## Search found 32 matches

Sun Mar 19, 2017 9:53 am
Forum: General Rate Laws
Topic: Homework 15.65 part C
Replies: 2
Views: 770

### Re: Homework 15.65 part C

This is because the rate constant, k, increases exponentially as temperature, T, increases. Therefore, the rate constant for the forward reaction that correlates with the larger activation potential will increase more so than the smaller rate constant for the reverse reaction. This would also mean t...
Wed Mar 15, 2017 8:10 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 2015 Final 5A
Replies: 4
Views: 572

### Re: 2015 Final 5A

For the ln in the NERNST equation, you know that you need to put a 1 in the numerator and either 20 and 30 in the denominator, respectively, because the problem tells you that the concentration of ions on the inside of the cell is about 20 to 30 times that of the concentration outside. We know that ...
Wed Mar 08, 2017 5:57 pm
Forum: Administrative Questions and Class Announcements
Topic: Torsional Strain
Replies: 2
Views: 482

### Re: Torsional Strain

When considering the conformations of molecules (e.g. alkanes, alkenes, and alkynes), torsional strain is defined as the force that opposes rotation of a part of a molecule about a bond. Today, Dr. Lavelle used the analogy of a wrench as an example to demonstrate what it is similar to; think of the ...
Wed Mar 01, 2017 10:17 am
Forum: *Organic Reaction Mechanisms in General
Topic: Pseudo-Equilibrium Constant
Replies: 1
Views: 372

### Re: Pseudo-Equilibrium Constant

The pseudo equilibrium constant is not the actual equilibrium constant, it is more of a reference point for the reaction as it reaches equilibrium. The concentration of the activated complex of AB is used because the equation states A + B -> AB -> C. Consider the reaction profile graph, in which in ...
Sun Feb 26, 2017 4:42 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Reaction Mechanisms and Orders
Replies: 1
Views: 310

### Re: Reaction Mechanisms and Orders

When writing a rate law, the reaction order corresponds to the degree of the concentration. If the concentration of any given element is raised to an exponential power, that power is its order, and this is determined by the number of moles of the element present in the reaction (thus generally occur...
Mon Feb 20, 2017 8:37 am
Forum: General Rate Laws
Topic: Stoichiometric coefficients
Replies: 1
Views: 303

### Re: Stoichiometric coefficients

Stoichiometric coefficients, or the number of moles of a product or reactant, affects K and Q values. When determining the exponents for each reactant in a rate law, you must analyze information given about the concentration of each reactant and its correlation to the corresponding rate.
Wed Feb 15, 2017 4:22 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Molar Entropies
Replies: 4
Views: 516

### Re: Molar Entropies

It depends primarily on the conditions that they are asking you about the entropy under. If they are asking you about entropy at 0 K, there is no thermal entropy to consider, therefore only residual entropy needs to be accounted for (this is based off of the number of positions/ arrangements for a m...
Wed Feb 15, 2017 4:19 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Winter Midterm 2014 QB
Replies: 3
Views: 540

### Re: Winter Midterm 2014 QB

Benzene has the chemical formula C6H6, while hexane has the chemical formula C6H14. Because they are asking you about the molar entropy at 25 C, we have to take into account thermal entropy (rather than residual/ positional entropy) and the fact that hexane would have more thermal entropy because it...
Wed Feb 15, 2017 10:54 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: DeltaG standard formation values
Replies: 1
Views: 281

### Re: DeltaG standard formation values

Yes, however it is not true for entropy values at standard conditions.
Sun Feb 12, 2017 8:24 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Question 7 on Midterm 2013
Replies: 2
Views: 342

### Re: Question 7 on Midterm 2013

You somewhat answered your question in your question. We switch the reaction involving Mn because it is the oxidation half reaction, meaning that the charge of the products is being reduced and therefore that the electrons must be on the right side of the equation. Switching this equation also allow...
Sun Feb 12, 2017 8:17 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Winter 2016 Midterm Q1A
Replies: 2
Views: 480

### Re: Winter 2016 Midterm Q1A

The arrows that point to and from the same element have been added to assist you in identifying which bonds are broken and formed; this means that they are trying to highlight important bonding sites in which the bonds in the products differ from those in the reactants. You can still do the problem ...
Wed Feb 08, 2017 8:57 am
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8223
Views: 1435006

### Re: Post All Chemistry Jokes Here

A photon checks into a hotel and is asked if he needs any help with his luggage.
He says, "No, I'm traveling light."
Wed Feb 08, 2017 8:56 am
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8223
Views: 1435006

### Re: Post All Chemistry Jokes Here

Did you hear about the man who got cooled to absolute zero?

He's 0K now.
Fri Jan 27, 2017 10:20 am
Forum: Phase Changes & Related Calculations
Topic: Homework Question 9.25
Replies: 1
Views: 348

### Re: Homework Question 9.25

Based on the molecule S02F2, there are six possible configurations of the four attached atoms around the central atom, S. Since we know that there are six possible arrangements, we can deduce that the degeneracy of this molecule is W=6, where W is degeneracy. The problem cites one molecule, SO2F2, s...
Fri Jan 27, 2017 10:13 am
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Delta U
Replies: 2
Views: 467

### Re: Delta U

Delta U is the change in internal energy of a system. The change in internal energy (dU) is equal to q+w, where q is the heat lost or gained and w is the work done on or by the system. (du=q+w) In the instance that the process occurs under constant pressure, du=dH+w, because qp=dH. If the process oc...
Sat Jan 21, 2017 10:27 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Reversible vs irreversible process
Replies: 2
Views: 437

### Re: Reversible vs irreversible process

In an irreversible reaction, the reactants convert to products, but the products cannot convert back to reactants (think of combustion, in which oxygen gas is burned with a compound; this process cannot be reverted/ reversed). In a reversible reaction the reactants and products are never fully consu...
Sat Jan 21, 2017 10:17 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Calorimeters [ENDORSED]
Replies: 1
Views: 335

### Re: Calorimeters[ENDORSED]

A "mock" calorimeter can actually be made out of any simple, insulating material (such as styrofoam). A common chemistry experiment involves creating a coffee cup calorimeter, literally making a calorimeter out of a styrofoam cup because the material acts as a good insulator. Bomb calorime...
Fri Jan 20, 2017 8:25 am
Forum: General Science Questions
Topic: Conservation of Energy Question
Replies: 1
Views: 376

### Re: Conservation of Energy Question

If the system to which you are referring is an isolated system, then yes, the mass of the entire system would remain the same despite shifts in state. This is because neither mass nor heat can escape the system and be emitted to the surroundings.
Thu Jan 12, 2017 12:01 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Help on HW 8.57
Replies: 4
Views: 840

### Re: Help on HW 8.57

The problem states specifically that we are finding the reaction enthalpy for the hydrogenation of ethyne and ethane. Hydrogenation is a process in which hydrogen and another compound/ substance react with each other; as a result, double bonds are converted to single bonds which "hardens" ...
Sat Dec 03, 2016 10:45 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Replies: 1
Views: 320

### Re: Example in Course Reader

First, you need to right the equation for the reaction and then balance the equation. Once you have done that, you will have the correct molar ratios for this reaction (N2 (g) + 3H2 (g) <-> 2NH3 (g)). We are given the equilibrium concentration of NH3, therefore right that value in your ICE table in ...
Sat Dec 03, 2016 10:29 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: 2007 Final Question 5B
Replies: 2
Views: 464

### Re: 2007 Final Question 5B

Did the solution also calculate Kp? It could be that the solution is trying to test if the reaction is at equilibrium or not. Q and Kp are calculated the same way, so calculating Q would theoretically be like calculating Kp if only a single condition/ state of the reaction is given. Either way, the ...
Sat Dec 03, 2016 10:26 pm
Forum: *Titrations & Titration Calculations
Topic: 2012 Final Exam Q7B
Replies: 2
Views: 856

### Re: 2012 Final Exam Q7B

This titration takes place between a weak acid and a strong base, therefore at the stoichiometric point the moles of the base added = the moles of acid in the sample (i.e. moles of HCOOH = moles of NaOH added) . Once we know this, we can derive the amount of moles of HCOO- based on molar ratios and ...
Sat Nov 26, 2016 10:04 pm
Forum: Identifying Acidic & Basic Salts
Topic: Acidic Salts
Replies: 3
Views: 841

### Re: Acidic Salts

I believe that anilinium chloride would still lower the pH of a solution because it is still an acidic salt, even with the presence of Cl-.
Wed Nov 23, 2016 10:44 am
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Higher/lower energy in a MO diagram?
Replies: 4
Views: 763

### Re: Higher/lower energy in a MO diagram?

Rachel's response is correct. The reason why the orbitals for N and O going are uneven with each other is because O is more electronegative than N. Because of is more electronegative than N, the orbitals require more energy to fill or remove electrons from, which is why they are located higher than ...
Mon Nov 14, 2016 1:41 pm
Forum: Naming
Topic: Writing the formula of coordinate compounds
Replies: 1
Views: 426

### Re: Writing the formula of coordinate compounds

When writing out the name of a compound, not the formula, ligand names are always written alphabetically in regard to the actual ligand, not the prefix indicating the number of ligands. In the course reader, writing chloro after ammine is correct because C comes after A. In the textbook, the compoun...
Mon Nov 07, 2016 1:35 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Ligand formation
Replies: 1
Views: 261

### Re: Ligand formation

Ligands are defined as Lewis bases attached to the central metal atom or ion in a d-metal complex (a complex being a species consisting of a central metal atom or ion to which a number of molecules or ions are attached by coordinate covalent bonds). Ligands can be either ions or molecules and they u...
Wed Nov 02, 2016 10:19 pm
Forum: Hybridization
Topic: Bond Character of Fluorine
Replies: 1
Views: 499

### Bond Character of Fluorine

What would be the bond character of fluorine involved in a sigma bond, for example in CH3F? I attended a review session this past weekend in which the TA told me that the sigma bond characteristics between the carbon and fluorine atoms would be (C 2sp3,F 2p), respectively. His explanation for not ha...
Mon Oct 24, 2016 1:12 pm
Forum: Trends in The Periodic Table
Topic: Effective Nuclear Charge
Replies: 2
Views: 1071

### Re: Effective Nuclear Charge

The effective nuclear charge (Zeff) is defined as the net nuclear charge after taking into account the shielding caused by other electrons in the atom. Zeff changes as the number of electrons in the atom changes; therefore, if there are fewer electrons in the lower energy orbitals, there will be les...
Mon Oct 24, 2016 12:56 pm
Forum: Lewis Structures
Topic: Lewis Structure for Perchlorate Ion [ENDORSED]
Replies: 2
Views: 564

### Re: Lewis Structure for Perchlorate Ion[ENDORSED]

Cl can have an expanded octet, and therefore form multiple double bonds with the oxygen atoms, because of its location in period 3 which allows for "extra" valence electrons to occupy (or "overflow" into) the 3d orbital. Cl's, and numerous other atoms in period 3 and other succee...
Thu Oct 13, 2016 3:11 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: What does Heisenberg Indeterminacy indicate with respect to the “randomness” of the electrons that are near nucleus
Replies: 3
Views: 510

### Re: What does Heisenberg Indeterminacy indicate with respect to the “randomness” of the electrons that are near nucleus

The Heisenberg Indeterminacy Principle accounts for the fact that because we can never know the exact position and momentum (mass times the velocity) of a particle at any given time, there is still a way to estimate or consider those characteristics of a particle but to a certain extent. This indete...
Sat Oct 08, 2016 1:35 pm
Forum: DeBroglie Equation
Topic: 1.37 [ENDORSED]
Replies: 2
Views: 437

### Re: 1.37[ENDORSED]

Yes, you are correct. There wavelengths are so close to each other in length, that the difference between the two is nearly indistinguishable (or rather, is indistinguishable to three sig. figs.). Your calculations are correct, therefore your answer would be that there is (almost) no noticeable diff...
Thu Sep 29, 2016 12:05 am
Forum: Significant Figures
Topic: Constants and Significant Figures
Replies: 3
Views: 1275

### Re: Constants and Significant Figures

Generally speaking, yes, constants should be taken into account for significant figures. To determine how many significant figures to consider, use the number with the least amount of significant figures present, or provided, in a problem. Even though there may be a number with a greater amount of s...