Search found 65 matches
- Sat Mar 16, 2019 10:55 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: cell potential
- Replies: 2
- Views: 517
cell potential
When choosing which half reaction to flip, do we choose the one in which plugging in Ecathode - Eanode will produce the greatest positive number? If so, how does one do that when we want to keep the sign of E values for each half reaction the same? I'm just kinda confused on which reaction we revers...
- Sat Mar 16, 2019 9:15 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Isometric/Isochoric
- Replies: 11
- Views: 1402
Re: Isometric/Isochoric
What does isometric mean? The same as isochoric?
- Sat Mar 16, 2019 9:11 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Frequency factor units
- Replies: 2
- Views: 683
Re: Frequency factor units
I've found that it's sometimes M^-2 * s^-1 because it uses the same units as the rate constant.
- Sat Mar 16, 2019 9:09 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: cell potential
- Replies: 3
- Views: 650
cell potential
For getting an E(total) from two reactions, how do we know when to add and when to subtract? I always thought we needed to do Ecathode - Eanode ...
- Sat Mar 16, 2019 12:38 am
- Forum: Second Order Reactions
- Topic: 7E.3 in 7th edition
- Replies: 3
- Views: 717
Re: 7E.3 in 7th edition
the problem says "the presence of a catalyst provides a reaction pathway in which the activation energy of a certain reaction is reduced from 125 kj to 75 kj, by what factor does the rate increase at 298, all other factors equal?" I tried to do this using the Kr2/Kr1= e^-(Ea2-Ea1)/RT but ...
- Sun Mar 10, 2019 4:56 pm
- Forum: Second Order Reactions
- Topic: pseudo first order rxns
- Replies: 3
- Views: 367
Re: pseudo first order rxns
You use pseudo rate laws are used when all reactant concentrations change. When all reactant concentrations are changing it is difficult to study the rate of the reaction. So in order to study it we assume one reactant concentration is small and the others are so much larger that the concentration ...
- Sun Mar 10, 2019 4:41 pm
- Forum: General Rate Laws
- Topic: writing rate laws
- Replies: 4
- Views: 462
writing rate laws
Is there a difference between rate law and the "rate of consumption of __"?
- Sun Mar 10, 2019 4:40 pm
- Forum: First Order Reactions
- Topic: graph
- Replies: 3
- Views: 2325
graph
Why is it that when graphing first order reactions, it is either exponentially decaying or linear?
- Sun Mar 10, 2019 4:39 pm
- Forum: Second Order Reactions
- Topic: pseudo first order rxns
- Replies: 3
- Views: 367
pseudo first order rxns
Hello! I am confused about the concept of pseudo-first-order reactions. When would we need to use them, and why is it that some reactants would be insignificant to the rate law?
- Sun Mar 03, 2019 7:37 pm
- Forum: Van't Hoff Equation
- Topic: Van't Hoff use
- Replies: 13
- Views: 2138
Re: Van't Hoff use
I have found that we use Vant Hoff when we are either given 2 temperatures and a K or two Ks and a temperature.
- Sun Mar 03, 2019 7:35 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Q and K with the Nernst Equation
- Replies: 3
- Views: 462
Q and K with the Nernst Equation
In order to find out which way the reaction is proceeding, would we have to find both Q and K? Or is there another way where we are able to determine this?
- Sun Mar 03, 2019 7:33 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: concentration cell
- Replies: 2
- Views: 278
concentration cell
What do concentration cells mean? And why are they always 0?
- Mon Feb 25, 2019 3:15 pm
- Forum: Balancing Redox Reactions
- Topic: Balancing redox equations in acidic/basic solutions [ENDORSED]
- Replies: 3
- Views: 439
Re: Balancing redox equations in acidic/basic solutions [ENDORSED]
How do we recognize whether we are dealing with an acidic or basic solution?
- Sun Feb 24, 2019 1:27 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: cell potential
- Replies: 2
- Views: 275
cell potential
What do we need to know about cell potential besides its relation with Gibbs free energy?
- Sun Feb 24, 2019 1:25 pm
- Forum: Balancing Redox Reactions
- Topic: platinum
- Replies: 7
- Views: 697
platinum
When Platinum is added to the cell diagram, should it also be added to the overall chemical equation?
- Sun Feb 24, 2019 1:17 pm
- Forum: Balancing Redox Reactions
- Topic: Test 2 Material
- Replies: 13
- Views: 1362
Re: Test 2 Material
Will acid/base consideration when balancing redox equations be on the test? It's in the textbook but not covered in lecture.
- Sun Feb 17, 2019 8:52 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: vibrational entropy
- Replies: 2
- Views: 308
vibrational entropy
Is there a way to measure vibrational entropy? I know that residual/positional is measured through degeneracy.
- Sun Feb 17, 2019 8:50 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: spontaneity
- Replies: 3
- Views: 362
spontaneity
I'm still unsure on how to visualize spontaneity if it doesn't mean that it happens immediately. Is there a good visual on how to describe spontaneity?
- Sun Feb 17, 2019 8:48 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: delta G
- Replies: 3
- Views: 430
delta G
Besides the fact that delta G indicates that a reaction is in equilibrium, what else can it tell us?
- Sun Feb 10, 2019 10:36 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: 7th edition 4E.5
- Replies: 3
- Views: 456
Re: 7th edition 4E.5
Hi all. I am currently working on 4E.5 in the 7th edition textbook. The question asks to estimate the reaction enthalpy using bond enthalpies for the formation of benzene: 3C2H2(g) --> C6H6(g) 3 C-C triple bonds are broken and 6 C-C 1.5 bonds are formed. Why isn't the formation of 6 C-H bonds inclu...
- Sun Feb 10, 2019 5:53 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: Concept of 3rd Law of Thermodynamics
- Replies: 3
- Views: 334
Re: Concept of 3rd Law of Thermodynamics
Chem_Mod wrote:The concept is that entropy’s theoretical limit is 0 if there is absolute order in a system. We can calculate positional and residual entropy with formulas you learned in class.
What do you mean by absolute order?
- Sun Feb 10, 2019 5:53 pm
- Forum: Calculating Work of Expansion
- Topic: Derivatives and Integrals
- Replies: 5
- Views: 661
Re: Derivatives and Integrals
I think we may need to write out the integrals, but no real integrating since we didn't do any of those in class.
- Sun Feb 10, 2019 5:51 pm
- Forum: Calculating Work of Expansion
- Topic: Reversible vs Irreversible
- Replies: 9
- Views: 832
Re: Reversible vs Irreversible
How come infinitesimally small changes affect reversible systems?
- Sat Feb 02, 2019 6:31 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Heat vs. Temp
- Replies: 9
- Views: 930
Re: Heat vs. Temp
Temperature, essentially, measures heat, since heat is the action/energy (of particles moving) and temperature is a measurement (Kelvin, Celsius, etc.).
- Sat Feb 02, 2019 6:30 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Open, closed, or isolated systems
- Replies: 10
- Views: 39215
Re: Open, closed, or isolated systems
I believe that the question/problem will usually give enough hints as to whether a system is open, closed, or isolated if it was not explicitly stated.
- Sat Feb 02, 2019 6:28 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Midterm Review
- Replies: 14
- Views: 1262
Re: Midterm Review
I believe that Dr. Lavelle will announce midterm review sessions this upcoming week or next week.
- Sat Feb 02, 2019 4:52 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: isolated system
- Replies: 5
- Views: 516
isolated system
If a problem were to include an isolated system, would we be able to do any calculations on it? Or would we just say that everything stays the same?
- Sat Feb 02, 2019 4:46 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Analogy of Boulder
- Replies: 5
- Views: 1019
Re: Analogy of Boulder
If you literally place a boulder on the side of the mountain/hill, it will roll down on its own due to the pull of gravity. We do not expect it to go up, unless another force was acted upon it (say, a machine) that could pull it up.
- Sat Feb 02, 2019 4:44 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: calorimeters
- Replies: 7
- Views: 635
calorimeters
Besides knowing that a bomb calorimeter is an isolated system, should we know anything else about the bomb calorimeter or other types of calorimeters?
- Sat Jan 19, 2019 1:40 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: strong acids and bases
- Replies: 2
- Views: 405
strong acids and bases
Can someone give a quick refresher on how to identify strong acids and bases vs weak acids and bases, and are there pages in the textbook to also help with this? I understand how the two differ when it comes to dissociating in the chemical equations.
- Sat Jan 19, 2019 1:38 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: exothermic/endothermic
- Replies: 3
- Views: 519
exothermic/endothermic
Besides the reaction equation, are there any other ways we can identify whether a reaction is endothermic or exothermic? And are there exceptions to being able to identify this from the equation?
- Sat Jan 19, 2019 1:35 pm
- Forum: Ideal Gases
- Topic: PV=nRT
- Replies: 8
- Views: 1150
Re: PV=nRT
Hi Ryan,
I think we use PV=nRT to support Le Chatelier's principle, but there isn't much else on where you'd use it in class. However, we may have to use the concentration to calculate P, such as in P = (conc) * RT given temperature. R is a constant.
I think we use PV=nRT to support Le Chatelier's principle, but there isn't much else on where you'd use it in class. However, we may have to use the concentration to calculate P, such as in P = (conc) * RT given temperature. R is a constant.
- Sat Jan 12, 2019 9:05 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: doubling pressure
- Replies: 2
- Views: 274
doubling pressure
When talking about Le Chatelier's implications on changing physicial parameters, such as pressure, why did Dr. Lavelle double pressure to find the new initial concentration of the equation : N2 + 3 H2 <=> 2 NH3 ??
- Sat Jan 12, 2019 9:02 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: pressure and temperature
- Replies: 4
- Views: 205
pressure and temperature
Can the effects of changing pressure and temperature on concentration be summarized? I only understand how to increase yield of products by removing products, but unfortunately I didn't learn anything in high school regarding the effects of pressure or temperature.
- Sat Jan 12, 2019 8:54 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Explaining Q<K and Q>K [ENDORSED]
- Replies: 7
- Views: 2301
Re: Explaining Q<K and Q>K [ENDORSED]
You can think of it like a pendulum. When K means the pendulum is in the middle (at equilibrium), Q lets you know how far it is from equilibrium based on its relation to K. If Q swings left, such as the arrow "<", you can visualize it as being driven to products because it is before reachi...
- Fri Dec 07, 2018 11:50 pm
- Forum: Polyprotic Acids & Bases
- Topic: polyprotic acids and bases in equations
- Replies: 3
- Views: 521
polyprotic acids and bases in equations
when writing the proton transfer equilibria equations, do we need to automatically apply polyprotic acids/bases such that for example in H2SO4 it is H2SO4 + H2O -> H3O+ + SO4 2- ? or would it still be HSO4 - ?
- Sun Dec 02, 2018 11:18 pm
- Forum: Biological Examples
- Topic: Cisplatin Example
- Replies: 5
- Views: 649
Re: Cisplatin Example
it forms coordination compounds with DNA to stop cell division. I don't think we need to know the details other than that.
- Sun Dec 02, 2018 11:13 pm
- Forum: Biological Examples
- Topic: Knowledge of Biological Applications for Final
- Replies: 5
- Views: 417
Re: Knowledge of Biological Applications for Final
I believe it's just cisplatin and hemoglobin.
- Sun Dec 02, 2018 10:59 pm
- Forum: Amphoteric Compounds
- Topic: Amphoteric compounds besides water
- Replies: 6
- Views: 545
Re: Amphoteric compounds besides water
Sarah Zhao 4E wrote:So besides water, they get kind of weird.
Hydrogen carbonate, bisulfate, amino acids, BUT MOST IMPORTANTLY (and probably the only one you will need to know) WATER
Can you explain why amino acids would be amphoteric?
- Sun Dec 02, 2018 10:57 pm
- Forum: Bronsted Acids & Bases
- Topic: Questions
- Replies: 2
- Views: 447
Questions
Will questions on the exam be asking characteristics of acids and bases or identifying different types of acids and bases?
- Sun Dec 02, 2018 10:53 pm
- Forum: Dipole Moments
- Topic: dipole
- Replies: 6
- Views: 579
Re: dipole
Luc Galaif wrote:Do we need to know how to draw dipoles for the test?
Yes, and I believe it will also be on the final.
- Sun Dec 02, 2018 10:52 pm
- Forum: Biological Examples
- Topic: Biological Importance of Coordination Compounds
- Replies: 3
- Views: 377
Re: Biological Importance of Coordination Compounds
In the chem review session, we were told that there could be multiple choice questions based on biological examples and that we should memorize the examples in case.
- Sun Dec 02, 2018 10:49 pm
- Forum: Naming
- Topic: Knowing oxidation states
- Replies: 11
- Views: 954
Re: Knowing oxidation states
Becky Belisle 1F wrote:I think it's useful to memorize the oxidation states of the common ligands.
Which are the common ligands that we would need to memorize for?
- Sun Dec 02, 2018 10:48 pm
- Forum: Naming
- Topic: coordination number
- Replies: 1
- Views: 179
coordination number
Does the coordination number (which equals number of bonds) determine the complex?
- Sat Nov 24, 2018 9:52 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Naming the Shape
- Replies: 16
- Views: 1268
Re: Naming the Shape
With the shapes, do we need to memorize the bond angles?
- Fri Nov 23, 2018 10:28 pm
- Forum: Dipole Moments
- Topic: dipole
- Replies: 6
- Views: 579
dipole
in my understanding, a dipole is closely related to polarity - are there instances where a dipole would exist where polarity did not?
- Sun Nov 18, 2018 1:36 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: bond angle
- Replies: 4
- Views: 445
bond angle
Is there a way to calculate bond angle besides memorizing the shapes that are associated with the bond angles?
- Sun Nov 18, 2018 1:33 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Determining Shape
- Replies: 10
- Views: 970
Re: Determining Shape
I think besides just drawing the Lewis structure, what would also help is sketching or imagining the Lewis structure in 3d. The Lewis structure presents you with a very 2d linear version of what the model actually looks like.
- Sun Nov 18, 2018 1:31 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: lone pairs
- Replies: 11
- Views: 881
lone pairs
When there is a lone pair in a molecular shape, is it safe to say a general statement for how the other angles are affected? For example, saying that the angles of 90 and 180 degrees are slightly decreased due to the lone pair or to state a specific angle?
- Sun Nov 11, 2018 11:00 pm
- Forum: Bond Lengths & Energies
- Topic: bond length such as the midterm question
- Replies: 5
- Views: 622
bond length such as the midterm question
Hi,
When determining bond lengths with two differently valued lengths, should we write it as a range or a specific value? I know that on the midterm, any value between was accepted, but would writing a range be considered wrong?
When determining bond lengths with two differently valued lengths, should we write it as a range or a specific value? I know that on the midterm, any value between was accepted, but would writing a range be considered wrong?
- Sun Nov 11, 2018 10:57 pm
- Forum: Resonance Structures
- Topic: Drawing resonance
- Replies: 17
- Views: 1884
Re: Drawing resonance
If the problem itself does not indicate that we have to draw all the different resonance structures, I believe it is not needed.
- Sun Nov 04, 2018 7:51 pm
- Forum: Lewis Structures
- Topic: Expanded octets? + other octet exceptions
- Replies: 3
- Views: 337
Expanded octets? + other octet exceptions
Hi! Which elements follow the expanded octet structures, and what are the other octet exceptions that we have to know?
- Sun Nov 04, 2018 7:50 pm
- Forum: Lewis Structures
- Topic: Lewis Acids and Bases
- Replies: 2
- Views: 278
Lewis Acids and Bases
How much of Lewis acids and bases do we have to know for the midterm?
- Sat Nov 03, 2018 3:59 pm
- Forum: *Shrodinger Equation
- Topic: radial distribution function
- Replies: 1
- Views: 513
radial distribution function
Hi! Do we need to know how to find the radial distribution function or probability density for the midterm? Thanks!
- Sun Oct 28, 2018 1:14 pm
- Forum: Ionic & Covalent Bonds
- Topic: ionization energy
- Replies: 7
- Views: 825
ionization energy
Why is the 2nd ionization energy of an element always higher?
- Sun Oct 28, 2018 1:12 pm
- Forum: Octet Exceptions
- Topic: Octet Exceptions
- Replies: 3
- Views: 347
Octet Exceptions
How come H, He, Li, Be are the octet exceptions?
- Sun Oct 28, 2018 1:02 pm
- Forum: Lewis Structures
- Topic: Dot's in the Lewis Structure
- Replies: 10
- Views: 2286
Re: Dot's in the Lewis Structure
It doesn't matter where you place the dots, but you should make sure to fill up all the sides first before adding more than 4. For example, it's not right to have 3 dots on one side and no dots on the other sides.
- Sun Oct 21, 2018 3:12 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Delta x
- Replies: 1
- Views: 190
Delta x
If the uncertainty equation is delta p * delta x is greater than or equal to 1/2 h/2pi, then can we combine m*delta x (delta p) with delta x so that it's m*delta x^2?
- Sun Oct 21, 2018 3:10 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Equal sign?
- Replies: 1
- Views: 165
Equal sign?
In the book, I saw an example where the final answer used an equal sign instead of a greater than or equal to sign. How important is this sign, and what is its significance?
- Sun Oct 14, 2018 2:32 pm
- Forum: Properties of Light
- Topic: Geiger and Marsden experiment
- Replies: 3
- Views: 217
Geiger and Marsden experiment
Can someone explain the significance of this experiment? I understand that most of the particles passed through but I don't understand why they called the atoms "blobs of positively charged jelly" or why some bounced back.
- Sun Oct 14, 2018 2:25 pm
- Forum: Properties of Light
- Topic: Colors and Frequency
- Replies: 14
- Views: 1662
Colors and Frequency
Do we need to memorize which colors corresponds with which frequency/wavelength/energy of photons? For example, if given a wavelength in nm, do we need to automatically know which color it corresponds to?
- Sun Oct 14, 2018 2:22 pm
- Forum: Properties of Light
- Topic: Speed of Light
- Replies: 41
- Views: 2835
Re: Speed of Light
AustinGrove3B wrote:more specifically 2.99792 x 108. I think in the book they use this (more sig figs) than 3.0 x 108
Would it be advisable to calculate using 2.99792 x 10^8 on the exams? I'm not sure when to apply significant figures - either throughout the problem or just for the final answer.
- Thu Oct 04, 2018 11:59 pm
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: atoms vs molecules vs formula units?
- Replies: 3
- Views: 301
atoms vs molecules vs formula units?
Hello! I would like some clarification on when to use these three units. How would we calculate finding an atom or molecule differently than calculating formula units? Or is it the same process but with different units?
Thanks!
Thanks!
- Thu Oct 04, 2018 11:55 pm
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Molecule vs Formula Unit
- Replies: 4
- Views: 833
Re: Molecule vs Formula Unit
Adding on to the original post, how would you know to label an answer with "formula units" or "molecules"?
- Thu Oct 04, 2018 11:53 pm
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: writing the formula of a molecule
- Replies: 5
- Views: 5881
Re: writing the formula of a molecule
A magnesium ion is Mg2+ Sulfate is SO4 2- Together that makes MgSO4 The heptahydrate basically just adds H2O at the end. Hepta- is a prefix for 7. So the official formula is MgSO4 . 7H2O In chemistry, it's standard to add a little dot between the compound and the hydrate For quizzes/tests, would we...