Search found 48 matches

by jessicahe4Elavelle
Mon Feb 18, 2019 11:08 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: TEST 3
Replies: 7
Views: 28

TEST 3

What are the topics we have to know for our upcoming test ?
by jessicahe4Elavelle
Mon Feb 18, 2019 11:00 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Negative Delta G
Replies: 7
Views: 17

Re: Negative Delta G

the formula for is delta G = delta H - T delta S. So if:
- delta H is positive and delta S is negative, delta G will definitely be positive
- delta H is negative and delta S is positive, delta G will definitely be negative
by jessicahe4Elavelle
Mon Feb 18, 2019 10:55 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Isolated system
Replies: 10
Views: 42

Re: Isolated system

a bomb calorimeter is an isolated system because no matter or heat can be exchanged through it.
by jessicahe4Elavelle
Mon Feb 11, 2019 12:02 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Constant Vol.
Replies: 5
Views: 30

Re: Constant Vol.

The equation for the work is Pext x change in volume, so if the volume is constant, the change in volume is zero therefore pressure is multiplied by zero which is w=0
by jessicahe4Elavelle
Mon Feb 11, 2019 12:01 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Using R
Replies: 9
Views: 34

Re: Using R

All the values of R are in the equation sheet provided to us. To see which R to use, you should check the units, specifically if it uses atm or joules or Torr.
by jessicahe4Elavelle
Sun Feb 10, 2019 11:59 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Midterm #1 14B
Replies: 12
Views: 114

Re: Midterm #1 14B

Ronald Thompson 1F wrote:Is there a solutions guide as well?


Lyndon said that he is not going to post any solutions so you should go to his review session in order to get the solutions.
by jessicahe4Elavelle
Mon Feb 04, 2019 2:34 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond Enthalpies
Replies: 4
Views: 18

Re: Bond Enthalpies

It is always best to draw Lewis structures so that you don't get confused or forget some bonds if you're visualizing structures in your head.
by jessicahe4Elavelle
Mon Feb 04, 2019 2:32 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Midterm [ENDORSED]
Replies: 47
Views: 425

Re: Midterm [ENDORSED]

The best way to prepare in my opinion is reading the concepts in the book, understanding the sample problems and finally doing ALL homework problems assigned to us. Practice is key.
by jessicahe4Elavelle
Mon Feb 04, 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: W=2^NA
Replies: 3
Views: 29

Re: W=2^NA

The NA represents the number of molecules or atoms in the system, so if there are 2 molecules of C02, for example, the NA would be 2. If you have one mole of CO2, the amount of molecules of CO2 is given by avogadro's number so NA would be Avogadro's number.
by jessicahe4Elavelle
Mon Jan 28, 2019 1:27 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Le Chatelier's Principle
Replies: 2
Views: 22

Re: Le Chatelier's Principle

If there are an even amount of moles on either side the reaction is unaffected by a change in pressure.
by jessicahe4Elavelle
Mon Jan 28, 2019 1:26 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Le Chatelier's Principle
Replies: 3
Views: 21

Re: Le Chatelier's Principle

Le chateliers principle applies on to reactions at equilibrium as it determines how a change in the system at equilibrium will affect the direction of the reaction.
by jessicahe4Elavelle
Mon Jan 28, 2019 1:25 pm
Forum: Ideal Gases
Topic: sre
Replies: 1
Views: 16

Re: sre

Standard enthalpy of reaction is the enthalpy change that occurs in a system for a reaction in which it’s reactants and products are in their standard state.
by jessicahe4Elavelle
Mon Jan 21, 2019 1:41 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Inert gas effect on Equilibrium constant
Replies: 4
Views: 29

Re: Inert gas effect on Equilibrium constant

The only factor that can change the equilibrium constant is temperature. Pressure can not change Equilibrium constant but it changes the direction of the reaction only if the change in pressure was caused by a change in volume because in that case there was a change in concentration.
by jessicahe4Elavelle
Mon Jan 21, 2019 1:31 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: pressure and volume
Replies: 5
Views: 27

Re: pressure and volume

Only a change in pressure that is caused by a change in volume affects the direction of the reaction because for an increase in volume, for example, causes a decrease in pressure (PV=nRT) and consequently a change in concentration. On the other hand, if the pressure changes because extra inert gases...
by jessicahe4Elavelle
Mon Jan 21, 2019 1:27 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Weak acid and its salt
Replies: 3
Views: 22

Re: Weak acid and its salt

No, first and second group cations do not affect pH so we shouldn't take them into account. Also the anions Cl, Br and I do not affect pH.
by jessicahe4Elavelle
Sun Jan 20, 2019 10:39 pm
Forum: Ideal Gases
Topic: OH and H3O
Replies: 9
Views: 69

Re: OH and H3O

To distinguish weak acids from strong acids you should just essentially memorize the list of strong acids (they are 7 in total HCl - hydrochloric acid, HNO3 - nitric acid, H2SO4 - sulfuric acid, HBr - hydrobromic acid, HI - hydroiodic acid, HClO4 - perchloric acid and HClO3 - chloric acid). The stro...
by jessicahe4Elavelle
Sun Jan 20, 2019 10:37 pm
Forum: Ideal Gases
Topic: ICE table
Replies: 10
Views: 53

Re: ICE table

Ice tables can be used for both molarity and partial pressure because the concept is basically the same (Initial pressure, change in pressure and equilibrium pressure). For partial pressure you would just use Kp instead of Kw.
by jessicahe4Elavelle
Sun Jan 20, 2019 10:32 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Quadratic method for weak acids and bases
Replies: 1
Views: 16

Re: Quadratic method for weak acids and bases

I think you might be getting confused because I thought that the ICE and quadratic method was used solely to calculate the pH or pOH of weak acids and bases because for strong ones you just know that they dissociate completely.
by jessicahe4Elavelle
Sat Dec 08, 2018 7:07 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Ka and Kb
Replies: 2
Views: 24

Re: Ka and Kb

No, Ka and Kb are used to calculate the pHs and pOHs of weak acids and bases but we are only working with strong acids and bases that dissociate completely in an aqueous solution.
by jessicahe4Elavelle
Sat Dec 08, 2018 7:06 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Memorizing Acids by name
Replies: 3
Views: 44

Re: Memorizing Acids by name

I think that you should memorize all the strong acids (they are 7: HCl, HBr, HI, HClO3, HClO4, H2SO4, HN03). Strong bases are basically all the metal oxides and metal hydroxides
by jessicahe4Elavelle
Sat Dec 08, 2018 7:04 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: ions
Replies: 3
Views: 37

Re: ions

A cation is a positive ion, so an atom that has lost one or more electrons thus becoming positively charged
by jessicahe4Elavelle
Fri Dec 07, 2018 4:18 pm
Forum: Identifying Acidic & Basic Salts
Topic: Ammonia and phosphoric acid
Replies: 1
Views: 42

Re: Ammonia and phosphoric acid

Water is for sure formed only when a strong base is present in the neutralization reaction. In this case ammonia is a weak base.
by jessicahe4Elavelle
Fri Dec 07, 2018 4:13 pm
Forum: Biological Examples
Topic: Ligands
Replies: 3
Views: 42

Re: Ligands

Chronium - assists insulin in control of blood sugar
Iron - facilitates electron transfer in the oxidation of carbohydrates, proteins and fats
Cobalt - for Vitamin B12
Manganese, Nickel, Copper and Zinc - critical for enzime function.
by jessicahe4Elavelle
Sun Dec 02, 2018 3:23 pm
Forum: Lewis Acids & Bases
Topic: Weak and Strong Acids/Bases
Replies: 7
Views: 82

Re: Weak and Strong Acids/Bases

For the acids, there are in total 7 strong acids that you should just memorize: HCl, HBr, HI, HNO3, HClO3, HClO4, H2SO4. (so the rest would be weak acids). The strong bases, instead you can recognize them as they are always a metal hydroxide (e.g. LiOH, NaOH, KOH...).
by jessicahe4Elavelle
Sat Dec 01, 2018 2:15 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Induced dipoles
Replies: 4
Views: 27

Re: Induced dipoles

Basically, electrons in an atom fluctuate over time and in one instant electrons may accumulate on one part of a molecule making side of the molecule more negative and leaving the other side more positive, becoming, therefore, an instantaneous dipole. An instantaneous dipole moment on one molecule w...
by jessicahe4Elavelle
Sat Dec 01, 2018 2:08 pm
Forum: Lewis Acids & Bases
Topic: Lewis and Bronsted
Replies: 8
Views: 49

Re: Lewis and Bronsted

In the Bronsted definition, an acid is a proton donor while a base is a proton acceptor. In the Lewis definition instead, an acid is an electron acceptor while the base is the electron donor. While the definition may be different, both Lewis and Bronsted pretty much refer to the same thing.
by jessicahe4Elavelle
Tue Nov 27, 2018 4:44 pm
Forum: Electronegativity
Topic: Electronegativity values
Replies: 2
Views: 29

Electronegativity values

Are we supposed to memorize electronegativity values? I know the general trend but if it asks for example: which pair has the most ionic character between CH4 and CF4, how am I supposed to know the electronegativity difference exactly.
by jessicahe4Elavelle
Sun Nov 18, 2018 11:43 pm
Forum: Sigma & Pi Bonds
Topic: sigma and pi bonds
Replies: 2
Views: 29

Re: sigma and pi bonds

A σ bond has cylindrical symmetry while a π bond has a nodal plane that includes the bond axis.
by jessicahe4Elavelle
Sun Nov 18, 2018 11:32 pm
Forum: Ionic & Covalent Bonds
Topic: Intra vs Intermolecular forces
Replies: 9
Views: 136

Re: Intra vs Intermolecular forces

Intramolecular forces are harder to break because it would be breaking the actual bonds between atoms. Intermolecular forces are forces between different molecules and include things like London dispersion forces, Van der Waals forces, and dipole-dipole interactions and are easier to break.
by jessicahe4Elavelle
Sun Nov 18, 2018 10:33 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: lone pair influence on shape
Replies: 12
Views: 69

Re: lone pair influence on shape

Electrons are negatively charged and repulse other electrons. A lone pair causes an area of high electron density so electrons repel each other more strongly than bonding pairs causing a distortion in the shape (lower angle).
by jessicahe4Elavelle
Sun Nov 11, 2018 9:22 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: Induced Dipole - Induced Dipole
Replies: 1
Views: 30

Re: Induced Dipole - Induced Dipole

The larger the molar mass, the more electrons the atom has. In larger atoms, the valence electrons are farther from the nuclei than in smaller atoms so they are less tightly held and can more easily form temporary dipoles. Also, an atom that has a large cloud of electrons is more easily distorted an...
by jessicahe4Elavelle
Sun Nov 11, 2018 9:09 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Polarization of cation's
Replies: 2
Views: 31

Re: Polarization of cation's

Yes cations’ polarizing powers depend on the power of its charge. Smaller atoms have their charges more concentrated in a smaller region so their polarizing power is stronger.
by jessicahe4Elavelle
Sun Nov 11, 2018 5:54 pm
Forum: Bond Lengths & Energies
Topic: 7th edition 2D. 13 [ENDORSED]
Replies: 2
Views: 54

Re: 7th edition 2D. 13 [ENDORSED]

Yes, you should draw the Lewis structures first the way we always do it (counting valence electrons and following the octet rule) and see which structures contain single, double or triple bonds. The single bonds have the greatest length followed by double and then triple bonds.
by jessicahe4Elavelle
Sun Nov 11, 2018 5:35 pm
Forum: Coordinate Covalent Bonds
Topic: coordinate covalent bond
Replies: 2
Views: 36

Re: coordinate covalent bond

A coordinate covalent bond is a bond in which one atom provides both electrons in a shared pair for both atoms.
by jessicahe4Elavelle
Sun Nov 04, 2018 12:32 pm
Forum: Trends in The Periodic Table
Topic: Question 2.75
Replies: 2
Views: 42

Re: Question 2.75

The s-block elements are all located in Group 1 and 2 and they all contain 1 or 2 electrons in their outer shell. They have lower ionization energies so they have the tendency of losing electrons more readily and react with other elements.
by jessicahe4Elavelle
Sun Nov 04, 2018 12:28 pm
Forum: Lewis Structures
Topic: Question 3.55 (Sixth Edition)
Replies: 6
Views: 43

Re: Question 3.55 (Sixth Edition)

Radicals are molecules that contain one unpaired electron. To answer this question it would be best if you draw the Lewis structures for which one and see which molecule has an unpair electron. You can also identify them by the fact that their number of valence electrons is odd (meaning that at leas...
by jessicahe4Elavelle
Fri Nov 02, 2018 8:17 pm
Forum: Electronegativity
Topic: ionic vs. covalent bonding
Replies: 2
Views: 48

Re: ionic vs. covalent bonding

Doctor Lavelle says that in these cases we cannot determine directly whether the two atoms will engage in covalent or ionic bonding through that simple rule, and we have to look at the specific cases.
by jessicahe4Elavelle
Sun Oct 28, 2018 6:17 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 1E 25)
Replies: 2
Views: 40

Re: 1E 25)

I think we should know on a general level. Just remember that alkali metals are in group 1. Group 2 are the alkaline earth metals, from group 3 to 12 are transition metals and group 17 contains the Halogens.
by jessicahe4Elavelle
Sun Oct 28, 2018 6:00 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Z effective 2.37
Replies: 1
Views: 30

Re: Z effective 2.37

The Zeff is the net positive charge that valence electrons experience from the protons in the nucleus. (a) is false because Zeff is largely dependent on the number of electrons in the atom. This is because the electrons in lower energy levels can shield electrons in higher energy orbitals thus decre...
by jessicahe4Elavelle
Sun Oct 28, 2018 2:42 pm
Forum: Ionic & Covalent Bonds
Topic: Friday 10/26/18 lecture
Replies: 4
Views: 58

Re: Friday 10/26/18 lecture

I am attaching my notes from the lecture down below. I hope that helps!

IMG_1094.jpg

IMG_1095.jpg

IMG_1092.jpeg
by jessicahe4Elavelle
Sun Oct 14, 2018 4:05 pm
Forum: Administrative Questions and Class Announcements
Topic: Test #2
Replies: 3
Views: 113

Test #2

What topics will the test next week (Test 2) cover? Only the Quantum World?
by jessicahe4Elavelle
Sun Oct 14, 2018 3:24 pm
Forum: General Science Questions
Topic: Chemistry Community Posts
Replies: 8
Views: 227

Re: Chemistry Community Posts

A friend of mine asked the TA and he said that extra posts do not roll over the following week.
by jessicahe4Elavelle
Sun Oct 14, 2018 3:22 pm
Forum: Significant Figures
Topic: When to round the answers to significant figures
Replies: 11
Views: 205

Re: When to round the answers to significant figures

You should keep as many significant figures as possible when doing your calculations (I usually keep at least 6 decimal places) and then round everything at the very end. Hope this helps
by jessicahe4Elavelle
Sun Oct 14, 2018 3:02 pm
Forum: Photoelectric Effect
Topic: Photoelectric Effect Post Module Questions
Replies: 2
Views: 40

Re: Photoelectric Effect Post Module Questions

I think it is better to say particle model. A photon is basically a quantized particle of light.
by jessicahe4Elavelle
Sun Oct 07, 2018 9:10 pm
Forum: Molarity, Solutions, Dilutions
Topic: Fundamentals E.15
Replies: 3
Views: 111

Re: Fundamentals E.15

The M is an unidentified metal that you have to find. The problem gives you the molar mass of M(OH)2 so what you have to do is subtract the molar mass of OH2 off of the molar mass of the entire thing to find the metal M. After doing the calculation you will find that the molar mass of the metal is 4...
by jessicahe4Elavelle
Sun Oct 07, 2018 7:11 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Forumula Units?
Replies: 2
Views: 81

Re: Forumula Units?

I think that formula units and molecules are pretty much interchangeable, but formula units refer to ionic compounds like NaCl while molecules refer to molecular compounds. Atoms, instead, are used for single elements or ions.
by jessicahe4Elavelle
Sun Oct 07, 2018 6:26 pm
Forum: Significant Figures
Topic: Sig Fig in Relation to Zero
Replies: 3
Views: 94

Re: Sig Fig in Relation to Zero

There are 4 major rules regarding zeros and significant figures. 1. Zeros that are between two non-zero digits are significant. (ex. 303 - 3 significant figures) 2. Leading zeros are not significant. (ex. 0.4 - 1 significant figure) 3. Trailing zeros that are to the right of the decimal are signific...
by jessicahe4Elavelle
Sun Oct 07, 2018 1:55 pm
Forum: Limiting Reactant Calculations
Topic: Limiting Reactants M19
Replies: 4
Views: 92

Re: Limiting Reactants M19

How do we get the info that the composition of caffeine is c(8)H(10)N(4)O(2)? I thought that that was what we were trying to find.

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