Search found 51 matches
- Tue Mar 13, 2018 9:32 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Chapter 15.12?
- Replies: 4
- Views: 473
Chapter 15.12?
Online it says we will be tested all of chapter 15 excluding 15.9, however 15.12 is quite confusing and contains some equations that I don't recall looking at. What do you think I should know?
- Tue Mar 13, 2018 7:20 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Steady-State v Pre equilibrium?
- Replies: 2
- Views: 430
Steady-State v Pre equilibrium?
What is the difference between "imposing the steady-state approximation" and "assuming that there is a pre-equiibrium" for determining rate laws?
- Sun Mar 11, 2018 10:28 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Pre-equiliibrium?
- Replies: 3
- Views: 588
Pre-equiliibrium?
the textbook says: "A rate law is often derived from a proposed mechanism by imposing the steady-state approximation or assuming that there is a pre-equilibrium." What is meant by "there is a pre-equilibrium?"
- Sun Mar 11, 2018 8:07 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Steady State Approximation?
- Replies: 2
- Views: 451
Steady State Approximation?
What is the steady state approximation and what are it's impacts?
- Sun Mar 11, 2018 7:37 pm
- Forum: First Order Reactions
- Topic: Slope of 1st order RXNs
- Replies: 9
- Views: 1308
Slope of 1st order RXNs
Is the slope of 1st order reactions +k or -k, and what is time graphed against in terms of [A]?
- Sun Mar 11, 2018 7:35 pm
- Forum: Zero Order Reactions
- Topic: Half-Life of Zero Order
- Replies: 3
- Views: 645
Half-Life of Zero Order
Next to the half life equation for zero order reactions i the text book it says that the equation isn't used. Do you know why this is? It also has that written next to the Second order half life equation but we were asked about that on Test #3. Should i assume that this is fair game as well?
- Sun Mar 11, 2018 7:30 pm
- Forum: Zero Order Reactions
- Topic: Pseudo Zero Order Reactions
- Replies: 3
- Views: 1416
Re: Pseudo Zero Order Reactions
I don't believe it is possible to have a zero order reaction. This is when one or more reactants is kept in such high quality that the r relative concentration hardly change during the reaction. If you did this to all the reactants to get something like a pseudo zero order, then they would all chang...
- Sun Mar 11, 2018 7:14 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Molar Entropy
- Replies: 9
- Views: 1280
Re: Molar Entropy
Yes, the larger a molecule is, the larger it's molar entropy. This is because a larger molecule has more possible substates, positions, or orientations. It's degeneracy is higher. For example, a linear molecule can have two possible orientations, whereas a trigonal planar molecule could have more.
- Sun Mar 11, 2018 7:12 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Slowest Step
- Replies: 3
- Views: 514
Re: Slowest Step
Its just like a limiting reactant problem form fundamentals of 14A. The amount of product that can be made relies on the limiting reactant based on the molar ratios. In the same way, the slowest step limits the rate of the reaction.
- Sun Mar 11, 2018 5:56 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: Negative Order
- Replies: 7
- Views: 15688
Re: Negative Order
Conceptually, a reaction with a negative order means that as you increase the concentration of reactant, the reaction rate actually decreases. This seems to eb an interesting phenomena to me, and I 'm sent sure of any real life examples of it.
- Sun Mar 11, 2018 5:54 pm
- Forum: Balancing Redox Reactions
- Topic: redox
- Replies: 6
- Views: 917
Re: redox
Its kind of a backwards terminology. If you follow the flow of electrons, the particles being oxidized are the reducing agents, and the particles being reduced are the oxidizing agents.
- Tue Mar 06, 2018 10:56 pm
- Forum: First Order Reactions
- Topic: pseudo rxn
- Replies: 4
- Views: 718
Re: pseudo rxn
A pseudo 1st order reaction means that the reaction is actually a second order reaction, but we've set one of the reactants at such a high concentration that the change to it during the reaction is negligible. Thus, because for all intents and purposes only one reactant concentration is changing, it...
- Tue Mar 06, 2018 10:51 pm
- Forum: General Rate Laws
- Topic: Proper units
- Replies: 7
- Views: 832
Re: Proper units
It shouldn't matter what units your answer is in.
- Tue Mar 06, 2018 10:50 pm
- Forum: Zero Order Reactions
- Topic: Test 3
- Replies: 1
- Views: 479
Re: Test 3
The negative orders might appear on the test, while fractional will not. Yes, you can get both from the trials. For example, if the rate changes from 20 to 10, when [a] doubles, it means it is -1 in A. This is an answer from Chem mod on that topic in response to a previous question. In other words,...
- Tue Mar 06, 2018 10:48 pm
- Forum: First Order Reactions
- Topic: Negative Order RXN?
- Replies: 2
- Views: 887
Negative Order RXN?
What does it mean if a reaction has a negative order?
- Tue Mar 06, 2018 10:44 pm
- Forum: First Order Reactions
- Topic: k
- Replies: 16
- Views: 1650
Re: k
I don't think the math of the problem is messed up, simply on a logistics level, when a different unit is used. its all about keeping track of your units. Also it will be easier to keep the units the same as the units of the answer you are trying to find
- Tue Mar 06, 2018 10:42 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Increasing Concentration of Reactants
- Replies: 5
- Views: 767
Re: Increasing Concentration of Reactants
yes, the reactions we are dealing with have a favorable forward reaction, and because we are typically dealing with them from the beginning of the reaction, they have not yet hit equilibrium. Therefore, an increase in reactants will increase the rate of the reaction
- Sun Mar 04, 2018 7:31 pm
- Forum: General Rate Laws
- Topic: Naming Clarification
- Replies: 3
- Views: 454
Naming Clarification
Is a Differential rate law the same thing as an Instantaneous rate law?
Thank you
Thank you
- Mon Feb 26, 2018 10:57 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Standard Potential
- Replies: 4
- Views: 632
Re: Standard Potential
As far as I can tell, pH is specific to solutions, such as an aqueous solution of HCl- at standard pressure and temperature wont be the same as any kind of bases and I'm pretty sure it would be a complicated precess to regulate this. So Im pretty are the answer is no
- Mon Feb 26, 2018 10:53 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Isolated [ENDORSED]
- Replies: 3
- Views: 766
Re: Isolated [ENDORSED]
An isolated system is defend as a system in which no heat or matter is transferred into/out of. Because of the law of conservation of matter and energy, the amount of matter and energy in the universe is constant and unchanging - thus an isolated system.
- Mon Feb 26, 2018 10:50 pm
- Forum: Balancing Redox Reactions
- Topic: Half Reaction Order
- Replies: 9
- Views: 2885
Re: Half Reaction Order
An oxidation reaction would have the electrons added (electrons are lost), so they should be on the right side of the arrow. A reduction reaction would have the opposite situation occurring, with electrons being gained so they will be listed on the left side.
- Mon Feb 26, 2018 10:47 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Cell Potential
- Replies: 9
- Views: 3235
Re: Cell Potential
These equations can be used in the same situation, however the one with a number already in it has been simplified with the entry of variables already.
- Mon Feb 26, 2018 10:46 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Q and K
- Replies: 7
- Views: 905
Re: Q and K
Q and K are the same in this context as in equilibrium, so the ideas around K>1 (products are favored), Q>K (reactants are favored), Q<K (products favored) are the same
- Fri Feb 02, 2018 8:39 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Residual Molar Entropy?
- Replies: 3
- Views: 492
Residual Molar Entropy?
Question 9.25 asks about the residual molar entropy of a disordered crystal, and I'm not quite sure what it's asking or how to go about answering the problem.
- Fri Feb 02, 2018 8:28 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Problem 9.19 about Standard Entropy
- Replies: 6
- Views: 819
Problem 9.19 about Standard Entropy
For problem 9.19, It asks us to calculate the standard entropy of vaporization of water at 85 degrees. The solution of the problem shows that you have to calculate \Delta S of heating the reactants, and then \Delta S of vaporization, but then for some reason it says you have to calculate the entropy...
- Mon Jan 29, 2018 7:59 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Kb=?
- Replies: 2
- Views: 340
Kb=?
In my notes I have two different definitions of Kb.
I have Kb=(R)(Avogadro's number)
and Kb=(R)(number of moles n)
Which is correct?
I have Kb=(R)(Avogadro's number)
and Kb=(R)(number of moles n)
Which is correct?
- Mon Jan 29, 2018 7:11 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Degeneracy and Entropy
- Replies: 3
- Views: 558
Degeneracy and Entropy
I am still unsure as to what exactly degeneracy is, and how degeneracy is related to entropy.
- Mon Jan 22, 2018 11:23 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Open System [ENDORSED]
- Replies: 4
- Views: 493
Re: Open System [ENDORSED]
In a more Laboratory-like setting, an open system could be a glass beaker into which you can place different substances. if you can also place it on some sort of heat source like a bunsen burner or cool it down in addition to the exchange of materials it will be an open system
- Mon Jan 22, 2018 11:14 pm
- Forum: Phase Changes & Related Calculations
- Topic: Heat capacities
- Replies: 5
- Views: 608
Re: Heat capacities
Degrees celsius and Kelvin cannot be used interchangeably. One unit of each is indeed equal, but as for the numerical value associated with a temperature, Kelvin is equal to # degrees celsius + 273.15
- Mon Jan 22, 2018 11:08 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Different Delta H. Question 8.57
- Replies: 2
- Views: 364
Different Delta H. Question 8.57
In this question, it states a Delta H with a subscript c. What does the C mean?
- Mon Jan 15, 2018 1:43 pm
- Forum: Calculating Work of Expansion
- Topic: Question 8.11 Reversible v Irreversible actions
- Replies: 2
- Views: 415
Question 8.11 Reversible v Irreversible actions
In Question 8.11, What is the difference between the (a) and the (b) in which it expands reversible and isothermally?
Thanks
Thanks
- Mon Jan 15, 2018 1:38 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Units of Pressure
- Replies: 3
- Views: 475
Units of Pressure
What are all the units of pressure and their conversions? Which unit is not commonly used? Will need to memorize these?
Thanks
Thanks
- Mon Jan 15, 2018 1:34 pm
- Forum: Phase Changes & Related Calculations
- Topic: Types of Systems
- Replies: 10
- Views: 1475
Types of Systems
What is the difference between a closed and isolated system?
Thanks!
Thanks!
- Sun Dec 03, 2017 9:43 pm
- Forum: Naming
- Topic: Naming Coordination Compounds
- Replies: 8
- Views: 814
Re: Naming Coordination Compounds
If your transition metal (or central atom) is contained in the anion part of the compound, -ate will be added
- Sun Dec 03, 2017 9:27 pm
- Forum: Hybridization
- Topic: Pi Bonds
- Replies: 2
- Views: 304
Re: Pi Bonds
It is related to the idea of resonance structures. If a molecule can have a pi bond in multiple places, we know that it does not actually have different kinds of bonds, but rather, all the bonds are an average of all the bonds in the structure. This can be seen in Benzene. So because one pi bond is ...
- Sun Nov 26, 2017 7:20 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: 4.43
- Replies: 2
- Views: 393
4.43
I don't quite understand what s-character means, and why bond angles increases as s-character increases. Could someone try to explain the to me?
- Sun Nov 26, 2017 7:17 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Sigma and Pi bonds
- Replies: 2
- Views: 333
Sigma and Pi bonds
I understand that a double bond will be comprised of a sigma and pi bond, but I don't understand the hybridization and orbitals that prove that. Could do someone explain it?
- Sun Nov 19, 2017 11:35 pm
- Forum: Einstein Equation
- Topic: Use of symbols
- Replies: 6
- Views: 1167
Re: Use of symbols
If it helps, you could write out the whole problem in a way that you are comfortable with, and then change your variable afterwards.
- Sun Nov 19, 2017 2:11 pm
- Forum: Naming
- Topic: Terminology
- Replies: 4
- Views: 421
Terminology
For whatever reason, as we've moved into this most current topic, I have been really lost and confused even with the most basic topics. I know this is probably a really dumb question, but what exactly is a ligand, and what is their relevance. Why is it important to be able to recognize a ligand and ...
- Sun Nov 12, 2017 10:57 pm
- Forum: Lewis Structures
- Topic: Radicals
- Replies: 7
- Views: 783
Re: Radicals
Most often, yes. With an odd number of electrons, there will be one electron ending up without a pair. Thank you of this illuminating knowledge benevolent sir :-* Why welcome fair kind maiden, hath 14a been treating thee kindly? 14a hath been a journey of the soul, down to my innermost electron (te...
- Sun Nov 12, 2017 10:47 pm
- Forum: Lewis Structures
- Topic: Radicals
- Replies: 7
- Views: 783
Re: Radicals
Veronica Rasmusen 1E wrote:Most often, yes. With an odd number of electrons, there will be one electron ending up without a pair.
Thank you of this illuminating knowledge benevolent sir :-*
- Sun Nov 12, 2017 10:39 pm
- Forum: Lewis Structures
- Topic: double bonds in NO3-
- Replies: 2
- Views: 1850
Re: double bonds in NO3-
Nitrogen will stick pretty closely to the octet rule, and if all the bonds were double bonds, the formal charges would indicate the [censored] would not be the most stable molecule.
- Sun Nov 12, 2017 10:16 pm
- Forum: Lewis Structures
- Topic: Radicals
- Replies: 7
- Views: 783
Radicals
Can you assume a molecule will be radical if its atoms have an odd number of valence elctorns between themselves?
- Sun Nov 05, 2017 11:07 pm
- Forum: Lewis Structures
- Topic: Expanded Octet Rule
- Replies: 3
- Views: 498
Re: Expanded Octet Rule
Non-metals with a d-subshell are able to have expanded octets. For instance, elements 13-17 can have expanded octets. You’ll know to draw an expanded octet when the central atom is bonded to more than 4 elements. The elements that are metals (transition metals included) will tend to give away electr...
- Sun Nov 05, 2017 11:01 pm
- Forum: Ionic & Covalent Bonds
- Topic: Ionic vs Covalent Bonds
- Replies: 4
- Views: 565
Re: Ionic vs Covalent Bonds
Covalent bonds are stronger than ionic bonds
- Sun Oct 29, 2017 10:17 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Test #3 Material [ENDORSED]
- Replies: 1
- Views: 350
Test #3 Material [ENDORSED]
Will we be tested anything related to the f-orbitals? I'm not sure if there are any special rules regarding the order in which electrons get put in subshells once the f-orbital is thrown in the mix, and I'm not sure if I should spend time figuring it out.
Thanks!
Thanks!
- Sun Oct 29, 2017 9:18 pm
- Forum: Ionic & Covalent Bonds
- Topic: Study Habits [ENDORSED]
- Replies: 8
- Views: 1199
Re: Study Habits [ENDORSED]
It might not be super helpful,because you asked for online sources, but to study I walk myself through the examples in the book step by step to make sure they make complete sense to me before I try the problems in the book. Sometimes the wording of the problems is confusing , but if i have a good ba...
- Sun Oct 15, 2017 11:00 pm
- Forum: Properties of Light
- Topic: Intensity
- Replies: 3
- Views: 348
Re: Intensity
In typical waves, intensity is measured as an increase in amplitude. Amplitude is the height of the waves, or the distance of the crests and troughs of waves from the midpoint or node. However, because light functions as a wave and proton, the amplitude does nothing to increase the amount of energy ...
- Sun Oct 15, 2017 10:51 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3591957
Re: Post All Chemistry Jokes Here
You must be made of Uranium and Iodine...
because all I can see is U and I
because all I can see is U and I
- Sun Oct 15, 2017 10:43 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3591957
Re: Post All Chemistry Jokes Here
Q: Why was the mole of oxygen molecules excited when he walked out of the singles bar?
A: He got Avogadro's number!
A: He got Avogadro's number!
- Sat Oct 07, 2017 9:18 pm
- Forum: SI Units, Unit Conversions
- Topic: Significant Figures in relation to molar mass [ENDORSED]
- Replies: 4
- Views: 11512
Significant Figures in relation to molar mass [ENDORSED]
Should the amount of significant figures given in a value in the problem affect the number of sig figs that I use of the molar mass or should i go as precise as possible? For Example: If I am given a mass with two significant figures and I need to convert that value to moles, should I only use two s...