Search found 61 matches
- Sun Mar 17, 2019 3:48 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Equlibrium and catalysts
- Replies: 2
- Views: 488
Equlibrium and catalysts
Do catalysts affect the equilibrium constant or the amount of products/reactants formed?
- Sun Mar 17, 2019 3:45 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Final scores
- Replies: 1
- Views: 472
Final scores
Does anyone know when final grades are usually posted on my.ucla?
- Sun Mar 17, 2019 3:44 pm
- Forum: Balancing Redox Reactions
- Topic: Triprotic
- Replies: 7
- Views: 3722
Re: Triprotic
yes so the correct answer would have been phosphoric acid
- Tue Mar 12, 2019 1:59 am
- Forum: General Rate Laws
- Topic: Derivations
- Replies: 3
- Views: 339
Derivations
Do we have to know how to derive the rate formulas using the derivative/integration?
- Tue Mar 12, 2019 1:52 am
- Forum: Administrative Questions and Class Announcements
- Topic: Lyndon's Review Sheets
- Replies: 9
- Views: 1288
Lyndon's Review Sheets
Did Lyndon already post his review worksheet for the final? If yes, where can I find it?
- Sun Mar 10, 2019 7:14 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Final Exam
- Replies: 23
- Views: 1731
Re: Final Exam
I heard from a UA that there will be one question from each unit and then 2 questions that include several topics at the same time.
- Mon Mar 04, 2019 3:44 am
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Study Advice
- Replies: 73
- Views: 6774
Re: Study Advice
Lyndon's and Karen's sessions are the best in my opinion!
- Mon Mar 04, 2019 3:40 am
- Forum: Administrative Questions and Class Announcements
- Topic: Homework
- Replies: 7
- Views: 829
Re: Homework
The general rule is to choose the problems from the chapters we are currently studying. But I am sure that you can email your TA and talk to him/her about it
- Mon Mar 04, 2019 3:36 am
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Endergonic vs. Endothermic
- Replies: 6
- Views: 1872
Re: Endergonic vs. Endothermic
Endergonic refers to a positive change in Gibbs Free energy while endothermic refers to a positive change in enthalpy.
- Sun Feb 24, 2019 11:54 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Galvanic Cells
- Replies: 2
- Views: 292
Galvanic Cells
Do we have to memorize how to draw the galvanic cells?
- Sun Feb 24, 2019 11:45 pm
- Forum: Balancing Redox Reactions
- Topic: balancing redox reactions
- Replies: 2
- Views: 337
balancing redox reactions
Are there any tips on balancing redox reactions in acidic AND basic environment?
- Thu Feb 21, 2019 11:25 pm
- Forum: Student Social/Study Group
- Topic: Midterm Results
- Replies: 4
- Views: 513
Re: Midterm Results
We got our midterms back yesterday after our lecture ! The TAs handed them back
- Thu Feb 21, 2019 11:24 pm
- Forum: Student Social/Study Group
- Topic: Outline
- Replies: 1
- Views: 251
Re: Outline
we are doing redox reactions right now and that falls into Outline 5-Electrochemistry
- Mon Feb 18, 2019 11:08 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: TEST 3
- Replies: 7
- Views: 979
TEST 3
What are the topics we have to know for our upcoming test ?
- Mon Feb 18, 2019 11:00 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Negative Delta G
- Replies: 7
- Views: 3934
Re: Negative Delta G
the formula for is delta G = delta H - T delta S. So if:
- delta H is positive and delta S is negative, delta G will definitely be positive
- delta H is negative and delta S is positive, delta G will definitely be negative
- delta H is positive and delta S is negative, delta G will definitely be positive
- delta H is negative and delta S is positive, delta G will definitely be negative
- Mon Feb 18, 2019 10:55 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Isolated system
- Replies: 10
- Views: 1243
Re: Isolated system
a bomb calorimeter is an isolated system because no matter or heat can be exchanged through it.
- Mon Feb 11, 2019 12:02 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Constant Vol.
- Replies: 8
- Views: 1030
Re: Constant Vol.
The equation for the work is Pext x change in volume, so if the volume is constant, the change in volume is zero therefore pressure is multiplied by zero which is w=0
- Mon Feb 11, 2019 12:01 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Using R
- Replies: 10
- Views: 963
Re: Using R
All the values of R are in the equation sheet provided to us. To see which R to use, you should check the units, specifically if it uses atm or joules or Torr.
- Sun Feb 10, 2019 11:59 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Midterm #1 14B
- Replies: 17
- Views: 2097
Re: Midterm #1 14B
Ronald Thompson 1F wrote:Is there a solutions guide as well?
Lyndon said that he is not going to post any solutions so you should go to his review session in order to get the solutions.
- Mon Feb 04, 2019 2:34 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Bond Enthalpies
- Replies: 4
- Views: 417
Re: Bond Enthalpies
It is always best to draw Lewis structures so that you don't get confused or forget some bonds if you're visualizing structures in your head.
- Mon Feb 04, 2019 2:32 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Midterm [ENDORSED]
- Replies: 49
- Views: 4713
Re: Midterm [ENDORSED]
The best way to prepare in my opinion is reading the concepts in the book, understanding the sample problems and finally doing ALL homework problems assigned to us. Practice is key.
- Mon Feb 04, 2019 2:30 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: W=2^NA
- Replies: 3
- Views: 407
Re: W=2^NA
The NA represents the number of molecules or atoms in the system, so if there are 2 molecules of C02, for example, the NA would be 2. If you have one mole of CO2, the amount of molecules of CO2 is given by avogadro's number so NA would be Avogadro's number.
- Mon Jan 28, 2019 1:27 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Le Chatelier's Principle
- Replies: 2
- Views: 392
Re: Le Chatelier's Principle
If there are an even amount of moles on either side the reaction is unaffected by a change in pressure.
- Mon Jan 28, 2019 1:26 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Le Chatelier's Principle
- Replies: 3
- Views: 534
Re: Le Chatelier's Principle
Le chateliers principle applies on to reactions at equilibrium as it determines how a change in the system at equilibrium will affect the direction of the reaction.
- Mon Jan 28, 2019 1:25 pm
- Forum: Ideal Gases
- Topic: sre
- Replies: 5
- Views: 566
Re: sre
Standard enthalpy of reaction is the enthalpy change that occurs in a system for a reaction in which it’s reactants and products are in their standard state.
- Mon Jan 21, 2019 1:41 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Inert gas effect on Equilibrium constant
- Replies: 4
- Views: 1007
Re: Inert gas effect on Equilibrium constant
The only factor that can change the equilibrium constant is temperature. Pressure can not change Equilibrium constant but it changes the direction of the reaction only if the change in pressure was caused by a change in volume because in that case there was a change in concentration.
- Mon Jan 21, 2019 1:31 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: pressure and volume
- Replies: 5
- Views: 472
Re: pressure and volume
Only a change in pressure that is caused by a change in volume affects the direction of the reaction because for an increase in volume, for example, causes a decrease in pressure (PV=nRT) and consequently a change in concentration. On the other hand, if the pressure changes because extra inert gases...
- Mon Jan 21, 2019 1:27 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Weak acid and its salt
- Replies: 3
- Views: 217
Re: Weak acid and its salt
No, first and second group cations do not affect pH so we shouldn't take them into account. Also the anions Cl, Br and I do not affect pH.
- Sun Jan 20, 2019 10:39 pm
- Forum: Ideal Gases
- Topic: OH and H3O
- Replies: 10
- Views: 1265
Re: OH and H3O
To distinguish weak acids from strong acids you should just essentially memorize the list of strong acids (they are 7 in total HCl - hydrochloric acid, HNO3 - nitric acid, H2SO4 - sulfuric acid, HBr - hydrobromic acid, HI - hydroiodic acid, HClO4 - perchloric acid and HClO3 - chloric acid). The stro...
- Sun Jan 20, 2019 10:37 pm
- Forum: Ideal Gases
- Topic: ICE table
- Replies: 11
- Views: 1263
Re: ICE table
Ice tables can be used for both molarity and partial pressure because the concept is basically the same (Initial pressure, change in pressure and equilibrium pressure). For partial pressure you would just use Kp instead of Kw.
- Sun Jan 20, 2019 10:32 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Quadratic method for weak acids and bases
- Replies: 1
- Views: 206
Re: Quadratic method for weak acids and bases
I think you might be getting confused because I thought that the ICE and quadratic method was used solely to calculate the pH or pOH of weak acids and bases because for strong ones you just know that they dissociate completely.
- Sat Dec 08, 2018 7:07 pm
- Forum: Acidity & Basicity Constants and The Conjugate Seesaw
- Topic: Ka and Kb
- Replies: 2
- Views: 211
Re: Ka and Kb
No, Ka and Kb are used to calculate the pHs and pOHs of weak acids and bases but we are only working with strong acids and bases that dissociate completely in an aqueous solution.
- Sat Dec 08, 2018 7:06 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Memorizing Acids by name
- Replies: 3
- Views: 716
Re: Memorizing Acids by name
I think that you should memorize all the strong acids (they are 7: HCl, HBr, HI, HClO3, HClO4, H2SO4, HN03). Strong bases are basically all the metal oxides and metal hydroxides
- Sat Dec 08, 2018 7:04 pm
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: ions
- Replies: 4
- Views: 711
Re: ions
A cation is a positive ion, so an atom that has lost one or more electrons thus becoming positively charged
- Fri Dec 07, 2018 4:18 pm
- Forum: Identifying Acidic & Basic Salts
- Topic: Ammonia and phosphoric acid
- Replies: 1
- Views: 395
Re: Ammonia and phosphoric acid
Water is for sure formed only when a strong base is present in the neutralization reaction. In this case ammonia is a weak base.
- Fri Dec 07, 2018 4:13 pm
- Forum: Biological Examples
- Topic: Ligands
- Replies: 6
- Views: 960
Re: Ligands
Chronium - assists insulin in control of blood sugar
Iron - facilitates electron transfer in the oxidation of carbohydrates, proteins and fats
Cobalt - for Vitamin B12
Manganese, Nickel, Copper and Zinc - critical for enzime function.
Iron - facilitates electron transfer in the oxidation of carbohydrates, proteins and fats
Cobalt - for Vitamin B12
Manganese, Nickel, Copper and Zinc - critical for enzime function.
- Sun Dec 02, 2018 3:23 pm
- Forum: Lewis Acids & Bases
- Topic: Weak and Strong Acids/Bases
- Replies: 7
- Views: 752
Re: Weak and Strong Acids/Bases
For the acids, there are in total 7 strong acids that you should just memorize: HCl, HBr, HI, HNO3, HClO3, HClO4, H2SO4. (so the rest would be weak acids). The strong bases, instead you can recognize them as they are always a metal hydroxide (e.g. LiOH, NaOH, KOH...).
- Sat Dec 01, 2018 2:15 pm
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: Induced dipoles
- Replies: 7
- Views: 892
Re: Induced dipoles
Basically, electrons in an atom fluctuate over time and in one instant electrons may accumulate on one part of a molecule making side of the molecule more negative and leaving the other side more positive, becoming, therefore, an instantaneous dipole. An instantaneous dipole moment on one molecule w...
- Sat Dec 01, 2018 2:08 pm
- Forum: Lewis Acids & Bases
- Topic: Lewis and Bronsted
- Replies: 8
- Views: 795
Re: Lewis and Bronsted
In the Bronsted definition, an acid is a proton donor while a base is a proton acceptor. In the Lewis definition instead, an acid is an electron acceptor while the base is the electron donor. While the definition may be different, both Lewis and Bronsted pretty much refer to the same thing.
- Tue Nov 27, 2018 4:44 pm
- Forum: Electronegativity
- Topic: Electronegativity values
- Replies: 2
- Views: 658
Electronegativity values
Are we supposed to memorize electronegativity values? I know the general trend but if it asks for example: which pair has the most ionic character between CH4 and CF4, how am I supposed to know the electronegativity difference exactly.
- Sun Nov 18, 2018 11:43 pm
- Forum: Sigma & Pi Bonds
- Topic: sigma and pi bonds
- Replies: 2
- Views: 174
Re: sigma and pi bonds
A σ bond has cylindrical symmetry while a π bond has a nodal plane that includes the bond axis.
- Sun Nov 18, 2018 11:32 pm
- Forum: Ionic & Covalent Bonds
- Topic: Intra vs Intermolecular forces
- Replies: 9
- Views: 16458
Re: Intra vs Intermolecular forces
Intramolecular forces are harder to break because it would be breaking the actual bonds between atoms. Intermolecular forces are forces between different molecules and include things like London dispersion forces, Van der Waals forces, and dipole-dipole interactions and are easier to break.
- Sun Nov 18, 2018 10:33 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: lone pair influence on shape
- Replies: 12
- Views: 4214
Re: lone pair influence on shape
Electrons are negatively charged and repulse other electrons. A lone pair causes an area of high electron density so electrons repel each other more strongly than bonding pairs causing a distortion in the shape (lower angle).
- Sun Nov 11, 2018 9:22 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: Induced Dipole - Induced Dipole
- Replies: 1
- Views: 106
Re: Induced Dipole - Induced Dipole
The larger the molar mass, the more electrons the atom has. In larger atoms, the valence electrons are farther from the nuclei than in smaller atoms so they are less tightly held and can more easily form temporary dipoles. Also, an atom that has a large cloud of electrons is more easily distorted an...
- Sun Nov 11, 2018 9:09 pm
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Polarization of cation's
- Replies: 2
- Views: 210
Re: Polarization of cation's
Yes cations’ polarizing powers depend on the power of its charge. Smaller atoms have their charges more concentrated in a smaller region so their polarizing power is stronger.
- Sun Nov 11, 2018 5:54 pm
- Forum: Bond Lengths & Energies
- Topic: 7th edition 2D. 13 [ENDORSED]
- Replies: 2
- Views: 443
Re: 7th edition 2D. 13 [ENDORSED]
Yes, you should draw the Lewis structures first the way we always do it (counting valence electrons and following the octet rule) and see which structures contain single, double or triple bonds. The single bonds have the greatest length followed by double and then triple bonds.
- Sun Nov 11, 2018 5:35 pm
- Forum: Coordinate Covalent Bonds
- Topic: coordinate covalent bond
- Replies: 7
- Views: 935
Re: coordinate covalent bond
A coordinate covalent bond is a bond in which one atom provides both electrons in a shared pair for both atoms.
- Sun Nov 04, 2018 12:32 pm
- Forum: Trends in The Periodic Table
- Topic: Question 2.75
- Replies: 2
- Views: 550
Re: Question 2.75
The s-block elements are all located in Group 1 and 2 and they all contain 1 or 2 electrons in their outer shell. They have lower ionization energies so they have the tendency of losing electrons more readily and react with other elements.
- Sun Nov 04, 2018 12:28 pm
- Forum: Lewis Structures
- Topic: Question 3.55 (Sixth Edition)
- Replies: 6
- Views: 614
Re: Question 3.55 (Sixth Edition)
Radicals are molecules that contain one unpaired electron. To answer this question it would be best if you draw the Lewis structures for which one and see which molecule has an unpair electron. You can also identify them by the fact that their number of valence electrons is odd (meaning that at leas...
- Fri Nov 02, 2018 9:17 pm
- Forum: Electronegativity
- Topic: ionic vs. covalent bonding
- Replies: 2
- Views: 320
Re: ionic vs. covalent bonding
Doctor Lavelle says that in these cases we cannot determine directly whether the two atoms will engage in covalent or ionic bonding through that simple rule, and we have to look at the specific cases.
- Sun Oct 28, 2018 7:17 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: 1E 25)
- Replies: 2
- Views: 172
Re: 1E 25)
I think we should know on a general level. Just remember that alkali metals are in group 1. Group 2 are the alkaline earth metals, from group 3 to 12 are transition metals and group 17 contains the Halogens.
- Sun Oct 28, 2018 7:00 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Z effective 2.37
- Replies: 1
- Views: 625
Re: Z effective 2.37
The Zeff is the net positive charge that valence electrons experience from the protons in the nucleus. (a) is false because Zeff is largely dependent on the number of electrons in the atom. This is because the electrons in lower energy levels can shield electrons in higher energy orbitals thus decre...
- Sun Oct 28, 2018 3:42 pm
- Forum: Ionic & Covalent Bonds
- Topic: Friday 10/26/18 lecture
- Replies: 4
- Views: 541
Re: Friday 10/26/18 lecture
I am attaching my notes from the lecture down below. I hope that helps!
- Sun Oct 14, 2018 5:05 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Test #2
- Replies: 3
- Views: 342
Test #2
What topics will the test next week (Test 2) cover? Only the Quantum World?
- Sun Oct 14, 2018 4:24 pm
- Forum: General Science Questions
- Topic: Chemistry Community Posts
- Replies: 8
- Views: 1114
Re: Chemistry Community Posts
A friend of mine asked the TA and he said that extra posts do not roll over the following week.
- Sun Oct 14, 2018 4:22 pm
- Forum: Significant Figures
- Topic: When to round the answers to significant figures
- Replies: 11
- Views: 2575
Re: When to round the answers to significant figures
You should keep as many significant figures as possible when doing your calculations (I usually keep at least 6 decimal places) and then round everything at the very end. Hope this helps
- Sun Oct 14, 2018 4:02 pm
- Forum: Photoelectric Effect
- Topic: Photoelectric Effect Post Module Questions
- Replies: 2
- Views: 271
Re: Photoelectric Effect Post Module Questions
I think it is better to say particle model. A photon is basically a quantized particle of light.
- Sun Oct 07, 2018 10:10 pm
- Forum: Molarity, Solutions, Dilutions
- Topic: Fundamentals E.15
- Replies: 3
- Views: 278
Re: Fundamentals E.15
The M is an unidentified metal that you have to find. The problem gives you the molar mass of M(OH)2 so what you have to do is subtract the molar mass of OH2 off of the molar mass of the entire thing to find the metal M. After doing the calculation you will find that the molar mass of the metal is 4...
- Sun Oct 07, 2018 8:11 pm
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Forumula Units?
- Replies: 2
- Views: 346
Re: Forumula Units?
I think that formula units and molecules are pretty much interchangeable, but formula units refer to ionic compounds like NaCl while molecules refer to molecular compounds. Atoms, instead, are used for single elements or ions.
- Sun Oct 07, 2018 7:26 pm
- Forum: Significant Figures
- Topic: Sig Fig in Relation to Zero
- Replies: 3
- Views: 569
Re: Sig Fig in Relation to Zero
There are 4 major rules regarding zeros and significant figures. 1. Zeros that are between two non-zero digits are significant. (ex. 303 - 3 significant figures) 2. Leading zeros are not significant. (ex. 0.4 - 1 significant figure) 3. Trailing zeros that are to the right of the decimal are signific...
- Sun Oct 07, 2018 2:55 pm
- Forum: Limiting Reactant Calculations
- Topic: Limiting Reactants M19
- Replies: 4
- Views: 432
Re: Limiting Reactants M19
How do we get the info that the composition of caffeine is c(8)H(10)N(4)O(2)? I thought that that was what we were trying to find.