Search found 21 matches

Sat Mar 12, 2016 3:50 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Residual Entropy
Replies: 1
Views: 317

Residual Entropy

What exactly is residual entropy in comparison to entropy? What is different about the equations used to find each?
Mon Mar 07, 2016 9:05 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Equation for E
Replies: 1
Views: 323

Equation for E

Could someone please remind me of the two separate equations used to solved for E (the ones that use log and ln)?
Sat Feb 27, 2016 4:19 pm
Forum: *Alkanes
Topic: Quiz 3 Preparation #2
Replies: 1
Views: 212

Quiz 3 Preparation #2

Name the compound CH3CH(CH3)CH(CH2CH3)C(CH3)3. You you please explain how one would draw this compound and why it is named 2,2,4-trimethyl 3-ethylpentane?
Tue Feb 09, 2016 9:56 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Midterm 2013 #7
Replies: 3
Views: 520

Re: Midterm 2013 #7

Then when is the equation ever used?
Tue Feb 09, 2016 5:26 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Midterm 2013 #7
Replies: 3
Views: 520

Midterm 2013 #7

The first part of this question that requires you to calculate the cell potential does not make sense to me. The cell potential of the cathode (the half equation involving Br2) is positive, which makes sense, however the cell potential for the anode (Mn2+ equation) should have the sign of its given ...
Mon Feb 08, 2016 1:44 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: W for BH2F
Replies: 3
Views: 1668

W for BH2F

Could you please explain how to find the degeneracy for a molecule such as BH2F? I'm still unclear on exactly what is done to find the value.
Mon Feb 01, 2016 3:52 pm
Forum: Balancing Redox Reactions
Replies: 1
Views: 267

At the top of page 50 in the course reader, we are given an example of how to balance the half reactions to create a balanced redox reaction. I know Professor Lavelle said that if we know the half reactions are balanced, then the full one is, but I'm still confused since 2Fe (3+) + Cu \rightarrow Cu...
Sat Jan 23, 2016 3:42 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Quiz 1 Preparation, Winter 2014, #9 and #12
Replies: 1
Views: 290

Quiz 1 Preparation, Winter 2014, #9 and #12

Question 9 asks to calculate delta G for the balanced reaction. I obtained the correct numerical value, but my answer is in units of kJ instead of kJ/mol as the workbook's answer states. I have noticed this happening in several other calculations, but I thought that the moles canceled when you multi...
Thu Jan 21, 2016 11:43 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Cp,m
Replies: 2
Views: 1187

Cp,m

Okay, I realize this is a very dumb and simple question but I seriously do not understand what the "m" stands for in things such as Cp,m and Cv,m.
Sun Jan 17, 2016 5:16 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond Enthalpies vs. Mean Bond Enthalpy
Replies: 2
Views: 1208

Re: Bond Enthalpies vs. Mean Bond Enthalpy

Bond dissociation enthalpy is the energy needed to break one mole of the bond to give separated atoms - everything being in the gas state. Now consider methane, CH4. It contains four identical C-H bonds, and it seems reasonable that they should all have the same bond enthalpy. However, if you took m...
Thu Jan 07, 2016 4:56 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Nitrogen Dioxide Formation
Replies: 1
Views: 315

Nitrogen Dioxide Formation

On page 18 of the course reader, the example of calculating delta H for nitrogen dioxide formation is given. I am confused about the use of Hess's Law for adding together the two equations. Where does NO go? Is it not used simply because the question is asking for the formation, which only includes ...
Sat Dec 05, 2015 1:11 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Changing amount of a Solid
Replies: 3
Views: 585

Changing amount of a Solid

What happens to the pressure of H2O when the amount of Fe3O4 halves? Fe3O4 (s) + 4H2 (g) <--> 3Fe (s) + 4H2O (g)
Sat Dec 05, 2015 12:28 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Workbook Quiz 3 #10
Replies: 1
Views: 330

Workbook Quiz 3 #10

The question asks: for the reaction at equilibrium, HCl + I2 <--> HI + Cl2, how will an increase in the pressure (by decreasing the volume) effect the concentration of Cl2? I found this question a little confusing because in the course reader (p. 129), it says that if the pressure double, the concen...
Fri Nov 27, 2015 5:56 pm
Forum: Identifying Acidic & Basic Salts
Topic: Identification
Replies: 1
Views: 414

Identification

I feel like to know whether a salt is acidic or basic, you really just have to see if it includes one of 3 cations (Li, K, Na) or one of 3 anions (Cl, Br, I) and recognize that these will not affect pH, so the other half of the molecule must be the definer of the salt. Is this an oversimplification ...
Tue Nov 17, 2015 9:42 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Oxidation Number
Replies: 1
Views: 295

Oxidation Number

I just wanted to double check that I was understanding how to find the oxidation number for an element correctly. So basically you add up all of the charges of the anions and then just give the metal the opposite charge to ensure that the entire compound has a charge of 0 (or whatever the overall ch...
Sun Nov 08, 2015 1:31 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Solids and Liquids Chemical Equilibrium
Replies: 1
Views: 214

Solids and Liquids Chemical Equilibrium

I'm still confused how I could calculate the equilibrium constant when a reaction includes only solids and liquids. The course reader states the solids and liquids are not included in the equilibrium constant, so then does that just mean that no constant exists for that particular reaction? If so, t...
Thu Oct 29, 2015 3:38 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Molecular Orbitals
Replies: 1
Views: 560

Molecular Orbitals

I'm still a little confused why the sigma Pz orbital has a higher energy than the pi Px and pi Py orbitals when an element has an atomic number less than 8. Also, which type of molecular orbital diagram would I draw for a compound such as CCl4?
Sun Oct 25, 2015 3:57 pm
Forum: Hybridization
Topic: Hybridization
Replies: 1
Views: 334

Hybridization

If hybridization occurs with bonding and the overlapping of orbitals, then when is a molecule ever not hybridized, since all molecules have some type of bonding?
Wed Oct 14, 2015 5:23 pm
Forum: Lewis Structures
Topic: Lewis Structure Stability
Replies: 3
Views: 614

Lewis Structure Stability

Since many Lewis structures have a more stable and less stable option, does that mean for every Lewis structure we draw, we should always be checking if there is a more stable option? Is there any sort of way to quickly decide if a molecule will have multiple options by just looking at the formula?
Sun Oct 11, 2015 3:52 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Multiple Orbitals
Replies: 2
Views: 500

Multiple Orbitals

I have some confusion about the concept of multiple orbitals existing around one atom. If an atom has a d-orbital, does that mean that it also includes the shapes of the s and p orbitals? If so, do these orbitals all lie on top of each other in the given energy level? Or are they spaced out in some ...
Fri Oct 02, 2015 2:57 pm
Forum: DeBroglie Equation
Replies: 2
Views: 369

Momentum is also equal to the product of energy and velocity. Since a photon has energy and velocity, it can therefore have momentum, even though it does not have a mass.