Search found 59 matches
- Fri Mar 16, 2018 11:02 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: 14.97
- Replies: 1
- Views: 319
14.97
What does it mean when it asks to calculate Ka? As well, why does the solutions manual choose the half reaction with the largest potential to be the anode? I thought the half reaction with the largest potential was the cathode, seeing as it has the most oxidizing power and is thus most likely to be ...
- Tue Mar 13, 2018 8:12 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: HW#15.87
- Replies: 2
- Views: 432
Re: HW#15.87
15.87 asks what conditions can be used to distinguish the two mechanisms-essentially, what mechanisms can be used to distinguish the two slow steps. If the reaction is carried out in a highly concentrated solution of sucrose, mechanism ii will behave as a pseudo-first order reaction, due to its depe...
- Tue Mar 13, 2018 8:07 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Minimum for a B-?
- Replies: 3
- Views: 576
Re: Minimum for a B-?
Considering a B- is 80-83%, 500*.8 is 400 points, so 400/500 points is what would be needed to get an 80% in the class, assuming there is no curve.
- Tue Mar 13, 2018 8:05 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: 15.85
- Replies: 2
- Views: 378
Re: 15.85
This was covered in class on March 9th at the end of lecture. You graph the change in standard Gibbs free energy for the reaction, making sure to detail the changes in standard Gibbs free energy of activation.
- Fri Mar 09, 2018 11:18 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: 15.85
- Replies: 1
- Views: 281
15.85
How is the proposed structure for the activated complex determined?
- Fri Mar 09, 2018 10:47 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: 15.47
- Replies: 3
- Views: 520
15.47
Does anyone have any good tips on how to approach this problem and the diagram? I understand that you have to isolate the reactants and the products, and, by doing so, find the intermediates, but I'm not sure on the quickest way to do so.
- Tue Mar 06, 2018 12:01 am
- Forum: General Rate Laws
- Topic: 15.17
- Replies: 3
- Views: 485
Re: 15.17
Most likely, because zero order reactions don't contribute to reaction rate.
- Mon Mar 05, 2018 11:59 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Test 2 Question 6 Part D
- Replies: 2
- Views: 363
Re: Test 2 Question 6 Part D
Yes, that is the formula that you use.
I would have to know the values for E cathode and E anode in order to tell you if your E cell is correct.
I would have to know the values for E cathode and E anode in order to tell you if your E cell is correct.
- Mon Mar 05, 2018 11:57 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Test 2 Question 2
- Replies: 4
- Views: 623
Re: Test 2 Question 2
First, calculate E standard by E standard=E cathode-E anode
Then, use the equation E standard=(0.05916/n)*log(K) to solve for K.
Then, use the equation E standard=(0.05916/n)*log(K) to solve for K.
- Mon Mar 05, 2018 11:52 pm
- Forum: Experimental Details
- Topic: 15.17a
- Replies: 1
- Views: 701
Re: 15.17a
Yes, that is correct. Even though C changes in concentration, the initial rate remains constant while A and B remain constant.
- Sat Mar 03, 2018 4:09 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Kinetics Test/Final
- Replies: 2
- Views: 417
Kinetics Test/Final
Will we be expected to derive by hand the integrated rate laws from the instantaneous rate laws on the Kinetics Test or Final Exam? Or will just knowing the instantaneous and integrated rate laws be sufficient?
- Fri Mar 02, 2018 12:17 am
- Forum: First Order Reactions
- Topic: problem 15.23B
- Replies: 3
- Views: 557
Re: problem 15.23B
ln(At)/(Ainitial)=-kt
When you do ln(A initial)/(At), the swap of the numerator and denominator makes ln(A initial)/(At)=kt
When you do ln(A initial)/(At), the swap of the numerator and denominator makes ln(A initial)/(At)=kt
- Tue Feb 27, 2018 11:50 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3874701
Re: Post All Chemistry Jokes Here
What do you call a tooth in a glass of water?
A one molar solution.
A one molar solution.
- Tue Feb 27, 2018 11:44 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Homework for Test 3
- Replies: 2
- Views: 471
Re: Homework for Test 3
Considering 15.6 covers through Second-Order Integrated Rate Laws and 15.7 begins Reaction Mechanisms, I would assume the assigned problems between 15.1 and 15.44 would be good practice for test 3, considering the problem set for Reaction Mechanisms begins with problem 15.45.
- Tue Feb 27, 2018 11:41 pm
- Forum: General Rate Laws
- Topic: 15. 17 [ENDORSED]
- Replies: 2
- Views: 432
Re: 15. 17 [ENDORSED]
In experiments 1 and 4, the initial rate stays the same while the concentrations of A and B stay the same between the two experiments-yet, C changes between the two experiments. Thus, C does not contribute to the initial rate, because a change in the initial rate does not result from a change in C.
- Mon Feb 19, 2018 3:38 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Galvanic Cell
- Replies: 3
- Views: 456
Re: Galvanic Cell
Will we have to draw a physical diagram of the galvanic cell for the exam? Or just write out the galvanic cell diagram with the lines representing the phase changes and the salt bridge?
- Mon Feb 19, 2018 3:35 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Galvanic Cell Diagram
- Replies: 1
- Views: 284
Galvanic Cell Diagram
From examples Dr. Lavelle has done in class and from the textbook, I was under the assumption that, in a galvanic cell diagram, you wrote the reactants and the products for the anode and the cathode, with the anode and cathode separated by the double line representing the salt bridge. The reactants ...
- Mon Feb 19, 2018 3:29 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Question 14.25
- Replies: 3
- Views: 465
Re: Question 14.25
As well, a more positive Ecell makes G more negative, and thus the reaction more spontaneous (from G=-nFE).
- Mon Feb 19, 2018 3:28 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Question 14.25
- Replies: 3
- Views: 465
Re: Question 14.25
Metals that are reducing agents are in the anode, as they themselves are becoming oxidized, which occurs in the anode. Thus, you want these metals to have a more negative standard reducing potential, as this will make the Ecell more positive, from the relationship: Ecell=Ecathode-Eanode (you want to...
- Mon Feb 19, 2018 3:25 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Inert Electrode
- Replies: 2
- Views: 458
Inert Electrode
From what I've seen in the solutions, an inert electrode such as platinum is needed in the galvanic cell when the oxidized and reduced molecules are in the same solution (they are both aqueous, or both gas). Is an inert electrode needed when oxidized and reduced molecules are both solids? As well, I...
- Wed Feb 14, 2018 3:30 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Choosing Cp or Cv [ENDORSED]
- Replies: 3
- Views: 554
Re: Choosing Cp or Cv [ENDORSED]
Also-in problems that have both volume and temperature changing, for example-use Cv in your delta S=nCln(T2/T1) temperature change calculation, as volume is constant while temperature is changing (even though volume changes in another part of the reaction). Conversely, in problems that have both del...
- Wed Feb 14, 2018 3:20 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: 11.99
- Replies: 1
- Views: 285
Re: 11.99
The first trend noticed is that the higher the bond dislocation energy, the higher the free energy of formation. This makes sense, as it should take more energy to form a molecule that requires more energy for separation. The second trend is that, as atomic number increases, the free energy of disso...
- Wed Feb 14, 2018 3:17 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Variables in reversible isothermal vs isolated system [ENDORSED]
- Replies: 2
- Views: 724
Re: Variables in reversible isothermal vs isolated system [ENDORSED]
q reversible=-w
And delta S should equal zero for reversible.
And delta S should equal zero for reversible.
- Tue Feb 06, 2018 12:28 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: salt bridge
- Replies: 3
- Views: 376
Re: salt bridge
A salt bridge facilitates counter ion transfer so the solutions stay neutral.
- Tue Feb 06, 2018 12:23 am
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Differing Equations Used For delta S with Change in Temperature
- Replies: 3
- Views: 634
Differing Equations Used For delta S with Change in Temperature
I'm noticing that the solutions manual uses different equations when solving for delta S when there is a temperature change. For example, for 9.13, the manual uses delta S=nRln(T2/T1). For 9.19, the manual uses delta S=Cp,mln(T2/T1). And then, for 9.43, the manual uses delta S=nCp,mln(T2/T1). How do...
- Tue Feb 06, 2018 12:18 am
- Forum: Phase Changes & Related Calculations
- Topic: Differential Thermal Analysis
- Replies: 2
- Views: 352
Re: Differential Thermal Analysis
Considering the readings posted on the syllabus do not include Box 8.1, and since Dr. Lavelle hasn't lectured on it, I assume we would not need to know the information.
- Tue Jan 30, 2018 11:10 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Question 9.89
- Replies: 1
- Views: 214
Question 9.89
What does Sm represent, as in question 9.89?
- Mon Jan 29, 2018 2:54 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: 9.1 Homework
- Replies: 4
- Views: 483
Re: 9.1 Homework
And then for b, just do a simple conversion of units.
For c, use delta S=-deltaH/T in order to make the comparison.
For c, use delta S=-deltaH/T in order to make the comparison.
- Mon Jan 29, 2018 2:53 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: 9.1 Homework
- Replies: 4
- Views: 483
Re: 9.1 Homework
You use change in entropy/time = -qrev/time*T
- Mon Jan 22, 2018 3:36 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Heat Capacity at Constant Volume and Constant Pressure
- Replies: 1
- Views: 255
Re: Heat Capacity at Constant Volume and Constant Pressure
When volume is constant, delta U = q. This is from the internal energy equation delta U = q -P*delta V (with -P*delta V substituted for work). When there is constant volume, delta V thus equals zero, resulting in delta U = q. You just substitute delta U in for q in the heat capacity equation. When p...
- Mon Jan 22, 2018 12:09 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Determining Enthalpy of Vaporization
- Replies: 4
- Views: 638
Re: Determining Enthalpy of Vaporization
How are you able to determine the intermolecular forces for these molecules? Does it have to do with covalent/ionic bonding or hydrogen bonding?
As well, do liquids tend to have higher intermolecular forces?
As well, do liquids tend to have higher intermolecular forces?
- Mon Jan 22, 2018 10:11 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Determining Enthalpy of Vaporization
- Replies: 4
- Views: 638
Determining Enthalpy of Vaporization
If you were to have a question that asked you to determine which compound had a higher enthalpy of vaporization, how would you do so?
If, for example, a question asked you to rank H2O, NaCl, and N2 in order of increasing enthalpy of vaporization, how would you determine this?
If, for example, a question asked you to rank H2O, NaCl, and N2 in order of increasing enthalpy of vaporization, how would you determine this?
- Tue Jan 16, 2018 12:37 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Q 8.67
- Replies: 2
- Views: 315
Re: Q 8.67
After you do the above calculations with the bond enthalpies, you should have delta H = -242 kJ/mol. You then need to take into account that water is in it's gaseous phase here, and the question asks for you to find the enthalpy of formation at a liquid state. With this in mind, subtract the enthalp...
- Tue Jan 16, 2018 12:32 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Bond Enthalpies
- Replies: 2
- Views: 395
Re: Bond Enthalpies
Keep in mind, as in question 8.73 c), the compounds may rearrange into different compounds, but the bonds between the elements remain the same. The reaction enthalpy is zero in situations such as this.
- Tue Jan 16, 2018 12:28 pm
- Forum: Phase Changes & Related Calculations
- Topic: Types of Systems
- Replies: 10
- Views: 1484
Re: Types of Systems
Question 8.1 offers good examples of open, closed, and isolated systems.
- Tue Jan 09, 2018 11:18 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Extra Chapter Covered in Dr. Lavelle's Class
- Replies: 4
- Views: 549
Re: Extra Chapter Covered in Dr. Lavelle's Class
If you want to catch up on that, read only 17.5 and 17.6 and do problems 29, 31, 33, 35, and 37, which has you practice naming coordination compounds.
- Tue Jan 09, 2018 11:06 pm
- Forum: Administrative Questions and Class Announcements
- Topic: reading textbook
- Replies: 5
- Views: 681
Re: reading textbook
As well, what problems in the Chapter 8 problem set should we begin with?
- Tue Jan 09, 2018 11:04 pm
- Forum: Administrative Questions and Class Announcements
- Topic: reading textbook
- Replies: 5
- Views: 681
Re: reading textbook
Yes, I was also wondering which sections of the textbook would be advisable to read in order to follow along with Dr. Lavelle's lecture schedule.
- Tue Dec 05, 2017 12:53 am
- Forum: Conjugate Acids & Bases
- Topic: Acids and Bases [ENDORSED]
- Replies: 8
- Views: 2641
Re: Acids and Bases [ENDORSED]
Will we receive a list similar to this on the final? (I am assuming not).
- Tue Dec 05, 2017 12:48 am
- Forum: Conjugate Acids & Bases
- Topic: Acids and Bases [ENDORSED]
- Replies: 8
- Views: 2641
Re: Acids and Bases [ENDORSED]
A strong acid is an acid in which almost all of the molecules are deprotonated in solution. A weak acid is an acid in which only a small fraction of the molecules become deprotonated in solution.
- Tue Dec 05, 2017 12:45 am
- Forum: Amphoteric Compounds
- Topic: Oxides
- Replies: 2
- Views: 447
Re: Oxides
Metals typically form basic oxides, nonmetals typically form acidic oxides, and substances that react with both acids and bases (see Figure 12.7-these are the elements in and close to the diagonal line of metalloids), are classified as amphoteric.
Reading 12.3 should also help!
Reading 12.3 should also help!
- Wed Nov 29, 2017 10:15 am
- Forum: Hybridization
- Topic: Trick for Hybridization
- Replies: 2
- Views: 277
Re: Trick for Hybridization
Hybridization is linked to regions of electron density and shape. Linear is sp Trigonal planar is sp2 Tetrahedral is sp3 Trigonal bipyramidal is sp3d Octahedral is sp3d2 For compounds with lone pairs about the central atom, consider the electron arrangement. For example, a trigonal pyramidal compoun...
- Wed Nov 29, 2017 10:12 am
- Forum: Hybridization
- Topic: When?
- Replies: 2
- Views: 532
Re: When?
For knowing which hybridized orbital to use, consider the regions of electron density in the compound. Linear: sp Trigonal planar: sp2 Tetrahedral: sp3 Trigonal bipyramidal: sp3d Octahedral: sp3d2 For compounds with lone pairs, consider the electron arrangement about the compound. For example, a com...
- Wed Nov 22, 2017 1:22 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: CO3^2- Tridentate
- Replies: 2
- Views: 491
Re: CO3^2- Tridentate
I was wondering this as well. Is it because the oxygen with two lone pairs and two bonded pairs has a zero formal charge? And that the other two oxygen both have a negative one formal charge?
- Wed Nov 22, 2017 1:21 pm
- Forum: Naming
- Topic: Naming (steps)
- Replies: 6
- Views: 773
Re: Naming (steps)
1) Identify the Greek prefix that corresponds with the coordination number (how many ligands are bonded) 2) When naming, name the ligands in alphabetical order 3) Then after you have named all of the ligands in alphabetical order, then name the Transition Metal Cation and then it's Roman Numeral in ...
- Wed Nov 15, 2017 10:11 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: 4.13c Bond Angle Question [ENDORSED]
- Replies: 3
- Views: 1480
Re: 4.13c Bond Angle Question [ENDORSED]
In question 73, though, how are you able to determine a more exact answer for the bond angle in a shape such as triangular pyramidal or bent? Since it asks you to rank the bond angles in increasing size in various molecules, these approximates are difficult to rank.
- Wed Nov 15, 2017 10:05 am
- Forum: Hybridization
- Topic: Coefficient of Hybridization? [ENDORSED]
- Replies: 2
- Views: 627
Re: Coefficient of Hybridization? [ENDORSED]
This is well illustrated in a couple of homework questions: 4.33, for example, asks you to just name the hybridization orbital. For 4.33 a, the answer is simply sp. On the other hand, 4.95 asks you to name the bonds between the atoms in the CH2=CHCHO molecule. Then, you use the coefficients in namin...
- Mon Nov 06, 2017 1:50 pm
- Forum: Photoelectric Effect
- Topic: Rydberg
- Replies: 11
- Views: 1662
Re: Rydberg
You can also use the equation given by Dr. Lavelle for hydrogen (En = -hR/n^2), as we seem to do examples generally with just hydrogen atoms. This rids of the issue of a negative answer with initial-nfinal
- Mon Nov 06, 2017 1:44 pm
- Forum: *Particle in a Box
- Topic: Homework Problem 1.48
- Replies: 2
- Views: 729
Re: Homework Problem 1.48
I also wouldn't be too worried about solving particle in a box problems, especially because that wasn't on our Chapter 2 test, so I doubt it would be on the midterm.
- Tue Oct 31, 2017 5:28 pm
- Forum: Lewis Structures
- Topic: 3.33 Part C
- Replies: 3
- Views: 447
Re: 3.33 Part C
The double bond is between oxygen and nitrogen.
- Tue Oct 31, 2017 5:27 pm
- Forum: Ionic & Covalent Bonds
- Topic: determining bonds
- Replies: 4
- Views: 568
Re: determining bonds
You can also look at how electrons are apportioned. If elements share electrons in the bond, it is a covalent bond. If electrons are completely "gained" and "lost" by elements bonded together, then the bond is ionic.
- Wed Oct 25, 2017 10:26 am
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: P_xyz axis
- Replies: 3
- Views: 288
Re: P_xyz axis
From the looks of this attached photo, the p orbitals seem to be straddling the axis. The p orbitals on each axis are the direct opposite of the other. Hope this helps
http://www.chem.ucla.edu/~harding/IGOC/P/p_orbital.html
http://www.chem.ucla.edu/~harding/IGOC/P/p_orbital.html
- Wed Oct 25, 2017 10:15 am
- Forum: *Shrodinger Equation
- Topic: Applying the Shrodinger Equation
- Replies: 3
- Views: 506
Re: Applying the Shrodinger Equation
Are we supposed to be able to perform calculations with the Schrodinger Equation?
- Wed Oct 18, 2017 10:31 am
- Forum: DeBroglie Equation
- Topic: De Broglie Wavelength
- Replies: 23
- Views: 3460
Re: De Broglie Wavelength
In 1.35, assuming the velocities of the two people are similar, I think the problem is just trying to show the relationship between the de Broglie wavelengths of two objects of the same speed but different masses, that being that the object with the smaller mass will have the larger de Broglie wavel...
- Wed Oct 18, 2017 10:25 am
- Forum: DeBroglie Equation
- Topic: De Broglie Wavelength
- Replies: 23
- Views: 3460
Re: De Broglie Wavelength
Calculating the de Broglie wavelength will not tell you if it is constructive or destructive. It just simply tells you how long the wavelength is.
- Wed Oct 11, 2017 10:45 am
- Forum: General Science Questions
- Topic: Rusty on High School Chem [ENDORSED]
- Replies: 347
- Views: 460539
Re: Rusty on High School Chem [ENDORSED]
I didn't take AP Chem in high school and took general chemistry my sophomore year. I've noticed people on this feed saying there are night study sessions at Hedrick-when and where are those at? Thank you.
- Wed Oct 11, 2017 10:39 am
- Forum: Properties of Light
- Topic: New User, Homework Question
- Replies: 2
- Views: 231
Re: New User, Homework Question
I, like you, am uncertain as to whether it is okay to do the fundamental problems instead of the ones for Chapter 1. However, based on the syllabus and the material covered in class, I think your best bet would be to do four Chapter 1 problems for your homework. I was able to do four for my discussi...
- Wed Oct 04, 2017 5:14 pm
- Forum: Balancing Chemical Reactions
- Topic: Balancing Chemical equations too slow... any advice? [ENDORSED]
- Replies: 18
- Views: 4075
Re: Balancing Chemical equations too slow... any advice? [ENDORSED]
I also keep track of the number of elements on each side of the equation. Also, I tend to balance the elements that are present in an even number on one side of the equation and an odd number on the opposite side of the equation first. It often makes subsequent calculations easier.
- Wed Oct 04, 2017 5:06 pm
- Forum: Empirical & Molecular Formulas
- Topic: L.39
- Replies: 5
- Views: 774
Re: L.39
I first subtracted 26.45g (mass of crucible) from 28.35(the mass of the crucible and product), to get 1.9 g, which is the mass of the tin oxide. I then subtracted 1.5g (mass of the metallic tin) from 1.9g (the mass of the tin oxide) to get .4g, which is the mass of the oxygen in the air that the tin...