Search found 70 matches
- Sat Mar 16, 2019 10:35 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: n value
- Replies: 3
- Views: 579
Re: n value
In electrochemistry, the equation is deltaG = -nFE, and n is equal to the change in electrons in the redox half reactions.
- Sat Mar 16, 2019 10:34 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: kB
- Replies: 1
- Views: 429
Re: kB
kB is Boltzmann's constant and is provided on the equations sheet. (1.38 * 10^-23 J/K)
- Sat Mar 16, 2019 10:33 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Determining n
- Replies: 6
- Views: 843
Re: Determining n
"Delta n as in moles" would be the change in moles from there reactant to product side. For the combustion reaction CH4 + 2O2 > 2H2O + CO2, delta n would be negative 2 because water is a liquid.
- Sat Mar 16, 2019 5:05 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Nernst
- Replies: 14
- Views: 1234
Re: Nernst
Just making sure, n could never equal 0 since there is always a transfer of electrons right?
- Sat Mar 16, 2019 5:03 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Ecell Always Positive
- Replies: 4
- Views: 1352
Re: Ecell Always Positive
We have the equation deltaG = -nFEcell. For galvanic cells, the reaction is spontaneous and therefore Ecell must be positive because deltaG is negative. Not sure if this was a bit roundabout but that's how I think of it.
- Sat Mar 16, 2019 5:00 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Intermediates
- Replies: 1
- Views: 248
Intermediates
How do we determine intermediates in a reaction?
- Sat Mar 16, 2019 12:35 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Nernst Equation
- Replies: 2
- Views: 345
Re: Nernst Equation
I believe you can use the 0.05916V equation when the temperature is at 25 degrees C. Just remember q would equal 10^((-n(E-E))/0.05916) since its log.
- Sat Mar 16, 2019 12:32 pm
- Forum: Calculating Work of Expansion
- Topic: Integrate Rate Law
- Replies: 2
- Views: 539
Integrate Rate Law
Hello guys. Can anyone help me find a practice problem in the book where we are given conditions for an integrated rate problem (ln[A] vs time gives a straight line) and we have to fint the order? Or something of that nature? I remember a problem in class but I can’t find one in the book that’s quit...
- Sun Mar 10, 2019 11:49 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Final Exam
- Replies: 23
- Views: 1846
Re: Final Exam
chemical equilibrium will be on the final exam as it covers everything we have covered in class so far
- Sun Mar 10, 2019 11:47 pm
- Forum: Zero Order Reactions
- Topic: Graphs
- Replies: 8
- Views: 2224
Re: Graphs
first, second, and zero order reactions have linear plots
- Sun Mar 10, 2019 11:44 pm
- Forum: Second Order Reactions
- Topic: Temperature
- Replies: 6
- Views: 645
Re: Temperature
temperature effects the rate constant
- Sun Mar 03, 2019 11:56 pm
- Forum: Balancing Redox Reactions
- Topic: OH-
- Replies: 5
- Views: 581
Re: OH-
You add OH- in a basic solution to the side of the reaction that has less hydrogen accordingly.
- Sun Mar 03, 2019 11:54 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: how is kinetics different?
- Replies: 17
- Views: 1694
Re: how is kinetics different?
Kinetics relates to how quickly a reaction reaches equilibrium while Thermodynamics relates to the energy stored in a reaction.
- Sun Mar 03, 2019 11:52 pm
- Forum: General Rate Laws
- Topic: The value of K
- Replies: 5
- Views: 469
Re: The value of K
K is not constant per reaction because it fluctuates wit temperature.
- Sun Feb 24, 2019 11:47 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: n in -nFE
- Replies: 14
- Views: 900
Re: n in -nFE
Number of electrons transferred, it signifies whether or not the system is gaining or losing energy.
- Sun Feb 24, 2019 11:46 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gibbs Free Energy Units
- Replies: 5
- Views: 589
Re: Gibbs Free Energy Units
If the question gives certain values per mol then you know to use kJ/mol.
- Sun Feb 24, 2019 11:44 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Test 2
- Replies: 9
- Views: 1132
Re: Test 2
Know entropy and enthalpy as well because there a lot of questions that encompass those as well as GFE.
- Sun Feb 17, 2019 11:42 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gases
- Replies: 3
- Views: 397
Re: Gases
I believe the negative delta g that we typically see when deaing with gases is due to the fact that the entire process is spontaneous.
- Sun Feb 17, 2019 11:24 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Intensive vs extensive
- Replies: 4
- Views: 494
Re: Intensive vs extensive
It is extensive because its magnitude is dependent on the amount of a substance in a given thermodynamic state
- Sun Feb 17, 2019 11:17 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Midterm Grades
- Replies: 35
- Views: 2826
Re: Midterm Grades
In 14A we received them about a week after we took it after lecture.
- Mon Feb 04, 2019 12:05 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Internal energy
- Replies: 5
- Views: 571
Re: Internal energy
the internal energy of a system is the energy within the system, of the entire system, as well as the potential energy of the system as a whole due to external force fields
- Mon Feb 04, 2019 12:02 am
- Forum: Phase Changes & Related Calculations
- Topic: Heat
- Replies: 6
- Views: 577
Re: Heat
When heat is absorbed from the solution q for the solution has a negative value
When heat is absorbed by the solution, q for the solution has a positive value
When heat is absorbed by the solution, q for the solution has a positive value
- Mon Feb 04, 2019 12:01 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Enthalpies
- Replies: 2
- Views: 305
Re: Enthalpies
ΔH°= standard enthalpy change
ΔH°r = standard enthalpy change of reaction
ΔH°f = standard enthalpy change of formation
ΔH°c = the standard enthalpy change of combustion
ΔH°r = standard enthalpy change of reaction
ΔH°f = standard enthalpy change of formation
ΔH°c = the standard enthalpy change of combustion
- Sun Feb 03, 2019 11:59 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Cup of Tea
- Replies: 17
- Views: 2564
Re: Cup of Tea
A system which can interchange mass and energy is considered an open system. A cup of tea is susceptible to the environment.
- Sun Feb 03, 2019 11:56 pm
- Forum: Phase Changes & Related Calculations
- Topic: State Function
- Replies: 10
- Views: 912
Re: State Function
State functions are "variables" that define the state of a system
- Sun Feb 03, 2019 11:47 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: w=PdeltaV
- Replies: 5
- Views: 669
Re: w=PdeltaV
V=(Abase)(H)=A*D
- Sun Feb 03, 2019 11:44 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Le Chatelier's Principle
- Replies: 11
- Views: 1562
Re: Le Chatelier's Principle
Increasing the partial pressure of a reactant shifts reactions towards the products, decreasing the partial pressure of a reactants shifts the reactions towards the reactants.
- Sun Feb 03, 2019 11:23 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Hess's Law
- Replies: 3
- Views: 489
Re: Hess's Law
Hess's law basically states that enthalpy changes are additive. Enthalpy change at each step of a multi-step reaction can be added to give Total Enthalpy Change.
- Sun Feb 03, 2019 11:20 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Bomb Calorimeter
- Replies: 5
- Views: 619
Re: Bomb Calorimeter
I think it was just important to know that the constant V (calorimetry) is associated with it. The problems will say something like "In a constant P calorimeter," so I doubt we'll have to know exactly how it works.
- Sun Feb 03, 2019 11:15 pm
- Forum: Phase Changes & Related Calculations
- Topic: Heating Curve
- Replies: 4
- Views: 425
Re: Heating Curve
Someone explained it to me like this: the energy required for water to go from a liquid to a gas is called the heat of vaporization, and when steam hits your skin, a lot of energy will be released as it condenses into a liquid
- Sun Feb 03, 2019 11:13 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: qv vs qp
- Replies: 9
- Views: 2570
Re: qv vs qp
q(v) is heat at constant volume and q(p) is heat at constant pressure
- Sun Feb 03, 2019 11:08 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Midterm [ENDORSED]
- Replies: 49
- Views: 4998
Re: Midterm [ENDORSED]
In my experience the best way to prepare for professor Lavelle's exams is the practice problems that are assigned. It might sound a bit arbitrary but what I like to do is actually repeat and quickly jot down the steps to each problem after I've completed it. It's worked well for me and I also think ...
- Sun Jan 20, 2019 6:55 pm
- Forum: Ideal Gases
- Topic: Ideal Gas as Approximation
- Replies: 2
- Views: 252
Re: Ideal Gas as Approximation
It is considered an approximation because deviations from ideal gas behavior are small.
- Sun Jan 20, 2019 6:44 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: endo/exothermic rxns
- Replies: 5
- Views: 473
Re: endo/exothermic rxns
We can come to certain conclusions that are more obvious, such as H2 -> 2H being endothermic, because H2 has lower energy than the 2 H's. However, because we are given more complex chemical reactions, it's not always possible.
- Sun Jan 20, 2019 6:40 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Ionization and deprotonation
- Replies: 3
- Views: 130
Re: Ionization and deprotonation
They mean the same thing but I believe we will be more likely to see percent ionization on a test.
- Sun Jan 13, 2019 8:00 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: ICE Tables
- Replies: 3
- Views: 376
Re: ICE Tables
Yes. I believe you can use ICE tables if asked to find equilibrium partial pressures.
- Sun Jan 13, 2019 7:05 pm
- Forum: Student Social/Study Group
- Topic: New to Lavelle
- Replies: 32
- Views: 5341
Re: New to Lavelle
I always make sure to take really good notes in class because while it sounds trivial, lecture is probably one the best resources for doing well on the exams. Also one tip for navigating chem community is going into Quicklinks on the top left and clicking on active topics to respond to questions.
- Sun Jan 13, 2019 6:44 pm
- Forum: Ideal Gases
- Topic: bar or atm
- Replies: 8
- Views: 667
Re: bar or atm
I believe we can use either but I know my TA said that since the textbook uses bar so would she. Just make sure you know that they are pretty much equal
- Sun Dec 09, 2018 1:48 am
- Forum: Biological Examples
- Topic: coordination compounds
- Replies: 2
- Views: 468
Re: coordination compounds
^ you can refer to that chart and also Lyndon Bui mentioned that we should know cisplatin because Lavelle mentioned it in class. It's used to treat cancers.
- Sun Dec 09, 2018 1:40 am
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Polydentate
- Replies: 3
- Views: 454
Re: Polydentate
Polydentate simply means ligands with more than one bonded atom. I believe you can just look at the amount of bonds, so an atom with 4 bonds is tetradentate for example.
- Sun Dec 09, 2018 1:37 am
- Forum: Bronsted Acids & Bases
- Topic: Bronsted acid
- Replies: 9
- Views: 1043
Re: Bronsted acid
It is a strong acid because it loses an H+. It's equation of dissociation is HBr(aq) -> H+(aq) + Br-(aq).
- Sun Dec 09, 2018 1:35 am
- Forum: Electronegativity
- Topic: Polarizing Power and Polarizability
- Replies: 2
- Views: 497
Re: Polarizing Power and Polarizability
Li+ is the smallest cation and also has one less shell than Mg2+
- Thu Dec 06, 2018 4:48 pm
- Forum: Naming
- Topic: OH2 vs H2O
- Replies: 5
- Views: 536
Re: OH2 vs H2O
They are the same and you can write it in both ways.
- Thu Dec 06, 2018 4:46 pm
- Forum: Air Pollution & Acid Rain
- Topic: acid rain
- Replies: 4
- Views: 587
Re: acid rain
I believe it is 2NO2 + H2O -> HNO2 +HNO3
Re: Spelling
There is no such thing as a dumb question. It is spelled ammine.
- Thu Dec 06, 2018 4:40 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Final Exam
- Replies: 7
- Views: 719
Re: Final Exam
Yes I remember my TA going over this in section.
- Thu Dec 06, 2018 4:37 pm
- Forum: Naming
- Topic: Naming Metals
- Replies: 2
- Views: 179
Re: Naming Metals
Yes this is just a rule. For example sulfate is SO42−.
- Thu Dec 06, 2018 4:30 pm
- Forum: Hybridization
- Topic: lone pairs
- Replies: 20
- Views: 2162
Re: lone pairs
Each lone pair is considered a region of electron density so they should be taken into account.
- Thu Dec 06, 2018 4:29 pm
- Forum: Student Social/Study Group
- Topic: Studying
- Replies: 7
- Views: 936
Re: Studying
I am mostly studying my notes and going over practice problems. I think it really helps to compare notes with other students to see if you missed anything.
- Thu Dec 06, 2018 4:26 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Final Exam
- Replies: 22
- Views: 1720
Re: Final Exam
The final will be cumulative with an emphasis on the later topics.
- Thu Dec 06, 2018 4:25 pm
- Forum: Administrative Questions and Class Announcements
- Topic: How to find my posts
- Replies: 163
- Views: 175313
Re: How to find my posts
'Quick links' top left -> 'your posts'
- Thu Dec 06, 2018 4:24 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bent Structures
- Replies: 12
- Views: 1324
Re: Bent Structures
They are all polar.
- Sun Nov 18, 2018 8:01 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Thanksgiving Wednesday Class
- Replies: 19
- Views: 1494
Re: Thanksgiving Wednesday Class
I think the case might be that not every lecture is on the same pace but I could be wrong. From Friday's lecture at noon, he said that we were ahead of schedule and that we would have no class on Wednesday.
- Sun Nov 18, 2018 7:58 pm
- Forum: Dipole Moments
- Topic: Test
- Replies: 15
- Views: 1331
Re: Test
The next test is week 9 in section. It might also have some chemical bond material because its needed for molecular structures.
- Sun Nov 18, 2018 7:57 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Drawing structures
- Replies: 8
- Views: 833
Re: Drawing structures
Lewis structures are the only thing we need to know how to draw in the context of 14a I believe.
- Mon Nov 12, 2018 4:49 am
- Forum: Dipole Moments
- Topic: Hydrogen Bonds
- Replies: 20
- Views: 1574
Re: Hydrogen Bonds
Hydrogen bonds are considered one of the stronger intermolecular attractions, but they are still weaker than covalent and ionic bonds.
- Mon Nov 12, 2018 4:47 am
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Why do the orbitals of an atom only hold a certain amount of electrons?
- Replies: 7
- Views: 1062
Re: Why do the orbitals of an atom only hold a certain amount of electrons?
^simply the way the orbitals are shaped determines the amount of electrons it can hold
- Mon Nov 12, 2018 4:45 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Chapter 4 Homework Number 1
- Replies: 6
- Views: 483
Re: Chapter 4 Homework Number 1
Lone pairs at the central atom repel shared pairs of electrons and make bond angles varied
- Sat Nov 03, 2018 9:34 pm
- Forum: Student Social/Study Group
- Topic: Studying
- Replies: 7
- Views: 936
Re: Studying
I'm going over notes from discussion and practice problems from the book. Also the review sessions are really helpful and I know there are some tomorrow!
- Sat Nov 03, 2018 9:31 pm
- Forum: SI Units, Unit Conversions
- Topic: Unit Conversions
- Replies: 3
- Views: 449
Re: Unit Conversions
Some unit conversions are given on the equation sheet, such as 1 nm = 10-9 m, so I would just review the ones that aren't on the worksheet.
- Sat Nov 03, 2018 9:25 pm
- Forum: Administrative Questions and Class Announcements
- Topic: What the Midterm Will Cover
- Replies: 5
- Views: 489
Re: What the Midterm Will Cover
On the midterms review session schedule, it says that it will be all material covered in Fundamentals, Quantum, Bonding to end of 3.11 (6 Ed.) and to end of 2C (7 Ed.).
- Sun Oct 28, 2018 11:31 pm
- Forum: Ionic & Covalent Bonds
- Topic: Octet Rule
- Replies: 7
- Views: 684
Re: Octet Rule
The octet rule applies to most atoms, but there are exceptions like hydrogen.
- Sun Oct 28, 2018 11:26 pm
- Forum: Significant Figures
- Topic: Sig Figs on MT
- Replies: 2
- Views: 2511
Re: Sig Figs on MT
It won't be a large amount of points taken off but yes you should have the correct amount of sig figs to get full credit. Some questions even have 1 sig fig in them.
- Sun Oct 28, 2018 11:25 pm
- Forum: Lewis Structures
- Topic: Lewis Structures
- Replies: 13
- Views: 1042
Re: Lewis Structures
I believe he said to choose the atom with the lowest ionization energy.
- Fri Oct 26, 2018 12:33 pm
- Forum: Einstein Equation
- Topic: Units
- Replies: 6
- Views: 959
Re: Units
While there are some units on the equation sheet given, it is probably best to know units as best you can.
- Sun Oct 21, 2018 12:19 pm
- Forum: Einstein Equation
- Topic: Numbers to memorize [ENDORSED]
- Replies: 37
- Views: 4247
Re: Numbers to memorize [ENDORSED]
The formula sheet that was given on the first test is the same one that will be given on the second test and third test as well.
- Sun Oct 21, 2018 12:17 pm
- Forum: Einstein Equation
- Topic: Joules per photon?
- Replies: 5
- Views: 685
Re: Joules per photon?
Joules is the correct unit.
- Sun Oct 07, 2018 10:15 pm
- Forum: Balancing Chemical Reactions
- Topic: Where to start [ENDORSED]
- Replies: 10
- Views: 1424
Re: Where to start [ENDORSED]
It usually helps me to look at the entire equation and see if any atoms are already balanced and then balance the others accordingly.
- Sun Oct 07, 2018 10:02 pm
- Forum: Administrative Questions and Class Announcements
- Topic: WHAT TYPE OF CALCULATOR IS ALLOWED ON EXAMS??
- Replies: 5
- Views: 1187
Re: WHAT TYPE OF CALCULATOR IS ALLOWED ON EXAMS??
A non-programmable calculator is allowed on exams.
- Sun Oct 07, 2018 9:52 pm
- Forum: Significant Figures
- Topic: knowing how many sig figs to use
- Replies: 17
- Views: 2241
Re: knowing how many sig figs to use
You should use the amount of significant figures in your answer that corresponds with the least amount of significant figures in any one given value of the problem.