Search found 29 matches

by Jesus A Cuevas - 1E
Sun Jun 10, 2018 11:27 pm
Forum: SI Units, Unit Conversions
Topic: Sig Figs for Final
Replies: 8
Views: 364

Re: Sig Figs for Final

I believe at this point we are expected to have the appropriate number of significant figures. I would imagine the grading/marking off for incorrect significant figures will be similar to the midterm.
by Jesus A Cuevas - 1E
Sun Jun 10, 2018 7:36 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Homework Problem 17.33.)
Replies: 4
Views: 241

Homework Problem 17.33.)

Could someone help me with the following problem, thanks in advance! Which of the following ligands can be polydentate? If the ligand can be polydentate, give the maximum number of places on the ligand that can bind simultaneously to a single metal center: (a)HN(CH2CH2NH2)2; (b)CO3 2- (c)H2O (d)Oxal...
by Jesus A Cuevas - 1E
Mon Jun 04, 2018 5:47 pm
Forum: Student Social/Study Group
Topic: Homework Week 10
Replies: 1
Views: 144

Homework Week 10

For this last homework assignment, can we still do problems from outline #4 (Molecular Shape & Structure) or are we expected to only do problems from outlines 5 (Coordination Compounds and their Biological Importance) and 6 (Acid and Base Structures and Properties)? Thanks in advance!
by Jesus A Cuevas - 1E
Sun Jun 03, 2018 1:43 pm
Forum: Ionic & Covalent Bonds
Topic: Energetics of Ionic Bond Formation
Replies: 2
Views: 168

Re: Energetics of Ionic Bond Formation

Professor Lavelle has mentioned in class that often in his lectures and in the readings, values will be presented for energy released or gained of certain reactions among others values, but these value were found through experiments. Surely we could find the values ourselves with the appropriate for...
by Jesus A Cuevas - 1E
Sat Jun 02, 2018 11:13 am
Forum: Biological Examples
Topic: Chemotherapy Example
Replies: 2
Views: 251

Chemotherapy Example

I am having a little trouble remembering the reasoning behind cis-diamine-dichloro-platinum(II) being an effective cancer treatment, while trans-diamide-dichloro-platinum(II) is not. Can anyone clarify? Thanks in advance!
by Jesus A Cuevas - 1E
Sat Jun 02, 2018 10:56 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: coordination number vs. oxidation number [ENDORSED]
Replies: 4
Views: 344

Re: coordination number vs. oxidation number [ENDORSED]

From what I have read, the coordination number of an atom is the total number of ligands that are attached to the central ion, so I would assume you find the coordination number by counting the number of bonds on the central ion. And, the oxidation number is the total number of (e-)s required for th...
by Jesus A Cuevas - 1E
Tue May 29, 2018 10:31 am
Forum: Dipole Moments
Topic: Correct Dipole Depiction
Replies: 4
Views: 281

Re: Correct Dipole Depiction

I actually had the same question because it seemed like such a dramatic change in how its depicted. From what I've read they only mention there was "a change in convention", which doesn't really answer the question. Maybe Lavelle or other Chemmods are able to add more insight.
by Jesus A Cuevas - 1E
Fri May 25, 2018 10:09 am
Forum: Ionic & Covalent Bonds
Topic: Help on 3.5
Replies: 2
Views: 116

Re: Help on 3.5

Just a minor correction, for the asked (e-) configuration of Bi^3+ you would get [Xe] 4f14 5d10 6s2 since the (+3) removes the last three (e-)s from the original (e-) configuration of Bi ([Xe] 4f14 5d10 6s2 6p3).
by Jesus A Cuevas - 1E
Wed May 23, 2018 8:38 am
Forum: Formal Charge and Oxidation Numbers
Topic: Contribution in Formal Charge
Replies: 2
Views: 195

Contribution in Formal Charge

In the textbook, where it discusses the Correcting of the Covalent Model and the formal charge, they often mention "contribution" but I am not entirely sure what they are referring to in that. For example, in the section Correcting the Covalent Model the book states that because Chlorine h...
by Jesus A Cuevas - 1E
Tue May 22, 2018 11:14 pm
Forum: Dipole Moments
Topic: Correct Dipole Depiction
Replies: 4
Views: 281

Correct Dipole Depiction

The textbook mentions that when drawing the dipole we either use the original convention (arrow pointing towards the partial negative charge) or the modern convention (arrow pointing towards the partial positive charge). For the test, are we expected to use the modern convention like the textbook do...
by Jesus A Cuevas - 1E
Sun May 20, 2018 2:44 pm
Forum: Ionic & Covalent Bonds
Topic: Octet rule
Replies: 17
Views: 530

Re: Octet rule

The octet rule simply states that 3rd period elements will either want to accept or give away (e-)'s to obtain a full octet, to have an (e-) configuration of a noble gas.
by Jesus A Cuevas - 1E
Tue May 15, 2018 8:35 pm
Forum: Ionic & Covalent Bonds
Topic: 3.23 (meaning of oxidation)
Replies: 7
Views: 283

Re: 3.23 (meaning of oxidation)

Just to clarify for part (d),would we just state that we found the values by adding and subtracting electrons to obtain a full octet, or is other reasoning? Thanks in advance!
by Jesus A Cuevas - 1E
Tue May 08, 2018 11:19 am
Forum: DeBroglie Equation
Topic: test 2, question5
Replies: 5
Views: 335

Re: test 2, question5

Hey, so I am still having a little trouble with this problem. I know we must use the equation λ=(h/p) = (h/ (m*v)), but could anyone clarify how to solve this problem? Thanks in advance!
by Jesus A Cuevas - 1E
Mon May 07, 2018 10:45 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: homework week 6
Replies: 3
Views: 174

Re: homework week 6

For my section (1E) our teaching assistant said we could and should turn in problems from outline 2 since they would serve as good practice for our midterm. However, it may vary from section to section, so it might be best to ask your teaching assistant directly.
by Jesus A Cuevas - 1E
Sun May 06, 2018 4:23 pm
Forum: Student Social/Study Group
Topic: Practice Test (Lyndon) Answer Key
Replies: 1
Views: 269

Practice Test (Lyndon) Answer Key

Hey! So I didn't get a chance to attend the UA's review session last Friday (12:00 - 1:50 LaKretz 110), but does anyone know where we can find the answer key to the Practice Test (Lyndon's) they were going to review? Thanks in advance!
by Jesus A Cuevas - 1E
Sat May 05, 2018 2:40 pm
Forum: Ionic & Covalent Bonds
Topic: cation vs anion
Replies: 14
Views: 459

Re: cation vs anion

As a side note, another key difference between anions and cations is that anions will always be larger than their parent atom, while a cation will always be smaller than their parent atoms. Since electrons make up the bulk of an atom's mass the loss of electron(s) would result in a smaller atom (cat...
by Jesus A Cuevas - 1E
Thu May 03, 2018 9:15 pm
Forum: Quantum Numbers and The H-Atom
Topic: Bohr radius [ENDORSED]
Replies: 3
Views: 170

Re: Bohr radius [ENDORSED]

So from what I have read, the Bohr radius is a given constant with a value of a = 5.29177 x 10^-11 meters. What the Bohr constant represents is the average radius of a ground state hydrogen atom's orbit.
by Jesus A Cuevas - 1E
Sun Apr 29, 2018 6:32 pm
Forum: Quantum Numbers and The H-Atom
Topic: HW Problem 2.2 [ENDORSED]
Replies: 3
Views: 122

Re: HW Problem 2.2 [ENDORSED]

When an electron shifts position from one subshell to another they have undergone a change in energy. Movement to a higher energy subshell means that the electron has absorbed (gained) energy, and movement to a lower subshell would reflect the electrons' emission (loss) of energy.
by Jesus A Cuevas - 1E
Sun Apr 29, 2018 6:20 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration of Br-
Replies: 6
Views: 2999

Re: Electron Configuration of Br-

Presenting the electron configuration of Br- as [Kr] would be correct, but keep in mind that they may be expecting you to give the full electron configuration rather than just the shorthand.
by Jesus A Cuevas - 1E
Sun Apr 29, 2018 6:09 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: understanding orbitals [ENDORSED]
Replies: 8
Views: 229

Re: understanding orbitals [ENDORSED]

When it comes down to understanding what an orbital is, we must remember that electrons are not fixed, meaning they are in constant motion. The path of their movement is also not so straightforward, it does not follow a circular pattern as most of us would think, and not so easily described. That is...
by Jesus A Cuevas - 1E
Sun Apr 22, 2018 1:17 pm
Forum: General Science Questions
Topic: Rusty on High School Chem [ENDORSED]
Replies: 165
Views: 100720

Re: Rusty on High School Chem [ENDORSED]

I would definitely recommend completing the modules that professor Lavelle has provided for us. I would also take advantage of as many office hours or step-up sessions as possible. Both the TA's and the UA's are very approachable and nearly always have fewer than a couple of students at a time. The ...
by Jesus A Cuevas - 1E
Sun Apr 22, 2018 1:11 pm
Forum: Properties of Light
Topic: Speed of Light which is more accurate? [ENDORSED]
Replies: 6
Views: 211

Re: Speed of Light which is more accurate? [ENDORSED]

Technically the more accurate value for the speed of light would be 2.998x10^8. However, when it comes to constants it is always best to use the constant provided to us in either the formula sheet for the test or in the question for homework problems. As a side note, it is also best to keep your num...
by Jesus A Cuevas - 1E
Sun Apr 22, 2018 12:59 pm
Forum: Properties of Light
Topic: Test 2 [ENDORSED]
Replies: 4
Views: 208

Re: Test 2 [ENDORSED]

In short, no we are not expected to memorize the formulas since we will be provided a formula and constant sheet for all exams. However, we will be expected to know which formula to use and how to appropriately manipulate the formula for the given question. (i.e. p*c = ((h*c)/λ) ----> p = (h/λ) or E...
by Jesus A Cuevas - 1E
Sun Apr 15, 2018 5:02 pm
Forum: Photoelectric Effect
Topic: What is a vacuum?
Replies: 7
Views: 242

Re: What is a vacuum?

I believe the purpose of a vacuum in this experiment ensures that the ejection of the electrons from the metal observed was a result of the applied photons, and not other variables that could have potentially contributed to the ejection of the electrons if not removed (i.e. air molecules).
by Jesus A Cuevas - 1E
Sun Apr 15, 2018 4:46 pm
Forum: SI Units, Unit Conversions
Topic: Correct Units?? [ENDORSED]
Replies: 8
Views: 312

Re: Correct Units?? [ENDORSED]

Unless otherwise specified, the general rule of thumb is to give the answer in the units the givens were presented in. It is also good practice to recognize if your answer contains a 10^ x that better corresponds to another unit (ex: picometers 10^-12, megameters 10^9, decimeters 10^-1, etc.), but a...
by Jesus A Cuevas - 1E
Sun Apr 15, 2018 4:12 pm
Forum: Properties of Light
Topic: HW 1.7 (using nm vs pm)
Replies: 8
Views: 270

Re: HW 1.7 (using nm vs pm)

When it comes to the use of the short hands, it is determined by what power of 10 our answer is raised to. For this question, in part (a) it specifically asked for nanometers (10^-9) and in part (b) it asked for the answer in picometers (10^ -12). We will usually be told what units the final answer ...
by Jesus A Cuevas - 1E
Fri Apr 06, 2018 12:53 pm
Forum: Molarity, Solutions, Dilutions
Topic: F19
Replies: 3
Views: 209

Re: F19

1) Start with converting the percentage of the element into grams (16.48% O = 16.48g O). (2) Divide the mass of the elements from the compound by the actual molar mass from the periodic table for each element (O = 16.48g/15.999g = 1.03). (3) Then divide the result for each element by the smallest re...
by Jesus A Cuevas - 1E
Fri Apr 06, 2018 12:26 pm
Forum: Balancing Chemical Reactions
Topic: H.5.b [ENDORSED]
Replies: 7
Views: 270

Re: H.5.b [ENDORSED]

As a sidenote, for those that read like 4(O2)3, you would first multiply the subscripts then multiply by the coefficient. In this example, you'd get 6 oxygen from multiplying the subscript (2 x 3= 6), then multiply the result by the coefficient (4 x 6 = 24) giving you a total of 24 Oxygens.
by Jesus A Cuevas - 1E
Fri Apr 06, 2018 12:10 pm
Forum: Empirical & Molecular Formulas
Topic: Homework Question
Replies: 4
Views: 200

Re: Homework Question

For the most part, the general rule of thumb is that they must be 75% or greater to round up. If you were to round at this point you would get the empirical formula C3H3O1, which isn’t correct. Instead you should multiple by 3 that will give you numbers that are greater than the 75% and allow you to...

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