Search found 60 matches
- Mon Mar 11, 2019 9:10 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Activation energy and k
- Replies: 2
- Views: 331
Activation energy and k
Why is it that when the activation energy increases, k decreases?
- Sun Mar 10, 2019 9:07 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Elementary Steps
- Replies: 1
- Views: 225
Elementary Steps
What is the difference between elementary steps and all other steps? Is there a significance in this difference?
- Sun Mar 10, 2019 8:52 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Microscopic Reversibility
- Replies: 2
- Views: 323
Re: Microscopic Reversibility
Another definition of microscopic reversibility that Dr. Lavelle mentioned in lecture was when one assumes that the reaction has the same intermediates (same pathway) in both the forward and reverse reactions.
- Wed Mar 06, 2019 6:42 pm
- Forum: Zero Order Reactions
- Topic: Slope = -k
- Replies: 3
- Views: 444
Slope = -k
Is there a specific reason both zero order reactions and first order reaction graphs have a slope of -k, while the slope of a second order reaction is k?
- Wed Mar 06, 2019 10:44 am
- Forum: First Order Reactions
- Topic: Half-Life 1st Order Reaction
- Replies: 6
- Views: 633
Half-Life 1st Order Reaction
Is the equation t1/2 = 0.693/k valid for all first order reactions? And if so, it it because the initial concentration of A cancel out and leave ln(1/2)?
- Wed Mar 06, 2019 10:39 am
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: n and m
- Replies: 3
- Views: 417
n and m
I am confused as to the meaning of n and m concerning the overall reaction order. In lecture, we used an examples with NH4+ and NO2-, and we determined that rate 2/rate 1 = 2 = 2.0^m, therefore m is 1. I don't know where the 2.0 value came from, or how to determine n.
- Sun Feb 24, 2019 5:00 pm
- Forum: Balancing Redox Reactions
- Topic: Oxidation
- Replies: 4
- Views: 535
Oxidation
Why is oxidation called that? Is there a specific reasoning that the loss of electrons is called oxidation (is it related to oxygen)?
- Sun Feb 24, 2019 4:52 pm
- Forum: Balancing Redox Reactions
- Topic: Oxygen Oxidation Number
- Replies: 3
- Views: 413
Oxygen Oxidation Number
Is the oxidation number of oxygen always -2? My teacher in high school told me that, but I am not sure if that is always true because difference molecules can affect the oxidation number of oxygen differently.
- Sun Feb 24, 2019 4:47 pm
- Forum: Balancing Redox Reactions
- Topic: Oxidizing and Reducing Agent
- Replies: 3
- Views: 389
Re: Oxidizing and Reducing Agent
In addition to what the other comments say, you can typically determine the oxidizing and reducing agent by first determining which molecules are oxidized and reduced. Therefore, the molecule that is being reduced is also the oxidizing agent for the other, and the molecule that is being oxidized is ...
- Mon Feb 18, 2019 12:25 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: K and Gibbs Free Energy
- Replies: 2
- Views: 323
K and Gibbs Free Energy
In lecture we discussed how if K is less than 1, then deltaG is positive, and visa versa. When K is less than one, there are more reactants than products at equilibrium, so would the reaction always shift right/favor the forward reaction when deltaG is positive?
- Mon Feb 18, 2019 12:13 pm
- Forum: Van't Hoff Equation
- Topic: Temperature Dependence of K
- Replies: 5
- Views: 526
Temperature Dependence of K
I am a little confused on the meaning of temperature dependence of K in the Van't Hoff equation. Does is just mean that the value of K can change depending on the temperature?
- Mon Feb 18, 2019 12:04 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Spontaneity
- Replies: 4
- Views: 431
Re: Spontaneity
Another way of telling if the reaction is spontaneous is if the change in entropy of the universe is positive (deltaS universe). This is because deltaS universe is equal to -(deltaG)/T. As long as deltaG is negative, the resulting value which equals deltaS universe will be positive, since the temper...
- Sat Feb 09, 2019 5:32 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Positive or Negative Entropy Change
- Replies: 2
- Views: 329
Positive or Negative Entropy Change
When calculating the change in entropy, do you always have to analyze the heat flow to determine if it is positive or negative? So, if the surroundings gain heat while the system loses it, would deltaS of the system be negative and deltaS of the surroundings be positive?
- Sat Feb 09, 2019 5:28 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: DeltaS=kBlnW
- Replies: 3
- Views: 607
Re: DeltaS=kBlnW
This equation, called the Boltzmann formula, is used to calculate deltaS (statistical entropy). kB is Boltzmann's constant, 1.381 x 10^-23 J/K, which is multiplied by the natural logarithm of W, degeneracy. Degeneracy is the number of ways that atoms/molecules can be arranged with the same total ene...
- Sat Feb 09, 2019 5:12 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: 4G. 3 7th edition
- Replies: 1
- Views: 225
Re: 4G. 3 7th edition
This question was recently answered in the same topic, but the answer is that the degeneracy of COF2 allows for a greater disorder and more possible arrangements of atoms, compared to BF3 since there is only one arrangement for that. Since there is higher degeneracy is COF2, it has a higher molar en...
- Tue Feb 05, 2019 3:48 pm
- Forum: Calculating Work of Expansion
- Topic: Work on Phases of Matter
- Replies: 2
- Views: 346
Work on Phases of Matter
When the energy of a system changes by doing work on it, is it only possible for gases, or also liquids and solids?
- Tue Feb 05, 2019 11:22 am
- Forum: Calculating Work of Expansion
- Topic: Work vs Degeneracy
- Replies: 2
- Views: 325
Work vs Degeneracy
Is there a relationship between work and degeneracy because they both use the same variable, w, or is this just a coincidence?
- Tue Feb 05, 2019 11:11 am
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Entropy
- Replies: 2
- Views: 267
Entropy
Why don't deltaU or deltaH fully describe the system? So, why is entropy necessary to describe the system and what information does it provide?
- Mon Jan 28, 2019 11:44 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Cv versus Cp
- Replies: 4
- Views: 455
Cv versus Cp
In lecture, it said that Cp > Cv. Is this always true, or was that just for one example? If it is always true, why?
- Mon Jan 28, 2019 11:25 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Cv and Cp
- Replies: 3
- Views: 375
Re: Cv and Cp
If Cv or Cp is not specified, it helps to know that Cv (molar heat capacity of a gas at constant volume) often uses a bomb calorimeter in which the volume remains constant and there is pressure buildup, hence the name. Cp (molar heat capacity of a gas at constant pressure) uses a constant pressure c...
- Mon Jan 28, 2019 11:15 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: HW Week4
- Replies: 4
- Views: 450
Re: HW Week4
So far in lecture, we have gone over most of 4D and 4C. 4D goes over standard reaction enthalpies, combustion, and Hess's Law, so the homework from that section should be helpful. 4C goes over some of what we covered today in lecture, such as heat capacities.
- Tue Jan 22, 2019 11:43 am
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: ignoring x
- Replies: 10
- Views: 829
Re: ignoring x
You only ignore X when it is being added or subtracted from a number, because X is so small that it barely makes any difference to the resulting value. This occurs when K is less than 10^-3. If X is by itself or being squared on the numerator of a fraction, don't assume X is 0 and instead continue s...
- Tue Jan 22, 2019 11:38 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Changing Pressure
- Replies: 6
- Views: 677
Changing Pressure
Is there any difference in the direction of the reaction when pressure is changed by altering the volume compared to adding inert gas?
- Tue Jan 22, 2019 11:23 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Conceptual questions
- Replies: 6
- Views: 463
Re: Conceptual questions
Jordan Lo 2A wrote:Is test 1 the entire outline 2? I could be wrong but I don't remember going over polyprotic acids (last couple exercises in 6th edition) or examples (last bullet points under concepts)
At office hours this morning, my TA said we did not need to know polyprotic acids for Quiz 1.
- Mon Jan 14, 2019 11:07 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Kw
- Replies: 2
- Views: 218
Kw
What does Kw represent? We used this term in lecture today concerning water, but I didn't know the specific meaning of Kw.
- Mon Jan 14, 2019 10:56 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Change in K
- Replies: 2
- Views: 249
Change in K
In lecture, why was a change in temperature described as a change in K, while a change in concentration and a change in pressure is described as no changes in K?
- Sun Jan 13, 2019 2:53 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Effect of Volume Given Equal Moles
- Replies: 2
- Views: 137
Re: Effect of Volume Given Equal Moles
When the volume decreases and the number of moles of gas on both sides of the reaction are equal, the reaction does not shift and it is unaffected. This is because the number of moles of reactants and products are equal, so the reaction does not favor either the forward or reverse reaction. If the v...
- Thu Jan 10, 2019 10:55 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: K=1
- Replies: 5
- Views: 354
K=1
Is there a certain significance to when K is equal to 1? In the lecture it was discussed that it is rare when K = 1, but I was not sure if it meant anything specific concerning reactants and products.
- Thu Jan 10, 2019 10:51 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: PArtial pressure= concentration?
- Replies: 2
- Views: 797
Re: PArtial pressure= concentration?
The partial pressure of a gas is not the same thing as finding the equilibrium concentration, but they are related. Partial pressure = (concentration)*R*T because it is derived from the ideal gas law, PV=nRT. When solving for pressure, P, you divide both sides by V, volume, and n/V equates to concen...
- Tue Jan 08, 2019 5:13 pm
- Forum: Ideal Gases
- Topic: Solid/Liquid in Reactions
- Replies: 4
- Views: 194
Solid/Liquid in Reactions
Why is it that solids and liquids are not included in the K expression? Is there a specific reason or is it a general rule?
- Thu Nov 29, 2018 6:54 pm
- Forum: Bronsted Acids & Bases
- Topic: HCl Acid
- Replies: 4
- Views: 401
HCl Acid
In lecture we discussed how HCl in an aqueous state is hydrochloric acid. So, if we do not specify that HCl is aqueous, is it not considered an acid?
- Thu Nov 29, 2018 6:41 pm
- Forum: Naming
- Topic: Brackets in Coordinate Compound Formula
- Replies: 2
- Views: 239
Brackets in Coordinate Compound Formula
When looking at the formula for coordinate compounds, part of the formula is inside brackets while other parts are not. I was wondering what the difference is between those two parts and how to distinguish between them. Thanks!
- Thu Nov 29, 2018 1:58 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Ligands
- Replies: 2
- Views: 346
Re: Ligands
Ligands are ions or molecules that bind to a central atom which makes up the coordination sphere. Ligands are the Lewis base in the interaction because they supply both electrons within the coordinate bond. They are significant because when the ligands are bound with the central atom, the transition...
- Mon Nov 19, 2018 1:32 pm
- Forum: Hybridization
- Topic: Perpendicular Bond Angle
- Replies: 1
- Views: 179
Perpendicular Bond Angle
At the end of lecture today, we went over how an unhybridized p-orbital is at a perpendicular angle to the hybridized orbital. Do 90 degree bond angles always form between pi-bonds and an unhybridized p-orbital, or was it just this one example?
- Mon Nov 19, 2018 1:23 pm
- Forum: Hybridization
- Topic: hybridization
- Replies: 2
- Views: 299
Re: hybridization
Hybridization is related to bond strength such that the bond strength increases as the s character increases in the bond. Therefore, the sp hybridization has a stronger bond strength than sp2, sp2 is stronger than sp3, and etc. This is because the s-orbital is closer to the nucleus than p or d-orbit...
- Mon Nov 19, 2018 1:08 pm
- Forum: Hybridization
- Topic: Electron Density Shape
- Replies: 2
- Views: 141
Electron Density Shape
In lecture today, Dr. Lavelle mentioned that, based on electron density, the shape of ammonia is trigonal pyramidal. But, this is not actually considered the molecule's shape. Can someone please explain this? Thanks!
- Wed Nov 14, 2018 5:39 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Electrons and VSEPR
- Replies: 4
- Views: 369
Electrons and VSEPR
Do lone pair electrons influence the name of the molecular shape? In the molecular geometries such as seesaw, don't lone pairs affect the name given to it, or is it just the bound electrons that influence it?
- Wed Nov 14, 2018 5:24 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: London Dispersion Forces
- Replies: 2
- Views: 522
Re: London Dispersion Forces
London Dispersion forces can have multiple names including induced dipole-induced dipole and Van der Waals forces. These forces are always present and attractive and occur when fluctuating electron distribution results in fluctuating dipoles. London Dispersion forces are the weakest because they inv...
- Wed Nov 14, 2018 1:50 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bond Angles
- Replies: 3
- Views: 301
Re: Bond Angles
The order of repulsion strength in bonds from strongest to weakest is: lone-lone pair, lone-bonding pair, bonding-bonding pair. Therefore, lone pairs have the most repulsion strength among electrons. This causes bond angles to decrease because the strength of the lone pairs force the bound pairs to ...
- Thu Nov 08, 2018 5:57 pm
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Polarizability and States of Matter
- Replies: 2
- Views: 521
Polarizability and States of Matter
I am a little confused as to the relationship between a molecule's polarizability and its state of matter (solid, liquid, gas). In class we discussed how molecules with high polarizability boil at a higher temperature, but I don't know why this happens. Could someone please explain?
- Thu Nov 08, 2018 5:50 pm
- Forum: Dipole Moments
- Topic: Induced Dipole
- Replies: 4
- Views: 337
Re: Induced Dipole
An induced dipole results from the interaction between a nonpolar molecule and another molecule, which can be very polar depending on the type of interaction. As the polar molecule moves closer to the non polar molecule, the distribution of charge in the polar molecule causes the arrangement of elec...
- Thu Nov 08, 2018 5:28 pm
- Forum: Ionic & Covalent Bonds
- Topic: Definition of a Covalent Bond
- Replies: 4
- Views: 447
Re: Definition of a Covalent Bond
A covalent bond is when two atoms share electrons to achieve a noble gas electron configuration, because that is the most stable state for molecules. Typically in covalent bonds, one shared electron comes from one atom and the second shared electron comes from the other atom. Meanwhile, a coordinate...
- Thu Nov 01, 2018 3:19 pm
- Forum: Lewis Structures
- Topic: Determining Lewis Structure
- Replies: 3
- Views: 240
Determining Lewis Structure
When you are trying to determine the lewis structure of a compound, how does the formal charge affect it? I remember learning that a compound is most stable when there is a neutral charge among all atoms, but I wasn't sure if the correct lewis structure is always the one with as many atoms having a ...
- Thu Nov 01, 2018 12:00 pm
- Forum: Ionic & Covalent Bonds
- Topic: Removing the second electron
- Replies: 8
- Views: 612
Re: Removing the second electron
Removing a second electron from an atom is much harder than removing the first electron because there is a higher electrostatic attraction. This is represented through ionization energies; the first ionization energy is the energy required to remove an electron, and the second ionization energy is t...
- Wed Oct 31, 2018 3:27 pm
- Forum: Lewis Structures
- Topic: Lewis Structure of BrF3 [ENDORSED]
- Replies: 3
- Views: 3038
Re: Lewis Structure of BrF3 [ENDORSED]
The lewis structure of BrF3 permits Br to have 10 valences electrons, which is above the octet rule of 8 valence electrons, because it is in period 3 or higher of the periodic table. Because Br is in period 4, it has an n value of n = 4. Therefore, l can be equal to 0, 1, 2, or 3. The l value of 2 c...
- Wed Oct 24, 2018 2:07 pm
- Forum: Trends in The Periodic Table
- Topic: Electron Affinity
- Replies: 2
- Views: 156
Re: Electron Affinity
Electron affinity and electronegativity are different, but they have a very similar trend across the periodic table. Electron affinity refers to the energy released when electrons are added to a gas phase atom, while electronegativity describes the the ability of an atom to attract a pair of bonded ...
- Wed Oct 24, 2018 11:34 am
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Pauli Exclusion Principle vs. Hund's Rule
- Replies: 2
- Views: 2436
Pauli Exclusion Principle vs. Hund's Rule
What is the difference between the Pauli Exclusion Principle and Hund's Rule? I was confused as to how these two rules affect the electron configuration of atoms and if we need to include these rules when writing out electron configurations. Thanks!
- Wed Oct 24, 2018 11:16 am
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Shielding effect
- Replies: 6
- Views: 1086
Re: Shielding effect
The shielding effect is how the inner electrons (in the lower energy levels) decrease the attractive pull of the nucleus on the outer electrons (in the highest energy levels). Therefore, the electron-electron repulsion between electrons on different energy levels reduces the electrostatic attraction...
- Wed Oct 17, 2018 7:29 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: variable l
- Replies: 2
- Views: 291
Re: variable l
The variable 'l' represents the orbital angular momentum quantum number, therefore it relates to the shape and type of orbital. The values of 'l' define the subshell that an electron belongs to, and there are 'n' different values of 'l' such that 'l' ranges from 0 to n-1. So, in the n=1 shell, 'l' i...
- Wed Oct 17, 2018 6:51 pm
- Forum: Photoelectric Effect
- Topic: Speed of Light
- Replies: 5
- Views: 409
Re: Speed of Light
In the problem we went over in class, the uncertainty in the electron's velocity was calculated, through the Heisenberg Indeterminacy equation, to be greater than the speed of light. This results in us recognizing that the model is incorrect because atoms only exist based on their physical parameter...
- Wed Oct 17, 2018 5:31 pm
- Forum: *Shrodinger Equation
- Topic: Nodal Planes
- Replies: 2
- Views: 2833
Nodal Planes
I believe I remember Dr. Lavelle saying that the 'd' atomic orbital has two nodal planes, but the mention of the cone-shaped nodal plane confused me. Is the cone nodal plane in the d-orbital considered one of the two basic nodal planes or is it a separate, third nodal plane in the d-orbitals? Also, ...
- Mon Oct 15, 2018 4:29 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Heisenberg Indeterminacy Equation
- Replies: 4
- Views: 357
Re: Heisenberg Indeterminacy Equation
We have to account for the difference in position and momentum because electrons have such small mass that the presence of electromagnetic radiation, or light, causes the electron to alter its path and momentum. We use the symbol delta p and delta x because delta represents change which shows that t...
- Mon Oct 15, 2018 1:46 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Planck's constant
- Replies: 7
- Views: 1396
Re: Planck's constant
Planck's constant, which has a rounded value of 6.626 x 10^-34 Joules (or kg.m^2.s^2), is often used in quantum mechanics when determining the energy of a photon. We are currently using Planck's constant as it relates to the equation, E=hv, in which the energy of a photon (E) is equal to Planck's co...
- Mon Oct 15, 2018 1:37 pm
- Forum: Photoelectric Effect
- Topic: Threshold energy [ENDORSED]
- Replies: 17
- Views: 2010
Re: Threshold energy [ENDORSED]
The threshold energy is the minimum amount of energy needed to eject an electron from a specific metal. The threshold energy is not used to calculate the energy of a photon, E=hv, but it is used in calculating the kinetic energy of the ejected electrons. The kinetic energy can be calculated by subtr...
- Sun Oct 07, 2018 7:14 pm
- Forum: Properties of Electrons
- Topic: Electron Affinity
- Replies: 4
- Views: 729
Re: Electron Affinity
Electron affinity is the energy that is released when an electron is added to a gas-phase atom. Generally, the trend for electron affinity is that it increases left to right across a period until it reaches the noble gases and decreases going down a group. Of course there are exceptions to this tren...
- Sun Oct 07, 2018 6:55 pm
- Forum: Properties of Light
- Topic: Topic 1A #3
- Replies: 2
- Views: 156
Re: Topic 1A #3
I am also unsure of which book edition you are referring to, but if your question is on the 7th Edition Topic 1A.3 exercise, then you would need to use the E=hv equation and the c=v*wavelength equation. For part (a), you would only need to use c+v*wavelength, yet remember that all electromagnetic ra...
- Sun Oct 07, 2018 10:28 am
- Forum: Properties of Light
- Topic: Classical vs Quantum
- Replies: 2
- Views: 329
Re: Classical vs Quantum
Classical mechanics describes how large objects act and their corresponding behavior. Classical mechanics typically represents a continuous function because the object is so large that it can be present in a continuous field. Quantum mechanics, meanwhile, describes the behavior of small objects whic...
- Wed Oct 03, 2018 1:17 pm
- Forum: Significant Figures
- Topic: Significant figures for molar mass
- Replies: 7
- Views: 5231
Re: Significant figures for molar mass
When calculating the moles of an element using the molar mass, I believe its best to be as accurate as possible and use the value given to you in the periodic table with that number of significant figures unless otherwise stated. When you reach the final answer through division, though, your end res...
- Wed Oct 03, 2018 11:07 am
- Forum: Balancing Chemical Reactions
- Topic: Combustion
- Replies: 6
- Views: 588
Re: Combustion
If a problem is telling you that there is a combustion of a certain molecule, then it is essentially saying that the designated organic molecule combines with oxygen(O2) to form carbon dioxide(CO2) and water(H2O). Since the combustion of molecules occurs in air, there is an excess of O2 molecules, s...
- Mon Oct 01, 2018 4:11 pm
- Forum: Balancing Chemical Reactions
- Topic: States of Matter
- Replies: 11
- Views: 2045
Re: States of Matter
As previously mentioned, aqueous solutions are solutions such that the solvent is water. In solutions, there is a solvent and a solute, and the solvent is the dominant substance. Therefore, in aqueous solutions, the main component of the mixture is water and the compound is dissolved in water. Aqueo...