## Search found 70 matches

Fri Mar 15, 2019 3:14 am
Forum: Reaction Mechanisms, Reaction Profiles
Replies: 1
Views: 109

Will we be required to use the steady-state approach or do we only need to know how to use the pre-equilibrium approach?
Fri Mar 15, 2019 3:08 am
Forum: First Order Reactions
Topic: Half life
Replies: 4
Views: 187

### Re: Half life

Using the integrated rate law of the first order reactions: ln [A] = -k t + ln [A]o, you can solve for the half-life (t1/2) by setting [A]= (1/2)[A]o.

Eventually you get, t1/2 = ln(2)/k or 0.693/k.
Fri Mar 15, 2019 2:54 am
Forum: Second Order Reactions
Topic: reaction intermediate
Replies: 4
Views: 382

### Re: reaction intermediate

Intermediates are the things that are produced in one step but used up in a later step. They do not appear in the overall chemical equation. These are the ones that are canceled out when you add the steps together and they are not reactants present in beginning.
Fri Mar 08, 2019 5:37 am
Forum: General Rate Laws
Topic: 15.5
Replies: 2
Views: 161

### Re: 15.5

You can find the unique rate expression of the each reactant and product, then set it equal to the unique rate.

For example:
(-1/3)(d[O2]/dt) = -(0.44 mol/Ls)
Fri Mar 08, 2019 5:31 am
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Reaction Rate vs Rate of Consumption/Formation
Replies: 3
Views: 172

### Re: Reaction Rate vs Rate of Consumption/Formation

I think the rate of consumption is the rate that the reactants are being used up. The rate of formation is the rate that the products are being formed.

During that problem, I think you are supposed to interpret the reaction rate as a unique rate to find the rate of consumption/formation.
Fri Mar 08, 2019 5:15 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: Order of the Reaction
Replies: 3
Views: 157

### Order of the Reaction

What does the order of each individual reactant mean? What does the overall order for the reaction mean?
Fri Mar 01, 2019 4:56 am
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Kinetically Stable
Replies: 3
Views: 240

### Kinetically Stable

What is the difference between being kinetically stable and thermodynamically stable?
Fri Mar 01, 2019 4:50 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: delta G naught when K<1
Replies: 3
Views: 750

### Re: delta G naught when K<1

When K<1, there is a higher concentration of reactants than products. This indicates that products are not being favored in equilibrium. This would lead to how delta G would be positive, or nonspontaneous. You can also look at the equation delta G = -RTln(K). Having a K<1 would result in a negative ...
Fri Mar 01, 2019 4:42 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Finding n for the equation ΔG⁰=-nFE⁰
Replies: 8
Views: 323

### Re: Finding n for the equation ΔG⁰=-nFE⁰

You are able to find n by creating the half reactions and balancing them so the number of electrons are equal. The number of electrons being transferred would then be the number of electrons you have found to balance the half reactions.
Fri Feb 22, 2019 1:18 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Standard hydrogen electrode
Replies: 1
Views: 101

### Standard hydrogen electrode

What exactly is a standard hydrogen electrode and what do we need to know about it?
Fri Feb 22, 2019 1:16 am
Forum: Balancing Redox Reactions
Topic: Number of electrons
Replies: 5
Views: 216

### Number of electrons

How do we determine the number of electrons in the oxidation and reduction half-reactions?
Fri Feb 22, 2019 1:11 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Spontaneous
Replies: 2
Views: 159

### Spontaneous

When is a reaction spontaneous in terms of Gibbs Free Energy, enthalpy, and entropy?

What does being spontaneous actually mean?
Thu Feb 14, 2019 11:21 pm
Forum: Calculating Work of Expansion
Topic: Substituting -nrT for -PΔV
Replies: 4
Views: 198

### Re: Substituting -nrT for -PΔV

The temperature would be given in the problem. To find delta n, you balance the chemical equation and take the difference of moles of gas between the products and reactants.
Thu Feb 14, 2019 11:14 pm
Forum: Calculating Work of Expansion
Topic: Change in moles
Replies: 3
Views: 165

### Re: Change in moles

We only consider the moles of gases. You can ignore the other things.
Thu Feb 14, 2019 11:03 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Comparing complex molecules
Replies: 2
Views: 137

### Comparing complex molecules

How do we compare the standard entropies between complex molecules?

What are the general rules used?
Thu Feb 14, 2019 10:59 pm
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: How to calculate W
Replies: 9
Views: 690

### How to calculate W

How are we supposed to calculate W (degeneracy)?
Fri Feb 08, 2019 1:13 am
Forum: Calculating Work of Expansion
Topic: Reversible Expansion
Replies: 3
Views: 153

### Reversible Expansion

Could someone explain the derivation of work of reversible expansion? Also, what is the difference between reversible work and irreversible?
Fri Feb 08, 2019 1:10 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Knowing which one to use
Replies: 3
Views: 229

### Knowing which one to use

How do we tell which heat capacity to use (heat capacity, specific heat capacity, and molar heat capacity)?

Does anyone also know the variables used for them?
In my notes there are C, Cv, Cp, Csp. I am confused which one is which.
Fri Feb 08, 2019 1:06 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Degeneracy
Replies: 1
Views: 88

### Degeneracy

How do we find the degeneracy of something? I am confused on how we are supposed to use the equation.
Fri Feb 01, 2019 1:58 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Closed System
Replies: 6
Views: 258

### Re: Closed System

The sealed beaker is a closed system because it can still exchange energy with surroundings. It cannot exchange matter with its surroundings because it is sealed with a fixed volume. However, energy can transfer because it is not insulated, meaning heat can be exchanged. It's like when a sealed cup ...
Fri Feb 01, 2019 1:54 am
Forum: Calculating Work of Expansion
Topic: Atmospheres to Joules
Replies: 2
Views: 105

### Re: Atmospheres to Joules

Don't forget that you can also check the constants and equations sheet on the class website. Everything on it will be provided during exams.
Fri Feb 01, 2019 1:49 am
Forum: Phase Changes & Related Calculations
Topic: Steam
Replies: 11
Views: 427

### Re: Steam

Steam causes severe burns because it releases a lot of energy very quickly when it turns back into liquid water.
Fri Feb 01, 2019 1:45 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Most stable form enthalpy
Replies: 3
Views: 210

### Re: Most stable form enthalpy

The standard enthalpy of formation is the standard reaction enthalpy for one mole of a substance from its elements that are in their most stable form. For example. O2 --> O2 The standard enthalpy of formation for O2 is zero because it is already its most stable form so there is no change in enthalpy.
Fri Feb 01, 2019 1:34 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond Enthalpy Method Accuracy
Replies: 1
Views: 89

### Bond Enthalpy Method Accuracy

Could someone explain why using enthalpies is the least accurate method? Does this mean that we should try to always use the other two methods instead?
Wed Jan 23, 2019 7:10 pm
Forum: Ideal Gases
Topic: units for partial pressure of gases
Replies: 6
Views: 378

### Re: units for partial pressure of gases

I don’t think you have to convert to bars. I think it’s recommend to stick with the units that are given in the questions.
Wed Jan 23, 2019 7:07 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: How to know when to use partial pressure or molar concentrations?
Replies: 4
Views: 222

### Re: How to know when to use partial pressure or molar concentrations?

You usually know when they ask for Kp (partial pressure) or Kc (molarity). You can also convert between the two by using the ideal gas law PV = nRT.
Wed Jan 23, 2019 7:04 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sig Figs when dealing with the change in concentration value
Replies: 2
Views: 86

### Re: Sig Figs when dealing with the change in concentration value

You should not round until the end of calculations. Try to keep the as many digits as possible when doing calculations or save them in your calculator. But you do have to keep track of the significant figures during calculations.
Fri Jan 18, 2019 3:05 am
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: when is x negligible
Replies: 7
Views: 1775

### Re: when is x negligible

You can also tell if x is negligible by seeing if the value of x is less than 5% of the initial molarity of the reactant after using the approximation.
Fri Jan 18, 2019 2:39 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Initial Concentrations of ICE Box and 12.79 (6th Edition)
Replies: 3
Views: 1072

### Initial Concentrations of ICE Box and 12.79 (6th Edition)

Are there ever any instances where the initial concentrations of the products are not 0?

In the answer key of 12.79 (6th Edition), why is it that the initial molarity of H30+ is not 0?
Fri Jan 18, 2019 2:35 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Inert Gas
Replies: 3
Views: 120

### Inert Gas

Why does adding inert gas to a container have no effect in reactant, product concentration, and the reaction?

Does this apply to only inert gases? What happens if you add other gases?
Fri Jan 11, 2019 1:54 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Definition of equilibrium
Replies: 4
Views: 102

### Re: Definition of equilibrium

When a reaction reaches equilibrium, the forward and reverse reactions continue to proceed while the concentrations of reactants and products do not change.
Fri Jan 11, 2019 1:43 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Using Q
Replies: 1
Views: 51

### Using Q

How are we supposed to use Q to determine whether a system is at equilibrium?
Fri Jan 11, 2019 1:34 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kc of the Forward/Reverse Reaction
Replies: 6
Views: 2189

### Kc of the Forward/Reverse Reaction

Why is it that when we know the Kc of the forward reaction, we also know the Kc of the reverse reaction? What is the relationship?
Fri Dec 07, 2018 4:22 am
Forum: Lewis Acids & Bases
Topic: 6th Edition 12.49
Replies: 2
Views: 341

### 6th Edition 12.49

Question:
Which is the stronger base, the hypobromite ion, BrO-, or morphine, C17H19O3N? Justify your answer.

What is the explanation that BrO- is the stronger base?
Fri Dec 07, 2018 2:59 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: SO THERE ARE SPECIAL RULES FOR SIG FIGS IN pH THEN
Replies: 5
Views: 346

### Re: SO THERE ARE SPECIAL RULES FOR SIG FIGS IN pH THEN

He did not mention it in class, but I think it is mentioned on the significant figures pdf on his class website.
Tue Dec 04, 2018 11:37 pm
Forum: Bronsted Acids & Bases
Topic: Memorizing Acid and Bases
Replies: 2
Views: 152

### Memorizing Acid and Bases

Will we have to memorize any acid and bases? I heard that have to know the strong acid and bases.

If so which are the ones we need to know?
Fri Nov 30, 2018 9:17 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Dipole moment
Replies: 7
Views: 375

### Re: Dipole moment

Dipole moment is dependent on the electronegativity difference between two atoms. The greater the difference the greater the dipole.
Fri Nov 30, 2018 9:13 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Transition Metals
Replies: 4
Views: 147

### Transition Metals

What was the reason that transition metals are good for electron transfer?
Fri Nov 30, 2018 9:10 am
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Size Vs. Charge of Cations
Replies: 2
Views: 129

### Re: Size Vs. Charge of Cations

When it comes to polarizing power, I think charge is more important.
Fri Nov 23, 2018 9:14 pm
Forum: Dipole Moments
Topic: 6th Edition 4.29
Replies: 2
Views: 194

### Re: 6th Edition 4.29

If the dipole moments cancel each other then the molecule will be nonpolar.
Fri Nov 23, 2018 9:12 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: AX2E2
Replies: 2
Views: 86

### AX2E2

Why is AX2E2 bent and not linear?
Fri Nov 23, 2018 9:04 pm
Forum: Hybridization
Topic: Number of Hybrid Orbitals
Replies: 3
Views: 139

### Number of Hybrid Orbitals

Why does the number of hybrid orbitals equal the number of regions of electron density?
Thu Nov 15, 2018 2:13 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Homework Question 4.1 (6th edition)
Replies: 4
Views: 343

### Re: Homework Question 4.1 (6th edition)

But for b), couldn't there be lone pairs that repel each other. For example, one lone pair at the top of the central atom and one at the bottom. However, they would not have an effect on the bond angle since the repulsion forces from the lone pairs cancel each other out.
Thu Nov 15, 2018 2:02 am
Forum: Student Social/Study Group
Topic: last problem on midterm
Replies: 4
Views: 574

### Re: last problem on midterm

I assume that you are referring to Q8A. If you have two double bonds, it would cause the formal charge on the N to be -1. When you have a negative formal charge, you want to put it on the element with the highest electronegativity, which in this case would be O. You make only one double bond so that...
Thu Nov 15, 2018 1:58 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Will we have to calculate bond angles?
Replies: 8
Views: 288

### Re: Will we have to calculate bond angles?

I think we would need to memorize the bond angles of molecules without lone pairs on the central atom. Professor Lavelle said that we do not need to memorize the bond angles for the molecular shapes with lone pairs on the central atoms. But just that the lone pairs have an effect on the bond angles....
Fri Nov 09, 2018 12:50 am
Forum: Resonance Structures
Topic: homework question 3.71 (6th edition)
Replies: 3
Views: 160

### Re: homework question 3.71 (6th edition)

You want to choose the most stable Lewis structure. This would relate to the formal charges and how you want as many 0's as possible.
Fri Nov 09, 2018 12:46 am
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Liquid and Solid Formation
Replies: 2
Views: 146

### Liquid and Solid Formation

How does the strength of dispersion forces explain whether a molecule is liquid or solid?

Also, during the lecture on 11/7/18, why does CH4 boil at a lower temperature than CCl4?
Thu Nov 08, 2018 11:43 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Distortion and Polarization
Replies: 3
Views: 368

### Re: Distortion and Polarization

You can think of distortion as the tendency of the electron density of ionic bonds to occupy the region between two nuclei. As the distortion of the electron cloud on an anion increases, ionic bonds get more covalent character. Atoms and ions with electron clouds that undergo large distortion are hi...
Thu Nov 01, 2018 6:49 pm
Forum: Bond Lengths & Energies
Topic: Lengths of Bonds
Replies: 9
Views: 263

### Lengths of Bonds

Why are double bonds shorter than single bonds?
Thu Nov 01, 2018 6:40 pm
Forum: Resonance Structures
Topic: Resonance
Replies: 8
Views: 409

### Re: Resonance

Yukta Italia 3I wrote:When we have to draw Lewis Structures on the midterm do you think we'll have to draw every resonance structure possible?

I think you only need to draw the resonance structures for the most stable structure.
Thu Nov 01, 2018 6:37 pm
Forum: Octet Exceptions
Topic: Octet Exceptions
Replies: 3
Views: 239

### Re: Octet Exceptions

I think the 13th column is an exception to the octet rule because the elements in the 13th column have 3 valence electrons. This means that they only need 3 bonds to create a formal charge of 0.

FC = V - (L + S/2)
FC = 3 - 3 = 0
Thu Oct 25, 2018 6:10 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Difference in energy between s-, p-, d-, f- orbitals in the same shell
Replies: 2
Views: 173

### Difference in energy between s-, p-, d-, f- orbitals in the same shell

Why does the energy order in the same shell: s < p < d < f? Does this have to do with how the s-orbital does not have any nodal planes so there is more electron shielding compared to the other orbitals? Is it the less nodal planes you have, the more electron shielding there is, resulting in lower en...
Thu Oct 25, 2018 5:57 pm
Forum: Administrative Questions and Class Announcements
Topic: Constants and Equations
Replies: 2
Views: 135

### Constants and Equations

Will every exam have all the things given from the constant and equations document on the class website?
Thu Oct 25, 2018 1:59 am
Forum: *Shrodinger Equation
Topic: What do we need to know about the Shrodinger Equation? [ENDORSED]
Replies: 1
Views: 391

### What do we need to know about the Shrodinger Equation?[ENDORSED]

During lecture, the equation was given as H(psi) = E(psi).

Do we need to know how to use the equation?
If not, then could someone also explain what the Schrodinger equation is and what we are supposed to know?
Thu Oct 25, 2018 1:53 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Value of Delta X
Replies: 9
Views: 549

### Re: Value of Delta X

I think we would have to multiply the radius by 2 to get the diameter. We want delta x to be the full range of where the electron could be.
Fri Oct 19, 2018 12:24 am
Forum: DeBroglie Equation
Topic: Rest Mass
Replies: 7
Views: 379

### Rest Mass

Does basically anything have rest mass? During the lecture, Dr. Lavelle said that photons have no rest mass. Does that mean we can use DeBroglie's equation on anything except photons?
Fri Oct 19, 2018 12:05 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Meaning of Delta and Uncertainty
Replies: 2
Views: 344

### Meaning of Delta and Uncertainty

What do the deltas in the Heisenberg Indeterminacy equation mean?

Before I thought it meant "change in", but after going to a UA session, delta meant uncertainty.

If delta means uncertainty, what does uncertainty mean?
Thu Oct 18, 2018 11:53 pm
Forum: Properties of Light
Topic: Test 2 [ENDORSED]
Replies: 15
Views: 577

### Re: Test 2[ENDORSED]

On the class website, it says, "Test 2 covers all quantum material up to and including quantum numbers."

Does this mean that there will not be anything about orbitals or anything in chapter 2 (6th edition)?
Thu Oct 18, 2018 7:19 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Nodal Planes [ENDORSED]
Replies: 4
Views: 342

### Nodal Planes[ENDORSED]

I am still confused about what nodal planes are. During the lecture, nodal planes were defined to have zero probability of electron density. Does this mean that nodal planes are a region where there would be no electrons found?
Thu Oct 11, 2018 5:31 pm
Forum: Properties of Light
Topic: Homework Question 3; 6th Edition
Replies: 2
Views: 78

### Re: Homework Question 3; 6th Edition

I think the extent of the change in the electrical field is related to the slope of the wave. As the frequency decreases, the slope of the wave also decreases.
Thu Oct 11, 2018 2:56 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Rydberg's Equation (hydrogen)
Replies: 2
Views: 99

### Rydberg's Equation (hydrogen)

What exactly is Rydberg's equation?

In the book, the equation is given as:
v = R((1/n1^2) - (1/n2^2))

Is this the same equation as En = - hR/n^2 or is it something different? Also, how are we supposed to use this formula when working on problems?
Thu Oct 11, 2018 2:22 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Energy Levels of Hydrogen Spectral Series
Replies: 1
Views: 64

### Energy Levels of Hydrogen Spectral Series

How do you determine the number for the lower energy level for the hydrogen spectral series (Balmer, Lyman) or is this something that could be found from a chart?
Wed Oct 10, 2018 1:53 am
Forum: SI Units, Unit Conversions
Topic: Rounding Off of 5
Replies: 7
Views: 469

### Rounding Off of 5

During one of the peer learning sessions, the UA talked about how you were supposed to round to an even number when there is 5. I do not remember clearly what the UA said. But if you were rounding 4.45 to two significant figures, it would be 4.4, not 4.5. Will we need to do this for future exams (ro...
Thu Oct 04, 2018 2:25 pm
Forum: Balancing Chemical Reactions
Topic: H3, coefficients
Replies: 7
Views: 342

### Re: H3, coefficients

I believe your answer would be fine because we always want to simplify the coefficients if we can. Generally, I think that it is always better to simplify the coefficients.
Wed Oct 03, 2018 9:00 pm
Forum: Limiting Reactant Calculations
Topic: Post-module #33
Replies: 1
Views: 168

### Re: Post-module #33

In order to solve this problem, you have to find out much of the reagents will be able to complete the reaction. It is given that 1 mol B reacts with 1 mol A, but there is only 1 mol A present. Using the given balanced equation: 2A + 1B ---> 3C. You can come up that 3 mol C will be made from every c...
Wed Oct 03, 2018 12:20 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Question E1(6th Edition)
Replies: 7
Views: 325

### Re: Question E1(6th Edition)

I began this problem by multiplying 1.00 mol of Ag by Avogadro's number to get 6.022x10^23 atoms of Ag. Then I multiplied that by 2(144 pm)--144 pm is the radius of the atom, so to get the total length of the atom you have to double it. The end result was 1.73x10^26 pm, which is equal to 1.73x10^11...
Tue Oct 02, 2018 12:19 am
Forum: SI Units, Unit Conversions
Topic: Problem E1 (6th Edition)
Replies: 2
Views: 131

### Problem E1 (6th Edition)

The field of nanotechnology offers some intriguing possibilities, such as the creation of fibers one atom wide. Suppose you were able to string together 1.00 mol Ag atoms, each of radius 144 pm, into one of these fibers by encapsulating them in carbon nanotubes (see Chapter 7). How long would the fi...
Mon Oct 01, 2018 5:29 pm
Forum: Administrative Questions and Class Announcements
Topic: 6th Edition Exercise Answers for Fundamentals Section
Replies: 2
Views: 161

### Re: 6th Edition Exercise Answers for Fundamentals Section

Thank you so much. I was so confused because I thought they would be before chapter 1.
Mon Oct 01, 2018 2:37 pm
Forum: Administrative Questions and Class Announcements
Topic: 6th Edition Exercise Answers for Fundamentals Section
Replies: 2
Views: 161

### 6th Edition Exercise Answers for Fundamentals Section

I have the 6th edition of the textbook and I can not find the answers to the fundamentals section in the back of the book. I do not have the solutions manual yet. Does anyone know where they are located in the 6th edition book or are they just not in there?
Fri Sep 28, 2018 6:23 pm
Forum: Administrative Questions and Class Announcements
Topic: Solutions Manual
Replies: 9
Views: 823

### Solutions Manual

Is the solutions manual required? I have the 6th edition of the textbook, but I do not plan on acquiring the solutions manual. It was noted on the class website link (Questions About The Textbook?): 'All the readings and homework are from the textbook. The solutions manual has the detailed homework ...