Search found 27 matches

by Katelyn Li 2J
Thu Mar 16, 2017 3:10 pm
Forum: *Alkanes and Substituted Alkanes (Staggered, Eclipsed, Gauche, Anti, Newman Projections)
Topic: Winter 2014 Q6E/F
Replies: 1
Views: 600

Winter 2014 Q6E/F

This question asks to draw the lowest and second lowest energy conformation Newman diagrams for 3-chloro-4,4,4-trihydroxy-3-methylbutanenitrile looking down the C2-C3 bond axis. Can someone please explain the arrangements? I understand why it's staggered, but not where to put everything.
by Katelyn Li 2J
Mon Mar 13, 2017 9:28 pm
Forum: *Constitutional and Geometric Isomers (cis, Z and trans, E)
Topic: Example on Page 17 (Organic Textbook)
Replies: 1
Views: 256

Example on Page 17 (Organic Textbook)

Could someone please explain how the last two examples (E-3,7-dimethylocta-1,3,7-triene and Z-3,7-dimethylocta-1,3,7-friend) are E and Z? I understand the concept of E (opposite sides) and Z (same side) but I'm not sure how this is applied in this case.
by Katelyn Li 2J
Mon Mar 06, 2017 3:20 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Fast/Slow Steps in Reaction Mechanisms
Replies: 1
Views: 294

Fast/Slow Steps in Reaction Mechanisms

I understand that if the first step in a proposed reaction mechanism is fast and the second is slow, we use the pre-equilibrium approach. But if the first step is slow and the second is fast, is the rate law of the first step also that of the overall reaction? As in, no further work is needed?
by Katelyn Li 2J
Sat Mar 04, 2017 11:06 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Quiz 3 [ENDORSED]
Replies: 14
Views: 989

Re: Quiz 3 [ENDORSED]

In addition to the pages in the course reader that Dr. Lavelle (and an earlier comment) specified, he also said that the concepts that will be quizzed are kinetics (Reaction profiles, Arrhenius equation and calculating activation energies), thermodynamics and kinetics of organic reactions, and hydro...
by Katelyn Li 2J
Thu Feb 23, 2017 2:15 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Effects of Temperature on Rate Constant
Replies: 1
Views: 277

Effects of Temperature on Rate Constant

Could someone please explain why raising the temperature increases the rate constant of reactions with higher activation barriers more than it does the rate constant of reactions with lower activation barriers?
by Katelyn Li 2J
Sat Feb 18, 2017 3:53 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7606
Views: 1017833

Re: Post All Chemistry Jokes Here

Did you hear oxygen went on a date with potassium? It went OK.
by Katelyn Li 2J
Sun Feb 12, 2017 11:07 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Midterm 2013 Question 3A
Replies: 4
Views: 490

Midterm 2013 Question 3A

A blacksmith tempers a 1.45kg katana made of carbon steel to 314.0 C and dunks it into a large vat of room temperature water (25.0 C). Assuming all the heat is transferred to the water such that the sword ends up at 25.0 C, and the steam does not eat past its measured boiling temperature (100.0 C), ...
by Katelyn Li 2J
Sun Feb 12, 2017 2:53 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Question on 14.37
Replies: 1
Views: 244

Question on 14.37

The question asks to determine the potential of the cells. I'm confused on part c, where the cell diagram is Pt (s) | Cl2 (g, 250 Torr) | HCl (aq, 1.0M) || HCl (aq, 0.85M) | H2 (g, 125 Torr) | Pt (s) In the solutions manual, the pressures are in the numerator and the concentrations are in the denomi...
by Katelyn Li 2J
Thu Feb 09, 2017 1:06 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14.23
Replies: 3
Views: 347

14.23

The questions asks: For each reaction that is spontaneous under standard conditions, write a cell diagram, determine the standard cell potential, and calculate G for the reaction. I'm confused about part c, which is the reaction (c) Cr2O72 (aq) + 14 H (aq) + 6 Pu3 (aq) ---> 6 Pu4 (aq) + 2 Cr3 (aq) +...
by Katelyn Li 2J
Thu Feb 02, 2017 2:31 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Salt Bridge?
Replies: 3
Views: 291

Re: Salt Bridge?

To expand upon the previous reply, think of the diagram of the cell we've been looking at in class. On the anode side, Zn2+ ions are produced and on the cathode side, Cu2+ ions are used up. Without a salt bridge, the transfer of electrons from one reaction beaker to another would cause the charge to...
by Katelyn Li 2J
Sun Jan 29, 2017 11:45 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Methods of Calculating Gibbs Free Energy
Replies: 2
Views: 377

Methods of Calculating Gibbs Free Energy

How come for example 9.14 in the reading (not the actual question at the end of the chapter), subtracting the standard Gibbs free energy of the reactants from the products does not give the correct answer? The example asks to "Calculate the standard Gibbs free energy of formation of HI(g) at 25...
by Katelyn Li 2J
Sat Jan 28, 2017 8:10 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Importance of Sig Figs
Replies: 2
Views: 346

Re: Importance of Sig Figs

I had Dr. Lavelle last quarter as well and I remember the scoring for questions usually had 1 point specifically for correct sig figs.
by Katelyn Li 2J
Fri Jan 20, 2017 5:52 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: HW 8.67 b) [ENDORSED]
Replies: 1
Views: 225

Re: HW 8.67 b) [ENDORSED]

When doing problems regarding the standard enthalpy of a substance, the reactants are in their pure elemental forms. So although the reaction you used may be a possibility, given the context of the question, you would not want to use CO because it is a compound.
by Katelyn Li 2J
Sat Jan 14, 2017 10:19 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hess's Law
Replies: 1
Views: 203

Re: Hess's Law

The law utilizes the fact that enthalpy is a state function, meaning that it is pathway-independent. Taking this into account, it allows us to bypass irrelevant values to only find the sum of all changes.
by Katelyn Li 2J
Sat Dec 03, 2016 4:42 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Question on 11.89
Replies: 1
Views: 318

Question on 11.89

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) Calculate the equilibr...
by Katelyn Li 2J
Sat Nov 26, 2016 5:13 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7606
Views: 1017833

Re: Post All Chemistry Jokes Here

With all the stress about finals coming up, I think it's important that we all think like a proton and stay positive! :)
by Katelyn Li 2J
Wed Nov 16, 2016 7:04 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Question on 17.31
Replies: 1
Views: 278

Question on 17.31

For part (d), it asks to write the formula for sodium bisoxalato(diaqua)ferrate(III). I wrote it in the order it was written in the name, that is, Na[Fe(C204)2(OH2)2], but in the solutions manual, it puts (OH2)2 before the (C2O4)2. Is there a reason for this or does it not matter too much?
by Katelyn Li 2J
Fri Nov 11, 2016 5:23 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7606
Views: 1017833

Re: Post All Chemistry Jokes Here

I hate when people reply to my texts with "K." Who wants to talk about potassium?
by Katelyn Li 2J
Tue Nov 01, 2016 10:53 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Fall 2015 Midterm Question 4
Replies: 1
Views: 353

Fall 2015 Midterm Question 4

For part 4Aii, it asks to draw and name the shape of XeF2 and give a bond angle. I drew the correct Lewis structure, but I'm confused as to why the shape is linear. I thought the side of Xe with two pairs of electrons would create more repulsive forces than the side with just one pair and result in ...
by Katelyn Li 2J
Tue Nov 01, 2016 6:27 pm
Forum: General Science Questions
Topic: Fall 2013 Midterm Q4
Replies: 1
Views: 590

Re: Fall 2013 Midterm Q4

The prefix Mega- for SI units indicates that it is 10^6, so 1 MeV = 10^6 eV. The mass of the neutron is given as 1.00866 g/mol, so you can first convert it to SI units, which would be 0.00100866 kg/mol. Then, divide by Avogadro's number to find the mass of a single neutron rather than an entire mole...
by Katelyn Li 2J
Mon Oct 24, 2016 5:20 pm
Forum: Lewis Structures
Topic: Question on 3.41
Replies: 1
Views: 282

Question on 3.41

For the last part of this question, it asks to draw the Lewis structure for H2C(NH2)COOH. How do you know what order to draw the structure in? I thought that for compounds like this, it was usually drawn in the same order it was written in, but the solutions manual puts NH2 on the far left. Also, ho...
by Katelyn Li 2J
Thu Oct 20, 2016 11:52 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Question about 2.39
Replies: 1
Views: 232

Question about 2.39

For question 2.39, it asks to determine whether the given electron configuration denotes an atom in its ground state or an excited state. I am fairly confident in determining the answers, but I am curious as to whether those configurations are actually possible, particularly in part (b). How can an ...
by Katelyn Li 2J
Tue Oct 11, 2016 4:54 pm
Forum: Balancing Chemical Reactions
Topic: Determining States of Matter in Reactions
Replies: 7
Views: 771

Determining States of Matter in Reactions

When asked to write a balanced equation, are we required to specify the states of matter? For example, question 7 of the Fall 2015 quiz prep says to write a balanced equation for the combustion of CH3OH. I understand how to do the actual problem, but how can you tell what state of matter CH3OH is? I...
by Katelyn Li 2J
Tue Oct 11, 2016 10:44 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Quiz 1 Fall 2015 #3 [ENDORSED]
Replies: 3
Views: 473

Re: Quiz 1 Fall 2015 #3 [ENDORSED]

I think in this case it should be 1.10 because that's the whole range of the potential speed.

For example, some object with a speed of 9 m/s and an uncertainty of plus or minus 1 m/s means it could be 8 m/s or 10 m/s. Therefore, the uncertainty would be 2 m/s.
by Katelyn Li 2J
Thu Oct 06, 2016 9:28 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Heisenberg Uncertainty Problem in A-V Module
Replies: 2
Views: 791

Re: Heisenberg Uncertainty Problem in A-V Module

Just a clarifying question: Normally, if given the radius of an atom, we'd double it to find the diameter, which would then be used as the uncertainty of the position. In this case, because the question specifies that the uncertainty is 1% of the radius, it doesn't require us to double it. Is that c...
by Katelyn Li 2J
Tue Sep 27, 2016 10:45 am
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Fundamentals E.21: Amount in moles vs Number of molecules vs Formula units
Replies: 4
Views: 1488

Re: Fundamentals E.21: Amount in moles vs Number of molecules vs Formula units

I have another question about this problem, specifically part b. I worked it through and thought it required 4 sig figs, but when I checked the solutions manual, it was rounded to 3. Can someone explain why the answer is given with 3 sig figs?
by Katelyn Li 2J
Mon Sep 26, 2016 6:38 pm
Forum: Student Social/Study Group
Topic: Chemistry Jokes
Replies: 31
Views: 4378

Re: Chemistry Jokes

A photon walks into a hotel. The man at the front desk asks if he needs help with any luggage. The photon says, "No thanks, I'm traveling light."

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