Search found 116 matches
- Wed Mar 10, 2021 5:20 pm
- Forum: General Rate Laws
- Topic: Rate Equation Order (Exponent)
- Replies: 3
- Views: 283
Re: Rate Equation Order (Exponent)
Hi! We can only use the stoichiometric coefficients for an elementary reaction or an elementary step in proposed reaction mechanism. The slow step will also be the rate determining step. In the end game question, we can treat step 1 like it is at equilibrium and can get a relationship between the tw...
- Tue Mar 09, 2021 7:48 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: strong reducing agent textbook 6.45
- Replies: 2
- Views: 234
Re: strong reducing agent textbook 6.45
Hi Eileen! I'm wondering the same thing. Since Dr. Lavelle should give us the values that we need on the exam, I'm hoping that this won't be something that we need to worry about. However, I haven't known which reactions to use for questions like 6.45, and so I would love to hear any tips that anyon...
- Tue Mar 09, 2021 5:15 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Final Exam Questions
- Replies: 15
- Views: 924
Re: Final Exam Questions
Hi Selena! In 14A, I don't think Dr. Lavelle ever took questions directly from the midterms and put them on the final.
There may be similar question on the 14B final to the ones we saw on the midterms, but they probably won't be exactly the same.
There may be similar question on the 14B final to the ones we saw on the midterms, but they probably won't be exactly the same.
- Tue Mar 09, 2021 5:12 pm
- Forum: Student Social/Study Group
- Topic: Favorite Chemistry YouTube Channels
- Replies: 39
- Views: 3466
Re: Favorite Chemistry YouTube Channels
Hi Jessie, thank you for making this! Organic Chemistry Tutor and Khan Academy have some helpful videos!
- Tue Mar 09, 2021 5:09 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Order of Ions in a Cell Diagram
- Replies: 2
- Views: 244
Re: Order of Ions in a Cell Diagram
Hi Sunny! Dr. Lavelle just confirmed in his office hours that the order of aqueous ions does not matter!
- Sun Mar 07, 2021 10:17 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Metals
- Replies: 6
- Views: 360
Re: Metals
Hi Emily! I'm wondering if this just means that if a metal or compound is aqueous, then it should dissolve in solution?
- Sun Mar 07, 2021 10:15 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Appendix 2B
- Replies: 3
- Views: 340
Re: Appendix 2B
Hi Sameer! I have been wondering the same thing this quarter, but Dr. Lavelle said that if we needed values that are found in Appendix 2B, then he should give them to us on the exam.
- Sun Mar 07, 2021 11:04 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Metal/Nonmetal/Metalloid Conductors
- Replies: 1
- Views: 182
Metal/Nonmetal/Metalloid Conductors
Hi! My understanding is that nonmetals are not conductors, but can any nonmetals act as conductors in some cases? And are metalloids conductors or just weak conductors? Are all metals conductors or just specifically d-block metals? And can all S block metals act as conductors? Are Gold, Copper, and ...
- Sun Mar 07, 2021 10:41 am
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Concentration Cells at Equilibrium
- Replies: 7
- Views: 395
Concentration Cells at Equilibrium
Hi! Are concentration cells always at equilibrium? Or only for certain cases?
- Sun Mar 07, 2021 10:25 am
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Textbook Problem 6N.13
- Replies: 6
- Views: 656
Textbook Problem 6N.13
Hi! When I used the Nernst Equation on Textbook Problem 6N.13, I got Q=2.67 x 10^6, but the answer key said the answer was just 10^6, and I'm not sure why the answer should just be 10^6? Thank you in advance! 6N.13 Calculate the reaction quotient, Q, for the following cell reactions, given the measu...
- Sun Feb 28, 2021 5:07 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Metalloids as Conductors
- Replies: 1
- Views: 155
Re: Metalloids as Conductors
Hi Arezo! I'm wondering this same thing! And are all S block metals conductors or only specific ones? Also, are there any nonmetals that could act as a conductor?
- Sun Feb 28, 2021 1:11 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Week 7/8 Sapling #12
- Replies: 9
- Views: 511
Re: Week 7/8 Sapling #12
Hi Samantha! Your work looks correct! I think you just need to convert J to kJ at the end and provide the answer in kJ on Sapling.
- Sun Feb 28, 2021 1:08 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Sapling HW Week 7/8 #18
- Replies: 2
- Views: 224
Re: Sapling HW Week 7/8 #18
Hi Adam! I started by writing the unbalanced equation with the reactants on the left side and products on the right. The question states that "rust is caused by iron reacting with oxygen gas in the presence of water to create an oxide layer." So the reactants would be Fe + O2 + H2O. Then i...
- Sun Feb 28, 2021 1:07 pm
- Forum: Balancing Redox Reactions
- Topic: Textbook Problem 6K.5 part d
- Replies: 1
- Views: 139
Textbook Problem 6K.5 part d
Hi! Could someone please walk me through how to solve the textbook problem 6K.5 for part d? It is in basic solution, and I couldn't figure out how to balance the oxygens and hydrogens. Thank you in advance! The question is: Balance each of the following skeletal equations by using oxidation and redu...
- Sun Feb 28, 2021 1:00 pm
- Forum: Balancing Redox Reactions
- Topic: Sapling Week 7/8 #18
- Replies: 3
- Views: 248
Re: Sapling Week 7/8 #18
Hi Scot! I started by writing the unbalanced equation with the reactants on the left side and products on the right. The question states that "rust is caused by iron reacting with oxygen gas in the presence of water to create an oxide layer." So the reactants would be Fe + O2 + H2O. Then i...
- Sun Feb 28, 2021 12:51 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Eo of Concentration Cell
- Replies: 3
- Views: 211
Re: Eo of Concentration Cell
Hi Sasha! My understanding is that cell potential E is is sensitive to the concentrations of reactants and products. A galvanic cell typically has different species on both sides, which would have different concentrations. A concentration cell typically has the same species on both sides. If both sp...
- Sun Feb 21, 2021 11:19 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Classes for Biochem Majors
- Replies: 6
- Views: 485
Re: Classes for Biochem Majors
Hi Ethan! I am not a Biochem major, but I know that Wesley Wu, one of the UAs, is also a Biochem major, and he took the 30 series. You could send him or a counselor an email or other students may have an answer for you. Good luck!
- Sun Feb 21, 2021 11:15 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: fun way to remember anode and cathode
- Replies: 16
- Views: 2664
Re: fun way to remember anode and cathode
Hi Eric! Thank you for sharing this! I've heard of RED CAT before but haven't heard of AN OX, and so I'll definitely use this to help me to remember that anodes participate in oxidation.
- Sun Feb 21, 2021 11:01 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Salt Bridge
- Replies: 30
- Views: 1416
Re: Salt Bridge
Hi! A salt bridge helps to maintain electrical neutrality and charge balance with the positive and negatives in the Galvanic cell. It allows ions to pass through to help keep the cell running and neutral and keep the charges flowing within the cell so that they don't build up.
- Thu Feb 18, 2021 12:31 am
- Forum: General Science Questions
- Topic: No Lavelle Chem 14C?
- Replies: 68
- Views: 4890
Re: No Lavelle Chem 14C?
Aw I'm gonna miss not having Lavelle and Chem Community and the UAs for 14 C : (
- Wed Feb 17, 2021 10:15 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Textbook 4.43
- Replies: 1
- Views: 116
Textbook 4.43
Hi! Problem 4.43 in the textbook says if 120 mL of H2 gas at SATP combines with.... Since it says SATP, I thought that meant that it would be at 25 degrees Celsius, but the solutions manual says STP and used 0 degrees Celsius. I'm wondering what the temperature should be?
- Sun Feb 14, 2021 11:14 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: isochoric / isometric
- Replies: 9
- Views: 613
Re: isochoric / isometric
Hi! Isochoric means that delta V = 0 and that volume is constant. Isobaric means that delta P = 0 and that pressure is constant. Isothermal means that delta T= 0 and that temperature is constant. I think that isometric is when you have 2 or more compounds that are composed of the same number and spe...
- Sun Feb 14, 2021 11:04 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Cv vs Cp
- Replies: 5
- Views: 367
Re: Cv vs Cp
Hi! I'm wondering the same thing and think that this is a great question.
- Sun Feb 14, 2021 11:03 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: 4H.1 part d
- Replies: 4
- Views: 292
4H.1 part d
Hi! In the textbook question 4H.1 part d, it asks about which substance has the higher molar entropy at 298 K: 1.0 mol of Ar (g) at 1.00 atm or 1.0 mol Ar (g) at 2.00 atm? I had originally thought that 1.0 mol Ar (g) at 2.00 atm would have a higher molar entropy since the pressure is greater because...
- Sun Feb 14, 2021 10:55 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: 4F.1 part a
- Replies: 2
- Views: 194
4F.1 part a
Hi! On question 4F.1 part a in the textbook, the answer key shows that delta S = - q / T because heat is leaving the body and releasing energy, but then it showed that the answer was positive. I thought that the answer was supposed to be - 0.341 J/(K * s), but I'm wondering if I'm missing something?
- Sat Feb 13, 2021 10:31 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: 4D.9
- Replies: 1
- Views: 210
4D.9
Hi! In the textbook question 4D.9, it asks us about finding the enthalpy density, and I thought it was just a matter of dimensional analysis and converting units, but the answer key used the enthalpies of formation to find the overall enthalpy of the reaction. Were we supposed to get those values in...
- Sun Feb 07, 2021 10:31 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3603462
Re: Post All Chemistry Jokes Here
Did you hear that oxygen and potassium went on a date?
Yeah it went OK!
Yeah it went OK!
- Sun Feb 07, 2021 10:25 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Which q equation to use
- Replies: 3
- Views: 177
Re: Which q equation to use
Hi! I think the first equation you listed may be for a calorimeter and not a molecule, and the mass of the calorimeter is not taken into consideration.
- Sun Feb 07, 2021 10:22 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Atoms, Linear, Non- Linear Molecules?
- Replies: 9
- Views: 1033
Re: Atoms, Linear, Non- Linear Molecules?
Hi! I think CO2 would be a linear molecule based on the Lewis structure and that Carbon, the central atom, has no lone pairs, which is a factor of its linear shape.
For my Sapling homework, I was given Ar (g) and just assumed that it was an atom.
For my Sapling homework, I was given Ar (g) and just assumed that it was an atom.
- Sun Feb 07, 2021 10:19 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: work and heat (positive or negative?)
- Replies: 3
- Views: 149
Re: work and heat (positive or negative?)
Hi! What has helped me is thinking about what happens when we work out and how we expend energy when we exercise and do work, thus releasing energy. If you think about the example from lecture with pumping bike tires, it takes a lot of energy to pump them up, and so we release that energy into the s...
- Sun Feb 07, 2021 12:46 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Positive vs Negative Heat Capacities
- Replies: 3
- Views: 139
Positive vs Negative Heat Capacities
Hi! Is it possible to have a negative heat capacity? Or does it always have to be a positive value?
- Sun Jan 31, 2021 11:44 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3603462
Re: Post All Chemistry Jokes Here
What's a kidney's favorite instrument?
The organ!
The organ!
- Sun Jan 31, 2021 11:43 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3603462
Re: Post All Chemistry Jokes Here
Why are skeletons good at chopping trees?
Because they're lumbar-jacks!
Because they're lumbar-jacks!
- Sun Jan 31, 2021 11:42 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3603462
Re: Post All Chemistry Jokes Here
Never trust an atom...
They make up everything
They make up everything
- Sun Jan 31, 2021 11:42 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3603462
Re: Post All Chemistry Jokes Here
What do you call an acid with an attitude?
A mean-oh acid!
A mean-oh acid!
- Thu Jan 28, 2021 2:41 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Combustion of nitrogen for enthalpy of combustion reactions
- Replies: 2
- Views: 2439
Combustion of nitrogen for enthalpy of combustion reactions
Hi! I was looking at enthalpy of combustion problems and am wondering if the equation for the combustion of Nitrogen is just N2 + 2 O2 --> 2 NO2 ? or would it be N2 + O2 --> 2 NO ?
Also for a reaction like CxHxOxNx + O2 → CO2 + H20 + N2
would it yield N2 or NO2?
Also for a reaction like CxHxOxNx + O2 → CO2 + H20 + N2
would it yield N2 or NO2?
- Sat Jan 23, 2021 11:37 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Table 5G2 - K vs Kc
- Replies: 4
- Views: 142
Table 5G2 - K vs Kc
Hi! For table 5G2 in the textbook, I'm wondering if the K without a subscript is supposed to be Kp? It is clear that the other K value that is listed is Kc.
- Sat Jan 23, 2021 11:34 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: standard states
- Replies: 6
- Views: 350
standard states
Hi! Are we supposed to know the standard states of molecules? Or just some of the most common ones? Or will they be given to us?
- Sat Jan 23, 2021 11:33 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Kp and aqueous solutions
- Replies: 1
- Views: 367
Kp and aqueous solutions
Hi! I know that for Kc equilibrium expressions we leave out solids and liquids, and we keep aqueous states and gases in the expression. I also know that when determining which direction a reaction will shift due to a change in pressure, we look at the amount of moles of gas on both sides and do not ...
- Fri Jan 22, 2021 5:33 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Method 2 and Resonance Structures
- Replies: 2
- Views: 86
Method 2 and Resonance Structures
Hi! When we're using method 2 or the bond enthalpies to find the overall enthalpy for the reaction, and we're looking at which bonds are breaking and forming, what should we do if we have resonance structures?
- Fri Jan 22, 2021 5:30 pm
- Forum: Phase Changes & Related Calculations
- Topic: Carbon (graphite form)
- Replies: 6
- Views: 306
Carbon (graphite form)
Hi! What should we know about Carbon in the graphite form?
- Sun Jan 17, 2021 10:00 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: 6E.1 Textbook problem
- Replies: 1
- Views: 98
Re: 6E.1 Textbook problem
Hi Jazlyn! I solved this problem the same way that you did. Since H2SO4 is a strong acid, I assumed that it would fully dissociate, and the concentration of [H30+] would be 0.15 M. The you should be able to do pH=-log(H3O+), which would be = -log(0.15)= 0.82. Dr. Lavelle also mentioned this in his l...
- Sun Jan 17, 2021 9:52 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: pH of Salts
- Replies: 1
- Views: 75
Re: pH of Salts
Hi! This is a great question! I'm wondering if neutralization would occur?
- Sun Jan 17, 2021 9:48 pm
- Forum: Calculating Work of Expansion
- Topic: Sapling Week 3/4 no. 14
- Replies: 4
- Views: 282
Re: Sapling Week 3/4 no. 14
Hi Shana! I am not sure how to do this problem either, but Dr. Lavelle has not lectured on this topic yet, so I'm hoping that our lectures this week will help us to be able to solve it. It's not due for a little while, so it's good that we have more time to work on it.
- Sun Jan 17, 2021 9:45 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Sapling Week 2 #5
- Replies: 1
- Views: 101
Re: Sapling Week 2 #5
Hi Jaylin! I started by converting pH to pOH and then found the concentration for [OH-] using 10^(-pOH). I then assumed that the concentration of [OH-] was at equilibrium and used that concentration of [OH-] to fill out my ICE table. In the ice table here, I used [OH-] = 3.673*10-5. We just don't kn...
- Sun Jan 17, 2021 9:40 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Sapling Week 2 #5
- Replies: 2
- Views: 166
Re: Sapling Week 2 #5
Hi Margia! I also started by converting pH to pOH and then got a similar concentration for [OH-]. I just assumed that the concentration of [OH-] was at equilibrium and used that concentration of [OH-] to fill out my ICE table. We just don't know the initial concentration of the amine, so I used the ...
- Sun Jan 10, 2021 1:33 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Textbook problem 5G.3b
- Replies: 1
- Views: 59
Re: Textbook problem 5G.3b
Hi! I think you're right! It seems like it should be 5 N2(g) for the products.
- Sun Jan 10, 2021 1:18 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Chemical Equilibrium Part 4 Post-Module Assessment #15
- Replies: 2
- Views: 151
Chemical Equilibrium Part 4 Post-Module Assessment #15
Hi! How many moles are there of reactants and products in this question? I was thinking that there were 6 moles of reactants and 6 moles of products, not including solids or aqueous. Unless the aqueous should be included for determining the number of moles on each side? 15. The photosynthesis reacti...
- Sun Jan 10, 2021 1:09 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Counting Moles
- Replies: 11
- Views: 545
Counting Moles
Hi! When finding the effect of increasing or decreasing partial pressure by determining how many moles are on each side of the chemical equation or how many moles there are of reactants and products, are aqueous molecules included? or just gases? For example, 2A (aq) + 1B (g) <--> 2C (g), would ther...
- Sat Jan 09, 2021 5:54 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Chemical Equilibrium Part 3 Post-Module Assessment #20
- Replies: 3
- Views: 118
Re: Chemical Equilibrium Part 3 Post-Module Assessment #20
Okay! I tried doing that, but I still got the incorrect concentration for SO3.
- Sat Jan 09, 2021 5:53 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Changing K
- Replies: 4
- Views: 163
Changing K
Hi! So Dr. Lavelle has been talking about how temperature is the only thing that changes k but doubling the stoichiometric coefficients for a reaction will square the k value, so technically changing the temperature isn't the only way to change the k value?
- Fri Jan 08, 2021 10:03 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Chemical Equilibrium Part 3 Post-Module Assessment #20
- Replies: 3
- Views: 118
Chemical Equilibrium Part 3 Post-Module Assessment #20
Hi! On the Chemical Equilibrium Part 3 Post-Module Assessment, this is problem #20: A vial of SO2 (0.522 mol.L-1) and O2 (0.633 mol.L-1) react and reach equilibrium. Calculate the equilibrium concentrations of the products and reactants given that KC = 5.66 x 10-10 for this reaction: 2 SO2 (g) + O2 ...
- Wed Jan 06, 2021 5:21 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Question about sapling homework
- Replies: 5
- Views: 325
Re: Question about sapling homework
Hi! No, we don't lose points, and there is no penalty for using hints! If you give up on the question, it will mark the question wrong though and deduct points.
- Wed Dec 16, 2020 9:06 pm
- Forum: Naming
- Topic: Resources for Help With Naming
- Replies: 2
- Views: 206
Re: Resources for Help With Naming
Hi Amanda! I hope that you're doing well! I found this website to be helpful for me! I can look and see if I can find others. Naming can definitely be a challenge.
http://www.chemistry.wustl.edu/~edudev/ ... _comp.html
http://www.chemistry.wustl.edu/~edudev/ ... _comp.html
- Wed Dec 16, 2020 9:02 pm
- Forum: Lewis Structures
- Topic: Maximum electrons in expanded octet
- Replies: 3
- Views: 389
Maximum electrons in expanded octet
Hi! I'm just wondering what the maximum number of electrons would be in an expanded octet for an element like Iodine?
- Wed Dec 16, 2020 9:00 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Brooke's Week 10 Workshop KEY
- Replies: 1
- Views: 208
Re: Brooke's Week 10 Workshop KEY
Thank you so much Brooke for positing this and for all of your time and help this quarter! I appreciate you so much and am looking forward to your sessions in 14B! Happy Holidays!
- Wed Dec 16, 2020 8:58 pm
- Forum: Student Social/Study Group
- Topic: HUGE THANK YOU to Dr. Lavelle, the UAs, TAs!
- Replies: 14
- Views: 896
Re: HUGE THANK YOU to Dr. Lavelle, the UAs, TAs!
Thank you so much Dr. Lavelle and to all of the TAs and UAs! I am so grateful for all of the time, help, dedication, and commitment! I appreciate you all so much and am looking forward to seeing you all in 14B! Happy Holidays! : )
- Wed Dec 16, 2020 8:55 pm
- Forum: Administrative Questions and Class Announcements
- Topic: TA Review: Acids and Bases - Kat [ENDORSED]
- Replies: 1
- Views: 216
Re: TA Review: Acids and Bases - Kat [ENDORSED]
Thank you so much for posting your slides! They are so helpful!
- Wed Dec 16, 2020 8:54 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Chemistry Community posts after this quarter [ENDORSED]
- Replies: 7
- Views: 1020
Re: Chemistry Community posts after this quarter [ENDORSED]
Hi! I think we can still see our posts after this quarter ends because Chemistry Community has posts from 2011 and possibly earlier until now!
- Sat Dec 12, 2020 10:50 pm
- Forum: Hybridization
- Topic: Pi Bonds and Hybrid Orbitals
- Replies: 1
- Views: 167
Re: Pi Bonds and Hybrid Orbitals
This is a great question! I have been wondering the same thing.
- Mon Dec 07, 2020 12:03 am
- Forum: Biological Examples
- Topic: Oxidation States
- Replies: 6
- Views: 8913
Re: Oxidation States
For example, if you had [Fe(CN)6]^4-, you know that the overall charge is -4. CN has an oxidation state of -1 and -1x6=-6. Using algebra, x+(-6)=-4, x=2. So Fe would have to have an oxidation state of +2.
- Sun Dec 06, 2020 11:59 pm
- Forum: Biological Examples
- Topic: Oxidation States
- Replies: 6
- Views: 8913
Re: Oxidation States
For finding oxidation states, I would look at the charges that you know and use algebra to find the oxidation state of the metal.
- Sun Dec 06, 2020 11:58 pm
- Forum: Student Social/Study Group
- Topic: 14BL
- Replies: 2
- Views: 87
Re: 14BL
I also enrolled in Chem 14BL and Chem 14B for next quarter and am wondering the same thing!
- Sun Dec 06, 2020 11:57 pm
- Forum: Administrative Questions and Class Announcements
- Topic: TA review sessions [ENDORSED]
- Replies: 4
- Views: 280
TA review sessions [ENDORSED]
I saw that each TA has 2 review sessions where they will be discussing the same topic in each. Will both sessions be the same? Will the material they discuss in each session be the same? Or will each of their 2 sessions be different?
- Sun Dec 06, 2020 11:55 pm
- Forum: Hybridization
- Topic: un-hybridized orbitals / orthogonal
- Replies: 1
- Views: 347
un-hybridized orbitals / orthogonal
Are un-hybridized orbitals considered orthogonal? And why or why not?
- Sun Dec 06, 2020 11:52 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: flat plane vs 3D
- Replies: 2
- Views: 201
flat plane vs 3D
Would a tetrahedral be considered the first 3D shape? Would molecules with 2 and 3 regions of electron density be considered flat?
- Sun Nov 29, 2020 11:45 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Easiest Way to Memorize Shape Names
- Replies: 9
- Views: 656
Re: Easiest Way to Memorize Shape Names
I think just doing a lot of practice problems is beneficial in memorizing the shapes and bond angles and becoming more familiar with the molecules. I also think that being able to visualize the 3D shape of the molecule is helpful. One of the UA's shared this website with us: http://intro.chem.okstat...
- Sun Nov 29, 2020 11:43 pm
- Forum: Resonance Structures
- Topic: Resonance Structure Confusion
- Replies: 5
- Views: 508
Re: Resonance Structure Confusion
An example of a resonance structure would be O3 because there is one single bond between an O and another O and one double bond between an O and another O. The electrons are delocalized and are shared in the molecule, and the single and double bonds could rotate between atoms and keep the same struc...
- Sun Nov 29, 2020 11:40 pm
- Forum: Resonance Structures
- Topic: Resonance Structure Confusion
- Replies: 5
- Views: 508
Re: Resonance Structure Confusion
They are not considered resonance structures because the structures and number of single, double, and triple bonds were changing for each one, and the electrons were not delocalized between the atoms.
- Sun Nov 29, 2020 11:35 pm
- Forum: Hybridization
- Topic: Determining the number of sigma and pi bonds
- Replies: 8
- Views: 938
Re: Determining the number of sigma and pi bonds
Yes, I counted all of the sigma bonds first for every bond and then all of the pi bonds after for the molecules.
- Sun Nov 29, 2020 11:33 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Tetrahedral molecular shape
- Replies: 10
- Views: 1833
Re: Tetrahedral molecular shape
I would also add that if each of the bond angles were 90 degrees, then the molecule would be flat and not 3D. Since there are repulsion forces between bonding pairs of electrons and the atoms are maximizing the distance, the structure is 3D, thus making the bond angles 109.5, which is greater than 90.
- Sun Nov 29, 2020 11:25 pm
- Forum: Sigma & Pi Bonds
- Topic: Textbook Problem 2F.3
- Replies: 1
- Views: 83
Re: Textbook Problem 2F.3
Hi! H2S has 2 single bonds, so it has 2 sigma bonds and 0 pi bonds. SO2 has 2 double bonds, and each double bond has 1 sigma bond and 1 pi bond, so there are 2 sigma bonds and 2 pi bonds in total for SO2.
- Sun Nov 29, 2020 11:22 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Shape Names and Degrees
- Replies: 4
- Views: 339
Re: Shape Names and Degrees
Hi! I think we do need to memorize bond angles and make sure that we know that one of them is 109.5 degrees. I think just doing a lot of practice problems is beneficial in memorizing the shapes and bond angles and becoming more familiar with the molecules. I also think that being able to visualize t...
- Thu Nov 19, 2020 10:33 pm
- Forum: Dipole Moments
- Topic: 3F:5
- Replies: 3
- Views: 210
3F:5
3F.5 Suggest, giving reasons, which substance in each of the following pairs is likely to have the higher normal melting point (Lewis structures may help your arguments): CHI3 or CHF3. I thought that CHF3 would have a higher melting point because F is very electronegative and has a higher ionization...
- Thu Nov 19, 2020 11:43 am
- Forum: Lewis Structures
- Topic: Textbook Q 2.C.5
- Replies: 3
- Views: 152
Re: Textbook Q 2.C.5
I had this same question. I think that O is more electronegative than Cl, and so it has a higher electron pulling power and really wants the full octet. Since O is more electronegative than Cl, it can handle having the negative formal charge.
- Wed Nov 18, 2020 9:59 pm
- Forum: Trends in The Periodic Table
- Topic: Trend for effective nuclear charge
- Replies: 3
- Views: 302
Trend for effective nuclear charge
Is there a trend for effective nuclear charge?
- Tue Nov 17, 2020 11:35 pm
- Forum: Bond Lengths & Energies
- Topic: Energy bullet point on outline
- Replies: 1
- Views: 76
Energy bullet point on outline
What does this bullet mean on the outline about the quantum world? Describe the factors affecting the energy of an electron in a many-electron atom.
- Tue Nov 17, 2020 10:58 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: n=6,l=5
- Replies: 7
- Views: 3118
n=6,l=5
If n=6, would l=5 be a valid answer? I know that l can be 0,...n-1 and that l=0 corresponds to s, l=1 corresponds to p, l=2 corresponds to d, l=3 corresponds to f. Based on this, l=5 would not correspond to s, p, d, or f. So would l=5 be valid because it fits for n=6-1=5?
- Tue Nov 17, 2020 10:38 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Nodes in the d orbital
- Replies: 4
- Views: 427
Nodes in the d orbital
How many nodes does the d orbital have? I think the p orbital just has 1 node and the s orbital has 0 nodes.
- Mon Nov 16, 2020 12:00 am
- Forum: Bond Lengths & Energies
- Topic: Bond energy equation
- Replies: 3
- Views: 137
Bond energy equation
In the bond energy equation, what grows faster? The numerator or radius (denominator)?
- Sun Nov 15, 2020 11:59 pm
- Forum: Dipole Moments
- Topic: London Dispersion Forces
- Replies: 10
- Views: 934
London Dispersion Forces
Why do all molecules experience London Dispersion Forces?
- Sun Nov 15, 2020 11:56 pm
- Forum: Lewis Structures
- Topic: Resonance Structures
- Replies: 2
- Views: 97
Resonance Structures
Some molecules can have a resonance structure with one double bond, two double bonds, or three double bonds, and so do you count all of them as resonance structures even if the molecule with two or three double bonds is not as stable as the molecule with one rotating double bond?
- Sun Nov 15, 2020 9:45 pm
- Forum: Trends in The Periodic Table
- Topic: Ion Trends
- Replies: 28
- Views: 1476
Ion Trends
What are some of the ion trends that we should know? And could someone please explain the ionic radius trend?
- Sun Nov 15, 2020 9:44 pm
- Forum: Bond Lengths & Energies
- Topic: Hydrogen Bond Length
- Replies: 3
- Views: 94
Hydrogen Bond Length
If two molecules have multiple Hydrogen bonds, do they all have to be the same length?
- Tue Nov 10, 2020 6:59 pm
- Forum: Electronegativity
- Topic: Electronegativity Difference for Covalent and Ionic Bonds
- Replies: 6
- Views: 218
Electronegativity Difference for Covalent and Ionic Bonds
So if the electronegativity difference is > 2, then there is an ionic bond like NaCl. If the electronegativity difference is < 1.5, then there would be a covalent bond (C-F). What would happen if the value falls between 1.5 and 2?
- Sun Nov 08, 2020 11:54 pm
- Forum: Lewis Structures
- Topic: Shape
- Replies: 3
- Views: 91
Shape
Does it matter where you put each atom when creating a Lewis structure as long as the formal charges are okay and the correct number of electrons are used?
- Sun Nov 08, 2020 11:52 pm
- Forum: Electronegativity
- Topic: Fluorine and Helium
- Replies: 6
- Views: 224
Fluorine and Helium
Knowing that Fluorine is the most electronegative element and that it's not in the very top right corner of the periodic table, would Helium be considered an exception to the trend since it is in the very top right corner?
- Sun Nov 08, 2020 11:51 pm
- Forum: Electronegativity
- Topic: Fluorine
- Replies: 7
- Views: 386
Re: Fluorine
Knowing that Fluorine is the most electronegative element and that it's not in the very top right corner of the periodic table, would Helium be considered an exception to the trend since it is in the very top right corner?
- Sun Nov 08, 2020 11:46 pm
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: bigger cation and how that affects polarization
- Replies: 2
- Views: 123
bigger cation and how that affects polarization
If you have a bigger cation, then the charge density is lower, and it has a lower pulling ability and lower polarizing power. What does this mean about the polarizing ability? And how is it affected?
- Sun Nov 08, 2020 11:43 pm
- Forum: Lewis Structures
- Topic: expanded/smaller octets
- Replies: 6
- Views: 123
Re: expanded/smaller octets
Yes, I believe that only atoms with a d-orbital can have an expanded octet.
- Sun Nov 08, 2020 7:21 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3603462
Re: Post All Chemistry Jokes Here
Are you a CATion? Because you're always so PAWsitive!
- Sun Nov 01, 2020 11:16 pm
- Forum: SI Units, Unit Conversions
- Topic: Memorizing SI Units
- Replies: 14
- Views: 2666
Re: Memorizing SI Units
Hi Amanda! I am not sure which ones we should have memorized, and I have this same question too. I did find picometers on the formula sheet, which is given as 1 pm = 10^-12 m. I think an acronym could be really helpful if someone has one!
- Sun Nov 01, 2020 8:36 pm
- Forum: Trends in The Periodic Table
- Topic: Radius trends for elements like Carbon
- Replies: 4
- Views: 156
Radius trends for elements like Carbon
Would Carbon and other elements in the same column gain or lose an electron? And how does it affect its radius and the radii trends?
- Sun Nov 01, 2020 7:36 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: S and P orbitals and shielding
- Replies: 2
- Views: 135
S and P orbitals and shielding
Hi! Does the 3s orbital shield the 3p orbital? Or instead of n=3, it could be n=2 or n=1.
- Fri Oct 30, 2020 4:13 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: M(l) Quantum Number
- Replies: 5
- Views: 355
Re: M(l) Quantum Number
Yes, okay thank you!
- Fri Oct 30, 2020 4:09 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: M(l) Quantum Number
- Replies: 5
- Views: 355
M(l) Quantum Number
Hi! If we were looking at the 2p orbital, then n=2 and l=1, then m(l) could equal -1, 0, or 1, thus being 3 possible quantum values. If we made our own arbitrary scale, like p(x)=-1, p(y)=0, and p(z)=1, we could say that m(l) = -1 if we wanted the quantum number for p(x)? Or does that matter? I know...
- Tue Oct 27, 2020 11:45 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: Quantum Numbers
- Replies: 3
- Views: 215
Quantum Numbers
Can the first 3 quantum numbers be the same?
- Sun Oct 25, 2020 10:49 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Rydberg Equation
- Replies: 2
- Views: 146
Re: Rydberg Equation
Hi! I am wondering the same thing, but I think that n1 is n final and n2 is n initial, because it should always be final - initial.
- Sun Oct 25, 2020 10:46 pm
- Forum: Properties of Electrons
- Topic: Work Function
- Replies: 3
- Views: 165
Work Function
Is there a way to find work function? Or does it just need to be given?
- Sun Oct 25, 2020 10:44 pm
- Forum: Properties of Electrons
- Topic: Kinetic energy for electrons
- Replies: 3
- Views: 233
Kinetic energy for electrons
When would the kinetic energy be 0 for an electron when using:
KE(electron)=E(photon)- Work Function
KE(electron)=E(photon)- Work Function