Search found 25 matches
- Sun Mar 06, 2016 11:57 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Cv vs Cp
- Replies: 3
- Views: 1017
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.
- Sun Mar 06, 2016 11:16 pm
- Forum: *ChemDraw
- Topic: Determining highest-priority groups in isomers
- Replies: 2
- Views: 1462
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.
- Sun Mar 06, 2016 11:11 pm
- Forum: *Alcohols
- Topic: order of functional groups
- Replies: 1
- Views: 548
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...
- 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: 467
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?
- Sun Feb 28, 2016 11:37 pm
- Forum: *Cycloalkenes
- Topic: Numbering
- Replies: 2
- Views: 685
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.
- Sun Feb 28, 2016 11:34 pm
- Forum: *Organic Reaction Mechanisms in General
- Topic: Double Dagger
- Replies: 1
- Views: 2206
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.
- Sun Feb 28, 2016 10:04 pm
- Forum: *Alkanes
- Topic: Naming of Organic Compounds
- Replies: 1
- Views: 553
Naming of Organic Compounds
Does the placement of commas, dashes, and/or parenthesis affect the overall naming of an organic compound?
- Tue Feb 09, 2016 7:04 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Meaning of Ecell
- Replies: 1
- Views: 2004
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.
- 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: 565
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...
- 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: 1322
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! :)...
- Mon Jan 25, 2016 9:32 pm
- Forum: Calculating Work of Expansion
- Topic: How to Solve work under constant pressure
- Replies: 2
- Views: 655
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:
- Sun Jan 24, 2016 7:12 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gibbs Free Energy, Enthalpy, and Entropy
- Replies: 3
- Views: 10543
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!
Thanks!
- Sun Jan 17, 2016 2:29 pm
- Forum: Phase Changes & Related Calculations
- Topic: Study Group
- Replies: 2
- Views: 661
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/
- Sun Jan 10, 2016 9:29 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Phase Diagrams
- Replies: 1
- Views: 599
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...
- 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: 2131
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...
- 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: 929
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 ...
- Thu Nov 19, 2015 9:07 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Finding Equations Given Partial Pressures
- Replies: 2
- Views: 2362
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...
- Tue Nov 17, 2015 11:31 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Significant Figures with Chemical Equilibria?
- Replies: 1
- Views: 475
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...
- Wed Nov 11, 2015 4:27 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Determining if a reaction is in equilibrium
- Replies: 1
- Views: 382
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...
- Wed Nov 11, 2015 4:15 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Determining Polydentate Structures Through Formula
- Replies: 2
- Views: 695
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...
- Sun Oct 25, 2015 12:47 pm
- Forum: Lewis Structures
- Topic: 3.65 part C
- Replies: 1
- Views: 511
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...
- Sun Oct 18, 2015 5:54 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Shape of Xe molecules
- Replies: 1
- Views: 860
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...
- Sat Oct 10, 2015 5:08 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Homework 1.57
- Replies: 1
- Views: 500
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...
- Fri Oct 09, 2015 4:43 pm
- Forum: Properties of Electrons
- Topic: Homework 1.21?
- Replies: 1
- Views: 1859
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...
- Sun Oct 04, 2015 2:43 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: h/4pi in Heisenberg's Indeterminacy Equation
- Replies: 3
- Views: 7773
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 .