Search found 51 matches
- Sat Mar 17, 2018 9:57 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Collision Theory
- Replies: 5
- Views: 747
Collision Theory
For the final, how in depth do we need to know collision theory?
- Sat Mar 17, 2018 9:08 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: >> [ENDORSED]
- Replies: 2
- Views: 719
>> [ENDORSED]
What does >> or << mean?
- Sat Mar 17, 2018 7:30 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Stoichiometric coefficients
- Replies: 4
- Views: 913
Stoichiometric coefficients
Are stoichiometric coefficients used for elementary reactions? In the book, it states that they are not. However, in lecture, Lavelle has provided examples where there are coefficients in the elementary reactions of a mechanism.
- Sun Mar 11, 2018 10:42 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Midterm Question 5 (Step 2)
- Replies: 2
- Views: 460
Re: Midterm Question 5 (Step 2)
The question states "as it returns to the original internal energy". It was calculated, in step 1, that the change in internal energy was -158 so to return to the original internal energy, step 2 internal energy would have to be the opposite, +158J.
- Sun Mar 11, 2018 10:35 pm
- Forum: Phase Changes & Related Calculations
- Topic: Exothermic Reaction
- Replies: 3
- Views: 435
Re: Exothermic Reaction
The temperature will not change during a phase change. All of the energy being lost is due to a substance changing from one state to another. The energy is used as work to break or form bonds of the molecule.
- Sun Mar 11, 2018 10:28 pm
- Forum: Van't Hoff Equation
- Topic: Derivation
- Replies: 5
- Views: 864
Re: Derivation
I am pretty sure you do not need to know the derivation of the equation, just the equation itself. So memorize the equation and you will be good to go.
- Tue Mar 06, 2018 10:04 pm
- Forum: Zero Order Reactions
- Topic: Finding 1/2 or negative orders
- Replies: 2
- Views: 414
Re: Finding 1/2 or negative orders
you would use the data on the table just as you would for a positive whole number order.
- Sun Mar 04, 2018 10:52 pm
- Forum: First Order Reactions
- Topic: half-lives
- Replies: 4
- Views: 520
half-lives
What is the importance of half-lives? Like why is it significant to know the time needed for the concentration to be half of the initial, why not just calculate the time needed for the concentration to reach zero?
- Sun Mar 04, 2018 10:34 pm
- Forum: General Rate Laws
- Topic: solving for a
- Replies: 2
- Views: 368
solving for a
When solving for (a) in rate reaction problems, will the answer always be a whole number or 1,2,etc...?
- Sun Mar 04, 2018 9:55 pm
- Forum: General Rate Laws
- Topic: a value
- Replies: 3
- Views: 500
a value
I am still confused how to determine/calculate the a value of a reaction. can someone please explain this to me?
- Sun Feb 25, 2018 10:46 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Cell Potential
- Replies: 4
- Views: 591
Re: Cell Potential
hydrogen's cell potential is zero so that it is possible to calculate the cell potential of the other electrode. Standard potentials only give us the overall cell potential and not just one electrode. Therefore, we arbitrarily set the standard potential of hydrogen to zero at all temperatures.
- Sun Feb 25, 2018 10:42 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell Diagrams
- Replies: 4
- Views: 656
Re: Cell Diagrams
Anodes are always on the left and cathodes are always on the right. To figure out which is which you have to determine which reactant is being oxidized and which is being reduced, so look at the electrons.
- Sun Feb 25, 2018 10:40 pm
- Forum: General Rate Laws
- Topic: rate constants
- Replies: 7
- Views: 904
rate constants
how are rate constants calculated and what do they represent?
- Sun Feb 25, 2018 10:26 pm
- Forum: General Rate Laws
- Topic: Unique Average Rates
- Replies: 1
- Views: 264
Re: Unique Average Rates
I think the unique average rate is just specific to the question/ reaction you are given. So when they ask for the unique average rate of the reaction, they are talking specifically about that certain reaction with those stoichiometric coefficients. When you calculate the average rate, the coefficie...
- Sun Feb 25, 2018 10:06 pm
- Forum: General Rate Laws
- Topic: Negative Sign [ENDORSED]
- Replies: 7
- Views: 985
Re: Negative Sign [ENDORSED]
you are finding the average rate of consumption. So, because the reactants are being consumed the delta A or R is going to be negative. For chemical kinetics, the rate is always going to be positive, hence the negative sign.
- Sun Feb 11, 2018 11:22 pm
- Forum: Phase Changes & Related Calculations
- Topic: Lyndons practice midterm
- Replies: 3
- Views: 434
Lyndons practice midterm
Can someone please explain to me this concept: "True/False: One cannot calculate the entropy of vaporization for water at room temperature because water has a boiling point of 373K."?
- Fri Feb 09, 2018 12:20 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Different Gibbs Free Energy values
- Replies: 1
- Views: 294
Different Gibbs Free Energy values
How come you get two different Gibbs free energy values when you solve them using the equation G = H - TS vs G(products) -G(reactants) ?
- Thu Feb 08, 2018 11:38 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Entropy
- Replies: 7
- Views: 717
Entropy
What is the difference between S°m, S°r, and S°f?
- Sun Feb 04, 2018 6:13 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: 9.65
- Replies: 2
- Views: 331
9.65
In problem 9.65, what determines the stability of an element? Like what variable measures that and how are we supposed to calculate that?
- Sun Feb 04, 2018 6:08 pm
- Forum: Calculating Work of Expansion
- Topic: Calculating work of expansion on the exam
- Replies: 2
- Views: 326
Calculating work of expansion on the exam
If Dr. Lavelle doesn't allow calculators on exams, then how are we supposed to calculate any problem that requires solving an integral?
- Sun Feb 04, 2018 6:03 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: 9.35
- Replies: 4
- Views: 462
Re: 9.35
Think about entropy in a manner of disorder. If things are not vibrating, they are stuck in place and orderly. However, if they are vibrating, there is more movement in general, meaning that there is more disorder and entropy.
- Sun Jan 28, 2018 11:39 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: 9.3
- Replies: 5
- Views: 719
Re: 9.3
when heat is exiting the system, heat is being lost so it is negative. When additional heat is entering a system, heat is being added, hence the positive sign.
- Sun Jan 28, 2018 11:28 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: ideal cooler [ENDORSED]
- Replies: 5
- Views: 625
ideal cooler [ENDORSED]
What does it mean by "ideal" when a system is an ideal cooler?
- Tue Jan 23, 2018 8:50 pm
- Forum: Phase Changes & Related Calculations
- Topic: Adiabatic Walls
- Replies: 1
- Views: 291
Adiabatic Walls
Can someone explain to me or give me an example of how energy could be transferred to or from a system as work in an adiabatic container?
- Sun Jan 21, 2018 11:10 pm
- Forum: Phase Changes & Related Calculations
- Topic: ΔU vs. ΔH
- Replies: 10
- Views: 3640
Re: ΔU vs. ΔH
I also was wondering what the relationship between the two was. Like are they completely different variables or do they work together?
- Sun Jan 21, 2018 9:59 pm
- Forum: Phase Changes & Related Calculations
- Topic: heat vs ΔH vs work
- Replies: 2
- Views: 307
heat vs ΔH vs work
Just for clarification, what is the difference between ΔH, work, and heat? (Conceptually)
- Sun Jan 21, 2018 8:47 pm
- Forum: Phase Changes & Related Calculations
- Topic: Irreversible vs reversible
- Replies: 3
- Views: 430
Irreversible vs reversible
Can someone please explain to me the difference between irreversible and reversible processes? I am still a little confused on the concept part of it.
- Sun Jan 14, 2018 10:23 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: U vs H
- Replies: 2
- Views: 201
U vs H
what is the difference between delta H and delta U? also, what units do you use for each?
- Sun Jan 14, 2018 10:21 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Standard States
- Replies: 4
- Views: 1178
Standard States
How do you know an element's standard state? are you just supposed to memorize them or...?
- Sun Jan 14, 2018 10:19 pm
- Forum: Phase Changes & Related Calculations
- Topic: Temperature during phase change
- Replies: 2
- Views: 269
Temperature during phase change
I understand that the temperature remains constant during phase changes, but then why does the temperature increase of water from when it melts to when it is boiling?
- Thu Dec 07, 2017 1:40 pm
- Forum: Bronsted Acids & Bases
- Topic: Protons/ H+
- Replies: 1
- Views: 186
Protons/ H+
In Bronsted acid and Base equations will the proton always be in the form of H+ or could it be something else as well?
- Thu Dec 07, 2017 1:38 pm
- Forum: Lewis Acids & Bases
- Topic: Self-Test 12.2A
- Replies: 1
- Views: 320
Self-Test 12.2A
Can someone explain how NO2- is a Lewis base in the reaction HNO2 + HPO4(2-) --> & <-- NO2- + H2PO4-? like how does NO2- have two electrons to donate?
- Sun Dec 03, 2017 11:39 pm
- Forum: Bronsted Acids & Bases
- Topic: water [ENDORSED]
- Replies: 2
- Views: 342
water [ENDORSED]
How can water act as a base and an acid?
- Sun Dec 03, 2017 11:30 pm
- Forum: Bronsted Acids & Bases
- Topic: Bronsted vs. Lewis
- Replies: 4
- Views: 597
Bronsted vs. Lewis
What is the difference between Bronsted and Lewis acids?
- Sun Nov 26, 2017 11:57 pm
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: Bond Order
- Replies: 5
- Views: 689
Re: Bond Order
whenever there is a decimal, there is a resonance structure meaning that the bond strength is between either a single bond and a double bond, or a double bond and a triple bond
- Sun Nov 26, 2017 11:55 pm
- Forum: Hybridization
- Topic: Question 4.95
- Replies: 2
- Views: 333
Re: Question 4.95
the 2 is the principle quantum number (n)
- Sun Nov 19, 2017 11:28 pm
- Forum: Hybridization
- Topic: Hybrid orbitals
- Replies: 3
- Views: 383
Hybrid orbitals
How do you draw/fill orbitals? like in what order?
- Sun Nov 19, 2017 11:27 pm
- Forum: Hybridization
- Topic: Sigma Bond
- Replies: 3
- Views: 437
Sigma Bond
why can there only be one sigma bond?
- Mon Nov 13, 2017 12:57 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Memorization
- Replies: 5
- Views: 607
Memorization
With the molecular shape and VSEPR, would it be just easier to memorize the different angles and shapes and names for the test?
- Mon Nov 13, 2017 12:53 am
- Forum: Ionic & Covalent Bonds
- Topic: different types of bonds
- Replies: 6
- Views: 885
different types of bonds
how do you know if a bond is ionic, polar, or nonpolar?
- Sun Nov 05, 2017 11:26 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Formal Charge and stability [ENDORSED]
- Replies: 7
- Views: 8298
Formal Charge and stability [ENDORSED]
What is the relation between formal charge and stability of the structure?
- Sun Nov 05, 2017 11:25 pm
- Forum: Octet Exceptions
- Topic: Incomplete Octet
- Replies: 2
- Views: 387
Incomplete Octet
I am still unsure about the concept behind the incomplete octet of boron trifluoride. I know what it says in the book, can anyone explain this in further detail?
- Sun Oct 29, 2017 11:59 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Electron affinity
- Replies: 4
- Views: 424
Re: Electron affinity
Electron affinity is equal to the negative change in energy.
- Sun Oct 29, 2017 11:44 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Spin of electron [ENDORSED]
- Replies: 2
- Views: 318
Spin of electron [ENDORSED]
When writing the arrows denoting the spin of the electron, does it matter if you draw the arrow facing upwards or downwards first?
- Sun Oct 29, 2017 11:42 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Super Octet [ENDORSED]
- Replies: 2
- Views: 2496
Super Octet [ENDORSED]
I am confused on the concept of a super octet. I thought there could only be up to 8 electrons in the outer shell. So, how is a super octet formed?
- Mon Oct 16, 2017 10:27 pm
- Forum: Properties of Light
- Topic: Lyman and Balmer series.
- Replies: 4
- Views: 472
Lyman and Balmer series.
Will we need to know about the Lyman or Balmer series for the test?
- Sun Oct 15, 2017 9:56 pm
- Forum: Properties of Light
- Topic: Speed of Light Constant
- Replies: 18
- Views: 1778
Re: I don't know how to post my own topic
you have to go to board index --> chem 14a --> select which topic your question pertains to and then click post a new topicKayla Ikemiya 1H wrote:Can someone please explain how to start a new topic on this please? I also don't understand 30 C on the post module for Photoelectric effect
- Sun Oct 15, 2017 9:55 pm
- Forum: Properties of Light
- Topic: Speed of Light Constant
- Replies: 18
- Views: 1778
Re: Speed of Light Constant
Since 3.00 x 10^8 m/s is the constant that Dr. Lavelle uses in lecture, I think it is safe to use that on our homework and on tests since the TAs grade them and they know what Lavelle has taught us (i.e 3.00 x 10^8 m/s).
- Sun Oct 15, 2017 9:50 pm
- Forum: *Black Body Radiation
- Topic: Black body for quiz 2 [ENDORSED]
- Replies: 11
- Views: 1764
Re: Black body for quiz 2 [ENDORSED]
He did not go over it during lecture very much, so I am sure it is not needed for the test.
- Sun Oct 15, 2017 5:54 pm
- Forum: Properties of Light
- Topic: Intensity
- Replies: 3
- Views: 348
Intensity
What is meant by the intensity of a wave or the intensity of the light?
- Sun Oct 15, 2017 5:50 pm
- Forum: Photoelectric Effect
- Topic: Wavelike properties [ENDORSED]
- Replies: 4
- Views: 508
Wavelike properties [ENDORSED]
How can we tell if something has wavelike properties?