Search found 26 matches

by Austin Hyun 1F
Sat Mar 12, 2016 1:08 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: concentration cells
Replies: 2
Views: 286

Re: concentration cells

If you consider the definition of a standard cell potential, it is the cell potential at a standardized molar concentration. Therefore, in a concentration cell, when the potential is generated by a difference in concentration, the standard cell potential must be zero (because it measures the potenti...
by Austin Hyun 1F
Sat Mar 12, 2016 12:47 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Rate Constant k and Ea
Replies: 1
Views: 333

Re: Rate Constant k and Ea

Well, when the rate constant increases, either the activation energy may have decreased or the temperature may have increased, yes. However, it's important to note that it is a rate constant , and so the rate constant is not manipulated on its own. It changes as a result of variables that impact it ...
by Austin Hyun 1F
Sat Mar 12, 2016 12:44 pm
Forum: *Identifying Primary, Secondary, Tertiary, Quaternary Carbons, Hydrogens, Nitrogens
Topic: Neo- vs. Tert- and Sec- vs. Iso-
Replies: 1
Views: 905

Neo- vs. Tert- and Sec- vs. Iso-

So just to clarify, a substituent would be referred to as tertbutyl over neobutyl, and isopropyl over secpropyl? Why are these priorities inconsistent (i.e. iso- over sec-, but neo not over tert-)?
by Austin Hyun 1F
Sat Mar 05, 2016 8:42 am
Forum: *Cyclohexanes (Chair, Boat, Geometric Isomers)
Topic: Beyond Cyclohexanes
Replies: 1
Views: 236

Beyond Cyclohexanes

So I understand that the bond angle strain should be minimal for cyclohexanes, as it reaches the intended bond angle for an sp 3 hybridized carbon, but then for larger ring structures (e.g. cycloheptane, cyclooctane, etc.), is there any sort of way of having even less bond angle strain? Or would it ...
by Austin Hyun 1F
Sat Feb 27, 2016 11:34 pm
Forum: *Alkanes
Topic: Tert- and Sec- Prefixes
Replies: 2
Views: 314

Tert- and Sec- Prefixes

Why are the carbons referred to as tertiary and secondary carbons for the tert- and sec- side chains? Aren't they really quaternary and tertiary carbons? (e.g. with a tert-butylpropane, the carbon connecting the side chain to the main propane chain would be bonded to four carbons, not three carbons,...
by Austin Hyun 1F
Sun Feb 21, 2016 10:03 pm
Forum: *Organic Reaction Mechanisms in General
Topic: Local Energy Minimum?
Replies: 1
Views: 2074

Re: Local Energy Minimum?

As far as I understand it, the local energy minimum is simply an indication of the minimum free energy level between the two transition states. The reason it is called the "local" energy minimum is because it is the lowest energy level between only these two states (in comparison to the gl...
by Austin Hyun 1F
Sat Feb 20, 2016 5:11 pm
Forum: *Organic Reaction Mechanisms in General
Topic: Pseudo-Equilibrium Constant
Replies: 1
Views: 348

Pseudo-Equilibrium Constant

Because transition states are very unstable, will pseudo-equilibrium constant values always favor the non-transition state? (e.g. when k = [AB]/[A][B], will k always be < 1?)
by Austin Hyun 1F
Sun Feb 07, 2016 7:51 pm
Forum: Van't Hoff Equation
Topic: Van't Hoff Equation
Replies: 5
Views: 1176

Re: Van't Hoff Equation

So essentially, the Van't Hoff Equation is used to calculate the equilibrium constant at different temperatures. The equation assumes a constant delta S o and a constant delta H o , as these standard values should not change based upon a temperature change. Thus, given K 1 at temperature T 1 , you c...
by Austin Hyun 1F
Sun Jan 31, 2016 1:38 pm
Forum: Balancing Redox Reactions
Topic: Page 4 of Course Reader Thermochem
Replies: 2
Views: 320

Re: Page 4 of Course Reader Thermochem

Hi Kawsar! So if you look at the previous page of the course reader (pg. 49), it states that a positive value of E o means reduction is spontaneous. And, as you stated, the copper half reaction involves a loss of electrons (oxidation), and as it is the reverse of a spontaneous copper reduction, this...
by Austin Hyun 1F
Sun Jan 31, 2016 1:16 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: The laws of thermodynamics
Replies: 2
Views: 420

Re: The laws of thermodynamics

So basically, the First Law of Thermodynamics states that energy cannot be created or destroyed; it is conserved during energy transfers or transformations. As the course reader describes on pg. 26, "the internal energy of an isolated system is constant." The Second Law of Thermodynamics s...
by Austin Hyun 1F
Sat Jan 23, 2016 2:04 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: Microstates
Replies: 1
Views: 438

Microstates

Based on the Boltzmann equation (and knowing that entropy can never reach 0), does this imply that there can never be only 1 microstate (W=1)?
by Austin Hyun 1F
Sat Jan 23, 2016 2:00 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard State
Replies: 1
Views: 326

Re: Standard State

Standard state should be indicated within the problem (or can be inferred if the problem states that it is at 273 K [25 oC] and 1 atm). I hope that helps!
by Austin Hyun 1F
Fri Jan 08, 2016 1:43 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard Enthalpy of Formation
Replies: 2
Views: 247

Re: Standard Enthalpy of Formation

Standard enthalpy of formation will be zero for elements, not compounds. For instance, H2O is composed of H2 and 1/2O2, and both of these have a standard enthalpy of formation of 0. I hope that helps!
by Austin Hyun 1F
Sat Dec 05, 2015 7:03 pm
Forum: Lewis Acids & Bases
Topic: Random Pressure Question
Replies: 1
Views: 322

Re: Random Pressure Question

Hi, Whitney. In general, as elevation increases, the pressure will decrease, as will the temperature. However, in terms of boiling point, boiling occurs when the vapor pressure is equal to the atmospheric pressure. Because pressure generally decreases as elevation does, the threshold pressure at whi...
by Austin Hyun 1F
Sat Dec 05, 2015 6:57 pm
Forum: *Titrations & Titration Calculations
Topic: Half-ing molarities?
Replies: 1
Views: 360

Re: Half-ing molarities?

Hi, Alexander. So at the stoichiometric point, the number of moles of the analyte (CH 3 COOH) is equal to the number of moles of the titrant (NaOH), and because these two compounds are of equal concentrations, the volume of titrant added will be equal to the volume of the weak acid. Thus, the total ...
by Austin Hyun 1F
Sat Dec 05, 2015 11:59 am
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Acid Strength of HF Versus Fluorine Oxoacid
Replies: 1
Views: 386

Acid Strength of HF Versus Fluorine Oxoacid

Why is HF, unlike the rest of the hydrogen halids, a weak acid, whereas the fluorine oxoacid discussed at Professor Lavelle's review session (and found in Q7B of the Fall 2013 Final Exam) is a stronger acid than its chlorine counterpart? Thanks!
by Austin Hyun 1F
Sun Nov 29, 2015 9:31 pm
Forum: Polyprotic Acids & Bases
Topic: loosing an h+ for a negative ion
Replies: 1
Views: 318

Re: loosing an h+ for a negative ion

Hi Grace,

So as a polyprotic acid loses each proton, the affinity of the remaining positive hydrogen ion[s] to the electrons of the compound increases. The Ka value will decrease with each dissociation to reflect such. I hope this helps!
by Austin Hyun 1F
Tue Nov 17, 2015 5:35 pm
Forum: Naming
Topic: New IUPAC Names
Replies: 2
Views: 418

Re: New IUPAC Names

Well, according to the course reader, at least for the purpose of this class, we can use the old names, rather than the IUPAC names, so you could just write "cyano," I think. However, in terms of the meaning, I don't know the direct translation, but basically I believe it indicates which a...
by Austin Hyun 1F
Sun Nov 08, 2015 9:04 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K of Reactions Proceeding to Completion
Replies: 1
Views: 316

K of Reactions Proceeding to Completion

For reactions that proceed to completion, does the equilibrium constant still apply, or does the reaction need to have a reverse reaction? If so, how would you indicate the equilibrium constant value? (because if the concentration of the reactants is 0, then wouldn't the K-value be undefined?)
by Austin Hyun 1F
Sun Nov 08, 2015 8:46 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: What happens to the rxn when a product/reactant is reduced?
Replies: 2
Views: 419

Re: What happens to the rxn when a product/reactant is reduc

Hi, I believe this actually relates to a concept we're learning later, referred to as Le Chatelier's Principle. Basically, when we remove product from this reaction, the reaction will proceed to consume the reactants to produce more product until the Q value returns to K eq . Similarly, if A is redu...
by Austin Hyun 1F
Sun Nov 08, 2015 8:35 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Molecular orbital order
Replies: 1
Views: 261

Re: Molecular orbital order

Hi Miya, So this change in the M.O. diagram is because the elements preceding oxygen on the periodic table have a nuclear charge less than 8 (Z<8). In these elements, the sigma orbitals' energies are increased, as they exist along the bond axis, whereas the pi orbitals' energies do not increase, as ...
by Austin Hyun 1F
Sat Oct 31, 2015 2:48 am
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Molecular Spectroscopy and Sunscreen
Replies: 1
Views: 275

Molecular Spectroscopy and Sunscreen

In Wednesday's lecture, Professor Lavelle talked about how, like in atomic spectroscopy, molecular spectroscopy involves the excitation of an electron to a higher energy level (i.e. the Highest Occupied Molecular Orbital to LUMO transition). He provided the example of finding the proper compounds to...
by Austin Hyun 1F
Thu Oct 22, 2015 5:51 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Molecular Shape and Biological Activity
Replies: 1
Views: 279

Re: Molecular Shape and Biological Activity

Molecular shape is especially important with regard to cellular signaling. Molecular shape is key for determination of what molecules may bind to what receptors. For instance, if you observe the concept of competitive inhibition, receptors will only bind to molecules of certain shapes, and by bindin...
by Austin Hyun 1F
Wed Oct 14, 2015 10:53 pm
Forum: Ionic & Covalent Bonds
Topic: The tetrafluoroborate anion and formal charge
Replies: 3
Views: 1102

Re: The tetrafluoroborate anion and formal charge

Hi, Audree! The issue is, as I understand it, while formal charge is not directly related to electronegativity, the relative formal charges do indicate relative degrees of electron attraction. For instance, with the BF 3 , double bonds between the boron and the fluorine are not possible, as (in addi...
by Austin Hyun 1F
Wed Oct 14, 2015 8:18 pm
Forum: Ionic & Covalent Bonds
Topic: The tetrafluoroborate anion and formal charge
Replies: 3
Views: 1102

The tetrafluoroborate anion and formal charge

Today in lecture we discussed the example of the BF 4 - anion, in which the octet of boron may be completed with a coordinate covalent bond. Professor Lavelle also explained that in a BF 3 molecule, double bonds are not possible, as this would yield formal charges that would indicate that boron is m...
by Austin Hyun 1F
Thu Oct 08, 2015 10:26 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Crossing Nodes
Replies: 1
Views: 651

Re: Crossing Nodes

Hi Jasmeet, Upon doing some research, it appears that electrons may travel through the node on account of their wave-particle duality. While the electron has a zero probability of being present at the nucleus, the wave properties of electrons permit it to travel through the node. The examples provid...

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