## Search found 59 matches

Sun Mar 17, 2019 10:59 am
Forum: Administrative Questions and Class Announcements
Topic: Saying Thank You to Dr. Lavelle
Replies: 282
Views: 134906

### Re: Saying Thank You to Dr. Lavelle

Thank you Dr. Lavelle! I was glad to be able to have Dr. Lavelle as a professor for both Chem 14A and 14B. All of the review sessions and lectures were helpful and I enjoyed this class a lot!
Sun Mar 17, 2019 10:58 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Pre Equilibrium Approach
Replies: 3
Views: 391

### Re: Pre Equilibrium Approach

Typically we are given a fast step and slow step when asked to use this approach
Sun Mar 17, 2019 10:56 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: OH-(aq) in cell diagram
Replies: 3
Views: 308

### Re: OH-(aq) in cell diagram

Yes, you include both
Sun Mar 17, 2019 10:55 am
Forum: First Order Reactions
Topic: Time Conversions
Replies: 9
Views: 507

### Re: Time Conversions

You can use any time unit as long as the same time unit is used for all values in the problem.
Sun Mar 17, 2019 10:54 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: When is delta U = 0?
Replies: 4
Views: 416

### Re: When is delta U = 0?

In isothermal systems, the internal energy does not change so delta U is always equal to zero.
Sun Mar 17, 2019 10:53 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Work done vs work on system
Replies: 18
Views: 1413

### Re: Work done vs work on system

I believe the way we've been doing in class is work done by the system is negative and work done on a system is positive.
Sun Mar 17, 2019 10:52 am
Forum: General Rate Laws
Topic: reaction rate(s)?
Replies: 4
Views: 344

### Re: reaction rate(s)?

Reaction rate is the actual rate while rate law is the formula (ex. rate=k[A])
Sun Mar 17, 2019 10:51 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Inert Electrodes
Replies: 3
Views: 325

### Re: Inert Electrodes

I believe we can always use platinum.
Sun Mar 17, 2019 10:50 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: Finding rate constant
Replies: 2
Views: 339

### Re: Finding rate constant

We can use the straight line formula for first-order reactions.
Sun Mar 17, 2019 10:49 am
Forum: General Rate Laws
Topic: slow step
Replies: 11
Views: 584

### Re: slow step

In most of the problems we've done, it seems to be explicitly stated in the problem.
Sun Mar 17, 2019 10:47 am
Forum: Ideal Gases
Topic: K and Q
Replies: 8
Views: 481

### Re: K and Q

Solids and liquids do not make much difference in equilibrium. Therefore, they are excluded.
Sun Mar 17, 2019 10:42 am
Forum: Zero Order Reactions
Topic: overall rate
Replies: 5
Views: 431

### Re: overall rate

Zero-order reactions are not included in the overall rate
Sun Mar 17, 2019 10:41 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Midterm Q4
Replies: 3
Views: 347

### Re: Midterm Q4

ICE Table is not needed for this problem, which is why it was probably not used in the solutions.
Sun Mar 17, 2019 10:40 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: galvanic cells
Replies: 6
Views: 464

### Re: galvanic cells

Two lines would indicate a salt bridge instead. A porous disc is indicated by a single line.
Sun Mar 17, 2019 10:39 am
Forum: Experimental Details
Topic: picking a trial
Replies: 7
Views: 453

### Re: picking a trial

We can pick any trial and should end up with the correct result
Sun Mar 17, 2019 10:37 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Final
Replies: 5
Views: 454

### Re: Final

I believe Dr. Lavelle may put more of an emphasis on problems based on material learned after the midterm.
Sun Mar 17, 2019 10:35 am
Forum: Ideal Gases
Topic: ICE table
Replies: 7
Views: 411

### Re: ICE table

You create an ICE table subtracting x from the initial concentrations of your reactants and adding x to products. You also multiply x by stoichiometric coefficients.
Sun Mar 17, 2019 10:33 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: K vs k1/k'1
Replies: 6
Views: 481

### Re: K vs k1/k'1

Both should be considered correct
Sun Mar 17, 2019 10:32 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: pKa and pKb
Replies: 4
Views: 393

### Re: pKa and pKb

Yes. To calculate pH for base, we would need to use Kb and not Ka.
Sun Mar 17, 2019 10:31 am
Forum: First Order Reactions
Topic: First Order Equation
Replies: 3
Views: 296

### Re: First Order Equation

We can also use this equation to solve for initial concentrations or rate constant if needed.
Sun Mar 17, 2019 10:30 am
Forum: Reaction Mechanisms, Reaction Profiles
Replies: 1
Views: 298

We will only be tested on the pre-equilibrium approximation
Sun Mar 17, 2019 10:29 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Arrhenius eq
Replies: 3
Views: 373

### Re: Arrhenius eq

Yes, as Dr. Lavelle has stated during lecture.
Sun Mar 17, 2019 10:27 am
Forum: Zero Order Reactions
Topic: Zero order reaction
Replies: 8
Views: 441

### Re: Zero order reaction

Concentration doesn't have any effect on the rate
Sun Mar 17, 2019 10:25 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalysts
Replies: 16
Views: 601

### Re: Catalysts

A lower peak would be seen with a catalyst.
Sun Mar 17, 2019 10:24 am
Forum: Calculating Work of Expansion
Topic: Reversible vs irreversible
Replies: 2
Views: 311

### Re: Reversible vs irreversible

I believe that it will be given in the problem whether the reaction is reversible or irreversible.
Sun Mar 17, 2019 10:21 am
Forum: Administrative Questions and Class Announcements
Replies: 179
Views: 12674

For worksheet 4 #6, I get a different value for the amount of work done. I get 12.4 kJ instead of 10.1kJ. Is there a mistake in the solutions?
Sat Dec 08, 2018 9:45 pm
Forum: Conjugate Acids & Bases
Topic: Strong acids
Replies: 3
Views: 297

### Re: Strong acids

Longer bond lengths means that the bonds are weaker and the acids are stronger. Strong acids have weak conjugate bases.
Sat Dec 08, 2018 9:32 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: ClO2+
Replies: 4
Views: 224

### Re: ClO2+

No, if you take a look at the actual electronegativity values, O is more electronegative than Cl.
Sat Dec 08, 2018 9:25 pm
Forum: Amphoteric Compounds
Topic: Amphiprotic vs. Amphoteric
Replies: 7
Views: 521

### Re: Amphiprotic vs. Amphoteric

No, while all amphiprotic substances are amphoteric, not all amphoteric substances are amphiprotic.
Sat Dec 08, 2018 9:18 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Ka and Kb on Final
Replies: 9
Views: 2195

### Re: Ka and Kb on Final

Yes, the larger the value of Kb, the stronger the base.
Sat Dec 08, 2018 8:36 am
Forum: Bronsted Acids & Bases
Topic: Cl- and F-
Replies: 4
Views: 215

### Re: Cl- and F-

Strong acids completely dissociate. HCl would completely dissociate into H+ and Cl- ions and therefore won't be able to turn back into HCl while HF is a weaker acid, so it doesn't completely dissociate. Since HF doesn't completely dissociate, F- has the ability to pick up a proton/hydrogen and becom...
Sat Dec 08, 2018 8:33 am
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Factors for Acid Stength [ENDORSED]
Replies: 3
Views: 285

### Re: Factors for Acid Stength[ENDORSED]

Size -> larger size -> more polarizable -> weaker bond -> stronger acid
Electronegativity -> higher electronegativity -> pulls electrons very strongly -> more stable -> stronger acid
Resonance -> electrons are more spread out -> more stable -> stronger acid
Sat Dec 08, 2018 8:24 am
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: J5 Sixth Edition
Replies: 1
Views: 191

### J5 Sixth Edition

For part c on J.5, for the net ionic equation the solutions manual says it is H+ + OH- -> 2H2O . Shouldn't it be H+ + OH- -> H2O? Or are they maybe using H3O+ instead of H+ in this equation? When do we use H3O+ instead of H+?
Sat Dec 08, 2018 8:18 am
Forum: Dipole Moments
Topic: London Dispersion
Replies: 5
Views: 574

### Re: London Dispersion

In larger heavier atoms/molecules, there are more polarizable electrons causing the LDFs to be so strong that they can be even stronger than dipole-dipole forces.
Sat Dec 08, 2018 8:08 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Angles
Replies: 2
Views: 147

### Re: Angles

This is also due to the fact that fluorine is way more electronegative than hydrogen.
Sat Dec 08, 2018 8:03 am
Forum: Ionic & Covalent Bonds
Topic: Boiling point
Replies: 5
Views: 388

### Re: Boiling point

NH3 can have Hydrogen bonding (between H and N), dipole-dipole (due to NH3 being a polar molecule), and London dispersion forces. CH4 is nonpolar so it only has London dispersion forces. NH3 has more and also stronger intermolecular forces, so it will have a higher boiling point.
Sat Dec 08, 2018 7:57 am
Forum: Naming
Topic: churro 31
Replies: 4
Views: 233

### Re: churro 31

The answer above is correct, except I believe when Lyndon went over this in the review session, he said to use ONO instead of NO2.
Sat Dec 08, 2018 7:51 am
Forum: Dipole Moments
Topic: churro 38
Replies: 3
Views: 342

### Re: churro 38

Although H2S has stronger dipole-dipole forces, the LDFs in H2Se are stronger than that of H2S. These forces are strong enough to overcome even the dipole-dipole forces of H2S.
Sat Dec 08, 2018 7:47 am
Forum: Ionic & Covalent Bonds
Topic: Boiling point
Replies: 3
Views: 218

### Re: Boiling point

Larger and heavier molecules have stronger London dispersion forces. C5H12 is a bigger molecule, therefore C5H12 has stronger LDFs and you will need a higher temperature to break apart these attractive forces so C5H12 has a higher boiling point.
Sat Dec 08, 2018 7:35 am
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Why are LDFs everywhere?
Replies: 3
Views: 468

### Re: Why are LDFs everywhere?

All molecules have LDFs. They are forces of attraction that occur when electrons in adjacent atoms occupy positions that make the atoms form temporary dipoles. Molecules have LDFs to hold the molecules together.
Sat Dec 08, 2018 7:16 am
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Ka and Kb on Final
Replies: 9
Views: 2195

### Re: Ka and Kb on Final

We do not need to know these for the final. Just in case, I think it would be good to at least keep in mind that pKa is -log(Ka) and that the bigger the value of Ka is the stronger the acid.
Sat Dec 08, 2018 7:06 am
Forum: Naming
Topic: Question on test 3
Replies: 2
Views: 145

### Re: Question on test 3

The bent shape of O3 is caused by a lone electron pair on O. The lone electron pair on the central atom causes a positive partial charge above and negative partial charge below. These opposing charges cause a net dipole. I3- is linear with the same atom of each side of the central atom; there is no ...
Sat Dec 08, 2018 6:51 am
Forum: Amphoteric Compounds
Topic: Amphiprotic vs. Amphoteric
Replies: 7
Views: 521

### Re: Amphiprotic vs. Amphoteric

Amphiprotic substances can accept and donate protons, amphoteric substances can act as both an acid and a base. All amphiprotic compounds are amphoteric. A clue to determine if a substance is amphoteric is to first check if there are hydrogens/protons to donate in the substance. If not, the substanc...
Sat Dec 08, 2018 6:34 am
Forum: Determining Molecular Shape (VSEPR)
Topic: ClO2+
Replies: 4
Views: 224

### Re: ClO2+

This is because you want the positive charge to be on Cl instead of O (due to Cl being less electronegative than O).
Sat Dec 08, 2018 6:11 am
Forum: Hybridization
Topic: 4.43 Increasing s-character of hybrids
Replies: 2
Views: 106

### Re: 4.43 Increasing s-character of hybrids

s-character of sp: 50%, sp^2: 33%, sp^3: 25%, etc. s-character increases as you go from sp^3 hybridization to sp hybridization. While in sp^3, there are four regions of electron density, sp has two. Less regions of electron density allow for more room between the regions so the bond angles increase ...
Sat Dec 08, 2018 4:59 am
Forum: Electronegativity
Topic: Electronegativity Trend
Replies: 1
Views: 266

### Electronegativity Trend

I know that electronegativity increases as you go right across a period and go up along a group, but between going up a group and going across a period, which causes a larger increase in electronegativity? For example, without being given the exact electronegativity values, can you tell if S and Cl ...
Sat Dec 08, 2018 4:47 am
Forum: Lewis Structures
Topic: Does the Orientation of Surrounding Atoms matter?
Replies: 1
Views: 356

### Does the Orientation of Surrounding Atoms matter?

For example, for SCl4, I drew the Cl atoms directly top, bottom, left, and right of S, but SCl4 is seesaw-shaped so the solutions manual has it drawn with a different orientation of the Cl atoms (1 directly above S, 1 directly under S, and 2 more Cl atoms in between those 2). Would my Lewis structur...
Sat Dec 08, 2018 4:21 am
Forum: Dipole Moments
Topic: Why is CH2Cl2 polar while CH4 is not?
Replies: 2
Views: 965

### Why is CH2Cl2 polar while CH4 is not?

I keep reading that the reason why CH2Cl2 is polar because due to its tetrahedral shape, the dipoles can not cancel each other out but doesn't CH4 also have tetrahedral shape too? I assumed, since the reason for CH2Cl2 being polar is apparently due to the 109.5 degree angles from the tetrahedral sha...
Sat Dec 08, 2018 3:42 am
Forum: Lewis Structures
Topic: Which resonance structure is the most stable?
Replies: 2
Views: 106

### Which resonance structure is the most stable?

When drawing the Lewis structure of the ClO2+ ion, there are different possible structures. One uses double bonds for both the Cl-O bonds while another uses a double bond for one of the Cl-O bonds and a single bond for the other. Both end up with the same overall formal charge of +1. If I am not mis...
Sun Oct 28, 2018 11:44 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Balmer series, Lyman series?
Replies: 3
Views: 222

### Balmer series, Lyman series?

Some of the problems in Chapter 1 involved knowing concepts such as the Balmer series and the Lyman series, but these were not on the Outline 2 or on the test. Do we need to fully master these concepts for the midterm?
Sun Oct 28, 2018 11:21 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Electron Transitions
Replies: 1
Views: 121

### Electron Transitions

I was doing the problems on the worksheet that one of the UAs posted (worksheet #2), and I need help on number 7. The problem is "An excited hydrogen atom emits light with a frequency of 1.14x10 1.14x10^{14} Hz to reach the energy level for which n=4. In what principle quantum level did the ele...
Sun Oct 28, 2018 10:47 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Heisenberg
Replies: 2
Views: 201

### Heisenberg

I have trouble understanding how to apply Heisenberg's uncertainty principle. Just to confirm, if the problem states, for example, that the speed is known to be +/- 0.55 m/s then the change in velocity that we plug into the equation would be 2(0.55) and not 0.55 right?
Thu Oct 18, 2018 2:20 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: 2.29 (6th Edition)
Replies: 1
Views: 62

### 2.29 (6th Edition)

I am confused on parts b and d on this problem. How does specifying the magnetic quantum number change the number of orbitals and/or the number of electrons that the orbitals can hold? QUESTION 2.29 How many electrons can have the following quantum numbers in an atom: (b) n =4, l= 2, ml= 2; (d) n =...
Sun Oct 14, 2018 8:56 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: HW 2 ch1 1.51
Replies: 2
Views: 91

### Re: HW 2 ch1 1.51

The problem states that in infrared spectroscopy, we express energy in terms of v /c. Therefore, for part (a), v/c = 3600 cm^-1 v = (c)(3600cm^-1) = (2.997 x 10^8 m/s)(3600cm^-1) After this, convert the value for c into terms of cm/s in order to cancel out the units, and you should be left with a va...
Sun Oct 14, 2018 8:34 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: 2.1 6th Edition
Replies: 1
Views: 118

### 2.1 6th Edition

Hello! I know this is literally the first question for Chapter 2, but I'm having trouble understanding this concept. The solutions manual says that the radius of the atom will increase when the electron in a hydrogen atom undergoes a transition from the 1s-orbital to a 2p-orbital, and I was wonderin...
Sun Oct 14, 2018 8:17 pm
Forum: Properties of Light
Topic: De Broglie Equation
Replies: 6
Views: 205

### Re: De Broglie Equation

Yes, as others have stated before, you should use kg in order to keep consistency since Planck's constant is in kg. I believe that during the lecture, Dr. Lavelle also said we will use kg due to kg being the standard SI unit for mass!
Fri Oct 05, 2018 1:40 am
Forum: SI Units, Unit Conversions
Topic: E23 (6th Edition)
Replies: 4
Views: 138

### E23 (6th Edition)

Hello! This may seem like a dumb question, but for all parts of this problem, we are finding the moles of the units specified in each part, so it is unnecessary to use Avogadro's number for any of these parts right? The problem is: Calculate the amount (in moles) of (a) Cu2+ ions in 3.00 g of CuBr2;...
Wed Oct 03, 2018 11:57 pm
Forum: Balancing Chemical Reactions
Topic: H19 (6th Edition) [ENDORSED]
Replies: 3
Views: 245

### H19 (6th Edition)[ENDORSED]

This question wants us to write the balanced equation for the combustion of the solid C14H18N2O5 to carbon dioxide gas, liquid water, and nitrogen gas. I understand how to balance the reaction, but I need help on starting the equation!
Wed Oct 03, 2018 10:42 pm
Forum: Empirical & Molecular Formulas
Topic: F.13
Replies: 6
Views: 2410

### Re: F.13

We already know that we have 4.14 grams of phosphorus, so we only need to solve for grams of chlorine. We know we have 27.8 grams of product, so 27.8 g product - 4.14 g P = 23.66 g Cl2 Convert into moles: 4.14g P x 1mol/30.97g = .134 mol P 23.66g Cl2 x 1mol/70.9g = .334 mol Cl2 Now, divide both valu...