Search found 61 matches
- Sat Mar 16, 2019 7:18 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Ka stuff
- Replies: 2
- Views: 512
Ka stuff
Sorry, I wasn't sure where to put this question for chem 14b but for Ka and Kb will we be expected to know the general equations including HA and A?
- Sat Mar 16, 2019 6:55 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: lnA
- Replies: 2
- Views: 343
lnA
Why do you add lnA at the end of the Arrhenius equation? other than to make a linear plot, like other than for graphing purposes?
- Sat Mar 16, 2019 6:52 pm
- Forum: General Rate Laws
- Topic: coefficient of product
- Replies: 1
- Views: 475
coefficient of product
when finding the rate law and after you solve for the intermediate do you always put the coefficient of the product?
- Sun Mar 10, 2019 12:50 pm
- Forum: General Rate Laws
- Topic: Problem
- Replies: 1
- Views: 279
Problem
For the first order reaction cyclobutane (g) 2 ethylene(g) at 800K, the half-life
is 0.43 seconds. Calculate the time needed for the concentration of cyclobutane
to fall to 1/64 of its initial value.
is 0.43 seconds. Calculate the time needed for the concentration of cyclobutane
to fall to 1/64 of its initial value.
- Sun Mar 10, 2019 12:49 pm
- Forum: General Rate Laws
- Topic: Problem
- Replies: 1
- Views: 264
Problem
Calculate the time required for the concentration of N2O(g) to decrease from
0.75M to 0.33M. The rate constant for the reaction is k= 6.8 x 10-3 /s
0.75M to 0.33M. The rate constant for the reaction is k= 6.8 x 10-3 /s
- Sun Mar 10, 2019 12:47 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: Order
- Replies: 2
- Views: 348
Order
What is the most efficient way to determine the order of a reaction and what does that information tell you?
- Sun Mar 03, 2019 7:23 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Kinetics and spontaneity
- Replies: 2
- Views: 386
Kinetics and spontaneity
I know chemical kinetics is used to analyze the speed or rate of a reaction but can it be used to analyze spontaneity?
- Sun Mar 03, 2019 7:06 pm
- Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
- Topic: Porous Disk and Salt Bridge
- Replies: 13
- Views: 1223
Porous Disk and Salt Bridge
So I understand that both the Porous Disk and Salt Bridge are used to transfer ions but is one more efficient than the other? If so, why? Just curious
- Sun Mar 03, 2019 7:05 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: 326
Concentration Cell
In a concentration cell, why is the Ecell always 0?
- Sun Mar 03, 2019 7:03 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Gases and Liquids in Cell Diagrams
- Replies: 3
- Views: 573
Gases and Liquids in Cell Diagrams
When making a cell diagram do you include gasses and liquids? Especially liquids like H2O, and the reactants are in aqueous form? Like isn't it implied that there is water on both sides on the reaction, so we shouldn't put it?
- Fri Feb 22, 2019 2:09 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: -charge x E = Wmax
- Replies: 2
- Views: 317
-charge x E = Wmax
Can someone explain why the charge is negative again? Also why is it the maximum work for this equation?
- Fri Feb 22, 2019 2:07 pm
- Forum: Balancing Redox Reactions
- Topic: Standard Oxidation Potentials?
- Replies: 1
- Views: 196
Standard Oxidation Potentials?
Do standard oxidation potentials exist? If so, why don't we use them? Is it because of the equation? Would things become more complicated?
- Fri Feb 22, 2019 2:06 pm
- Forum: Balancing Redox Reactions
- Topic: Positive E means Favorable
- Replies: 2
- Views: 1086
Positive E means Favorable
Today Lavelle stated that when the standard reduction potential is positive that the reactant is favorable. Did I understand this wrong? Can someone explain please?
- Fri Feb 15, 2019 2:14 pm
- Forum: Van't Hoff Equation
- Topic: Assumptions
- Replies: 1
- Views: 311
Assumptions
Dr. Lavelle mentioned that when using the ln K2/K1 equation you must assume that entropy and enthalpy are both constant. If these assumptions are not true is there a different equation? or are they always true...?
- Fri Feb 15, 2019 2:08 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: At Equilibrium G
- Replies: 6
- Views: 713
At Equilibrium G
For the equation G=-RTlnK
when K<1 then G is positive which means R>P right? (non-spontaneous?)
and when K>1 then G is negative which means R<P right? (spontaneous?)
when K<1 then G is positive which means R>P right? (non-spontaneous?)
and when K>1 then G is negative which means R<P right? (spontaneous?)
- Fri Feb 15, 2019 2:06 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Equation based on equilibrium
- Replies: 5
- Views: 508
Equation based on equilibrium
Can someone please explain the G=G+RTlnQ equation please. Lavelle wrote Q is reaction quotient not K, is he just emphasizing that its not at equilibrium? I thought it was....?
- Fri Feb 08, 2019 1:00 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Constant Pressure Problem
- Replies: 2
- Views: 319
Constant Pressure Problem
In a problem in which there is constant pressure, mols are given as well as the heat of the asks for the change in enthalpy, why would you divide the the heat by the mols?
- Fri Feb 08, 2019 12:47 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: Residual Entropy
- Replies: 5
- Views: 540
Residual Entropy
In lecture Lavelle did an example using four carbon monoxide molecules and mentioned that there is no translational/rotational movement and I was wondering what else must be stagnant for this system to have residual entropy?
- Fri Feb 08, 2019 12:44 am
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Spontaneity
- Replies: 2
- Views: 301
Spontaneity
In lecture, Lavelle said that if the change in internal energy or the change in enthalpy were negative, we could ask if the reaction could be predicted to occur. He also mentioned that we could question if the reaction would be spontaneous and that it was likely to be. How would we know that/figure ...
- Sun Feb 03, 2019 8:25 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Hess's Law
- Replies: 3
- Views: 396
Hess's Law
Will we ever have to do Hess's law problems in which we consider the changes in temperature?
- Sun Feb 03, 2019 8:24 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Standard Enthalpy of Formation
- Replies: 3
- Views: 328
Standard Enthalpy of Formation
The literal definition for enthalpy of formation is that 1 mol of a compound is formed from pure elements in their stable form. My questions are does it always have to be 1 mol of the product, and are we meant to memorize the standard forms of all elements?
- Sun Feb 03, 2019 8:10 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Enthalpy of Formation
- Replies: 2
- Views: 359
Enthalpy of Formation
So when calculating bond enthalpies the final answer will be an enthalpy of formation, correct? So I know that bond enthalpies are always positive, but the formation can be pos or neg based on if the number of reactants/products, right?
- Fri Jan 25, 2019 11:46 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Solving bond enthalpies
- Replies: 3
- Views: 277
Solving bond enthalpies
Why is it reactants minus products when solving for the enthalpy of the reaction using bond enthalpies?
- Fri Jan 25, 2019 11:45 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: bond enthalpies
- Replies: 5
- Views: 573
bond enthalpies
Will the values for bond enthalpies between atoms always be positive?
- Fri Jan 25, 2019 11:43 am
- Forum: Phase Changes & Related Calculations
- Topic: Reverse fusion
- Replies: 3
- Views: 491
Reverse fusion
Can someone please explain how the reversr rxn for fusion is exothermic please.
- Fri Jan 18, 2019 12:36 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Kw
- Replies: 6
- Views: 597
Kw
When are the concentration of hydronium and hydroxide equal? when in pure water?
- Fri Jan 18, 2019 12:33 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Adding concentration vs amount
- Replies: 1
- Views: 227
Adding concentration vs amount
If a question asks how the system would be affected after adding a certain concentration (molarity) is that different from adding say grams? please explain difference abnd how you would answer.
- Fri Jan 18, 2019 12:29 pm
- Forum: Ideal Gases
- Topic: Pressure in terms of mols
- Replies: 3
- Views: 465
Pressure in terms of mols
Is the pressure lower when there are less mols because they are less collisions? or why?
- Fri Jan 11, 2019 10:57 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Charles’s Law
- Replies: 4
- Views: 242
Charles’s Law
Can someone please explain Charles’s law in depth.
- Fri Jan 11, 2019 10:56 am
- Forum: Ideal Gases
- Topic: Pressure of gasses
- Replies: 5
- Views: 772
Pressure of gasses
On page 151 of the 6th edition of our textbook there is an equation: P=dhg which solves for the pressure of a gas based on the height of a column of liquid and its density and gravity. I was wondering if we would need to know this calculation, if so can someone please explain it in depth because the...
- Fri Jan 11, 2019 10:50 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Liquids in Chemical Equilibrium
- Replies: 1
- Views: 185
Liquids in Chemical Equilibrium
We discussed how liquids that were used as solvents were not to be included in solving the chemical equilibrium constant because at the beginning and end of the rxn there was an insignificant change to the volume, what about those liquids in rxn that are not solvents?
- Fri Jan 11, 2019 10:48 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Pure Substances
- Replies: 2
- Views: 292
Pure Substances
In lecture we discussed how liquids and solids were not included in the chemical equilibrium equation because they were pure substances. Can someone please explain why gases are not pure substances.
- Wed Nov 28, 2018 10:00 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Radicals
- Replies: 2
- Views: 350
Radicals
In the VSEPR formula, would you apply a radical as a "lone pair"
- Wed Nov 28, 2018 8:37 pm
- Forum: Hybridization
- Topic: Radicals
- Replies: 3
- Views: 537
Radicals
When determining hybridization, do radicals count as regions of electron density?
- Thu Nov 22, 2018 10:28 pm
- Forum: Dipole Moments
- Topic: Canceling?
- Replies: 3
- Views: 421
Canceling?
When dipole moments cancel that means that the molecule is nonpolar correct? Also, since dipole moments have the same magnitude (right?) the only way to cancel them is by direction, right? Is there any other way for them to cancel?
- Thu Nov 22, 2018 10:27 pm
- Forum: Sigma & Pi Bonds
- Topic: Drawing bonds
- Replies: 3
- Views: 396
Drawing bonds
Will we learn how to draw the sigma and pi bonds? Will this be on the test? Can someone explain how they intersect and what it means?
- Thu Nov 22, 2018 10:25 pm
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: on test? [ENDORSED]
- Replies: 3
- Views: 527
on test? [ENDORSED]
This subject won't be on the test, correct? Also when will we learn molecular orbital theory?
- Thu Nov 22, 2018 10:24 pm
- Forum: Hybridization
- Topic: determining shape from given information
- Replies: 3
- Views: 395
determining shape from given information
could you determine the geometry of a molecule (VSEPR) if given only its hybridization? if given its hybridization and another aspect? if so what aspect?
- Thu Nov 22, 2018 10:19 pm
- Forum: Hybridization
- Topic: reason for hybridization
- Replies: 9
- Views: 10265
reason for hybridization
why does hybridization exist?
- Thu Nov 22, 2018 10:18 pm
- Forum: Hybridization
- Topic: d-block
- Replies: 3
- Views: 380
d-block
In hybridization, when combing the s, p and d block where does that hybridization fall in terms of energy compared to the regular electron configuration ?
- Thu Nov 22, 2018 9:51 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Transition Metals
- Replies: 1
- Views: 243
Transition Metals
How does VSEPR work for the transition metals? Does it still apply?
- Thu Nov 22, 2018 9:50 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Isoelectric species
- Replies: 2
- Views: 228
Isoelectric species
How does VSEPR work for isoelectric species? Does it still apply?
- Thu Nov 22, 2018 9:43 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Drawing Structures on Test
- Replies: 11
- Views: 1001
Drawing Structures on Test
When drawing the lewis structures on the test and using the wedges, if we "misplace" an axial or equatorial atom will that be a major mistake?
- Thu Nov 08, 2018 5:50 pm
- Forum: Lewis Acids & Bases
- Topic: Lewis acids and bases
- Replies: 1
- Views: 316
Lewis acids and bases
This may be the wrong section to ask this question... However, in my discussion section, we were learning about Lewis acid and bases and my TA did an example with Al+3 and H20. He was saying that for the structure you would need 6H20 molecules and then he drew it and it was very confusing. If anyone...
- Thu Nov 08, 2018 5:21 pm
- Forum: Dipole Moments
- Topic: Permanent Dipole Moments
- Replies: 4
- Views: 4026
Permanent Dipole Moments
Can someone explain permanent dipole moments to me please? As well as their importance
- Thu Nov 08, 2018 5:17 pm
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Polarizability
- Replies: 2
- Views: 327
Polarizability
In discussion section, we went over how charge and volume are the factors that determine the "polarizing power" or a cation or the "polarizability" or an anion. In this list of ions, which would have the greater "polarizing power"? Please explain :)
Rb+, Sr+2, Be+2
Rb+, Sr+2, Be+2
- Tue Oct 30, 2018 12:48 am
- Forum: Resonance Structures
- Topic: Drawing Resonance Structures
- Replies: 1
- Views: 225
Drawing Resonance Structures
Just curious, but when Lavelle says that resonance is the average of the arrangement of atoms with different arrangements of electrons, how would this be shown? Is it only with the double-sided arrows? Or with line structures like he showed with Benzene?
- Tue Oct 30, 2018 12:43 am
- Forum: Sigma & Pi Bonds
- Topic: What each bond refers to
- Replies: 3
- Views: 405
What each bond refers to
In class Lavelle referred to pi and sigma bonds when discussing resonance but never really went into much detail. Can anyone explain what each refers to?
- Tue Oct 30, 2018 12:42 am
- Forum: Formal Charge and Oxidation Numbers
- Topic: Stable Structure in SO4^-2
- Replies: 1
- Views: 705
Stable Structure in SO4^-2
In class, Lavelle said that the most stable structure for a sulfate ion is with two double bonds because the formal charge matched the given charge of the ion. If this is so, why wasn't the first structure we created (with only single bonds) as stable? Is it because the FC values for the two double ...
- Sun Oct 28, 2018 1:10 pm
- Forum: Trends in The Periodic Table
- Topic: Smallest ionic radius [ENDORSED]
- Replies: 6
- Views: 832
Smallest ionic radius [ENDORSED]
If you're comparing P^-3, Cl^-, S^-2, which would have the smallest ionic radius? Would you have to compare their protons at this point?
- Sun Oct 28, 2018 1:08 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: D Block
- Replies: 1
- Views: 153
D Block
In the D-block, when we write the 3d before the 4s, that means that electrons come from the 4s orbital when ions are formed right?
- Sun Oct 28, 2018 1:03 pm
- Forum: Ionic & Covalent Bonds
- Topic: Determining the number of electrons in a compound [ENDORSED]
- Replies: 2
- Views: 333
Determining the number of electrons in a compound [ENDORSED]
Can someone explain to me again how to add up the electrons in a compound like Lavelle did in class with SO4^-2 please
- Sat Oct 20, 2018 4:06 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Superscript
- Replies: 3
- Views: 306
Superscript
Does the superscript in configurations (2s^2) correlate to how many electrons can be in that orbital?
- Sat Oct 20, 2018 4:05 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: P orbital
- Replies: 2
- Views: 286
P orbital
How do you know which value (-1,0,1) corresponds to the axes px,py,pz? Will these be on the test: determining which axes.
- Sat Oct 20, 2018 4:03 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Realistic Values
- Replies: 1
- Views: 268
Realistic Values
How does one determine whether or not values calculated for uncertainty of velocity or position are realistic? How does one know they are realistic?
- Tue Oct 09, 2018 1:07 am
- Forum: Properties of Light
- Topic: Wavelength vs Frequency
- Replies: 7
- Views: 632
Re: Wavelength vs Frequency
Also in an experiment, how would one alter the wavelength and frequency of light?
- Tue Oct 09, 2018 1:05 am
- Forum: Photoelectric Effect
- Topic: Other Sources of energy
- Replies: 1
- Views: 185
Other Sources of energy
In the photoelectric experiment shown to us in class the source of energy was light. Could another source of energy be used and produce the same or similar outcomes (a similar amount of electrons emitted)?
- Tue Oct 09, 2018 1:02 am
- Forum: Properties of Electrons
- Topic: Energy per photon equation
- Replies: 3
- Views: 389
Energy per photon equation
Just to clarify, in the equation: E=hv
as well as in the photoelectric experiment, the energy of per photon is reliant solely on the frequency?
as well as in the photoelectric experiment, the energy of per photon is reliant solely on the frequency?
- Fri Oct 05, 2018 12:06 pm
- Forum: SI Units, Unit Conversions
- Topic: SI Units on tests
- Replies: 5
- Views: 566
SI Units on tests
In high school, for tests we were told to make sure that all our answers were in MKS (meters, kilograms and seconds) or just in SI units in general. For Lavelle’s exams are there specific units that he expects all answers to be converted to?
- Fri Oct 05, 2018 12:02 pm
- Forum: Properties of Light
- Topic: Energy Function
- Replies: 1
- Views: 157
Energy Function
In the equation: E= -hR/n^2 (solves for the energy of electrons as a function of n)
What are the variables and how do they contribute to finding the energy of the electron?
What are the variables and how do they contribute to finding the energy of the electron?
- Fri Oct 05, 2018 11:45 am
- Forum: Empirical & Molecular Formulas
- Topic: When finding empirical formula
- Replies: 4
- Views: 495
When finding empirical formula
When beginning to find the empirical formula, do you always start with the mass percentage composition if it is not given?