Search found 34 matches

by Jenna_Hakel_2A
Tue Mar 14, 2017 8:04 pm
Forum: *Alkenes
Topic: Naming every alkene as cis or trans
Replies: 1
Views: 525

Re: Naming every alkene as cis or trans

If one of the carbons has 2 of the same atom on one side, for instance if a carbon was connected to 2 H molecules, then it doesn't matter which one is on the top or bottom because both will produce the same molecule. In this case, it is not possible to say whether it is cis (Z) or trans (E). However...
by Jenna_Hakel_2A
Mon Mar 06, 2017 7:39 pm
Forum: *Organic Reaction Mechanisms in General
Topic: Standard Gibbs Free Energy of Activation
Replies: 4
Views: 721

Standard Gibbs Free Energy of Activation

In the textbook, it says that the standard gibbs free energy of activation for a second transition state is often drawn from the reactants until the second transition state rather than from the intermediates to the second transition state because it is more convenient to measure everything in terms ...
by Jenna_Hakel_2A
Sun Mar 05, 2017 9:38 pm
Forum: *Alkynes
Topic: 1.5 (c)
Replies: 3
Views: 644

Re: 1.5 (c)

Any of the organic molecules that have a carbon-carbon triple bond are alkynes (just as how all single bonds is an alkane, and a double bond makes it an alkene). In all of the line diagrams, none of the carbons or hydrogens are drawn, just the bonds between carbons. Therefore, we know that the point...
by Jenna_Hakel_2A
Mon Feb 27, 2017 5:57 pm
Forum: *Free Energy of Activation vs Activation Energy
Topic: 4.40
Replies: 1
Views: 219

Re: 4.40

You can determine if something is thermodynamically or kinetically stable based on the sign and magnitude of the free energy of the reaction and of formation. A reaction is thermodynamically stable if delta G of the reaction is negative, and thermodynamically unstable if delta G of the reaction is p...
by Jenna_Hakel_2A
Wed Feb 22, 2017 11:58 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 15.65
Replies: 1
Views: 267

Re: 15.65

You can tell that the reaction is endothermic because the activation energy for the reverse reaction is lower than that of the forward reaction. Because of this, it requires more energy for the forward reaction to progress than the reverse reaction, so the reverse reaction occurs more readily. There...
by Jenna_Hakel_2A
Wed Feb 15, 2017 1:22 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Midterm 2014 Question 8
Replies: 4
Views: 423

Re: Midterm 2014 Question 8

I'm still confused on why Ka=(K)^(1/2). I understand that when we solve for the balanced equation to solve for E, it ends up as 2HF-->2H+ + 2F- with a standard cell potential of -0.16V. However, if we were to divide this equation by 2 to get HF-->H+ + F-, wouldn't we then have the correct equation a...
by Jenna_Hakel_2A
Mon Feb 13, 2017 12:04 pm
Forum: Balancing Redox Reactions
Topic: 2016 midterm #6a
Replies: 1
Views: 276

Re: 2016 midterm #6a

To determine the oxidation number of an atom within a molecule, you can add up the oxidation numbers of the elements also in that molecule that generally have a constant oxidation number, and the sum of all of the oxidation numbers of the atoms within a molecule should add up to the total charge wit...
by Jenna_Hakel_2A
Thu Feb 09, 2017 10:39 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagrams
Replies: 3
Views: 328

Re: Cell Diagrams

To write a cell diagram, the anode of the reaction actually goes on the left and the cathode half on the right! And then the order of the molecules does not particularly matter, but they are split up by vertical lines by into groups of the same phase. i.e. The solids together, liquids together, gase...
by Jenna_Hakel_2A
Mon Feb 06, 2017 3:20 pm
Forum: Student Social/Study Group
Topic: Quiz 1 Review
Replies: 4
Views: 524

Re: Quiz 1 Review

I am very interested in studying together an forming a study group! :) my email is jenna.hakel@gmail.com
by Jenna_Hakel_2A
Tue Jan 31, 2017 10:45 pm
Forum: Calculating Work of Expansion
Topic: When to Use Different Formulas for Work
Replies: 2
Views: 356

Re: When to Use Different Formulas for Work

We use w=-PdeltaV when the pressure against which the gas is expanding is constant. However, we use the second equation when the pressure is variable, such as when the expansion is reversible.
by Jenna_Hakel_2A
Mon Jan 30, 2017 6:07 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: HW Prob. 11.17
Replies: 1
Views: 278

Re: HW Prob. 11.17

I also got -2.7 kJ! All the numbers I inputted were the same as in the solutions manual also, so it may just be a typo :)
by Jenna_Hakel_2A
Wed Jan 25, 2017 6:37 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Why is the oxygen (1/2)02instead of 02?
Replies: 2
Views: 454

Re: Why is the oxygen (1/2)02instead of 02?

Because the questions ask about the formation of one mole of the product, if you had O2 instead of 1/2 O2, there would be too many molecules of O2. If you think of it more as just molar ratios, for every one mole of product formed you need half a mole of O2. Just try to balance the equations and mak...
by Jenna_Hakel_2A
Tue Jan 24, 2017 5:24 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Chapter 8 problem 21 [ENDORSED]
Replies: 3
Views: 496

Re: Chapter 8 problem 21 [ENDORSED]

Because the heat lost by the system is all gained by the surroundings, the numerical value on each side will be the same, they will just have opposite signs because one is losing energy and the other is gaining it. Because of this, it does not matter which side we place the extra negative sign on, i...
by Jenna_Hakel_2A
Tue Jan 24, 2017 1:05 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Ch 8 Exercise 77
Replies: 3
Views: 433

Re: Ch 8 Exercise 77

So, following up on that, in terms of question 77, when you use the bond enthalpies that show that 3 of the C-C bonds are double bonds and 3 are single bonds, you get a total energy of 2880 kJ; however, when you use the given values for bond energies given that all 6 of the bonds share the delocaliz...
by Jenna_Hakel_2A
Mon Jan 23, 2017 12:25 pm
Forum: Phase Changes & Related Calculations
Topic: 8.41
Replies: 1
Views: 280

Re: 8.41

The way I solved this problem was by still using the concept that all the heat lost by the water is gained by the ice cube. So qH2O=-qICE. However, the ice requires energy to both change phase to water and then to also change temperature. Therefore, the heat gained by ice (qICE) is q=(moles ice*enth...
by Jenna_Hakel_2A
Mon Jan 23, 2017 12:18 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy equation used in solutions manual
Replies: 2
Views: 315

Re: Enthalpy equation used in solutions manual

For the enthalpies associated with changes in phase, they are all just given in terms of kJ/mole, so in 8.37, they are simply dividing the number of kJ required to vaporize the .579 moles of CH4 to achieve this value. The equation q=moles x molar heat capacity x change in temperature wouldn't apply ...
by Jenna_Hakel_2A
Mon Jan 23, 2017 12:11 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond Enthalpy and Energy of Formation
Replies: 1
Views: 221

Re: Bond Enthalpy and Energy of Formation

I think it all depends on what information is given to you. In the course reader, for example, it begins each new section by saying something along the lines of "When bond enthalpies are not available, use the standard enthalpies of formation." So although all three methods may produce the...
by Jenna_Hakel_2A
Mon Jan 23, 2017 12:05 pm
Forum: Student Social/Study Group
Topic: Quiz 1 Prep
Replies: 8
Views: 804

Re: Quiz 1 Prep

I'm also interested in comparing answers! :)
by Jenna_Hakel_2A
Thu Jan 19, 2017 6:30 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Chapter 8 problem 21 [ENDORSED]
Replies: 3
Views: 496

Re: Chapter 8 problem 21 [ENDORSED]

So we know that the water and the copper will both have the same final temperature, because heat will continue to be exchanged between the two until the temperatures are equal. We also know that, during this process, all of the heat that is lost by the copper will go to the water, because we assume ...
by Jenna_Hakel_2A
Thu Jan 19, 2017 6:22 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Heat capacity [ENDORSED]
Replies: 5
Views: 731

Re: Heat capacity [ENDORSED]

Yes, because at constant pressure it also requires the heat to do work on the surroundings.
by Jenna_Hakel_2A
Wed Jan 18, 2017 10:37 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Heat capacity [ENDORSED]
Replies: 5
Views: 731

Re: Heat capacity [ENDORSED]

The way Dr. Lavelle described in class was to imagine a piston. To maintain constant pressure (based on PV=nRT), the volume must be able to adjust. For instance, when the gas is heated at a constant pressure, it expands, pushing the piston upward. However, for the piston to move upward, the air mole...
by Jenna_Hakel_2A
Fri Jan 13, 2017 11:16 am
Forum: Phase Changes & Related Calculations
Topic: Phase change
Replies: 3
Views: 385

Re: Phase change

I would think that there would be certain vocabulary used to indicate if the problem were a phase change problem, such as vaporization, fusion, or sublimation. In the case of water, we also know the temperatures at which the phase changes occur (0C/32F, 100C/212F), so if the temperature were to pass...
by Jenna_Hakel_2A
Fri Dec 02, 2016 3:34 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Names of Acids and Bases on the Final Exam
Replies: 1
Views: 289

Names of Acids and Bases on the Final Exam

To what extent do we have to know the names of the acids and bases on the final? For example, when we are given an acid/base problem, will we be given its formula or will it say "sulfuric acid" and we must know the formula and the difference between sulfuric and hydrosulfuric acid? I know ...
by Jenna_Hakel_2A
Tue Nov 29, 2016 6:19 pm
Forum: Calculating the pH of Salt Solutions
Topic: Ch 13 Q 21 a
Replies: 2
Views: 376

Re: Ch 13 Q 21 a

In the equation pH=pKa+log([CO3(2-)/HCO3-]), the value of the logarithm is positive. So to find the value of the ratio of the concentrations, you wouldn't do 10^-.75, you would just do 10^.75, with a positive value for .75 because both sides of the equation are positive. When you do this, you find t...
by Jenna_Hakel_2A
Tue Nov 22, 2016 4:23 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Course Reader pg. 156-157
Replies: 1
Views: 230

Re: Course Reader pg. 156-157

If there is a weak acid in which equilibrium strongly favors the reactants, not a lot of H+ will be produced in the reaction. Because of this, the concentration of H+ in the solution may be very, very low, such as 1.0x10^-10. According to the method to calculate pH, the pH should then be equal to -l...
by Jenna_Hakel_2A
Mon Nov 14, 2016 11:51 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Questions about coordination compound (mainly quiz 3 preparation)
Replies: 2
Views: 378

Re: Questions about coordination compound (mainly quiz 3 preparation)

1. In class, he said that square planar is the more common structure for a coordination complex with 4 ligands. He said that to determine if a structure is square planar or tetrahedral requires information that is not covered in class (such as the ligand field theory), but usually structures will be...
by Jenna_Hakel_2A
Mon Nov 07, 2016 11:15 am
Forum: Administrative Questions and Class Announcements
Topic: Chem 14B and 14BL [ENDORSED]
Replies: 11
Views: 3069

Re: Chem 14B and 14BL [ENDORSED]

I was thinking of taking 14B winter quarter, but does that mean I should take 14BL and 14C winter quarter or just 14BL? I had the same question. If anyone knows, if we put off taking 14BL (which I have also been advised to do) until after we take 14B, the following quarter should we take 14BL and 1...
by Jenna_Hakel_2A
Mon Oct 31, 2016 6:51 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: H2CBr2 Polarity
Replies: 2
Views: 282

Re: H2CBr2 Polarity

Following on the above comment, if you look at the shape of a tetrahedral molecule, none of the atoms connected to the central atom are completely opposite each other. The bond angle is 109.5 for every bond, never 180. Because of this, even if the atoms appear to be directly across from each other i...
by Jenna_Hakel_2A
Mon Oct 24, 2016 6:26 pm
Forum: Bond Lengths & Energies
Topic: Bond Order
Replies: 2
Views: 388

Re: Bond Order

Oh wait sorry I missed this! It also discusses it on page 77 of the textbook in the second to last paragraph, which then would be in Chapter 3, Section 6: Lewis Structures of Polyatomic Species.
by Jenna_Hakel_2A
Mon Oct 24, 2016 4:51 pm
Forum: Bond Lengths & Energies
Topic: Bond Order
Replies: 2
Views: 388

Re: Bond Order

The explanation of bond orders in the book is in Chapter 4, Section 10 (Electron Configurations of Diatomic Molecules). So we haven't reached this point in the textbook in class yet! But if you're looking for it, it's on page 134 and 135 in the textbook :)
by Jenna_Hakel_2A
Tue Oct 18, 2016 4:39 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Textbook Question #2.47 [ENDORSED]
Replies: 1
Views: 491

Re: Textbook Question #2.47 [ENDORSED]

Pretty much yes! To make an ion with a charge of +1, you only have to remove one electron. So once you know the configuration of the electrons of an atom, this question is basically just asking where the last electron (the one that will need to be removed) is located. For example, if the configurati...
by Jenna_Hakel_2A
Tue Oct 11, 2016 7:30 pm
Forum: Empirical & Molecular Formulas
Topic: Fall 2015 Quiz Prep question #5 [ENDORSED]
Replies: 3
Views: 532

Re: Fall 2015 Quiz Prep question #5 [ENDORSED]

So to find the empirical formula, you first find the number of moles of Carbon and Hydrogen given the masses produced of carbon dioxide and water. The tricky part in this question is that it is burned in air, so O2 can also contribute to the oxygen in the products; it is not only from the reactant t...
by Jenna_Hakel_2A
Wed Oct 05, 2016 10:39 am
Forum: Properties of Light
Topic: Balmer and Lyman Series [ENDORSED]
Replies: 4
Views: 717

Re: Balmer and Lyman Series [ENDORSED]

We talked about this in my discussion yesterday and my TA told us that for each series grouped together, the energy levels where the electrons start is always the same. For example, for the Lyman series, the electrons always either start at or return to (depending on if the light is absorbed or emit...
by Jenna_Hakel_2A
Thu Sep 29, 2016 5:25 pm
Forum: Photoelectric Effect
Topic: Photoelectric Effect Post-Assessment #22 & 23
Replies: 1
Views: 259

Re: Photoelectric Effect Post-Assessment #22 & 23

For 23, I used the equation E=(hc)/wavelength to find the energy of the light with the wavelength of 194 nm. I then subtracted the number that I calculated in #22 (since that is where we calculated the threshold energy for the metal) according to the equation E(light)=threshold energy + KE(electron)...

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