## Search found 22 matches

Mon Mar 06, 2017 9:16 pm
Forum: Administrative Questions and Class Announcements
Topic: Quiz 3 Winter 2017
Replies: 183
Views: 20031

### Re: Quiz 3 Winter 2017

In the organic chemistry text book, there are several assigned homework problems that have to do with identifying and naming alkenes and cycloalkenes. 1.25-1.29 ask to name this alkene or draw a structure of (Z)-3-methyl-3-heptene. I thought the quiz was only over alkanes and cycloalkanes but is th...
Sun Mar 05, 2017 7:54 pm
Forum: *Electrophiles
Topic: Electrophiles and Nucleophiles for Quiz 3
Replies: 3
Views: 1068

### Re: Electrophiles and Nucleophiles for Quiz 3

I think it's good to be able to identify them but also know the strengths since the assigned readings do cover it, even though it wasn't emphasized in lecture.
Wed Feb 22, 2017 10:05 am
Forum: First Order Reactions
Topic: Calculating Half-life
Replies: 2
Views: 642

### Re: Calculating Half-life

A tip to know when to use which equation is to look at what you're given. Since the initial and final concentrations are not mentioned, you can infer that the equation t1/2 = 0.693/k is what you need to use to find the half life.
Wed Feb 08, 2017 9:12 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: HW 14.5 a [ENDORSED]
Replies: 3
Views: 468

### Re: HW 14.5 a[ENDORSED]

#14.15 in the textbook part a mentions solubility equilibrium as well and I'm also not sure what it means.
Part b also means a Bronsted neutralization reaction and I also don't know what that one is if anyone else does?
Tue Jan 31, 2017 12:51 pm
Forum: Administrative Questions and Class Announcements
Replies: 130
Views: 17454

### Re: Quiz 1 Preparation Answers

For number 3, what equation do we use since there seems to be a change in pressure? I can't seem to get the answer posted here by any method I've tried. Thanks. Use w=-nRT ln V2/V1 So then you'd get -(2.00 mol)(8.314 J/K mol)(300 K)(ln 18.00/6.00) to get -5480 J or -5.48 kJ. how do you then find th...
Sat Jan 28, 2017 3:58 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Energy Extensive or Intensive?
Replies: 2
Views: 19286

### Re: Energy Extensive or Intensive?

Extensive properties depend on the amount of material or the size of the sample (moles, mass, volume, etc.). Intensive properties, on the other hand, do NOT depend on the the amount of material available, like density, pressure, color, etc. Energy does depend on the amount of stuff in the system, so...
Mon Jan 23, 2017 10:06 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat Capacity of Gases
Replies: 2
Views: 437

### Re: Heat Capacity of Gases

I would assume so. Unless the problem is asking you to solve for it, there should be a chart or something with all the values.
Sun Jan 15, 2017 3:28 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard Reaction Enthalpy
Replies: 1
Views: 254

### Re: Standard Reaction Enthalpy

Because O2 is in its standard state as a gas, or its most stable form, no change occurs in the formation of it. Dr. Lavelle gave the example of H2(g) ---> H2(g), where delta H, or the standard reaction enthalpy, is 0 since no change occurs. The course reader also states that the definition of the st...
Wed Nov 30, 2016 12:22 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Identifying a strong acid
Replies: 6
Views: 1496

### Re: Identifying a strong acid

omg such a helpful pneumonic! will definitely be using this thanks :)
Tue Nov 22, 2016 1:42 pm
Forum: Conjugate Acids & Bases
Topic: What does a conjugate acid/base do? [ENDORSED]
Replies: 4
Views: 1010

### Re: What does a conjugate acid/base do?[ENDORSED]

This also confused me a little, but reading the textbook helped clarify. In the example of HCO3- + O2-, HCO3- loses its H and donates it to O2- so it becomes OH- and HCO3- becomes CO3-. HCO3- is the Bronsted acid because it donated a proton, and O2- is the Bronsted base because it accepted a proton....
Wed Nov 16, 2016 9:55 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Identifying Polydentates? [ENDORSED]
Replies: 8
Views: 1256

### Re: Identifying Polydentates?[ENDORSED]

In regards to the coordination number, if a molecule is bidentate, then it can bond with the central atom in 2 places, so you consider that as a 2 when adding up the coordination number of the compound. If it's tridentate, then it would be 3, and so on. If it's written like (en)2 then you would mult...
Wed Nov 16, 2016 9:53 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Identifying Polydentates? [ENDORSED]
Replies: 8
Views: 1256

### Re: Identifying Polydentates?[ENDORSED]

I also have trouble with this, but I know looking at the lewis structure helps a lot. In the example of ethylenediamine, once you draw the structure you can see that the two "N's" in the NH2 have a lone pair that can form a bond, hence en is bidentate. Dien is tridendate because the 3 &quo...
Sun Nov 13, 2016 7:35 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Textbook 11.31
Replies: 2
Views: 400

### Re: Textbook 11.31

Yes, I realized this a little while after posting it and felt a little dumb, but left this up in case anyone else was also initially confused. Thank you!!
Fri Nov 11, 2016 9:10 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Textbook 11.31
Replies: 2
Views: 400

### Textbook 11.31

In this problem, part c asks if there's a tendency to form more reactants or products. After determining the reaction quotient, it comes out to be that Q < K. The solutions manual says "Because Q < K, more products will be formed." Is it not the other way around? On page 135 of our course ...
Wed Nov 02, 2016 10:56 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Midterm 2015 #4
Replies: 1
Views: 384

### Midterm 2015 #4

On practice midterm 2015 #4, we are supposed to draw the molecule XeF2 and name its shape and angle. Xe ends up having 3 lone pairs while bonded to the 2 flourines, and the shape of this is linear with 180 degree angles. I don't quite understand how a molecule with 3 lone pairs and 2 atoms could sti...
Wed Oct 26, 2016 9:38 pm
Forum: Resonance Structures
Replies: 2
Views: 449

### Re: Resonance Course Reader Example

You only need to draw all of the resonance structures if the question asks you to. If the question asked for the most stable resonance structure, until you draw all of them and calculate all the formal charges, you wouldn't necessarily know that the first one you draw is the most stable. I suppose i...
Wed Oct 26, 2016 9:30 pm
Forum: Ionic & Covalent Bonds
Topic: Bond Angles?
Replies: 2
Views: 700

### Re: Bond Angles?

I was wondering the same thing and just wanted to say that was super helpful. Thanks!
Fri Oct 21, 2016 6:32 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Angles of molecular shapes
Replies: 5
Views: 953

### Angles of molecular shapes

A molecule like BF3, or Boron Triflouride, has angles of 120 degrees, which makes sense considering it's trigonal planar so the 3 F atoms are equally spaced out around the Boron. But for a molecule like CH4, methane, the H-C-H angles are 109.5, which seems a bit random. I visually see why that makes...
Tue Oct 11, 2016 4:30 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8223
Views: 1435192

### Re: Post All Chemistry Jokes Here

Why does hamburger yield lower energy than steak?
Because it's in the ground state.
Fri Oct 07, 2016 6:29 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Emittance versus Absorption in Atomic Spectra [ENDORSED]
Replies: 1
Views: 380

### Re: Emittance versus Absorption in Atomic Spectra[ENDORSED]

Hi!
An electron emits light when traveling from a higher energy level to a lower energy level, like from n=4 to n=2. Energy is absorbed when an electron moves from a lower energy level to a higher energy level.

Hope this helps!
Fri Oct 07, 2016 6:05 pm
Forum: SI Units, Unit Conversions
Topic: Conversions [ENDORSED]
Replies: 8
Views: 1221

### Re: Conversions[ENDORSED]

This number is on the back of the periodic table from the Course Reader Store along with all the other constants so I would imagine that we don't need to memorize it.
Fri Sep 30, 2016 8:41 pm
Forum: Properties of Light
Topic: Wavelength, Frequency, Amplitude, & Intensity
Replies: 4
Views: 3936

### Re: Wavelength, Frequency, Amplitude, & Intensity

For this experiment, the original thought was that increasing the intensity of light with longer wavelengths would cause electrons to be emitted from the metal. What they found was that longer wavelengths were unsuccessful at this task, no matter the intensity (# of photons emitted) or brightness of...