## Search found 26 matches

Thu Mar 16, 2017 1:30 am
Forum: Administrative Questions and Class Announcements
Topic: Lecture on Friday
Replies: 2
Views: 405

### Lecture on Friday

Since there is no material left to cover, I was wondering if there is going to be a lecture on Friday.
Mon Mar 06, 2017 10:37 am
Forum: Administrative Questions and Class Announcements
Topic: Final Exam points
Replies: 7
Views: 1004

### Final Exam points

In the front of the course reader it says the final exam is worth 160 points, but all of the previous finals have been 170 points. Does anyone know if it's worth 160 points or 170?
Thu Mar 02, 2017 1:04 pm
Forum: *Organic Reaction Mechanisms in General
Topic: HBr example from lecture
Replies: 2
Views: 424

### HBr example from lecture

In lecture Dr. Lavelle talks about an example where a HBr molecule is broken and attached to a hydrocarbon. In the example he always attaches the H+ ion first to the hydrocarbon and then the Br- to the hydrocarbon. Does the order that the ions are attached matter? And if it does, then why is the H+ ...
Thu Feb 23, 2017 8:04 pm
Forum: Administrative Questions and Class Announcements
Topic: Quiz 2 Winter 2017
Replies: 160
Views: 17170

### Re: Quiz 2 Winter 2017

Do we have to know how to draw any graphs for quiz 2?
Tue Feb 14, 2017 10:17 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Determining 1st, 2nd, or 3rd Order
Replies: 1
Views: 340

### Determining 1st, 2nd, or 3rd Order

In the course reader it says to make only one reactant's concentration variable and the other's constant. Then it says that n (order) is determined by the plot. (Ln([A])=1st order, 1/[A]=2nd order, and [A]=zero order) How would we find the plot to determine the order? or would we be given the plot a...
Fri Feb 10, 2017 3:01 pm
Forum: Balancing Redox Reactions
Topic: OH- H+ and H2O in balancing redox reactions
Replies: 5
Views: 6515

### OH- H+ and H2O in balancing redox reactions

When balancing redox reactions, H2O and OH- are always used to balance the O and H in the RXN. Why isn't H+ used to balance the RXN?
Thu Feb 02, 2017 11:21 pm
Forum: Phase Changes & Related Calculations
Topic: signs of delta H
Replies: 3
Views: 1048

### Re: signs of delta H

I know for an exothermic system delta H is negative, but if the question is asking for the quantity of that heat, would the quantity be positive?

For example, if delta H= -1500kJ/mol, would we say that 1500kJ/mol is removed from the system?
Thu Feb 02, 2017 7:59 pm
Forum: Phase Changes & Related Calculations
Topic: signs of delta H
Replies: 3
Views: 1048

### signs of delta H

If a question asks how much heat is removed from a system, would the answer always be positive?
I found delta H and it was negative, so I don't know if I keep it as a negative, or make it a positive cause it is asking for how much heat and not the change in heat.
Thu Feb 02, 2017 7:52 pm
Forum: Phase Changes & Related Calculations
Topic: Practice Quiz 1 #9
Replies: 2
Views: 345

### Re: Practice Quiz 1 #9

I think that since it says the reaction is an isothermal reaction, any energy that is lost from doing work is replaced in the form of heat from the surroundings. Since delta S(sys)= delta H(sys)/T, as T decreases, delta S(sys) increases to become positive.
Fri Jan 27, 2017 11:25 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Qv and Qp in delta U equations [ENDORSED]
Replies: 2
Views: 26479

### Re: Qv and Qp in delta U equations[ENDORSED]

Thank you so much it makes so much sense now.
Fri Jan 27, 2017 11:21 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Ideal gas.
Replies: 1
Views: 264

### Ideal gas.

In the course reader it says that delta U= 3/2 nR(delta T)=0. Is this just for when the system is at equilibrium so all the heat lost is replaced (delta T=0)? If not then why is this equation true?
Fri Jan 27, 2017 10:58 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Degeneracy
Replies: 4
Views: 706

### Degeneracy

Can someone please explain what degeneracy is? I don't understand what it is or why it is related to entropy.
Fri Jan 20, 2017 8:49 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Qv and Qp in delta U equations [ENDORSED]
Replies: 2
Views: 26479

### Qv and Qp in delta U equations[ENDORSED]

What do Qv and Qp stand for and how do you find the Qv and Qp?
Fri Jan 13, 2017 2:42 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Methods of Determining Enthalpy
Replies: 1
Views: 238

### Methods of Determining Enthalpy

Why are there so many methods to finding enthalpy and how do I know which method should be used?
Wed Nov 30, 2016 7:55 pm
Forum: *Titrations & Titration Calculations
Topic: Moles in sample and titrate
Replies: 1
Views: 352

### Moles in sample and titrate

During lecture Dr. Lavelle keeps saying that the moles of the titrate is equal to the moles of the sample. Why is this true?
Wed Nov 23, 2016 3:31 pm
Forum: Conjugate Acids & Bases
Topic: Autorpotolysis Note(pg 156 Course Reader)
Replies: 1
Views: 461

### Autorpotolysis Note(pg 156 Course Reader)

In the course reader there is a note on page 156 that says if [H3O]+ < 10^(-7) then solution is considered neutral because we know that autorpotolysis generates 10^-7 mol/L H3O+. Can someone please explain what this means.
Tue Nov 15, 2016 11:32 pm
Forum: Ideal Gases
Topic: Ice Box Change in Concentrations
Replies: 2
Views: 560

### Ice Box Change in Concentrations

When we make the ice box, if there are two products/reactants we say that they have the same change in concentration. For example 2NO<=>N2+O2. The change in N2 and O2 would both be x, but why do they have the same change in concentration?
Tue Nov 08, 2016 8:44 pm
Forum: Naming
Topic: (en)2 naming
Replies: 3
Views: 424

### (en)2 naming

In the 1st practice quiz for quiz 3 in the workbook, number 3 has (en)2 in the chemical formula. The answer gives it the name bisethylenediamine. Why is it named like this?
Thu Nov 03, 2016 9:37 am
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: sigma and pi bonds in p orbital
Replies: 1
Views: 345

### sigma and pi bonds in p orbital

In the p orbitals, px and py are pi bonds and pz is sigma bonds. Why are there two pi bonds and one sigma bond, and why is it the pz orbital that has the only sigma bond?
Wed Oct 26, 2016 2:09 pm
Forum: Sigma & Pi Bonds
Topic: Hybridization question
Replies: 1
Views: 339

### Hybridization question

In the Wednesday lecture he showed us that the Carbon atom had its valence electrons placed in these orbitals: two electrons in the s orbital, one electron in the px and py orbitals, and an empty pz orbital. Why can't the H electrons just fill the empty pz orbital and the rest of the px and py ones?
Tue Oct 18, 2016 5:00 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Ch. 2 Textbook Question 45d. [ENDORSED]
Replies: 1
Views: 392

### Ch. 2 Textbook Question 45d.[ENDORSED]

Which elements are predicted to have the following ground-state electron configurations. d) [Rn]7s^2 6d^2 In the periodic table in the textbook both thorium and rutherfordium have this configuration, but the solutions manual says that the answer is thorium. How do I know which one it is if they have...
Tue Oct 18, 2016 4:15 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Practice Quiz #8
Replies: 2
Views: 394

### Re: Practice Quiz #8

Thank you. That makes sense.
Thu Oct 13, 2016 7:48 pm
Forum: Quantum Numbers and The H-Atom
Topic: Atomic Spectra question 1.11 [ENDORSED]
Replies: 3
Views: 603

### Re: Atomic Spectra question 1.11[ENDORSED]

Thank you for explaining it. I found the picture and it makes sense now.
Thu Oct 13, 2016 7:45 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Practice Quiz #8
Replies: 2
Views: 394

### Practice Quiz #8

On the second practice quiz for quiz #1 in the workbook #8 asks what is the wavelength of the radiation emitted when an electron transitions from n=4 to n=3? For my answer I got -1875 nm, but the answer is 1875 nm. Why is it positive? Here is my work: E=-hR/(4)^2= -1.3624x10^-19 E=-hR/(3)^2= -2.4220...
Thu Oct 06, 2016 11:05 pm
Forum: Quantum Numbers and The H-Atom
Topic: Atomic Spectra question 1.11 [ENDORSED]
Replies: 3
Views: 603

### Atomic Spectra question 1.11[ENDORSED]

Could someone please explain to me the answer to Chapter 1 homework question 1.11 Q. 1.11: In the spectrum of atomic hydrogen, several lines are generally classified together as belonging to a series (for example, Balmer series, Lymann series, Paschen series), as shown in Figs. 1.10 and 2.1. What is...
Tue Sep 27, 2016 7:42 pm
Forum: Student Social/Study Group
Topic: Chemistry Jokes
Replies: 31
Views: 5178

### Re: Chemistry Jokes

What is the chemical formula for coffee? Co(Fe)2 If H2O is the formula for water, what is the formula for ice? H2O cubed Why did the chemist sole and heel his shoes with silicone rubber? To reduce his carbon footprint. What happened to the man who was stopped for having NaCl and a nine-volt in his c...