Search found 61 matches
- Fri Mar 15, 2019 11:29 am
- Forum: Biological Examples
- Topic: biological examples for final
- Replies: 10
- Views: 1647
Re: biological examples for final
I would probably also know any industrial and and environmental examples that Dr. Lavelle has gone over in class just in case. I think it's safe to assume there might be a small question on them.
- Fri Mar 15, 2019 11:19 am
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Catalysts
- Replies: 3
- Views: 266
Re: Catalysts
Additionally, catalysts speed up the rate of reaction by lowering the activation energy, which changes the reaction mechanism. Although this occurs, adding a catalyst doesn't affect reaction enthalpy or the equilibrium position and neither does it alter reaction yields at equilibrium.
- Fri Mar 15, 2019 9:02 am
- Forum: Environment, Ozone, CFCs
- Topic: Homogeneous Catalysts and Ozone
- Replies: 6
- Views: 1607
Homogeneous Catalysts and Ozone
How do homogeneous catalysts play a role in the formation of ozone in the lower atmosphere?
- Sat Mar 09, 2019 3:06 pm
- Forum: Second Order Reactions
- Topic: Straight-Line Plot for Second-Order Reactions
- Replies: 1
- Views: 278
Straight-Line Plot for Second-Order Reactions
Why is the straight-line plot for second-order reactions have a positive slope rather than a negative one like zero-order and first-order reactions?
- Sat Mar 09, 2019 2:50 pm
- Forum: First Order Reactions
- Topic: Half-Life 1st Order Reaction
- Replies: 6
- Views: 643
Re: Half-Life 1st Order Reaction
Why is it that the half-life of a first order reaction doesn't depend on initial concentration?
- Sat Mar 09, 2019 2:41 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: integrated rate law
- Replies: 2
- Views: 331
Re: integrated rate law
To add on, we only consider reactants with the integrated rate law because if we consider products, we also have to keep into account the reverse reaction, which complicates the math. We only consider reactants to "keep the math simple".
- Sat Mar 02, 2019 1:07 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Nernst
- Replies: 4
- Views: 2227
Re: Nernst
The 0.0592 comes from changing the natural log in the original equation ( E=E(standard)-(RT/nF)lnQ ) to log base 10, which yields E=E(standard)-(2.303RT/nF)logQ. At standard temperature (298K), 2.303RT/F = 0.0592, which gives you the representation of the Nernst equation that first mentioned, E = E ...
- Sat Mar 02, 2019 1:01 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: Order of a Reaction
- Replies: 2
- Views: 294
Order of a Reaction
Why is determining the order of a reaction important?
- Sat Mar 02, 2019 1:00 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: Finding n
- Replies: 4
- Views: 681
Re: Finding n
Michelle Lee 2E wrote:What if the n value we calculate using the method of initial rates was not a whole number but some weird decimal?
Dr. Lavelle also said in lecture that he wouldn't give us any fractional orders or anything that you couldn't round to a whole number.
- Fri Feb 22, 2019 10:30 am
- Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
- Topic: Recharging Batteries [ENDORSED]
- Replies: 10
- Views: 1326
Recharging Batteries [ENDORSED]
Why is recharging a battery considered to be an unfavorable reaction?
- Fri Feb 22, 2019 10:25 am
- Forum: Van't Hoff Equation
- Topic: Overview
- Replies: 8
- Views: 1067
Re: Overview
Basically the Van’t Hoff equation is used to calculate the equilibrium constant when the temperature is different as long as you know dH. It shows the temperature dependence of K, the equilibrium constant.
- Fri Feb 22, 2019 10:22 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gibbs free energy at phase changes
- Replies: 2
- Views: 332
Re: Gibbs free energy at phase changes
I believe that Gibbs free energy is 0 at phase changes because there’s an equilibrium that exists during that phase change and dG =0 at equilibrium.
- Fri Feb 15, 2019 11:50 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gibbs Free Energy and Equilibrium
- Replies: 5
- Views: 507
Gibbs Free Energy and Equilibrium
Why is Gibbs free energy 0 at equilibrium?
- Fri Feb 15, 2019 11:37 am
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Isobaric
- Replies: 12
- Views: 1593
Re: Isobaric
Also in relation to the change in internal energy, heat under constant pressure is dH, which could help with the manipulation of dU=q+w.
- Fri Feb 15, 2019 11:30 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gibbs free energy
- Replies: 5
- Views: 478
Re: Gibbs free energy
It also tells us the free energy of a system at any point in time. The fact that it a state function makes it easier to calculate as you would with dH° and dS°.
- Fri Feb 08, 2019 1:03 am
- Forum: Calculating Work of Expansion
- Topic: 4F.1 7th Edition
- Replies: 4
- Views: 480
Re: 4F.1 7th Edition
I'm not entirely sure, but it may be negative because the question is asking how body heat affects the entropy in your surroundings?
- Fri Feb 08, 2019 12:58 am
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Closed Systems and q
- Replies: 1
- Views: 238
Closed Systems and q
I understand that in a closed system, energy can be exchanged with its surroundings but matter cannot. If this is the case, why is it that in a closed system, q=0 is always true? Isn't heat a form of energy? Just some clarification for question 4B.9 in the 7th edition of the textbook.
- Fri Feb 08, 2019 12:55 am
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Spontaneity
- Replies: 2
- Views: 286
Re: Spontaneity
To address the spontaneity, think of the example he mentioned about the boulder on the mountain; it will roll down the side by itself (spontaneously), but it won't roll up the mountain itself. Energy through the form of work is needed to push that boulder up the mountain. If something can occur by i...
- Mon Feb 04, 2019 11:44 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: W=2^NA
- Replies: 3
- Views: 407
W=2^NA
I understand Avogadro’s number can be used when calculating degeneracy, but I’m confused as to when we would use it. Can someone clarify that please?
- Fri Feb 01, 2019 11:42 am
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Universe as a Thermodynamic System
- Replies: 2
- Views: 2661
Universe as a Thermodynamic System
Why is the universe considered an isolated system?
- Fri Feb 01, 2019 11:34 am
- Forum: Calculating Work of Expansion
- Topic: Equations for w
- Replies: 5
- Views: 450
Re: Equations for w
The integral equation is used when calculating reversible expansion done by a gas, since in this case it is set up so that the change in pressure occurs in small increments till it reaches the volume it should be at in equilibrium. In reversible expansion, the external and internal pressures are ne...
- Fri Feb 01, 2019 11:21 am
- Forum: Phase Changes & Related Calculations
- Topic: U and its relations to work
- Replies: 8
- Views: 778
Re: U and its relations to work
Additionally in a closed system, internal energy relates to work in this equation:
delta U = q + w
delta U = q + w
- Fri Jan 25, 2019 11:44 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Standard States
- Replies: 1
- Views: 171
Standard States
I know that the standard state for a gas is 1atm. How do you determine standard states of something other than a gas, such as a liquid or solid, or an element?
- Fri Jan 25, 2019 11:36 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: 3 Methods
- Replies: 3
- Views: 232
3 Methods
In lecture, Dr. Lavelle mentioned that using bind enthalpies is the least accurate method. Why is that so?
- Thu Jan 24, 2019 9:52 pm
- Forum: Phase Changes & Related Calculations
- Topic: Thermochemistry Video Modules
- Replies: 1
- Views: 177
Re: Thermochemistry Video Modules
I don't think there will be any video modules on thermochemistry. I believe that the video modules stop after chemical equilibrium.
- Fri Jan 18, 2019 10:16 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Le Chatelier's Principle
- Replies: 3
- Views: 318
Re: Le Chatelier's Principle
Le Chatelier’s Principle is applied to equilibrium reactions in trying to determine the direction in which a reaction will go when changes are introduced to the system.
- Fri Jan 18, 2019 10:06 am
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: bases and acids
- Replies: 2
- Views: 329
Re: bases and acids
As mentioned above, you would be able to calculate Q in the same manner in which K is calculated. The only difference in its application is that Q represents any point in the reaction that is not at equilibrium.
- Fri Jan 18, 2019 10:04 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: The Quadratic Equation
- Replies: 3
- Views: 165
The Quadratic Equation
Is there a reason why we can “bypass” the quadratic equation when calculating for x with weak acids?
- Fri Jan 11, 2019 11:07 am
- Forum: Ideal Gases
- Topic: Use of the Ideal Gas law vs Combined Gas Law
- Replies: 2
- Views: 291
Re: Use of the Ideal Gas law vs Combined Gas Law
I know that the combined gas law has more restrictions than the ideal gas law, such as the fact that moles (n) has to stay constant. In this sense, this is why the ideal gas law is used more often in regards to equilibrium.
- Fri Jan 11, 2019 11:01 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Kp
- Replies: 9
- Views: 730
Kp
I understand that K is often used to represent either Kc or Kp and that they are found in the same manner. Why do we use Kp for gases when we could also use Kc? Is one more preferred than the other?
- Fri Jan 11, 2019 10:57 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Liquids in Chemical Equilibrium
- Replies: 1
- Views: 172
Re: Liquids in Chemical Equilibrium
It’s to my belief that any liquid or solid in its pure form is negligible in calculating the equilibrium constant because their change in concentration during the equilibrium reaction is so small that it’s not counted.
- Thu Dec 06, 2018 10:01 pm
- Forum: Naming
- Topic: Final Exam
- Replies: 9
- Views: 831
Re: Final Exam
For Gail's review session she recommended that we do know both just in case.
The chemical formula of EN is C2H8N2.
The chemical formula of EDTA is C10H16N2O8.
The chemical formula of EN is C2H8N2.
The chemical formula of EDTA is C10H16N2O8.
- Wed Dec 05, 2018 10:50 am
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Kw
- Replies: 3
- Views: 372
Kw
I’ve seen that Kw=Ka*Kb, but I’ve also seen Kw=10^-14. Can someone clarify that concept for me? Thanks.
- Wed Dec 05, 2018 10:43 am
- Forum: Polyprotic Acids & Bases
- Topic: Significance of Polyprotic Acids & Bases
- Replies: 6
- Views: 930
Significance of Polyprotic Acids & Bases
What is the importance/function of polyprotic acids and bases?
- Fri Nov 30, 2018 10:37 am
- Forum: Properties & Structures of Inorganic & Organic Bases
- Topic: Weak Bases with Nitrogen
- Replies: 4
- Views: 742
Weak Bases with Nitrogen
Dr. Lavelle said something about nitrogen in the compound needing a lone pair or else it can’t act as a base. Can someone remind me why that lone pair is necessary?
- Fri Nov 30, 2018 10:26 am
- Forum: Biological Examples
- Topic: Myoglobin vs Hemoglobin
- Replies: 2
- Views: 169
Re: Myoglobin vs Hemoglobin
To add on, because hemoglobin has 4 myoglobin-like molecules, it therefore has four times the carrying capacity of myoglobin, which is very important for the transport of oxygen in blood.
- Fri Nov 30, 2018 10:19 am
- Forum: Naming
- Topic: Transition metal oxidation states
- Replies: 3
- Views: 336
Re: Transition metal oxidation states
I believe that transition metals can have multiple oxidation states because of their electrons in the 3d orbitals.
- Sun Nov 25, 2018 5:18 pm
- Forum: Octet Exceptions
- Topic: Radicals
- Replies: 16
- Views: 1660
Re: Radicals
Quick question, are we going to have to know in-depth about radicals or just know a basic application of it for the final?
- Sun Nov 25, 2018 5:16 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Formal charge vs octet rule
- Replies: 5
- Views: 759
Re: Formal charge vs octet rule
I would have to agree, having the most stable molecule possible would be the priority over the octet rule (especially since the octet rule becomes violated in and after period3 due to expanded octets) although for the most part having the octet for elements before period 3 does contribute to the ove...
- Sun Nov 25, 2018 5:13 pm
- Forum: Ionic & Covalent Bonds
- Topic: Ionic & covalent character
- Replies: 6
- Views: 1191
Re: Ionic & covalent character
when (if) this happens how can we differentiate between the two characters? I think Dr. Lavelle mentioned a rough guideline based on the difference in electronegativity: if difference is >2, ionic character if difference is <1.5,covalent character It's tougher to determine the character if the elec...
- Fri Nov 16, 2018 12:53 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Lone Pairs in Molecular Shape
- Replies: 4
- Views: 485
Re: Lone Pairs in Molecular Shape
I believe that for the most part what you are saying is correct but I’ll clarify just in case. Lone pair electrons do repel the other electrons on the substituent atoms, which cause the bond angle to be slightly greater than what’s normally expected; in the same case, as a result, the bond angle bet...
- Fri Nov 16, 2018 10:38 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: VSEPR Models with 5 bonding regions
- Replies: 3
- Views: 353
VSEPR Models with 5 bonding regions
It’s pretty easy to see the trends when it comes to VSEPR models with three or even four bonding regions (lone pairs included) but why does having five bonding regions make these trends harder to see? Or rather, why does having 5 domains somehow break the trend?
- Fri Nov 16, 2018 10:29 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Distance from Central Atom
- Replies: 8
- Views: 555
Distance from Central Atom
So I understand that in drawing VSEPR diagrams (or even just a 2D representation with Lewis structures) we use the wedges to represent distance from the central atom. For my question, I was confused on which type of wedge indicated a further distance: the completely shaded or the hatched wedges?
- Fri Nov 09, 2018 10:52 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Tetrahedral molecules
- Replies: 4
- Views: 390
Re: Tetrahedral molecules
Don’t quote me on this, but I believe that if the shape is tetrahedral, the bond angle should be 109.5° for the most part.
- Wed Nov 07, 2018 7:03 pm
- Forum: Bond Lengths & Energies
- Topic: MIDTERM Bond Length Question
- Replies: 15
- Views: 1525
MIDTERM Bond Length Question
There was a question on the midterm about determining the bond length for N-O in NO2, given that the a single bond is 140Å(?) and a double bond is 120Å(?) (I don’t quite remember the units). Any clue on how to determine that?
- Wed Nov 07, 2018 6:57 pm
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Polarizability
- Replies: 2
- Views: 227
Re: Polarizability
I believe that having a higher polarity increases the chances of the distortion of electrons because the electrons from one atom are being pulled/attracted more strongly by another atom. In a sense, I think having a larger atomic radius would also increase the chances of electron distortion.
- Thu Nov 01, 2018 9:37 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Formal Charge of Ions
- Replies: 9
- Views: 935
Re: Formal Charge of Ions
I think the central charge only contributes to the overall net charge of the atom, so as long as the charge of the central atom in addition to the other atoms equal the overall charge, it'll be fine because that's what you're looking for.
- Thu Nov 01, 2018 9:31 pm
- Forum: Resonance Structures
- Topic: Double Bonds and Single Bonds in Resonance Structures
- Replies: 3
- Views: 357
Double Bonds and Single Bonds in Resonance Structures
I remember from high school chemistry that double bonds are shorter than single bonds. If that's the case, could someone explain why the bond lengths in resonance structures are experimentally the same bond length? I didn't quite get that.
- Thu Nov 01, 2018 9:23 pm
- Forum: Octet Exceptions
- Topic: H, He, Li, Be Rule
- Replies: 3
- Views: 808
Re: H, He, Li, Be Rule
I would think that the first four elements on the periodic table don't need an octet because they would rather lose electrons than gain them. It would be very difficult and unstable if they were to somehow try to get an octet.
- Wed Oct 24, 2018 10:49 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Electron configurations
- Replies: 2
- Views: 271
Re: Electron configurations
You can write the shorthand configuration of elements by going back to the nearest noble gas before it (in atomic number), then account for the electrons after that noble gas. Say, for example, you have Arsenic (As). The shorthand would be As: [Ar]4s^2 3d^10 4p^3.
- Wed Oct 24, 2018 10:39 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Writing an Electron Configuration Format
- Replies: 3
- Views: 366
Re: Writing an Electron Configuration Format
Although both are correct, I believe that Dr. Lavelle prefers 1s^2 2s^2 2px^1 2py^1 over the 1s^2 2s^2 2p^2 because it gives better insight on whether or not the electrons are paired.
- Wed Oct 24, 2018 10:35 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Subshells/Orbitals
- Replies: 5
- Views: 510
Re: Subshells/Orbitals
Although I'm not entirely sure which SPECIFIC orbitals the f subshell would have, I do know that it should have 7 orbitals.
(s=1 orbital, p=3 orbitals, d=5 orbitals, f=7 orbitals)
(s=1 orbital, p=3 orbitals, d=5 orbitals, f=7 orbitals)
- Tue Oct 16, 2018 9:46 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Rydberg Equation
- Replies: 4
- Views: 374
Re: Rydberg Equation
This has become a string of questions for now, but to (hopefully) answer most of the questions, one of the UAs told me that Dr. Lavelle prefers that we use the En = -hR/n^2 equation over the other one because it makes more sense conceptually. In this manner, we won't learn the other version but I th...
- Tue Oct 16, 2018 9:41 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Indeterminacy vs. Uncertainty?
- Replies: 4
- Views: 399
Indeterminacy vs. Uncertainty?
I understand that the two are the same, but I don't quite remember why Dr. Lavelle prefers "indeterminacy" over "uncertainty"... Can someone clarify that really quick for me?
- Mon Oct 15, 2018 10:24 am
- Forum: DeBroglie Equation
- Topic: Rest Mass?
- Replies: 4
- Views: 381
Rest Mass?
During lecture Dr. Lavelle said that the De Broglie equation only works if the particles have “rest mass”. Can someone clarify what that means?
- Thu Oct 11, 2018 2:30 pm
- Forum: Properties of Light
- Topic: HW 1A.7
- Replies: 2
- Views: 148
Re: HW 1A.7
I believe the original problem (part (b)) asked for the final wavelength to be in picometers, which is 10^-12. Hope that clears it up!
- Wed Oct 10, 2018 4:44 pm
- Forum: Photoelectric Effect
- Topic: work function
- Replies: 4
- Views: 452
Re: work function
The work function is also called the "threshold energy", so watch for that too! The way I remember how the threshold energy function is by relating it in my mind as something similar to "activation energy" because in both cases, if the minimum requirement is not met, then nothing...
- Wed Oct 10, 2018 4:31 pm
- Forum: Properties of Light
- Topic: Balmer series vs Lyman series
- Replies: 4
- Views: 210
Re: Balmer series vs Lyman series
To add on, don't forget that the Balmer series represents the visible region and that the Lyman series represents the ultraviolet region!
- Wed Oct 03, 2018 10:11 pm
- Forum: SI Units, Unit Conversions
- Topic: Naming Compounds
- Replies: 9
- Views: 811
Re: Naming Compounds
Per Dr. Lavelle, over time you'll pick up how to name compounds through working through more problems just like this. To add further elaborate on the post above: -ite : used when the same compound has lesser amount of oxygen (ex. phosphite, PO3) -ate: used when the same compound has the larger amoun...
- Wed Oct 03, 2018 9:40 pm
- Forum: Empirical & Molecular Formulas
- Topic: Multiplying to get an integer in the empirical formula
- Replies: 4
- Views: 801
Re: Multiplying to get an integer in the empirical formula
For an empirical formula, the numbers must be whole numbers, not numbers like 1.33 or 2.5, etc. In such case that you don't get a whole number, you would multiply that by another number to make it whole. But to address your question regarding the threshold for rounding, I believe Dr. Lavelle mention...
- Wed Oct 03, 2018 9:32 pm
- Forum: SI Units, Unit Conversions
- Topic: Formula Units??
- Replies: 3
- Views: 533
Re: Formula Units??
From my understanding, I think you are correct in regards to finding the formula units. I believe you would have to find the amount of moles first, then multiply by Avogadro's number.