## Search found 30 matches

Sat Mar 12, 2016 1:17 am
Forum: *Alkanes
Topic: Given molecular formula draw line structure
Replies: 1
Views: 368

### Re: Given molecular formula draw line structure

In the problem from our quiz, in which you were given CH3CH2CH(CH2CH3)CH2CH2CH(CH3)2 and asked to draw the line structure, it was easy for me to draw the line structure because the substituents were the parts of the formula in parenthesis so I could visualize the ethyl and methyls as substituents. ...
Mon Feb 29, 2016 3:06 pm
Topic: SN1 vs. SN2
Replies: 2
Views: 852

### Re: SN1 vs. SN2

The S represents Substitution and the N represents Nucleophilic. The 1 means the reaction is unimolecular and so only involves one reactant. The 2 means the reaction is bimolecular and so involves two reactants. So, SN1 and SN2 are both nucleophilic substitution reactions but differ in molecularity.
Mon Feb 22, 2016 4:24 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Arrhenius Equation
Replies: 1
Views: 382

### Re: Arrhenius Equation

When approaching homework problems, is there any way to know whether to use the k = Aexp(-Ea/RT) or ln k = -Ea/RT + ln A form of the Arrhenius Equation for different problems? The two equations are essentially the same thing, but in different forms, so they should both have the same answer when usi...
Tue Feb 16, 2016 4:40 pm
Forum: First Order Reactions
Topic: Difference in First order integrated rate law
Replies: 2
Views: 477

### Re: Difference in First order integrated rate law

They're essentially the same thing, but in different forms. The first formula is just e^ for both sides of the second formula simplified.
Mon Feb 08, 2016 2:28 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Closed/Isolated
Replies: 1
Views: 490

### Re: Closed/Isolated

An isolated system has nothing going in or out of it. The aircraft engine with fuel in it has fuel being used up as energy, but matter is not let out of the engine, so it's a closed system.
Tue Feb 02, 2016 4:55 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Ecell, Nernst Equation
Replies: 1
Views: 535

### Re: Ecell, Nernst Equation

2.303RT/F is a conversion from using ln to using log. So if you use ln, the nerst equ is E=E(not) - RT/nF (ln Q). If you use log, the nerst equ is E=E(not) - 2.303RT/nF (log Q).
Tue Feb 02, 2016 4:51 pm
Forum: Balancing Redox Reactions
Topic: Determining Half Reactions
Replies: 1
Views: 408

### Re: Determining Half Reactions

When determining half reactions, do we look at the charges on the ion or are we looking at the sum of the oxidation numbers in order to decide if it's oxidation or reduction? You figure out the oxidation numbers using the charges on the ions to see whether it's oxidation or reduction. You're lookin...
Mon Jan 25, 2016 9:25 pm
Forum: Calculating Work of Expansion
Topic: Clarification On the Work Formula
Replies: 3
Views: 699

### Re: Clarification On the Work Formula

JLee Disc 1A wrote:I was just wondering if the liters in the work formula for variable pressure cancel each other out or whether it stays in the final answer.

Yes, the liters cancel out in ln(V2/V1)
Mon Jan 25, 2016 9:24 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: Residual Entropy
Replies: 5
Views: 1298

### Re: Residual Entropy

Residual entropy is entropy at T=0 K. You will have to use S=kB lnW to solve it. Degeneracy, W, is #orientations^#molecules. You need Avogadro's # to get molecules.
Mon Jan 18, 2016 10:14 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: Finding Total Degeneracy
Replies: 1
Views: 721

### Re: Finding Total Degeneracy

Why should separate degeneracies be multiplied to find total degeneracy? And what does total degeneracy represent in a system? Degeneracy is the number of ways of achieving a given energy state. S = k lnW, and S depends on degeneracy. Separate degeneracies are multiplied because S1 + S2 = k lnW1 + ...
Mon Jan 18, 2016 10:07 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Degeneracy equation
Replies: 2
Views: 518

### Re: Degeneracy equation

The 2 states are the two areas the particles in the flask can go to. In the diagrams, there is a left area (microstate) and right area (microstate). The calculation won't always use 2. That's just how many possible states there are in the example.
Wed Jan 13, 2016 4:26 pm
Forum: Phase Changes & Related Calculations
Topic: State function
Replies: 2
Views: 367

### Re: State function

804416421 wrote:I'm still a bit lost as of what it means to have a state function. Can anyone clarify?

State functions don't depend on the path taken. Different paths will result in the same answer for state functions.
Wed Jan 13, 2016 4:14 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Internal Energy
Replies: 3
Views: 454

### Re: Internal Energy

What exactly is internal energy and why is it important?
Fri Jan 08, 2016 3:38 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Breaking Double Bonds
Replies: 1
Views: 285

### Re: Breaking Double Bonds

RHong 2J wrote:Why is it necessary to break both bonds in a double bond rather than just break one when doing bond enthalpy problems?

Double bonds involve both sigma and pi bonds, so because of how they are structured when bonded, it's necessary to break both bonds in order to make new bonds.
Fri Jan 08, 2016 3:35 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond Enthalpy
Replies: 1
Views: 298

### Re: Bond Enthalpy

When calculating bond enthalpy, how do we know exactly which bonds are breaking and which bonds are forming? Thank you. It helps to draw the Lewis structures of each molecule involved in the chemical reaction to see which bonds need to break in the reactants in order to make new bonds to make the p...
Thu Dec 03, 2015 5:59 pm
Forum: *Making Buffers & Calculating Buffer pH (Henderson-Hasselbalch Equation)
Topic: Salts' Function In Buffers
Replies: 3
Views: 561

### Re: Salts' Function In Buffers

The pH has to do with the concentration of H+, not the concentration of the conjugate base. pH=-log[H+]
Mon Nov 23, 2015 11:53 pm
Forum: Identifying Acidic & Basic Salts
Topic: Exceptions of anions
Replies: 2
Views: 499

### Re: Exceptions of anions

Hee Sang Kim 4I wrote:Why were HSO4- and H2PO4- exceptions from anions making solution basic again?

They can make solutions acidic because they are able to give off a proton, H+.
Thu Nov 19, 2015 6:05 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Concentrations
Replies: 1
Views: 369

### Re: Concentrations

Is there a mathematical example to show that final equilibrium concentrations of [O2]/[O3] would be different when starting with different initial concentrations of each, while K, which depends on the expression [O2]^3/[O3]^2 is constant? (Problem 11.11 part C) If you solve for K, the ratio of [O2]...
Mon Nov 09, 2015 8:18 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: When to use P in finding K and Q
Replies: 1
Views: 434

### Re: When to use P in finding K and Q

Many of the Homework problems form chapter 11 ask us to write the equilibrium expression K for reactions or write the reaction quotient Q. In the answers to these problems sometimes they are written using P and sometimes they are not. When do we use P and when do we not? For example problem number ...
Mon Nov 09, 2015 8:11 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordination sphere
Replies: 1
Views: 365

### Re: Coordination sphere

On the course reader it states that the number of bonds equal the coordination number. But I remember during lecture it was mentioned that it is always not the case. What are some of the exceptions where the number of bonds don't equal the coordination number? Actually, the number of bonds do equal...
Mon Nov 02, 2015 4:52 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Cis and trans form of tetrahedral complex
Replies: 1
Views: 363

### Re: Cis and trans form of tetrahedral complex

Izzy Ick 4B wrote:Besides structural, what are the differences in between the cis and trans form of a tetrahedral complex?

The polarity will be different, so they will react differently.
Mon Nov 02, 2015 12:55 am
Forum: Administrative Questions and Class Announcements
Topic: Midterm
Replies: 1
Views: 635

### Midterm

On the detailed solutions for previous midterm exams in the course reader, points given are shown. I noticed that points are given for a lot of separate steps. Do we actually have to write out all of those steps to get full credit? When I work through problems, I combine steps to save time. Some of ...
Tue Oct 27, 2015 10:40 pm
Forum: Ionic & Covalent Bonds
Topic: 3.79
Replies: 1
Views: 573

### Re: 3.79

Hi, I have a question about 3.79. The question says: "Compounds having bonds with a high covalent character tend to be less soluble in water than similar compounds that have low covalent character. Use ekectonhgatives to predict which of the following compounds is the more soluble in water: (a...
Tue Oct 27, 2015 10:29 pm
Forum: Lewis Structures
Topic: Drawing a reduced anion
Replies: 2
Views: 527

### Re: Problem 3.103

Problem 3.103 gives the Lewis structure for quinone, C6H4O2, and says it can be reduced to the anion (C6H4O2)2-. Part a says to draw the Lewis structure of the reduced product. How would you know how to draw this? Since the anion has 2 extra electrons, you have to see where you can add those 2 more...
Wed Oct 21, 2015 9:46 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Ionic & Covalent Bond Characteristics
Replies: 1
Views: 440

### Re: Ionic & Covalent Bond Characteristics

In what ways do ionic bonds have covalent bond characteristics? In an ionic bond, the anion's electron is pulled into the bonding region to the cation's positive charge. The spherical electron cloud of the anion becomes distorted toward the cation. This is the tendency of the electron density of th...
Wed Oct 21, 2015 9:25 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Covalent Bond Electrons
Replies: 1
Views: 392

### Re: Covalent Bond Electrons

When observing covalent bonds, do the electrons orbit around both the nuclei or do they stop in-between? The valence electrons (the outer most electrons) are used in bonding, so the rest of the inner electrons would still orbit around the nucleus of the element they were already a part of alone bef...
Wed Oct 14, 2015 5:10 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Negative vs positive energy value
Replies: 1
Views: 5981

### Re: Negative vs positive energy value

For the problem, "An excited hydrogen atom emits light with a frequency of 1.14 x 10^14 Hz to reach the energy level for which n=4. In what principle quantum level did the electron begin?", the answer key in the workbook shows that delta E= Ef-Ei which I understand. However, it then presu...
Wed Oct 14, 2015 5:06 pm
Forum: Photoelectric Effect
Topic: Fall 2014 Quiz 1 Preparation question 10
Replies: 1
Views: 403

### Re: Fall 2014 Quiz 1 Preparation question 10

The question asks in what principle quantum level did the electron begin and it gives the frequency of the light emitted, 1.14*10^{14} Hz , as well as the final energy level, n=4. When I solve for n after plugging in all of the constants and givens I get n=3.21 instead of the answer n=6. I don't un...
Wed Oct 07, 2015 7:11 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Effective nuclear charge
Replies: 2
Views: 406

### Re: Effective nuclear charge

Why is the effective nuclear charge in the p-orbital less than the effective nuclear charge in the s-orbital if they are both in the same shell? The effective nuclear charge is the electrostatic attraction that electrons feel from the positive nucleus. Outer electrons would feel a REDUCED attractio...
Wed Oct 07, 2015 6:51 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Exceptions when writing e- configurations
Replies: 3
Views: 622

### Re: Exceptions when writing e- configurations

The electron configuration for Copper is an exception so it is [Ar]3d^10 4s^1. If Copper gained an electron, would it be added back to 4s to make it [Ar]3d^10 4s^2? Also, in lecture we were discussing how if you lose an electron, you remove the most recent electron you drew or the outermost e-. Doe...