Search found 62 matches

by 904936893
Sat Mar 16, 2019 10:57 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Activated Complex
Replies: 1
Views: 94

Re: Activated Complex

The activated complex I believe is what forms when molecules in a reaction collide in the right orientation to form products. How temperature affects this is that with increasing temperature, there are more collisions, with higher energy (and are able to overcome the energy barrier/activation energy...
by 904936893
Sat Mar 16, 2019 10:53 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: How to know which conducting element to add?
Replies: 3
Views: 107

Re: How to know which conducting element to add?

I'm pretty sure you can always add Platinum if you're missing an inert conductor on one side of the cell. I think you can add any solid metal as your conductor, but Platinum is what is standard. I hope this helps!
by 904936893
Sat Mar 16, 2019 10:46 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: different types of cells
Replies: 1
Views: 95

Re: different types of cells

I'm pretty sure voltaic and galvanic cell are the same (convert chemical energy to electrical energy, standard cell potential is always positive). Electrolytic cells convert electrical energy to chemical energy, and use spontaneous reactions to drive nonspontaneous reactions, the standard cell poten...
by 904936893
Sun Mar 10, 2019 4:26 pm
Forum: General Rate Laws
Topic: Writing Rate Laws
Replies: 3
Views: 47

Re: Writing Rate Laws

Maybe it is because when we are looking at reaction rates, we are looking at initial concentrations, when a reaction first starts. At this point in time no products have been formed, so they would not be included in the rate law, since they are not affecting the rate.
by 904936893
Sun Mar 10, 2019 4:23 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: The temperature reaction changes from spontaneous to nonspontaneous?
Replies: 1
Views: 43

Re: The temperature reaction changes from spontaneous to nonspontaneous?

You use the equation delta G = delta H - Tdelta S, and by plugging in your known values of delta H and S, you make G equal to zero and solve for T. That temperature, T (when G = 0) is when the reaction changes from nonspontaneous to spontaneous and vice versa.
by 904936893
Sun Mar 10, 2019 4:21 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalysts
Replies: 6
Views: 69

Re: Catalysts

I believe that by lowering the activation energy of a reaction, catalysts increase the speed of a reaction.
by 904936893
Sun Mar 03, 2019 6:56 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Pt inert electrode
Replies: 9
Views: 155

Re: Pt inert electrode

Athena L 1B wrote:Is Pt(s) the only other substance you would add in any scenario?

I think you can add any inert conductor (I think any solid metal), but Pt(s) is just the most commonly used.
by 904936893
Sun Mar 03, 2019 6:53 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: delta G = 0 ??
Replies: 5
Views: 154

Re: delta G = 0 ??

delta G standard is equal to zero when K=1, which I believe is very rare.
by 904936893
Sun Mar 03, 2019 6:50 pm
Forum: Administrative Questions and Class Announcements
Topic: Class Curve
Replies: 11
Views: 380

Re: Class Curve

I would assume 50-72% or so would be a C- and then the rest of the grading would be on a normal scale. I'm sure you could ask your TA though, or professor Lavelle.
by 904936893
Sun Feb 24, 2019 3:57 pm
Forum: Balancing Redox Reactions
Topic: Test 2 Material
Replies: 13
Views: 182

Re: Test 2 Material

Does anyone know if we will be asked to draw a cell diagram for Test 2?
by 904936893
Sun Feb 24, 2019 3:56 pm
Forum: Balancing Redox Reactions
Topic: Balancing Redox Reactions in Acidic / Basic Conditions
Replies: 1
Views: 45

Balancing Redox Reactions in Acidic / Basic Conditions

Can someone explain how to balance redox reactions in acidic or basic conditions? How do you know what to use to balance out everything???
by 904936893
Sun Feb 24, 2019 3:51 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Inert Conductors
Replies: 3
Views: 67

Inert Conductors

Can someone please explain what inert conductors are, and why they are helpful in redox reactions? Thank you
by 904936893
Sun Feb 17, 2019 11:51 am
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Isolated system
Replies: 10
Views: 218

Re: Isolated system

The internal energy of an isolated system is constant, and the entropy of an isolated system increases in the course of any spontaneous change, according to the first and second laws of thermodynamics.
by 904936893
Sun Feb 17, 2019 11:48 am
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: Derivations
Replies: 3
Views: 144

Re: Derivations

The equation is called the Van't Hoff Equation, and it helps show temperature dependence of K! It can be used to find K at different temperatures.
by 904936893
Sun Feb 17, 2019 11:44 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Differences in Gibbs Free Energy
Replies: 3
Views: 39

Re: Differences in Gibbs Free Energy

I think Dr. Lavelle also mentioned that when K<1, enthalpy dominates over entropy, and the reaction will be non-spontaneous
by 904936893
Sun Feb 17, 2019 11:34 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: At Equilibrium G
Replies: 6
Views: 101

Re: At Equilibrium G

If K = 0, is the reaction at equilibrium?
by 904936893
Sun Feb 17, 2019 11:32 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Calculating Standard Entropy of Fusion
Replies: 2
Views: 54

Re: Calculating Standard Entropy of Fusion

Because at the freezing temperature is when it goes from liquid to solid, so it's also the melting point, where it goes from solid to liquid. So you use the same temperature.
by 904936893
Wed Feb 13, 2019 3:34 pm
Forum: Administrative Questions and Class Announcements
Topic: Lyndon's HOTDOG MIDTERM REVIEW SESSION!! FINALLY!
Replies: 49
Views: 2630

Re: Lyndon's HOTDOG MIDTERM REVIEW SESSION!! FINALLY!

dgerges 4H wrote:I also got that the other part of w=9.12 from w=-pdv. so i got a total of 11.45kj or 1.145x10^5j for w. is this correct?

I also got that for work
by 904936893
Sun Feb 03, 2019 9:39 pm
Forum: Phase Changes & Related Calculations
Topic: Phase Changes
Replies: 2
Views: 40

Re: Phase Changes

It only doesn't change temperature when the phase change is occurring, because the energy being provided to or leaving the system is going towards breaking /forming bonds, not increasing or decreasing the temperature. Once the phase change is finished, then the energy will go towards changing temper...
by 904936893
Sun Feb 03, 2019 9:36 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Midterm [ENDORSED]
Replies: 48
Views: 909

Re: Midterm [ENDORSED]

Definitely doing all the homework problems assigned, because I know sometimes textbook problems are put on the midterm / final verbatim.
by 904936893
Sun Feb 03, 2019 9:34 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hess's Law
Replies: 2
Views: 53

Re: Hess's Law

I know in the textbook sometimes just the final equation is given and not the intermediate equations that must be be set up and manipulated to solve for the final equation, but I'm pretty sure for this class that the intermediate equations and their enthalpies will be given in the problem so that al...
by 904936893
Mon Jan 28, 2019 9:18 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hess's Law (Method 1)
Replies: 4
Views: 95

Re: Hess's Law (Method 1)

In addition to that, sometimes you'll need to multiply one of the delta H's if the final reaction requires two moles of one of the substances, and the given delta H is for one mole. So you have to make sure that the reactions match with the amount of moles required in the final reaction, if that mak...
by 904936893
Mon Jan 28, 2019 9:15 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: When to use which method for calculating reaction enthalpies
Replies: 4
Views: 60

When to use which method for calculating reaction enthalpies

How do you know which of the three methods to use when given a specific problem? Like when would you use Hess's Law vs. Bond Enthalpies vs. Standard Enthalpies of formation?
by 904936893
Mon Jan 28, 2019 9:12 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond Enthalpies
Replies: 7
Views: 76

Bond Enthalpies

Why are bond enthalpies the least accurate way of measuring reaction enthalpies?
by 904936893
Sun Jan 20, 2019 7:11 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Removing products
Replies: 10
Views: 131

Re: Removing products

I believe the only way to change K is to change the temperature of a reaction.
by 904936893
Sun Jan 20, 2019 7:10 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Bars vs. Molarity
Replies: 5
Views: 69

Re: Bars vs. Molarity

bars I believe is a unit of pressure, like atm, so if given this, you would be finding Kp, versus when given molarity, that is the concentration of a molecule, and you would find Kc.
by 904936893
Sun Jan 20, 2019 7:08 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: endo/exothermic rxns
Replies: 5
Views: 80

Re: endo/exothermic rxns

The easiest way to tell if a reaction is endothermic or exothermic is by the change in enthalpy (delta H), which I believe will be given for these types of reactions.
by 904936893
Sun Jan 13, 2019 2:28 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 11.49 6th Edition
Replies: 2
Views: 31

Re: 11.49 6th Edition

I believe it is because the molar concentration of a pure substance, such as a liquid or solid, does not change in a reaction! So, since it doesn't change, it wouldn't affect the ICE table!
by 904936893
Sun Jan 13, 2019 9:54 am
Forum: Ideal Gases
Topic: Denoting brackets/parentheses
Replies: 9
Views: 106

Re: Denoting brackets/parentheses

I'm pretty sure brackets indicate concentration so for Kc [H20] indicates the concentration of water, but with Kp you have (PCl2). You don't need brackets to indicate concentration for this because the P indicates the pressure of the gas. I hope this helps!
by 904936893
Mon Dec 03, 2018 9:12 am
Forum: Naming
Topic: Naming the Shape
Replies: 6
Views: 113

Re: Naming the Shape

I would say the easiest way is just to draw out the compound, especially if it is not too large of a molecule. It's also probably the easiest way to check your answer.
by 904936893
Mon Dec 03, 2018 9:09 am
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Bronsted vs Lewis
Replies: 2
Views: 45

Re: Bronsted vs Lewis

I think in class it was stated that either definition will work for this class, and both sufficiently cover what we need to know.
by 904936893
Mon Dec 03, 2018 9:08 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Orbitals
Replies: 3
Views: 153

Re: Orbitals

I don't think you have to memorize the different energy values of the different orbitals. Just know that s is always the lowest energy, and then p. Once you get to the fourth row, s fills up first because its a lower energy, but then once one electron is in the 3d orbital, that becomes your lowest, ...
by 904936893
Sun Nov 25, 2018 6:02 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: hydrogen bonding
Replies: 4
Views: 89

Re: hydrogen bonding

Hydrogen bonding is a type of dipole-dipole bond, that is stronger than other dipole-dipole bonds, as well as ion-dipole, dipole-induced dipole, and van der Waals / London dispersion forces. Hydrogen bonds can only occur between a hydrogen atom and a N, O, or F atom, because these atoms have very hi...
by 904936893
Sun Nov 25, 2018 5:57 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
Replies: 4
Views: 96

Re: induced-dipole

molecules held in a polar covalent bond have dipoles. An induced dipole can happen to an element in a nonpolar covalent bond, when near a polar molecule, because the partial charge of that molecule will repel the electrons in the nonpolar molecule
by 904936893
Sun Nov 18, 2018 9:46 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: Dipole moments
Replies: 1
Views: 60

Re: Dipole moments

I think you would have to draw out the Lewis Structures and then add in the arrows for the dipole moments, making the arrows larger or smaller depending on the difference in electronegativity between the atoms being bonded. From that image you would look at the directions the arrows are pointing, an...
by 904936893
Sun Nov 18, 2018 9:39 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Polar or nonpolar [ENDORSED]
Replies: 1
Views: 42

Re: Polar or nonpolar [ENDORSED]

I think for molecules like that, it is possible for it to have different isomers which are both polar and nonpolar. My TA did an example in discussion with C2F2H2, a similar molecule, and there were three isomers, one of which was nonpolar because the polarities cancel each other out. This isomer th...
by 904936893
Sun Nov 18, 2018 9:35 am
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Sigma and Pi Bonds
Replies: 5
Views: 119

Re: Sigma and Pi Bonds

The first bond that two atoms make is a sigma bond. If two atoms have a double bond (i.e O=O) then they will have one sigma bond and one pi bond. If two atoms have a triple bond, like Nitrogen with Nitrogen, then there will be one sigma bond, and two pi bonds. So if two atoms are bound by more than ...
by 904936893
Sun Nov 11, 2018 7:12 pm
Forum: Ionic & Covalent Bonds
Topic: Bond Length
Replies: 3
Views: 44

Re: Bond Length

I think it would be given, but in general you should just know conceptually that single bonds are the longest (and weakest), and then double bonds are shorter, and triple bonds are the shortest (and the strongest).
by 904936893
Sun Nov 11, 2018 10:15 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 1
Views: 132

Re: Bond Angles

I think if another molecule/element was nearby it would only shift the electrons within the molecule, through repulsion of charges, but not affect the actual angles within the molecule.
by 904936893
Sun Nov 11, 2018 10:14 am
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Polar Bonds with Cations and Anions
Replies: 1
Views: 126

Re: Polar Bonds with Cations and Anions

I think if it involves cations and anions its an ionic bond, and polar bonding refers to covalent bonds between elements in their neutral states. The bond is only polar because elements have different electronegativities.
by 904936893
Sat Nov 03, 2018 11:32 pm
Forum: Properties of Light
Topic: 3b on Quantum Test
Replies: 2
Views: 113

Re: 3b on Quantum Test

The intensity of the light will decrease (i.e. the lamp will be dimmer). This is because there are now atoms that have a higher threshold energy in the lamp. So, the voltage energy being emitted is not sufficient enough to excite these atoms with a higher threshold energy, to the next energy level, ...
by 904936893
Sat Nov 03, 2018 11:27 pm
Forum: Trends in The Periodic Table
Topic: Second and First Ionization Energy
Replies: 2
Views: 42

Re: Second and First Ionization Energy

Ionization energy is the energy it takes to remove an electron from an element. Once one electron is removed, the element has an overall positive charge. Electrons are negative, so they are therefore more attracted to this positively charged element, making them harder to remove.
by 904936893
Sat Nov 03, 2018 11:25 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Subshells
Replies: 2
Views: 52

Re: Subshells

It does have access to its d and f subshells, those shells just aren't filled. This is why elements after row 2 can have an expanded octet (more than 8 electrons), because n=3, which means that l can equal 0,1, or 2 (s, p, and d orbital). Even though none of the elements in row three have any electr...
by 904936893
Sat Nov 03, 2018 11:21 pm
Forum: Trends in The Periodic Table
Topic: Periodic trends of elements diagonal to one another
Replies: 1
Views: 48

Re: Periodic trends of elements diagonal to one another

I believe that going down a group has more significance than across a period for the trends. For example, with atomic radius, Arsenic would have a larger radius because it has the 4s 3d and 4p orbitals in addition to the orbitals in fluorine. The same goes for Selenium and Iodine. Although Iodine's ...
by 904936893
Sat Nov 03, 2018 11:13 pm
Forum: Quantum Numbers and The H-Atom
Topic: Quantum number Ms
Replies: 3
Views: 192

Re: Quantum number Ms

I don't think we would be able to tell. If a question were to come up on quantum numbers, I think all you would need to know about ms is that it can only be +1/2 or -1/2. Whether it is + or - I believe is arbitrary for this class.
by 904936893
Sat Nov 03, 2018 11:09 pm
Forum: Lewis Structures
Topic: Lewis structures of compounds
Replies: 2
Views: 27

Re: Lewis structures of compounds

I think that if the question was assigned, it would be better just to understand it, in case a question on molecules comes up. I believe all of those compounds are salts, so it would make sense that the Lewis structures were written like ionic compounds.
by 904936893
Sat Nov 03, 2018 11:05 pm
Forum: Octet Exceptions
Topic: Copper ion electron structure
Replies: 3
Views: 101

Re: Copper ion electron structure

Once there is an electron in the 3d orbital, it has a lower energy than the 4s orbital, meaning that the electron configuration would be written as 3d1 4s2. Copper's neutral state electron configuration is 3d10 4s1. Since electrons are removed from the highest energy level first, the electron in the...
by 904936893
Sat Nov 03, 2018 11:02 pm
Forum: Octet Exceptions
Topic: Ions and Exceptions to the Octet Rule
Replies: 3
Views: 71

Re: Ions and Exceptions to the Octet Rule

Zn+ having an electron removed from the 4s orbital isn't an exception to a rule. Once an electron is in the 3d orbital, that orbital has a lower energy than 4s, which would mean the electron configuration is written as 3d1 4s2. Since electrons are removed from the highest energy level (the level wri...
by 904936893
Sat Oct 27, 2018 1:47 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Radial Distribution Function
Replies: 2
Views: 85

Re: Radial Distribution Function

I believe r is the radius and R is the radial wavefunction, which indicates how the wavefunction varies as a particle moves away from the nucleus in any direction. It is a part of the wavefunction equation where Ψ(r, θ , ф) = R(r) x Y(θ, ф)
by 904936893
Sat Oct 27, 2018 1:39 pm
Forum: *Particle in a Box
Topic: Application
Replies: 3
Views: 372

Re: Application

I believe there is an example in the textbook (6th edition) on page 23. It goes through how to calculate the energies of a particle in a box.
by 904936893
Sat Oct 27, 2018 1:36 pm
Forum: Trends in The Periodic Table
Topic: Atomic Radius
Replies: 7
Views: 138

Re: Atomic Radius

When an electron is removed, the atom becomes a cation, or a positively charged ion. This positive charge in the atom makes the electrons more attracted to it, and therefore harder to remove.
by 904936893
Sun Oct 21, 2018 4:45 pm
Forum: Properties of Light
Topic: Intensity vs energy
Replies: 6
Views: 138

Re: Intensity vs energy

Intensity is increasing the amplitude of the wavelength, so making it larger or smaller. When light is acting as a particle, increasing the intensity is just increasing the amount of photons (not the energy per photon). The reason why intensity was significant was because in the photoelectric experi...
by 904936893
Thu Oct 18, 2018 6:46 pm
Forum: Photoelectric Effect
Topic: units
Replies: 12
Views: 217

Re: units

Wavelength is measured in meters, so always convert to meters! Energy is in Joules. eV, Watts, and cal can all be converted into Joules (the conversion are in the back of the book). So yes, always convert back to meters or Joules
by 904936893
Thu Oct 18, 2018 6:44 pm
Forum: *Black Body Radiation
Topic: Black Body Radiation
Replies: 1
Views: 182

Re: Black Body Radiation

Black body radiation is an object that absorbs ALL radiation at all wavelengths. To the extent of my knowledge, it has no real equivalent in everyday life, and the closest example would be something like a black hole. I do not believe that we need to know about black body radiation for this course.
by 904936893
Sun Oct 14, 2018 9:11 am
Forum: Properties of Light
Topic: Moles in photoelectric effect? [ENDORSED]
Replies: 2
Views: 45

Re: Moles in photoelectric effect? [ENDORSED]

If the threshold energy is given in Joules/mole, you just have to divide by Avogadro's number (6.022x10^23) in order to cancel the units. Then you will just have Joules and can use that number in your equations.
by 904936893
Sun Oct 14, 2018 9:08 am
Forum: Properties of Light
Topic: E=hv
Replies: 13
Views: 202

Re: E=hv

Tamera Scott 3L wrote:I've also seen E=hf once, does anyone know if that is the same as E=hv?

v is frequency, so I believe f would just be another way to denote frequency.
by 904936893
Tue Oct 09, 2018 9:44 am
Forum: Einstein Equation
Topic: Einstein's Equation: E=hv
Replies: 11
Views: 284

Re: Einstein's Equation: E=hv

the equation shows that the energy per photon is proportional to frequency. As frequency increases, so does the energy per photon. Planck's constant, h, is the proportionality constant that equates v to E.
by 904936893
Sat Oct 06, 2018 1:22 pm
Forum: Properties of Electrons
Topic: Light and Electrons
Replies: 1
Views: 59

Light and Electrons

In one of the module's Professor Lavelle mentions that light's affect on electrons is more noticeable because they have a much smaller mass than protons/neutrons. However, would the position of the electron's in the atom also be significant, because they are located in orbitals outside the nucleus?
by 904936893
Sat Oct 06, 2018 12:54 pm
Forum: Significant Figures
Topic: Rounding numbers ending in 5
Replies: 9
Views: 128

Re: Rounding numbers ending in 5

I believe it is more standard to round up with numbers ending in 5
by 904936893
Sat Oct 06, 2018 12:51 pm
Forum: SI Units, Unit Conversions
Topic: Avogadro's Number [ENDORSED]
Replies: 11
Views: 406

Re: Avogadro's Number [ENDORSED]

So when asked for atoms of a molecule we can multiply by the mols by Avogadro's number to get number of atoms, but I do not understand how to get molecules from mols? You can do the same thing to get molecules, because moles is just a unit of "something" not just an atom, but also molecul...
by 904936893
Sat Oct 06, 2018 12:47 pm
Forum: Properties of Light
Topic: Electric and Magnetic Fields
Replies: 1
Views: 112

Electric and Magnetic Fields

When professor Lavelle was talking about the oscillation of electric and magnetic fields, are both important when looking at electromagnetic radiation / light? Like what is the significance of each? I know he addressed the speed of the electric field, and it's importance in different ranges of visib...

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