Search found 62 matches
- Sat Mar 16, 2019 10:57 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Activated Complex
- Replies: 1
- Views: 511
Re: Activated Complex
The activated complex I believe is what forms when molecules in a reaction collide in the right orientation to form products. How temperature affects this is that with increasing temperature, there are more collisions, with higher energy (and are able to overcome the energy barrier/activation energy...
- Sat Mar 16, 2019 10:53 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: How to know which conducting element to add?
- Replies: 3
- Views: 554
Re: How to know which conducting element to add?
I'm pretty sure you can always add Platinum if you're missing an inert conductor on one side of the cell. I think you can add any solid metal as your conductor, but Platinum is what is standard. I hope this helps!
- Sat Mar 16, 2019 10:46 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: different types of cells
- Replies: 1
- Views: 462
Re: different types of cells
I'm pretty sure voltaic and galvanic cell are the same (convert chemical energy to electrical energy, standard cell potential is always positive). Electrolytic cells convert electrical energy to chemical energy, and use spontaneous reactions to drive nonspontaneous reactions, the standard cell poten...
- Sun Mar 10, 2019 4:26 pm
- Forum: General Rate Laws
- Topic: Writing Rate Laws
- Replies: 3
- Views: 461
Re: Writing Rate Laws
Maybe it is because when we are looking at reaction rates, we are looking at initial concentrations, when a reaction first starts. At this point in time no products have been formed, so they would not be included in the rate law, since they are not affecting the rate.
- Sun Mar 10, 2019 4:23 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: The temperature reaction changes from spontaneous to nonspontaneous?
- Replies: 1
- Views: 416
Re: The temperature reaction changes from spontaneous to nonspontaneous?
You use the equation delta G = delta H - Tdelta S, and by plugging in your known values of delta H and S, you make G equal to zero and solve for T. That temperature, T (when G = 0) is when the reaction changes from nonspontaneous to spontaneous and vice versa.
- Sun Mar 10, 2019 4:21 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Catalysts
- Replies: 6
- Views: 781
Re: Catalysts
I believe that by lowering the activation energy of a reaction, catalysts increase the speed of a reaction.
- Sun Mar 03, 2019 6:56 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Pt inert electrode
- Replies: 9
- Views: 1826
Re: Pt inert electrode
Athena L 1B wrote:Is Pt(s) the only other substance you would add in any scenario?
I think you can add any inert conductor (I think any solid metal), but Pt(s) is just the most commonly used.
- Sun Mar 03, 2019 6:53 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: delta G = 0 ??
- Replies: 5
- Views: 2899
Re: delta G = 0 ??
delta G standard is equal to zero when K=1, which I believe is very rare.
- Sun Mar 03, 2019 6:50 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Class Curve
- Replies: 11
- Views: 1804
Re: Class Curve
I would assume 50-72% or so would be a C- and then the rest of the grading would be on a normal scale. I'm sure you could ask your TA though, or professor Lavelle.
- Sun Feb 24, 2019 3:57 pm
- Forum: Balancing Redox Reactions
- Topic: Test 2 Material
- Replies: 13
- Views: 1407
Re: Test 2 Material
Does anyone know if we will be asked to draw a cell diagram for Test 2?
- Sun Feb 24, 2019 3:56 pm
- Forum: Balancing Redox Reactions
- Topic: Balancing Redox Reactions in Acidic / Basic Conditions
- Replies: 1
- Views: 237
Balancing Redox Reactions in Acidic / Basic Conditions
Can someone explain how to balance redox reactions in acidic or basic conditions? How do you know what to use to balance out everything???
- Sun Feb 24, 2019 3:51 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Inert Conductors
- Replies: 3
- Views: 452
Inert Conductors
Can someone please explain what inert conductors are, and why they are helpful in redox reactions? Thank you
- Sun Feb 17, 2019 11:51 am
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Isolated system
- Replies: 10
- Views: 1321
Re: Isolated system
The internal energy of an isolated system is constant, and the entropy of an isolated system increases in the course of any spontaneous change, according to the first and second laws of thermodynamics.
- Sun Feb 17, 2019 11:48 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: Derivations
- Replies: 3
- Views: 694
Re: Derivations
The equation is called the Van't Hoff Equation, and it helps show temperature dependence of K! It can be used to find K at different temperatures.
- Sun Feb 17, 2019 11:44 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Differences in Gibbs Free Energy
- Replies: 3
- Views: 433
Re: Differences in Gibbs Free Energy
I think Dr. Lavelle also mentioned that when K<1, enthalpy dominates over entropy, and the reaction will be non-spontaneous
- Sun Feb 17, 2019 11:34 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: At Equilibrium G
- Replies: 6
- Views: 713
Re: At Equilibrium G
If K = 0, is the reaction at equilibrium?
- Sun Feb 17, 2019 11:32 am
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Calculating Standard Entropy of Fusion
- Replies: 2
- Views: 590
Re: Calculating Standard Entropy of Fusion
Because at the freezing temperature is when it goes from liquid to solid, so it's also the melting point, where it goes from solid to liquid. So you use the same temperature.
- Wed Feb 13, 2019 3:34 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Lyndon's HOTDOG MIDTERM REVIEW SESSION!! FINALLY!
- Replies: 49
- Views: 11849
Re: Lyndon's HOTDOG MIDTERM REVIEW SESSION!! FINALLY!
dgerges 4H wrote:I also got that the other part of w=9.12 from w=-pdv. so i got a total of 11.45kj or 1.145x10^5j for w. is this correct?
I also got that for work
- Sun Feb 03, 2019 9:39 pm
- Forum: Phase Changes & Related Calculations
- Topic: Phase Changes
- Replies: 2
- Views: 352
Re: Phase Changes
It only doesn't change temperature when the phase change is occurring, because the energy being provided to or leaving the system is going towards breaking /forming bonds, not increasing or decreasing the temperature. Once the phase change is finished, then the energy will go towards changing temper...
- Sun Feb 03, 2019 9:36 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Midterm [ENDORSED]
- Replies: 49
- Views: 5070
Re: Midterm [ENDORSED]
Definitely doing all the homework problems assigned, because I know sometimes textbook problems are put on the midterm / final verbatim.
- Sun Feb 03, 2019 9:34 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Hess's Law
- Replies: 2
- Views: 335
Re: Hess's Law
I know in the textbook sometimes just the final equation is given and not the intermediate equations that must be be set up and manipulated to solve for the final equation, but I'm pretty sure for this class that the intermediate equations and their enthalpies will be given in the problem so that al...
- Mon Jan 28, 2019 9:18 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Hess's Law (Method 1)
- Replies: 4
- Views: 523
Re: Hess's Law (Method 1)
In addition to that, sometimes you'll need to multiply one of the delta H's if the final reaction requires two moles of one of the substances, and the given delta H is for one mole. So you have to make sure that the reactions match with the amount of moles required in the final reaction, if that mak...
- Mon Jan 28, 2019 9:15 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: When to use which method for calculating reaction enthalpies
- Replies: 4
- Views: 415
When to use which method for calculating reaction enthalpies
How do you know which of the three methods to use when given a specific problem? Like when would you use Hess's Law vs. Bond Enthalpies vs. Standard Enthalpies of formation?
- Mon Jan 28, 2019 9:12 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Bond Enthalpies
- Replies: 7
- Views: 698
Bond Enthalpies
Why are bond enthalpies the least accurate way of measuring reaction enthalpies?
- Sun Jan 20, 2019 7:11 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Removing products
- Replies: 10
- Views: 3943
Re: Removing products
I believe the only way to change K is to change the temperature of a reaction.
- Sun Jan 20, 2019 7:10 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Bars vs. Molarity
- Replies: 5
- Views: 610
Re: Bars vs. Molarity
bars I believe is a unit of pressure, like atm, so if given this, you would be finding Kp, versus when given molarity, that is the concentration of a molecule, and you would find Kc.
- Sun Jan 20, 2019 7:08 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: endo/exothermic rxns
- Replies: 5
- Views: 478
Re: endo/exothermic rxns
The easiest way to tell if a reaction is endothermic or exothermic is by the change in enthalpy (delta H), which I believe will be given for these types of reactions.
- Sun Jan 13, 2019 2:28 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 11.49 6th Edition
- Replies: 2
- Views: 284
Re: 11.49 6th Edition
I believe it is because the molar concentration of a pure substance, such as a liquid or solid, does not change in a reaction! So, since it doesn't change, it wouldn't affect the ICE table!
- Sun Jan 13, 2019 2:25 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: True or False regarding reaction mixture [ENDORSED]
- Replies: 10
- Views: 854
Re: True or False regarding reaction mixture [ENDORSED]
I believe so.
- Sun Jan 13, 2019 9:54 am
- Forum: Ideal Gases
- Topic: Denoting brackets/parentheses
- Replies: 9
- Views: 2215
Re: Denoting brackets/parentheses
I'm pretty sure brackets indicate concentration so for Kc [H20] indicates the concentration of water, but with Kp you have (PCl2). You don't need brackets to indicate concentration for this because the P indicates the pressure of the gas. I hope this helps!
- Mon Dec 03, 2018 9:12 am
- Forum: Naming
- Topic: Naming the Shape
- Replies: 6
- Views: 638
Re: Naming the Shape
I would say the easiest way is just to draw out the compound, especially if it is not too large of a molecule. It's also probably the easiest way to check your answer.
- Mon Dec 03, 2018 9:09 am
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Bronsted vs Lewis
- Replies: 2
- Views: 228
Re: Bronsted vs Lewis
I think in class it was stated that either definition will work for this class, and both sufficiently cover what we need to know.
- Mon Dec 03, 2018 9:08 am
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Orbitals
- Replies: 3
- Views: 639
Re: Orbitals
I don't think you have to memorize the different energy values of the different orbitals. Just know that s is always the lowest energy, and then p. Once you get to the fourth row, s fills up first because its a lower energy, but then once one electron is in the 3d orbital, that becomes your lowest, ...
- Sun Nov 25, 2018 6:02 pm
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: hydrogen bonding
- Replies: 4
- Views: 910
Re: hydrogen bonding
Hydrogen bonding is a type of dipole-dipole bond, that is stronger than other dipole-dipole bonds, as well as ion-dipole, dipole-induced dipole, and van der Waals / London dispersion forces. Hydrogen bonds can only occur between a hydrogen atom and a N, O, or F atom, because these atoms have very hi...
- Sun Nov 25, 2018 5:57 pm
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: induced-dipole
- Replies: 4
- Views: 706
Re: induced-dipole
molecules held in a polar covalent bond have dipoles. An induced dipole can happen to an element in a nonpolar covalent bond, when near a polar molecule, because the partial charge of that molecule will repel the electrons in the nonpolar molecule
- Sun Nov 18, 2018 9:46 am
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: Dipole moments
- Replies: 1
- Views: 186
Re: Dipole moments
I think you would have to draw out the Lewis Structures and then add in the arrows for the dipole moments, making the arrows larger or smaller depending on the difference in electronegativity between the atoms being bonded. From that image you would look at the directions the arrows are pointing, an...
- Sun Nov 18, 2018 9:39 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Polar or nonpolar [ENDORSED]
- Replies: 1
- Views: 721
Re: Polar or nonpolar [ENDORSED]
I think for molecules like that, it is possible for it to have different isomers which are both polar and nonpolar. My TA did an example in discussion with C2F2H2, a similar molecule, and there were three isomers, one of which was nonpolar because the polarities cancel each other out. This isomer th...
- Sun Nov 18, 2018 9:35 am
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: Sigma and Pi Bonds
- Replies: 5
- Views: 715
Re: Sigma and Pi Bonds
The first bond that two atoms make is a sigma bond. If two atoms have a double bond (i.e O=O) then they will have one sigma bond and one pi bond. If two atoms have a triple bond, like Nitrogen with Nitrogen, then there will be one sigma bond, and two pi bonds. So if two atoms are bound by more than ...
- Sun Nov 11, 2018 7:12 pm
- Forum: Ionic & Covalent Bonds
- Topic: Bond Length
- Replies: 3
- Views: 405
Re: Bond Length
I think it would be given, but in general you should just know conceptually that single bonds are the longest (and weakest), and then double bonds are shorter, and triple bonds are the shortest (and the strongest).
- Sun Nov 11, 2018 10:15 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bond Angles
- Replies: 1
- Views: 343
Re: Bond Angles
I think if another molecule/element was nearby it would only shift the electrons within the molecule, through repulsion of charges, but not affect the actual angles within the molecule.
- Sun Nov 11, 2018 10:14 am
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Polar Bonds with Cations and Anions
- Replies: 1
- Views: 394
Re: Polar Bonds with Cations and Anions
I think if it involves cations and anions its an ionic bond, and polar bonding refers to covalent bonds between elements in their neutral states. The bond is only polar because elements have different electronegativities.
- Sat Nov 03, 2018 11:32 pm
- Forum: Properties of Light
- Topic: 3b on Quantum Test
- Replies: 2
- Views: 311
Re: 3b on Quantum Test
The intensity of the light will decrease (i.e. the lamp will be dimmer). This is because there are now atoms that have a higher threshold energy in the lamp. So, the voltage energy being emitted is not sufficient enough to excite these atoms with a higher threshold energy, to the next energy level, ...
- Sat Nov 03, 2018 11:27 pm
- Forum: Trends in The Periodic Table
- Topic: Second and First Ionization Energy
- Replies: 2
- Views: 374
Re: Second and First Ionization Energy
Ionization energy is the energy it takes to remove an electron from an element. Once one electron is removed, the element has an overall positive charge. Electrons are negative, so they are therefore more attracted to this positively charged element, making them harder to remove.
- Sat Nov 03, 2018 11:25 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Subshells
- Replies: 2
- Views: 537
Re: Subshells
It does have access to its d and f subshells, those shells just aren't filled. This is why elements after row 2 can have an expanded octet (more than 8 electrons), because n=3, which means that l can equal 0,1, or 2 (s, p, and d orbital). Even though none of the elements in row three have any electr...
- Sat Nov 03, 2018 11:21 pm
- Forum: Trends in The Periodic Table
- Topic: Periodic trends of elements diagonal to one another
- Replies: 1
- Views: 271
Re: Periodic trends of elements diagonal to one another
I believe that going down a group has more significance than across a period for the trends. For example, with atomic radius, Arsenic would have a larger radius because it has the 4s 3d and 4p orbitals in addition to the orbitals in fluorine. The same goes for Selenium and Iodine. Although Iodine's ...
- Sat Nov 03, 2018 11:13 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: Quantum number Ms
- Replies: 3
- Views: 706
Re: Quantum number Ms
I don't think we would be able to tell. If a question were to come up on quantum numbers, I think all you would need to know about ms is that it can only be +1/2 or -1/2. Whether it is + or - I believe is arbitrary for this class.
- Sat Nov 03, 2018 11:09 pm
- Forum: Lewis Structures
- Topic: Lewis structures of compounds
- Replies: 2
- Views: 325
Re: Lewis structures of compounds
I think that if the question was assigned, it would be better just to understand it, in case a question on molecules comes up. I believe all of those compounds are salts, so it would make sense that the Lewis structures were written like ionic compounds.
- Sat Nov 03, 2018 11:05 pm
- Forum: Octet Exceptions
- Topic: Copper ion electron structure
- Replies: 3
- Views: 836
Re: Copper ion electron structure
Once there is an electron in the 3d orbital, it has a lower energy than the 4s orbital, meaning that the electron configuration would be written as 3d1 4s2. Copper's neutral state electron configuration is 3d10 4s1. Since electrons are removed from the highest energy level first, the electron in the...
- Sat Nov 03, 2018 11:02 pm
- Forum: Octet Exceptions
- Topic: Ions and Exceptions to the Octet Rule
- Replies: 3
- Views: 725
Re: Ions and Exceptions to the Octet Rule
Zn+ having an electron removed from the 4s orbital isn't an exception to a rule. Once an electron is in the 3d orbital, that orbital has a lower energy than 4s, which would mean the electron configuration is written as 3d1 4s2. Since electrons are removed from the highest energy level (the level wri...
- Sat Oct 27, 2018 1:47 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Radial Distribution Function
- Replies: 2
- Views: 473
Re: Radial Distribution Function
I believe r is the radius and R is the radial wavefunction, which indicates how the wavefunction varies as a particle moves away from the nucleus in any direction. It is a part of the wavefunction equation where Ψ(r, θ , ф) = R(r) x Y(θ, ф)
- Sat Oct 27, 2018 1:39 pm
- Forum: *Particle in a Box
- Topic: Application
- Replies: 4
- Views: 1239
Re: Application
I believe there is an example in the textbook (6th edition) on page 23. It goes through how to calculate the energies of a particle in a box.
- Sat Oct 27, 2018 1:36 pm
- Forum: Trends in The Periodic Table
- Topic: Atomic Radius
- Replies: 7
- Views: 727
Re: Atomic Radius
When an electron is removed, the atom becomes a cation, or a positively charged ion. This positive charge in the atom makes the electrons more attracted to it, and therefore harder to remove.
- Sun Oct 21, 2018 4:45 pm
- Forum: Properties of Light
- Topic: Intensity vs energy
- Replies: 6
- Views: 769
Re: Intensity vs energy
Intensity is increasing the amplitude of the wavelength, so making it larger or smaller. When light is acting as a particle, increasing the intensity is just increasing the amount of photons (not the energy per photon). The reason why intensity was significant was because in the photoelectric experi...
- Thu Oct 18, 2018 6:46 pm
- Forum: Photoelectric Effect
- Topic: units
- Replies: 12
- Views: 1156
Re: units
Wavelength is measured in meters, so always convert to meters! Energy is in Joules. eV, Watts, and cal can all be converted into Joules (the conversion are in the back of the book). So yes, always convert back to meters or Joules
- Thu Oct 18, 2018 6:44 pm
- Forum: *Black Body Radiation
- Topic: Black Body Radiation
- Replies: 2
- Views: 699
Re: Black Body Radiation
Black body radiation is an object that absorbs ALL radiation at all wavelengths. To the extent of my knowledge, it has no real equivalent in everyday life, and the closest example would be something like a black hole. I do not believe that we need to know about black body radiation for this course.
- Sun Oct 14, 2018 9:11 am
- Forum: Properties of Light
- Topic: Moles in photoelectric effect? [ENDORSED]
- Replies: 2
- Views: 276
Re: Moles in photoelectric effect? [ENDORSED]
If the threshold energy is given in Joules/mole, you just have to divide by Avogadro's number (6.022x10^23) in order to cancel the units. Then you will just have Joules and can use that number in your equations.
- Sun Oct 14, 2018 9:08 am
- Forum: Properties of Light
- Topic: E=hv
- Replies: 13
- Views: 1121
Re: E=hv
Tamera Scott 3L wrote:I've also seen E=hf once, does anyone know if that is the same as E=hv?
v is frequency, so I believe f would just be another way to denote frequency.
- Tue Oct 09, 2018 9:44 am
- Forum: Einstein Equation
- Topic: Einstein's Equation: E=hv
- Replies: 11
- Views: 1597
Re: Einstein's Equation: E=hv
the equation shows that the energy per photon is proportional to frequency. As frequency increases, so does the energy per photon. Planck's constant, h, is the proportionality constant that equates v to E.
- Sat Oct 06, 2018 1:22 pm
- Forum: Properties of Electrons
- Topic: Light and Electrons
- Replies: 1
- Views: 190
Light and Electrons
In one of the module's Professor Lavelle mentions that light's affect on electrons is more noticeable because they have a much smaller mass than protons/neutrons. However, would the position of the electron's in the atom also be significant, because they are located in orbitals outside the nucleus?
- Sat Oct 06, 2018 12:54 pm
- Forum: Significant Figures
- Topic: Rounding numbers ending in 5
- Replies: 9
- Views: 919
Re: Rounding numbers ending in 5
I believe it is more standard to round up with numbers ending in 5
- Sat Oct 06, 2018 12:51 pm
- Forum: SI Units, Unit Conversions
- Topic: Avogadro's Number [ENDORSED]
- Replies: 11
- Views: 1437
Re: Avogadro's Number [ENDORSED]
So when asked for atoms of a molecule we can multiply by the mols by Avogadro's number to get number of atoms, but I do not understand how to get molecules from mols? You can do the same thing to get molecules, because moles is just a unit of "something" not just an atom, but also molecul...
- Sat Oct 06, 2018 12:47 pm
- Forum: Properties of Light
- Topic: Electric and Magnetic Fields
- Replies: 1
- Views: 248
Electric and Magnetic Fields
When professor Lavelle was talking about the oscillation of electric and magnetic fields, are both important when looking at electromagnetic radiation / light? Like what is the significance of each? I know he addressed the speed of the electric field, and it's importance in different ranges of visib...