## Search found 63 matches

Wed Mar 13, 2019 9:07 pm
Forum: Administrative Questions and Class Announcements
Replies: 7
Views: 383

I would try to do it before the final because I remember last quarter we couldn't make posts after it.
Sun Mar 03, 2019 8:27 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: concentration cell
Replies: 2
Views: 72

### Re: concentration cell

Concentration cells are galvanic cells with same components (AgNO3 the example Lavelle gave us) but it only works when concentrations are different. The standard cell potential is always zero because the conditions of standard cell potential requires the concentrations to be at 1M, so the voltage is...
Tue Feb 26, 2019 9:09 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Lyndon Review number 8/9?
Replies: 1
Views: 70

### Lyndon Review number 8/9?

Does anyone know why “A reaction with a negative standard reduction potential favors oxidation of the reactant” is True? What is the “reactant” in this case.

And also why for “A reactant in a reaction with a very positive standard reduction potential is a powerful reducing agent” is False?
Mon Feb 25, 2019 10:29 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: salt bridge
Replies: 1
Views: 57

### Re: salt bridge

Since the electrons flow from anode to cathode, the anode side of the reaction will become more positive and there will be a build up of negative charge in the cathode which slows the reaction/flow of e-. To balance the charges and allow the reaction to keep continuing there has to be a salt bridge/...
Mon Feb 25, 2019 10:15 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Stability and free energy
Replies: 1
Views: 71

### Re: Stability and free energy

I don't understand the second part of your question but when free energy (deltaG) is negative, the reaction is spontaneous therefore the reaction's products are stable and will occur without an input of energy. Therefore a reaction with a positive free energy change means the reaction requires energ...
Mon Feb 25, 2019 8:44 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Salt Bridge
Replies: 2
Views: 96

### Re: Salt Bridge

Salt bridge or porous disc to allow negative ions to flow back to the anode side or else the reaction will stop.
Sun Feb 24, 2019 10:44 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Wmax and -W
Replies: 2
Views: 74

### Re: Wmax and -W

because the negative is in front of the charge.
Sun Feb 24, 2019 10:43 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell diagram
Replies: 4
Views: 95

### Re: Cell diagram

Most of the time anode is left and cathode is right.
Thu Feb 21, 2019 11:14 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Free Energy and Pressure
Replies: 1
Views: 87

### Re: Free Energy and Pressure

Because enthalpy is heat at constant pressure. You can only calculate deltaG when the reaction occurs at constant pressure and temperature.
Thu Feb 21, 2019 11:08 pm
Forum: Balancing Redox Reactions
Topic: redox reactions
Replies: 3
Views: 91

### Re: redox reactions

Another tip is to figure out the oxidation numbers of each molecules first and then figure out which one loses/gains electrons with OIL RIG acronym. Oxidation numbers are basically the charges of an atom, ex) H is always 1+ Oxygen is usually 2- etc, the oxidation number of an ion is its charge... etc.
Thu Feb 21, 2019 11:05 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Free Energy and Work Relationship
Replies: 2
Views: 87

### Re: Free Energy and Work Relationship

Gibbs free energy is defined as the energy available to do useful work.
Thu Feb 21, 2019 11:04 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Explanation
Replies: 3
Views: 85

### Re: Explanation

A galvanic cell is basically the diagram that Lavelle showed in lecture where the reactants are divided in two containers and the cathode pulls electrons from the anode due to cell potential.
Thu Feb 21, 2019 10:59 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Delta G = 0
Replies: 4
Views: 114

### Re: Delta G = 0

Yes!
Wed Feb 20, 2019 10:58 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 6th edition 9.67
Replies: 3
Views: 108

### Re: 6th edition 9.67

After you find out what temperature it is to make deltaG zero, the following assumption is made that for every temperature above the "equilibrium" temperature, your delta G will therefore be negative.
Wed Feb 20, 2019 10:56 pm
Forum: Balancing Redox Reactions
Topic: H2O
Replies: 3
Views: 110

### Re: H2O

You add H2O to balance the amounts of oxygen on the sides of reaction. Since you add H2O you then would at H+ on the other side of the reaction to balance it from the added H2O you just put in.
Mon Feb 18, 2019 11:48 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: TEST 3
Replies: 7
Views: 458

### Re: TEST 3

for electrochemistry up to but no including Nernst equation
Tue Feb 12, 2019 6:25 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Reasonable Assumptions
Replies: 2
Views: 118

### Re: Reasonable Assumptions

To answer the second part of your question, Delta U = 0 in isothermal systems because one of the equations Lavelle showed us is that
delta U = 3/2nR(delta T) and if there is no change in T then there is no change in U.
Mon Feb 11, 2019 2:30 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: Reversible vs. Irreversible
Replies: 6
Views: 166

### Re: Reversible vs. Irreversible

Remember that PV=nRT or P1V1=P2V2, that is, pressure and volume are inversely related so an increase in volume for example leads to a decrease in pressure.
Sun Feb 10, 2019 10:37 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Isothermal vs Reversible
Replies: 2
Views: 98

### Re: Isothermal vs Reversible

Actually reversible/isothermal systems are most efficient at doing work considering the area under the curve of reversible expansion vs irreversible expansion on Lavelle's outlines.
Fri Feb 08, 2019 10:18 pm
Forum: Phase Changes & Related Calculations
Topic: Signs in work equations
Replies: 2
Views: 129

### Re: Signs in work equations

I don't know about physics portion of work but Lavelle said the negative sign is because its related to the work of the gas. For example imagine a gas system with a piston, and when the gas expands, delta V would be positive and therefore the work is negative meaning the gas DID work. When the delta...
Fri Feb 08, 2019 10:14 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Internal Energy in a Reversible Isothermal expansion
Replies: 1
Views: 66

### Re: Internal Energy in a Reversible Isothermal expansion

Since temperature is constant in isothermal reactions, the internal energy is 0 because internal energy is dependent on temperature.
Fri Feb 08, 2019 10:11 pm
Forum: Calculating Work of Expansion
Topic: Which P to use? 6th edition, 8.27
Replies: 3
Views: 109

### Re: Which P to use? 6th edition, 8.27

Irreversible expansion uses the equation w = -PexΔV where you would plug in for pressure. For reversible expansion you would use w = -nRT x ln(vf/vi)... one of the TA's said that questions will almost always tell you what type of expansion it is, therefore you would use whatever equation is linked t...
Mon Feb 04, 2019 11:59 pm
Forum: Calculating Work of Expansion
Topic: q and delta H
Replies: 3
Views: 107

### Re: q and delta H

q is the same as delta H, enthalpy when the pressure is constant.
Mon Feb 04, 2019 12:23 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Cup of Tea
Replies: 17
Views: 658

### Re: Cup of Tea

Because it is an open system the system also is at a constant pressure because the system's pressure is the same as the outside pressure.
Sun Feb 03, 2019 2:43 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Midterm Exam Content
Replies: 4
Views: 132

### Re: Midterm Exam Content

No need for that equation since it's not on the outline
Sun Feb 03, 2019 2:41 pm
Forum: Phase Changes & Related Calculations
Topic: Week 4 Discussion Notes & Worksheet (2E, 2I, 2K)
Replies: 3
Views: 315

### Re: Week 4 Discussion Notes & Worksheet (2E, 2I, 2K)

Thanks Joyce
Sun Feb 03, 2019 2:40 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Gas vs solid
Replies: 5
Views: 147

### Re: Gas vs solid

Think of entropy as disorder, gas molecules and more dispersed and disordered in an aqueous solution whereas a solid is a literal solid and ordered.
Mon Jan 28, 2019 8:11 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7951
Views: 1177782

### Re: Post All Chemistry Jokes Here

acid
Tue Jan 15, 2019 12:53 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Change in K
Replies: 2
Views: 90

### Re: Change in K

Temperature changes K because temperature (average kinetic energy) of the molecules are increased/decreased which means the rate of collisions of the molecules are affected which ultimately affects the K equilibrium constant because the rates of both forward and reverse reactions are now changed bec...
Fri Jan 11, 2019 3:56 pm
Forum: Ideal Gases
Topic: Week 1 Discussion Notes (2E, 2I, 2K)
Replies: 2
Views: 287

### Re: Week 1 Discussion Notes (2E, 2I, 2K)

Thanks Joyce.
Fri Jan 11, 2019 3:55 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 6th edition 11.15
Replies: 1
Views: 51

### Re: 6th edition 11.15

This questions isn't included in Lavelle's syllabus so it's not something he wants us to master.
Sat Dec 08, 2018 10:05 pm
Forum: Biological Examples
Topic: Cisplatin
Replies: 7
Views: 433

### Re: Cisplatin

Cis-platin , cis means that the constituents are on the same side in the structure, in this case there are 2 Cl's on one side. This is effective in chemotherapy because when cisplatin interacts with DNA, Nitrogen from the DNA takes place of Cl causing the DNA to lose its structure and function and s...
Sat Dec 08, 2018 9:59 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Polydentates
Replies: 2
Views: 120

### Re: Polydentates

If it has multiple lone pairs. NH2CH2CH2NH2 there is 1 lone pair on each NH2 group in this structure so a total of 2 = bidentate.
Sat Dec 08, 2018 3:46 pm
Forum: General Science Questions
Topic: FINAL
Replies: 3
Views: 344

### Re: FINAL

Nope, he taught it last year but not to our year. Don't worry about weak acid calculations
Tue Dec 04, 2018 11:18 pm
Forum: Lewis Acids & Bases
Topic: Problem 12.15 6th Edition
Replies: 2
Views: 91

### Re: Problem 12.15 6th Edition

Check how many valence electrons there are and if your structures is over or under the amount of total valence electrons you can use.
Tue Dec 04, 2018 11:17 pm
Forum: Biological Examples
Topic: Ligands
Replies: 7
Views: 363

### Re: Ligands

Usually there will only be 1 metal and everything else is a ligand, also for coordination compounds, the metals are always transition metals.
Tue Dec 04, 2018 11:15 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Dissociation of strong acids/bases
Replies: 1
Views: 67

### Re: Dissociation of strong acids/bases

The physical state of the chemicals (aq) indicates that the reaction occurs with water as the solvent. Therefore when the dissociation occurs, the water accepts the protons from Ba(OH)2 and becomes H3O+.
Tue Dec 04, 2018 11:14 pm
Forum: Bronsted Acids & Bases
Topic: HCl Ionized
Replies: 1
Views: 83

### Re: HCl Ionized

Yes, because it is a strong acid. When H2O interacts with HCl, the interaction is strong enough for water to take the H+ and become H3O+ , leaving Cl-.
Sun Nov 25, 2018 12:25 am
Forum: Dipole Moments
Topic: Polarity
Replies: 9
Views: 228

### Re: Polarity

The main reason N is the central atom is because it is the least electronegative out of the 3 atoms (it does not want electrons as much as oxygen therefore oxygen is by itself because its selfish). Also considering formal charge N-N-O is the most stable.
Thu Nov 22, 2018 10:22 pm
Forum: Sigma & Pi Bonds
Topic: Carbon Pi bond hybridization
Replies: 2
Views: 85

### Re: Carbon Pi bond hybridization

The aufbau diagram for a sp2 hybridized carbon. Would be like sp2 _ _ _, then the other p orbital _. One trick to hybridization and pi bonds is that sigma bonds are formed by hybridized orbitals (sp, sp2, sp3) while pi bonds are formed with the unhybridized orbital. For sp2 hybridization , there is ...
Thu Nov 22, 2018 10:18 pm
Forum: Dipole Moments
Topic: Chemistry Community
Replies: 2
Views: 88

### Re: Chemistry Community

When you comment or something it tells you how many posts you have, that's how TA's will check most likely near the end of the quarter.
Thu Nov 22, 2018 10:18 pm
Forum: Dipole Moments
Topic: Chemistry Community
Replies: 5
Views: 117

### Re: Chemistry Community

It's both.
Thu Nov 22, 2018 10:17 pm
Forum: Dipole Moments
Topic: Polarity
Replies: 9
Views: 228

### Re: Polarity

Although it is linear, oxygen is more electronegative than nitrogen therefore it pulls on the electrons more to its side , creating a dipole moment and making oxygen slightly negative.
Sat Nov 10, 2018 12:08 am
Forum: Lewis Structures
Topic: Molecular shape and structure
Replies: 5
Views: 241

### Re: Molecular shape and structure

Not for lewis structure
Thu Nov 01, 2018 2:11 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: What is the notation for the valence-shell configuration?
Replies: 2
Views: 81

### Re: What is the notation for the valence-shell configuration?

I think it just means write out the electron configuration
Sun Oct 28, 2018 12:45 am
Forum: Ionic & Covalent Bonds
Topic: Valence electrons
Replies: 8
Views: 177

### Re: Valence electrons

One easy way is at the top of the periodic table, the last digit of the group numbers is usually the amount of valence electrons... Group 1 and 2 have 1 and 2 valence electrons respectively, 13, 14, 15, 16, 17, 18 have 3 , 4 , 5, 6, 7, 8 valence electrons.
Sun Oct 21, 2018 2:05 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: CH 1 1.39 6TH EDITION
Replies: 2
Views: 74

### Re: CH 1 1.39 6TH EDITION

You would calculate the wavelength using de Broglie's equation: lambda = h/(m * v). Where m is the mass and v is the velocity. Make sure units cancel out.
Fri Oct 19, 2018 12:26 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Lecture Question
Replies: 4
Views: 136

### Lecture Question

So why did Dr. Lavelle include ... after the L quantum numbers for s,p,d,f,... if theres only four blocks??
Sun Oct 14, 2018 12:31 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Orbitals problem 1E.11
Replies: 2
Views: 41

### Re: Orbitals problem 1E.11

We didn't learn those yet in lecture
Tue Oct 09, 2018 1:04 am
Forum: Properties of Light
Topic: 1.7.b. 6th edition
Replies: 1
Views: 59

### Re: 1.7.b. 6th edition

Yea the correct answer on the solutions manual is 150pm.
Tue Oct 09, 2018 1:03 am
Forum: Properties of Electrons
Topic: Energy per photon equation
Replies: 3
Views: 124

### Re: Energy per photon equation

Yes energy of each light photon is dependent on the frequency of the wave.
Thu Oct 04, 2018 9:13 pm
Forum: Balancing Chemical Reactions
Topic: Problem H1 (7th EDITION) Part A
Replies: 4
Views: 159

### Re: Problem H1 (7th EDITION) Part A

The right idea, basically changing the subscripts of any reactant/product in a chemical equation will change the chemical formula and ultimately the substance.
Thu Oct 04, 2018 8:52 pm
Forum: Molarity, Solutions, Dilutions
Topic: aqueous solutions
Replies: 1
Views: 70

### Re: aqueous solutions

Hey, so an aqueous solution means a solution that has water. (lol) So if they ask you to prepare a 510. gram solution containing 5.45% KNO3 by mass, you first would solve for the grams of KNO3 in the 510. solution (using the mass percent). This gets you 0.0545 x 510grams =27.8 grams of KNO3. The oth...
Thu Oct 04, 2018 8:44 pm
Forum: Molarity, Solutions, Dilutions
Topic: Homework Question G5
Replies: 3
Views: 81

### Re: Homework Question G5

Hey, this question is a bit tricky and I figured it out after Lavelle showed me through his office hours. First you would take your 2.111 grams of Na2CO3 and convert it to moles using the molar mass. Then take the moles and divide it by .250L to get the concentration of Na2CO3. The question is askin...
Thu Oct 04, 2018 8:38 pm
Forum: Limiting Reactant Calculations
Topic: Mole-to-mole predictions [ENDORSED]
Replies: 2
Views: 173

### Re: Mole-to-mole predictions[ENDORSED]

Hey, mole ratio is from a chemical reaction for example: 2A + B -> C + D Say you are told that you have 8 mols of A. Using the mole ratio from the chemical equation, for every 2 moles of A the reaction produces 1 mole of D. So you predict that with 8 moles of A, you expect to get 4 moles of D produc...
Thu Oct 04, 2018 8:32 pm
Forum: Limiting Reactant Calculations
Topic: Limiting Reactant vs. Reagent??? [ENDORSED]
Replies: 6
Views: 276

### Re: Limiting Reactant vs. Reagent???[ENDORSED]

Interchangeably. :)
Thu Oct 04, 2018 8:30 pm
Forum: Molarity, Solutions, Dilutions
Topic: QUESTION G15
Replies: 1
Views: 56

### Re: QUESTION G15

Hey, if you are referring to part a, the question says "What volume of .788 M Na2CO3 (aq) [initial molarity] should be diluted to 150.0mL (final volume) with water to reduce its concentration to .0234M Na2CO3 (aq) [final molarity]. (.788mol/L)(V1) = (.0234mol/L)(.150 L) Solve for initial volume.
Wed Oct 03, 2018 9:20 pm
Forum: Limiting Reactant Calculations
Topic: limiting reactant problem
Replies: 3
Views: 75

### Re: limiting reactant problem

The limiting reactant is A since the molar ratio of the reaction is 2A : 1B. You have 1 B for the reaction but only 1A so A limits the amount of product that is produced.
Wed Oct 03, 2018 9:07 pm
Forum: Limiting Reactant Calculations
Topic: Problem differentiating
Replies: 1
Views: 84

### Re: Problem differentiating

Usually limiting reactant questions will ask you how much of a product will be produced when ____ grams of Reactant A reacts with ____ grams of Reactant B. (For example A + B --> C + D). After finding the limiting reactant, use that reactant to calculate for the amount of product asked from the ques...
Wed Oct 03, 2018 9:02 pm
Forum: Molarity, Solutions, Dilutions
Topic: molarity conversion
Replies: 7
Views: 169

### Re: molarity conversion

Yes if the question gives you mL instead of liters.
Mon Oct 01, 2018 6:21 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Question E.23 Part D (Sixth Edition)
Replies: 1
Views: 102

### Re: Question E.23 Part D (Sixth Edition)

The multiplication sign with the H2O just means that that is a hydrate compound (special type of compound with water). To do this question I believe you convert grams to moles first. (Molar mass of Na2CO3 x 10H2O is 286 grams/mol). Using the molar mass, with 2.00 grams of the compound you get .00699...
Mon Oct 01, 2018 5:57 pm
Forum: Empirical & Molecular Formulas
Topic: Solving For Empirical and Molecular Formulas
Replies: 4
Views: 195

### Re: Solving For Empirical and Molecular Formulas

Yes it is necessary to find the mass % in order to solve the question unless it is given to you. For that particular question you would have to subtract 339.2 grams of Cobalt from the 996.08 grams of the compound to get 656.88 grams of the Fluorine gas. Then you would divide the Cobalt and Fluorine ...
Mon Oct 01, 2018 5:03 pm
Forum: Balancing Chemical Reactions
Topic: Need help w/ determining the moles of gas produced
Replies: 2
Views: 63

### Re: Need help w/ determining the moles of gas produced

Hey Kylie, the net moles of gas means the overall moles gas produced from the reactants. There are 36 moles on the product side and 30 moles on the reactant side. The net change is 36 - 30 = 6