Search found 25 matches

by Yiling Liu 1N
Sat Mar 18, 2017 2:54 pm
Forum: *Constitutional and Geometric Isomers (cis, Z and trans, E)
Topic: Final 2016 Question 7
Replies: 2
Views: 750

Final 2016 Question 7

For Part B, I don't get how to determine if the structure given for 1,2-dipropylcyclohexane is cis or trans.

In general, how does one determine cis/trans for cyclohexanes?

Thanks.
by Yiling Liu 1N
Tue Feb 28, 2017 3:01 pm
Forum: *Alkanes
Topic: 4-ethyl-2,2-dimethylhexane vs 2,2-dimethyl-4-ethylhexane
Replies: 2
Views: 666

4-ethyl-2,2-dimethylhexane vs 2,2-dimethyl-4-ethylhexane

in the "Introduction to Organic Chemistry" workbook on page 8, the book names the alkane 4-ethyl-2,2-dimethylhexane. it says "the substituents are placed alphabetically (ethyl then dimethyl)" but doesn't the letter "d" come before the letter "e"? Is 2,2-dimeth...
by Yiling Liu 1N
Sat Feb 18, 2017 2:54 am
Forum: General Rate Laws
Topic: verifying reaction mechanism of ozone decomposition using pre-equilibrium method [ENDORSED]
Replies: 2
Views: 490

Re: verifying reaction mechanism of ozone decomposition using pre-equilibrium method [ENDORSED]

Actually never mind! There is a pretty good online explanation for how to express [O] in terms of the things actually present in the overall reaction equation. https://chem.libretexts.org/Core/Physical_and_Theoretical_Chemistry/Kinetics/Rate_Laws/Reaction_Mechanisms/Reaction_Mechanisms/Reaction_Mech...
by Yiling Liu 1N
Sat Feb 18, 2017 2:47 am
Forum: General Rate Laws
Topic: verifying reaction mechanism of ozone decomposition using pre-equilibrium method [ENDORSED]
Replies: 2
Views: 490

verifying reaction mechanism of ozone decomposition using pre-equilibrium method [ENDORSED]

example 15.7 The textbook uses the steady-state method to verify the proposed mechanism with the experimental rate law for the decomposition of ozone. 2 O3 (g) --> 3 O2 (g) experimentally determined rate of decomposition of O3 = k[O3]^2/[O2] mechanism proposed: step 1 (fast) O3 <--> O2 + O step 2 (s...
by Yiling Liu 1N
Mon Feb 13, 2017 5:45 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: delta U=0
Replies: 1
Views: 300

Re: delta U=0

Internal energy is dependent on temperature. In isothermal processes, temperature change is 0, thus internal energy change is also 0 for an ideal gas.
by Yiling Liu 1N
Mon Feb 13, 2017 5:42 pm
Forum: Balancing Redox Reactions
Topic: Oxidation Number of Diatomic Oxygen
Replies: 2
Views: 619

Re: Oxidation Number of Diatomic Oxygen

Diatomic molecules have oxidation number of 0
by Yiling Liu 1N
Sat Feb 11, 2017 2:32 pm
Forum: Balancing Redox Reactions
Topic: purpose of C(gr) at anode? [ENDORSED]
Replies: 2
Views: 330

purpose of C(gr) at anode? [ENDORSED]

In question 14.11, the cell diagram is C(gr) | H2(g) | H+ (aq) || Cl-(aq) | Cl2(g) | Pt(s)

I was just curious what the purpose of having Carbon in graphite form at the anode? How do we know when to have Pt or C at an electrode?

Thanks
by Yiling Liu 1N
Mon Feb 06, 2017 9:29 pm
Forum: Balancing Redox Reactions
Topic: 14.11 e, calculation of standard cell potential [ENDORSED]
Replies: 1
Views: 343

14.11 e, calculation of standard cell potential [ENDORSED]

Pt(s) | Sn4+(aq), Sn2+(aq) || Cl-(aq) | Hg2Cl2(s) | Hg(l) I looked up the standard potential for the reduction of Sn4+ to Sn2+, which is -0.14V. However, we know that in this problem since Sn4+ and Sn2+ are on the left side of the diagram, they are at the anode and will be oxidized, not reduced. Thu...
by Yiling Liu 1N
Thu Jan 26, 2017 12:21 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 9.75 positional disorder in cis vs trans molecules
Replies: 1
Views: 284

9.75 positional disorder in cis vs trans molecules

"Considering positional disorder, would you expect a crystal of octahedral cis-MX2Y4 to have the same, higher, or lower residual entropy than the corresponding trans isomer? Explain your conclusion." The answer key says that for the cis compound there will be 12 different orientations. Bes...
by Yiling Liu 1N
Mon Jan 23, 2017 12:15 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Changes in Entropy
Replies: 1
Views: 232

Re: Changes in Entropy

This is how I interpreted it: The textbook mentions work in two primary ways - one is work at a constant pressure, and the other is work when pressure is not constant. Since chapter 9 typically deals with reversible processes, then the work involved is reversible work where external pressure is not ...
by Yiling Liu 1N
Mon Jan 23, 2017 12:07 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: the idea behind finding entropy of vaporization
Replies: 1
Views: 291

the idea behind finding entropy of vaporization

I'm a bit confused by the textbook's explanation on how one finds the entropy of vaporization of water at 25 deg C and 1 bar (on page 328). The textbook divides the process into three steps: 1. heat the liquid to its normal boiling point, 100 deg C 2. allow it to vaporize 3. then cool the vapor back...
by Yiling Liu 1N
Sun Jan 22, 2017 10:54 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7951
Views: 1213957

Re: Post All Chemistry Jokes Here

Can I survive chemistry this quarter?

Yes I chem.
by Yiling Liu 1N
Sun Jan 15, 2017 3:36 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: constant-volume vs. constant-pressure calorimeters
Replies: 1
Views: 262

constant-volume vs. constant-pressure calorimeters

I was reading about constant-volume and constant-pressure calorimeters in the textbook. I was wondering how one knows to distinguish which calorimeter to use in a combustion experiment. For instance, if I wanted to see experimentally find the reaction enthalpy of the combustion of benzene, could I u...
by Yiling Liu 1N
Wed Nov 30, 2016 6:15 pm
Forum: *Titrations & Titration Calculations
Topic: 13.23 How to find final pH?
Replies: 3
Views: 405

Re: 13.23 How to find final pH?

Edit: Thanks for the clarification!
by Yiling Liu 1N
Wed Nov 30, 2016 6:00 pm
Forum: *Titrations & Titration Calculations
Topic: 13.23 How to find final pH?
Replies: 3
Views: 405

13.23 How to find final pH?

5mL 0.010M NaOH (aq) is titrated with 0.005M HCl (aq) What is the pH of the final solution? I don't understand how the answer key got that the final pH is 2.54, when 30.0 mL of HCl was added. Besides for trial-and-error, I don't really see a way to solve for the final pH. I understand that the pH at...
by Yiling Liu 1N
Sun Nov 27, 2016 11:30 am
Forum: Identifying Acidic & Basic Salts
Topic: #12.75
Replies: 3
Views: 872

Re: #12.75

I'm having difficulty solving this problem as well. The fact that there is a sodium salt of an unknown acid with pH 10.35 seems inherently contradictory to me -- wouldn't that mean it is a base, since the pH is >7? I also don't understand how in the answer key Kb was solved with 0.01 in the denomina...
by Yiling Liu 1N
Mon Nov 21, 2016 11:05 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Strong Acids
Replies: 3
Views: 454

Re: Strong Acids

I think by definition acids are proton donors. If an acid more easily donates a proton, then the stronger it is.
by Yiling Liu 1N
Tue Nov 15, 2016 1:19 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Calculating the Equilibrium Composition [ENDORSED]
Replies: 2
Views: 495

Re: Calculating the Equilibrium Composition [ENDORSED]

In the example you are referencing, the equation is PCl5 <--> PCl3 + Cl2 You are told that initially there is some amount of PCl5 in the reaction vessel. There is no other information in the problem that says the initial amount for PCl3 or Cl2. Thus, one assumes that PCl5 will decompose into the pro...
by Yiling Liu 1N
Tue Nov 15, 2016 1:15 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: What does TM stand for? pg 118
Replies: 1
Views: 321

Re: What does TM stand for? pg 118

Yes, you're right - I'm pretty sure TM stands for transition metal.
by Yiling Liu 1N
Tue Nov 15, 2016 12:32 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 11.89 HW
Replies: 2
Views: 373

11.89 HW

The problem is: "The following plot shows how the partial pressures of reactant and products vary with time for the decomposition of compound A into compounds B and C. All three compounds are gases. Use this plot to do the following: (a) Write a balanced chemical equation for the reaction. (b) ...
by Yiling Liu 1N
Sat Nov 12, 2016 4:31 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7951
Views: 1213957

Re: Post All Chemistry Jokes Here

A bear said "Help, I'm dissolving!"
The person next to it said "But bears are insoluble"
The bear said "That's easy for you to say, you're not polar!"
by Yiling Liu 1N
Fri Oct 21, 2016 2:04 pm
Forum: Ionic & Covalent Bonds
Topic: Drawing Lewis structures
Replies: 1
Views: 276

Re: Drawing Lewis structures

Hydrogen has 1 valence electron. Oxygen has 6 valence electrons. H3O+ has 1*3+6-1 valence electrons for a total of 8 valence electrons. I subtracted one because the compound has a 1+ charge. I drew the structure somewhat like this: ////// H ////// | ////H-- O -- H ////// .. * you can also add bracke...
by Yiling Liu 1N
Sun Oct 09, 2016 4:43 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Homework Question 1.33 [ENDORSED]
Replies: 2
Views: 473

Re: Homework Question 1.33 [ENDORSED]

For your second question, regarding how much energy is required to remove the electron from the metal surface:

We recall the equation E = hv.

v is given in the problem as 2.50*10^16 Hz, and h is Plank's constant, or 6.626*10^(-34) J.s

plugging in the values, E = 1.66*10^(-17) J
by Yiling Liu 1N
Sun Oct 09, 2016 4:29 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Homework Question 1.33 [ENDORSED]
Replies: 2
Views: 473

Re: Homework Question 1.33 [ENDORSED]

For your first question, regarding the wavelength of the ejected electron: We can utilize the equation λ = h / p, where h is Plank's constant and p is momentum, or the mass of electron x velocity of electron. λ = (6.626 * 10^(-34)) ------------------------- (9.11 * 10^(-31)) (3.6*10^6)) In the numer...
by Yiling Liu 1N
Sat Oct 01, 2016 1:30 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Building-Up Principle [ENDORSED]
Replies: 3
Views: 3306

Re: Building-Up Principle [ENDORSED]

Hi, I actually had a similar question but here is a helpful video https://www.youtube.com/watch?v=wS5u2jk6W8Y . By looking at the electron configuration of an atom, you can tell if it is in an excited state if it "jumps" orbitals or begins filling in the next orbital before completely occu...

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