Search found 104 matches
- Mon Mar 16, 2020 4:05 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Voltaic Cells
- Replies: 3
- Views: 306
Voltaic Cells
Are voltaic cells the same as galvanic cells?
- Mon Mar 16, 2020 4:04 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Activation Energy
- Replies: 3
- Views: 347
Re: Activation Energy
If the reaction is endothermic, increasing the temperature lowers the activation energy because it adds energy to the system. For the endothermic reaction this makes it easier for the reactants to form products, this is the opposite for an exothermic reaction.
- Mon Mar 16, 2020 4:02 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: Initial vs Unique Rates
- Replies: 3
- Views: 278
Re: Initial vs Unique Rates
The initial rate is the rate when there are only reactants, and it is the rate that the reactants are used up in a reaction. The unique rate is the rate a molecule is used up divided by its stoichiometric coefficient, all molecules in a reaction will have the same unique rate.
- Mon Mar 16, 2020 3:58 pm
- Forum: Balancing Redox Reactions
- Topic: oxidation numbers
- Replies: 4
- Views: 471
Re: oxidation numbers
Count the oxygens and hydrogens in the molecule. The oxygens are -2 and the hydrogens are +1, the other element in the molecule will add to these elements to get the molecule to whatever charge it is.
- Mon Mar 16, 2020 3:57 pm
- Forum: Second Order Reactions
- Topic: 2nd order
- Replies: 6
- Views: 559
Re: 2nd order
If you look at the units and liters and seconds are in the denominator then it is second order.
- Mon Mar 16, 2020 1:40 am
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: Reverse rate Laws
- Replies: 3
- Views: 306
Re: Reverse rate Laws
If you are given the K for the forward reaction and the overall K then you can determine the K for the backwards reaction and thus determine the rate for the backwards reaction
- Mon Mar 16, 2020 1:38 am
- Forum: First Order Reactions
- Topic: order of a reaction
- Replies: 6
- Views: 442
Re: order of a reaction
Depending on what you are given you can tell. If you are just given the reaction, then you can tell what order it is by looking at how each reactant affects the rate. If you are given a certain unit for the k value, then you can also tell the order.
- Mon Mar 16, 2020 1:36 am
- Forum: Balancing Redox Reactions
- Topic: Ecell values
- Replies: 12
- Views: 789
Re: Ecell values
The higher Ecell value is usually reduced because the E cell values are the standard values of reduction. One that produces a higher value that is reduced is more likely to be reduced in a reaction.
- Mon Mar 16, 2020 1:35 am
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Concentration Cells
- Replies: 9
- Views: 671
Concentration Cells
Why is the standard cell potential of a concentration cell always equal to 0?
- Mon Mar 16, 2020 1:34 am
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: concentration
- Replies: 3
- Views: 318
Re: concentration
Because the only thing that is making the cell have a potential is the difference in concentration between the cathode and the anode, so changing the concentration of one or both will affect the cell potential.
- Tue Mar 10, 2020 12:40 am
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Work and Delta G
- Replies: 4
- Views: 211
Work and Delta G
I believe Dr. Lavelle mentioned in lecture that W = -nfe and G = -nfe. Is this true for all reactions? Or is it only for standard conditions?
- Tue Mar 10, 2020 12:37 am
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Downs Process
- Replies: 4
- Views: 387
Re: Downs Process
No the Downs Process was never really gone over in lecture and isn't covered in the homework so it likely won't be on the final exam.
- Tue Mar 10, 2020 12:32 am
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: Reactant for Initial Rate
- Replies: 2
- Views: 172
Re: Reactant for Initial Rate
We only use reactant rate for initial rate because we assume there are only reactants and no products when just starting the reaction, this is why it is known as initial rate. This is used for all reactions
- Tue Mar 10, 2020 12:11 am
- Forum: Second Order Reactions
- Topic: Derivations of Reactions
- Replies: 5
- Views: 447
Re: Derivations of Reactions
I'm pretty sure we just need to know the final equations associated with each of the derived equations. A lot of the time equations are derived for us in class so we can understand them better but we don't need to fully apply all the derivations
- Tue Mar 10, 2020 12:03 am
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Study Advice
- Replies: 73
- Views: 6764
Re: Study Advice
I like doing all the homework problems in the textbook because Lavelle loves putting problems like those on the test. I also like to review past midterms and exams.
- Thu Mar 05, 2020 11:02 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: different units
- Replies: 4
- Views: 363
Re: different units
Each different ordered reactions involve having the concentrations be increased to certain powers. ^2 for second order. Therefore the units are changed by that order as well.
- Thu Mar 05, 2020 11:00 pm
- Forum: General Rate Laws
- Topic: Rate Law Slopes
- Replies: 3
- Views: 289
Rate Law Slopes
In lecture it seemed like professor said that k is always the slope of the graph of the rate. Is this true for zero order, first order, and second order reactions. Or is it only true for zero order?
- Wed Mar 04, 2020 12:20 pm
- Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
- Topic: electrolysis calculations
- Replies: 2
- Views: 218
Re: electrolysis calculations
I'm pretty sure that at least for test 2 we will not have to do any calculations involving electrolysis.
- Wed Mar 04, 2020 12:19 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: equation for Q
- Replies: 3
- Views: 239
Re: equation for Q
Yes for Q the anode is always over the cathode. It is very confusing because you would think it would be cathode over anode but in the case of the nernst equation it is the opposite
- Wed Mar 04, 2020 12:17 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Figuring out n
- Replies: 15
- Views: 927
Figuring out n
When using the equation G= -nFe how do we determine what n is?
- Mon Feb 24, 2020 12:34 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Galvanic vs. electrolytic
- Replies: 4
- Views: 307
Re: Galvanic vs. electrolytic
An electrolytic cell converts electrical energy into chemical energy, a galvanic cell converts chemical energy to electrical energy.
- Mon Feb 24, 2020 12:33 am
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: G in standard conditions
- Replies: 2
- Views: 204
Re: G in standard conditions
You can also calculate G in standard states using the Gfinal-Ginitial, and you can do the same with G in non standard states, since G is a state function
- Mon Feb 24, 2020 12:30 am
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Estimating Delta G
- Replies: 2
- Views: 233
Re: Estimating Delta G
I'm pretty sure since you are subtracting electric potential, a negative electric potential means that delta G is positive. So whatever the sign of the electric potential, delta G will always be the opposite
- Mon Feb 24, 2020 12:26 am
- Forum: Balancing Redox Reactions
- Topic: half reaction
- Replies: 10
- Views: 644
Re: half reaction
You include water in the half reaction when you need to balance O2 in the reaction. Then if there are left over H+ ions you include water in the reaction as well as OH- ions
- Mon Feb 24, 2020 12:25 am
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Test 2
- Replies: 6
- Views: 372
Re: Test 2
Yeah it is everything we've learned after the midterm until the end of electrochemistry I think
- Wed Feb 19, 2020 1:35 pm
- Forum: Van't Hoff Equation
- Topic: Van't Hoff Equation
- Replies: 3
- Views: 243
Van't Hoff Equation
I'm not sure when we apply this equation. Can someone explain to me what types of problems we use this equation for?
- Wed Feb 19, 2020 1:28 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Sign of delta G
- Replies: 9
- Views: 569
Sign of delta G
Instead of using the sign of delta G to determine which way a reaction can proceed. Could we also just figure out if Q is less then or more then K and decide that way?
- Wed Feb 19, 2020 1:25 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Midterm Curve
- Replies: 45
- Views: 2130
Re: Midterm Curve
He curves the class based on the total overall scores. Don't expect your midterm score to be curved but likely if everyones final class scores are lower then expected he will curve the class
- Wed Feb 19, 2020 1:23 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Midterm question 8 [ENDORSED]
- Replies: 5
- Views: 505
Midterm question 8 [ENDORSED]
On the midterm we were asked how entropy is different based on irreversible expansion or reversible expansion. Is it true that entropy is the same for both since it is a state function?
- Wed Feb 19, 2020 1:19 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Salt Bridge
- Replies: 4
- Views: 284
Salt Bridge
What is the salt bridges function in a galvanic cell/battery?
- Wed Feb 19, 2020 1:17 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Differences in Heat Capacity
- Replies: 4
- Views: 331
Re: Differences in Heat Capacity
We need to know heat capacity for calorimeters, which is just the heat capacity required to raise a substance 1 degree celcius. But also specific and molar heat capacities are important to know. Specific being the amount of heat required to raise 1 gram of a substance 1 degree celcius, and molar bei...
- Wed Feb 19, 2020 1:12 pm
- Forum: Balancing Redox Reactions
- Topic: Test 2 [ENDORSED]
- Replies: 12
- Views: 650
Test 2 [ENDORSED]
Is test 2 next week? And if so what subject areas is it covering?
- Sun Feb 02, 2020 11:46 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Bond Enthalpies
- Replies: 2
- Views: 87
Re: Bond Enthalpies
Normally you are given the bond enthalpy when trying to solve the problem. I don't think we have to learn how to calculate the enthalpy of a broken bond.
- Sun Feb 02, 2020 11:45 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Enthalpy
- Replies: 1
- Views: 41
Enthalpy
What is the difference between entropy and heat gained/lost? I'm still very unclear on this.
- Sun Feb 02, 2020 11:44 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: pKa and pKb
- Replies: 3
- Views: 288
Re: pKa and pKb
You know the most essential parts. Just know that for acidic reactions you should apply pKa. If you are only given pKb then you can calculate pKa because their products are equal to 14.
- Sun Feb 02, 2020 11:42 pm
- Forum: Ideal Gases
- Topic: Ideal gas constant
- Replies: 4
- Views: 242
Re: Ideal gas constant
They might have different units associated with them, or maybe one is for higher pressure and one is for lower pressure. If they are associated with the same units then you may be able to use them interchangeably.
- Sun Feb 02, 2020 11:39 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Car Engine
- Replies: 4
- Views: 211
Re: Car Engine
Because it gives off heat to its surroundings and also mass is inputed into the system from gasoline
- Sun Jan 26, 2020 9:21 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Different Enthalpy Strategies
- Replies: 5
- Views: 160
Different Enthalpy Strategies
Is there any benefit to using one strategy for calculating bond enthalpies over another? Or will we be asked to use certain strategies based on what the question is asking?
- Sun Jan 26, 2020 9:19 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Midterm
- Replies: 8
- Views: 310
Midterm
Anyone know what week the midterm is? Is it week 6?
- Sun Jan 26, 2020 9:18 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Water Phase Change
- Replies: 6
- Views: 161
Re: Water Phase Change
It is because there is energy required to break bonds between water molecules. The hydrogen bonds in water are strong so it takes a lot of energy, therefore more energy is stored in gas at the same temperature than at liquid.
- Sun Jan 26, 2020 9:16 pm
- Forum: Ideal Gases
- Topic: PLF material
- Replies: 3
- Views: 162
Re: PLF material
If they are based on the same material then they likely use similar if not the same worksheets. I doubt you will miss much if you attend one session over the other.
- Sun Jan 26, 2020 9:14 pm
- Forum: Phase Changes & Related Calculations
- Topic: Enthalpy Calculations
- Replies: 5
- Views: 124
Re: Enthalpy Calculations
I doubt we will have to memorize any formulas as in most Lavelle classes the formulas are all provided on the test.
- Sun Jan 19, 2020 7:39 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: reactants and products in dynamic equilibria
- Replies: 3
- Views: 201
Re: reactants and products in dynamic equilibria
Because certain molecules are more stable then others so those are favored in reactions over unstable molecules.
- Sun Jan 19, 2020 7:38 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Pa and Pb
- Replies: 4
- Views: 200
Pa and Pb
How do you no whether to use Pa or Pb in an acid base calculation?
- Sun Jan 19, 2020 7:37 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: exothermic/endothermic rxns
- Replies: 4
- Views: 145
Re: exothermic/endothermic rxns
Because more energy is provided to the system so in an endothermic reaction that requires heat to make products, it is easier for the reactants to become products if they are provided with heat, and vise versa for exothermic reactions
- Sun Jan 19, 2020 7:36 pm
- Forum: Ideal Gases
- Topic: When does the Ideal Gas Law Fail?
- Replies: 7
- Views: 1235
Re: When does the Ideal Gas Law Fail?
It fails at low temperatures and higher pressures because intermolecular forces become important, it also fails with heavy gases.
- Sun Jan 19, 2020 7:34 pm
- Forum: Ideal Gases
- Topic: Step Up Session Material
- Replies: 2
- Views: 57
Re: Step Up Session Material
The one that I have been to worked out of the book as I came and asked about specific problems in the textbook.
- Sun Jan 12, 2020 3:53 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: ICE tables
- Replies: 3
- Views: 77
ICE tables
Do you always have to use ice tables when determining equilibrium concentrations, or is it possible to do calculations without the ice tables?
- Sun Jan 12, 2020 3:52 pm
- Forum: Ideal Gases
- Topic: Test 1
- Replies: 7
- Views: 347
Re: Test 1
He said in his outlines you have to be able to calculate a certain variable of pv=nrt given all four of the others. So just simple algebraic calculations I think.
- Sun Jan 12, 2020 3:51 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Rounding in K problems
- Replies: 4
- Views: 223
Re: Rounding in K problems
You aren't supposed to round until the end, the answer will be the most accurate if the exact numbers are used until the final answer.
- Sun Jan 12, 2020 3:49 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Test 1
- Replies: 6
- Views: 213
Test 1
Is test 1 this week like it was in 14A or do we have more time before this test.
- Sun Jan 12, 2020 3:47 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: When to use Kc vs Kp
- Replies: 7
- Views: 179
Re: When to use Kc vs Kp
We use Kp when calculating partial pressure of gases and Kc when calculating concentration of aqueous solutions.
- Fri Dec 06, 2019 3:30 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Deciding shape
- Replies: 3
- Views: 209
Re: Deciding shape
If you determine the coordination number you can determine how many molecules bond to it, if you find this out you can find the molecular shape.
- Fri Dec 06, 2019 3:27 pm
- Forum: Sigma & Pi Bonds
- Topic: Change in hybridization based on sigma and pi bonds
- Replies: 1
- Views: 139
Change in hybridization based on sigma and pi bonds
Does hybridization of orbitals change depending on if the bonds are sigma or pi?
- Fri Dec 06, 2019 3:26 pm
- Forum: Lewis Structures
- Topic: Oxoacids
- Replies: 1
- Views: 230
Re: Oxoacids
I don't think so, just remember that if it is an acid with a center molecule with oxygens and hydrogens around it. The oxygens bond to the center molecule and the hydrogens bond to the oxygens.
- Fri Dec 06, 2019 3:11 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: speed of light
- Replies: 2
- Views: 250
Re: speed of light
Electrons are never found in the nucleus even if the uncertainty in velocity is less than the speed of light. That being said I don't think there is a case where this is ever possible because heisenbergs uncertainty principle would likely always show that an electrons velocity uncertainty is more th...
- Fri Dec 06, 2019 3:06 pm
- Forum: Hybridization
- Topic: Hybridization - 2F9 part d
- Replies: 1
- Views: 105
Re: Hybridization - 2F9 part d
I find it more helpful to look at the lewis structure and not the electron configuration when looking at hybridization. Use the regions of electron density to figure out what the hybridization is. PCL3 is sp^3 because it has 4 regions of electron density because it has three bonds and one lone pair....
- Fri Dec 06, 2019 3:03 pm
- Forum: Hybridization
- Topic: hybridization of lone pairs
- Replies: 4
- Views: 283
Re: hybridization of lone pairs
Yes, hybridization is solely based on regions of electron density. An atom with two bonds and one lone pair would have the same hybridization (sp^2) as something with three bonds and no lone pair.
- Sun Dec 01, 2019 5:14 pm
- Forum: Acidity & Basicity Constants and The Conjugate Seesaw
- Topic: Inductive Effect
- Replies: 1
- Views: 56
Re: Inductive Effect
The inductive effect is when conjugate acids and bases are stabilized by a strong electronegative atom. These atoms pull the electrons in more which makes them more stable in solution.
- Sun Dec 01, 2019 5:10 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: Test Grades
- Replies: 6
- Views: 408
Test Grades
Is anyone elses test grade in myUCLA for test 2 a zero? I'm a little concerned as I never got my test back and am still not seeing a grade in myUCLA.
- Sun Dec 01, 2019 5:09 pm
- Forum: Lewis Acids & Bases
- Topic: strong and weak acids
- Replies: 3
- Views: 276
Re: strong and weak acids
An acid or base is strong if they completely disassociate in solution. I'm pretty sure for the final we just need to know a few strong acids and a few strong bases, the bases being, KOH, NaOH, Ba(OH)2, Cs(OH), Sr(OH)2, Ca(OH)2, Li(OH), and Rb(OH) these are all group one and two elements with OH on t...
- Sun Dec 01, 2019 5:04 pm
- Forum: Naming
- Topic: Naming for the final
- Replies: 6
- Views: 447
Re: Naming for the final
Some of the general rules for naming are as follows. Use the prefixes di, tri, tetra, penta, hexa, octa, if there are two or more of certain molecules. For ligands, name them in alphabetical order remembering to replace ammonia with ammine, or anything ending in ide with an o. Also cations go first ...
- Sun Dec 01, 2019 5:00 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: pH scale
- Replies: 12
- Views: 605
pH scale
Why is the pH scale from 0-14 if it can be negative and go beyond 14?
- Sun Dec 01, 2019 4:58 pm
- Forum: Conjugate Acids & Bases
- Topic: Conjugate acids/bases
- Replies: 1
- Views: 91
Conjugate acids/bases
I'm still not exactly sure what a conjugate acid is. If a molecule gives off a proton in a reaction, in the reverse reaction is it then the conjugate base since it receives a proton?
- Sun Dec 01, 2019 4:56 pm
- Forum: Acidity & Basicity Constants and The Conjugate Seesaw
- Topic: Meaning of the constants
- Replies: 2
- Views: 172
Re: Meaning of the constants
A larger constant means it is a stronger base. Keep in mind the Ka value tends to be close to zero, so a 10^-2 value will be a stronger base then a 10^-6 value. However the pKa value is on a logarithmic scale and therefore a smaller pKa value means a stronger acid/base so a lower pH if it's an acid ...
- Sun Nov 24, 2019 3:44 pm
- Forum: DeBroglie Equation
- Topic: Slow Moving Large Objects
- Replies: 2
- Views: 268
Re: Slow Moving Large Objects
Even though in De Broglies wave equation yes it would technically have a wavelength. I think that De Broglies equation only applies to objects with relatively fast velocity. Something with an extremely low velocity would essentially just not be moving. The best example I could think of is a tectonic...
Re: Final
There will definitely be review sessions. I'm almost positive on Friday of week 10 lavelle does a comprehensive review of important topics in class.
- Sun Nov 24, 2019 3:38 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Bronsted vs. Lewis Acids and Bases
- Replies: 4
- Views: 280
Bronsted vs. Lewis Acids and Bases
What is the difference between a Bronsted acid/base and a lewis acid/base?
- Sun Nov 24, 2019 3:36 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: transition metals
- Replies: 2
- Views: 119
Re: transition metals
Transition metals have different oxidation numbers depending on their environment. They can have different oxidation numbers because they are good for electron transfer so electrons can pass through them very easily. Certain oxidation numbers allow for a certain number of ligands to bind to these tr...
Re: Naming
If there is a molecule with an -ide at the end drop the ide and add an o. Another tip is cations go first and anions go second. Also if it is an anion you add ate to the end. There are a bunch of other strategies and I think there are also some exceptions to these rules.
- Sun Nov 17, 2019 1:40 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: Dipole Moments
- Replies: 3
- Views: 211
Re: Dipole Moments
Dipole moments cancel when the dipoles in a molecule are facing opposite directions. However they also cancel in a trigonal planar because they are all 120 degrees apart and each dipole faces out, causing them all to cancel.
- Sun Nov 17, 2019 1:38 pm
- Forum: Sigma & Pi Bonds
- Topic: Test 2 Sigma and Pi bonds
- Replies: 5
- Views: 179
Test 2 Sigma and Pi bonds
Will Sigma and Pi bonds be on test 2? And if so what is the difference between a sigma and a pi bond, I don't recall going over this in class.
- Sun Nov 17, 2019 1:37 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Octahedral??
- Replies: 4
- Views: 648
Re: Octahedral??
I think it is because of the fact that it is a 3-D shape. So if it were in 2D it would be hexagonal, but due to the fact that it has molecules all of bond angle 90 degrees on the xyz plane it is an octahedral. Lavelle explained something about how the shape when drawn in geometric patterns relates t...
- Sun Nov 17, 2019 1:33 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: vapor pressure
- Replies: 4
- Views: 312
Re: vapor pressure
I'm almost positive we don't have to know vapor pressure for this test. However if we do it is defined as the pressure exerted by a vapor when in thermodynamic equilibrium.
- Sun Nov 17, 2019 1:31 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: This Week Test
- Replies: 12
- Views: 702
This Week Test
Will the test this week just be on VSEPR model of atoms or will it also include interionic and intermolecular forces?
- Sun Nov 17, 2019 1:28 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: Boiling Points
- Replies: 7
- Views: 537
Re: Boiling Points
Boiling points are dependent on the strength of force. The boiling point of a molecule is higher if the bonds are stronger because it takes more energy to break the bonds. So a molecule with shorter bonds will tend to have a higher boiling point.
- Sun Nov 17, 2019 1:26 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Strength of Repulsion
- Replies: 4
- Views: 309
Re: Strength of Repulsion
Lone pairs have a stronger repulsion because they are two negatively charged electrons. So they push repulse each-other a lot more then an electron and an atom would repulse because atoms don't have as strong of a negative charge if they are even charged at all. Just remember that lone-pairs are two...
- Sun Nov 17, 2019 1:24 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Interactions
- Replies: 3
- Views: 111
Re: Interactions
Yes to both questions, ion-dipole interactions are the strongest because ions tend to have a strong charge which attracts the charged dipoles of other molecules.
- Sun Nov 03, 2019 11:24 pm
- Forum: SI Units, Unit Conversions
- Topic: Converting SI units
- Replies: 3
- Views: 334
Converting SI units
What is the rule for converting SI units on the test. Will we be penalised if we get the sig figs wrong?
- Sun Nov 03, 2019 11:23 pm
- Forum: Balancing Chemical Reactions
- Topic: Balancing Chemical Equations
- Replies: 4
- Views: 405
Re: Balancing Chemical Equations
From left to right I think that it is 6, 10 = 5, 9, 6, 3.
- Sun Nov 03, 2019 11:20 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Heisenberg Indeterminacy (Uncertainty) Equation
- Replies: 5
- Views: 344
Re: Heisenberg Indeterminacy (Uncertainty) Equation
There is an inverse relationship because h/4 pi is a constant. So since uncertainty in momentum and uncertainty in position multiply to be greater than that number, then as one gets bigger the other one will get smaller.
- Sun Nov 03, 2019 11:17 pm
- Forum: Lewis Structures
- Topic: Valence Electrons on Oxygen
- Replies: 3
- Views: 146
Re: Valence Electrons on Oxygen
Remember that chlorine is one of the three elements that regularly violates the octet rule. So it is likely that oxygen might double bond with chlorine in order to keep its octet, while chlorine would violate the rule since it doesn't need to be in octet to be stable.
- Sun Nov 03, 2019 11:12 pm
- Forum: Electronegativity
- Topic: Figuring it out without the trend?
- Replies: 4
- Views: 125
Re: Figuring it out without the trend?
Look at the periods and the groups, the farther right an element is in a group the more electronegative it is, and the farther up it is in a group the more electronegative it is.
- Fri Oct 25, 2019 3:37 pm
- Forum: Resonance Structures
- Topic: Bond Lengths
- Replies: 5
- Views: 601
Re: Bond Lengths
Even though the bond lengths are represented as different, with double bonds, single bonds, etc. In resonance structures the electrons are delocalized, so the lewis structures aren't necessarily a good representation of how the molecule looks. In reality resonance structures share all the electrons ...
- Fri Oct 25, 2019 3:35 pm
- Forum: Octet Exceptions
- Topic: Expanded Valence Shells
- Replies: 4
- Views: 163
Expanded Valence Shells
Are phosphorus, sulfur and chlorine the only three elements with expanded valence shells?
- Fri Oct 25, 2019 3:33 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Formal Charge and Molecules
- Replies: 4
- Views: 232
Formal Charge and Molecules
Does the formal charge of a molecule always equal its ionic charge? In class for the SO4 2- ion the charge was for the whole molecule. Was that just a coincidence or do the formal charges of each individual atom always add up to the formal charge of the molecule?
- Fri Oct 25, 2019 3:30 pm
- Forum: Trends in The Periodic Table
- Topic: Electron Affinity
- Replies: 4
- Views: 230
Re: Electron Affinity
Atoms always want to get to a their lowest possible energy. So it makes sense that electron affinity increases as you go towards the top right of the periodic table. Atoms like halogens have high electron affinities because they will release the most energy by getting to the stable noble gas state
- Fri Oct 25, 2019 3:26 pm
- Forum: DeBroglie Equation
- Topic: Linear Momentum
- Replies: 6
- Views: 203
Re: Linear Momentum
You somewhat answered your own question. Linear momentum relates to the de broglie equation in that it has an inverse relationship with wavelength. So yes a larger momentum means a smaller wavelength. For example a car moving 60 mph has a much larger momentum then an electron, so it has a much small...
- Sun Oct 20, 2019 4:36 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Uncertainty in Speed
- Replies: 2
- Views: 124
Uncertainty in Speed
How do we calculate the uncertainty in speed if the speed is 5+- 5 m/s? Is the uncertainty 5m/s or 10?
- Sun Oct 20, 2019 4:34 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Inverse Relation
- Replies: 3
- Views: 198
Re: Inverse Relation
Yes, with more uncertainty in position comes less in position and vise versa because they multiply to a constant.
- Sun Oct 20, 2019 4:33 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: 1.B.25
- Replies: 1
- Views: 114
Re: 1.B.25
It essentially just means that you use the diameter of the atom to use as the uncertainty in position of the electron. The model of the one dimensional box is a line where the position of the electron in uncertain, it just means you don't have to find the area of the atom.
- Fri Oct 18, 2019 5:00 pm
- Forum: Photoelectric Effect
- Topic: The Work Function
- Replies: 15
- Views: 968
Re: The Work Function
The work function is the energy it takes to expel an electron from a certain metal. The energy of the photon is E=hv and if you subtract the work function from that energy then the difference is the kinetic energy of the electron which is E=MV.
- Fri Oct 18, 2019 4:54 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Heisenberg's uncertainty
- Replies: 2
- Views: 151
Re: Heisenberg's uncertainty
Electrons have to be outside of the atoms nucleus. Photons are in the nucleus, but if electrons were there, according to heisenbergs principle the uncertainty in the position would be too small and would therefore make the indeterminacy in the speed of the electron faster then the speed of light, wh...
- Sun Oct 13, 2019 6:56 pm
- Forum: Limiting Reactant Calculations
- Topic: Can't Find Limiting Reactant
- Replies: 4
- Views: 328
Re: Can't Find Limiting Reactant
You would first balance the equations and then convert the grams of each compound into moles. Then you would see which reactant would yield less of the product. By doing this you will see which reactant is limiting the mass of the product.
- Sun Oct 13, 2019 6:54 pm
- Forum: Significant Figures
- Topic: Significant Figures on Test 1
- Replies: 3
- Views: 264
Significant Figures on Test 1
I was just curious the rule that we were supposed to used for answering with signifigant figures on test 1? I was also wondering if the T.A's will be grading with sig figs in mind on this test?
- Sun Oct 13, 2019 6:51 pm
- Forum: *Black Body Radiation
- Topic: Black Body Radiation
- Replies: 2
- Views: 661
Re: Black Body Radiation
Black body radiation is not at all prevalent in our daily lives. Although it does exist in black holes to the extent of my knowledge there is no black body radiation present on Earth.
- Sun Oct 13, 2019 6:43 pm
- Forum: Properties of Electrons
- Topic: Interference.
- Replies: 2
- Views: 222
Re: Interference.
As illustrated in Professor Lavelle's standing wave diagram, energy levels can be seen through the electrons patterns of constructive and destructive interference patterns. You can visualize an electrons wave pattern by looking at the standing wave motion and how it switches from peaks to valleys, i...
- Sun Oct 13, 2019 6:41 pm
- Forum: Properties of Light
- Topic: Atomic Spectra Pre-Assessment #12
- Replies: 2
- Views: 119
Re: Atomic Spectra Pre-Assessment #12
Not sure the exact setup but in lecture Professor Lavelle spoke of pointing a light source at whatever metal you are testing. If electrons are ejected from that metal then the light source has a high enough frequency/energy to raise the electron to its second energy level (n=2).
- Fri Oct 04, 2019 2:21 pm
- Forum: Limiting Reactant Calculations
- Topic: L7
- Replies: 2
- Views: 100
L7
How is it possible that the mass of water in the products is so much larger than the mass of the fat that is given in the reactants side? Isn't it impossible for mass to be created during a reaction?
- Fri Oct 04, 2019 2:20 pm
- Forum: Molarity, Solutions, Dilutions
- Topic: G11
- Replies: 1
- Views: 78
G11
I'm confused how to use the equation M1V1 = M2V2 when they only give us two molarities. Is there another equation we are supposed to be given?