Why does reduction take place spontaneously at the electrode with higher concentration?
(14.93)
Search found 92 matches
- Sat Mar 16, 2019 2:22 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Reduction/Concentration cells
- Replies: 1
- Views: 268
- Sat Mar 16, 2019 1:17 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Week 10 Discussion Notes (2E,2I,2K)
- Replies: 6
- Views: 12151
Re: Week 10 Discussion Notes (2E,2I,2K)
Hi, does anyone know why delta H was 300 and not -300 when calculating the reverse activation energy? Didn't they give it as -300, and it's an exothermic reaction so deltaH should be negative?
- Wed Mar 13, 2019 11:59 pm
- Forum: General Rate Laws
- Topic: elementary step
- Replies: 1
- Views: 216
elementary step
If water is a reactant, do we put this as a reactant in the rate law? Or do we not put liquids when writing the rate law?
- Wed Mar 13, 2019 12:13 pm
- Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
- Topic: Batteries
- Replies: 2
- Views: 512
Batteries
Is charging our phone batteries electrolysis or a galvanic example? Can someone provide an example of electrolysis and an example of a galvanic reaction?
- Mon Mar 11, 2019 3:23 pm
- Forum: *Electrophiles
- Topic: final
- Replies: 7
- Views: 1899
Re: final
There will probably be an emphasis on kinetics since it was the most recent unit and we spent the longest amount of time on it. Just study everything though.
- Mon Mar 11, 2019 3:16 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Rate constant
- Replies: 4
- Views: 857
Rate constant
Can rate constants be negative?
- Mon Mar 11, 2019 3:15 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: E
- Replies: 1
- Views: 233
E
Why does E decrease over time but E at standard conditions does not? How exactly does E decrease over time?
- Wed Mar 06, 2019 11:30 pm
- Forum: General Rate Laws
- Topic: 15.3
- Replies: 2
- Views: 376
15.3
For 15.3 part a when finding the reaction rate of NO2, how come we don't divide by 2, the coefficient of NO2?
- Wed Mar 06, 2019 10:47 pm
- Forum: Balancing Redox Reactions
- Topic: 14.119
- Replies: 1
- Views: 279
14.119
For this problem in the 6th edition, why aren't we using Au2+ for the anode rxn (instead of Au+)? Doesn't its paired anode half rxn involving (CN)2 have a 2- charge?
- Mon Mar 04, 2019 5:36 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Dilution effect on cell potential
- Replies: 1
- Views: 276
Re: Dilution effect on cell potential
When we dilute a solution, we decrease the number of ions, so I believe this has to do with Le Chatelier's Principle, in that reducing the number of ions in the anode side will cause the reaction to favor the products and the E cell potential to increase.
- Mon Mar 04, 2019 5:16 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: 6th Edition 14.41
- Replies: 3
- Views: 420
Re: 6th Edition 14.41
I believe it's because H2 is an element in its most stable form already? Maybe it has something to do with the formation reaction being 0?
- Mon Mar 04, 2019 5:13 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Unique/Formation and Degradation
- Replies: 2
- Views: 277
Unique/Formation and Degradation
What's the difference between unique rate law and the rate of formation/degradation?
- Thu Feb 28, 2019 12:20 am
- Forum: Balancing Redox Reactions
- Topic: Oxidation Numbers
- Replies: 3
- Views: 446
Re: Oxidation Numbers
I don’t think it will be given but some helpful tips is that the Halogens all have a -1 charge. Column 1 all has a +1 charge. And the elements in the same row as oxygen all have -2 charge.
- Thu Feb 28, 2019 12:19 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Test #2
- Replies: 1
- Views: 261
Re: Test #2
I believe it’s up to 35, ending in cell diagrams.
- Thu Feb 28, 2019 12:18 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: 14.27, 6th Edition
- Replies: 1
- Views: 232
Re: 14.27, 6th Edition
It’s because that equation is not the redox Reaction, but just another half reaction. So the reactions aren’t occurring at the same time as would the two half reactions and the overall redox reactions. We use G because G is a state function.
- Thu Feb 28, 2019 12:16 am
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: E
- Replies: 4
- Views: 480
E
E is not a state function, but how come we can add to get the E of the redox reactions?
- Mon Feb 18, 2019 5:34 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gibbs Free Energy and equilibrium
- Replies: 2
- Views: 339
Re: Gibbs Free Energy and equilibrium
Equilibrium means the forward rate equals the reverse rate. Free energy refers to the amount of energy available to do work. So when the energy of the reactants/products aren't equal, the system is not at equilibrium.
- Mon Feb 18, 2019 5:33 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Finding standard reaction for a reaction
- Replies: 3
- Views: 449
Re: Finding standard reaction for a reaction
Oxygen is still used in all three formulas. For enthalpy, the formation reaction is the deltaH of the entire reaction. In the textbook, Hrxn is already given of H20, with Oxygen taken in to account. And for Gibbs Free Energy, since the formula is G=H-TS, if entropy and enthalpy use O2, so will Gibbs.
- Mon Feb 18, 2019 5:30 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Entropy
- Replies: 3
- Views: 455
Entropy
Does entropy increase only when the number of moles of gas increase? Or do we look at solids and liquids too?
- Mon Feb 11, 2019 5:51 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Delta U and deltaH
- Replies: 1
- Views: 254
Re: Delta U and deltaH
deltaU=q+w
At constant pressure, we use w=-PdeltaV.
This becomes deltaU= q -PdeltaV
Since we assume constant pressure, q at constant pressure = deltaH
Thus, deltaU= deltaH- PdeltaV
At constant pressure, we use w=-PdeltaV.
This becomes deltaU= q -PdeltaV
Since we assume constant pressure, q at constant pressure = deltaH
Thus, deltaU= deltaH- PdeltaV
- Mon Feb 11, 2019 5:45 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Question 8.19
- Replies: 2
- Views: 303
Re: Question 8.19
Your formula is correct, we are adding q of copper and q of water together. Try using mcdeltaT for both, where mass and heat capacity is in grams. Also double check that your units are in Joules.
- Mon Feb 11, 2019 5:42 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: q and w = 0
- Replies: 3
- Views: 423
Re: q and w = 0
q=0 if the problem is adiabatic. w=0 if there is no volume change. q=-w if deltaU=0, which occurs when the system is in isothermal conditions. This is because isothermal occurs at a constant temperature, and for ideal gases, U=3/2nRT. For solids and liquids, q=-w because U=q+w. q and w will both be ...
- Mon Feb 11, 2019 5:27 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: 1 molecule
- Replies: 2
- Views: 269
1 molecule
When calculating Degeneracy(W):
If the question says we have 1 molecule of a compound, does this mean the number of atoms is 1 or 6.023*10^23?
If the question says we have 1 molecule of a compound, does this mean the number of atoms is 1 or 6.023*10^23?
- Mon Feb 04, 2019 2:05 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Units
- Replies: 2
- Views: 339
Units
When finding deltaH of the rxn, when are our units kJ and when are the units kJ/mol? I thought Hf is kJ/mol, but in some cases Hrxn overall is kJ/mol as well?
- Mon Feb 04, 2019 1:53 pm
- Forum: Calculating Work of Expansion
- Topic: Degeneracy
- Replies: 6
- Views: 839
Re: Degeneracy
Degeneracy(W) is defined as the number of possible ways a system can exist in a specific energy state. It is determined by the number of possible states, raised to the number of particles involved. For example, two particles A and B have two possible states. Thus 2 states and 2 particles is 2^2, and...
- Mon Feb 04, 2019 1:50 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Heat capacity
- Replies: 2
- Views: 302
Re: Heat capacity
Both, but usually specific/molar heat capacity is given in a chart. The only time we really have to calculate heat capacity is if we were given deltaH for an entire reaction, and the temperature change, and thus heat capacity = deltaH/deltaT (kJ/1 Celsius).
- Mon Feb 04, 2019 1:45 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Outside Factors
- Replies: 1
- Views: 216
Re: Outside Factors
I don't believe so, because if deltaU= q+w, those two variables are the only factors that affect internal energy. This is why, for an isolated system, if no work or heat can be exchanged, deltaU=0.
- Thu Jan 31, 2019 9:06 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: U:Internal Energy
- Replies: 4
- Views: 453
U:Internal Energy
What's the difference between
1) deltaU= q+w
and
2) deltaU= deltaH -PV
Is the second equation only for constant pressure? Are there certain circumstances to use each equation or are they interchangeable?
1) deltaU= q+w
and
2) deltaU= deltaH -PV
Is the second equation only for constant pressure? Are there certain circumstances to use each equation or are they interchangeable?
- Mon Jan 28, 2019 1:58 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Q and H
- Replies: 2
- Views: 320
Q and H
What's the difference between deltaQ and deltaH if they both measure change in heat of a reaction?
- Mon Jan 28, 2019 1:57 pm
- Forum: Ideal Gases
- Topic: Q and K
- Replies: 13
- Views: 1336
Re: Q and K
Q is when the reaction is not at equilibrium, K is when the reaction is at equilibrium. If Q<K, the reaction shifts right to favor the products. If Q>K the reaction shifts left to favor the reactants. Most of the time it is Q that changes, not K. K is changed by temperature only.
- Mon Jan 28, 2019 1:55 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Extensive vs intensive
- Replies: 2
- Views: 266
Re: Extensive vs intensive
Extensive Properties depend on the amount of substance given, such as heat capacity. Intensive Properties do not depend on the amount of substance given, since it's already in the calculation itself. (Specific heat capacity and molar heat capacity)
- Mon Jan 28, 2019 1:54 pm
- Forum: Phase Changes & Related Calculations
- Topic: Properties
- Replies: 2
- Views: 347
Re: Properties
Extensive Properties depend on the amount of substance given, such as heat capacity. Intensive Properties do not depend on the amount of substance given, since it's already in the calculation itself. (Specific heat capacity and molar heat capacity)
- Mon Jan 28, 2019 1:52 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Heat capacity
- Replies: 1
- Views: 182
Re: Heat capacity
Heat capacity is an extensive property and thus depends on the amount of product formed. To calculate it, we find the heat required (Joules or kilo Joules) to raise the temperature of an object by 1 degree Celsius. Heat Capacity branches off into Specific heat capacity and molar heat capacity, which...
- Wed Jan 23, 2019 2:14 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: [H30+]
- Replies: 1
- Views: 94
[H30+]
When adding an acid and the [H30+] ends up being less than 10^-7 due to diluteness of the acid wee added, does anyone remember what Lavelle said to do? Do we just write that the pH is 7 or do we have to add 10^-7 to [H30+] first?
- Wed Jan 23, 2019 1:58 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Ideal Gases
- Replies: 2
- Views: 369
Re: Ideal Gases
One example Lavelle gave in class was adding Helium to a reaction. Since Helium is a noble gas, it is basically unreactive and will not affect the reaction/shift equilibrium. I don't think we have to understand exactly how Helium will just "sit" in the reaction, but the main idea is that n...
- Wed Jan 23, 2019 1:54 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: State property
- Replies: 3
- Views: 341
Re: State property
Hi! A state property is defined as not dependent on a path taken to obtain a certain state. Think about the mountain example given in class. A person who takes a longer route will have done more work but will have climbed the same altitude at the end. Thus, work is not a state property because it ch...
- Fri Jan 18, 2019 3:33 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Endothermic
- Replies: 2
- Views: 276
Endothermic
For 11.87 in the 6th edition, the textbook states that X2 (g) —->2X (g) is an endothermic reaction since it takes heat to break the molecules of gas apart.
However, I thought catabolic (breaking down) reactions were exergonic?
However, I thought catabolic (breaking down) reactions were exergonic?
- Wed Jan 16, 2019 7:06 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Acid or Base
- Replies: 1
- Views: 199
Acid or Base
How can you tell if an aqueous compound acts as an acid or a base?
For example, if given NH2NH2, can’t this compound donate a H+ and also receive an H+?
For example, if given NH2NH2, can’t this compound donate a H+ and also receive an H+?
- Mon Jan 14, 2019 4:30 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 12.29
- Replies: 1
- Views: 135
12.29
When deciding how many sigfigs to use for pH/pOH, does the rule that only numbers after the decimal count as a sig dig apply for all values in the problem (Molarity, Liters, etc.) The pH values had 2 sig figs (like 3.24) but the problem only had one sig fig so I was wondering how the rule would work.
- Mon Jan 14, 2019 4:20 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Kw
- Replies: 2
- Views: 262
Kw
For water at temperatures higher than 25 degrees Celsius, we will have a different K value which changes the pH/pOH values. Does this mean that the pH for neutral water isn’t always 7? (So a pH of 7 doesn’t exactly mean neutral?)
- Fri Jan 11, 2019 2:43 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Adding a liquid
- Replies: 7
- Views: 564
Adding a liquid
Adding a gas only increases the pressure of a system so the equilibrium constant will not change. However, what happens if we add a liquid like water to the system? This will not change the pressure but will it increase the volume thereby changing K?
Or does adding a liquid also have no effect on K?
Or does adding a liquid also have no effect on K?
- Fri Jan 11, 2019 2:02 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Volume increasing
- Replies: 4
- Views: 293
Volume increasing
I’m Lavelle’s lecture today, he said that generally when volume decreases, the equilibrium will shift to the side with less moles of gas. So if volume increases, does equilibrium shift to the side with more moles of gas?
- Thu Jan 10, 2019 1:39 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: PArtial pressure= concentration?
- Replies: 2
- Views: 846
PArtial pressure= concentration?
When asked to find the partial pressure of a gas, is this the same thing as finding the equilibrium concentration?
If so, then why is Partial Pressure = conc (RT) ?
Isn't that equation saying that partial pressure = concentration * R * T not that partial pressure = concentration?
If so, then why is Partial Pressure = conc (RT) ?
Isn't that equation saying that partial pressure = concentration * R * T not that partial pressure = concentration?
- Wed Jan 09, 2019 4:38 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 11.41
- Replies: 1
- Views: 211
11.41
For 11.41 in the 6th edition, I was wondering if we would use an ICE table to solve this problem? Also, the book gave the initial amount of moles for NH4(NH2CO2) but I only used the final amount of moles of CO2 to calculate the final equilibrium concentration of NH3 so was this information necessary?
- Wed Jan 09, 2019 3:35 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Equilibrium constant for Gas
- Replies: 1
- Views: 199
Equilibrium constant for Gas
When writing the equilibrium constant equation for gases, is it ok to use the [] notation as we do for aqueous solutions or do we have to use P (partial pressure) notation?
- Wed Jan 09, 2019 3:23 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Initial Concentration
- Replies: 3
- Views: 305
Initial Concentration
When doing ICE tables and the initial concentration of a reactant/product is not given, do we just assume that it is 0?
- Fri Dec 07, 2018 6:47 pm
- Forum: Administrative Questions and Class Announcements
- Topic: FINAL PRACTICE - Lyndon's Churro Review Session [ENDORSED]
- Replies: 118
- Views: 21822
33c [ENDORSED]
For 33c, since we have a weak base, we will have less OH since it doesn’t completely dissociate. However, since less OH means more H3O, this means less pOH should mean more pH. Why did Lyndon say lower pH instead?
- Fri Dec 07, 2018 6:25 pm
- Forum: Bronsted Acids & Bases
- Topic: Cl- and F-
- Replies: 4
- Views: 606
Cl- and F-
Why is it that Cl- does nothing when dissolved in water but F- has the potential to gain a proton and become HF?
- Fri Dec 07, 2018 6:23 pm
- Forum: Bronsted Acids & Bases
- Topic: List of strong/weak acids/bases
- Replies: 3
- Views: 485
List of strong/weak acids/bases
Does anyone have a complete list of the strong and weak acids/bases we should memorize?
- Thu Dec 06, 2018 3:07 am
- Forum: Naming
- Topic: in prep for the final
- Replies: 1
- Views: 108
Re: in prep for the final
Lavelle has a worksheet on his website of all the ligand names you should know! :)
- Thu Dec 06, 2018 3:05 am
- Forum: Lewis Acids & Bases
- Topic: HCl vs. HI
- Replies: 7
- Views: 794
HCl vs. HI
HI is a stronger acid because H and I have a longer/weaker bond and the H+ ions will thus dissociate more, resulting in a stronger acid. However, Cl is more electronegative (another stronger acid property).
So in determining the strength of an acid, does bond length trump electronegativity?
So in determining the strength of an acid, does bond length trump electronegativity?
- Mon Dec 03, 2018 11:21 pm
- Forum: Lewis Acids & Bases
- Topic: KBr
- Replies: 5
- Views: 463
KBr
Why is KBr neutral when dissolved in water, but KF is not?
For 6th edition 12.65, how can we tell by looking at the salt, if it will release H+ or OH- in water?
salts:
AlCl3
Cu(NO3)2
For 6th edition 12.65, how can we tell by looking at the salt, if it will release H+ or OH- in water?
salts:
AlCl3
Cu(NO3)2
- Mon Dec 03, 2018 11:18 pm
- Forum: Conjugate Acids & Bases
- Topic: B(OH)3 conjugate base
- Replies: 1
- Views: 623
B(OH)3 conjugate base
Hi what would be the conjugate base for B(OH)3?
Do we just add an H to it? So it would be B(OH)3H+?
Do we just add an H to it? So it would be B(OH)3H+?
- Mon Dec 03, 2018 4:12 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: As2O3 and Bi2O3
- Replies: 1
- Views: 258
As2O3 and Bi2O3
Can someone explain why As2O3 and Bi2O3 are amphoteric?
Also, in Lavelle's slides, As2O3 was labeled as an acidic oxide, so I'm not sure if that was a mistake?
Also, in Lavelle's slides, As2O3 was labeled as an acidic oxide, so I'm not sure if that was a mistake?
- Mon Dec 03, 2018 3:57 pm
- Forum: Biological Examples
- Topic: Structure of a hemoglobin
- Replies: 1
- Views: 180
Structure of a hemoglobin
Can someone explain the exact structure of a hemoglobin/myoglobin molecule? From what I remember there are four myoglobins that make up a hemoglobin. (Each myoglobin binds 1 O2) A myoglobin = heme complex + protein. Heme complex = Fe and 4 other things/2 proteins? (Fe is octahedral but I'm not sure ...
Order/OH2
Hi, for the compound sodium bisoxalato(diaqua)ferrate(III), I was wondering what it meant when diaqua was in parenthesis? Also, the book wrote the water part as OH2 instead of H2O. Would it be wrong if I wrote it as H2O? Lastly, does order of the ligands matter when we're given the name and have to ...
- Mon Dec 03, 2018 3:48 pm
- Forum: Naming
- Topic: nitro vs nitrito
- Replies: 3
- Views: 677
nitro vs nitrito
I was looking over the ligands naming sheet Lavelle posted and saw that there was a "nitro" and a "nitrito" but am not sure what the difference is/how to distinguish which name to use.
Thanks!
Thanks!
- Sun Dec 02, 2018 10:57 pm
- Forum: Naming
- Topic: coordination number
- Replies: 1
- Views: 184
Re: coordination number
Coordination Number is based off of the number of bonds to the central metal atom. The Complex is made up of the central metal atom and its ligands (which is connected by bonds). The bonds(Coordination #) don't exactly "affect" the Complex, it's more of a component thing.
- Tue Nov 27, 2018 12:17 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Test 3
- Replies: 38
- Views: 2743
Re: Test 3
My TA said these would be the topics:
-VSEPR, Molecular Geometry, Lewis Structures
-Intermolecular Forces
-Hybridization
-Polarizability
-VSEPR, Molecular Geometry, Lewis Structures
-Intermolecular Forces
-Hybridization
-Polarizability
- Tue Nov 27, 2018 12:15 am
- Forum: Dipole Moments
- Topic: Dipole Moment Calculation
- Replies: 3
- Views: 333
Re: Dipole Moment Calculation
Lavelle did mention this formula in class, but we will never actually have to calculate the dipole of anything, so this equation probably won't be tested.
- Tue Nov 27, 2018 12:13 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: polarity vs. nonpolarity
- Replies: 8
- Views: 693
Re: polarity vs. nonpolarity
Drawing the Lewis Structure usually helps! Once you draw the structure you can see if there is a net dipole moment - if there is one then it is polar. A helpful tip though is that C bonded to H is always nonpolar. Also, if the Lewis Structure is symmetric, it is usually nonpolar because the dipoles ...
- Tue Nov 20, 2018 3:15 pm
- Forum: Lewis Structures
- Topic: Midterm question
- Replies: 8
- Views: 696
Re: Midterm question
For this question, when finding bond lengths you would look at the average of the two since resonance is the blending of structures. Thus, you would take the average of 140pm and 120pm to get 130pm as the bond length.
- Tue Nov 20, 2018 3:12 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bond Angles
- Replies: 2
- Views: 177
Re: Bond Angles
The bond angles depend on the shape of the molecule so you’ll already know the smaller and bigger angles included. However, if you’re asking how to tell which angle is “90” or which one is “120” within the structure, you’ll have to visualize how the molecule is put together. There are many shapes to...
- Tue Nov 20, 2018 3:06 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: lone pairs
- Replies: 4
- Views: 452
Re: lone pairs
No, I believe only lone pairs on central atoms would affect the shape. This is why the trigonal pyramidal shape (3 bonded and 1 lone pair) has a bond angle that’s slightly less than a tetrahedral (4 bonded and 0 lone pair) bond angle of 109.5 degrees. Lone pairs on non central atoms do affect the re...
- Tue Nov 20, 2018 3:03 pm
- Forum: Hybridization
- Topic: S character in bond angles
- Replies: 1
- Views: 190
S character in bond angles
Hi, in chapter 4 question 43 (6th edition), the question asks what would happen to the bond angles as the “s” character increases?
Can someone explain what this means?
Can someone explain what this means?
- Thu Nov 15, 2018 3:12 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Fluorine and Electronegativity
- Replies: 2
- Views: 751
Fluorine and Electronegativity
Which will have a higher melting point: CHI3 or CHF3?
I assumed it was CHF3 since Fluorine is the most electronegative and will have a strong pull on the electrons of the other atoms. Can someone explain why CHI3 is higher?
(6th edition 6.5c)
I assumed it was CHF3 since Fluorine is the most electronegative and will have a strong pull on the electrons of the other atoms. Can someone explain why CHI3 is higher?
(6th edition 6.5c)
- Wed Nov 14, 2018 2:44 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Isobal Analogy
- Replies: 1
- Views: 240
Isobal Analogy
Hi, there is a question in the homework that mentions isobal analogy. (3.101b Edition 6) Can someone explain what this is and if it's important to know?
- Wed Nov 14, 2018 2:14 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: MgO vs BaO
- Replies: 5
- Views: 3573
MgO vs BaO
Hi, which molecule is more ionic/soluble in water?
MgO or BaO?
Since Mg is more electronegative than Ba, I would assume MgO is more ionic, but the textbook solutions say otherwise. (This is problem 3.79b 6th edition)
MgO or BaO?
Since Mg is more electronegative than Ba, I would assume MgO is more ionic, but the textbook solutions say otherwise. (This is problem 3.79b 6th edition)
- Sat Nov 10, 2018 4:37 pm
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Polarizability
- Replies: 4
- Views: 450
Re: Polarizability
Bigger atoms means a larger atomic radius, and as we can see from our periodic trends, the bigger the atom/molecule, the more electrons it will have. The electrons can cause distortion in nearby atoms, which ultimately affects the polarizability of the electron.
- Sat Nov 10, 2018 4:30 pm
- Forum: Ionic & Covalent Bonds
- Topic: Iconic v Covalent Strength
- Replies: 4
- Views: 412
Re: Iconic v Covalent Strength
Yes, as mentioned above ionic bonds tend to be between oppositely charged atoms. The general guideline is that if the electronegativity difference between the two is greater than 2, it is classified as an ionic bond. Also just wanted to note that while ionic bonds are stronger than covalent bonds, a...
- Sat Nov 10, 2018 4:21 pm
- Forum: Dipole Moments
- Topic: VSPER
- Replies: 8
- Views: 978
Re: VSPER
Hi, VSPER stands for Valence Shell Electron Pair Repulsion Model, and we use this rule to determine the shape of the molecule. As the name implies, this rule determines where bonding electrons and lone pairs will be in respect to the central atom.
- Sat Nov 03, 2018 10:36 pm
- Forum: Lewis Structures
- Topic: Lewis structures of compounds
- Replies: 2
- Views: 325
Lewis structures of compounds
Hi, in Edition 6, Ch 3 question 39, the question states: Write the complete Lewis structure for each of the following compounds: (a) ammonium chloride; (b) potassium phosphide; (c) sodium hypochlorite. Do we have to know the chemical formula of these? Also, the Lewis structures for these molecules w...
- Mon Oct 29, 2018 5:35 pm
- Forum: Bond Lengths & Energies
- Topic: Bond Lengths
- Replies: 3
- Views: 379
Re: Bond Lengths
Yes, those are just given calculations. The only thing Lavelle wanted us to get from those numbers is that resonance is the blending of structures and that the real structure is takes the average of the bond lengths.
- Mon Oct 29, 2018 5:27 pm
- Forum: Lewis Structures
- Topic: lewis structure
- Replies: 10
- Views: 1084
Re: lewis structure
Some tips I find helpful:
- The atom with the lowest ionization energy ends up in the middle for lewis structure.
- Carbon always makes four bonds
Also, just remember that every element except H, He, Li, and Be follow the octet rule.
- The atom with the lowest ionization energy ends up in the middle for lewis structure.
- Carbon always makes four bonds
Also, just remember that every element except H, He, Li, and Be follow the octet rule.
- Mon Oct 29, 2018 5:21 pm
- Forum: Student Social/Study Group
- Topic: UA Review Sessions & Practice Midterms
- Replies: 2
- Views: 260
Re: UA Review Sessions & Practice Midterms
Hi Gabby! I also think if you search up "garlic bread" you can get more midterm practice problems.
- Wed Oct 24, 2018 1:01 am
- Forum: Trends in The Periodic Table
- Topic: Test 2
- Replies: 3
- Views: 342
Re: Test 2
Hi, I was looking at the CH 2 HW problems, and after taking Test 2, just know up to question 39/41. Basically, once you reach electron configuration, you've gone too far. Just know stuff discussed in lecture (s,p,d,f and possible quantum numbers)
- Wed Oct 24, 2018 12:59 am
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: What AS information is given on Test 2
- Replies: 1
- Views: 225
Re: What AS information is given on Test 2
I would say the only important thing to know is that 400-700nm wavelength is Visible Light, and that 50/100-400nm wavelength is UV light. Also, based off the hw, probably know that Lyman series is n=1 and Balmer series is n=2.
- Wed Oct 24, 2018 12:57 am
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Spectral Lines and Series
- Replies: 3
- Views: 402
Re: Spectral Lines and Series
I think the only important thing to know here is that in each of these series, (Balmer/Lyman), the principle quantum number for the lower energy level is the same for each absorption line. That's why n=1 for all of Lyman series,etc.
- Fri Oct 19, 2018 1:36 am
- Forum: *Shrodinger Equation
- Topic: examples?
- Replies: 1
- Views: 176
Re: examples?
For the Schrodinger Wave Function, I think Lavelle just wants us to know that it's a wave function that explains where the s,p,d,f orbitals come from. You won't have to apply/use the Schrodinger equation. He may give us some s,p,d,f practice problems Friday though.
- Fri Oct 19, 2018 1:31 am
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Valence Electrons for d-block
- Replies: 2
- Views: 865
Re: Valence Electrons for d-block
The d-block can hold up to 10 electrons. This is because each orbital can contain up to two electrons, and the d subshell has 5 orbitals. I'm not sure what you mean about how you can get the number of electrons by looking at the periodic table, but hope this clarified the electrons a d subshell can ...
- Fri Oct 19, 2018 1:27 am
- Forum: DeBroglie Equation
- Topic: 6th HW 1.23 What is KeV?
- Replies: 5
- Views: 1458
Re: 6th HW 1.23 What is KeV?
eV= electric Volt
kEv is like "kilo" electric Volt so just multiply that number by 1,000.
The conversion for volts to joules is 1eV=1.602*10^-19 Joules.
kEv is like "kilo" electric Volt so just multiply that number by 1,000.
The conversion for volts to joules is 1eV=1.602*10^-19 Joules.
- Thu Oct 11, 2018 5:27 pm
- Forum: Photoelectric Effect
- Topic: Photoelectric Effect
- Replies: 2
- Views: 191
Re: Photoelectric Effect
Kinetic energy is calculated by 1/2mv^2. Use the given velocity in the problem and the mass of an electron (9.11*10^-31 kg), and substitute these values into the equation.
- Thu Oct 11, 2018 5:24 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: Finding quantum numbers [ENDORSED]
- Replies: 2
- Views: 318
Re: Finding quantum numbers [ENDORSED]
There's the principle quantum number (shell) which simply goes by n=1, 2, 3... and is the average e- distance from the nucleus. Then, there's the angular quantum number (subshell) represented by l, which ranges from 0 to (n-1). This determines the e- orbital shape. l=0 is the s subshell l=1 is the p...
- Mon Oct 08, 2018 8:12 pm
- Forum: Molarity, Solutions, Dilutions
- Topic: Molarity Question G5
- Replies: 2
- Views: 245
Re: Molarity Question G5
Hi! For G5, you would use Volume = number of moles/Molarity. This is derived from our typical Molarity=n/V equation.
Just make sure to find the number of Na moles in Na2Co3 (2 Na moles per Na2Co3), and use that number of moles in your actual equation.
Just make sure to find the number of Na moles in Na2Co3 (2 Na moles per Na2Co3), and use that number of moles in your actual equation.
- Mon Oct 08, 2018 8:07 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: Number of Orbitals
- Replies: 3
- Views: 417
Re: Number of Orbitals
Hi! I guess the best way to answer your question would be to summarize the four quantum numbers. There's the principle quantum number (shell) which simply goes by n=1, 2, 3... and is the average e- distance from the nucleus. Then, there's the angular quantum number (subshell) represented by l, which...
- Mon Oct 08, 2018 8:06 pm
- Forum: Photoelectric Effect
- Topic: Photoelectric Effect
- Replies: 6
- Views: 470
Re: Photoelectric Effect
Hi, that formula represents the excess energy of an emitted electron. It is also known as kinetic energy of the electron. One way you could solve for kinetic energy is:
E(incoming light/photon) - E(work function/energy to emit electron) = E(kinetic energy of emitted electron)
E(incoming light/photon) - E(work function/energy to emit electron) = E(kinetic energy of emitted electron)
- Sun Oct 07, 2018 7:52 pm
- Forum: Photoelectric Effect
- Topic: Energy in photoelectric effect problems
- Replies: 1
- Views: 265
Re: Energy in photoelectric effect problems
Hi! Here's a little legend to help: If problem asks- Amount of energy to remove electron = work function Number of photons= usually means amount of INCOMING light Excess energy=kinetic energy=1/2mv^2 Also, a general formula to help: Energy(photon) - Energy to remove e- = Kinetic energy of electron (...
- Sun Oct 07, 2018 7:49 pm
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Forumula Units?
- Replies: 2
- Views: 360
Re: Forumula Units?
Hi! I think the difference in units just depends on the number of elements given. When figuring out whether to use atoms/molecules in your answer, it depends on whether or not there's one element given (ex: Hydrogen) or more than one element given (H2O). I believe we refer to atoms if there is just ...
- Wed Oct 03, 2018 3:05 pm
- Forum: Student Social/Study Group
- Topic: HW Schedule?
- Replies: 7
- Views: 981
HW Schedule?
Hi Chem 14A,
So there are 6 outlines on the chem website...does outline 2 correspond with week 2 homework?
And since there are 10 weeks and only 6 outlines, are the other 4 weeks for midterms or is there another outline?
Just wanted to figure out how to find each weeks' hw. Thanks in advance!
So there are 6 outlines on the chem website...does outline 2 correspond with week 2 homework?
And since there are 10 weeks and only 6 outlines, are the other 4 weeks for midterms or is there another outline?
Just wanted to figure out how to find each weeks' hw. Thanks in advance!
- Sat Sep 29, 2018 10:55 pm
- Forum: Limiting Reactant Calculations
- Topic: Calculating Required Moles
- Replies: 2
- Views: 249
Re: Calculating Required Moles
Hey! So when calculating the required moles, think of the "4 to 5" ratio as 'how do I get from 4 to 5'. To get from 4 to 5, we multiply by 1.25. And we use that same number (1.25) to calculate the required amount. Just make sure to keep the elements in the same sequence when multiplying (i...
- Sat Sep 29, 2018 3:48 pm
- Forum: Molarity, Solutions, Dilutions
- Topic: Study Module Post-assessment Question
- Replies: 5
- Views: 375
Re: Study Module Post-assessment Question
Hi! You're definitely on the right track. :) The initial volume would be 0.02L because that's the amount you're actually bringing in to the new flask. Even though we technically started with 0.15L, that was only used to calculate the number of moles of our solute, which stays constant throughout the...
- Sat Sep 29, 2018 3:44 pm
- Forum: Molarity, Solutions, Dilutions
- Topic: Post-Module Assessment Q25
- Replies: 1
- Views: 169
Re: Post-Module Assessment Q25
Hi Christine! :) I believe you meant to ask why is Volume(initial) .02L and not .15L? And it's because we're transferring 20 ml of the solution into the new flask. We use this new amount because it's what we're actually taking into the new container. Even though we technically started with 0.15L, th...