Search found 39 matches
- Fri Mar 16, 2018 10:42 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Slow Step Vs. Steady State Approximation
- Replies: 3
- Views: 590
Slow Step Vs. Steady State Approximation
Hi! When is it necessary to use steady state approximation to find the rate of a reaction as opposed to just using the slow step? Thanks!
- Tue Mar 13, 2018 9:55 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Arrhenius when Temperature Changes
- Replies: 3
- Views: 463
Arrhenius when Temperature Changes
Does it matter which set of numbers is used as k1 and T1, and k2 and T2?
- Mon Mar 05, 2018 8:40 pm
- Forum: General Rate Laws
- Topic: rate of change of species
- Replies: 2
- Views: 364
rate of change of species
The outline for Chapter 15 says that we should be able to "show how the rate of change of one species in a reaction is related to that of another species." What exactly does this mean (like what equations do we need to know) ?
- Mon Mar 05, 2018 12:56 am
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3053343
Re: Post All Chemistry Jokes Here
Why did the hipster get burnt?
Because he touched the beaker before it was cool.
Because he touched the beaker before it was cool.
- Mon Mar 05, 2018 12:54 am
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: Units of k
- Replies: 8
- Views: 1398
Re: Units of k
You find the units of k by cancelling out all other known units in the rate law, like all of the different mol/L and the units for time. You can also just memorize them, because they're the same for each rxn order. Zero order: mol/L/s or basically, Molarity/Time First Order: 1/s, or basically 1/Time...
- Mon Mar 05, 2018 12:47 am
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3053343
Re: Post All Chemistry Jokes Here
A photon checks into a hotel and is asked if it needs any help with its luggage.
"No," it says. "I'm traveling light."
"No," it says. "I'm traveling light."
- Mon Feb 19, 2018 11:13 am
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: 14.23A
- Replies: 1
- Views: 319
14.23A
One of half reactions needed to calculate the overall cell potential in 14.23A is 2Hg -> Hg 2 2+ + 2e- and the cell potential for the reverse reaction in the textbook is listed as +0.79, which the solutions manual uses in the calculations for E o cell. I'm confused why they didn't flip the cell pote...
- Sun Feb 18, 2018 12:55 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell Diagrams and Cell Potential
- Replies: 1
- Views: 297
Cell Diagrams and Cell Potential
I heard/read a lot that the anode is conventionally on the left of the cell diagram and the cathode is on the right. However, there's also a rule that mentions that a negative cell potential means that the cathode is actually on the left. Do we have to draw cell diagrams differently when the cell po...
- Wed Feb 14, 2018 12:40 am
- 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: Units for Standard Molar Entropy [ENDORSED]
- Replies: 1
- Views: 320
Units for Standard Molar Entropy [ENDORSED]
In the homework problem 9.25, the units used in the final answer for residual molar entropy is J/K. Why would the units for residual molar entropy be in J/K and not J/K/mol?
- Sun Feb 11, 2018 10:46 pm
- Forum: Van't Hoff Equation
- Topic: Different versions of van't Hoff
- Replies: 2
- Views: 528
Different versions of van't Hoff
Is there an advantage to using either form of the van't Hoff equation? I know there's the version in the textbook and the version that Lavelle recommended in class, but are there certain times when it's better to use one form or the other? Thanks!
- Sun Feb 11, 2018 10:35 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: delta S total
- Replies: 2
- Views: 432
Re: delta S total
Think of it as though the universe always wants to have more entropy. Just as Lavelle showed in class, a gas will always want to spread out and fill the container it's in. It's never going to want to huddle up densely packed in a corner of a room by itself; it, and everything in the universe, will w...
- Sun Feb 11, 2018 10:33 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: About the unit for standard gibbs free energy of a reaction
- Replies: 2
- Views: 440
Re: About the unit for standard gibbs free energy of a reaction
That is only necessary when the question specifically asks, "What is the Gibbs Free Energy for one mole of _____?" and they will specifically tell you which molecule needs to have one mole. If there is more than one product for the equation, all that matters is that the specific molecule t...
- Sun Feb 11, 2018 10:28 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Which is more stable: Fe3O4 or Fe2O3?
- Replies: 2
- Views: 853
Re: Which is more stable: Fe3O4 or Fe2O3?
I believe the stability of Fe 3 O 4 and Fe 2 O 3 were mentioned in problem 9.81, and in that problem, it was important to write out the equation that involves the two of them, which is 4Fe 3 O 4 + O2 -> 6Fe 2 O 3 . This Gibbs Free Energy for this forward reaction is negative and the reverse is posit...
- Sun Feb 04, 2018 10:48 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Equipartition Theorem
- Replies: 3
- Views: 497
Re: Equipartition Theorem
We usually don't consider vibrational energy because most molecules don't vibrate under standard conditions.
- Sun Feb 04, 2018 10:46 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Higher Molar Entropy
- Replies: 4
- Views: 846
Re: Higher Molar Entropy
A good way to define molar entropy is just the amount of entropy in one mole of the given substance. Although it's important to remember that when it's mentioned, it's usually referred to as "standard molar entropy," meaning that it's asking for the molar entropy at standard conditions. Th...
- Sun Feb 04, 2018 10:40 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: 9.27 Entropy
- Replies: 3
- Views: 482
Re: 9.27 Entropy
You don't need to do any calculations. You just explain that since Br has a higher atomic mass, it has higher molecular complexity (a fancy way of saying that its electrons have more energy levels that they can jump between), and that gives HBr more entropy.
- Sat Jan 27, 2018 3:45 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: Finding W
- Replies: 3
- Views: 442
Finding W
Is there a specific way to best find W? Other than drawing out the different possible microstates?
- Sat Jan 27, 2018 3:24 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3053343
Re: Post All Chemistry Jokes Here
A u! Did you take my gold?
A g, never mind, it's just silver.
A g, never mind, it's just silver.
- Sat Jan 27, 2018 3:05 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Units for Entropy
- Replies: 4
- Views: 467
Units for Entropy
Why are the units for entropy sometimes J/K and other times J/K/mol?
- Mon Jan 22, 2018 7:11 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Equipartition Theorem - Test 1
- Replies: 1
- Views: 340
Equipartition Theorem - Test 1
Do we need to know the equipartition theorem for Test 1? I don't recall learning it in class.
- Sun Jan 21, 2018 7:44 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Heat of Combustion & Heat of Formation
- Replies: 3
- Views: 448
Heat of Combustion & Heat of Formation
Is heat of combustion the same thing as the heat of formation, except during a combustion reaction? Or is it more similar to the reaction enthalpy?
- Sun Jan 21, 2018 5:39 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: 8.53b - kJ/mol
- Replies: 1
- Views: 345
8.53b - kJ/mol
For 8.53b, which reads The reaction of 1.40 g of carbon monoxide with excess water vapor to produce carbon dioxide and hydrogen gases in a bomb calorimeter causes the temperature of the calorimeter assembly to rise from 22.113C to 22.799C. The calorimeter assembly is known to have a total heat capac...
- Mon Jan 15, 2018 12:24 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: 8.27b - how to find n
- Replies: 1
- Views: 293
8.27b - how to find n
8.27 reads "Calculate the work for each of the following processes beginning with a gas sample in a piston assembly with T=305 K, P=1.79 atm, and V= 4.29 L: (a) irreversible expansion against a constant external pressure of 1.00 atm to a final volume of 6.52 L; (b) isothermal, reversible expans...
- Sun Jan 14, 2018 10:49 am
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Molar heat capacity
- Replies: 2
- Views: 436
Re: Molar heat capacity
Heat capacity is dependent on temperature, as you mentioned with C v = ΔU/ΔT (equation for heat capacity at a constant volume). To find the molar heat capacity at a constant volume, you take C v and divide it by however many moles of substance you have. You're looking for the heat capacity per unit ...
- Sun Jan 14, 2018 10:32 am
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Why isn't heat a state function?
- Replies: 2
- Views: 743
Why isn't heat a state function?
I'm having a hard time seeing the differences between heat and enthalpy. What happens when calculating heat that leads it to /not/ be a state function?
- Sun Jan 14, 2018 10:19 am
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Heat Capacity
- Replies: 1
- Views: 312
Re: Heat Capacity
At constant volume, all work is lost as heat (no work). Therefore, ΔU = q. The equation for heat capacity at a constant volume therefore, Cv = ΔU/ΔT, is derived from ΔU = q and c = q/ΔT.
At constant pressure, ΔH = q. So we substitute that into c = q/ΔT, and we get Cp = ΔH/ΔT.
At constant pressure, ΔH = q. So we substitute that into c = q/ΔT, and we get Cp = ΔH/ΔT.
- Sun Dec 10, 2017 12:48 am
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Coordination Sphere
- Replies: 1
- Views: 334
Re: Coordination Sphere
Never mind haha I got it. For anyone wondering, the coordination sphere is specifically referring to the central atom/ion and the ligands attached to it. So if given an entire molecule consisting of more than just the coordination compound, you disregard the other atoms/molecules attached to to the ...
- Sun Dec 10, 2017 12:41 am
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Coordination Sphere
- Replies: 1
- Views: 334
Coordination Sphere
Hi!
I know it's a bit late, but what exactly is a coordination sphere, and what do we need to know about its geometry? Thanks!
I know it's a bit late, but what exactly is a coordination sphere, and what do we need to know about its geometry? Thanks!
- Tue Dec 05, 2017 8:39 pm
- Forum: Biological Examples
- Topic: Chemotheraphy Examples [ENDORSED]
- Replies: 3
- Views: 746
Chemotheraphy Examples [ENDORSED]
The syllabus for chapter 17 on the website says we need to know "well-known examples of coordination compounds used as chemotherapy drugs." Is this something he mentioned in a lecture or something in the textbook? I can't seem to find anything on it.
- Mon Dec 04, 2017 6:54 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: EDTA
- Replies: 2
- Views: 504
EDTA
How is EDTA a hexadentate?
- Sun Dec 03, 2017 5:27 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Dentates
- Replies: 6
- Views: 889
Re: Dentates
Unless it's one of the more common coordination compounds where you're expected to know whether it's a bidentate etc, drawing out the Lewis diagram is the best thing to do to figure it out.
- Mon Nov 27, 2017 8:19 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: 17.33
- Replies: 4
- Views: 971
Re: 17.33
Did you have to draw out the Lewis diagrams to figure that out?
- Sun Nov 26, 2017 8:49 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: 11.13 Part C
- Replies: 2
- Views: 386
Re: 11.13 Part C
Gases are pretty much always as partial pressure, and solutes (aq) more often appear in concentration (mol/L). Usually, the only time gases are written in mol/L are when they give you moles and liters in the equation.
- Sat Nov 25, 2017 2:36 pm
- Forum: Naming
- Topic: Roman Numerals
- Replies: 1
- Views: 234
Roman Numerals
In toolbox 17.1, the name for [Fe(NCS)(OH2) 5 ] ]2+ with an Fe-N bond is thiocyanato( k N)pentaaqua(III) iron. I'm not 100% sure, but are the roman numerals meant to describe iron? And if so, are there any particular rules as to where the roman numerals are placed? I'm more used to seeing them come ...
- Mon Nov 13, 2017 7:09 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: lone pairs in trigonal bipyramidal shape
- Replies: 2
- Views: 1773
Re: lone pairs in trigonal bipyramidal shape
If the lone pair is axial, it interacts with three atoms instead of the (only) two atoms it would interact with as an equatorial. As an equatorial lone pair, it would just interact with the axial atoms. The molecule prefers this because it takes less energy.
- Mon Nov 13, 2017 6:57 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: CO2 vs. H2O
- Replies: 6
- Views: 6636
CO2 vs. H2O
Hi! What exactly makes carbon dioxide non-polar while H2O is polar? I know that it has to do with its dipole moments, but I'm unsure how you can look at the dipole moments and determine polarity. Thanks!
- Wed Nov 08, 2017 7:31 pm
- Forum: Electronegativity
- Topic: Electronegativity and Bond Strength
- Replies: 4
- Views: 1871
Electronegativity and Bond Strength
Is there a correlation between electronegativity and bond strength?
- Mon Oct 23, 2017 10:07 am
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: magnetic quantum number - orientation
- Replies: 1
- Views: 501
magnetic quantum number - orientation
Hi guys! I know that the magnetic quantum number can be positive or negative, but which one indicates clockwise or counterclockwise? And how does the electron's orientation change when the magnetic quantum number equals 0?
- Wed Oct 18, 2017 11:09 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Test 2
- Replies: 5
- Views: 710
Re: Test 2
The above post is correct - 1.5 is the furthest material that the test covers. All the material we are learning this week are part of the next section.