar Entropy
Replies: 2
Views: 475

Re: Molar Entropy

In general, compounds that are in a more disordered state of matter (i.e. a gas phase, as opposed to a liquid phase) are said to have greater "molar entropy", due to the fact that they can occupy more a greater number of permutations for their position. Following this logic, compounds with...
by Se-Young Lee
Thu Feb 06, 2014 9:09 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: With regards to moles in calculation
Replies: 1
Views: 293

With regards to moles in calculation

Hello professor,

In calculating the number of moles given an 'x' gram of gas that is usually in diatomic state (such as Helium), why do we assume that the gas is monoatomic in solving problems?
by Se-Young Lee
Sat Jan 25, 2014 12:16 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Do all pressure units operate in the same gradient?
Replies: 2
Views: 333

Do all pressure units operate in the same gradient?

For instance, when calculating the natural logs of the quotient between the initial pressure and final pressures, must we convert kPa to atm, or would that be unnecessary? If unnecessary, please explain why. Thank you!
by Se-Young Lee
Thu Jan 23, 2014 11:34 pm
Forum: Phase Changes & Related Calculations
Topic: trouton's rule
Replies: 2
Views: 497

Re: trouton's rule

I know that organic means containing carbon, C. So any liquid hydrocarbons, alcohols, etc. look at appendix 2A, A16 Ah, you should be careful here-- not all compounds containing carbon are organic: carbon dioxide, sodium bicarbonate, and carbon tetrachloride are all inorganic. The general rule of t...
by Se-Young Lee
Thu Jan 23, 2014 11:28 pm
Forum: Phase Changes & Related Calculations
Topic: temperature
Replies: 4
Views: 499

Re: temperature

Yes, all enthalpy of formation values listed in the chart are at values of 298.15 kelvin.
by Se-Young Lee
Thu Jan 23, 2014 11:27 pm
Forum: Phase Changes & Related Calculations
Topic: sign in front
Replies: 5
Views: 572

Re: sign in front

could you please clarify what you mean by "sign in front"? There are multiple situations in which you have signs in front-- heat flowing into a system would be an increase in internal energy, so a "positive sign", whereas heat flowing out of a system would constitute a decrease i...
by Se-Young Lee
Sun Jan 19, 2014 9:53 am
Forum: Calculating Work of Expansion
Topic: Using the correct unit in calculation
Replies: 3
Views: 328

Re: Using the correct unit in calculation

Recall that the Kelvin scale of temperature measurement and the celsius scale of temperature measurement use the same unit gradient, or are simply linear to one another: Kelvins are essentially the same units of measurement as celsius, +273.15 degrees. Whenever you encounter a problem that asks for ...
by Se-Young Lee
Sun Jan 19, 2014 9:34 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: entropy
Replies: 2
Views: 339

Re: entropy

The following statements that I am about to make are ROUGH generalities (that is in no way an axiom) that I thought of after a quarter of the professor's lecture and recent lectures, so do not quote me on these: Reactions in which products are formed into more "ordered states" (such as fro...
by Se-Young Lee
Fri Jan 17, 2014 7:58 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Work = -P X delta-V
Replies: 4
Views: 1036

Re: Work = -P X delta-V

It may also be useful to look up other constants for other units of pressure, including torr and bar (though it's simple enough to just convert from one to another)
by Se-Young Lee
Fri Jan 17, 2014 7:33 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 7.29 C
Replies: 3
Views: 424

Re: 7.29 C

Or you can also generalize it this way: Recall the different modes of storing energy at the atomic/molecular level: vibrations, translational movement, and rotation. You can view each of these three types of atomic displacement as a way of atoms storing energy, since atomic movement causes a disrupt...
by Se-Young Lee
Sat Dec 07, 2013 12:15 pm
Forum: Quantum Numbers and The H-Atom
Topic: Maximum number e- if n=5
Replies: 3
Views: 1086

Re: Maximum number e- if n=5

For n = 5, recall that the azimuthal quantum number (l) ranges from 0-4 as the professor mentioned. Below is a list of what each number from 0-4 symbolizes. 0 = s 1 = p 2 = d 3 = f 4 = g recall that for each of these l values, you can have a range of suborbitals from -l to +l, and each of those subo...
by Se-Young Lee
Sat Dec 07, 2013 11:59 am
Forum: Hybridization
Topic: When does hybridization occur?
Replies: 5
Views: 671

Re: When does hybridization occur?

I mean yes, having two regions of electron density gives you a hybridization scheme of 'sp', three regions sp2, four regions sp3, five regions sp3d, six regions sp3d2, etc... but is there a more 'scientific way' of calculating hybridization, or is the empirical method the only way of determining hyb...
by Se-Young Lee
Sat Dec 07, 2013 11:58 am
Forum: *Titrations & Titration Calculations
Topic: 12.23
Replies: 11
Views: 1432

Re: 12.23

Sure thing! I'll re-edit this post once I get home (currently out)
by Se-Young Lee
Fri Dec 06, 2013 7:37 pm
Forum: *Titrations & Titration Calculations
Topic: 12.23
Replies: 11
Views: 1432

Re: 12.23

(a) sketch the titration curve for the titration of 5.00 mL 0.010 M NaOH with 0.005 M HCl, indicating the pH of the initial and final solutions and the pH at the stoichiometric point. --> how do you find the pH of the final solution? Okay, so I'm assuming that you already know how to figure out the...
by Se-Young Lee
Thu Dec 05, 2013 11:12 pm
Forum: Naming
Topic: when to write Ion and writing the order of the ligands
Replies: 3
Views: 500

Re: when to write Ion and writing the order of the ligands

The overall charge must be zero.
by Se-Young Lee
Thu Dec 05, 2013 11:04 pm
Forum: Significant Figures
Topic: Sig fig rules in quadratic equation
Replies: 1
Views: 501

Re: Sig fig rules in quadratic equation

According to my physics teacher in high school, you should always follow the rule of the "least accurate measurement". For example, the terms in the following: -0.0200 +/- sqrt(0.00400 + 0.05)/2.00 should have a significant figure of 1, since 0.05 is the least accurate measurement taken. (...
by Se-Young Lee
Thu Dec 05, 2013 10:50 pm
Forum: Dipole Moments
Topic: Certain Structures and Polarity
Replies: 3
Views: 573

Re: Certain Structures and Polarity

Knowledge of vector addition is incredibly helpful, and is in fact, the definitive way of figuring out polarity of any structure.
by Se-Young Lee
Thu Dec 05, 2013 10:45 pm
Forum: Hybridization
Topic: When does hybridization occur?
Replies: 5
Views: 671

Re: When does hybridization occur?

Professor, what would be the more formal method of determining hybridization?
by Se-Young Lee
Thu Dec 05, 2013 10:42 pm
Forum: Polyprotic Acids & Bases
Topic: Fall 2008 Final Question 6D
Replies: 7
Views: 682

Re: Fall 2008 Final Question 6D

Also, Ka3 becomes really small because the molecule itself becomes more negative as protons are removed, so it holds on to its remaining protons strongly. The more negatively charged the overall molecule, the stronger the pull on the protons. Also, the smaller the atomic radius of the anion, the sh...
by Se-Young Lee
Tue Dec 03, 2013 9:54 pm
Forum: General Science Questions
Topic: Random question about the word "Base"
Replies: 3
Views: 1033

Re: Random question about the word "Base"

Hey powerberry, that's incredibly interesting! Thank you! Looks like I formulated my very own (possibly valid) theory!
by Se-Young Lee
Mon Dec 02, 2013 10:04 pm
Forum: Calculating the pH of Salt Solutions
Topic: Question 11.75, part C. (Knowing Ka and Kb values)
Replies: 3
Views: 570

Re: Question 11.75, part C. (Knowing Ka and Kb values)

Professor,
if we were given all the initial concentrations of reactants and products involved (without Ka), would we use mole ratios to determine the limiting reactant to solve for the equilibrium constant?
by Se-Young Lee
Mon Dec 02, 2013 10:00 pm
Forum: General Science Questions
Topic: Random question about the word "Base"
Replies: 3
Views: 1033

Random question about the word "Base"

Professor,

is it mere coincidence that the word 'base' as in 'basic solution' happens to coincide with the word 'basin'? After all, a base is really just a basin of attraction for protons, or a basin that contains electrons.
by Se-Young Lee
Mon Dec 02, 2013 9:51 pm
Forum: Identifying Acidic & Basic Salts
Topic: Group 1 and 2 metals and pH
Replies: 1
Views: 393

Re: Group 1 and 2 metals and pH

I have been told that metals can make a salt/compound act as an acid. I am unsure if it is because of how I am thinking about it, but this, however, seems to contradict the statement that metals form group 1 and 2 don't affect pH. Can you please clarify? Metals, by themselves, do not affect pH: rec...
by Se-Young Lee
Mon Dec 02, 2013 9:40 pm
Forum: *Titrations & Titration Calculations
Topic: Titration curve
Replies: 4
Views: 481

Re: Titration curve

how do you even know what the initial or final pH is? why is the graph only showing HCl and bit NaoH??? how do you know what volume of HCL has been added at b. stoichiometric point c. halfway point of titration? Initial and final pH values are approximately equal to the initial concentrations of yo...
by Se-Young Lee
Mon Dec 02, 2013 9:10 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: pKa and its relationship with how acidic something is
Replies: 3
Views: 10272

Re: pKa and its relationship with how acidic something is

ELI5: Recall that the larger the denominator, the smaller the number. In the case of a number such as 1.0 * 10^-10, that's saying 1.0/10^10, which is incredibly close to zero. Also recall that Ka or Kb is given in numbers that are incredibly small, which are generally smaller than 1. (Anything large...
by Se-Young Lee
Mon Dec 02, 2013 8:36 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE Box equations without the value of K
Replies: 2
Views: 446

Re: ICE Box equations without the value of K

It would be helpful if you could provide us with the question.
by Se-Young Lee
Mon Dec 02, 2013 8:29 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Quiz 3 WB #10
Replies: 6
Views: 878

Re: Quiz 3 WB #10

I know the new initial partial pressure for BrCl is .54 (half of 1.08), but do the the other initial partial pressures change? They stay at 4.9 bar B 2 and 7.6 bar Cl 2 , right? Or would everything need to be halved to find the new equilibrium partial pressures? Nope- recall that everything remains...
by Se-Young Lee
Mon Dec 02, 2013 8:21 pm
Forum: Naming
Topic: Copper vs. Cupperate
Replies: 2
Views: 753

Re: Copper vs. Cupperate

Just for future reference, by "Latin root", we mean the original Latin names used to refer to these substances. For example, the nomenclature of the elements helium and oxygen make sense to us, since the element name is related to the first two, or first letter, or even the first letter + ...
by Se-Young Lee
Mon Dec 02, 2013 8:08 pm
Forum: *Making Buffers & Calculating Buffer pH (Henderson-Hasselbalch Equation)
Topic: 11.21a
Replies: 4
Views: 389

Re: 11.21a

Hey, you can find the Ka2 values in page 455 of the textbook, and solve for pKa2.
by Se-Young Lee
Mon Dec 02, 2013 8:06 pm
Forum: Lewis Acids & Bases
Topic: Amphoteric
Replies: 1
Views: 385

Amphoteric

Professor, Can we state that all acids and bases, regardless of whether they are strong or weak, have some amphoteric character? (Even though HCl is a strong acid, Cl- still has capacity to act as a sink for protons, since the overwhelming majority of H2O molecules are converted to H3O+, Cl- takes l...
by Se-Young Lee
Sun Nov 17, 2013 11:12 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Module Part 3, Question 7 (pre-assessment)
Replies: 3
Views: 553

Re: Module Part 3, Question 7 (pre-assessment)

Robot X, it was much more fun to see you in character.
by Se-Young Lee
Sun Nov 17, 2013 11:09 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Module 41
Replies: 2
Views: 312

Re: Module 41

004253593 wrote:41. Write the equilibrium constant expression for: NH4+ (aq) + H2O (l) ⇌ NH3 (aq) + H3O+ (aq)

does aq get be in equation?


The question was, do aqueous solutions participate in the calculation of equilibrium constants, and the answer is yes. Kc will be equal to [H3O][NH3] / [NH4]
by Se-Young Lee
Sun Nov 17, 2013 11:06 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Module #38
Replies: 2
Views: 330

Re: Module #38

Recall that the term 'solvent' explicates a liquid, which is undiluted by definition. Since liquids are excluded from equilibrium constants due to their incompressible nature, solvents are also excluded.
by Se-Young Lee
Sun Nov 17, 2013 11:03 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 10.71 c and d
Replies: 3
Views: 490

Re: 10.71 c and d

co + h20 - CO2 + H2 c. if concentration of CO is increased, what happens to the equilibrium constant for the reaction? d. if the concentration of H20 is decreased, what happens to the equilibrium constant for the reaction? Yes, it is true that equilibrium constants do not change; hence, the name 'e...
by Se-Young Lee
Sun Nov 17, 2013 10:58 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Accounting for aqueous solutions vs accounting for liquids
Replies: 2
Views: 527

Re: Accounting for aqueous solutions vs accounting for liqui

Thought that I should expand on Robot X's answer, since I'm sure you're curious as to why it's the case that we set liquids and solids equal to 1. Aqueous solutions, by definition, are solutions in which solvent is water: (hence aqua, and eous meaning "like water"). Thus, aqueous solutions...
by Se-Young Lee
Sun Nov 17, 2013 10:11 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Anti bonds and de stabilizing
Replies: 1
Views: 485

Re: Anti bonds and de stabilizing

Great question. In purely mathematical terms, antibonds are destructive wave interferences, (recall that electrons are represented by mathematical wave functions according to quantum theory), which means that the overlap of the atomic orbitals of two nuclei in a molecule is "out of phase",...
by Se-Young Lee
Sun Nov 17, 2013 9:56 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Homework 10.27
Replies: 2
Views: 386

Re: Homework 10.27

Ah, touché.
by Se-Young Lee
Sun Nov 17, 2013 9:50 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Cubic equations for x
Replies: 2
Views: 367

Re: Cubic equations for x

We won't be dealing with cubics, but if you do run into them in the future, you could graph it and find the zeros (on a graphing calc of course) But of course, sadly and unfortunately, we can't use graphing calculators in the chemistry courses that we will be taking in the future? (don't quote me o...
by Se-Young Lee
Sun Nov 17, 2013 9:45 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE Box
Replies: 1
Views: 381

Re: ICE Box

Right, because solids and pure liquids do not affect the reactant amount at equilibrium.
by Se-Young Lee
Sun Nov 17, 2013 9:37 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: module question 5
Replies: 3
Views: 532

Re: module question 5

Recall that even during chemical equilibrium, forward and reverse reactions are still occurring, just at equal rates: hence, the "dynamic" aspect of chemical reactions. Accordingly, the rate at which reactants are producing products, is equal to the rate at which products are forming react...
by Se-Young Lee
Sun Nov 17, 2013 9:32 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium Concentration vs. Concentration
Replies: 2
Views: 375

Re: Equilibrium Concentration vs. Concentration

To expand, remember that 2 is your stoichiometric coefficient indicating how many of your molar concentrations are interacting with itself (in this case, two). So, [M]^2 would mean you have two [M] concentrations interacting in the reaction, or two moles of concentrated M.
by Se-Young Lee
Sun Nov 17, 2013 9:29 pm
Forum: Naming
Topic: Water as H2O or OH2?
Replies: 2
Views: 18569

Re: Water as H2O or OH2?

Either is perfectly fine. In fact, you can write any compound in any order-- for example, you could call ethylenediamine--which in the book is NH2CH2CH2NH2-- N2C2H8, or C2N2H8, or even H8N2C2, but the reason why it's written the way it is in the book, is to emphasize the order of bonding when drawin...
by Se-Young Lee
Sun Nov 17, 2013 9:21 pm
Forum: Naming
Topic: Number of Binding Spots for CO3(2-)
Replies: 3
Views: 873

Re: Number of Binding Spots for CO3(2-)

There ARE three oxygens, but only two of them have a (-) formal charge and thus attract other compounds to come bind. The last one is double bonded and has a zero formal charge and thus it has no reason for forming a coordinate covalent bond with anything. It is the same reason why something like E...
by Se-Young Lee
Sun Nov 17, 2013 9:10 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Determining what is a chelate
Replies: 2
Views: 433

Re: Determining what is a chelate

Chelates are polydentate ligands-- essentially anything that is (Greek prefix)-dentate is a chelate. If you observe how many lone pairs of electrons are on each atom of a compound, and geometrically see whether those charged atoms are in a trans or cis conformation, you'll be able to determine that ...
by Se-Young Lee
Sun Nov 17, 2013 9:08 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Polydenates vs Chelates
Replies: 1
Views: 380

Re: Polydenates vs Chelates

A: by definition, chelates are polydentate ligands, and the formation of a complex ion between a chelate and a metal ion is called "chelation".
by Se-Young Lee
Sun Nov 17, 2013 9:05 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Oxalate and Oxygen's valence electrons
Replies: 1
Views: 449

Re: Oxalate and Oxygen's valence electrons

It has four total binding sites, but geometrically, the molecule isn't able to bend in such a way that allows it to bind to four different receptors. If you were to bind all four sites, you'd have to break a couple of bonds to allow that molecule to bind at all four sites, and that would be energeti...
by Se-Young Lee
Sun Nov 17, 2013 8:54 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: quiz 3 prep number 4
Replies: 1
Views: 373

Re: quiz 3 prep number 4

Recall that NH2CH2CH2NH2 is ethylediamine, or simply "en" when we write chemical formulas for compounds. En is a bidentate that forms two bonds, namely at its two nitrogen sites that contain lone pairs of electrons. Since those two nitrogens are available for bonding, each "en" b...
by Se-Young Lee
Sun Nov 17, 2013 8:46 pm
Forum: Naming
Topic: Am I alphabetizing Wrong
Replies: 5
Views: 745

Re: Am I alphabetizing Wrong

Either way is fine-- in the case of actually writing the chemical equations, writing the ligands in the chemical formula in alphabetical order isn't necessary.
by Se-Young Lee
Thu Nov 14, 2013 2:17 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Homework 10.27
Replies: 2
Views: 386

Homework 10.27

In homework 10.27, table 10.2 states that in the reaction H2 + I2 <-> 2HI, at 500K, Kc is given to be 4.00 x 10^18, but the solutions manual seems to state that Kc = 160. Clarification please?
by Se-Young Lee
Mon Nov 11, 2013 7:34 pm
Forum: General Science Questions
Topic: Supersymmetry and spherical nature of electrons
Replies: 1
Views: 601

Supersymmetry and spherical nature of electrons

Professor, how do you personally feel about the supersymmetry theory? A group called the ACME collaboration, led by David DeMille of Yale University and John Doyle and Gerald Gabrielse of Harvard University recently discovered with incredible precision, that electrons may be more spherical, and lack...
by Se-Young Lee
Mon Nov 11, 2013 5:09 pm
Forum: Ideal Gases
Topic: Intermolecular and interionic interactions and gas behavior
Replies: 2
Views: 526

Intermolecular and interionic interactions and gas behavior

Hello, I have a small question regarding ideal gases: how do intermolecular and interionic interactions affect the value of the activity of gases? Even though the definition of ideal gases is that they are non-interacting points particles in space, they do, in fact, interact to form product with oth...
by Se-Young Lee
Mon Nov 11, 2013 4:21 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: module question 8
Replies: 1
Views: 323

Re: module question 8

8. For a balanced chemical equation with different stoichiometric coefficients, what is the simplest expression for the equilibrium constant? For a balanced chemical equation with different stoichiometric coefficients, what is the simplest expression for the equilibrium constant? A. The ratio of th...
by Se-Young Lee
Mon Nov 11, 2013 4:13 pm
Forum: Ionic & Covalent Bonds
Topic: Q4A on 2008 Midterm
Replies: 2
Views: 472

Re: Q4A on 2008 Midterm

To add to Robert, it specifically means ionization energy with respect to the number of electrons you are removing. For example, l3 means the "third ionization energy", or the amount of energy required to remove three electrons from the atom.
by Se-Young Lee
Mon Nov 11, 2013 4:11 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium and limiting reactants
Replies: 1
Views: 307

Equilibrium and limiting reactants

In concept, would a reaction reach equilibrium when there is a limiting reactant, or will the equilibrium be shifted since there are excess reactants?
by Se-Young Lee
Fri Nov 08, 2013 10:29 pm
Forum: Hybridization
Topic: Fall 2010, Q6
Replies: 4
Views: 501

Re: Fall 2010, Q6

I have another question regarding the bond composition/ hybridization of each lone pair. Why is it that the lone pairs attached to Oxygen have a hybridization of Osp 2 , while everyother hybridization is listed with the principle quantum # (2 in each case). In other words, why is it Osp 2 and not O...
by Se-Young Lee
Fri Nov 08, 2013 10:27 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: MO diagram and Lewis Structure of CO
Replies: 7
Views: 1889

Re: MO diagram and Lewis Structure of CO

meaning what does Bond orders of 0.5, 1.5, and 2.5 indicate in terms of the bond between two atoms? Think resonance-- it's a delocalization of a single unpaired electron that has probability density encompassing the entire molecule (though it's not always the case, it generally works). For instance...
by Se-Young Lee
Fri Nov 08, 2013 10:22 pm
Forum: General Science Questions
Topic: Touch
Replies: 1
Views: 685

Touch

Is what we consider "touch" and "force" the result of electron repulsion, or are there other forces at play? I'm trying to explain life to a 8 year old who's incredibly interested in chemistry, and we happened to come across the topic of perception.

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