Search found 101 matches
- Fri Mar 12, 2021 4:05 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Textbook Problem 7.11 b
- Replies: 2
- Views: 330
Re: Textbook Problem 7.11 b
For this one you will need to figure out which step is the rate determining one. That is the slowest step. The experimental rate law should clue you in on this. It implies that it has to be a step where H2 is reacting with another molecule. However step 2 has this but has n2o2 instead. This is where...
- Fri Mar 12, 2021 4:00 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Pre-Exponential Factor
- Replies: 3
- Views: 418
Re: Pre-Exponential Factor
Temperature can actually change A, This can be seen by re organizing the Arrhenius equation. This website has an excellent explanation of how https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Kinetics/06...
- Mon Mar 08, 2021 1:48 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Alternative solution to 6L.7 part b?
- Replies: 1
- Views: 159
Alternative solution to 6L.7 part b?
I solved the cell using two half reactions that the answer key did not use. I ended up with the correct cell potential and the correct overall equation, yet the answer key uses different half reactions and hence they reach a different cell diagram. Is my cell diagram correct as an alternative proces...
- Mon Mar 08, 2021 1:37 am
- Forum: Balancing Redox Reactions
- Topic: Redox Tips
- Replies: 5
- Views: 415
Re: Redox Tips
I think it really helps to follow the procedure to a T. The procedure is outlined in the textbook on page 538.
- Mon Mar 08, 2021 1:33 am
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: 6L.9
- Replies: 3
- Views: 373
Re: 6L.9
Oxidation number rules can help with this. You know that halogens will be -1, and that alkali will be +1. This means those substances are highly unlikely to change.
- Mon Mar 08, 2021 1:32 am
- Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
- Topic: Cathodic protection
- Replies: 2
- Views: 292
Re: Cathodic protection
Adding on to the reply above, the substance needs to be connected to the structure you are trying to protect. This connection needs to be conductive, and in essence the cathode is sacrificed to save the structure.
- Mon Mar 08, 2021 1:30 am
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Electrochemistry
- Replies: 9
- Views: 704
Re: Electrochemistry
Adding on to the reply above, you also need to know how to calculate cell potential from a list of standard reduction potentials.
- Sun Feb 28, 2021 11:11 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: avogadro's number in Boltzmann Equation
- Replies: 4
- Views: 474
Re: avogadro's number in Boltzmann Equation
Unfortunately, that means your calculator cannot compute such a large number. I do not think there is a way around that. Apparently calculators cannot handle numbers above 9.99999999 x 10^99.
- Sun Feb 28, 2021 11:10 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Nernst Equations
- Replies: 7
- Views: 434
Re: Nernst Equations
E naught is not equal to zero at equilibrium I believe. It is only when K is equal to 1 that the whole equation is equal to 0. Not all equilibria have a K value of 0 only very few do. Hope that helps in addition to the reply above.
- Sun Feb 28, 2021 11:07 pm
- Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
- Topic: RTGs
- Replies: 2
- Views: 372
RTGs
hello everyone,
here is an interesting application of the thermoelectric effect that I found (due to all the news about rovers)
https://rps.nasa.gov/power-and-thermal- ... r-systems/
I was wondering if anyone knows how to calculate the cell potential for one of these units?
here is an interesting application of the thermoelectric effect that I found (due to all the news about rovers)
https://rps.nasa.gov/power-and-thermal- ... r-systems/
I was wondering if anyone knows how to calculate the cell potential for one of these units?
- Sun Feb 28, 2021 11:05 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Conceptually understand why Enaught is not dependent on moles.
- Replies: 2
- Views: 206
Conceptually understand why Enaught is not dependent on moles.
Why is E naught not dependent on moles? Wouldn't the coefficients dictating how much electrons can move lead to some sort of a limiting reactant in the one that uses up more electrons per reduction?
- Sun Feb 28, 2021 11:03 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: cell potential (E) change affect overall
- Replies: 3
- Views: 237
Re: cell potential (E) change affect overall
E is negatively correlated with delta G. When E is negative delta D is positive which means that the situation is not spontaneous. When E is positive, delta G becomes negative making it spontaneous. This is seen from looking at deltaG= -nFEnaught
- Sun Feb 21, 2021 7:59 pm
- Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
- Topic: Ion Selective Electrode
- Replies: 6
- Views: 583
Re: Ion Selective Electrode
It is also known as a selective ion electrode, which basically tracks concentration of a specific ion. A common example of this is the glass electrode, which is used to track pH changes.
- Sun Feb 21, 2021 7:56 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Common logarithms in Nernst equation
- Replies: 3
- Views: 328
Re: Common logarithms in Nernst equation
We can use log or ln. We just have to use different coefficients. I believe that is what your question is asking?
- Sun Feb 21, 2021 7:53 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Topics
- Replies: 1
- Views: 173
Re: Topics
I believe that we are not going in exact order, so probably just read the textbook sections when we cover them in class? I am personally on 6M.
- Sun Feb 21, 2021 7:51 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Porous vs Salt
- Replies: 2
- Views: 223
Re: Porous vs Salt
Salt bridges and porous membranes serve the same purpose. However sometimes there are errors in either set up as seen in this paper https://scholar.harvard.edu/maralmousav ... rous-glass
- Sun Feb 21, 2021 7:47 pm
- Forum: Balancing Redox Reactions
- Topic: Manipulating Reduction Potentials
- Replies: 5
- Views: 419
Re: Manipulating Reduction Potentials
As the replies above seem to indicate. The thermodynamic properties are extensive properties, which means they depend on the amount of substance. Reduction potential is not extensive.
- Sun Feb 14, 2021 11:13 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Cv vs Cp
- Replies: 5
- Views: 373
Re: Cv vs Cp
David Y wrote:Cp is 5/2R while Cv is 3/2R
yeah I was wondering why there was a difference of R, how does that arise from having a fixed/changing volume?
- Sun Feb 14, 2021 11:12 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Equations for Thermodynamics and Thermochemisty
- Replies: 2
- Views: 171
Re: Equations for Thermodynamics and Thermochemisty
Another important equation is Delta S =nR ln(v2/v1)
- Sun Feb 14, 2021 11:09 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: avogadro's number in Boltzmann Equation
- Replies: 4
- Views: 474
Re: avogadro's number in Boltzmann Equation
You use avogadros number when you have a mole of a certain molecule. This would make degeneracy raised to the power of avogadros number to account for each of the positions on each molecule.
- Sun Feb 14, 2021 11:07 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: determining residual entropy - 4G.5
- Replies: 2
- Views: 198
Re: determining residual entropy - 4G.5
The first one has 4 *3 positions. This is because cis means the red atoms must stay next to the other. Hence in the middle section there are 4 slots for it, then 4 that would work from the top to the middle and 4 that work from the bottom to the middle. As for the second one there's only 6 atoms so ...
- Sun Feb 14, 2021 11:00 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Cv vs Cp
- Replies: 5
- Views: 373
Cv vs Cp
Could someone explain how the mathematical relationship between Cp and Cv was derived? I was looking at it in the textbook and got confused.
- Sun Feb 14, 2021 10:33 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Cp vs Cv
- Replies: 2
- Views: 213
Cp vs Cv
Why do we use Cv in the delta S=nC ln T2/T1 formula and not the Cp value?
- Sun Feb 07, 2021 8:30 pm
- Forum: Calculating Work of Expansion
- Topic: Work of Expansion
- Replies: 2
- Views: 156
Re: Work of Expansion
This is because a reversible reaction assumes a perfect system, with no energy lost other than work. This is the theoretical limit of a system.
- Sun Feb 07, 2021 8:27 pm
- Forum: Calculating Work of Expansion
- Topic: Work of Expansion
- Replies: 2
- Views: 148
Re: Work of Expansion
work of expansion, because the external gas around the piston is expanding, even if the gas inside the piston is compressing.
- Sun Feb 07, 2021 8:25 pm
- Forum: Calculating Work of Expansion
- Topic: Sapling #14: Why do we use two different values of R for Path A?
- Replies: 5
- Views: 216
Re: Sapling #14: Why do we use two different values of R for Path A?
The first equation has atm that you use the appropriate R for. The second R is only for Joules by Kelvin. The units dictate what R value you use.
- Sun Feb 07, 2021 8:24 pm
- Forum: Calculating Work of Expansion
- Topic: Help with Friday's Lecture
- Replies: 3
- Views: 143
Re: Help with Friday's Lecture
The system is doing work, which means that some amount of internal energy is being lost. But temperature isn't falling, this implies that some other energy is entering the system to keep it at thermal equilibrium. Hence, it is a heat sink.
- Sun Feb 07, 2021 8:20 pm
- Forum: Van't Hoff Equation
- Topic: Chemistry analysis
- Replies: 5
- Views: 512
Re: Chemistry analysis
I think we multiply by RT or R to figure out the H and delta S, or they might be asking us to analyze a graph.
- Sun Feb 07, 2021 8:13 pm
- Forum: Environment, Fossil Fuels, Alternative Fuels
- Topic: Gibbs and Environment
- Replies: 2
- Views: 710
Re: Gibbs and Environment
The above response is excellent. I just have an example to add. Check out Example 4d.4 to see what an alternative fuel problem looks like.
- Sun Jan 31, 2021 3:57 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Delta G and Delta H
- Replies: 3
- Views: 436
Re: Delta G and Delta H
You would have to find a scenario in which enthalpy is either very large and where entropy is very small (which the above replies have covered). This is because a large enthalpy value is not likely to be skewed too much by a change in entropy. So a large negative enthalpy would correlate to a large ...
- Sun Jan 31, 2021 3:55 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: Understanding Entropy
- Replies: 4
- Views: 444
Re: Understanding Entropy
Disorder has become synonymous with the "wrong/bad outcome". Entropy does not follow the value that media and society has assigned with that word. Instead entropy can just be thought of as randomness in a system.
- Sun Jan 31, 2021 3:52 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Absolute enthalpy
- Replies: 3
- Views: 489
Re: Absolute enthalpy
How are absolute enthalpy and absolute internal pressure different than enthalpy and internal pressure? Absolute enthalpy and internal pressure are the total amounts of those quantities. The values we use in our problems are a change in enthalpy and pressure. Those are observed by experiments where...
- Sun Jan 31, 2021 3:51 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Absolute enthalpy
- Replies: 3
- Views: 489
Re: Absolute enthalpy
Can absolute enthalpy and absolute internal energy be determined? I believe that absolute enthalpy of a system cannot be measured, however it is possible to estimate this using the change in enthalpy observed. As then the energy would be used to calculate how much energy would need to be taken out ...
- Sun Jan 31, 2021 3:48 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: energy within a system with pressure changes
- Replies: 2
- Views: 116
Re: energy within a system with pressure changes
One thing to add to the previous answer would be to consider friction. The friction between the piston and the wall could be another potential avenue for the energy to leave the system and enter the surroundings.
- Sun Jan 24, 2021 8:47 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Units for ΔH
- Replies: 3
- Views: 213
Re: Units for ΔH
Enthalpy change is usually calculated as kilojoules per mole, as when we are looking at an equation. However, if we want to know the q or the change in a system we would need to multiply it by moles to get the kilojoules that occurred in a specific reaction. So in summary, use kj/mol if we are doing...
- Sun Jan 24, 2021 8:44 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Internal energy
- Replies: 2
- Views: 96
Re: Internal energy
We do not need to know how to solve calorimetry problems for the midterm, but I believe we will learn them soon.
- Sun Jan 24, 2021 8:43 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Temperature and Equilibrium
- Replies: 3
- Views: 128
Re: Temperature and Equilibrium
We would need to be given the change in enthalpy or we would need to conduct the experiment in a calorimeter to track the change in the temperature. We do know that q= MCAT which can be used to calculate the change in heat energy.
- Sun Jan 24, 2021 8:41 pm
- Forum: Phase Changes & Related Calculations
- Topic: State Changes
- Replies: 4
- Views: 282
Re: State Changes
We will need to know the heat of fusion and vaporization, which I believe will be on the constants sheet. Additionally, I believe it is not like the photon, as it has a lot of different factors. Sometimes water can be chilled below the temperature as it will need a freezing nucleus to form ice. At t...
- Wed Jan 20, 2021 2:06 pm
- Forum: Phase Changes & Related Calculations
- Topic: Phase Change
- Replies: 5
- Views: 344
Phase Change
Is the state of a system a state property? During a phase change the system at a particular enthalpy can exist in either phase, which would mean that state of matter is not a state property as it depends on the pathway it took to get to the phase change temperature. Additionally isn't the enthalpy a...
- Sun Jan 17, 2021 9:22 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Temperature Change in Neutral Water
- Replies: 2
- Views: 132
Re: Temperature Change in Neutral Water
The reply above does an excellent job explaining it but I believe one more detail could help make it clearer. The reason why the neutral ph changed is because Kw has changed as temperature changes move the equilibrium constant.
- Sun Jan 17, 2021 9:10 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Kp to Kc conversion
- Replies: 5
- Views: 404
Re: Kp to Kc conversion
I believe if you understand how that equation is derived (from the ideal gas law) then you should be fine. We were supposed to learn the ideal gas law from the outlines, so I would assume that these kinds of questions are fair game for the midterms.
- Sun Jan 17, 2021 9:08 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: changing volume by adding more solid reactants.
- Replies: 3
- Views: 248
changing volume by adding more solid reactants.
Would we ever need to consider the volume a solid reactant or liquid reactant takes up in a reaction chamber? For instance if we added a large excess of a low density solid to a reaction vessel, wouldn't that change the volume and thereby pressure of the system for which we would need to apply le Ch...
- Sun Jan 17, 2021 9:06 pm
- Forum: *Alkanes
- Topic: Alkaline environment
- Replies: 6
- Views: 1388
Re: Alkaline environment
This is peculiar because our bodies are slightly alkaline. Luckily we have a nice system of buffers, which we will probably learn the Henderson hasselbach equation for, which keep our bodies at a ph of 7.4.
- Sun Jan 17, 2021 9:03 pm
- Forum: Ideal Gases
- Topic: Kp?
- Replies: 30
- Views: 1146
Re: Kp?
Yes, this is because ideal gasses assume that they do not interact with each other as their collisions are considered negligible. Hence, their partial pressures are calculated which is equal to their "concentration". Additionally, the units for Kp do not matter as they will cancel out if t...
- Sun Jan 17, 2021 8:59 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Kw usage
- Replies: 6
- Views: 401
Re: Kw usage
I believe for 6B.9 you do still use the kw of 10^-14.
- Sun Jan 10, 2021 11:45 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Heterogenous Equilibriums
- Replies: 4
- Views: 217
Re: Heterogenous Equilibriums
They would change but not by much, which is why we disregard them. The change is so small it doesn't affect the calculation we make.
- Sun Jan 10, 2021 11:43 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Textbook 5J #5 Part D?
- Replies: 6
- Views: 277
Re: Textbook 5J #5 Part D?
The pressure could increase from an inert gas, that would not affect the K value.
- Sun Jan 10, 2021 11:42 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Is there a correct step to solve for K?
- Replies: 3
- Views: 138
Re: Is there a correct step to solve for K?
Sometimes you cannot solve for the concentrations at the start so you have to do it at the end. This was what I found from problems on sapling. This is because we are only given initial concentrations not equilibrium ones, hence we could only solve for it at the end.
- Sun Jan 10, 2021 11:40 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Rice method correlation [ENDORSED]
- Replies: 4
- Views: 246
Re: Rice method correlation [ENDORSED]
RICE is the same thing as an ICE table, my high school used both names for it. I think just knowing how to solve the problems is important.
- Sun Jan 10, 2021 11:39 pm
- Forum: Ideal Gases
- Topic: Inert Gases
- Replies: 11
- Views: 364
Re: Inert Gases
An inert gas does not change the volume. K is always calculated in terms of quanitity per volume, hence increasing pressure with an inert gas does nothing to change it.
- Wed Dec 16, 2020 9:20 pm
- Forum: Properties of Light
- Topic: article about the speed of light
- Replies: 1
- Views: 1965
- Wed Dec 16, 2020 9:15 pm
- Forum: *Making Buffers & Calculating Buffer pH (Henderson-Hasselbalch Equation)
- Topic: Equation
- Replies: 2
- Views: 734
Re: Equation
We use the henderson hasselbalch equation: pH=pKa +log ([A-]/[HA])
- Wed Dec 16, 2020 9:08 pm
- Forum: Polyprotic Acids & Bases
- Topic: Calculating Ka
- Replies: 9
- Views: 1194
Re: Calculating Ka
We add in molarity (concentration). We haven't done kinetics yet but whenever we see the [] that indicates concentration.
- Wed Dec 16, 2020 9:06 pm
- Forum: Properties & Structures of Inorganic & Organic Bases
- Topic: oxides and hydroxides
- Replies: 7
- Views: 628
Re: oxides and hydroxides
The response above talks about group 1 and two. So I will talk about some transitional metals. These also can form hydroxides and oxides as seen in the textbook. This is because they can become a +3 or +4 ion and can bind to oxygen which is -2 or hydroxide which is -1
- Wed Dec 16, 2020 9:02 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Conceptual Textbook Question: Fundamentals J [ENDORSED]
- Replies: 2
- Views: 327
Re: Conceptual Textbook Question: Fundamentals J [ENDORSED]
I believe that this is referencing the fact that strong acid and bases in water would dissolve, hence would not be written in molecular form but as ions. Weak acids and bases are only dissolving at a low rate which is why their molecular formula is utilized.
- Sun Dec 06, 2020 10:11 pm
- Forum: Properties & Structures of Inorganic & Organic Bases
- Topic: What makes an acid more corrosive?
- Replies: 7
- Views: 1230
Re: What makes an acid more corrosive?
I believe the reason concentration doesn't matter is because when the concentration is very high there won't be enough water to be protonated and participate in the reaction, at a dilute concentration there will be enough water to do so. Also both bases and acids are corrosive, not just acids.
- Sun Dec 06, 2020 10:06 pm
- Forum: Naming
- Topic: Question about How Much We Need to Memorize
- Replies: 2
- Views: 198
Re: Question about How Much We Need to Memorize
I believe we should be memorizing the chart on page 724 at the very least. That has a lot of common ligand names.
- Sun Dec 06, 2020 10:02 pm
- Forum: Amphoteric Compounds
- Topic: Amphoteric Compound Acid/Base Character
- Replies: 4
- Views: 271
Re: Amphoteric Compound Acid/Base Character
Well as we know the strong acids, and none of those seem to be amphoteric, it appears that most amphoteric molecules that can act as acids would be weak ones. Same would apply to bases.
- Sun Dec 06, 2020 10:00 pm
- Forum: Air Pollution & Acid Rain
- Topic: Carbon dioxide
- Replies: 6
- Views: 752
Re: Carbon dioxide
As the above reply indicates, having more carbon dioxide leads to more carbonic acid which lowers the ph of solutions. Respiratory acidosis is when the lungs cannot expel enough CO2 that it leads to the blood and bodily fluids becoming acidic.
- Sun Dec 06, 2020 9:58 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Calculating pH or pOH for Strong & Weak Acids & Bases
- Replies: 2
- Views: 173
Re: Calculating pH or pOH for Strong & Weak Acids & Bases
A pH of 7 is neutral. 0-7 are considered acidic. 7-14 are considered basic. This is because it is the negative logarithm of the concentration of H+
- Sun Nov 29, 2020 6:42 pm
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: Last Bullet of Outline 4
- Replies: 3
- Views: 373
Re: Last Bullet of Outline 4
Please tell me everything you know for describing the structure of a molecule, cation, or anion in terms of hybrid orbitals and sigma and pi bonds! - To describe the structure of a molecule, cation, or anion, you will need to know the amount of lone pairs on the central atom and the amount of bonds...
- Sun Nov 29, 2020 6:38 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: H20 Shape
- Replies: 17
- Views: 1121
Re: H20 Shape
Lone pair repel each-other more greatly than two atoms, hence they increase the angle between themselves, which in turn pushes the two atoms closer together decreasing that angle. This results in the bent shape.
- Sun Nov 29, 2020 6:35 pm
- Forum: Hybridization
- Topic: Double Bond Type
- Replies: 4
- Views: 272
Re: Double Bond Type
This is because a pi bond is weaker than a sigma bond. The first bond that always forms is a sigma bond. Additionally pi bonds happen at 90 degrees to each other (think of the p shell orbitals) and that is physically impossible to happen and be bonded to the same atom.
- Sun Nov 29, 2020 6:34 pm
- Forum: Hybridization
- Topic: Sapling #18
- Replies: 10
- Views: 483
Re: Sapling #18
I believe this is figured out by looking at pi bonding. whenever you have an even number there are enough pi bonds to lock the carbon into a single plane. This is because the pi bond does not allow for rotation. Every pi bond is formed at a 90 degree Angle to the other, so even numbers would go back...
- Sun Nov 29, 2020 6:23 pm
- Forum: Hybridization
- Topic: Definition of Hybridization
- Replies: 5
- Views: 318
Re: Definition of Hybridization
Hybridization is the mixing of shells to form half full orbitals that can bond at an energy level between the original energy levels of the constituent shells. This is because of the Pauli exclusion principal that states you can only have 2 electrons in a shell. In response to your second question, ...
- Sun Nov 22, 2020 10:58 pm
- Forum: Sigma & Pi Bonds
- Topic: Sigma and Pi bonds relating to resonance
- Replies: 2
- Views: 190
Re: Sigma and Pi bonds relating to resonance
For the scope of this course (as far as I can tell from the textbook problems) we just draw out all the possible resonance structures then label the bonds for each structure. As for the real world, I think that the Pi bonds are the reason why resonance can exist. They are easily broken (relative to ...
- Sun Nov 22, 2020 10:52 pm
- Forum: Dipole Moments
- Topic: Determining higher dipole moments
- Replies: 5
- Views: 474
Re: Determining higher dipole moments
You can do this by looking at the ionic character of the bonds. So a c-F bond is more polar than a C-o bond. So the vectors for that molecule will have a stronger partial negative charge. Furthermore, if the vectors in a molecule cancel out, then it would be less polar than one where the vectors do ...
- Sun Nov 22, 2020 10:50 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Optimal Formal Charge Configuration
- Replies: 3
- Views: 287
Re: Optimal Formal Charge Configuration
I believe that is correct, you put it on the nitrogen. When you have the option that all else has the lowest formal charge and the only difference is where a negative formal charge goes, then you put that on the more electronegative atom. I believe this is similar to a sapling problem from last week...
- Sun Nov 22, 2020 10:48 pm
- Forum: Ionic & Covalent Bonds
- Topic: C-H bond polarity
- Replies: 10
- Views: 12054
Re: C-H bond polarity
Their electronegativity difference is about 0.4 which means it is non polar. Anything above 2.0 is considered ionic bonding. Since 0.4 is so small it is considered non polar as the ionic character of this bond is very low.
- Sun Nov 22, 2020 10:45 pm
- Forum: Sigma & Pi Bonds
- Topic: Pi Bonds with s Orbital
- Replies: 4
- Views: 221
Re: Pi Bonds with s Orbital
It is not possible for the S orbital to overlap in that manner. If you look at it geometrically, it is the same at all aspects, hence an overlap "sideways" is the same as the overlap from a sigma bond. This means that they can only create one bond.
- Sun Nov 15, 2020 11:27 pm
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Textbook 2D.9
- Replies: 4
- Views: 277
Re: Textbook 2D.9
The bigger the atom is the more polarizing power it has, because it has more protons pulling on the electrons. Hence, Be would be the smallest and lowest, then Rb, then Sr. This means polarizing power goes up across a period and increases as u go down a group.
- Sun Nov 15, 2020 11:18 pm
- Forum: Ionic & Covalent Bonds
- Topic: Saplong 15
- Replies: 6
- Views: 387
Re: Saplong 15
I believe the question is asking which one of the molecules has hydrogen bonding in water. (these are the atoms with H bound to F, O, or N) HF is the only molecule that meets this criteria
- Sun Nov 15, 2020 11:15 pm
- Forum: Lewis Structures
- Topic: expanded octets
- Replies: 2
- Views: 166
Re: expanded octets
The above reply explains how to do it, so I will help with when to do it. You can do it when the atom is in the 3p shell onwards as it can hybridize with the 3d shell and accept electrons there as it is technically also at the third energy level. You would do this when you need to put in more electr...
- Sun Nov 15, 2020 11:13 pm
- Forum: Ionic & Covalent Bonds
- Topic: Formation of Hydrogen bonds
- Replies: 2
- Views: 160
Formation of Hydrogen bonds
Can a hydrogen bond form with F 2 or not? Additionally if a Flourine atom was in a polar molecule would it be able to participate in hydrogen from another atom that has an oh or nh or fh group, despite the fluorine in the polar molecule not being bound to hydrogen (lets suppose its bound to carbon o...
- Sun Nov 15, 2020 11:10 pm
- Forum: Ionic & Covalent Bonds
- Topic: Hydrogen Bonds
- Replies: 2
- Views: 82
Hydrogen Bonds
I noticed during some of the homework on sapling the hydrogen bonds could be created twice on the same oxygen atom because it has two lone pairs. Are hydrogen bonds like coordinate covalent bonds, or does it have to do with the fact that each lone pair simply acts as a negative charge for positive d...
- Sun Nov 08, 2020 7:34 pm
- Forum: Electronegativity
- Topic: determining electronegativity
- Replies: 40
- Views: 6038
Re: determining electronegativity
This is outside of the scope of this class, but it was cool so I searched it up. There is a person named Linus Pauling who made a scale to measure electronegativity from 0.79-3.98 (1-4). He assigned Flourine to be 4, and then calculated the rest through experimental observation. This is known as the...
- Sun Nov 08, 2020 7:30 pm
- Forum: Ionic & Covalent Bonds
- Topic: London dispersion forces
- Replies: 12
- Views: 853
Re: London dispersion forces
I believe most replies above have the definition of London dispersion forces. Here is the order of bond strengths from strongest to weakest
1. Ionic bonds
2. Covalent bonds
3. Dipole Dipole bonds
4. Van der Waals (London dispersion)
1. Ionic bonds
2. Covalent bonds
3. Dipole Dipole bonds
4. Van der Waals (London dispersion)
- Sun Nov 08, 2020 7:27 pm
- Forum: Bond Lengths & Energies
- Topic: Delocalized Electrons
- Replies: 5
- Views: 362
Re: Delocalized Electrons
Delocalized electrons are free flowing between the nuclei. We just simplify it for our Lewis diagrams. If you have heard of metallic bonds, those are an excellent example of delocalized electrons, and the reason we have electricity!
- Sun Nov 08, 2020 7:22 pm
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Covalent Bonds with Ionic Character/Polar
- Replies: 3
- Views: 197
Re: Covalent Bonds with Ionic Character/Polar
Covalent happen between two nonmetals. Additionally, the atoms in ionic bonds with covalent characteristics have a higher electronegativity difference than atoms in polar covalent bonds.
- Sun Nov 08, 2020 7:19 pm
- Forum: Electronegativity
- Topic: Silver Halides
- Replies: 5
- Views: 253
Re: Silver Halides
I believe he specifically highlighted them because they are insoluble. Hence this physical phenomenon we can observe with our eyes shows the covalent characteristics. This is unexpected for an ionic compound.
- Sun Nov 01, 2020 4:53 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: 1E.7
- Replies: 6
- Views: 236
Re: 1E.7
The answer is c. This is because it deviates from the normal rules for filling orbitals, you can notice how one orbital at a lower energy level is half filled and instead the electron is in a higher energy level. The rest of the options follow hunds aufau and Pauli
- Sun Nov 01, 2020 4:46 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: Number of Electrons per Shell
- Replies: 5
- Views: 374
Re: Number of Electrons per Shell
You can calculate it by understanding the ml quantum number. this tells you how many orbitals are available, each orbital has 2 so it would be ml options *2. If we look at the shells we know so far: s has only 0 as ml so 1*2=2 p has -1,0,1 as ml so 3*2=6 d has -2,-1,0,1,2 so 5*2=10 f has -3,-2,-1,0,...
- Sun Nov 01, 2020 4:42 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: Sapling question 21
- Replies: 11
- Views: 629
Re: Sapling question 21
I looked at the periodic table. How many electrons are possible at the second energy level are all of the atoms in the second period. this would be Li-Ne. Or aka 2s^22p^6. This is 2+6=8
- Sun Nov 01, 2020 4:30 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Energy of s, p, d, f states
- Replies: 3
- Views: 239
Re: Energy of s, p, d, f states
This all depends on energy level, obviously the 5s electrons will have more energy (be further away from the nucleus) than a 4s electron. However when comparing orbitals at the same principle quantum number, the order will be s, p , d ,f. This has to do with the physical geometry determined by shrod...
- Sun Nov 01, 2020 4:27 pm
- Forum: Trends in The Periodic Table
- Topic: Metalloids/Non-Metals on the Periodic Table
- Replies: 6
- Views: 1810
Re: Metalloids/Non-Metals on the Periodic Table
The way I memorized them is by looking at the periodic table. I have memorized the shape of the "staircase" and can reproduce it from memory. This method is probably less efficient than a mnemonic but goes to show there are alternative ways of memorizing them
- Sun Oct 25, 2020 6:20 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Rydberg Equation and Negative Signs
- Replies: 11
- Views: 1890
Re: Rydberg Equation and Negative Signs
Tl;dr If the question asks about the energy of the electron it will be negative as it loses energy. If the question is asking how much energy is released or is in the photon released that is positive.
- Sun Oct 25, 2020 6:16 pm
- Forum: Photoelectric Effect
- Topic: Mass of atoms
- Replies: 18
- Views: 757
Re: Mass of atoms
On one of the textbook problems it assumed we knew how to convert from miles to meters. Is that something we need to memorize?
- Sun Oct 25, 2020 6:15 pm
- Forum: *Black Body Radiation
- Topic: Figure 1B.1 [ENDORSED]
- Replies: 1
- Views: 319
Figure 1B.1 [ENDORSED]
I was looking at the figure 1b.1 in the textbook which depicts black body radiation and energy per wavelength of light. How is it possible that objects at higher temperatures emit a higher amount of energy for a certain wavelength than a cooler object emitting photons at the same wavelength. Is this...
- Sun Oct 25, 2020 6:04 pm
- Forum: Photoelectric Effect
- Topic: Determining Metal Type
- Replies: 3
- Views: 573
Re: Determining Metal Type
Here is how I approached this problem. First I converted from wavelength to frequency using hv=c. v= 1.577x10^15 Then I converted to energy per photon using hv=E. E= 1.045x10^-18 J then I converted to ev. this gave me 6.53 eV. I subtracted kinetic energy to find the work for the metal. This is 2.53 ...
- Sun Oct 25, 2020 5:56 pm
- Forum: *Shrodinger Equation
- Topic: Shrodinger Equation Confusion
- Replies: 3
- Views: 284
Re: Shrodinger Equation Confusion
I believe what you are referring to is the Rydberg equation. V=R (1/n(final) - 1/n(initial)) will always give you a positive number. Think about it in terms of fractions, final will always be smaller than the initial. The larger a denominator, the smaller the fraction. Hence, 1/small - 1/large will ...
- Sun Oct 25, 2020 5:52 pm
- Forum: Properties of Light
- Topic: Balmer or Lyman Series
- Replies: 9
- Views: 356
Re: Balmer or Lyman Series
Balmer ends at n=2, Lymann at n=1, the Paschen series ends at n=3 and the Brackett series ends at n=4. These are the ones from the textbook.
- Sun Oct 18, 2020 9:38 pm
- Forum: *Black Body Radiation
- Topic: Black Body Radiation
- Replies: 13
- Views: 902
Re: Black Body Radiation
We don't need to know this but something interesting to know is that T is temperature, C is the same C we have been using, and lambda is wavelength. This is much more advanced that we would be learning for 14a.
- Sun Oct 18, 2020 2:23 pm
- Forum: Einstein Equation
- Topic: HW problem 5
- Replies: 6
- Views: 201
Re: HW problem 5
Yes, that is exactly correct. Conceptually, the equations we are solving are PER photon. So at the end we would just need to figure out how many of the energy per photon we would need to get the 32.74J. First you would want to find the frequency so do c=lambda v this would give you 3.08 x 10^11 hz T...
- Sun Oct 18, 2020 2:16 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Rydberg Equations vs Dr Lavelle's Empirical Equation
- Replies: 2
- Views: 119
Re: Rydberg Equations vs Dr Lavelle's Empirical Equation
I believe n1 is the final. This is because n1 being the final would mean its the lower energy state, and the n2 term would have the higher energy state. - Small- (-big) would create a positive energy, which tells you the amount of energy released. This is exactly the same as Dr.Lavelle explained. I ...
- Sun Oct 18, 2020 2:11 pm
- Forum: Einstein Equation
- Topic: E=hv vs E=pc?
- Replies: 8
- Views: 1778
Re: E=hv vs E=pc?
How would we calculate the momentum of a photon? Is it a similar calculation to that of an electron except we use the mass of a photon instead? What would be the units? thanks.
- Sun Oct 18, 2020 2:09 pm
- Forum: Properties of Light
- Topic: Speed of Light Equation
- Replies: 6
- Views: 314
Re: Speed of Light Equation
As most replies above have indicated, the speed of light is a constant and will be provided on exams. As for why that is? this is where it gets interesting. The speed of light is not given to us in a relative sense, as a car passing by us may appear to be 40 mph but only 0 mph for those inside of it...
- Sun Oct 11, 2020 6:01 pm
- Forum: Significant Figures
- Topic: Sapling #4
- Replies: 10
- Views: 650
Re: Sapling #4
As the reply above indicates, 3000 would not be considered an exact number unless you have a decimal. Hence, 3020 would have 3 significant figures, as it could be written as 3.02 x 10^4. The general rule is digits after the decimal place are considered significant, and trailing zeroes without a deci...
- Sun Oct 11, 2020 5:20 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Syllabus Problem 1A.9 The Quantum World
- Replies: 2
- Views: 170
Re: Syllabus Problem 1A.9 The Quantum World
This should be either given or located inside the textbook. All these activities are simply examples on the electromagnetic spectrum.
- Sun Oct 11, 2020 3:37 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Sapling Q 5
- Replies: 1
- Views: 85
Re: Sapling Q 5
I believe it goes from n-6 to n=1, so that would be 5 spectral lines. One for each transition it makes, as the energy we observe is released when the electron moves down energy levels.
- Wed Oct 07, 2020 7:15 pm
- Forum: Limiting Reactant Calculations
- Topic: Actual and Theoretical yields
- Replies: 14
- Views: 506
Re: Actual and Theoretical yields
This is an interesting question! Here are my thoughts : 1. As numerous others have mentioned in this thread, getting to a 100% actual yield will be very hard. This assumes every atom in the reactants reacts in the appropriate reaction that you are investigating. 2. You might get a false 100% yield a...