Search found 72 matches
- Mon Mar 11, 2019 4:38 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Reaction Mechanisms
- Replies: 2
- Views: 281
Re: Reaction Mechanisms
I would assume you use the energy of products minus energy of reactants because delta H is a state property not a kinetic property, so therefore the activation energy is not concerned in that aspect.
- Mon Mar 11, 2019 4:34 pm
- Forum: Second Order Reactions
- Topic: Final
- Replies: 32
- Views: 2465
Re: Final
In a review session, the UA said that Lavelle will most likely have 1-2 Kinetics problems, 2 Thermochem/Dynamics, 1 Electrochem. with 8 questions total. Basically everything is fair game for the final with probably one or two questions from each outline.
- Mon Mar 11, 2019 4:31 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Increasing reducing power
- Replies: 4
- Views: 1632
Re: Increasing reducing power
Oxidation and reduction are opposites. So the species that has a higher tendency to oxidize has a higher reducing power. For example if the reduction potential of species 1 was .34v and species 2 was .78v, species 1 is more likely to be oxidized and therefore has a higher reducing power.
- Tue Mar 05, 2019 8:08 pm
- Forum: General Rate Laws
- Topic: Units of Rate Constant
- Replies: 4
- Views: 513
Re: Units of Rate Constant
Yes. For zero order, the rate constant units are mol/Lsec., First order=1/s, 2nd order=L/molsec.
- Tue Mar 05, 2019 8:07 pm
- Forum: First Order Reactions
- Topic: First Order Reactions Graph
- Replies: 3
- Views: 467
Re: First Order Reactions Graph
The graph of ln[A] vs. time is linear for first order reactions, but the graph of [A] vs time is exponential decay, because e is applied to undo the ln. That is the difference between the two graphs but both of them are for first order reactions, the only difference is the two variables.
- Tue Mar 05, 2019 8:05 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Rate Constant
- Replies: 3
- Views: 400
Re: Rate Constant
The rate constant is basically the derivative of the concentration, or d[R]/dt=k. Note that the rate constant is found experimentally and is temperature and reaction specific.
- Wed Feb 27, 2019 3:45 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Adding Pt to Cell Diagrams [ENDORSED]
- Replies: 1
- Views: 261
Adding Pt to Cell Diagrams [ENDORSED]
In some book examples Pt is included in the cell diagram. How do you know when to include it and when not to, and also which side it appears on? What specific wording in a question would suggest that?
- Wed Feb 27, 2019 3:42 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Order in Cell Diagrams
- Replies: 1
- Views: 209
Re: Order in Cell Diagrams
In Karen's worksheet session on Sunday she clarified this a little. Solid metals are always written towards the outer and oxidation forms are written closest to the middle. Therefore, the product of the oxidation half reaction would be to the right of the initial form.
- Wed Feb 27, 2019 3:40 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: n
- Replies: 8
- Views: 854
Re: n
n is the number of electrons involved in the equation. For example, if given a balanced redox reaction, you would have to reseperate the half reactions to find the number of electrons that are being cancelled out.
- Wed Feb 20, 2019 4:41 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Salt Bridge
- Replies: 5
- Views: 565
Re: Salt Bridge
The e- transfer from one reaction to another will stop due to charge build up and the reaction will stop. The salt bridge serves to maintain neutrality. Adding a salt bridge or porous disk allows the ion transfer to stay neutral.
- Wed Feb 20, 2019 4:40 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: positive E value?
- Replies: 1
- Views: 269
Re: positive E value?
Lavelle did not completely explain this but I'm guessing it has to do with the relative stability of different oxidation states. For example, in the class example the equation required Zn==>Zn+2 + 2e-, but the value was only given positive in the reverse. This shows that the state Zn+2 is probably m...
- Wed Feb 20, 2019 4:38 pm
- Forum: Balancing Redox Reactions
- Topic: Separating the equation
- Replies: 5
- Views: 513
Re: Separating the equation
Basically you're going to want to identify which element is reduced and which is oxidized and then write out separate equations. Therefore, you would write one equation for the reduction and another equation for the oxidation. By balancing both with the electrons cancelling out, you therefore have a...
- Wed Feb 13, 2019 11:24 am
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: delta S
- Replies: 7
- Views: 775
Re: delta S
For a system at equillibrium, the total delta s equals zero. For n irreversible expansion, given that there is no effect on the surroundings, delta s system equals delta s total.
- Wed Feb 13, 2019 11:23 am
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Internal Energy and Enthalpy
- Replies: 3
- Views: 405
Re: Internal Energy and Enthalpy
Delta U equals delta H + w when pressure is constant. At constant pressure q=delta H. Another helpful equation in this scenario is delta u=delta h-delta n RT. This can be used when you have gas values other thank P and V.
- Wed Feb 13, 2019 11:21 am
- Forum: Calculating Work of Expansion
- Topic: Work of the system
- Replies: 3
- Views: 434
Re: Work of the system
You can assume the work of the system is zero when there is no change in volume, given that w=-pdeltav. Therefore w would equal zero since deltav equals zero.
- Sun Feb 10, 2019 3:35 pm
- Forum: Calculating Work of Expansion
- Topic: Worksheet Week 4
- Replies: 1
- Views: 236
Worksheet Week 4
Could someone please explain number 6 on worksheet week 4? Thanks
- Tue Feb 05, 2019 9:15 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: Degeneracy Example
- Replies: 1
- Views: 236
Re: Degeneracy Example
in our lecture he did not do this example, but he gave the example ch4 and ch3cl (similar). for ch4 the degeneracy is only 2^1 if there are two possible partitions NOT 2^5. i think this is because ch4 is acting as a single unit. so in the example ch3cl, the degeneracy is 2^2 for two partitions. if a...
- Tue Feb 05, 2019 9:12 pm
- Forum: Calculating Work of Expansion
- Topic: Pressure Units
- Replies: 7
- Views: 783
Re: Pressure Units
i feel like as a general, the only one important to know is torr since that appears most frequently and some constants on the equations sheet are given also in torr. 760 torr=1atm.
- Tue Feb 05, 2019 9:11 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Delta H and q
- Replies: 3
- Views: 524
Re: Delta H and q
pressure and volume are inversely related. so at a constant volume, pressure is also constant. think about if you increase the pressure of a bike tire, the tire is also expanding and therefore there is a change in v, delta v. if delta v=0 then w=-pdeltav equals zero because the change in volume is z...
- Tue Feb 05, 2019 9:09 pm
- Forum: Calculating Work of Expansion
- Topic: work done by system or on system
- Replies: 3
- Views: 489
Re: work done by system or on system
if q for the system is positive, then it absorbs heat. if q is negative, it releases heat and heat is therefore lost to the surroundings. if w is positive for the system, work is done on the system by the surroundings. if w is negative, work is done by the system on the surroundings. hope this helps!
- Tue Feb 05, 2019 9:06 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Practice Midterm
- Replies: 3
- Views: 420
Re: Practice Midterm
I am assuming Lyndon will make an announcement sometime this week cause typically the practice midterms are lined up with a certain review session, so must be sometime this week :)
- Wed Jan 30, 2019 3:32 pm
- Forum: Phase Changes & Related Calculations
- Topic: Water phase change graph
- Replies: 6
- Views: 1489
Re: Water phase change graph
The slanted lines show and include all temperatures where only one state exists (ex. solid, liquid, gas). While the straight lines show melting/vaporization. Therefore, at that temperature, both phases that it is in between are present. Think about when ice is melting. It does not immediately go fro...
- Wed Jan 30, 2019 3:29 pm
- Forum: Phase Changes & Related Calculations
- Topic: Work
- Replies: 5
- Views: 555
Re: Work
Lavelle gave a great example in class. If you are pumping a tire, you are putting work into the system (given that the tire/pump is the system). Therefore the work for the surroundings is negative because you are losing energy. But the work for the system is positive because it is having the work do...
- Wed Jan 30, 2019 3:27 pm
- Forum: Phase Changes & Related Calculations
- Topic: J vs. kJ
- Replies: 9
- Views: 1103
Re: J vs. kJ
Work=-pressure*change in volume. The units for that are kgm-1s-1m3. The meters cancel out through exponent rules to create the unit kgm2s-2. This equals a joule. Therefore, your answer should be in joules, unless all other units in the equation are multiplied by 1000. But you could convert the final...
- Wed Jan 23, 2019 9:48 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Inert Gas
- Replies: 2
- Views: 188
Inert Gas
I know that adding an inert gas to a chemical reaction at equilibrium does not cause a shift, but which gases are inert? Is there a row/period on the periodic table?
- Tue Jan 22, 2019 7:11 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Quiz #1 This friday
- Replies: 5
- Views: 699
Re: Quiz #1 This friday
I was in Lavelle's class last quarter for 14A. Yes, the tests are during discussion section. The format is open ended questions with a possible mix of a few multiple choice questions thrown in there. It's usually around 8-10 questions that have multiple parts. For 14A at least, the tests were worth ...
- Tue Jan 22, 2019 7:09 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Stability
- Replies: 1
- Views: 147
Re: Stability
I'm unsure about comparing reactions as a whole. But in terms of reactants and products, if the equilibrium constant k<0 then that suggests that the reactants are more stable than the products. If the equilibrium constant k>0, then the products are more stable than the reactants.
- Tue Jan 22, 2019 7:06 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Making more product
- Replies: 3
- Views: 333
Re: Making more product
You are correct that the speed of the reaction does not effect the amount of product produced. Making more product includes LeChatlier's principle which essentially says that the reaction will adjust to a change in order to reach equilibrium again. This includes pressure/volume, temperature, and con...
- Mon Jan 21, 2019 3:52 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Percentage Protonation
- Replies: 2
- Views: 179
Percentage Protonation
If you are given the percentage protonation, is that the change value or equilibrium value when making an ICE table? (Given that you multiply the initial concentration by the percentage).
- Wed Jan 16, 2019 4:01 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Temperature and Equilibrium
- Replies: 3
- Views: 370
Re: Temperature and Equilibrium
If a reaction is endothermic, then it requires heat to complete the reaction, because the products have higher energy than the reactants. Therefore, if temperature is raised (more heat inputted) then equilibrium will favor the products. On the opposite, if a reaction is exothermic, meaning that the ...
- Wed Jan 16, 2019 3:57 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Taking x away in a Ka calculation
- Replies: 5
- Views: 442
Re: Taking x away in a Ka calculation
If you are calculating ka from given concentrations, so the ka is unknown, you employ the 5% rule. You would first calculate the percent ionization by dividing the equilibrium concentration by the initial concentration of one of the products times 100 in order to determine the change in x. If this a...
- Wed Jan 16, 2019 3:51 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Conjugates
- Replies: 5
- Views: 490
Re: Conjugates
The conjugate seesaw is based upon the statements "the stronger the acid the weaker its conjugate base" and "the stronger the base the weaker its conjugate acid" and inversely. Quantitatively, this can be explained by the equation ka x kb= kw, and kw is a constant (10^-14). There...
- Wed Jan 09, 2019 4:00 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: hw questions - points
- Replies: 9
- Views: 737
Re: hw questions - points
No. You earn three points per week for chemistry community posts (1 point per posts for up to 3 points a week) and then 7 points a week for homework problems (1 point per problem).
- Wed Jan 09, 2019 3:58 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: "lie to the right" vs "shifted to the right"
- Replies: 6
- Views: 1414
Re: "lie to the right" vs "shifted to the right"
Lying or sitting to the right basically means that at equilibrium, there are more products than reactants based upon the equilibrium constant k being greater than 10^3. Shifted to the right implies a change to the reaction or conditions, shifting the reaction away from equilibrium and producing more...
- Wed Jan 09, 2019 3:56 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Initial Concentration
- Replies: 3
- Views: 301
Re: Initial Concentration
I think you can always assume the initial concentration of a product is zero because the reaction has not occurred yet at the beginning and reactants are what are being formed. As for products, it is unlikely that the initial concentration is zero because then there is no reaction occurring because ...
- Tue Jan 08, 2019 5:02 pm
- Forum: Ideal Gases
- Topic: R in PV=nRT
- Replies: 34
- Views: 7069
Re: R in PV=nRT
R is a constant in the ideal gas law (PV=nRT) and has multiple unit derrivations that can all be found on the equations and constants sheet! So no need to memorize the value or units!
- Tue Jan 08, 2019 5:00 pm
- Forum: Ideal Gases
- Topic: Memorization
- Replies: 12
- Views: 1299
Re: Memorization
Also in regards to your second question, I had Lavelle for 14A and we did have to memorize the chemical formulas of some complex biological molecules. But overall, I would say it's necessary to memorize common polyatomic molecules as well as any specific example he goes over in class. For example, c...
- Tue Jan 08, 2019 4:57 pm
- Forum: Ideal Gases
- Topic: Memorization
- Replies: 12
- Views: 1299
Re: Memorization
No-PV=nRT is listen on the Equations and Constants sheet on Lavelle's website as well as the values for constant R with multiple unit derrivations!
- Mon Dec 03, 2018 9:06 pm
- Forum: Bronsted Acids & Bases
- Topic: Water with Acids and Bases
- Replies: 3
- Views: 396
Re: Water with Acids and Bases
Water is amphoteric so it can act as either an acid or base, therefore it depends on the other compound involved in the reaction with water to determine water's behavior.
- Mon Dec 03, 2018 9:05 pm
- Forum: Bronsted Acids & Bases
- Topic: Strong Acids
- Replies: 4
- Views: 346
Re: Strong Acids
Strong acids produce more protons of H+'s because they are almost completely ionized in solution. HBr, HCl, and HI are some examples of strong acids. Also, in today's lecture, Lavelle talked about how longer bonds associated with larger molecules become increasingly strong acids because the bonds ar...
- Mon Dec 03, 2018 9:00 pm
- Forum: Amphoteric Compounds
- Topic: Definition
- Replies: 5
- Views: 484
Re: Definition
Based on Lavelle's class notes "Between metal oxides (Bases) and Nonmetal Oxides (Acids) there is a diagonal bond of amphoteric oxides closely matching the diagonal bond of metalloids." Examples include BeO, Al2O3, Ga2O3, SnO2, Sb2O5, and PbO2.
- Mon Dec 03, 2018 11:23 am
- Forum: Administrative Questions and Class Announcements
- Topic: Final Grades
- Replies: 10
- Views: 1086
Re: Final Grades
Its based off of a point system overall, but there is a note on the syllabus that says a 50% is a C- (which would typically be a 70%), so I think the class is curved overall to the letter grade at the end. I'm assuming it can only help and not hurt you because its not a competetive scaling or anythi...
- Mon Nov 26, 2018 8:07 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Can an octahedral be polar?
- Replies: 4
- Views: 2236
Re: Can an octahedral be polar?
No. The octahedral shape is always nonpolar, because the shape is symmetrical. When a molecule has a symmetrical shape, the dipoles cancel out and the molecule in nonpolar.
- Mon Nov 26, 2018 7:57 pm
- Forum: Hybridization
- Topic: The Number Before Hybridization
- Replies: 3
- Views: 266
Re: The Number Before Hybridization
Yes. It would probably be most helpful conceptually too to write out the electron configuration and figure out which orbital and n number the valence electrons exist in. From there you can draw the Aufbau diagram like we did in class for the examples. I am also confused though if its necessary to in...
- Mon Nov 26, 2018 7:54 pm
- Forum: Hybridization
- Topic: Just Kind of Confused
- Replies: 13
- Views: 1054
Re: Just Kind of Confused
Lavelle went over this in class and said that he personally will accept either way. As long as the total number of orbitals matches the number of electron densities in the right order you should be good!
- Mon Nov 19, 2018 8:34 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Molecular Shape Patterns
- Replies: 5
- Views: 600
Re: Molecular Shape Patterns
I think we basically just need to memorize all of them, though some of the angles could probably be determined by visualizing. There are a lot of shapes, but what helped me was to make an organized table of the formulas using the VSEPR notation of A, X, and E and then the shape, bond angle(s), and h...
- Mon Nov 19, 2018 8:28 am
- Forum: Sigma & Pi Bonds
- Topic: Sigma and Pi Bonds affect on structure
- Replies: 4
- Views: 460
Re: Sigma and Pi Bonds affect on structure
Sigma and Pi bonds do not affect the shape or structure because in VSEPR, all bonds are treated as equivalent. Single, double, and triple bonds are all considered one region of electron density. Though Sigma and Pi bonds impact the movement and rotation of molecules. Molecules with only sigma bonds ...
- Mon Nov 19, 2018 8:25 am
- Forum: Sigma & Pi Bonds
- Topic: Calculating Amount of Sigma/Pi Bonds
- Replies: 4
- Views: 506
Re: Calculating Amount of Sigma/Pi Bonds
Yes, you would need to draw the Lewis Structure and count from there. A single bond has one sigma bond. A double bond has one sigma and one pi. And a triple bond has one sigma and two pi!
- Mon Nov 12, 2018 11:47 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: VSEPR
- Replies: 3
- Views: 369
Re: VSEPR
Just to clarify, all three atom molecules are not bent. For example, BeCl2 has a linear shape with a bond angle of 180 degrees. The difference is in the lone pair of electrons. BeCl2 has no lone pairs around the central atom, where as something like H20 is not linear because of the exertion of force...
- Mon Nov 12, 2018 11:44 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: Hydrogen Bonds
- Replies: 14
- Views: 1058
Re: Hydrogen Bonds
A hydrogen bond occurs only between a hydrogen atom and nitrogen, oxygen, or fluorine. A hydrogen bond in this sense is a covalent bond between a hydrogen atom and a highly electronegative atom with an available lone pair of electrons.
- Mon Nov 12, 2018 11:39 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: Greater polarizability of larger molecules
- Replies: 6
- Views: 1173
Re: Greater polarizability of larger molecules
Basically, the more electrons there are, the more likely or easily they are distorted. If you think about it in the diagram of circles as different n levels around the nucleus, the electrons are getting further and further away and filling more n orbitals. Therefore, the further electrons experience...
- Mon Nov 05, 2018 10:53 am
- Forum: Administrative Questions and Class Announcements
- Topic: DOWNLOAD SESSION WORKSHEETS HERE - Sundays 4-6pm (Karen) [ENDORSED]
- Replies: 135
- Views: 39513
Re: DOWNLOAD SESSION WORKSHEETS HERE - Sundays 4-6pm (Karen) [ENDORSED]
Thank you Karen! This is super helpful for preparing for the midterm today!
- Mon Nov 05, 2018 8:23 am
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: 3d and 4s
- Replies: 4
- Views: 607
Re: 3d and 4s
Commenting on the other replies, remember that 4s is only higher in energy when the 3d orbital has electrons in it. If the 3d orbital is empty, then 4s has lower energy level. Also remember the exceptions Cr [Ar] 3d5 4s1 and Cu [Ar] 3d10 4s1!
- Mon Nov 05, 2018 8:20 am
- Forum: *Shrodinger Equation
- Topic: Midterm
- Replies: 3
- Views: 634
Re: Midterm
I don't think we would need to know how to calculate this equation. In the lecture notes, Lavelle basically went over that Schrodinger's equation is used to predict where an electron is, or the probability of finding an e- at some point in space.
- Mon Nov 05, 2018 8:18 am
- Forum: Octet Exceptions
- Topic: Incomplete Octet
- Replies: 5
- Views: 1356
Re: Incomplete Octet
The four exceptions are hydrogen, lithium, beryllium, and boron. These are the first 5 elements on the periodic table, so you they have only 5,4,3,2, or 1 electrons to start with. Therefore they cannot form more bonds than valence electrons.
- Sun Nov 04, 2018 5:17 pm
- Forum: Resonance Structures
- Topic: Tricks for Resonance Structures
- Replies: 5
- Views: 912
Re: Tricks for Resonance Structures
Just try to draw as many as possible. Usually it's symettric or the question tells you how many resonance structures to consider. We won't be calculating the actual mixed bond lengths or anything because that's exclusively found experimentally.
- Sun Nov 04, 2018 5:16 pm
- Forum: Resonance Structures
- Topic: Resonance structures
- Replies: 7
- Views: 898
Re: Resonance structures
A resonance structure is basically when bonds and electrons can be organized in a variety of combinations. Remember that the actual occurring structure is a mix or blend of the multiple resonance structures, rather than one. But using formal charge, the lowest energy resonance structure factors more...
- Sun Nov 04, 2018 5:13 pm
- Forum: Lewis Structures
- Topic: ground state configuration set up
- Replies: 3
- Views: 293
Re: ground state configuration set up
Also make sure to remember the exceptions: Cr=[Ar]3d54s1 and Cu=[Ar]3d104s1 !!
- Sun Nov 04, 2018 5:12 pm
- Forum: Lewis Structures
- Topic: Lewis Structure for Ionic Bonds
- Replies: 2
- Views: 560
Re: Lewis Structure for Ionic Bonds
I think for ionic bonds or polyatomic ions (basically something with a charge), you use the box method to notate that each individual compound has a charge. Such as KNH4 then [K+][the lewis diagram for NH4+], bad example but hopefully that helps.
- Sun Nov 04, 2018 5:09 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Class Grading
- Replies: 9
- Views: 1168
Re: Class Grading
No, this class is not graded on a curve. On the syllabus it lists and overall point system. Basically, I think the homework points and chemistry community points act as a kind of curve like or buffer to your grade. Honestly, the curve would probably hurt more than help.
- Sun Nov 04, 2018 5:08 pm
- Forum: Administrative Questions and Class Announcements
- Topic: How to find my posts
- Replies: 163
- Views: 174300
Re: How to find my posts
If you go to the words "Quick links" in the upper left corner, the drop down will provide you with the option "Your posts" and they are all organized there.
- Sun Nov 04, 2018 5:07 pm
- Forum: Empirical & Molecular Formulas
- Topic: Naming Compounds on Test?
- Replies: 5
- Views: 517
Re: Naming Compounds on Test?
The UA talked about this a little in one of the review sessions. Basically he said you should know basic naming in addition to polyatomic ions or common compounds. In many practice questions in the textbook or midterm reviews though they often give you the name and then the formula after so don't st...
- Sun Nov 04, 2018 5:05 pm
- Forum: Empirical & Molecular Formulas
- Topic: garlic bread midterm practice #2
- Replies: 5
- Views: 623
Re: garlic bread midterm practice #2
You cannot round down. If you're going from that approach of multiplying the mass ratio of say carbon in co2 and dividing moles, then you'll need to multiply (basically guess and check) what integer will produce a next to close number. 0.15 is a little too high to round down since we are producing w...
- Sun Nov 04, 2018 5:03 pm
- Forum: Photoelectric Effect
- Topic: Conditions that allow electron to be ejected from metal surface
- Replies: 12
- Views: 2246
Re: Conditions that allow electron to be ejected from metal surface
Basically. If the energy of the photon/light has greater energy than the threshold energy, then energy will be conserved and appear in the form of ejected electron's kinetic energy. If the energy of photon is equal to the threshold energy, it is a break even, and the kinetic energy of ejected electr...
- Sun Nov 04, 2018 5:01 pm
- Forum: Photoelectric Effect
- Topic: Question on kinetic energy
- Replies: 5
- Views: 742
Re: Question on kinetic energy
No. 1/2mv^2 can only be used for particles that have mass and velocity (essentially particles in motion). This cannot be applied to photons because they have no rest mass. Therefore, the equation hc/E is used instead of h/p.
- Sun Nov 04, 2018 5:00 pm
- Forum: Photoelectric Effect
- Topic: intensity
- Replies: 4
- Views: 377
Re: intensity
Intensity relates to the quantity of photons. Basically, if the intensity decreases then there are less photons in the stream of light. Since photons are essentially packets of energy, this means that there is less energy going in-leading to either insufficient amount to eject electrons or less elec...
- Sun Nov 04, 2018 4:57 pm
- Forum: Photoelectric Effect
- Topic: Calculating Wavelength of electron
- Replies: 3
- Views: 1267
Re: Calculating Wavelength of electron
The equation you would use is Energy (photon) - Work Function=Kinetic Energy of Electron=1/2mv^2. And then use the known value of mass of electron to solve for velocity to plug into heisenberg's.
- Mon Oct 29, 2018 3:38 pm
- Forum: Resonance Structures
- Topic: Bond lengths
- Replies: 6
- Views: 436
Re: Bond lengths
I believe that bond lengths can only be found experimentally, so it's unlikely that we will be needing them in this class. I felt that Lavelle was using the experimental data of bond lengths to depict to us the general pattern that in terms of length: triple bonds<double bonds<single bonds. Also to ...
- Mon Oct 22, 2018 9:13 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: Electron Spin
- Replies: 3
- Views: 429
Re: Electron Spin
I was really confused on the Ms number number when I learned it in high school but I feel like Lavelle explained it really well. If you draw out the orbitals it makes a lot more sense. For example if n=2 and l=1 then you know this is the 2p orbital. p has three ml levels or three subshells (room for...
- Mon Oct 15, 2018 4:12 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Heisenberg Indeterminacy Equation
- Replies: 4
- Views: 407
Re: Heisenberg Indeterminacy Equation
I found the way that Professor Lavelle explained this concept in lecture today very helpful. Basically, if you passed something with large mass such as a baseball or human being through a stream of light, the distance and time could be accurately computed by multiple light beams because the track of...
- Fri Oct 12, 2018 4:13 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: En= -hR/n^2
- Replies: 3
- Views: 218
Re: En= -hR/n^2
Yes, there are other equations for elements that contain more than one electron. But, this equation is not necessarily only for hydrogen, but for single electron atoms.
For example: Li2+, He+, Be3+, etc. also have one electron using the periodic table and their "z" value.
For example: Li2+, He+, Be3+, etc. also have one electron using the periodic table and their "z" value.
- Fri Oct 12, 2018 4:09 pm
- Forum: Significant Figures
- Topic: Rounding Using Significant Figures
- Replies: 10
- Views: 1550
Re: Rounding Using Significant Figures
Generally, for multiplication and division problems, you adhere to the least number of significant figures stated in the given numbers for the problem. For addition and subtraction, you go to the least number of decimal places given in the problem. But for rounding I am also a bit confused. I would ...