Search found 132 matches
- Fri Mar 13, 2020 5:58 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Irreversible System
- Replies: 2
- Views: 293
Re: Irreversible System
The questions would have to say isothermal irreversible, so you would use the deltaS=nRln(V2/V1) formula. The delta S obtained is the delta S of the system. For a irreversible system, the graph is a sharp vertical dip, which means the surroundings do not have time to react to this change, so the del...
- Fri Mar 13, 2020 5:09 pm
- Forum: Student Social/Study Group
- Topic: Tips for Staying Focused
- Replies: 64
- Views: 4177
Re: Tips for Staying Focused
Yeah same with me. I am usually really focused before finals week but there is a lot going on in terms of panic and new news. I try and get through some work but it seems like there are constant distractions every few minutes.
- Fri Mar 13, 2020 2:25 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Arrhenius equation
- Replies: 2
- Views: 269
Re: Arrhenius equation
You would have to be given the constant A, the rate constant, and the temperature to solve for activation energy.
- Mon Mar 09, 2020 8:27 am
- Forum: Administrative Questions and Class Announcements
- Topic: Review session on Friday
- Replies: 3
- Views: 304
Re: Review session on Friday
I don't think they bruincast the review session. However, they have a worksheet that they usually go through and they post it on chemistry community and then they will post the answers sometime after the review session. So if you absolutely can't make it you can still review the content they covered.
- Mon Mar 09, 2020 8:26 am
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Ways to Approach Reaction Mechanisms
- Replies: 3
- Views: 276
Re: Ways to Approach Reaction Mechanisms
yes, and he said he will teach pre-equilibrium approach to us in todays lecture!
- Mon Mar 09, 2020 8:26 am
- Forum: Administrative Questions and Class Announcements
- Topic: Final
- Replies: 2
- Views: 276
Re: Final
Last quarter the final was around 8 questions which a few parts to each one. It roughly covered each topic we had learned. However, it did not take 3 hours to finish. As Brian said, I had a lot of time to check my work before I turned it in.
- Mon Mar 09, 2020 8:24 am
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Concentration cells
- Replies: 4
- Views: 429
Re: Concentration cells
I don't remember there being a question where you had to utilize solubility rules. I think for concentration cells there was a HW problem that said if you change one of the ions in your salt bridge what would happen, and I think you were chagning NO3- to Cl- and if PbCl2 forms its insoluble so the s...
- Mon Mar 09, 2020 8:23 am
- Forum: First Order Reactions
- Topic: Units for t
- Replies: 30
- Views: 1318
Re: Units for t
You can use whichever units you would like but, as Brian said, make sure the units match up in all of your terms before solving.
- Mon Mar 09, 2020 8:22 am
- Forum: First Order Reactions
- Topic: First Order Equation
- Replies: 3
- Views: 284
Re: First Order Equation
Yes there are multiple ways of expressing the equation. The first one is the linearized form and thats the one that Lavelle put on the Kinetics syllabus. I prefer to use that one since its easy to graph and see the linear line.
- Mon Mar 02, 2020 8:58 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Deciding Where Reactions Occur
- Replies: 2
- Views: 223
Re: Deciding Where Reactions Occur
Reduction occurs at the cathode and oxidation occurs at the anode.
- Mon Mar 02, 2020 8:57 pm
- Forum: Balancing Redox Reactions
- Topic: Balancing redox (from worksheet 6-8 workshop)
- Replies: 2
- Views: 330
Re: Balancing redox (from worksheet 6-8 workshop)
Since we know that this is in acidic solution. We also know that Chromium is being reduced, we can conclude that hydrogen ions will be in our reactants and water will be in our products. Also the electrons will be on the reactants side. After we determine what our products and reactants are, we basi...
- Mon Mar 02, 2020 8:54 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: cell diagrams
- Replies: 2
- Views: 231
Re: cell diagrams
Yes, that is correct. No coefficients in your cell diagram. Use platinum in instances when you have no solids in your redox reactions.
- Mon Mar 02, 2020 8:52 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell Diagrams and Metal Solids
- Replies: 2
- Views: 190
Re: Cell Diagrams and Metal Solids
I'm not sure. I have only seen Carbon(graphite) and Platinum. I would stick with platinum just to be safe.
- Mon Mar 02, 2020 8:51 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: EMF
- Replies: 1
- Views: 177
Re: EMF
It is basically the difference in potentials that gives rise to an electrical current. I'm not sure about the second part of your question though.
- Mon Feb 24, 2020 10:35 am
- Forum: Administrative Questions and Class Announcements
- Topic: Hw 8
- Replies: 10
- Views: 705
Re: Hw 8
Usually you can do the hw on material that he has taught within the past week of your discussion time.
- Mon Feb 24, 2020 10:32 am
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Test 2
- Replies: 6
- Views: 417
Re: Test 2
Second page of the thermodynamics outline(outline 4), and the all of outline 5. We will begin to learn kinetics but it will not be on the test.
- Mon Feb 24, 2020 10:16 am
- Forum: Administrative Questions and Class Announcements
- Topic: Outlines for Thermodynamics and Electrochem
- Replies: 1
- Views: 159
Re: Outlines for Thermodynamics and Electrochem
Hmm. I am not having that problem. Maybe try using a different web browser. I am also not sure how to post images on chemistry community.
- Mon Feb 24, 2020 10:14 am
- Forum: Balancing Redox Reactions
- Topic: OIL RIG
- Replies: 4
- Views: 330
Re: OIL RIG
Yeah thats another good way. I may just end up using it!
- Mon Feb 24, 2020 10:08 am
- Forum: Administrative Questions and Class Announcements
- Topic: Test 2 info
- Replies: 8
- Views: 681
Re: Test 2 info
We will begin learning kinetics on Friday, but it will not be on the test.
- Mon Feb 24, 2020 10:07 am
- Forum: Administrative Questions and Class Announcements
- Topic: Thermo
- Replies: 3
- Views: 291
Re: Thermo
I agree with those above. I also thing its smart to go about and create a little study guide as you move through the text, lecture notes, and homework problems, outlining which situations in which to use certain equations and rules and exceptions. Repetition of the problems is key as the more proble...
- Mon Feb 17, 2020 5:06 pm
- Forum: Balancing Redox Reactions
- Topic: Why do we split equations?
- Replies: 12
- Views: 814
Re: Why do we split equations?
There is no other reason, other than the fact that it helps to visualize and see what is being oxidized and reduced.
- Mon Feb 17, 2020 5:06 pm
- Forum: Balancing Redox Reactions
- Topic: Why do we split equations?
- Replies: 12
- Views: 814
Re: Why do we split equations?
There is no other reason, other than the fact that it helps to visualize and see what is being oxidized and reduced.
- Mon Feb 17, 2020 5:05 pm
- Forum: Administrative Questions and Class Announcements
- Topic: 14BL and 14C
- Replies: 8
- Views: 476
Re: 14BL and 14C
I think it is definitely manageable, however I do know that 14BL is a lot of calculations and it takes time. So if you think that learning OCHEM along with doing chemistry labs is too much then split it up.
- Mon Feb 17, 2020 5:04 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Constant R
- Replies: 15
- Views: 1081
Re: Constant R
The best way to determine when to use which instead of memorizing them is to look at the units to see which units you are working with and what you want to end up with.
- Mon Feb 17, 2020 5:03 pm
- Forum: Ideal Gases
- Topic: pv=nrt
- Replies: 19
- Views: 1211
Re: pv=nrt
Yes, you would just need to plug in 0 degrees celsius and 1 atm.
- Mon Feb 17, 2020 5:02 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Cv vs Cp
- Replies: 17
- Views: 992
Re: Cv vs Cp
Basically, Cv represents the heat capacity at constant volume, so a bomb calorimeter per say. Cp represents heat capacity at constant pressure, so an irreversible expansion. Cv is 3/2R and Cp is 5/2R
- Mon Feb 17, 2020 5:00 pm
- Forum: Van't Hoff Equation
- Topic: K rather than Kc
- Replies: 10
- Views: 766
Re: K rather than Kc
This is a good question. When I was doing my calculations I used the same value for both but my calculations could be wrong. Does anyone know?
- Thu Feb 13, 2020 1:28 am
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: constant pressure and volume
- Replies: 3
- Views: 354
Re: constant pressure and volume
Constant volume means there is no work done. At constant pressures, q is equal to delta H and work is -PdeltaV.
- Thu Feb 13, 2020 1:27 am
- Forum: General Science Questions
- Topic: Tutoring
- Replies: 6
- Views: 409
Re: Tutoring
What does AAP stand for?
- Thu Feb 13, 2020 1:26 am
- Forum: Student Social/Study Group
- Topic: Number of Chemistry Community Posts
- Replies: 45
- Views: 2633
Re: Number of Chemistry Community Posts
Personally, you can go under "your posts" tab and check the date on which you posted. This is the most definite way to check if you have completed the required number of posts in the right time period.
- Thu Feb 13, 2020 1:25 am
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Significance of open, closed, isolated
- Replies: 22
- Views: 1179
Re: Significance of open, closed, isolated
In my opinon. The most applicable scenario in which we would use our knowledge about closed, isolated, and open systems in when assessing whether there are changes in heat and work. For example since a bomb calorimeter is an isolated system there is no work done on the system.
- Thu Feb 13, 2020 1:23 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: deltaU for an ideal gas
- Replies: 2
- Views: 182
Re: deltaU for an ideal gas
Exactly what was said above. Dr. Lavelle just used those in derivations and to explain concepts to us. We don't actually need to solve problems using them.
- Thu Feb 13, 2020 1:21 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Spontaneous
- Replies: 23
- Views: 1249
Re: Spontaneous
A negative delta G value or a positive detla S universe (total) value.
- Thu Feb 13, 2020 1:20 am
- Forum: Student Social/Study Group
- Topic: Notes from 2.10.20
- Replies: 3
- Views: 254
Re: Notes from 2.10.20
Dr. Lavelle didn't lecture on any topics. He rather went over past exam questions in preparation for our midterm.
- Mon Feb 03, 2020 10:43 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: reversing signs
- Replies: 5
- Views: 274
Re: reversing signs
You can reverse the sign of enthalpy change when doing Hess's law and you are trying to determine the overall reaction by manipulating the equations.
- Mon Feb 03, 2020 10:41 pm
- Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
- Topic: Degeneracy
- Replies: 4
- Views: 104
Re: Degeneracy
I think the problem he did in his lecture was a good example. You have to identify the number of orientations the molecule can be in. Lets say its 3. Then you raise this number to the power of how many molecules of it there are. That is your W (degeneracy) in the boltzmann equation.
- Mon Feb 03, 2020 10:39 pm
- Forum: Van't Hoff Equation
- Topic: Van't Hoff
- Replies: 6
- Views: 375
Re: Van't Hoff
Has Dr. Lavelle taught this yet?
- Mon Feb 03, 2020 10:39 pm
- Forum: Phase Changes & Related Calculations
- Topic: -w vs w
- Replies: 15
- Views: 676
Re: -w vs w
Basically work is represented by "w". negative work means that the system has lost energy since it has itself done work. positive work means that the system has gained energy because something else has done work on the system.
- Mon Feb 03, 2020 10:37 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Lyndon Bui Workshops
- Replies: 7
- Views: 490
Re: Lyndon Bui Workshops
I attended lyndon's review session earlier today, and he said he will be posting the worksheet later this week. He usually comes and announces it in lecture. I'm assuming he will do this either on Wednesday or Friday.
- Mon Feb 03, 2020 10:36 pm
- Forum: Phase Changes & Related Calculations
- Topic: Heating Curve
- Replies: 6
- Views: 1052
Re: Heating Curve
The flat lines on a heating curve represent the deltaH(fusion) or the deltaH(vaporization) depending on where the horizontal line is. The increasing diagonal lines are representing the q=mcAT as we are heating the substance with a certain heat capacity.
- Sat Feb 01, 2020 11:32 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Isolated vs Closed [ENDORSED]
- Replies: 34
- Views: 4333
Re: Isolated vs Closed [ENDORSED]
An isolated system is something where matter and energy cannot enter or leave the system. A closed system is where only energy, but not matter, can enter or leave the system. And an open system is where both matter and energy can enter or leave the system. That being said, an insulated water bottle ...
- Tue Jan 28, 2020 12:50 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Thermochemistry Textbook HW
- Replies: 4
- Views: 184
Re: Thermochemistry Textbook HW
Just took a look and that is right. 4D has Hess's law, and 4E is bond enthalpies, all of which we have covered. 4C may have some problems as well.
- Tue Jan 28, 2020 12:48 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: 4A and B
- Replies: 2
- Views: 93
Re: 4A and B
You could read through the 4A and 4B focuses, but I would wait until he covers it in class. It seems as if he is going out of order for this unit.
- Tue Jan 28, 2020 12:48 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: 4E.5
- Replies: 2
- Views: 128
Re: 4E.5
The way you calculate the enthalpy of these reactions is always (Delta H(Bonds Broken) - DeltaH(Bonds Formed)). So if you break a C-H bond lets just say, but then reform it, they will cancel out according to our equation. That is what is happening in this problem because the Bonds Form release energ...
- Tue Jan 28, 2020 12:45 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: ICE BOX
- Replies: 27
- Views: 889
Re: ICE BOX
yes, the cutoff is 10^-3.
However, I would advise only to use the short cut when the value is 10^-5 since you don't want to take a chance and have your answer be off by a few digits. On the test I would always check your answer using the quadratic formula if you used the short cut.
However, I would advise only to use the short cut when the value is 10^-5 since you don't want to take a chance and have your answer be off by a few digits. On the test I would always check your answer using the quadratic formula if you used the short cut.
- Tue Jan 28, 2020 11:02 am
- Forum: Administrative Questions and Class Announcements
- Topic: Thermochemistry Textbook HW
- Replies: 4
- Views: 184
Re: Thermochemistry Textbook HW
Yeah I do know that the Hess's Law HW problems are from 4d. Other than that I am also confused on which hw problems we should be doing.
- Thu Jan 23, 2020 9:07 pm
- Forum: Ideal Gases
- Topic: Partial Pressure
- Replies: 4
- Views: 273
Re: Partial Pressure
A very simple way to convert from concentration to pressure is (Pressure = Concentration * RT)
- Thu Jan 23, 2020 8:52 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Ice Tables
- Replies: 3
- Views: 234
Re: Ice Tables
I do not fully understand the scope of your question but I'll answer to the best of my ability. If they ask for final equilibrium concentrations and you begin with a certain amount of reactant, lets say 0.1, then the E section for that reactant would be 0.1-x, so you would plug x back in to find the...
- Thu Jan 23, 2020 8:50 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: removing H2 from N2 + 3H2 -> 2NH3
- Replies: 7
- Views: 2053
Re: removing H2 from N2 + 3H2 -> 2NH3
If H2 is removed from this chemical reaction. That means that the Q>K and the reaction will shift toward the reactants. Basically the system wants to compensate for the decrease in H2, so it will produce more reactants (H2 and N2) to raise the amount of H2 back so that Q=K
- Thu Jan 23, 2020 8:39 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Chemical equation
- Replies: 5
- Views: 256
Re: Chemical equation
In those instances in which you are not given a chemical equation, you need to use the context clues to generate an equation. Usually you will have to come up with the equations yourself only for Acid-Base equilibrium problems, in which the acid or base and water are almost always the reactants and ...
- Thu Jan 23, 2020 8:36 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Q<K
- Replies: 11
- Views: 298
Re: Q<K
As Kyle said, if Q<K then there is more reactants at that instance, so in order to reach equilibrium (Q=K), the reaction needs to proceed toward the products.
- Mon Jan 13, 2020 11:36 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: volume and K value
- Replies: 3
- Views: 468
Re: volume and K value
Changing the volume changes the pressure. This can cause the reaction to lean toward the reactants or products but it does not change the equilibrium constant value.
- Mon Jan 13, 2020 11:35 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Updating my account
- Replies: 2
- Views: 122
Re: Updating my account
Click on the "Register Alias and Password) link at the top menu bar once you are logged in, and you will be able to change your alias to the new discussion section you are in
- Mon Jan 13, 2020 11:26 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Effect of Inert Gases
- Replies: 9
- Views: 354
Re: Effect of Inert Gases
Increasing pressure by inserting an inert gas will not change the way the reaction leans. Only increasing pressure by reducing volume will affect the reactant quotient which will change the direction that the reaction favors.
- Mon Jan 13, 2020 11:24 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Studying tips
- Replies: 10
- Views: 506
Re: Studying tips
I would recommend you read the textbook, complete all the HW problems, revisit your lecture notes, and browse Chemistry Community. If you do these things well you will be prepared for the test.
- Mon Jan 13, 2020 2:16 pm
- Forum: Ideal Gases
- Topic: When to use this equation
- Replies: 14
- Views: 500
Re: When to use this equation
In the context of equilibrium, you use this equation to convert from pressure to concentration. So if you want to calculated K(p) and you are given concentration values, you can use PV=nRT to convert to partial pressure values for that reactant or product. The same applies for converting from pressu...
- Mon Jan 13, 2020 2:14 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Solid and Liquid
- Replies: 5
- Views: 204
Re: Solid and Liquid
Yes, the concentration change of solids and liquids is insignificant. If you think about it, if they do not affect the concentrations of reactants/products, then they serve no purpose in the equilibrium constant.
- Sun Jan 12, 2020 11:18 pm
- Forum: Ideal Gases
- Topic: Q vs. K
- Replies: 10
- Views: 346
Re: Q vs. K
Q and K are calculated using the same rules and formula. However Q is used when you are given initial concentration/pressure values, and K is used when you are given equilibrium concentration/pressure values. You can compare Q and K to determine in which direction the reaction will proceed.
- Mon Jan 06, 2020 5:17 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Calculating Kc
- Replies: 4
- Views: 157
Re: Calculating Kc
Basically solids and liquids have a constant concentration. There may be very tiny changes in volume of them but its not enough to affect our calculations. The activity of solids and liquids at equilibrium is 1, so therefore it doesn't affect equilibrium concentrations.
- Mon Jan 06, 2020 5:08 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: K threshold
- Replies: 2
- Views: 168
Re: K threshold
Threshold is 10^-4
- Mon Jan 06, 2020 4:59 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Reactant Quotient vs Equilibrium Constant
- Replies: 3
- Views: 140
Reactant Quotient vs Equilibrium Constant
How can you identify when to calculate a reactant quotient vs an equilibrium constant. Also, are the rules for calculating them the same (ex: do you omit solids and liquids for reactant quotient as well?)
- Mon Jan 06, 2020 4:54 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Question 5H.3
- Replies: 3
- Views: 210
Re: Question 5H.3
This equation can be broken down into two smaller equation. By looking at the chart it becomes evident of what those two equations are. Then identify K values at the correct temperature for these reactions and multiply K values together for the overall K for the reaction.
- Mon Jan 06, 2020 4:52 pm
- Forum: Ideal Gases
- Topic: ICE Table Variables
- Replies: 6
- Views: 302
Re: ICE Table Variables
Always use variables in your change row. the coefficient for your change variable corresponds to the coefficient in the chemical equation. Use a negative sign to indicate using up of reactants and a positive sign to indicate production of products.
- Tue Dec 03, 2019 12:53 pm
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: dipole dipole
- Replies: 7
- Views: 422
Re: dipole dipole
Yes. The molecule needs to be polar in order to for it to have dipole dipole interactions since the dipole on one molecule can form an IMF with the dipole on the other molecule.
- Tue Dec 03, 2019 12:52 pm
- Forum: Trends in The Periodic Table
- Topic: Question
- Replies: 17
- Views: 1419
Re: Question
They have the same trend but they mean different things. Electronegativity refers to the amount of pull that an atom can have on an outside electron because it wants the electron. Ionization energy means the amount of energy it takes to remove one electron from an atom.
- Tue Dec 03, 2019 12:51 pm
- Forum: Biological Examples
- Topic: cisplatin
- Replies: 5
- Views: 417
Re: cisplatin
The Cl atoms don't directly attach to the DNA. The Cl atoms are replaced by nitrogen atoms when the cisplatin binds to guanine on the DNA. This is now going into too much depth. Just know its general function.
- Tue Dec 03, 2019 12:50 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Resonance and Formal Charge
- Replies: 4
- Views: 384
Re: Resonance and Formal Charge
Different resonance structures may have different formal charges for the atoms that are double bonded in one and are single bonded in the other. Just look at the overall charge of the molecule and make sure your formal charges add up.
- Tue Dec 03, 2019 12:42 pm
- Forum: Polyprotic Acids & Bases
- Topic: Why is HClO4 stronger than H3PO4?
- Replies: 3
- Views: 1265
Re: Why is HClO4 stronger than H3PO4?
Because the conjugate base of HClO4, which is ClO4 is more stable than the conjugate base of H3PO4, so HClO4 is more likely to disassociate more in solution as H+ ions and ClO4- anions. Eventhough it is polyprotic, to my knowledge it really has no effect on acidity strength. Here is a formal explana...
- Tue Dec 03, 2019 12:40 pm
- Forum: *Particle in a Box
- Topic: Hydrogen Atom
- Replies: 7
- Views: 1101
Re: Hydrogen Atom
When it absorbs a hydrogen atom, then it absorbs energy so the energy change is positive meaning it gained energy.
- Sat Nov 30, 2019 12:11 pm
- Forum: Bronsted Acids & Bases
- Topic: 6A.17b
- Replies: 5
- Views: 359
Re: 6A.17b
SO3 is basic, not acidic. Acidic oxides are oxides that reacts with water to form a solution of a Bronsted acid. SO3 is an example of an acidic oxide because when it reacts with water, it forms H2SO4. SO3 + H20 --> H2SO4. Since H2SO4 is an acid, SO3 is an acidic oxide. It is also useful to not that...
Re: 9C.3d
Na[Fe(OH2)2(C2O4)2]
- Tue Nov 26, 2019 5:02 pm
- Forum: Student Social/Study Group
- Topic: Test 2 and Final
- Replies: 18
- Views: 938
Re: Test 2 and Final
The TA's will decide when to give back Test 2. The final will cover everything since day 1 of class.
- Tue Nov 26, 2019 5:01 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Video Modules
- Replies: 5
- Views: 270
Re: Video Modules
Nope! Lavelle only posts video modules for quantum and fundamentals.
- Tue Nov 26, 2019 5:00 pm
- Forum: Molarity, Solutions, Dilutions
- Topic: Molarity Formula / Calculation
- Replies: 5
- Views: 2974
Re: Molarity Formula / Calculation
Try not to get too caught up in the wordiness of the questions. You need to break everything down so you have just moles of whatever atom/compound you want to find the molarity of and the volume of the solution. Then divide the number of moles by the number of liters to get the concentration.
- Tue Nov 26, 2019 4:58 pm
- Forum: *Liquid Structure (Viscosity, Surface Tension, Liquid Crystals, Ionic Liquids)
- Topic: Hydrogen Bonding/Pi bonds
- Replies: 11
- Views: 1634
Re: Hydrogen Bonding/Pi bonds
Hydrogen Bonds and pi ponds really have nothing to do with each other in my knowledge.
- Tue Nov 26, 2019 4:57 pm
- Forum: Naming
- Topic: Final Exam
- Replies: 3
- Views: 220
Re: Final Exam
Dr. Lavelle provided his own chart. I think it is linked above in one of the other replies!
- Tue Nov 26, 2019 4:56 pm
- Forum: Sigma & Pi Bonds
- Topic: Question on Test 2
- Replies: 11
- Views: 932
Re: Question on Test 2
For this question, you had to be able to identify that all the single bonds had a sigma bond in it and that all the double bonds that a sigma bond and a pi bond in it. When counting the number of hydrogen bonding sites you need to include the H-bonds already present and the lone pairs on N,O, or F.
- Tue Nov 19, 2019 8:43 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: How to know which angles are smaller
- Replies: 8
- Views: 503
Re: How to know which angles are smaller
@Leila: The shape of AX2E is bent. The bond angles are 120 degrees. For AX2E2 it is still bent, but the bond angles are 109.5 degrees since the two lone pairs push the two atoms further away from them therefore decreasing the angle.
- Tue Nov 19, 2019 8:37 am
- Forum: Dipole Moments
- Topic: Dipole Induced- Dipole Induced
- Replies: 13
- Views: 1184
Re: Dipole Induced- Dipole Induced
I think you mean to say "induced-dipole induced-dipole." Yes this is the weakest form of interaction since it is synonymous with LDF and Van der Waals forces. So technically it is present to some extent in all molecules. Contrary, "Dipole-Induced-Dipole" is an interaction between...
- Tue Nov 19, 2019 8:35 am
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: Ion-Dipole
- Replies: 2
- Views: 430
Re: Ion-Dipole
The easiest way to explain ion-dipole interaction, is the salt in water example. Lets take NaCl for example. The sodium has a positive charge and the chlorine has a negative charge. So the water molecules will surround the the NaCl ion in such an orientation that the positive hydrogen atom in water ...
- Tue Nov 19, 2019 8:31 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Pi and Sigma bonds
- Replies: 5
- Views: 465
Re: Pi and Sigma bonds
I think the general idea behind pi and sigma bonds that we need to know is determining how many of each there are in a large molecule of some sort. So the basic rule of a single bond having 1 sigma bond, a double bond having 1 sigma and 1 pi bond, and a triple bond having 1 sigma and 2 pi bonds is u...
- Tue Nov 19, 2019 8:29 am
- Forum: Dipole Moments
- Topic: Cancelling Dipole Moments
- Replies: 4
- Views: 374
Re: Cancelling Dipole Moments
Can someone explain more in depth why CH2Cl2 is polar?
- Tue Nov 19, 2019 8:28 am
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: Strength of Intermolecular Forces
- Replies: 3
- Views: 305
Re: Strength of Intermolecular Forces
What Camellia said is correct. However, yesterday I came across the idea that HCl has a stronger bond than HBr since the bond length in HCl is shorter and stronger since Cl has a smaller atomic radii than Br does. How do you know which reasoning to use?
- Wed Nov 13, 2019 2:45 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Topics on Outlines for Test 2
- Replies: 3
- Views: 197
Re: Topics on Outlines for Test 2
To my knowledge Test 2 will only contain information from the end of Chemical Bonds outline and from the Molecular Shape and Structure outline. This is also a good question to ask your TA's
- Wed Nov 13, 2019 2:42 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Week 9 homework
- Replies: 11
- Views: 752
Re: Week 9 homework
That is probably a good question to ask our TAs as I am also wondering the same thing.
- Wed Nov 13, 2019 2:41 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Class grading
- Replies: 12
- Views: 803
Re: Class grading
The class is based of points. The max points is 500. The first test was 50 points, the midterm was 120 points, the HW problems are 50 points, and then the rest is consituted by Chem Community participation, Test 2, and the Final. Your final grade will be determined by the amount of points you earned...
- Wed Nov 13, 2019 2:39 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Regrade requests
- Replies: 3
- Views: 300
Re: Regrade requests
The best course of action would probably be to talk to your TA in the next discussion section or reach out to them via email.
- Wed Nov 13, 2019 2:38 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Midterm grade
- Replies: 4
- Views: 191
Re: Midterm grade
I do not think our scores will be posted online until the next few days. However, we received our physical test grades back after class from our TA's today.
- Wed Nov 13, 2019 2:37 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Midterm Answers
- Replies: 10
- Views: 751
Re: Midterm Answers
Yes, under the chem14A tab on the website, on the bottom right corner these is a link that says midterms solutions.
- Wed Nov 13, 2019 2:36 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Test 2
- Replies: 15
- Views: 871
Re: Test 2
3F and latter sections from the Chemical Bonds Outline, and all the sections from the Molecular Shape and Structure Outlines will appear on the test.
- Sat Nov 09, 2019 3:18 pm
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: Hydrogen bonding
- Replies: 8
- Views: 464
Re: Hydrogen bonding
The high electronegative atoms will be the only ones strong enough to pull away the electron from hydrogen to form the H-bond.
- Sat Nov 09, 2019 3:15 pm
- Forum: Bond Lengths & Energies
- Topic: Midterm
- Replies: 9
- Views: 539
Re: Midterm
According to Dr. Lavelle, we should receive them after lecture on Wednesday
- Sat Nov 09, 2019 3:14 pm
- Forum: Student Social/Study Group
- Topic: Test 2
- Replies: 3
- Views: 361
Re: Test 2
Sure! That would be great
- Sat Nov 09, 2019 3:12 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Best Way To Study?
- Replies: 56
- Views: 3561
Re: Best Way To Study?
Read the textbook in order to fill in gaps in your knowledge from the lecture. Once you think you know the information, then attempt the HW problems to get an accurate representation of how well you know the material.
- Fri Nov 08, 2019 4:29 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Formal Charge Shortcut
- Replies: 3
- Views: 141
Re: Formal Charge Shortcut
An easy way is to count the number of lone electrons, not lone pairs, and add that the number of bonds( so a single bond would be one bond, a double would be two bonds). Then subtract this value from the number of valence electrons for that element.
- Fri Nov 08, 2019 4:27 pm
- Forum: Resonance Structures
- Topic: Bond lengths
- Replies: 11
- Views: 414
Re: Bond lengths
This is due to the fact that the electrons are delocalized. Therefore, the bonds in the structure are a blend of single and double bonds, or in another words they have single and double bond character. Therefore the bond lengths are the same.
- Fri Nov 08, 2019 4:27 pm
- Forum: Resonance Structures
- Topic: Bond lengths
- Replies: 11
- Views: 414
Re: Bond lengths
This is due to the fact that the electrons are delocalized. Therefore, the bonds in the structure are a blend of single and double bonds, or in another words they have single and double bond character. Therefore the bond lengths are the same.
- Mon Oct 28, 2019 10:48 am
- Forum: General Science Questions
- Topic: homework
- Replies: 5
- Views: 217
Re: homework
This weeks HW will be on chemical bonds
- Mon Oct 28, 2019 10:48 am
- Forum: Lewis Structures
- Topic: BrF3
- Replies: 2
- Views: 130
Re: BrF3
Br would be in the center will 3 single bonds to Flourines. Draw in 3 lone pairs for each flourine to complete the octet for them, and add 2 lone pairs onto the Br in the center. In this case, Br is capable is having more than an octet.
- Mon Oct 28, 2019 10:43 am
- Forum: Administrative Questions and Class Announcements
- Topic: Review Sessions
- Replies: 2
- Views: 171
Re: Review Sessions
I had the same question. I emailed my TA and am awaiting a response.