Search found 30 matches

by Silvia Huang 3D
Sat Mar 12, 2016 1:47 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: inert electrodes, galvanic cells
Replies: 1
Views: 324

inert electrodes, galvanic cells

When do we add an inert electrode? Do we add it to only the side that has no metal, or always to both sides even if one of cells already has a metal?

The solution manual seems to be doing it both ways. Is there any rules to this...or does it not really matter??
by Silvia Huang 3D
Thu Mar 10, 2016 12:17 pm
Forum: *Haloalkanes
Topic: polytetrafluorotehylene
Replies: 1
Views: 486

polytetrafluorotehylene

How do you draw the structure of polytetrafluorotehylene? I'm confused about the ethylene part.. isn't ethylene just ethene, but in the answer key, the carbons didn't have a double bond between them.
by Silvia Huang 3D
Wed Mar 09, 2016 8:01 pm
Forum: *Nucleophiles
Topic: alkyl carbanion and aryl carbanion
Replies: 1
Views: 466

alkyl carbanion and aryl carbanion

What are alkyl carbanion and aryl carbanion? They are mentioned in the organic textbook.... It also says carbanions have 8 valence electrons, does that just means the central carbon has a complete octet through bonding with other atoms??
by Silvia Huang 3D
Sat Mar 05, 2016 10:52 pm
Forum: *Alkanes
Topic: Common Names(sec?)
Replies: 1
Views: 242

Common Names(sec?)

What are the common names we need to know for the final?
I know we should know iso, neo and tert since we went over those in detail in class.
What about sec? What's difference between sec and neo... they both look like T-shapes to me.
Is there any other common names we should know?
by Silvia Huang 3D
Mon Feb 29, 2016 9:06 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: activated complex
Replies: 1
Views: 451

activated complex

HW Q15.85 The following rate laws were each derived from an elementary reaction. In each case, write the chemical equation for the reaction, determine its molecularity, and draw a proposed structure for the activated complex. (a) Rate " k[CH3CHO] (Products are CH3 and CHO.) (b) Rate " k[I]...
by Silvia Huang 3D
Sun Feb 28, 2016 10:50 am
Forum: Second Order Reactions
Topic: given half life, calculate time needed
Replies: 3
Views: 871

given half life, calculate time needed

HWQ 15.35 The half-life for the second-order reaction of a substance A is 50.5 s when [A]0 " 0.84 mol!L!1. Calculate the time needed for the concentration of A to decrease to (a) one sixteenth; (b) one-fourth; (c) one-fi fth of its original value. The solution manual calculated k first then use...
by Silvia Huang 3D
Sun Feb 28, 2016 10:06 am
Forum: *Alkenes
Topic: Naming
Replies: 1
Views: 291

Re: Naming

When placing in alphabetic order, prefix such as di, tri etc is not considered.
In this case it's methyl vs. ethyl, so ethyl comes first.
by Silvia Huang 3D
Thu Feb 18, 2016 2:13 pm
Forum: *Nucleophiles
Topic: Nucleophiles vs. Ligand
Replies: 3
Views: 1235

Re: Nucleophiles vs. Ligand

Nucleophile is a molecule that has a region of excess electron density.
Ligand is an ion or molecule attached to a metal atom by sharing electrons.
I guess you can think of ligand as a type of attached nucleophile :P
by Silvia Huang 3D
Fri Feb 12, 2016 8:03 pm
Forum: General Rate Laws
Topic: Given Half life, calculate initial concentration
Replies: 1
Views: 370

Given Half life, calculate initial concentration

HW Q 15.105 To prepare a 15-kg drug for surgery, 150 mg of the anesthetic phenobarbitol is administered intravenously. The reaction in which the anesthetic is metabolized (decomposed in the body) is first order in phenobarbital and has a half-life of 4.5 h. After about 2 h, the drug begins to lose i...
by Silvia Huang 3D
Thu Feb 04, 2016 4:21 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Entropy change when Temperature changes [ENDORSED]
Replies: 5
Views: 518

Entropy change when Temperature changes [ENDORSED]

Can someone please explain when should we use the following two equations? delta S= q / T delta S = nCln (Tf / Ti) I know you should use the second one if temperature changes and the first if temp is constant. However, in hw question 9.5 Even though the temperature changed the first equ is still use...
by Silvia Huang 3D
Fri Jan 29, 2016 10:54 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Galvanic Cell Setup
Replies: 1
Views: 292

Re: Galvanic Cell Setup

Before the electrodes are connected,SO 4 2- ion is present in both solutions. The anode solution contains ZnSO 4 and a zinc metal stripe and the cathode solution contains CuSO 4 and a copper metal strip. Both solutions are neutral. As the anode(Zn) goes through oxidization, it releases Zn 2+ into th...
by Silvia Huang 3D
Sat Jan 23, 2016 2:17 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 8.23 Energy put into heat calorimeter and water
Replies: 1
Views: 276

Re: 8.23 Energy put into heat calorimeter and water

In this question, you want to treat the calorimeter as a whole (including the water inside it and the container/machine itself), because it is asking for heat capacity which does not take volume into consideration, as opposed to specific heat capacity, which is measured per gram or mol. heat capacit...
by Silvia Huang 3D
Sat Jan 16, 2016 11:30 pm
Forum: Calculating Work of Expansion
Topic: W vs w
Replies: 1
Views: 301

Re: W vs w

Capitalized W is degeneracy: the number of ways of achieving a given energy state, (entropy) Lower case w is work: energy transferred in or out of the system. Professor Lavelle mentioned in class that we are used to seeing work as capitalized W in high schools, however, in 14B we'll be using lower c...
by Silvia Huang 3D
Fri Jan 08, 2016 2:39 pm
Forum: Phase Changes & Related Calculations
Topic: Extensive vs. Intensive Property
Replies: 2
Views: 1868

Re: Extensive vs. Intensive Property

intensive property - independent of the size of the sample. Ex: density, temperature, concentration Extensive property - dependent on the size of the sample. Ex: enthalpy, volume and internal energy Intensive properties would have units in the form of x/y, whereas extensive property should just have...
by Silvia Huang 3D
Tue Dec 01, 2015 9:39 pm
Forum: Polyprotic Acids & Bases
Topic: HW 12.77 (Calculating pH of alanine)
Replies: 3
Views: 612

Re: HW 12.77 (Calculating pH of alanine)

Hi, I was wondering if this problem can be done by Ka(overall) = Ka1*Ka2, calculating the initial concentration first then used ka=x^2/ [initial] ?? I got 6.22 :( 0.11 off from the correct answer
by Silvia Huang 3D
Mon Nov 30, 2015 11:16 am
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Why is BF3 an acid?
Replies: 2
Views: 1309

Why is BF3 an acid?

HW question 12.13 draw the lewis structure for each of the following species and identify each as a Lewis acid or Lewis base:
b) BF3

Why is BF3 considered a lewis acid? Doesn't B only have 3 valence electrons and will be stable with 6?
by Silvia Huang 3D
Fri Nov 27, 2015 11:36 am
Forum: Bronsted Acids & Bases
Topic: Drawing the structure of conjugate acid that can be formed
Replies: 1
Views: 405

Drawing the structure of conjugate acid that can be formed

Hw question 12.127 The two strands of the nucleic acid DNA are held together by hydrogen bonding between four organic bases. The structure of one of these bases, thymine, is shown below. (a) How many protons can this base accept? (b) Draw the structure of each conjugate acid that can be formed. (c) ...
by Silvia Huang 3D
Thu Nov 19, 2015 11:34 am
Forum: Naming
Topic: using bis, tris, tetrakis
Replies: 4
Views: 3563

using bis, tris, tetrakis

Can someone please explain when to use bis, tris and tetrakis and give a few examples. I thought you would only use it if the ligand's name had di etc in it, for example 2dien ligands would be biethlyenetriaminetetraacetato?? HW Q11.31 sodium bisoxalato (diaqua) ferrate(III) Why did the solution put...
by Silvia Huang 3D
Tue Nov 17, 2015 5:30 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Biological Importance
Replies: 1
Views: 373

Re: Biological Importance

the equation is basically showing the transport of oxygen by hemoglobin hemoglobin is made up of 4 proteins, each with a heme complex(tetradentate ligand + Fe in the middle). Oxygen molecule is transferred by binding to and then dissociating from the transition metal Fe, which is also bonded to the ...
by Silvia Huang 3D
Fri Nov 13, 2015 2:50 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Given partial pressure, calculate equilibrium constant
Replies: 2
Views: 447

Re: Given partial pressure, calculate equilibrium constant

Thanks Nathan!
That's what I thought too... however, if converting kPa to Pa, shouldn't we times it by 1000 instead of dividing by 100?
by Silvia Huang 3D
Wed Nov 11, 2015 4:15 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Given partial pressure, calculate equilibrium constant
Replies: 2
Views: 447

Given partial pressure, calculate equilibrium constant

HW question 11.89 b
for reaction 2A <-> B + 2C
Partial pressure: A: 18kPa, B: 5kPa, C: 10kPa
Calculate the equilibrium constant

In the solution manual, K= ((5/100)(10/100)^2)/((18/100)^2)
Can you please explain why each partial pressure is divided by 100??
Thank you very much! :)
by Silvia Huang 3D
Fri Nov 06, 2015 2:22 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Ionization energy based on valence- shell e-
Replies: 3
Views: 539

Re: Ionization energy based on valence- shell e-

I think you meant 2e- in pi2px and 1e- in pi2py vs 1e- pi2px and 1e- in pi2px?? because in orbital has px, py and pz, so it can accept 3 pair of electron The atom with paired electron would have a lower higher ionization energy than the atom with unpaired electrons, because of e- repulsion. For exam...
by Silvia Huang 3D
Mon Nov 02, 2015 10:03 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Ionization energy based on valence- shell e-
Replies: 3
Views: 539

Ionization energy based on valence- shell e-

Homework Question 4.67 Base on their valence-shell electron configurations, which of the following species would you expect to have the lowest ionization energy? a) C2 + b) C2 c) C2 - The answer is C2- because its electron is lost from a higher energy level orbital, therefore more easily removed. So...
by Silvia Huang 3D
Sun Nov 01, 2015 3:43 pm
Forum: Hybridization
Topic: What hybrid orbitals are involved
Replies: 1
Views: 258

What hybrid orbitals are involved

Quiz 2 preparation, Question 3
What hybrid orbitals are involved in the C-C sigma bonds and the C-H sigma bonds in benzene?
Can someone please explain what this question is asking??
How is this different from just asking for the hybridization of carbon, which is sp2?
by Silvia Huang 3D
Wed Oct 28, 2015 4:42 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond angles of atoms with lone pair electrons
Replies: 1
Views: 309

Bond angles of atoms with lone pair electrons

Just to clarify, Bent/ Angular (AX2E, AX2E2) has a bond angle of <120 degrees Trigonal Pyramidal (AX3E) has a bond angle of <109.5 degrees but a square planar(AX4E2) would have a bond angle of 90 degrees, because the lone pairs are symmetric and they cancel out?? What about Seesaw, T-shape and squar...
by Silvia Huang 3D
Fri Oct 23, 2015 6:45 pm
Forum: Lewis Structures
Topic: Radicals
Replies: 4
Views: 342

Radicals

HW question 3.55: Which of the following species are radicals?? a) NO2- b)CH3 c)OH d)CH2O I understand that b is a radical, because C has an unpaired electron; however, the answer says that c) OH is also a radical.. Can someone please explain? Doesn't Oxygen have 6 paired electrons and 1 bonded to H...
by Silvia Huang 3D
Thu Oct 15, 2015 11:07 am
Forum: Trends in The Periodic Table
Topic: Exceptions to trends in electron affinity
Replies: 1
Views: 1533

Exceptions to trends in electron affinity

Hi, I have a question about electron affinity. In general electron affinity increase across the period(except for nobel gases with affinity of 0) and decrease down the group; however, N has a negative electron affinity and Be and Mg also have <=0 electron affinities, and why does S have the greatest...
by Silvia Huang 3D
Wed Oct 07, 2015 8:53 pm
Forum: Photoelectric Effect
Topic: Photoelectric effect post-quiz 17-19 [ENDORSED]
Replies: 6
Views: 3646

Re: Photoelectric effect post-quiz 17-19 [ENDORSED]

a) E_{k}=\frac{1}{2}mv^{2}=\frac{1}{2}(9.10956*10^{-31} kg)(6.61*10^{5} \frac{m}{s})^{2}= 1.99*10^{-19} J b) work energy is the energy required to remove one electron, however, this is given in moles and we want it for one sodium atom, so we divide by Avogadro's number to energy get ...
by Silvia Huang 3D
Sat Oct 03, 2015 5:14 pm
Forum: DeBroglie Equation
Topic: Given the energy, calculate the wavelength of y-rays
Replies: 11
Views: 1369

Re: Given the energy, calculate the wavelength of y-rays

Thank you very much!! I forgot that keV can be converted to joules... >_<
by Silvia Huang 3D
Fri Oct 02, 2015 6:49 pm
Forum: DeBroglie Equation
Topic: Given the energy, calculate the wavelength of y-rays
Replies: 11
Views: 1369

Given the energy, calculate the wavelength of y-rays

Hw questions 1.23 The y-ray photons emitted by the nuclear decay of a technetium-99 atom used in radiopharmaceuticals have an energy of 140.511 keV. Calculate the wavelength of these y-rays. I have no idea how to start this question... help please !! :)

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