Search found 49 matches
- Fri Mar 16, 2018 11:09 am
- Forum: *Electrophiles
- Topic: what is going to be on the final? [ENDORSED]
- Replies: 12
- Views: 2725
Re: what is going to be on the final? [ENDORSED]
It might be a good idea to also look at the practice final posted on chemistry community!
- Fri Mar 16, 2018 11:08 am
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Rate determining step
- Replies: 2
- Views: 410
Re: Rate determining step
I think it means the slow step.
- Fri Mar 16, 2018 11:06 am
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: sketching reaction profiles
- Replies: 2
- Views: 494
Re: sketching reaction profiles
When sketching a reaction profile, I think it is just important to remember that if the reaction is exothermic, the reactants will start off at a higher point than the products whereas in an endothermic reaction, the reactants will start of lower than the products. In addition, the humps that mark t...
- Fri Mar 16, 2018 11:02 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: When to use standard potentials and when to balance
- Replies: 2
- Views: 386
Re: When to use standard potentials and when to balance
It's just like balancing an equation to complete it. Just remember to balance according to whether it is a basic or acidic solution.
- Fri Mar 16, 2018 11:01 am
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Book Thinking Point
- Replies: 1
- Views: 453
Re: Book Thinking Point
I'm not sure if this is correct, but I wonder if it is because even as the molecules move farther apart and the vibrational motions of the molecules increase, it is the change that stays the same and therefore potential energy does not change?
- Fri Mar 16, 2018 10:59 am
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: 15.67
- Replies: 3
- Views: 511
Re: 15.67
The question is asking for the factor that will increase the rate of reaction therefore using a ratio between the rates of the catalyzed and un-catalyzed will show the multiple between the two.
- Fri Mar 16, 2018 10:57 am
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Question 15.87
- Replies: 1
- Views: 419
Re: Question 15.87
It is simply asking how, under different conditions such as change in concentration, the reaction mechanism might change. For example, in the book it says that in a dilute solution, kinetic data is not able to distinguish between different mechanisms whereas in a highly concentrated solution, the wa...
- Fri Mar 16, 2018 10:53 am
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Steady-State Approximation vs. Pre-equilibrium Condition
- Replies: 4
- Views: 783
Re: Steady-State Approximation vs. Pre-equilibrium Condition
Typically, if the reaction has a fast first step, it is safe to use a pre-equilibrium approximation. On the other hand, if the reaction has a slow first step, a steady state approximation is used instead.
- Fri Mar 16, 2018 10:50 am
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: trend for temp and activation energy
- Replies: 3
- Views: 469
Re: trend for temp and activation energy
Yes, at higher temperatures there is sufficient energy to overcome the larger activation energy.
- Fri Mar 16, 2018 10:49 am
- Forum: General Science Questions
- Topic: Grade
- Replies: 8
- Views: 1523
Re: Grade
One TA I talked to said that there was no curve so it is simply dependent on the number of points you received over the quarter.
- Fri Mar 16, 2018 10:48 am
- Forum: *Aldehydes
- Topic: Toxicity
- Replies: 1
- Views: 1128
Re: Toxicity
I believe the toxicity of an aldehyde is more dependent on the type and quantity rather than assuming as a general rule.
- Thu Mar 01, 2018 10:37 am
- Forum: First Order Reactions
- Topic: reaction order
- Replies: 2
- Views: 483
Re: reaction order
Reaction orders are typically positive numbers but it is possible for them to be zero, fractional, or negative.
- Thu Mar 01, 2018 10:35 am
- Forum: First Order Reactions
- Topic: Pseudo-First Order Reaction [ENDORSED]
- Replies: 4
- Views: 591
Re: Pseudo-First Order Reaction [ENDORSED]
I guess it's kind of related to the second order reaction because of the fact that you have more than one reactant.
- Thu Mar 01, 2018 10:32 am
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Catalytic Reactions
- Replies: 2
- Views: 353
Re: Catalytic Reactions
A catalytic reaction is one in which something is added to the reaction to increase the rate of that reaction. Other good examples of catalytic reactions include enzymes in biochemical reactions.
- Thu Mar 01, 2018 10:26 am
- Forum: Second Order Reactions
- Topic: Half Life
- Replies: 2
- Views: 479
Re: Half Life
Also, if you simply plot the half life reactions for all three types of reactions you can see that in the zero order reaction and the second order reaction, the slope changes as the concentration changes, whereas in the first order reaction graph, the length of the half-life remains at a constant, i...
- Thu Mar 01, 2018 10:20 am
- Forum: Second Order Reactions
- Topic: Example?
- Replies: 4
- Views: 596
Re: Example?
An example of a second order reaction is the formation of oxygen molecules from the combustion of oxygen atoms and ozone (O + O3 → O2 + O2).
- Wed Feb 21, 2018 4:46 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: 14.15 B
- Replies: 1
- Views: 268
Re: 14.15 B
I think it's because H+ and O2 are what form the H2O molecule, which is why we know to include it in one of the half reactions.
- Wed Feb 21, 2018 4:44 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: 14.15b
- Replies: 1
- Views: 267
Re: 14.15b
I think based off the equation and which equation needs to be reduced to receive a positive Ecell, one can determine which reaction is at the anode and which reaction is at the cathode.
- Wed Feb 21, 2018 4:42 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Galvanic Cells
- Replies: 2
- Views: 358
Re: Galvanic Cells
Yes, galvanic cells always have a positive potential difference. Because there are only two ways to combine the two, if one way makes it negative, flip one of them for a positive output.
- Wed Feb 21, 2018 4:39 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: What is n when finding Standard Gibbs Rxn
- Replies: 1
- Views: 237
Re: What is n when finding Standard Gibbs Rxn
n is the number of electrons transferred total between the half reactions.
- Sun Feb 04, 2018 7:31 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Using dS vs change in S
- Replies: 3
- Views: 666
Re: Using dS vs change in S
I think dS is mainly used in proofs as a part of integral calculus and deltaS is what we are actually solving for.
- Sun Feb 04, 2018 7:25 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Question about "Real Processes"
- Replies: 3
- Views: 404
Re: Question about "Real Processes"
All real processes cannot be reversible because it would need to take the same process to return to its original state, however, this not always the case for more complex processes.
- Sun Feb 04, 2018 7:21 pm
- Forum: Calculating Work of Expansion
- Topic: Calculating work of expansion on the exam
- Replies: 2
- Views: 326
Re: Calculating work of expansion on the exam
Otherwise, they would probably be very simple integrals I assume.
- Fri Feb 02, 2018 12:48 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Exergonic [ENDORSED]
- Replies: 5
- Views: 682
Re: Exergonic [ENDORSED]
An example of an exergonic reaction in our body is cellular respiration. In breathing, we are releasing energy into our surroundings. Another example of an exergonic reaction is combustion.
- Fri Feb 02, 2018 12:43 pm
- Forum: Phase Changes & Related Calculations
- Topic: Phase change
- Replies: 4
- Views: 499
Re: Phase change
You know the phase change would occur because it's changing from a solid to a liquid. It is not only increasing in temperature, the heat required to change the physical form of the substance would need to be taken into account as well.
- Fri Feb 02, 2018 12:42 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Using the Kan't Hoff Equation to Calculate the Change in Concentration
- Replies: 1
- Views: 282
Re: Using the Kan't Hoff Equation to Calculate the Change in Concentration
Because deltaS and deltaH are the changes in entropy and enthalpy, it is not an issue of whether or not they would be constant because they are the difference in the initial and final states which would vary between each problem you do.
- Sun Jan 28, 2018 11:06 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: 9.1
- Replies: 3
- Views: 502
Re: 9.1
Usually there if there is a change in temperature involved in an equation, either unit is acceptable because it's only the change that is important.
- Sun Jan 28, 2018 11:05 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Definition of Entropy
- Replies: 10
- Views: 1415
Re: Definition of Entropy
Entropy of a system can be defined as being the thermodynamic quantity that demonstrates how a system's thermal energy cannot be converted into mechanical work. Usually it is interpreted as being the degree of disorder or randomness in a system.
- Sun Jan 28, 2018 10:58 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: 9.19
- Replies: 4
- Views: 631
Re: 9.19
Do you have to cool it to start backwards from 85 degrees C, since we are given the standard entropy of vaporization at 100 degrees C?
- Sun Dec 10, 2017 2:03 am
- Forum: Lewis Structures
- Topic: NO2 Lewis Structure
- Replies: 2
- Views: 2791
Re: NO2 Lewis Structure
In addition, it's a good idea to check the formal charge of the compound.
- Sun Dec 10, 2017 1:49 am
- Forum: Lewis Acids & Bases
- Topic: Determine Lewis Acid
- Replies: 13
- Views: 1671
Re: Determine Lewis Acid
A Lewis acid is an electron acceptor.
- Sun Dec 10, 2017 1:45 am
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Strong or weak acids/ bases
- Replies: 6
- Views: 2069
Re: Strong or weak acids/ bases
A strong acid also typically has weaker electron affinity because it makes it easier to break off completely into its ions.
- Sun Dec 10, 2017 1:43 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Test 4 #6
- Replies: 2
- Views: 415
Re: Test 4 #6
With four values, you would have to calculate the value of Q for the initial molar concentrations and compare it to K to determine which direction the reaction is going in. Then, from there you can solve the rest of the ICE table normally.
- Fri Dec 08, 2017 4:39 pm
- Forum: Bronsted Acids & Bases
- Topic: Bronsted and Lewis Acids
- Replies: 3
- Views: 495
Re: Bronsted and Lewis Acids
Based on the definitions, I don't believe this can be true. Bronsted-Lowry bases are bases because they combine with hydrogen ions, which is possible due to the lone pair of electrons they have, which is consistent with the Lewis acid definition.
- Fri Dec 08, 2017 4:30 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: number of oxygen atoms effect on acidity
- Replies: 1
- Views: 792
Re: number of oxygen atoms effect on acidity
The bond strength of O - H in the acid and the stability of the conjugate base determine the strength of the acid. When there are more electronegative oxygen atoms pulling away electron density from the O - H bond, the bond is weakened and can therefore break more easily. Charge density might also b...
- Thu Dec 07, 2017 11:59 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Question 12.55
- Replies: 1
- Views: 226
Re: Question 12.55
You would need to use an ICE table to calculate the H3O+ concentration which you can use to divide over the initial concentration of CH3COOH x 100 to get the percentage deprotonation.
- Thu Dec 07, 2017 11:57 pm
- Forum: Lewis Acids & Bases
- Topic: 12.17
- Replies: 2
- Views: 448
Re: 12.17
For these types of questions, typically the periodic table and an element's metallic or nonmetallic properties are used to determine whether or not something is acidic, basic, or amphoteric.
- Thu Dec 07, 2017 11:55 pm
- Forum: Lewis Acids & Bases
- Topic: 12.13
- Replies: 5
- Views: 912
Re: 12.13
Ag+ is a Lewis acid because if Ag+ accepts an electron it would become just Ag. In one example of 2NH3 + Ag+ --> [Ag(NH3)2]+, the lone pair of e- on NH3 would go to the Ag+.
- Thu Dec 07, 2017 11:52 pm
- Forum: Bronsted Acids & Bases
- Topic: Lone Pair of Bronsted
- Replies: 1
- Views: 192
Re: Lone Pair of Bronsted
A Bronsted base requires a lone pair of electrons to bond to the H+ in order for it to be capable of accepting a proton.
- Sun Dec 03, 2017 1:25 am
- Forum: Acidity & Basicity Constants and The Conjugate Seesaw
- Topic: Problem 55 Part D
- Replies: 1
- Views: 199
Re: Problem 55 Part D
Certain substances are bound very tightly together and do not split apart easily. Take for example, CH4 or methane, which is less acidic since all four hydrogen atoms are held very closely to the carbon atom and therefore does not break off as easily. On the other hand, substances held together by p...
- Sun Dec 03, 2017 12:29 am
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: pH and pOH
- Replies: 10
- Views: 1414
Re: pH and pOH
The pH scale measures the H+ concentration while the pOH scale measures the OH- concentration. Depending on which value you are given, one way to calculate the pH or the pOH of a solution is pH + pOH = 14.
- Sat Nov 04, 2017 5:41 pm
- Forum: Administrative Questions and Class Announcements
- Topic: 14B and 14BL
- Replies: 3
- Views: 427
Re: 14B and 14BL
I heard several people take 14B and 14BL in separate quarters.
- Sat Oct 28, 2017 4:54 pm
- Forum: *Shrodinger Equation
- Topic: Shrodinger Equation Applications [ENDORSED]
- Replies: 7
- Views: 803
Re: Shrodinger Equation Applications [ENDORSED]
Doesn't the Shrodinger equation only apply to particle in a box and certain laws of conservation of energy?
- Sat Oct 28, 2017 4:39 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Valence Electrons [ENDORSED]
- Replies: 1
- Views: 249
Re: Valence Electrons [ENDORSED]
The valence electrons are just the electrons in the outer shell, so if it is the outermost, then it is included.
- Sat Oct 21, 2017 3:43 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Homework for Test #3
- Replies: 1
- Views: 329
Re: Homework for Test #3
I believe we'll be finishing up the rest of Quantum World for the next test (which I think is our mid-term).
- Sat Oct 21, 2017 3:31 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Orbitals and Electron Configuration
- Replies: 3
- Views: 401
Re: Orbitals and Electron Configuration
I think it can be written either way. Distinguishing between the x and y orbitals of the 2p shell just clarifies where exactly the electrons go.
- Sat Oct 14, 2017 4:27 pm
- Forum: Photoelectric Effect
- Topic: Photoelectric effect [ENDORSED]
- Replies: 6
- Views: 1102
Re: Photoelectric effect [ENDORSED]
1 nm = 10^-9 m
- Sat Oct 14, 2017 2:56 pm
- Forum: Photoelectric Effect
- Topic: general curiosity about atom stability [ENDORSED]
- Replies: 2
- Views: 506
Re: general curiosity about atom stability [ENDORSED]
I'm not sure if this answers your question exactly but an atom is most stable when their outermost energy level is either empty or completely full.
- Wed Oct 11, 2017 4:59 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Bohr Condition/Rydberg Constant
- Replies: 2
- Views: 473
Re: Bohr Condition/Rydberg Constant
I think the Bohr model simply explained the structure of the Rydberg formula and proved the observed results found from the model.