Search found 25 matches

by Lillian Xie 1K
Sun Mar 06, 2016 11:57 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Cv vs Cp
Replies: 3
Views: 587

Re: Cv vs Cp

If you have both constant pressure and constant volume, you likely don't have a calculation to make!! You use Cv under conditions of constant volume and Cp under conditions of constant pressure.
by Lillian Xie 1K
Sun Mar 06, 2016 11:16 pm
Forum: *ChemDraw
Topic: Determining highest-priority groups in isomers
Replies: 2
Views: 601

Re: Determining highest-priority groups in isomers

If there are multiple higher bonds, you need to identify whether each of them are cis/trans or E/Z. You tell your audience which bond is which in the beginning by listing the specifications in order respective to that in which the higher order bonds are listed.
by Lillian Xie 1K
Sun Mar 06, 2016 11:11 pm
Forum: *Alcohols
Topic: order of functional groups
Replies: 1
Views: 263

Re: order of functional groups

We don't need to know this for the scope of 14B (asked Professor Lavelle, and heard from TAs Daniel Hatfield and Brandon Yoshida), but when compounds contain more than one functional group, the order of precedence determines which groups are named with prefix or suffix forms. The order is as follows...
by Lillian Xie 1K
Sat Mar 05, 2016 2:36 am
Forum: *Constitutional and Geometric Isomers (cis, Z and trans, E)
Topic: Identifying cis, Z and trans, E
Replies: 1
Views: 265

Identifying cis, Z and trans, E

When you're looking at an organic molecule, how can you identify if a higher order bond qualifies as cis/trans or Z/E? What factors play into identifying whether a bond has these isomers?
by Lillian Xie 1K
Sun Feb 28, 2016 11:37 pm
Forum: *Cycloalkenes
Topic: Numbering
Replies: 2
Views: 371

Re: Numbering

You number the bonds in a way that ensures the lowest possible numbers for each of the substituents. So, if there are two double bonds on a hexene molecule, and you can number them either 1,3 or 4,6, you would choose 1,3 as the numbering.
by Lillian Xie 1K
Sun Feb 28, 2016 11:34 pm
Forum: *Organic Reaction Mechanisms in General
Topic: Double Dagger
Replies: 1
Views: 982

Re: Double Dagger

That symbol represents that the reaction taking place is a transition state. Also, if it is used with a K constant, then it refers to the pseudo-equilibrium established by the activated complex of arbitrary reactants A and B.
by Lillian Xie 1K
Sun Feb 28, 2016 10:04 pm
Forum: *Alkanes
Topic: Naming of Organic Compounds
Replies: 1
Views: 280

Naming of Organic Compounds

Does the placement of commas, dashes, and/or parenthesis affect the overall naming of an organic compound?
by Lillian Xie 1K
Tue Feb 09, 2016 7:04 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Meaning of Ecell
Replies: 1
Views: 438

Meaning of Ecell

Can someone please explain what Ecell in Ecell = Eknotcell - RT/lnQ stands for? Is it the net difference in voltage between a given cell and the same cell at standard conditions? I don't understand how this works, conceptually.
by Lillian Xie 1K
Tue Feb 09, 2016 6:58 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Winter 2011 Midterm Question 7&8 on Equilibrium and Gibbs
Replies: 1
Views: 327

Winter 2011 Midterm Question 7&8 on Equilibrium and Gibbs

Can someone please help me with these problems? I used the ln version of the Nernst equation and seem to be getting a different answer from the one in the book. Can someone explain why the answer says log K, when it uses a constant usually associated with ln in part C? Also, for part D, a similar si...
by Lillian Xie 1K
Sun Feb 07, 2016 2:50 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Does n have units?
Replies: 2
Views: 396

Re: Does n have units?

The variable, n, does have units. It is the number of moles of electrons exchanged in the electrochemical reaction, and so make sure that if you need to balance redox reactions before using the Nernst equation, to properly account for the exchanged electrons before solving for n. Hope this helps! :)...
by Lillian Xie 1K
Mon Jan 25, 2016 9:32 pm
Forum: Calculating Work of Expansion
Topic: How to Solve work under constant pressure
Replies: 2
Views: 379

Re: How to Solve work under constant pressure

Since the expansion work is done under isothermal and reversible conditions, you can use the following equation:
by Lillian Xie 1K
Sun Jan 24, 2016 7:12 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs Free Energy, Enthalpy, and Entropy
Replies: 3
Views: 6349

Gibbs Free Energy, Enthalpy, and Entropy

Can someone summarize/explain the relationship between Gibbs free energy, enthalpy, and entropy? I'm starting to get confused by what combinations result in spontaneous and non-spontaneous reactions.

Thanks!
by Lillian Xie 1K
Sun Jan 17, 2016 2:29 pm
Forum: Phase Changes & Related Calculations
Topic: Study Group
Replies: 2
Views: 308

Re: Study Group

There is an unofficial group on Facebook if you would like to join! Study groups are organized around midterm and final weeks. Feel free to make any posts. https://www.facebook.com/groups/930573750352011/
by Lillian Xie 1K
Sun Jan 10, 2016 9:29 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Phase Diagrams
Replies: 1
Views: 322

Re: Phase Diagrams

The shape of the phase change diagram will be affected by the temperatures at which the substances reach their freezing and boiling points. Another important factor to consider is the specific heat of the substance because that affects the slope since energy input is on the x axis. For example, if y...
by Lillian Xie 1K
Sun Nov 29, 2015 9:10 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: H2+I2----> 2HI equilibrium shift
Replies: 1
Views: 812

Re: H2+I2----> 2HI equilibrium shift

Your assumption was partially correct in that the change would produce more products, but this change is too negligible to really shift the equilibrium. The Kc constant shows that the ratio of products to reactants is very small, indicating that a much higher concentration of reactants exists compar...
by Lillian Xie 1K
Sat Nov 21, 2015 2:23 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Determining strength of acid or base
Replies: 2
Views: 421

Re: Determining strength of acid or base

Strong acids and bases are relatively rare since they are virtually 100% ionized, or they are very nearly completely dissociated. Strong acids generally have a very low pH (between 0 and 1), while strong bases generally have a very high pH (between 13 and 14). To contrast with these strengths, weak ...
by Lillian Xie 1K
Thu Nov 19, 2015 9:07 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Finding Equations Given Partial Pressures
Replies: 2
Views: 595

Finding Equations Given Partial Pressures

In textbook problem #89, the question reads as follows: The following plot shows how the partial pressures of reactant and products vary with time for the decomposition of compound A into compounds B and C. All three compounds are gases. Use this plot to do the following: (a) Write a balanced chemic...
by Lillian Xie 1K
Tue Nov 17, 2015 11:31 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Significant Figures with Chemical Equilibria?
Replies: 1
Views: 259

Significant Figures with Chemical Equilibria?

For 11.49 in the textbook, how would we know (like in this example) when to ignore normal significant figure conventions in order to obtain an answer? After the quadratic equation is obtained through the expression 1.6*10^-4 = 0.200x + x^2, how do we know to use round to four decimal places in the s...
by Lillian Xie 1K
Wed Nov 11, 2015 4:27 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Determining if a reaction is in equilibrium
Replies: 1
Views: 187

Re: Determining if a reaction is in equilibrium

If you aren't given a K value, you could be given a graph like the one I attached to this comment. When the forward rate of the reaction equals the reverse on the graph (when the y-values/concentrations for each line is constant), the reaction is in equilibrium. Otherwise, a K value would indicate t...
by Lillian Xie 1K
Wed Nov 11, 2015 4:15 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Determining Polydentate Structures Through Formula
Replies: 2
Views: 397

Determining Polydentate Structures Through Formula

Textbook Question 17.33 asks (essentially), which of the following can be polydentate? Give the maximum number of places that the ligand can bind simultaneously to the metal center. a) HN(CH2CH2NH2)2 b) (CO3)^2- c) H2O d) (C2O4)^2- How do you determine whether a ligand is polydentate? I know that lo...
by Lillian Xie 1K
Sun Oct 25, 2015 12:47 pm
Forum: Lewis Structures
Topic: 3.65 part C
Replies: 1
Views: 266

Re: 3.65 part C

There are single bonds between Xenon and each of the Fluorine atoms. Each Fluorine atom has three lone pairs (so six electrons aside from the bonded electrons with the Xenon. Because Xenon can have an expanded octet and is the central atom, it has two additional lone pairs. In total, all 36 of the e...
by Lillian Xie 1K
Sun Oct 18, 2015 5:54 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Shape of Xe molecules
Replies: 1
Views: 340

Re: Shape of Xe molecules

In the examples you presented, Xenon is the central atom because of its capacity for an expanded octet through its d-orbital. Take XeOF*2, for instance: While Xe has a higher ionization energy than both oxygen and fluorine, it's placed in the center because neither of these elements have a d-orbital...
by Lillian Xie 1K
Sat Oct 10, 2015 5:08 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Homework 1.57
Replies: 1
Views: 259

Homework 1.57

Hey! I was finishing up Chapter One and checking over my answers when I went through Question 1.57: "Lines in the Balmer series of the hydrogen spectrum are observed at 656.3, 486.1, 434.0, and 410.2 nm. What is the wavelength of the next line in the series?" I used the Rydberg equation, w...
by Lillian Xie 1K
Fri Oct 09, 2015 4:43 pm
Forum: Properties of Electrons
Topic: Homework 1.21?
Replies: 1
Views: 902

Homework 1.21?

Hey! I'm stuck on Question 1.21 from the homework. It states, "From the following list of observations, select the one that best supports the idea that electromagnetic radiation has the properties of particles. Explain your reasoning. a) Black-body radiation b) Electron diffraction c) Atomic sp...
by Lillian Xie 1K
Sun Oct 04, 2015 2:43 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: h/4pi in Heisenberg's Indeterminacy Equation
Replies: 3
Views: 770

Re: h/4pi in Heisenberg's Indeterminacy Equation

Adding on to what Shelby said, it makes sense that would be the constant that was experimentally derived because it relates back to how most graphs of waves involve the sine curve, which can be more conveniently graphed with a constant involving .

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