Search found 51 matches
- Tue Mar 13, 2018 12:55 am
- Forum: Administrative Questions and Class Announcements
- Topic: Organic Chem on Final
- Replies: 9
- Views: 1443
Re: Organic Chem on Final
The ochem Dr Lavelle went over in lecture today will be on the final. He recently posted on chem community that "identifying functional groups given the structure" will be on the final and that he will go through more examples during lecture on Wednesday.
- Tue Mar 13, 2018 12:51 am
- Forum: Administrative Questions and Class Announcements
- Topic: final length
- Replies: 2
- Views: 529
Re: final length
Just like the midterm, the final will have 8 questions, but these questions will most likely have several parts and take longer to solve when compared to the questions on the midterm. However, you should have plenty of time to finish, since we'll have one more hour than we had for the midterm.
- Tue Mar 13, 2018 12:44 am
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Reaction Mechanisms
- Replies: 1
- Views: 282
Re: Reaction Mechanisms
Yes, I believe so.
- Sat Mar 10, 2018 12:33 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Test 2, Question #5
- Replies: 1
- Views: 368
Test 2, Question #5
This problems asks you to rank the following in order of increasing reducing power: a)Zn, Mn, Cr b)I 2 , Br 2 , Al I understood that the more negative the reduction potential, the greater the reducing power, and applied this logic to both parts. I wrote out the reduction potentials and ordered them ...
- Sat Mar 10, 2018 12:23 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Test 2, Question #7 [ENDORSED]
- Replies: 2
- Views: 1352
Test 2, Question #7 [ENDORSED]
What is the correct answer for this question: Calculate the standard potential for the following reaction using the standard reduction potentials on the last page of the test: Cr2O72-(aq)+14H+(aq)+12e-->2Cr(s)+7H2O(l)
- Fri Mar 09, 2018 12:55 am
- Forum: Administrative Questions and Class Announcements
- Topic: practice final?
- Replies: 4
- Views: 672
Re: practice final?
I think Lyndon will give us a packet of problems on electrochemistry and kinetics similar to the practice midterm he gave us that covered thermochemistry and thermodynamics, so if you combine these two packets it's almost like a long practice final. I think he's focusing on electrochemistry and kine...
- Fri Mar 02, 2018 1:14 am
- Forum: General Rate Laws
- Topic: Determining Order [ENDORSED]
- Replies: 8
- Views: 1063
Re: Determining Order [ENDORSED]
Additionally, example 15.2 in the textbook explains how to find the order of the reactants and the order of the overall reaction if you're given a table of experimental data.
- Fri Mar 02, 2018 1:09 am
- Forum: First Order Reactions
- Topic: problem 15.23B
- Replies: 3
- Views: 557
Re: problem 15.23B
ln[A]t-ln[A]0=-kt If you divide both sides of this equation by -1 then you get -[A]t+[A]0=kt which can be rewritten as [A]0-[A]t=kt. According to log rules, this equation can be rewritten as ln[A]0/ln[A]t=kt
- Fri Mar 02, 2018 1:06 am
- Forum: First Order Reactions
- Topic: 15.23 [ENDORSED]
- Replies: 1
- Views: 344
Re: 15.23 [ENDORSED]
The equations ln[A] 0 /ln[A] t =kt and ln[A] t -ln[A] 0 =-kt are equivalent. If you divide both sides of the second equation by -1 then you get -[A] t +[A] 0 =kt which can be rewritten as [A] 0 -[A] t =kt. According to log rules, this equation can be rewritten as ln[A] 0 /ln[A] t =kt which is the fi...
- Sat Feb 24, 2018 4:57 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: n
- Replies: 8
- Views: 917
Re: n
I believe that "n" is just the number of moles.
- Sat Feb 24, 2018 4:49 pm
- Forum: General Rate Laws
- Topic: Units for 15.3 Part B
- Replies: 4
- Views: 708
Units for 15.3 Part B
Part B asks you to determine the rate of formation for O2. The solutions manual gives the units in (mol O2).L-1.s-1. Is it wrong to leave the O2 out of the units and just leave it as mol.L-1.s-1?
- Sat Feb 24, 2018 4:37 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: units of the rate of reaction
- Replies: 7
- Views: 1037
Re: units of the rate of reaction
units for k0: mol.L-1.s-1
units for k1: s-1
units for k2: L.mol-1.s-1
units for k1: s-1
units for k2: L.mol-1.s-1
- Wed Feb 14, 2018 1:08 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Delta S(tot)
- Replies: 5
- Views: 1289
Re: Delta S(tot)
These three terms are related by deltaStotal=deltaSsystem+deltaSsurroundings.
- Wed Feb 14, 2018 1:04 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Celsius to Kelvin Clarification
- Replies: 3
- Views: 632
Re: Celsius to Kelvin Clarification
Hi! I have the same question, because sometimes the solutions manual and TAs add 273 instead of 273.15 when converting from Celsius to Kelvin and I've noticed that the answers are slightly different. However, since the equations sheet that we get for the midterm has "0 degrees Celsius=273.15 K&...
- Wed Feb 14, 2018 12:37 pm
- Forum: Phase Changes & Related Calculations
- Topic: Correct Answer For Test 1 Question 7
- Replies: 4
- Views: 728
Correct Answer For Test 1 Question 7
Question 7 on Test 1: In order to make iced-tea, a 50.0 g ice cube at 0.0 degrees Celsius is added to 250mL of tea at 20.0 degrees Celsius. What is the final temperature of the iced-tea once it has reached thermal equilibrium? Assume no heat is transferred to or from the surroundings. I solved it us...
- Tue Feb 06, 2018 5:36 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Midterm Question
- Replies: 3
- Views: 488
Re: Midterm Question
All of the material covered up until Friday, February 2 (chapters 8, 9, and 11) will be on the midterm.
- Tue Feb 06, 2018 5:34 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Bruin Cast
- Replies: 5
- Views: 881
Re: Bruin Cast
No, this class is not Bruincasted.
- Tue Feb 06, 2018 5:33 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Midterm Content Question
- Replies: 4
- Views: 688
Re: Midterm Content Question
The midterm will cover material from chapters 8, 9, and 11, so do the assigned homework problems for those chapters. Chapter 14 (electrochemistry) will not be on the midterm.
- Fri Feb 02, 2018 4:58 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Nonspontaneous processes
- Replies: 2
- Views: 478
Re: Nonspontaneous processes
Non-spontaneous processes can be done by both work and heat.
- Fri Feb 02, 2018 4:55 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Midterm
- Replies: 6
- Views: 840
Re: Midterm
According to the syllabus, you should read sections 3, 11, 12, and 13 of chapter 11. I believe that we are also responsible for knowing the rest of chapter 11, which was covered in chem 14A.
- Fri Feb 02, 2018 4:51 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gibbs Free Energy
- Replies: 3
- Views: 429
Re: Gibbs Free Energy
The textbook defines Gibbs free energy as the energy of a system that is free to do work at constant temperature and pressure. The direction of spontaneous change at constant pressure and temperature is the direction of decreasing Gibbs free energy.
- Thu Jan 25, 2018 9:25 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Chem 14A final
- Replies: 2
- Views: 402
Re: Chem 14A final
Professor Lavelle sent an email a while ago that said we can pick up our fall quarter final during week 3 from 4006 Young Hall.
- Thu Jan 25, 2018 9:18 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: 8.99
- Replies: 3
- Views: 443
Re: 8.99
The problem states that the reaction produces hydrogen gas and chloride ions , so the chemical equation can be rewritten as 2HCl (aq) +Zn (s) -->H 2(g) +Zn 2+ (aq) +2Cl - (aq) . You can now find all the enthalpies of formation needed to find the enthalpy of th...
- Thu Jan 25, 2018 3:03 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Homework Problems
- Replies: 4
- Views: 720
Re: Homework Problems
I have Mackenzie as a TA, and last week during discussion she didn't specify whether she wanted HW problems from chapter 8 or chapter 9 for week 3. On another chemistry community post Dr Lavelle commented that we can turn in any 7 problems from chapter 8 for week 3 HW, so that's what I'm doing, but ...
- Fri Jan 19, 2018 5:56 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Clarification About DeltaU=q+w
- Replies: 1
- Views: 223
Clarification About DeltaU=q+w
The following equation was given in lecture today: DeltaU=energy transferred by heating (+q) + energy transferred by compression (+w) If the system was cooled instead of heated you would just replace "heating (+q)" with "cooling (-q)" and if the system was expanded instead of com...
- Fri Jan 19, 2018 5:37 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Confusion About One of the Answers to an Example Done in Lecture
- Replies: 2
- Views: 339
Confusion About One of the Answers to an Example Done in Lecture
I was looking back through my notes and I was confused by one of the answers given to an example in lecture. Professor Lavelle went over the example "98 kJ of heat are required to raise the temperature of some ethanol by 2 degrees Celsius. What is the heat capacity for this ethanol?", and ...
- Fri Jan 19, 2018 5:11 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Mathematical Derivations of Formulas We Use
- Replies: 2
- Views: 263
Re: Mathematical Derivations of Formulas We Use
I'm pretty sure that we don't need to know how to derive the formulas we learned. I believe that Professor Lavelle just shows us the derivations so that we have a better understanding of where the formulas we use come from and how the formulas we use are related to one another, which is helpful when...
- Sun Jan 14, 2018 6:59 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Most Staple Phases
- Replies: 3
- Views: 284
Re: Most Staple Phases
C-solid (graphite), I,Br-liquid, N,O,F,Cl-gas
I believe that these are correct.
I believe that these are correct.
- Sun Jan 14, 2018 6:56 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Standard Enthalpies of Physical Change
- Replies: 2
- Views: 179
Re: Standard Enthalpies of Physical Change
I don't believe that we will have to commit any of them to memory. We've been talking about them for 2 lectures and Professor Lavelle hasn't mentioned that we have to memorize them, but I'm not 100% positive.
- Sun Jan 14, 2018 6:52 pm
- Forum: Phase Changes & Related Calculations
- Topic: Open/Closed/Isolated
- Replies: 11
- Views: 1181
Re: Open/Closed/Isolated
I would say a fish tank is a closed system.
- Sat Dec 09, 2017 3:47 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Lyndon's Week 9 WS #7 Clarification Question
- Replies: 1
- Views: 478
Lyndon's Week 9 WS #7 Clarification Question
Number 7 asks: From number 1, SO 3(g) <-->SO 2(g) +O 2(g) . The K c of the reverse reaction is 5.66*10^(-10). What are the equilibrium concentrations of all the products and reactants if you first introduce a 0.522M sample of SO 2 with a 0.633M sample of O 2 ? I have 2 questi...
- Sat Dec 09, 2017 3:36 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Lyndon's Week 9 WS #8 Part C
- Replies: 1
- Views: 293
Lyndon's Week 9 WS #8 Part C
Number 8 asks: Will the equilibrium constant K increase, decrease, or remain constant after the following changes to the exothermic reaction 4A (g) +3B (g) <-->2C (g) Part C States: The stoichiometric coefficients are doubled _________ Lyndon's answer key says that "eith...
- Tue Nov 28, 2017 2:09 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Concept Question
- Replies: 3
- Views: 555
Re: Concept Question
You would increase the yield of ammonia by removing the ammonia as it is produced in the reaction. By constantly removing the product you would prevent the reaction from reaching equilibrium and since there would then be far more reactants than products, the forward reaction would be strongly favore...
- Tue Nov 28, 2017 1:59 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 11.7
- Replies: 5
- Views: 590
Re: 11.7
@RobertEstrada At equilibrium the concentrations of the reactants and products remain constant. From flask 1 to 2 and from flask 2 to 3 the concentrations of the reactant and product change. However, from flask 3 to 4 the concentrations of the reactant and product remain the same; therefore, you kno...
- Mon Nov 20, 2017 10:25 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Constant Calculation
- Replies: 2
- Views: 419
Re: Constant Calculation
By "the opposite side of the equation" do you mean the reverse reaction? If so, yes. If you have the value of the equilibrium constant for the forward reaction, you can calculate the value of the equilibrium constant for the reverse reaction by taking the reciprocal of the equilibrium cons...
- Mon Nov 20, 2017 10:16 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Reaction arrows
- Replies: 3
- Views: 520
Re: Reaction arrows
It means that the reactants are forming the products at the same rate that the products are creating the reactants.
- Thu Nov 16, 2017 7:32 pm
- Forum: Hybridization
- Topic: Quick Hybridization Question
- Replies: 1
- Views: 213
Re: Quick Hybridization Question
Yes, you are correct.
- Thu Nov 16, 2017 7:25 pm
- Forum: Hybridization
- Topic: Extra P-Orbital
- Replies: 1
- Views: 314
Re: Extra P-Orbital
This occurs when there is sp or sp^2. For sp only one of the 3 p orbitals is hybridized along with the 1 s orbital. Therefore, there are 2 sp hybridized orbitals and 2 unhybridized p orbitals. The same goes for sp^2 except 2 of the p orbitals are hybridized along with the 1 s orbital and 1 of the p ...
- Thu Nov 09, 2017 2:51 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Test 3, Question #1
- Replies: 3
- Views: 523
Re: Test 3, Question #1
So I don't use the 1.5 anywhere?
- Thu Nov 09, 2017 2:40 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Test 3, Question #1
- Replies: 3
- Views: 523
Test 3, Question #1
How do you solve this problem? A professor is walking towards the class. An electron in his body has a speed of 1.5 +/- 0.4 m/s. What is the uncertainty in the position of the electron? I got deltax= (1.05457x10^(-34))/(2x(9.1095x10^(-31))x(2.3))= 2.5x10^(-5) m, but the correct answer is 7.35x10^(-5...
- Thu Nov 09, 2017 2:34 pm
- Forum: Limiting Reactant Calculations
- Topic: Extra Practice Problem #2
- Replies: 2
- Views: 378
Extra Practice Problem #2
How would you solve this problem:
The following two-step reaction produces hydrogen.
Step 1: CH4+H2O->CO+3H2
Step 2: CO+H2O->CO2+H2
Given 0.036g of methane (CH4) and 0.108g of water, how much hydrogen, in grams, is produced?
The following two-step reaction produces hydrogen.
Step 1: CH4+H2O->CO+3H2
Step 2: CO+H2O->CO2+H2
Given 0.036g of methane (CH4) and 0.108g of water, how much hydrogen, in grams, is produced?
- Fri Nov 03, 2017 8:14 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Angular VS Bent
- Replies: 3
- Views: 740
Re: Angular VS Bent
Yes, the terms "angular" and "bent" can be used interchangeably; they mean the same thing.
- Fri Nov 03, 2017 8:05 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Only certain central atoms have a full octet?
- Replies: 4
- Views: 745
Re: Only certain central atoms have a full octet?
@leilawilliams16 You don't always have to calculate the formal charge after drawing a lewis structure, because formal charge is only used to determine the most stable structure when molecules or ions have resonance, and therefore resonance structures. For example, CH 4 does not have resonance, so yo...
- Sun Oct 29, 2017 12:14 am
- Forum: Trends in The Periodic Table
- Topic: Effective Nuclear Charge [ENDORSED]
- Replies: 4
- Views: 1656
Re: Effective Nuclear Charge [ENDORSED]
Effective nuclear charge is the net nuclear charge after taking into account the shielding caused by other electrons in the atom. Nuclear charge and shielding are related by the equation Z(eff)=Z-S, where Z(eff) is the effective nuclear charge, Z is the atomic number, and S is the number of shieldin...
- Sun Oct 29, 2017 12:04 am
- Forum: Quantum Numbers and The H-Atom
- Topic: Ionization vs. Ionization Energy
- Replies: 2
- Views: 327
Re: Ionization vs. Ionization Energy
Ionization refers to the conversion of atoms or molecules into ions by the transfer of electrons. Ionization energy is the minimum energy required to remove an electron from the ground state of a gaseous atom, molecule, or ion.
- Sat Oct 28, 2017 11:52 pm
- Forum: Trends in The Periodic Table
- Topic: Diagonal Relationships
- Replies: 1
- Views: 307
Re: Diagonal Relationships
The textbook defines diagonal relationships as "a similarity in properties between diagonal neighbors in the main groups of the periodic table," so yes we only see diagonal relationships in main group elements.
- Sat Oct 28, 2017 11:40 pm
- Forum: DeBroglie Equation
- Topic: Test 2, Question #7 [ENDORSED]
- Replies: 5
- Views: 789
Test 2, Question #7 [ENDORSED]
Problem #7: A) An electron was ejected from the surface of an unknown metal. The ejected electron had 2.35 x 10^(-18) J of kinetic energy. The photon used to eject the electron had 4.19 x 10^(-18) J of energy. Calculate the work function (or threshold energy) of the unknown metal. B) What is the vel...
- Sat Oct 14, 2017 8:43 pm
- Forum: Properties of Light
- Topic: Units for HW Problem 1.23 [ENDORSED]
- Replies: 2
- Views: 408
Units for HW Problem 1.23 [ENDORSED]
For problem 1.23 I calculated the wavelength in nm, but when I went to check my answer with the solutions manual it had the answer in pm. How do I know which units to use for the final answer when calculating wavelength?
- Sat Oct 14, 2017 8:34 pm
- Forum: Properties of Light
- Topic: Understanding the Rydberg Formula [ENDORSED]
- Replies: 6
- Views: 1024
Understanding the Rydberg Formula [ENDORSED]
When using the Rydberg formula to calculate the frequency and you get a negative value do you omit the negative sign for the final answer because frequency can't be negative? Or do you leave the negative sign because it indicates that the electron went from a higher energy level to a lower energy le...
- Sat Oct 07, 2017 1:54 pm
- Forum: Empirical & Molecular Formulas
- Topic: Faster Method to Calculate the Molecular Formula [ENDORSED]
- Replies: 2
- Views: 500
Faster Method to Calculate the Molecular Formula [ENDORSED]
When asked to calculate the molecular formula of a compound (for this example: Compound C which is comprised of the elements A and B) and you're given the grams of C produced, the molar mass of C, the grams of A, and the grams of B, is there a faster way to calculate the molecular formula of C other...
- Sat Oct 07, 2017 1:33 pm
- Forum: Balancing Chemical Reactions
- Topic: Balancing Chemical Equations
- Replies: 5
- Views: 1427
Re: Balancing Chemical Equations
The delta symbol above the arrow in a chemical equation simply indicates that in order for the reaction to take place heat must be applied to the reactants. The delta symbol does not affect how you balance the chemical equation.