## Search found 60 matches

Sat Mar 16, 2019 1:38 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Reverse and Forward
Replies: 1
Views: 88

### Re: Reverse and Forward

The equilibrium constant is equal to the forward reaction rate constant divided by the reverse reaction rate constant.
Sat Mar 16, 2019 1:36 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Activation Energy
Replies: 2
Views: 82

### Activation Energy

How can you tell whether a reaction is exothermic or endothermic based on activation energies for the forward and the reverse reaction, such as the homework problem 15.65 in the sixth edition?
Thu Mar 14, 2019 8:44 pm
Forum: General Rate Laws
Topic: 15.19 6th edition
Replies: 4
Views: 107

### Re: 15.19 6th edition

I am having the same issue too. Here is my work:
Sun Mar 10, 2019 4:32 pm
Forum: General Rate Laws
Topic: Writing Rate Laws
Replies: 3
Views: 117

### Re: Writing Rate Laws

Products are not included in the rate law because it looks at the initial concentrations when there are no products formed.
Sun Mar 10, 2019 4:31 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Activation Energy
Replies: 3
Views: 122

### Re: Activation Energy

The activation energy is the amount of energy required to go from the reactants to the transition state. So, if activation energy increases that results in more energy required, which causes for a slower reaction. A slower reaction means a higher reaction rate.
Sun Mar 10, 2019 4:17 pm
Forum: General Science Questions
Topic: Discussion Section Test
Replies: 3
Views: 368

### Re: Discussion Section Test

Yeah, my TA emailed us and said that if you put that photosynthesis is non-spontaneous, he would give us our points back.
Sun Mar 03, 2019 6:35 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Pt(s)
Replies: 10
Views: 337

### Re: Pt(s)

Pt(s) is generally used whenever a solid is not given to write the cell diagram for both the anode and the cathode.
Sun Mar 03, 2019 6:34 pm
Forum: Balancing Redox Reactions
Topic: balancing redox reactions
Replies: 5
Views: 171

### Re: balancing redox reactions

You use H+ and H20 to balance half reactions in an acidic solution. H20 is used to balance the oxygen atoms while H+ is used to balance the hydrogen ions. It is easier to balance oxygen first, so that you know how many H+ ions you need to balance the equation.
Sun Mar 03, 2019 6:31 pm
Forum: Administrative Questions and Class Announcements
Topic: Test 2 Scores
Replies: 6
Views: 201

### Re: Test 2 Scores

I believe we get them during discussion this week.
Sun Feb 24, 2019 6:02 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Quiz 3
Replies: 3
Views: 109

### Re: Quiz 3

Yeah, I was told the test will include everything from Gibbs Free energy till last Friday's lecture.
Sun Feb 24, 2019 6:00 pm
Forum: Student Social/Study Group
Topic: How are you guys going to study for Test 2?
Replies: 10
Views: 282

### Re: How are you guys going to study for Test 2?

Yeah, I always do all the homework problems to get prepared for the exams. Also, I try to do some of the worksheets that the UAs post on here.
Sun Feb 24, 2019 3:59 pm
Forum: Balancing Redox Reactions
Topic: TEST
Replies: 7
Views: 296

### Re: TEST

I don't think it will include concepts for Monday's lecture, but it will definitely include gibbs free energy.
Sun Feb 17, 2019 3:39 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Midterm Question
Replies: 8
Views: 253

### Re: Midterm Question

Yeah, I just used the equation for constant pressure of an ideal gas to solve for the heat capacity of nitrogen gas.
Sun Feb 17, 2019 3:37 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Work done vs work on system
Replies: 18
Views: 1390

### Re: Work done vs work on system

When work is being done on the system, w is positive, and when work is being done by the system w is negative.
Sun Feb 17, 2019 3:36 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: constant C
Replies: 7
Views: 399

### Re: constant C

There are different types of heat capacities. C refers to heat capacity when there is no constant pressure or volume. Cp refers to the heat capacity when it is an ideal gas at constant pressure while Cv is the heat capacity of an ideal gas at constant volume.
Sat Feb 09, 2019 1:11 am
Forum: Administrative Questions and Class Announcements
Topic: Lyndon's Midterm Review Sheet
Replies: 2
Views: 261

### Re: Lyndon's Midterm Review Sheet

He hasn't uploaded it on here yet, but he will make it sometime this weekend and will go over it during his review session on Monday 7pm-10pm in Franz 1178.
Sat Feb 09, 2019 1:07 am
Forum: Administrative Questions and Class Announcements
Topic: Midterm
Replies: 8
Views: 375

### Re: Midterm

The midterm will cover all the topics we talked about in lecture until Friday (2/8/18). It is helpful to go over the objectives on his outlines for concepts on the midterm.
Sat Feb 09, 2019 12:57 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: w=-PdeltaV
Replies: 6
Views: 212

### Re: w=-PdeltaV

The first one is used when the external pressure is not constant, which is reversible expansion, and the other equation is used when the external pressure is constant, which is irreversible expansion.
Sun Feb 03, 2019 3:08 pm
Forum: Calculating Work of Expansion
Topic: Units for pressure
Replies: 10
Views: 263

### Re: Units for pressure

To play it safe, I would just convert to atmospheres anytime you are asked for pressure.
Sun Feb 03, 2019 3:06 pm
Forum: Calculating Work of Expansion
Topic: What is Work?
Replies: 5
Views: 162

### Re: What is Work?

Work is the energy required to complete a certain reaction in terms of chemistry.
Sun Feb 03, 2019 3:01 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm Review
Replies: 14
Views: 503

### Re: Midterm Review

Will the Peer Learning Sessions continue with the week's content, content for Week 5, or will they be backtracking in order to help with Midterm review?

I think it will be content from Week 4 and a little bit of Week 5 depending on which day you go. I feel like most will be review for the midterm.
Sun Jan 27, 2019 9:32 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Ph and Pka
Replies: 5
Views: 125

### Re: Ph and Pka

If you are given the pKa, you would have to use the ICE table to find the concentration of [H3O+] at equilibrium and then take the -log of that value to find pH.
Sun Jan 27, 2019 9:27 pm
Forum: Ideal Gases
Topic: SI Units
Replies: 5
Views: 373

### Re: SI Units

It is atmospheres, which is the same thing as atm.
Sun Jan 27, 2019 9:26 pm
Forum: Administrative Questions and Class Announcements
Topic: Lecture Slides
Replies: 5
Views: 211

### Re: Lecture Slides

No, he said if you ever miss a lecture, just get the notes from someone.
Sat Jan 19, 2019 11:09 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Changes in K
Replies: 4
Views: 165

### Re: Changes in K

The equilibrium constant only changes when temperature changes. Anything else will not cause the ratio of products and reactant to change.
Sat Jan 19, 2019 11:00 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Concentrations Effect on K
Replies: 8
Views: 201

### Re: Concentrations Effect on K

K only changes when the ratio of products and reactants change, but when concentrations change, the ratio stays the same. Therefore, K stays the same.
Sat Jan 19, 2019 2:27 pm
Forum: Ideal Gases
Topic: PV=nRT
Replies: 8
Views: 592

### Re: PV=nRT

R is always a constant, so it will always be given. I think we may use the ideal gas law to convert from Kc to Kp or to find concentration when given pressure.
Sun Jan 13, 2019 1:00 pm
Forum: Ideal Gases
Topic: A bit of confusion
Replies: 3
Views: 121

### Re: A bit of confusion

Use the information in Table 11.2 to determine the value of K at 300 K for the reaction 2 BrCl(g) + H2(g) <--> Br2(g) + 2 HCl(g). So for this textbook question, you have to go to table 11.2 where it tells you the equilibrium constants at different temperatures for two separate equations. If you mul...
Sun Jan 13, 2019 12:51 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Keq
Replies: 3
Views: 82

### Re: Keq

Keq is used to represent either Kc or Kp, but I don't think you will be marked down if you use Keq all of the time. However, just to be safe I would use Kc when dealing with molarity and Kp when using partial pressure.
Sat Jan 12, 2019 11:27 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Solving for K
Replies: 7
Views: 182

### Re: Solving for K

It doesn't really matter if you use parentheses or brackets when solving for K in terms of calculation. But to find K c , you use concentrations, so it is more appropriate to use brackets to represent molarity while when finding K p , you use partial pressure which is represented with parentheses. T...
Sat Dec 08, 2018 3:07 pm
Forum: Bronsted Acids & Bases
Topic: Metal oxides and non-metal oxides
Replies: 1
Views: 115

### Re: Metal oxides and non-metal oxides

In the sixth edition of the textbook, table J.1 lists the strong acids and bases in water, so it would be helpful to memorize these. Strong acids include HBr, HCl, HI, HNO 3 , HClO 4 , HClO 3 , H 2 SO 4 . Strong bases include group 1 hydroxides, alkaline earth metal hydroxides, such as Ca(OH) 2 , Sr...
Sat Dec 08, 2018 3:00 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Rydberg’s Equation - Hydrogen
Replies: 2
Views: 325

### Re: Rydberg’s Equation - Hydrogen

Yes, the Rydberg's equation only applies to hydrogen, and we will only be required to know how to calculate energy levels for Hydrogen atoms.
Sat Dec 08, 2018 12:25 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Polydentates
Replies: 2
Views: 138

### Polydentates

Why is CO32- monodentate and bidentate?
Sun Dec 02, 2018 2:58 pm
Forum: Lewis Acids & Bases
Topic: Strong acids and strong bases
Replies: 5
Views: 163

### Re: Strong acids and strong bases

Yeah in lecture, he stated that strong acids and bases are completely ionized in water and weak acids and weak bases are not. So, for the scope of this class, you can say 100% dissociated.
Sun Dec 02, 2018 2:43 pm
Forum: Naming
Topic: With Respect to the Final
Replies: 9
Views: 403

### Re: With Respect to the Final

Yeah, you will need to know how to name compounds because in a lot of the homework problems, the name is given instead of the molecular formula. He usually says that the final will be similar to the homework problems.
Sun Dec 02, 2018 2:30 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Is Hydrogen Bonding a type of Dipole-Dipole Interaction?
Replies: 5
Views: 195

### Re: Is Hydrogen Bonding a type of Dipole-Dipole Interaction?

If the final asks for the intermolecular forces in a molecule, can we always write that London forces are present or are there cases where they are not? I believe Lavelle said that London Dispersion Forces are always present in between molecules that are close to each regardless of whether they are...
Sun Nov 25, 2018 7:02 pm
Forum: Hybridization
Topic: Hybridization scheme
Replies: 3
Views: 99

### Re: Hybridization scheme

It also helps to determine the VSEPR formula or the steric number of the molecule and then determine the hybridization from there.
Sun Nov 25, 2018 6:54 pm
Forum: Hybridization
Topic: Hybridized orbitals for Boron
Replies: 1
Views: 43

### Re: Hybridized orbitals for Boron

So in this molecule, all the borons have a formal charge of -1 and all the nitrogens have a formal charge of +1. Therefore, the molecule would have a net charge of zero.
Sun Nov 25, 2018 6:48 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Molecular Shape of (CH3)2Be
Replies: 1
Views: 78

### Re: Molecular Shape of (CH3)2Be

Since it is a polyatomic species, you would look at the individual molecular compounds to determine the shape. For each C, the 3 Hs and the Be are arranged symmetrically, around the C. So, the shape about the carbons would be tetrahedral. However, since the question is asking for the hybridization o...
Sun Nov 18, 2018 2:52 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Square Planar vs Tetrahedral
Replies: 8
Views: 571

### Re: Square Planar vs Tetrahedral

Also, in the example we did in class with XeF 4 , this is a square planar because it has 4 bonding pairs plus 2 lone pairs while a tetrahedral only has 4 bonding pairs, such as CH 4 . XeF4 has 6 regions of electron density while CH4 has 4 regions of electron density, which can also play a role in th...
Sun Nov 18, 2018 2:39 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: lone pairs
Replies: 11
Views: 308

### Re: lone pairs

Yes. In the example we did in class with the sulfite ion, the bond angles are expected to be 109.5 degrees because they are arranged tetrahedrally, but the bond angles are actually 106 degrees due to the extra lone pair on the sulfur atom.
Sun Nov 18, 2018 2:34 pm
Forum: General Science Questions
Topic: Audio Visuals
Replies: 6
Views: 479

### Re: Audio Visuals

MaiaRodriguezChoi3E wrote:Does anyone know of any resources similar to the audio visuals for the other topics this quarter? Do people find Khan academy helpful, or crash course videos?

I find Kahn Academy pretty helpful for understanding the general topics and if I need more specifics I will refer back to the textbook.
Sun Nov 11, 2018 5:27 pm
Forum: Ionic & Covalent Bonds
Topic: Lattice Energy
Replies: 2
Views: 140

### Re: Lattice Energy

Lattice energy is used in ionic compounds to describe the bond strength. It is the amount of energy required to separate a mole of an ionic solid into the gaseous form of its ions. For example, the lattice energy of NaCl is the energy released when gaseous Na+ and Cl– ions come together to form a la...
Sun Nov 11, 2018 5:07 pm
Forum: Lewis Structures
Topic: Formal Charge
Replies: 14
Views: 463

### Re: Formal Charge

I agree that the formal charge should be close to 0 on the central atom and if there are any charges they should be on the outer elements. It is also important to look at electronegativity, but the least electronegative element is more likely to be the central atom, so this follows the pattern that ...
Sun Nov 11, 2018 5:01 pm
Forum: Lewis Structures
Topic: Expanded Octets
Replies: 9
Views: 420

### Re: Expanded Octets

Any element on or below period 3 of the periodic table can have an expanded octet because these elements have d orbitals that can hold more electrons.
Sat Nov 03, 2018 9:11 pm
Forum: Administrative Questions and Class Announcements
Topic: What the Midterm Will Cover
Replies: 5
Views: 233

### Re: What the Midterm Will Cover

I believe that questions about the properties of bonds will not appear on the midterm because professor Lavelle said that midterm material that will appear on the test will be up to what we covered in lecture on Wednesday.
Sat Nov 03, 2018 9:06 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Test 2 1b
Replies: 2
Views: 333

### Re: Test 3 Version 2 1b

The change in uncertainty in momentum is inversely proportional to the uncertainty in its wavelength. Yes, you have to use De Broglie because wavelength equals h/momentum, so if momentum decreases, then wavelength increase and vice versa.
Sat Nov 03, 2018 8:55 pm
Forum: Lewis Structures
Topic: HW 6th Edition 3.57
Replies: 1
Views: 60

### HW 6th Edition 3.57

In the sixth edition, question 57 on chapter 3 asks to draw the lewis structure of hydrogen sulfite ion (HSO3^-). How do you know that hydrogen is not bonded to sulfur and instead it is bonded to oxygen because I found a way that all the formal charges are 0 expect for an oxygen when hydrogen is bon...
Sun Oct 28, 2018 1:42 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 4s and 3d [ENDORSED]
Replies: 2
Views: 161

### Re: 4s and 3d[ENDORSED]

The 4s orbital is filled before the 3d orbitals because the 4s subshell is lower in energy compared to 3d.
Sun Oct 28, 2018 1:39 pm
Forum: Photoelectric Effect
Topic: Work Function
Replies: 14
Views: 948

### Re: Work Function

The work function specifically refers to the minimum amount of energy required to eject an electron, and the threshold energy refers to the frequency that light has to reach to eject an electron. However, when calculating using the equation, they are the same thing, which is why Professor Lavelle us...
Sun Oct 28, 2018 1:33 pm
Forum: Ionic & Covalent Bonds
Topic: Determining the number of electrons in a compound [ENDORSED]
Replies: 2
Views: 136

### Re: Determining the number of electrons in a compound[ENDORSED]

So, to add up the electrons of a compound, you need to first count the number of valence electrons for each atom. In SO4^2-, Sulfur has 6 valence electrons and Oxygen has 6 valence electrons. But there is 4 oxygens, so the total number of electrons of oxygen is 24e-. You add the 24e- of oxygen with ...
Sun Oct 21, 2018 2:48 am
Forum: Properties of Light
Topic: 1.9 6th Edition
Replies: 1
Views: 63

### Re: 1.9 6th Edition

To fill in the activities section for this question, you had to correspond each event with the type of wave it uses. So, for example, reading is visible light and suntan is UV. Then, you compare the wavelengths you calculated in nanometers and list the events from largest to shortest wavelength. For...
Sun Oct 21, 2018 2:36 am
Forum: Properties of Light
Topic: Test 2
Replies: 7
Views: 330

### Re: Test 2

My TA said that the main topics covered on this test are photoelectric effect, De Broglie wavelength, Heisenberg uncertainty, Atomic spectra, and quantum numbers.
Sun Oct 21, 2018 2:28 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Test 2 Material
Replies: 9
Views: 212

### Re: Test 2 Material

I believe there will be questions on quantum numbers, but I don't think there will be anything on electron configuration since he hasn't gone over that yet. Dr. Lavelle also said on Friday that the Friday lecture will be the last topics covered on test 2.
Sun Oct 14, 2018 5:14 pm
Forum: SI Units, Unit Conversions
Topic: Sig Figs
Replies: 8
Views: 539

### Re: Sig Figs

I remember that I came across a question that listed no numbers, so I was told to use 4 significant figures. The answer in the book also listed 4 sig figs, so I would use 4 sig figs if no numbers were given.
Sun Oct 14, 2018 5:09 pm
Forum: Administrative Questions and Class Announcements
Topic: Test #2
Replies: 3
Views: 201

### Re: Test #2

I think it will be only on quantum world, so you should understand everything listed under outline 2.
Sun Oct 14, 2018 5:05 pm
Forum: Significant Figures
Topic: When to round the answers to significant figures
Replies: 11
Views: 705

### Re: When to round the answers to significant figures

Personally, I tend to be as accurate as possible on every step to get the closest I can to the correct answer, then I will round to the amount of significant figures. Sometimes,I am still a bit of by about .1 or .2, but most of the time it is pretty accurate.
Sat Oct 06, 2018 5:42 pm
Forum: Significant Figures
Topic: Empirical and Molecular Formula's Video #19
Replies: 3
Views: 391

### Re: Empirical and Molecular Formula's Video #19

The number of significant figures that the answer should have is determined by what is given in the question and not what has been calculated. Therefore, since the molar mass of 84 is the only number that is given, then the answer should have 2 significant figures because 84 has 2 sig figs. If there...
Sat Oct 06, 2018 5:35 pm
Forum: Empirical & Molecular Formulas
Topic: Chem Mod Empirical and Molecular Formulas Problem 22
Replies: 1
Views: 79

### Re: Chem Mod Empirical and Molecular Formulas Problem 22

So, I got the same ratio as you did, but instead of multiplying by 3, I multiplied by 5 to get 5:5:12. By multiplying by 3, the H would be 7.14 and you need whole numbers. Therefore, the answer is C5H12O5.
Sat Oct 06, 2018 5:12 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Naming Compounds
Replies: 3
Views: 67

### Naming Compounds

On the homework for E.9 on the sixth edition, there was a compound called magnesium sulfate heptahydrate, which is MgSO4, but they didn't provide the actual formula. For the first test, do we have to know how to name compounds? If so, how do we do that?