## Search found 22 matches

Sat Mar 12, 2016 11:03 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Internal Energy of Isothermal Processes
Replies: 2
Views: 734

### Internal Energy of Isothermal Processes

I'm still a bit confused conceptually as to why $\Delta$U is equal to zero in an isothermal process, since $\Delta$U=q+w and work can still be done on or by the system. Thanks :)
Sat Mar 05, 2016 11:20 pm
Forum: *Alkanes
Topic: Dichlorodiflouromethane line structure
Replies: 1
Views: 320

### Re: Dichlorodiflouromethane line structure

I think the cis-/trans- distinction only applies to geometric isomers with a C=C double bond, because in that situation the double bond locked the atoms into a specific geometry without independent rotation. So, in the case of dichlorodifluoromethane, the cis-/trans- isn't needed because the -ane su...
Sun Feb 28, 2016 11:41 am
Forum: *Alkenes
Topic: Benzene vs Phenyl
Replies: 2
Views: 479

### Re: Benzene vs Phenyl

I think benzene is a ring with 6 carbon atoms and 3 double bonds, whereas phenyl is like benzene but has an alkyl substituent (R, or a generic carbon chain) attached to one of the carbons in place of one of the hydrogen atoms.
Sun Feb 28, 2016 11:34 am
Forum: *Alkanes
Topic: Carbons
Replies: 2
Views: 432

### Re: Carbons

I think since the parent chain is the longest continuous chain of carbons you can form, when you draw out the given molecule, the longest possible chain you can get is a chain of five, hence the pentane part of the name. Then, regardless of how you counted the five, when it is drawn out you can see ...
Thu Feb 18, 2016 9:40 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: reaction profiles
Replies: 1
Views: 366

### Re: reaction profiles

Based on the workbook, I think you can only get a qualitative estimate of K (the equilibrium constant) (and thus the ratio of the rate constants, k/k ' )from a reaction profile (if it doesn't provide data) based on whether or not the formation of reactants or products is favored. So I think if t...
Thu Feb 18, 2016 9:31 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Low Activation Energy
Replies: 1
Views: 380

### Re: Low Activation Energy

I think if the activation energy is very small, a change in temperature will only make the term (E A /RT) smaller, but since it is already very small the change is not very significant. So, when it is used in the Arrhenius equation, k=Ae^(-E A /RT), k does not change very much either, meaning the ra...
Tue Feb 09, 2016 11:07 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Atom Size
Replies: 1
Views: 321

### Re: Atom Size

I think Flourine is a larger atom because it has more protons, more electrons, and thus more mass and more repulsion to expand the atomic radius. (Which I think also increases the degeneracy of molecules that contain F).
Tue Feb 02, 2016 8:28 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Max potential difference between electrodes
Replies: 1
Views: 341

### Re: Max potential difference between electrodes

Since the maximum potential difference occurs when there is no current, I think i stands for current flowing in the system.
Thu Jan 28, 2016 10:12 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: U=(3/2)nRT equation
Replies: 1
Views: 613

### U=(3/2)nRT equation

I'm still a bit confused about the relevance of the equation Utotal=(3/2)nRT. In what kind of circumstances would it be helpful or necessary to use it?
Thu Jan 28, 2016 10:06 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond Enthalpies
Replies: 3
Views: 548

### Re: Bond Enthalpies

I think in the bond enthalpy problems, broken bonds result in a +$\Delta$H, because heat is needed to break the bond and thus is added to the reaction. Then, forming a bond is the opposite and releases energy, resulting in a -$\Delta$H.
Wed Jan 20, 2016 6:56 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Entropy and Degeneracy
Replies: 1
Views: 379

### Re: Entropy and Degeneracy

I think the formula S=nRln2 applies for systems with a degeneracy of two (they can only be in 2 possible states). Otherwise, for given volume changes (and thus entropy changes) I think we use $\Delta$S=nRln(V2/V1) (although sometimes V2/V1 is equal to 2 so it ends up being $\Delta$S=nRln2!)
Sun Jan 10, 2016 4:26 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard reaction Enthalpy Vs Enthalpy of Formation
Replies: 1
Views: 575

### Re: Standard reaction Enthalpy Vs Enthalpy of Formation

From what I understand, I think standard reaction enthalpy is the ΔH o (amount of heat released in a reaction at a constant pressure) for any reaction that has reactants and products in their standard state at 1 atm, and is measured in kJ. Standard Enthalpy of formation , (ΔH f o ) is the standard r...
Thu Dec 03, 2015 11:18 pm
Forum: *Titrations & Titration Calculations
Topic: Titrant
Replies: 3
Views: 1160

### Re: Titrant

Additionally, I believe the titrant is always a strong acid or a strong base because they are easier to work with since they ionize completely. In an experimental setting, you would be choosing the titrant to you want to use, so it would be best to choose one that would make the calculations the eas...
Sat Nov 21, 2015 9:44 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: pH scale
Replies: 2
Views: 585

### Re: pH scale

In lecture, I think Professor Lavelle said that when the hydronium concentration is greater than 1, the pH is less than zero and the substance is considered a super acid. (And conversely super bases are those that have a pH over 14), which means it is possible to have pH less than 0 or greater than ...
Sat Nov 14, 2015 6:18 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Polydentate Ligands
Replies: 1
Views: 333

### Polydentate Ligands

If a ligand is polydentate, does that affect the naming of the ligand within the name of the coordination compound?
Thu Nov 05, 2015 9:17 pm
Forum: Lewis Structures
Topic: Lewis Structure of HClO3
Replies: 3
Views: 22321

### Re: Lewis Structure of HClO3

To my understanding, if the H atom is bonded to the central Cl atom, the Cl atom would have a formal charge of +1, while the O atom would have a formal charge of -1 if it had another lone pair instead of bonding with the H atom. So, the structure in which one O atom is bonded to the H atom and Cl ha...
Thu Oct 29, 2015 7:12 pm
Forum: Lewis Structures
Topic: Lewis Structure
Replies: 1
Views: 316

### Re: Lewis Structure

I think in the case of radicals, the unpaired electron goes with the atom that has remaining empty orbitals. So, in the case of CH 3 , the unpaired electron ends up with Carbon, because Carbon doesn't have an octet if it is only bonded with 3 Hydrogen atoms and thus has an empty orbital to accommoda...
Thu Oct 22, 2015 8:57 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: AXE Formation
Replies: 2
Views: 13401

### Re: AXE Formation

To get the AXE notation, A is representative of the central atom, X represents the number of atoms bonded to the central atom (the subscript is the number of non-central atoms), and E represents the number of lone pairs on the central atom. So, in the requested example, IF 3 is written AX 3 E 2 , be...
Wed Oct 14, 2015 9:36 pm
Forum: Trends in The Periodic Table
Topic: 2nd Ionization Energy
Replies: 2
Views: 553

### Re: 2nd Ionization Energy

I think the reason the second ionization energy would still be higher is that the remaining electron would then experience stronger electrostatic attraction to the positively charged nucleus, and would thus still need more energy to be removed.
Sun Oct 11, 2015 7:53 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Configurations
Replies: 1
Views: 291

### Re: Configurations

Based on my understanding of this topic, I think the first number is indicative of the energy level/shell the electrons occupy. (In the s- and p- blocks this number corresponds with the number of the row, but the 4s level fills up before the 3d level, and so on for each row.) Then, the letter repres...
Fri Oct 02, 2015 8:29 pm
Forum: SI Units, Unit Conversions
Topic: Grams to Mol
Replies: 3
Views: 1006

### Re: Grams to Mol

I think when you are doing a conversion, the grams are from the molar mass (g/mol) of the element/molecule/compound, and to find the molar mass you add the atomic mass of each unit within the molecule/compound. So, for example, the molar mass of water (H 2 O) is 18.02 g/mol (1.01 g H + 1.01 g H + 16...
Fri Oct 02, 2015 8:16 pm
Forum: *Shrodinger Equation
Topic: What is the hamiltonian?
Replies: 2
Views: 519

### Re: What is the hamiltonian?

As I understood it, I think the Hamiltonian (H) is the second derivative of the function $\Psi$(x,y,z), which is the change in the function over time.

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