Search found 46 matches

by Nora 1F
Sun Mar 11, 2018 10:22 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: K and K'
Replies: 4
Views: 159

Re: K and K'

I believe that they're related through the equilibrium constant, so that K = k/k'. Stated differently, k = (K)(k')
by Nora 1F
Sun Mar 11, 2018 10:04 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Collision Theory
Replies: 3
Views: 182

Collision Theory

How do mean relative speeds and activation energy relate to the collision theory? How is collision theory used to determine a rate constant?
by Nora 1F
Sun Mar 11, 2018 9:56 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Steric requirement
Replies: 1
Views: 152

Steric requirement

Can someone please explain what the steric requirement is and why the steric factor must always be less than one?
by Nora 1F
Sun Mar 04, 2018 11:17 pm
Forum: General Rate Laws
Topic: zero order in rate laws
Replies: 8
Views: 276

Re: zero order in rate laws

If a reactant is zero order, you do not include it in the rate law because it won't affect the rate of the reaction.
by Nora 1F
Sun Mar 04, 2018 11:13 pm
Forum: First Order Reactions
Topic: First order
Replies: 4
Views: 194

Re: First order

Justin is correct! So just to clarify, a reactant is first order if when all other reactant concentrations are held constant and the concentration reactant of interest is doubled, the rate doubles.
by Nora 1F
Sun Mar 04, 2018 10:59 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Test 2
Replies: 4
Views: 202

Test 2

While reviewing my tests I was unsure about why one of the problems was marked incorrect. The question asked to calculate the standard potential for the following reaction using given reduction potentials. Fe^3+ (aq) + 3e- --> Fe (s) Fe^3+ (aq) + e- --> Fe^2+ (aq) E = 0.77 V Fe^2+ (aq) + 2e- --> Fe ...
by Nora 1F
Sun Feb 25, 2018 10:03 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: unique average rates
Replies: 3
Views: 190

Re: unique average rates

I agree about unique rates, but to further clarify, for unique average rates you do not take the coefficient into account so that the unique rate can be different from the average rate. I found the first page of this study guide to be helpful as well. https://books.google.com/books?id=wwlAfF32x18C&a...
by Nora 1F
Sun Feb 25, 2018 9:44 pm
Forum: Second Order Reactions
Topic: About steady state approximation and pre-equilibrium approach
Replies: 1
Views: 98

Re: About steady state approximation and pre-equilibrium approach

From what I understand, you are correct about the pre-equilibrium approach. The pre-equilibrium approach should be used when the first step is fast and the following step is slow, while the steady state approximation should be used if the first step is much slower than the following step.
by Nora 1F
Sun Feb 25, 2018 9:38 pm
Forum: General Rate Laws
Topic: rate law for forward and backward reaction
Replies: 2
Views: 83

Re: rate law for forward and backward reaction

I believe this was referring to when the concentration of product is low, because when the product concentration is low it is less likely that the backward reaction will be occurring at a significant rate.
by Nora 1F
Sun Feb 18, 2018 11:29 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: redox
Replies: 7
Views: 282

Re: redox

In a redox reaction, the oxidizing agent is what causes something else to become oxidized (by becoming reduced itself) and the reducing agent is what causes something else to become reduced (by becoming oxidized itself). If it would help to see it in different words or for some examples, https://che...
by Nora 1F
Sun Feb 18, 2018 11:24 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Concentration Cells
Replies: 5
Views: 215

Re: Concentration Cells

It also might be helpful to keep in mind that with a concentration cell, the lower concentration should be the product concentration.
by Nora 1F
Sun Feb 18, 2018 11:18 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Salt Bridge
Replies: 2
Views: 114

Re: Salt Bridge

I believe salt bridges contain an electrolyte!
by Nora 1F
Sun Feb 11, 2018 11:50 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Entropy of Spontaneous Processes
Replies: 2
Views: 120

Entropy of Spontaneous Processes

Can someone explain why there is always an increase in entropy when a process is spontaneous?
by Nora 1F
Sun Feb 11, 2018 11:39 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Using Nernst Equation
Replies: 2
Views: 147

Using Nernst Equation

Could someone explain what we use Nernst Equation for and how it relates to cell potential and concentration?
by Nora 1F
Sun Feb 11, 2018 11:20 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 9.43 HW
Replies: 3
Views: 275

Re: 9.43 HW

I believe because we are dealing with a change in temperature and because a change of 1 degree Celsius is equivalent to a change of 1 Kelvin, the answer for this question would have the same numerical value to give +0.8 J/*C
by Nora 1F
Mon Feb 05, 2018 12:00 am
Forum: Phase Changes & Related Calculations
Topic: Units [ENDORSED]
Replies: 2
Views: 171

Re: Units [ENDORSED]

I believe that 1 bar would be the unit used in the definition of these conditions, but because the difference between 1 bar and 1 atm is so small and we are accustomed to using atm, you will often see them interchanged.
by Nora 1F
Sun Feb 04, 2018 11:56 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: max work [ENDORSED]
Replies: 1
Views: 110

max work [ENDORSED]

Why is the max work done by a process at constant temperature and pressure equal to deltaG?
by Nora 1F
Sun Feb 04, 2018 11:49 pm
Forum: Calculating Work of Expansion
Topic: Midterm [ENDORSED]
Replies: 3
Views: 168

Re: Midterm [ENDORSED]

I don't think you will need to memorize any equations, but if there is one in particular you are unsure about I would expect the equation sheet to be the same as the one given with the first test and on Dr. Lavelle's site.
by Nora 1F
Sun Jan 28, 2018 10:50 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Universe being isolated
Replies: 3
Views: 151

Re: Universe being isolated

The universe would be described as an isolated system because neither matter nor energy are created or destroyed (gained or lost).
by Nora 1F
Sun Jan 28, 2018 10:42 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 9.1
Replies: 3
Views: 141

Re: 9.1

You should decide which one to use based on the units of the constant.
by Nora 1F
Sun Jan 28, 2018 10:33 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 9.13
Replies: 3
Views: 133

Re: 9.13

Yes, I think that in this case because it says assume ideal behavior and you are not given an amount of moles, you assume you have one mole of N2 gas.
by Nora 1F
Sun Jan 21, 2018 11:11 pm
Forum: Phase Changes & Related Calculations
Topic: ΔU vs. ΔH
Replies: 10
Views: 467

Re: ΔU vs. ΔH

by Nora 1F
Sun Jan 21, 2018 11:10 pm
Forum: Phase Changes & Related Calculations
Topic: ΔU vs. ΔH
Replies: 10
Views: 467

Re: ΔU vs. ΔH

When heat is released or absorbed during a reaction that takes place at constant volume, you use deltaU. When heat is released or absorbed during a reaction that takes place under constant pressure, you use deltaH. I found the following website to be very helpful in explaining the difference if you ...
by Nora 1F
Sun Jan 21, 2018 10:58 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Memorizing Enthalpies [ENDORSED]
Replies: 5
Views: 166

Re: Memorizing Enthalpies [ENDORSED]

From what I understand, all the enthalpies needed for a problem will be given on the test.
by Nora 1F
Mon Jan 15, 2018 12:02 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Calculating Enthaply with Changing Pressure
Replies: 1
Views: 99

Re: Calculating Enthaply with Changing Pressure

I believe when you have constant pressure conditions (isobaric), you use deltaH = q+w , and when you have constant volume conditions, deltaU = q can be used.
by Nora 1F
Sun Jan 14, 2018 11:58 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard State
Replies: 1
Views: 101

Re: Standard State

I believe that unless otherwise stated in the problem, you should assume standard conditions apply.
by Nora 1F
Sun Jan 14, 2018 11:57 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 3 Methods
Replies: 4
Views: 180

3 Methods

Can someone help clarify when each of the three methods discussed in class should be used. I understand that enthalpy being a state function is the basis of the methods but am not sure when to use them.
by Nora 1F
Sun Jan 14, 2018 11:51 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: U=q or U=q+w?
Replies: 3
Views: 153

Re: U=q or U=q+w?

If you're looking for an example of this, problem 8.53 is a good start.
by Nora 1F
Sun Dec 03, 2017 11:52 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Overall Equations vs. Ionic Equations vs. Net Ionic Equations
Replies: 2
Views: 170

Re: Overall Equations vs. Ionic Equations vs. Net Ionic Equations

Rain already answered the question well, but sometimes it just helps to see the process. I found this video helpful and hope it helps you too!

https://www.khanacademy.org/science/che ... -equations
by Nora 1F
Sun Dec 03, 2017 11:26 pm
Forum: Lewis Acids & Bases
Topic: Donating electrons versus protons [ENDORSED]
Replies: 4
Views: 232

Re: Donating electrons versus protons [ENDORSED]

A Lewis acid accept electrons and Lewis bases donate electrons. Bronsted acids donate protons while Bronsted bases accept protons. A Lewis base does not necessarily have to be a Bronsted acid. When only electrons are being transferred (no protons), you are dealing with Lewis definitions.
by Nora 1F
Sun Nov 26, 2017 11:59 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: test 4 question
Replies: 3
Views: 249

Re: test 4 question

I checked Dr. Lavelle's website and it says that Test 4 will include material from chapter 11 from 11.1 to the end of 11.8, and LCP is mentioned before the end of 11.8 so I would understand what it states to be safe. Also on the chemical equilibrium outline, this is the last bullet: "Use Le Cha...
by Nora 1F
Sun Nov 26, 2017 11:45 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: 11.37
Replies: 3
Views: 186

Re: 11.37

For part A, it is helpful to remember that the reverse reaction has a K value that is the inverse of the forward reaction. This is because you find K by dividing the concentrations of the products by the concentrations of the reactants, and if the reverse reaction is occurring, then the numerator an...
by Nora 1F
Sun Nov 19, 2017 11:40 pm
Forum: Naming
Topic: Naming
Replies: 5
Views: 268

Re: Naming

When naming a coordination compound, the ligand names are written first in alphabetical order (before the TM ion). They are written using prefixes to indicate the number of ligands, so the prefix tri- would be chosen over bi- if the complex has three ligands.
by Nora 1F
Sun Nov 19, 2017 11:32 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Number of Ligands
Replies: 2
Views: 175

Number of Ligands

What do you look at to determine the number of ligands in a given complex?
by Nora 1F
Sun Nov 12, 2017 11:57 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR Formula
Replies: 2
Views: 194

Re: VSEPR Formula

I just asked the same question and from what I understand now, this is how AXE notation works: The A is the central atom. The X is an atom that is directly attached to the central atom. The subscript n is the number of atoms (bonded pairs) attached to the central atom. The E is the a lone pair of el...
by Nora 1F
Sun Nov 12, 2017 11:41 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: AXE notation [ENDORSED]
Replies: 3
Views: 343

AXE notation [ENDORSED]

Can somebody explain how AXE notation is used? Will knowing AXE notations be sufficient for naming molecular shapes?
by Nora 1F
Sun Nov 05, 2017 10:55 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 3-D Lewis Structure Drawing
Replies: 2
Views: 118

Re: 3-D Lewis Structure Drawing

For the purpose of this class, I don't believe you will need to draw 3D Lewis structures, but you will need to be able to draw 2D Lewis structures and name the 3D shapes. Hope this helps you narrow down what you have to study!
by Nora 1F
Sun Nov 05, 2017 10:50 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Lewis Structures
Replies: 6
Views: 286

Re: Lewis Structures

Just to clarify, Lewis structures deal with a two-dimensional representation of molecules, so they themselves are not the actual 3D shape. Rather, the VSEPR model is used for this and Lewis structures are useful for counting regions of high electron density when working with the VSEPR model.
by Nora 1F
Sun Oct 29, 2017 9:02 pm
Forum: Formal Charge and Oxidation Numbers
Topic: when to calculate formal charge [ENDORSED]
Replies: 3
Views: 260

when to calculate formal charge [ENDORSED]

During lecture we learned that some Lewis structures are better representations than others, and that formal charge can be used to figure out which structure is best. My question is when we should calculate formal charges. Do we always have to calculate formal charges and compare structures?
by Nora 1F
Sun Oct 29, 2017 7:03 pm
Forum: Resonance Structures
Topic: resonance vs. isomers
Replies: 4
Views: 2189

Re: resonance vs. isomers

Just one more clarification, isomers are atoms/ions of different elements that have the same number of electrons because they have lost or gained electrons. Also keep in mind that a group of isomers, say one where the number of electrons is 10, would also include the atom that normally possesses tha...
by Nora 1F
Sun Oct 22, 2017 11:53 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: d and s orbitals
Replies: 1
Views: 114

d and s orbitals

When writing the electron configuration of an atom that ends similarly to the following 3p^6 4s^2 3d^9, I remember that after rearranging it to 3p^6 3d^9 4s^2 there is sometimes another step that results in the electron configuration being rewritten as 3p^6 3d^10 4s^1, but I am unsure as to why this...
by Nora 1F
Sun Oct 22, 2017 11:42 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Paired & Parallel Configurations
Replies: 2
Views: 151

Re: Paired & Parallel Configurations

In multi-electron atoms, electron-electron repulsion must be factored in when writing electron configurations. In a 2p subshell, for example, there are multiple orbitals, the 2px, 2py, and 2pz orbitals. Each of these orbitals cannot contain more than 2 electrons. However, the way these orbitals are ...
by Nora 1F
Sun Oct 15, 2017 10:26 pm
Forum: Photoelectric Effect
Topic: Difference Between Work Function and the Energy Required to Remove an Electron from one Atom [ENDORSED]
Replies: 4
Views: 348

Re: Difference Between Work Function and the Energy Required to Remove an Electron from one Atom [ENDORSED]

So to clarify, you are correct in thinking that the work function is equivalent to the energy needed to remove an electron from one atom of an element. This is also referred to as threshold energy. To go back to the equation, the total energy of the photon will be equal to the work function plus the...
by Nora 1F
Sun Oct 15, 2017 10:02 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Why don't we use the Rydberg equation from the book?
Replies: 8
Views: 346

Re: Why don't we use the Rydberg equation from the book?

Building on that question, the Rydberg equation is applicable to atoms of different elements, but the other equation -hR/n^2 is only applicable to hydrogen atoms, correct?
by Nora 1F
Thu Oct 05, 2017 4:24 pm
Forum: Limiting Reactant Calculations
Topic: Determining Limiting Reactant
Replies: 6
Views: 534

Re: Determining Limiting Reactant

The limiting reactant will always be the reactant that runs out first, thereby making it so that the reaction cannot take place any longer. Sometimes it will be the reactant with the least amount of moles, but many times it will not be. In order to determine which reactant is the limiting reactant, ...
by Nora 1F
Thu Oct 05, 2017 3:44 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Formula units E.9
Replies: 2
Views: 259

Formula units E.9

I was not sure what the term "formula units" referred to in the following problem. Epsom salts consist of magnesium sulfate heptahydrate. Write its formula. (a) How many atoms of oxygen are in 5.15 g of Epsom salts? (b) How many formula units of the compound are present in 5.15 g? (c) How ...

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