Search found 72 matches
- Sat Mar 16, 2019 8:43 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Final
- Replies: 3
- Views: 1543
Re: Final
Homework questions and skimming over lecture notes always help me
- Sat Mar 16, 2019 8:38 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: k(1)/k(-1)
- Replies: 4
- Views: 617
Re: k(1)/k(-1)
k(1)/k' =K (equilibrium constant)
k' is the reverse or second process
k' is the reverse or second process
- Mon Mar 11, 2019 7:38 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: equations for q
- Replies: 9
- Views: 894
Re: equations for q
We use q=mCdeltaT when mass is given in grams. q=nCdeltaT when moles are given
- Mon Mar 11, 2019 7:32 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Y-Axis Units
- Replies: 2
- Views: 540
Y-Axis Units
When graphing Kinetics what should we look for on the y-axis for the different orders. Also what units do we use for each
- Mon Mar 11, 2019 7:28 pm
- Forum: General Rate Laws
- Topic: Unique Rate Law
- Replies: 4
- Views: 486
Unique Rate Law
What exactly does Unique Rate Law mean?
- Mon Mar 11, 2019 7:27 pm
- Forum: Experimental Details
- Topic: Fast vs Slow
- Replies: 7
- Views: 1233
Re: Fast vs Slow
Normally, the problem will tell you what the rate determining reaction is.
- Mon Mar 11, 2019 7:24 pm
- Forum: General Science Questions
- Topic: Final
- Replies: 7
- Views: 1240
Re: Final
There is no curve, but Dr.Lavelle does adjust the grades a bit so everyone benefits.
- Mon Mar 11, 2019 7:20 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Meaning of k
- Replies: 4
- Views: 665
Re: Meaning of k
k is the rate constant, K is the equilibrium constant
- Sat Mar 02, 2019 10:55 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Test #2
- Replies: 10
- Views: 1076
Re: Test #2
We should get it back in section next week.
- Sat Mar 02, 2019 10:55 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: finding DeltaG
- Replies: 6
- Views: 678
Re: finding DeltaG
There are multiple methods, but deltaG=deltaH-TdeltaS is a powerful equation. Also, we can do G=-nFE
- Sat Mar 02, 2019 10:54 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Order of Cell Diagrams
- Replies: 13
- Views: 1602
Re: Order of Cell Diagrams
I put in order of the reaction. So for Fe2+ to Fe3+ on the anode side would go in that order.
On the reduction (cathode) we would write in order Fe3+,Fe2+
On the reduction (cathode) we would write in order Fe3+,Fe2+
- Sat Mar 02, 2019 10:52 pm
- Forum: Ideal Gases
- Topic: pV=nRT
- Replies: 12
- Views: 2138
Re: pV=nRT
We can use it to solve for variables that might be unknown to us from the problem.
- Sun Feb 24, 2019 5:31 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Test 2
- Replies: 7
- Views: 892
Re: Test 2
Gibbs free energy up to Friday's lecture
- Sun Feb 24, 2019 5:26 pm
- Forum: Student Social/Study Group
- Topic: How are you guys going to study for Test 2?
- Replies: 10
- Views: 1027
Re: How are you guys going to study for Test 2?
I think Homework problems are the best indicator of what's going to be on the exam.
- Sun Feb 24, 2019 5:26 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Spontaneous?
- Replies: 6
- Views: 770
Re: Spontaneous?
If the change in DeltaG is negative then the forward reaction will be spontaneous, but if deltaG is positive then the reverse reaction is spontaneous.
- Sun Feb 17, 2019 8:52 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3865331
Re: Post All Chemistry Jokes Here
Q: Why was the mole of oxygen molecules excited when he walked out of the singles bar?
A: He got Avogadro's number!
A: He got Avogadro's number!
- Tue Feb 12, 2019 1:49 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Acid Base
- Replies: 3
- Views: 2309
Re: Acid Base
Ka is equal to 10^-pka. Once you find the Ka value you can solve for [H+] using the reaction equation. From that we can find pH.
In other words, yes you're correct
In other words, yes you're correct
- Tue Feb 12, 2019 1:43 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Heating Curve
- Replies: 3
- Views: 591
Heating Curve
Can someone please explain how to calculate the entropy through different phase changes using the heating curve as a guide?
Thanks!
Thanks!
- Fri Feb 08, 2019 7:17 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Ideal Gas Laws
- Replies: 4
- Views: 604
Re: Ideal Gas Laws
The ideal gas laws go with PV=nRT where P is 1atm n is 1 mole of gas.
- Fri Feb 08, 2019 7:14 pm
- Forum: Calculating Work of Expansion
- Topic: Conversions to joules?
- Replies: 4
- Views: 842
Re: Conversions to joules?
m^3 is equal to about 1000 L so you'd need to do the conversion of that to give you atm x L. 101.325 atmXL is equal to 1 joule. I believe this conversion is somewhere on the formula sheet for 14B.
- Fri Feb 08, 2019 7:12 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Study Guides
- Replies: 15
- Views: 1287
Re: Study Guides
The online modules might be able to help you understand concepts, but for study guides I would go to TA run review sessions since they typically show problems from past Midterms.
- Sat Feb 02, 2019 9:16 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Bond Angles
- Replies: 5
- Views: 549
Re: Bond Angles
The formation of bonds is exothermic, thus we place a negative sign.
- Sat Feb 02, 2019 9:16 pm
- Forum: Calculating Work of Expansion
- Topic: SI unit for P
- Replies: 6
- Views: 700
Re: SI unit for P
Our textbook uses bar mostly, but atm is technically the proper SI unite for pressure. Since there is only a 1% difference between bar and atm they are interchangeable though.
- Sat Feb 02, 2019 9:14 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: U=q+w
- Replies: 3
- Views: 419
U=q+w
What exactly is delta U and what does the equation for it mean?
- Sat Feb 02, 2019 9:10 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: calorimeters
- Replies: 7
- Views: 644
Re: calorimeters
When we are given questions on exams I believe everything we need to know will be provided to us.
- Sat Jan 26, 2019 7:20 pm
- Forum: Phase Changes & Related Calculations
- Topic: Modules
- Replies: 17
- Views: 1356
Re: Modules
No they are not required but they are good practice
- Sat Jan 26, 2019 7:18 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Signs in bond enthalpies
- Replies: 4
- Views: 455
Re: Signs in bond enthalpies
Yes, just add up the enthalpies of prods-reactants
- Sat Jan 26, 2019 7:17 pm
- Forum: Phase Changes & Related Calculations
- Topic: Sublimation
- Replies: 6
- Views: 572
Re: Sublimation
This does not effect solids or liquids
- Sun Jan 20, 2019 4:58 pm
- Forum: Student Social/Study Group
- Topic: test 1
- Replies: 10
- Views: 1198
Re: test 1
Karyn Nguyen 1K wrote:Will we be tested on concepts (like multiple choice or short answers) or will it just be math problems?
Based on what happened last quarter in 14A, Dr. Lavelle's style is having mostly math problems with a sprinkling of concept questions throughout the exam.
- Sun Jan 20, 2019 4:57 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Le Chatelier's Principle
- Replies: 3
- Views: 250
Re: Le Chatelier's Principle
Changing the concentration doesn't change K because if we take out more reactants the equation will shift in order to make up for the deficient amount of reactants to make the K ratio the same.
- Sun Jan 20, 2019 4:53 pm
- Forum: Student Social/Study Group
- Topic: test 1
- Replies: 10
- Views: 1198
Re: test 1
It is outline 1 with acids and bases
- Sun Jan 13, 2019 12:09 pm
- Forum: Ideal Gases
- Topic: bar or atm
- Replies: 8
- Views: 663
Re: bar or atm
Both are approximately the same thing, but atm is the SI unit for pressure so I'd put your answer in atm if not stated otherwise.
- Sun Jan 13, 2019 12:06 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: solids & liquids
- Replies: 5
- Views: 462
Re: solids & liquids
Solid and liquids don't have concentrations so no reaction would really occur
- Sun Jan 13, 2019 12:05 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Using variables in ICE tables
- Replies: 2
- Views: 259
Re: Using variables in ICE tables
To add onto the above comment the X variable is much easier to use as after you are done assigning variables we would just need to use the quadratic equation.
- Sat Dec 08, 2018 6:06 pm
- Forum: Electronegativity
- Topic: Exceptions
- Replies: 3
- Views: 713
Re: Exceptions
The trend is that across (left to right) a group electronegativity increases and up a period it also increases.
I am unaware of any exceptions to this trend.
I am unaware of any exceptions to this trend.
- Sat Dec 08, 2018 6:05 pm
- Forum: Lewis Acids & Bases
- Topic: Trends of Acids and Bases
- Replies: 2
- Views: 345
Re: Trends of Acids and Bases
I just came out of a chem review session and I was told that on the exam we will have to order from most to least acidic, but they will never make it so that we must confirm an oxoacid with a non-oxoacid. It is always comparing oxoacids with oxoacids and non with non. Just know longer the atomic rad...
- Sat Dec 08, 2018 6:01 pm
- Forum: Identifying Acidic & Basic Salts
- Topic: salts of weak acids and bases
- Replies: 4
- Views: 729
Re: salts of weak acids and bases
Will this be on the chem14A final?
- Sat Dec 08, 2018 6:00 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Oxyacids
- Replies: 4
- Views: 1077
Re: Oxyacids
If the central atom is not the same in a set of oxoacids then the molecule with the central atom with the highest electronegativity will be the most acidic. If the central atoms are the same for a group of oxoacids then we must see the number of Oxygens that are attached to the central atom. The mor...
- Sun Dec 02, 2018 8:20 pm
- Forum: Coordinate Covalent Bonds
- Topic: Oxidation states "()" in naming coord compounds
- Replies: 4
- Views: 688
Re: Oxidation states "()" in naming coord compounds
Yes the central atoms is always positively charged.
- Sun Dec 02, 2018 8:19 pm
- Forum: Hybridization
- Topic: Double and Triple Bonds
- Replies: 17
- Views: 4349
Re: Double and Triple Bonds
No they do not. The only thing that matters is the areas of electron density.
- Sun Dec 02, 2018 8:06 pm
- Forum: Hybridization
- Topic: Sigma bonds
- Replies: 9
- Views: 943
Re: Sigma bonds
3 pi bonds and 1 sigma bond means its a quadruple bond.
- Mon Nov 26, 2018 4:46 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Test 3 Content
- Replies: 3
- Views: 462
Test 3 Content
According to Dr. Lavelle, the test will be on Chapter 3 (3.12 6th edition) and all of chapter 4, but my TA and I believe other TA's did review content in their sections that is outside of this text (like Acids and Bases and Intermolecular forces). Will this additional content also be included on Tes...
- Fri Nov 23, 2018 2:22 pm
- Forum: Lewis Structures
- Topic: Homework #4.13 (C)
- Replies: 2
- Views: 354
Re: Homework #4.13 (C)
It is more stable in terms of formal charge like this. Plus this doesn't break the octet rule.
- Fri Nov 23, 2018 2:20 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: VSEPR RULE 3
- Replies: 4
- Views: 468
Re: VSEPR RULE 3
A double bond will count as one electron density so it doesn't affect the shape of the molecule.
- Fri Nov 23, 2018 2:19 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Test 3
- Replies: 10
- Views: 994
Re: Test 3
Test 3 will be more conceptual based rather than calculations.
- Sat Nov 17, 2018 9:19 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: VSEPR Shapes
- Replies: 4
- Views: 527
Re: VSEPR Shapes
The amount of lone pairs around the central atom also matters as in a T Shape there are 2 lone pairs on the central atom that makes the other atoms move over. On Trigonal Planer the lone pairs of the other atoms push eachother to make a triangle
- Sat Nov 17, 2018 9:14 pm
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: AXE
- Replies: 7
- Views: 750
Re: AXE
Well X is the number of possible bonds and E is the number of lone pairs. So you'd have to memorize this combination for each shape.
- Sat Nov 17, 2018 9:13 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: VSEPR Model
- Replies: 3
- Views: 326
Re: VSEPR Model
Technically no you would just need to memorize the shapes and when each geometrical figure should be applied. I will admit though that the formula will definitely help.
- Sat Nov 10, 2018 2:08 pm
- Forum: Electronegativity
- Topic: Electronegativity
- Replies: 8
- Views: 754
Re: Electronegativity
More electronegative means that the element more greatly wants another electron to fill its octet.
- Sat Nov 10, 2018 2:06 pm
- Forum: Ionic & Covalent Bonds
- Topic: Hydrogen bonding
- Replies: 7
- Views: 1360
Re: Hydrogen bonding
The increased bond length makes the bonds stronger.
- Sat Nov 10, 2018 2:05 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Molecular Shape
- Replies: 2
- Views: 237
Re: Molecular Shape
We won't be required to draw a VSEPR model, but a tetrahedral model doesn't have any lone pairs as exhibited in CH4.
- Sat Nov 10, 2018 2:03 pm
- Forum: Bond Lengths & Energies
- Topic: MIDTERM Bond Length Question
- Replies: 15
- Views: 1613
Re: MIDTERM Bond Length Question
I got 130 pm because I took the average of the 140pm and 120pm.
- Sun Nov 04, 2018 1:35 am
- Forum: General Science Questions
- Topic: Midterm
- Replies: 3
- Views: 345
Re: Midterm
The difficulty level should be comparable to the homework problems
- Sat Nov 03, 2018 11:49 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: s-block, p-block, d-block
- Replies: 3
- Views: 282
s-block, p-block, d-block
Hi just confirming for the midterm we'll only have to be responsible for the configuration of all of the s-block, all the p-block, and just the first row of the d-block?
- Sat Nov 03, 2018 4:38 pm
- Forum: Student Social/Study Group
- Topic: Sig Figs on Midterm
- Replies: 13
- Views: 1595
Sig Figs on Midterm
My TA wasn't particularly strict on SigFigs on Tests #1 and #2. Will it be more of a factor for the midterm?
- Sat Oct 27, 2018 10:10 pm
- Forum: Lewis Structures
- Topic: Periodic Table Trends
- Replies: 3
- Views: 165
Re: Periodic Table Trends
Both are 2 different things but the trend is the same.
- Sat Oct 27, 2018 9:24 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Is homework graded for correctness or completeness?
- Replies: 5
- Views: 904
Re: Is homework graded for correctness or completeness?
It is graded on completeness
- Sat Oct 27, 2018 7:46 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Delta X relationship with Delta P
- Replies: 3
- Views: 2573
Re: Delta X relationship with Delta P
I believe that deltaP and deltaX are inversely proportional. A good rule of thumb is that variables on the same side of an equation are inversely proportional, while variables on different sides of an equation are directly proportion. For example, in p=mv, p and v are directly proportional (p and m ...
- Sat Oct 27, 2018 7:35 pm
- Forum: Ionic & Covalent Bonds
- Topic: Bond
- Replies: 9
- Views: 927
Re: Bond
I believe the bond is stronger when there are more bonds. So in terms of energy needed to break the bonds single<double<triple. Also, interestingly, for the length of a bond the more bonds an atom has the shorter the bond. So a triple bond is shorter than a double bond and a double bond is shorter t...
- Sun Oct 21, 2018 1:25 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Lecture Question on Orbitals
- Replies: 4
- Views: 462
Lecture Question on Orbitals
During the lecture, Dr.Lavelle gave an example where n=2, l=1, and m=-1
From this, he told us this is an electron in 2px state. I don't exactly understand how he got the "x" from this information.
From this, he told us this is an electron in 2px state. I don't exactly understand how he got the "x" from this information.
- Sun Oct 21, 2018 1:20 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: Where does this section end in the textbook? [ENDORSED]
- Replies: 2
- Views: 277
Re: Where does this section end in the textbook? [ENDORSED]
For the exam, we will only need to go up to Quantum Numbers and Orbitals.
- Sun Oct 21, 2018 1:16 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Test 2 Material
- Replies: 9
- Views: 693
Re: Test 2 Material
Dr.Lavelle said that everything in Quantum World up to the information presented on Friday's lecture is what we will be tested on. In other words, the lecture from Friday is the cutoff.
- Sun Oct 21, 2018 1:15 pm
- Forum: Properties of Light
- Topic: TEST 2
- Replies: 7
- Views: 848
Re: TEST 2
It is confirmed that we won't need to memorize any of them
- Sun Oct 21, 2018 1:11 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Heisenbergy Uncertainty Equation
- Replies: 3
- Views: 387
Re: Heisenbergy Uncertainty Equation
The equation he gave in class is correct.
- Sat Oct 13, 2018 1:19 pm
- Forum: Limiting Reactant Calculations
- Topic: Test 1
- Replies: 5
- Views: 649
Re: Test 1
On the exam, we were supposed to box our answers, so I'm pretty sure that if you boxed the right answer it would negate the "doodles"
- Sat Oct 13, 2018 1:15 pm
- Forum: Limiting Reactant Calculations
- Topic: Test 1
- Replies: 5
- Views: 776
Re: Test 1
It would make sense to get our grades back next time we go into discussion yes.
- Sat Oct 13, 2018 1:15 pm
- Forum: Properties of Light
- Topic: Grades
- Replies: 2
- Views: 307
Re: Grades
I believe the syllabus does state that we won't know our grades until the end of the quarter since the class is set up on a bell curve of some sorts (only meant to help your grade).
- Sun Oct 07, 2018 5:08 pm
- Forum: Properties of Light
- Topic: Chapter 1 Homework
- Replies: 6
- Views: 618
Chapter 1 Homework
Is Chapter 1 homework due in our next discussion period or is it due on the one after that?
- Sun Oct 07, 2018 3:04 pm
- Forum: Empirical & Molecular Formulas
- Topic: Molecular Formula
- Replies: 12
- Views: 609
Re: Molecular Formula
All you have to do is count the atoms out for the molecular formula.
- Sun Sep 30, 2018 5:03 pm
- Forum: SI Units, Unit Conversions
- Topic: Length Units
- Replies: 15
- Views: 1532
Re: Length Units
Typically, yes we should just infer that we are supposed to use SI units
- Sun Sep 30, 2018 5:01 pm
- Forum: SI Units, Unit Conversions
- Topic: Avogadro #
- Replies: 9
- Views: 1205
Re: Avogadro #
Avogadro's number is pretty much just "things." So for instance, if you want to turn moles to molecules you'd multiply the moles you have by 6.022x10^23 molecules
- Sun Sep 30, 2018 4:58 pm
- Forum: General Science Questions
- Topic: First Homework
- Replies: 3
- Views: 306
Re: First Homework
Remember we only have to do 7 problems from the hw list on the syllabus