Search found 98 matches
- Sat Mar 16, 2019 2:30 am
- Forum: Student Social/Study Group
- Topic: class pictures
- Replies: 15
- Views: 3968
Re: class pictures
so motivational :’)
- Sat Mar 16, 2019 2:29 am
- Forum: Student Social/Study Group
- Topic: class pictures
- Replies: 15
- Views: 3968
- Sat Mar 16, 2019 2:26 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Standard Free Energy of Formation Units
- Replies: 2
- Views: 484
Standard Free Energy of Formation Units
In class today, Dr. Lavelle calculated the change in standard free energy of formation by using the summation method, and his deltaG standard of formation was in kJ/mol. He said that the deltaG standard of the reaction is a per mole equivalent, that is, per mole of reaction. Now I'm confused, becaus...
- Fri Mar 15, 2019 2:18 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Nernst Equation and pH
- Replies: 2
- Views: 480
Nernst Equation and pH
How can we use the Nernst Equation to calculate pH? Does it have to do something with ion-selective electrodes?
- Tue Mar 12, 2019 12:14 am
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: k prime?
- Replies: 1
- Views: 305
Re: k prime?
k is the rate constant for the forward reaction.
k' is the rate constant for the reverse reaction.
k' is the rate constant for the reverse reaction.
- Tue Mar 12, 2019 12:13 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: stability of reactants and products
- Replies: 3
- Views: 471
Re: stability of reactants and products
If K is less than 10^-3, there are more reactants at equilibrium. Therefore, the reactants are strongly favored. The reactants are more stable than the products. If K is greater than 10^3, there are more products at equilibrium. Therefore, the products are strongly favored. The products are more sta...
- Tue Mar 12, 2019 12:06 am
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Intermediates
- Replies: 3
- Views: 355
Re: Intermediates
Also, if you are only given the overall reaction rate law, I don't think you would be able to determine what the intermediates are, as intermediates and catalysts aren't included in the rate law equation.
I'm also wondering about this though, someone please verify!
I'm also wondering about this though, someone please verify!
- Sun Mar 10, 2019 10:26 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Intermediate species
- Replies: 2
- Views: 354
Re: Intermediate species
Intermediate species are formed in one of the elementary steps of the reactions then used up in another of the following elementary steps of the reaction. It is not included in the rate law.
- Sun Mar 10, 2019 10:22 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Test 2
- Replies: 12
- Views: 1055
Re: Test 2
Can someone please explain why Gibbs free energy for the combustion of a gas used to heat a BBQ at a pool party is negative? Wouldn't it require be a non-spontaneous process for the combustion to occur? This question confused me as well. After the test, I realized it was spontaneous because combust...
- Sun Mar 10, 2019 10:17 pm
- Forum: General Rate Laws
- Topic: integrals
- Replies: 8
- Views: 928
Re: integrals
Hello!
All these people gave amazing resources, just wanted to add a graphic that helped me understand it!
The derivative is shown as the slope of the graph, while the integral is shown as the area under the curve of the graph.
All these people gave amazing resources, just wanted to add a graphic that helped me understand it!
The derivative is shown as the slope of the graph, while the integral is shown as the area under the curve of the graph.
- Wed Mar 06, 2019 5:07 pm
- Forum: General Rate Laws
- Topic: Question 15.3, Sixth Edition
- Replies: 1
- Views: 275
Question 15.3, Sixth Edition
Question 15.3 reads: 15.3 In 20. s, the concentration of nitrogen dioxide, NO2, decreases from 450 mmol/L to 320 mmol/L in the reaction 2 NO2(g) -> 2 NO(g) + O2(g). (a) Determine the rate of reaction of NO2. (b) Determine the rate of formation of O2. (c) What is the unique rate of the reaction? Why ...
- Wed Mar 06, 2019 5:03 pm
- Forum: General Rate Laws
- Topic: Question 15.5, Sixth Edition
- Replies: 1
- Views: 283
Question 15.5, Sixth Edition
Hello! Question 15.5 reads: 15.5 Ethene is a minor but important component of natural gas, and its combustion has been thoroughly studied. At a certain temperature and pressure, the unique rate of the combustion reaction C2H4(g) + 3 O2(g) -> 2 CO2(g) + 2 H2O(g) is 0.44 mol/L/s (a) What is the rate a...
- Sun Mar 03, 2019 11:33 pm
- Forum: General Rate Laws
- Topic: 1st and 2nd order
- Replies: 6
- Views: 698
Re: 1st and 2nd order
I think to find the order in general, you have to do the calculations. The m and n values, which are the reaction orders with respect to each reactant, are determined experimentally. The difference between the 1st and 2nd order of the overall reaction seems to be just a difference in the sum of m an...
- Sun Mar 03, 2019 11:26 pm
- Forum: Balancing Redox Reactions
- Topic: OH-
- Replies: 5
- Views: 540
Re: OH-
This is when you're trying to find the balanced half reaction in a basic solution. This would be the last step, after balancing all atoms outside of O and H, then balancing the O's with adding H2O's to the side in which you need them. Now, we will focus on balancing the H's. You add an H2O to the si...
- Sun Mar 03, 2019 11:20 pm
- Forum: General Rate Laws
- Topic: m and n
- Replies: 2
- Views: 287
Re: m and n
Hi! Hope this helps!
- Wed Feb 20, 2019 4:57 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Gibb's free energy Units
- Replies: 4
- Views: 380
Re: Gibb's free energy Units
I don't think it matters as long as you keep your units consistent throughout and don't add kJ to J.
- Wed Feb 20, 2019 4:56 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Galvanic Cells
- Replies: 7
- Views: 630
Galvanic Cells
Hello! I can't seem to wrap my head around the concept of galvanic cells. In class today, we learned that galvanic cells change chemical energy, but what exactly is a galvanic cell? When "cells" are mentioned, am I suppose to think of biological cells or just pockets of space? I'm having t...
- Wed Feb 20, 2019 4:52 pm
- Forum: Balancing Redox Reactions
- Topic: Salt Bridge
- Replies: 4
- Views: 418
Re: Salt Bridge
The purpose of a salt bridge is to maintain a change balance, since electrons are moving from one side to another. Without the salt bridge, electron transfer from one "reaction beaker" to another will stop due to charge buildup. Adding a salt bridge (or a porous disk) will help the solutio...
- Sat Feb 16, 2019 5:45 am
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: ΔS=q/t
- Replies: 8
- Views: 901
Re: ΔS=q/t
Why can you only calculate delta S, when the q for the reaction is reversible? The reaction does not have to be reversible in order to calculate delta S in this way. They just use q rev as a convention, but since delta S is a state function, the pathway doesn’t matter (therefore, it doesn’t matter ...
- Sat Feb 16, 2019 5:42 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: At Equilibrium G
- Replies: 6
- Views: 656
Re: At Equilibrium G
Parth Mungra wrote:If K=0, then the reaction is neither spontaneous nor nonspontaneous
This sounds interesting! I’ve never heard of a case where K=0, can someone elaborate on this?
- Sat Feb 16, 2019 5:41 am
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Midterm Grades
- Replies: 35
- Views: 2633
Re: Midterm Grades
Last quarter it took around a week!
- Thu Feb 07, 2019 2:46 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Cv vs. Cp
- Replies: 1
- Views: 392
Cv vs. Cp
In the constants and equations sheet, the values for various specific heats of water are listed as: Specific heat capacity ice = 2.03 J.°C-1.g-1 Specific heat capacity water liquid = 4.184 J.°C-1.g-1 Specific heat capacity water vapor = 2.01 J.°C-1.g-1 Molar heat capacity water liquid = 75.29 J·K-1·...
- Wed Feb 06, 2019 1:14 am
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Reversible vs. Irreversible
- Replies: 1
- Views: 231
Reversible vs. Irreversible
What are the main differences between reversible and irreversible expansion of an ideal gas? Is it just that reversible is with changing pressure and irreversible is with constant pressure?
What about temperature?
What about temperature?
- Wed Feb 06, 2019 12:42 am
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Equation help!
- Replies: 1
- Views: 228
Equation help!
If we use W = -P * deltaV for when it's under constant pressure, what formula do we use when it's not?
- Thu Jan 31, 2019 4:03 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: What do do when moles are given
- Replies: 5
- Views: 470
Re: What do do when moles are given
Kobe_Wright wrote:when a problem says there is 3 moles or 6 moles of a certain molecule do we just use that value to find the concentration or do we put the moles given in the exponent of our equilibrium constant equation?
I think we use those values of moles to find Q and then compare it to equilibrium.
- Thu Jan 31, 2019 4:02 pm
- Forum: Ideal Gases
- Topic: atm vs. bar?
- Replies: 25
- Views: 2819
Re: atm vs. bar?
Karina Jiayu Xu 4E wrote:On the test I used bar and it was fine
My TA said she would’ve accepted both atm and bar on the test, but I’ve also heard that atm is more standard.
- Wed Jan 30, 2019 11:46 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Sixth Edition Question 8.63
- Replies: 1
- Views: 176
Re: Sixth Edition Question 8.63
Also, I thought standard reaction enthalpy was per mol, so why didn't they divide by two at the end, since there's two moles of HNO3?
- Wed Jan 30, 2019 11:45 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Sixth Edition Question 8.63
- Replies: 1
- Views: 176
Sixth Edition Question 8.63
Just regarding 8.63 a), why is the standard enthalpy of formation for NO positive and not negative? The solutions manual said it was +90.25 kJ/mol, but I thought that since it was a product, it would have negative enthalpy?
- Fri Jan 25, 2019 2:26 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Autoprotolysis
- Replies: 3
- Views: 423
Re: Autoprotolysis
If a weak acid deprotonates and releases less than 10^-7 M of hydronium, then you would consider autoprotolysis. This is because if you ignore autolysis and calculate pH of an acid that creates 10^-9 M hydronium, then the pH would be basic. This would not make sense since there is an acid in the so...
- Wed Jan 23, 2019 9:09 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Kw - applies to solutions other than 100% water?
- Replies: 3
- Views: 317
Kw - applies to solutions other than 100% water?
For 12.21 in the Sixth Edition, we are suppose to solve for either [H3O+] or [OH-] using the Kw relationship, [H3O+][OH-] = 10^-14. Can we use this relationship to solutions other than 100% water? I thought that Kw was only for water but it doesn't say in the question whether the solution is water-b...
- Wed Jan 23, 2019 8:54 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Adding a Liquid or Solid to an Equation
- Replies: 2
- Views: 415
Adding a Liquid or Solid to an Equation
Does adding a liquid or solid to a system evoke a shift to restore equilibrium? I thought it wouldn't, especially if you add more of the solvent, since there is already so much of it. However, the Post-Test contradicts my thoughts, help?
See the attached picture for what I'm talking about.
See the attached picture for what I'm talking about.
- Sat Jan 19, 2019 2:33 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Extracting the Equation from a Given question
- Replies: 1
- Views: 179
Extracting the Equation from a Given question
Hello! I find myself having trouble writing out my own chemical equation for those questions in which you are only given some initial information. How do you know what combines with what? For instance, the example we went over in class on Week 2, Lecture 3 (1/18/19), the given information was: Given...
- Sat Jan 19, 2019 2:23 am
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Understanding Q
- Replies: 9
- Views: 721
Re: Understanding Q
Adding onto what they all said, I’d like to relate this to Le Chatelier’s Principle. When pressure/volume/concentration change, it is Q that changes, not K. However, when temperature changes, then K changes.
- Thu Jan 17, 2019 1:54 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Sixth Edition Question 11.87
- Replies: 2
- Views: 247
Sixth Edition Question 11.87
Hello!
Question 11.87 is about the dissociation of a diatomic molecule, Xs 2x.
How do we know this reaction is endothermic?
Question 11.87 is about the dissociation of a diatomic molecule, Xs 2x.
How do we know this reaction is endothermic?
- Fri Jan 11, 2019 12:25 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: ICE Table Help
- Replies: 3
- Views: 232
ICE Table Help
Hello! In the example given on Wednesday, we did the ICE table on ATP hydrolysis. It was given that the initial molarity of ATP in healthy muscle tissue is 8.435 x 10^-3. We determined that the change in molarity was - 8.435 x 10^-3. I thought that if we subtracted the change from the initial, we wo...
- Fri Jan 11, 2019 12:20 pm
- Forum: Ideal Gases
- Topic: Q and K [ENDORSED]
- Replies: 35
- Views: 3010
Re: Q and K [ENDORSED]
K is found using concentrations at equilibrium, BUT to calculate Q do we just use the initial concentrations or concentrations at any given time? Yes. Q can be calculated at any time in the reaction, and then you would compare it to the given equilibrium constant, K, to determine if the reaction is...
- Fri Jan 11, 2019 12:17 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Activity in reactions
- Replies: 2
- Views: 157
Re: Activity in reactions
Pure substances, which are solids and liquids, are omitted from equilibrium constant calculations. This is because the molar concentration of pure substances does not change in a reaction. This does make the calculation for K an approximation, as there may actually be a reaction going on with the so...
- Sun Dec 09, 2018 12:17 am
- Forum: Naming
- Topic: Carbonato and Sulfato - Bidentate?
- Replies: 1
- Views: 313
Carbonato and Sulfato - Bidentate?
Carbonato and sulfato both seem to be bidentate because they both have single bonded oxygens, but the textbook doesn't say they are polydentate... Any insight?
- Sat Dec 08, 2018 1:30 am
- Forum: Polyprotic Acids & Bases
- Topic: Strong Acids - HClO4 and HClO3
- Replies: 1
- Views: 2940
Strong Acids - HClO4 and HClO3
Chlorate is ClO3 -1, and adding a Hydrogen would make it neutral, so I understand that HClO3 should be neutral.
Why is perchloric acid (HClO4) neutral and not negatively charged since there's another oxygen on it compared to neutral HClO3?
Why is perchloric acid (HClO4) neutral and not negatively charged since there's another oxygen on it compared to neutral HClO3?
- Fri Dec 07, 2018 12:14 pm
- Forum: Administrative Questions and Class Announcements
- Topic: FINAL PRACTICE - Lyndon's Churro Review Session [ENDORSED]
- Replies: 118
- Views: 20763
- Wed Dec 05, 2018 8:50 pm
- Forum: Naming
- Topic: Coordination Compound vs. Coordination Complex
- Replies: 1
- Views: 167
Re: Coordination Compound vs. Coordination Complex
Nevermind. I looked it up in the textbook and it was just a subtle difference: Coordination compounds include what is inside and outside the brackets. They do not have a net charge, as whatever is inside the coordination sphere (surrounded by brackets) cancels out with whatever is outside the bracke...
- Wed Dec 05, 2018 8:45 pm
- Forum: Naming
- Topic: Coordination Compound vs. Coordination Complex
- Replies: 1
- Views: 167
Coordination Compound vs. Coordination Complex
What's the difference between a coordination compound and a coordination complex? Does this have to do anything with the charges?
- Tue Dec 04, 2018 9:39 pm
- Forum: Lewis Structures
- Topic: Lewis Structure bonds
- Replies: 4
- Views: 410
Re: Lewis Structure bonds
Look at the formal charge of the atoms involved in the Lewis structure. Formal charges should add up to 0, unless there is a charge indicated on the molecular formula, and it is more favorable to have a formal charge on the terminal atoms.
- Sat Dec 01, 2018 12:41 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Dissociation energy
- Replies: 7
- Views: 610
Re: Dissociation energy
Dissociation energy is the energy required to break a covalent bond. I believe that dissociation energy is positive because a positive change in energy is required to break a bond (gains energy) while a negative change in energy is required to make a bond (loses energy).
- Tue Nov 27, 2018 12:20 am
- Forum: Dipole Moments
- Topic: Problem 6.1
- Replies: 1
- Views: 284
Problem 6.1
6.1 Identify the kinds of intermolecular forces that might arise between molecules of each of the following substances: (a) NH2OH; (b) CBr4; (c) H2SeO4; (d) SO2.
For SO2, why can it create dipole-dipole interactions between molecules of each? I thought it was polar. Is it because of the lone pairs?
For SO2, why can it create dipole-dipole interactions between molecules of each? I thought it was polar. Is it because of the lone pairs?
- Mon Nov 26, 2018 10:31 pm
- Forum: Lewis Structures
- Topic: Question 3.45
- Replies: 4
- Views: 302
Re: Question 3.45
Rachel Yoo 3E wrote:Nitrogen is in row 2 which means it cant disobey the octet rule. By adding a double bond to chlorine, it would make nitrogen not follow this rule.
Thank you! Makes total sense now.
- Mon Nov 26, 2018 10:24 pm
- Forum: Lewis Structures
- Topic: Question 3.45
- Replies: 4
- Views: 302
Question 3.45
Why does the lewis structure for ClNO2 have only one double bond? Can't it have two and have zero formal charge on all of the bonds?
- Thu Nov 22, 2018 10:46 pm
- Forum: Hybridization
- Topic: Octet Expansion and d-Orbitals
- Replies: 8
- Views: 780
Re: Octet Expansion and d-Orbitals
So is any element in the first 3 groups without a d-orbital in its shell unable to fulfill the octet rule? Under my current understanding, I believe any element in the first three groups don't have to meet the octet rule of maximum 8 electrons, it can exceed the octet rule since it has access to th...
- Thu Nov 22, 2018 5:11 am
- Forum: Hybridization
- Topic: Question 4.95
- Replies: 1
- Views: 824
Question 4.95
Attached is the solution to question 4.95, which asks: Consider the bonding in CH2-CHCHO. (a) Draw the most important Lewis structure. Include all nonzero formal charges. (b) Identify the composition of the bonds and the hybridization of each lone pair—for example, by writing sigma(H1s,C2sp2). My qu...
- Thu Nov 22, 2018 5:05 am
- Forum: Hybridization
- Topic: Sixth Edition, Example 4.6
- Replies: 2
- Views: 278
Sixth Edition, Example 4.6
In this example, it shows the image of how a the bonds form.
Why is it C sp2 instead of C 2sp2? As well as O sp2 instead of O 2sp2? Aren't oxygen and Carbon in the second row?
Thanks!
Why is it C sp2 instead of C 2sp2? As well as O sp2 instead of O 2sp2? Aren't oxygen and Carbon in the second row?
Thanks!
- Thu Nov 22, 2018 4:26 am
- Forum: Hybridization
- Topic: Octet Expansion and d-Orbitals
- Replies: 8
- Views: 780
Octet Expansion and d-Orbitals
With regards to the dsp 3 hybridized orbitals as well as the d 2 sp 3 hybridized orbitals, octet expansion involves the d-orbitals, which starts at phosphorus. Why does octet expansion begin at phosphorus? I thought anything in the third row could have an expanded octet; why not Aluminum or Silicon?...
- Thu Nov 22, 2018 4:22 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bent - Lone Pairs
- Replies: 8
- Views: 926
Bent - Lone Pairs
For the bent shape, does this include instances where there's one lone pair, as well as instances including two lone pairs?
Thank you!
Thank you!
- Thu Nov 22, 2018 4:20 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Sixth Edition. Question 4.109
- Replies: 4
- Views: 1061
Sixth Edition. Question 4.109
Question 4.109 is: 4.109 Estimate the bond angles marked with arcs and lowercase letters in peroxyacetylnitrate, an eye irritant in smog. It adds an image of the molecule, which is attached. But why is angle b around 109.5 degrees? It only has two regions of electron density, so I expected it to be ...
- Tue Nov 20, 2018 5:29 pm
- Forum: Lewis Structures
- Topic: Lewis Structure for NO3-
- Replies: 3
- Views: 2960
Re: Lewis Structure for NO3-
I agree with 705 and Clarissa that the reason that the bond lengths are the same is because of the resonance structures. This is due to the delocalization of electrons, creating a single-double bond hybrid, so all the bond lengths are actually the same.
- Tue Nov 20, 2018 5:00 pm
- Forum: Hybridization
- Topic: Test 3
- Replies: 8
- Views: 798
Re: Test 3
It will include hybridization, which is the focus of the UA's peer learning sessions this week.
- Tue Nov 20, 2018 4:57 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Hund's rule vs Pauli's
- Replies: 3
- Views: 1078
Re: Hund's rule vs Pauli's
Hello!
I like to associate Pauli with the word "pair" since they both start with P! That's just an extra thing that helps me remember that Pauli Exclusion Principle is about how electrons that are spin paired must be of opposite spin.
Hope this helped!
I like to associate Pauli with the word "pair" since they both start with P! That's just an extra thing that helps me remember that Pauli Exclusion Principle is about how electrons that are spin paired must be of opposite spin.
Hope this helped!
- Sun Nov 18, 2018 2:45 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Square Planar vs Tetrahedral
- Replies: 8
- Views: 2361
Re: Square Planar vs Tetrahedral
Hello! Square planar is with regards to molecular geometry/arrangement, that is, it considers the lone pairs and how their repulsion affect the bond angle. However, tetrahedral is with regards to the shape of the molecule, only considering the atoms and not the lone pairs.
- Sun Nov 18, 2018 2:42 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: lone pairs
- Replies: 11
- Views: 826
Re: lone pairs
I also agree that the lone pairs affect the angular geometry of the molecule. This is because of electron repulsion. However, lone pairs only are accounted for in the geometry of the molecule. The atoms in the molecule are what determines its shape.
- Thu Nov 15, 2018 12:40 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: See-Saw Shape
- Replies: 3
- Views: 499
See-Saw Shape
Hello!
Can someone explain what the see-saw shape is please? Is it another name for something in our notes? I know it involves a lone pair, but I cannot conceptualize how it looks like a see-saw.
Thanks!
Can someone explain what the see-saw shape is please? Is it another name for something in our notes? I know it involves a lone pair, but I cannot conceptualize how it looks like a see-saw.
Thanks!
- Fri Nov 09, 2018 2:00 am
- Forum: Ionic & Covalent Bonds
- Topic: Polarizability
- Replies: 9
- Views: 839
Re: Polarizability
Polarizability is a measure of how easy an electron cloud is distorted by an electric field. The electron distortion is proportional to the polarizability of the electron.
- Fri Nov 09, 2018 1:55 am
- Forum: Bond Lengths & Energies
- Topic: MIDTERM Bond Length Question
- Replies: 15
- Views: 1524
Re: MIDTERM Bond Length Question
I assumed that both the bond-lengths were the same, that they were each single-double bond hybrids.
Therefore, I thought it was 130.
Therefore, I thought it was 130.
- Fri Nov 09, 2018 1:51 am
- Forum: Student Social/Study Group
- Topic: Sig Figs on Midterm
- Replies: 13
- Views: 1524
Re: Sig Figs on Midterm
I think it may be strict on the midterm. On the constants and formula page, it says 2 pts. for sig figs.
- Sat Nov 03, 2018 2:22 am
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: En Equation - Why the Negative?
- Replies: 2
- Views: 976
En Equation - Why the Negative?
Hello!
I thought energy could only be positive, why does the equation for energy at a specific principle quantum number have a negative sign in front of it? Is this applied to find change in energy?
En = -hR/n^2
I thought energy could only be positive, why does the equation for energy at a specific principle quantum number have a negative sign in front of it? Is this applied to find change in energy?
En = -hR/n^2
- Sat Nov 03, 2018 1:54 am
- Forum: Properties of Electrons
- Topic: Isoelectronicity
- Replies: 3
- Views: 1008
Re: Isoelectronicity
Isoelectronicity is the phenomenon when two different atoms/ions have the same number of electrons. For example, Na and Mg+ are isoelectronic, since Na and Mg+ both have 11 electrons. (Mg has 12 electrons in its neutral state, then it loses an electron, having 11). Isoelectronicity is an important c...
- Sat Nov 03, 2018 1:47 am
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Cu and Cr electron configuration exceptions
- Replies: 1
- Views: 9566
Re: Cu and Cr electron configuration exceptions
Copper and Chromium are exceptions to the common electron configuration methods because they are one electron away from reaching a more stable state (a half-filled 3d subshell for Chromium with 5 electrons under Hund's Rule, and a filled 3d subshell with 10 electrons under the Pauli Exclusion Princi...
- Sat Nov 03, 2018 1:40 am
- Forum: Trends in The Periodic Table
- Topic: Ionic Radius
- Replies: 3
- Views: 320
Re: Ionic Radius
Hi, Stevin! I recall someone said that this is because of the proton to electron ratio. I don't understand it in full, but this is along the lines of what I remember... Ca2+ has 22 electrons and 20 protons, while Na+ has 10 electrons and 11 protons. I guess since calcium as a cation has the most cha...
- Wed Oct 31, 2018 7:45 pm
- Forum: Ionic & Covalent Bonds
- Topic: Problem 3.5
- Replies: 1
- Views: 133
Problem 3.5
Hello! Here is Problem 3.5: 3.5 Give the ground-state electron confi guration expected for each of the following ions: (a) Cu+; (b) Bi3+; (c) Ga3+; (d) Tl3+. Regarding part a, for Cu+, why does the electron configuration go one more element to the right on the periodic table, when it loses one elect...
- Tue Oct 30, 2018 2:25 am
- Forum: General Science Questions
- Topic: Midterm Location
- Replies: 1
- Views: 280
Midterm Location
Does anyone know where the midterm is located? Thanks!
- Sat Oct 27, 2018 12:49 pm
- Forum: Student Social/Study Group
- Topic: Studying
- Replies: 7
- Views: 730
Re: Studying
The step-up sessions and workshops are really helpful! Look up the practice workshops’ worksheets on chemistry community.
- Sat Oct 27, 2018 12:47 pm
- Forum: Einstein Equation
- Topic: E=hv [ENDORSED]
- Replies: 52
- Views: 18033
Re: E=hv [ENDORSED]
E in this case is E(photon). The work function is the energy required to eject an electron in a 1:1 photon:electron interaction.
- Tue Oct 23, 2018 4:28 pm
- Forum: Properties of Light
- Topic: EM Energy Spectrum
- Replies: 4
- Views: 404
EM Energy Spectrum
Do we have to know the quantities of wavelengths for each category of light?
Such as gamma = 10^-12 m, and Radio waves = 10^3 m?
Thanks!
Such as gamma = 10^-12 m, and Radio waves = 10^3 m?
Thanks!
- Mon Oct 22, 2018 1:05 am
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Rydberg's Equation
- Replies: 1
- Views: 179
Rydberg's Equation
I remember Dr. Lavelle saying something about not wanting us to use Rydberg's equation but to use another one in place of that. Can someone clarify or explain this?
Thank you!
Thank you!
- Sat Oct 20, 2018 6:08 pm
- Forum: Properties of Light
- Topic: Grades
- Replies: 7
- Views: 628
Re: Grades
Hello!
I checked on CCLE and MyUCLA, and grades are not on there. I am also not sure where to access this information.
I checked on CCLE and MyUCLA, and grades are not on there. I am also not sure where to access this information.
- Sat Oct 20, 2018 5:55 pm
- Forum: Properties of Light
- Topic: Wavelengths and frequencies
- Replies: 10
- Views: 643
Re: Wavelengths and frequencies
I think it would be useful to remember the order of the wavelength classifications from largest to smallest energy, but not necessary to remember the exact length of each category, such as 10^-12
- Fri Oct 19, 2018 10:48 am
- Forum: Einstein Equation
- Topic: Numbers to memorize [ENDORSED]
- Replies: 37
- Views: 3988
Re: Numbers to memorize [ENDORSED]
Hello! I agree that there will be a formula sheet in the front. Common equations, such as E=hv and c= lambda•v will be given. However, derivations of common equations that are necessary for some problems, such as E = hc/lambda will have to be determined by the test taker. All constants should be on ...
- Fri Oct 19, 2018 10:43 am
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Problem 1D.9
- Replies: 3
- Views: 382
Re: Problem 1D.9
Hello! My TA said that if material is not covered in class, we will not be held accountable for it and it is not on the test.
- Mon Oct 15, 2018 1:07 am
- Forum: General Science Questions
- Topic: BruinCast [ENDORSED]
- Replies: 4
- Views: 726
BruinCast [ENDORSED]
Hello!
Does Dr. Lavelle offer Bruincast/podcast lectures? If so, where can I find them?
I know he has the audio/video modules, but that only goes to the Heisenberg Uncertainty Principle.
Thanks!
Does Dr. Lavelle offer Bruincast/podcast lectures? If so, where can I find them?
I know he has the audio/video modules, but that only goes to the Heisenberg Uncertainty Principle.
Thanks!
- Mon Oct 15, 2018 12:59 am
- Forum: Properties of Light
- Topic: What does v stand for?
- Replies: 1
- Views: 1140
What does v stand for?
Under the Properties of Light slide, it said that "fields oscillate in direction & strength with frequency, v, (per second)..." but under the Properties of Electrons slide, it said that wavelength = h/(mass x velocity).
Does v stand for velocity or frequency?
Thank you in advance!
Does v stand for velocity or frequency?
Thank you in advance!
- Wed Oct 10, 2018 9:27 pm
- Forum: SI Units, Unit Conversions
- Topic: Scientific Notation
- Replies: 7
- Views: 629
Re: Scientific Notation
It doesn't matter which notation you use, as long as you get the number of significant figures correctly. Hope this helped!
- Wed Oct 10, 2018 9:25 pm
- Forum: Empirical & Molecular Formulas
- Topic: Chemical Formula Element Order
- Replies: 5
- Views: 637
Re: Chemical Formula Element Order
Hello! I asked Dr. Lavelle this question today in office hours, and he said for now, not to worry about it. Conventionally, for organic molecules, it usually goes in the order of C H O, but if it has lesser known elements, like Cl or Br, it can be in any order. Some order the elements in descending ...
- Wed Oct 10, 2018 9:23 pm
- Forum: Einstein Equation
- Topic: sig fig numbers
- Replies: 4
- Views: 303
Re: sig fig numbers
Hi! It depends what computations you are doing in the problem. Most problems require multiplication and/or division, in which case your answer should include the least number of significant figures from the problem. If the problem only requires addition and/or subtraction, then your answer should in...
- Sun Oct 07, 2018 11:30 pm
- Forum: Limiting Reactant Calculations
- Topic: Question M3
- Replies: 3
- Views: 318
Re: Question M3
Never mind regarding this question. There was only one reactant.
But in other cases, would they give you the masses of both/all the reactants to determine which one is limiting? Thank you!
But in other cases, would they give you the masses of both/all the reactants to determine which one is limiting? Thank you!
- Sun Oct 07, 2018 11:29 pm
- Forum: Limiting Reactant Calculations
- Topic: Question M3
- Replies: 3
- Views: 318
Question M3
Questions M3 reads: When limestone, which is principally CaCO3, is heated, carbon dioxide and quicklime, CaO, are produced by the reaction CaCO3 (s) -> CaO (s) + CO2 (g). If 17.5 g of CO2 is produced from the thermal decomposition of 42.73 g of CaCO3, what is the percentage yield of the reaction? Si...
- Sun Oct 07, 2018 10:53 pm
- Forum: Empirical & Molecular Formulas
- Topic: Question L39
- Replies: 2
- Views: 367
Question L39
Hello! Question L39 reads: A 1.50 g sample of metallic tin was placed in a 26.45 g crucible and heated until all the tin had reacted with the oxygen in the air to form an oxide. The crucible and product together were found to weigh 28.35 g. A) what is the empirical formula of the oxide? B) write the...
- Sun Oct 07, 2018 10:47 pm
- Forum: Balancing Chemical Reactions
- Topic: Where to start [ENDORSED]
- Replies: 10
- Views: 1356
Re: Where to start [ENDORSED]
Hello!
I also start balancing with whatever element occurs the least. Sometimes, I leave the ones that are on their own (like O2) for the end, so I can just balance it accordingly with the other side, and it won’t affect any other element.
Hope this helped!
I also start balancing with whatever element occurs the least. Sometimes, I leave the ones that are on their own (like O2) for the end, so I can just balance it accordingly with the other side, and it won’t affect any other element.
Hope this helped!
- Sun Oct 07, 2018 10:44 pm
- Forum: Empirical & Molecular Formulas
- Topic: when to multiply empirical formula [ENDORSED]
- Replies: 9
- Views: 4441
Re: when to multiply empirical formula [ENDORSED]
If you are at 3.5, you can multiply by 2 to get 7! Hope this helps.
- Wed Oct 03, 2018 8:06 pm
- Forum: Empirical & Molecular Formulas
- Topic: Multiplying to get an integer in the empirical formula
- Replies: 4
- Views: 801
Multiplying to get an integer in the empirical formula
What’s the threshold of rounding up and down when calculating the empirical formula versus multiplying to get a whole number?
Is it 0.75 and up, round up; 0.25 and down, round down? When do we know to multiply to get a whole number for the empirical formula?
Is it 0.75 and up, round up; 0.25 and down, round down? When do we know to multiply to get a whole number for the empirical formula?
- Wed Oct 03, 2018 8:01 pm
- Forum: General Science Questions
- Topic: Turning in Homework
- Replies: 4
- Views: 474
Re: Turning in Homework
Abby-Hile-1I wrote:Is the homework due in discussion this week? For some reason I thought he said something about turning it in on Friday.
Hi! For this week, we will be turning in the homework in class. Moving forward, it’ll be in discussion.
- Wed Oct 03, 2018 12:43 am
- Forum: General Science Questions
- Topic: Turning in Homework
- Replies: 4
- Views: 474
Turning in Homework
Hello! Does anyone know when the homework we turn in is given back to us, if at all? I did it on a separate piece of paper, but I want to start doing it in my notebook. However, if it turns out that the homework is collected and not given back, I'll just keep doing it on loose leaf. Thank you in adv...
- Tue Oct 02, 2018 10:21 pm
- Forum: SI Units, Unit Conversions
- Topic: FREE Textbook
- Replies: 2
- Views: 368
Re: FREE Textbook
Hello! Would I be able to take it?
- Tue Oct 02, 2018 10:21 pm
- Forum: Empirical & Molecular Formulas
- Topic: Resources given on tests [ENDORSED]
- Replies: 3
- Views: 463
Re: Resources given on tests [ENDORSED]
I'm not sure exactly which periodic table we will be given, but Dr. Lavelle did say that we will surely be given a periodic table. Have a wonderful day!
- Tue Oct 02, 2018 10:19 pm
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Avogadro's Number
- Replies: 2
- Views: 287
Re: Avogadro's Number
Hello! Here's a link to an old post on Chemistry Community that I found helpful when I was wondering this too. https://lavelle.chem.ucla.edu/forum/viewtopic.php?t=1925#p3890 Basically, @Chem_Mod said that we used carbon because it set a common standard for everyone to work with because if different ...
- Tue Oct 02, 2018 10:14 pm
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Question E1(6th Edition)
- Replies: 7
- Views: 678
Re: Question E1(6th Edition)
Can we leave our answer in pm, or do we have to convert it to km? Hi, Nicolette! Even though the textbook answer is in kilometers, I would write my answer in meters, since meters is the standard SI unit for length. In this case though, I assume they converted all the way to kilometers since it was ...
- Sun Sep 30, 2018 10:33 pm
- Forum: Empirical & Molecular Formulas
- Topic: Formula Units vs. Molecules [ENDORSED]
- Replies: 1
- Views: 366
Formula Units vs. Molecules [ENDORSED]
Hello!
With regards to question E21, it asks for the answer in molecules and formula units. What is the difference between molecules and formula units?
Thank you!
With regards to question E21, it asks for the answer in molecules and formula units. What is the difference between molecules and formula units?
Thank you!
- Sun Sep 30, 2018 7:04 pm
- Forum: Empirical & Molecular Formulas
- Topic: Module Pre-Assessment Scoring [ENDORSED]
- Replies: 1
- Views: 180
Module Pre-Assessment Scoring [ENDORSED]
Hello!
I just completed the pre-assessment for the first module: Empirical and Molecular Formulas. Is there any way I can access my score to gauge how well I did on it?
Thank you in advance!
I just completed the pre-assessment for the first module: Empirical and Molecular Formulas. Is there any way I can access my score to gauge how well I did on it?
Thank you in advance!
- Sat Sep 29, 2018 5:35 pm
- Forum: Molarity, Solutions, Dilutions
- Topic: Question E16 - Transition Metal Charge
- Replies: 4
- Views: 367
Question E16 - Transition Metal Charge
Hello! I’m working on question E16, which asks to find the chloride of a mystery metal. The mystery metal is determined by using its molar mass, which we calculate. Anyways, the mystery metal turned out to be Ag. Since silver is a transition metal, how do we determine its charge? Do we just assume t...
- Fri Sep 28, 2018 7:30 pm
- Forum: SI Units, Unit Conversions
- Topic: Standard SI Unit, Question E1
- Replies: 3
- Views: 448
Standard SI Unit, Question E1
Hello! In my chemistry discussion yesterday, my TA did question E1 with us, which reads: The field of nanotechnology offers some intriguing possibilities, such as the creation of fibers one atom wide. Suppose you were able to string together 1.00 mol Ag atoms, each of radius 144 pm, into one of thes...
- Fri Sep 28, 2018 7:10 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Solutions Manual
- Replies: 9
- Views: 1745
Re: Solutions Manual
I think solutions manual is not mandatory; however, it is highly recommended. It can be used to check your homework as well as trace back answers if you don't understand them. I believe this is because the textbook (sixth edition) only provides answers to the odd-numbered exercises, which starts on ...