Search found 22 matches

by Julia Hwang 3G
Mon Mar 06, 2017 9:16 pm
Forum: Administrative Questions and Class Announcements
Topic: Quiz 3 Winter 2017
Replies: 183
Views: 15876

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...
by Julia Hwang 3G
Sun Mar 05, 2017 7:54 pm
Forum: *Electrophiles
Topic: Electrophiles and Nucleophiles for Quiz 3
Replies: 3
Views: 796

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.
by Julia Hwang 3G
Wed Feb 22, 2017 10:05 am
Forum: First Order Reactions
Topic: Calculating Half-life
Replies: 2
Views: 438

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.
by Julia Hwang 3G
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: 371

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?
by Julia Hwang 3G
Tue Jan 31, 2017 12:51 pm
Forum: Administrative Questions and Class Announcements
Topic: Quiz 1 Preparation Answers
Replies: 130
Views: 13715

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...
by Julia Hwang 3G
Sat Jan 28, 2017 3:58 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Energy Extensive or Intensive?
Replies: 2
Views: 1588

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...
by Julia Hwang 3G
Mon Jan 23, 2017 10:06 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat Capacity of Gases
Replies: 2
Views: 360

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.
by Julia Hwang 3G
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: 210

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...
by Julia Hwang 3G
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: 1065

Re: Identifying a strong acid

omg such a helpful pneumonic! will definitely be using this thanks :)
by Julia Hwang 3G
Tue Nov 22, 2016 1:42 pm
Forum: Conjugate Acids & Bases
Topic: What does a conjugate acid/base do? [ENDORSED]
Replies: 4
Views: 867

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....
by Julia Hwang 3G
Wed Nov 16, 2016 9:55 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Identifying Polydentates? [ENDORSED]
Replies: 8
Views: 963

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...
by Julia Hwang 3G
Wed Nov 16, 2016 9:53 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Identifying Polydentates? [ENDORSED]
Replies: 8
Views: 963

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...
by Julia Hwang 3G
Sun Nov 13, 2016 7:35 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Textbook 11.31
Replies: 2
Views: 285

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!!
by Julia Hwang 3G
Fri Nov 11, 2016 9:10 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Textbook 11.31
Replies: 2
Views: 285

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 ...
by Julia Hwang 3G
Wed Nov 02, 2016 10:56 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Midterm 2015 #4
Replies: 1
Views: 310

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...
by Julia Hwang 3G
Wed Oct 26, 2016 9:38 pm
Forum: Resonance Structures
Topic: Resonance Course Reader Example
Replies: 2
Views: 354

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...
by Julia Hwang 3G
Wed Oct 26, 2016 9:30 pm
Forum: Ionic & Covalent Bonds
Topic: Bond Angles?
Replies: 2
Views: 455

Re: Bond Angles?

I was wondering the same thing and just wanted to say that was super helpful. Thanks!
by Julia Hwang 3G
Fri Oct 21, 2016 6:32 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Angles of molecular shapes
Replies: 5
Views: 786

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...
by Julia Hwang 3G
Tue Oct 11, 2016 4:30 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7582
Views: 1015251

Re: Post All Chemistry Jokes Here

Why does hamburger yield lower energy than steak?
Because it's in the ground state.
by Julia Hwang 3G
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: 292

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!
by Julia Hwang 3G
Fri Oct 07, 2016 6:05 pm
Forum: SI Units, Unit Conversions
Topic: Conversions [ENDORSED]
Replies: 8
Views: 1005

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.
by Julia Hwang 3G
Fri Sep 30, 2016 8:41 pm
Forum: Properties of Light
Topic: Wavelength, Frequency, Amplitude, & Intensity
Replies: 4
Views: 3130

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...

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