Search found 35 matches

by Katelyn 2E
Tue Mar 13, 2018 11:47 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Midterm Question 6B
Replies: 1
Views: 163

Midterm Question 6B

Can anyone explain/provide their work for this question? For further reference, it is the one where 2/3 of the question was taken out and the one that remained was "under constant volume." How would you figure out moles for this question, too?
by Katelyn 2E
Tue Mar 13, 2018 11:45 pm
Forum: Phase Changes & Related Calculations
Topic: Midterm, Question 4B
Replies: 2
Views: 105

Midterm, Question 4B

Hi, can anyone provide the correct answer for this question? Thank you!
by Katelyn 2E
Tue Mar 13, 2018 11:32 pm
Forum: Balancing Redox Reactions
Topic: Test 2 Question 8
Replies: 2
Views: 99

Test 2 Question 8

Hi!
For the electrochemistry test (which I took Wednesday in Dane's section), how do you tell what the value of n, the number of electrons exchanged is? And also what is the balanced equation for this question?
Thank you!
by Katelyn 2E
Tue Mar 06, 2018 3:44 pm
Forum: Zero Order Reactions
Topic: 15.16
Replies: 1
Views: 202

15.16

This isn't a homework problem, but could someone help me understand this question please? Thank you! In the reaction 4 Fe2+(aq) + O2(g) + 4 H3O+(aq) --> 4 Fe3+(aq) + 6 H2O(l), when the Fe2+ concentration alone was doubled, the rate increased by a factor of 8; when both the Fe2+ and the O2 concentrat...
by Katelyn 2E
Mon Mar 05, 2018 11:28 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Unique rates
Replies: 4
Views: 142

Re: Unique rates

Dr. Lavelle also summarizes information regarding unique rates in this thread below and, in general, it is a very informative thread:
viewtopic.php?f=145&t=28677
by Katelyn 2E
Mon Mar 05, 2018 11:22 pm
Forum: General Rate Laws
Topic: 15.17
Replies: 4
Views: 118

15.17

I'm a little confused as to how [C] is independent of the rate, as stated in the solutions manual.
by Katelyn 2E
Mon Mar 05, 2018 11:11 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Kinetics Test
Replies: 2
Views: 120

Kinetics Test

I know that our test only covers 15.1-15.6 but can someone please clarify which class lectures/material that covers and which homework problems would fit that frame?
by Katelyn 2E
Wed Feb 28, 2018 10:29 am
Forum: General Rate Laws
Topic: 15.9
Replies: 5
Views: 148

Re: 15.9

Matthew Lee 3L wrote:On the syllabus, it says to omit this question from the homework.

I think Dr. Lavelle meant to omit Section 15.9 of the reading, not the actual homework question.
by Katelyn 2E
Wed Feb 28, 2018 10:27 am
Forum: General Rate Laws
Topic: Finding reaction rate [ENDORSED]
Replies: 5
Views: 147

Re: Finding reaction rate [ENDORSED]

keep in mind that the rate of reaction is equal to the change in concentration over the change in time. and as said above, concentration is always found in mols
by Katelyn 2E
Wed Feb 28, 2018 10:17 am
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Textbook Problems 15.3 and 15.5
Replies: 7
Views: 428

Re: Textbook Problems 15.3 and 15.5

also regarding this question, is there a difference in how we should calculate rate of reaction and rate of formation?
by Katelyn 2E
Tue Feb 20, 2018 6:21 pm
Forum: Balancing Redox Reactions
Topic: Homework Question 14.5
Replies: 2
Views: 112

Homework Question 14.5

For part a and part d of 14.5, what is the oxidation state of O3 and P4? Thank you!
by Katelyn 2E
Tue Feb 20, 2018 6:07 pm
Forum: Balancing Redox Reactions
Topic: calculating oxidation states
Replies: 2
Views: 151

Re: calculating oxidation states

These are also some general rules that are really helpful: The oxidation state of an individual atom is 0. The total oxidation state of all atoms in: a neutral species is 0 and in an ion is equal to the ion charge. Group 1 metals have an oxidation state of +1 and Group 2 an oxidation state of +2 The...
by Katelyn 2E
Tue Feb 20, 2018 6:03 pm
Forum: Balancing Redox Reactions
Topic: oxidation
Replies: 4
Views: 131

Re: oxidation

what about for O3 like in 14.5 part a?
by Katelyn 2E
Mon Feb 12, 2018 3:49 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: Degeneracy
Replies: 2
Views: 87

Re: Degeneracy

In lecture, we learned that degeneracy, W, is the number of ways of achieving a given energy state. W would be equal to the (number of microstates) ^ (number of particles in the system). To relate it to entropy, you would use the Boltzmann formula: S = kb(lnW).
by Katelyn 2E
Mon Feb 12, 2018 3:38 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: 9.25
Replies: 2
Views: 110

Re: 9.25

I would recommend drawing out the Lewis structures as well. Sometimes, the electron geometry will align with the number of orientation (in example 9.8 in the book), but it does not in this problem. The best way to be sure is to draw them out.
by Katelyn 2E
Mon Feb 12, 2018 3:21 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Units for enthalpy
Replies: 2
Views: 120

Units for enthalpy

Can someone refresh my memory as to what Dr. Lavelle said in class today regarding units for enthalpy? My impression is that he said kJ and kJ/mol could be accepted interchangeably (when we were doing the Hess's Law question).
by Katelyn 2E
Mon Feb 05, 2018 6:55 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 9.25
Replies: 5
Views: 150

Re: 9.25

to follow up, how do you know that W is 6?
by Katelyn 2E
Mon Feb 05, 2018 10:25 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: DG = 0 [ENDORSED]
Replies: 3
Views: 135

Re: DG = 0 [ENDORSED]

Adding on to what Ryan said, DeltaG at equilibrium means there's no net flow, or no tendency for the reaction to favor either direction.
by Katelyn 2E
Mon Feb 05, 2018 10:23 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Types of Disorders [ENDORSED]
Replies: 5
Views: 167

Re: Types of Disorders [ENDORSED]

Thermal disorder is the disorder arising from the thermal motion of the molecules (heating); an increase in heating supplied/temperature leads to an increase in the disorder of a system because the supply of energy increases the thermal motion of the molecules. Positional disorder refers to the diso...
by Katelyn 2E
Mon Feb 05, 2018 10:16 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Clausius Inequality
Replies: 1
Views: 60

Clausius Inequality

Can someone explain the Clausius Inequality and its relevance to what we have been learning about thermodynamics? I found the book's explanation to be a bit confusing.
by Katelyn 2E
Mon Jan 29, 2018 9:35 am
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Useful Summary of Thermodynamic Definitions
Replies: 23
Views: 13177

Re: Useful Summary of Thermodynamic Definitions

will we be discussing these different types of systems each in detail or should we just know the general conceptual idea behind them such as is provided here? thank you!
by Katelyn 2E
Mon Jan 29, 2018 9:32 am
Forum: Environment, Fossil Fuels, Alternative Fuels
Topic: biodiesel fuel [ENDORSED]
Replies: 2
Views: 223

Re: biodiesel fuel [ENDORSED]

I think the most important difference about biodiesel fuel compared to regular fuel is that it is renewable (it can also be domestically produced and is cleaner); instead of being produced from fossil fuels, it can be manufactured from vegetable oils, animal fats, or recycled restaurant grease.
by Katelyn 2E
Mon Jan 29, 2018 9:27 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Entropy Definition [ENDORSED]
Replies: 2
Views: 117

Entropy Definition [ENDORSED]

In class, Dr. Lavelle avoided using the word "disorder" to describe entropy but the book consistently uses it. How would we define/what was Dr. Lavelle's definition of entropy without using "disorder"?
by Katelyn 2E
Mon Jan 22, 2018 2:54 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Cv vs. Cp [ENDORSED]
Replies: 13
Views: 725

Re: Cv vs. Cp [ENDORSED]

Will we have to know the Cvm and Cpm values for the test?
by Katelyn 2E
Mon Jan 22, 2018 2:44 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Concepts for Chapter 8 [ENDORSED]
Replies: 5
Views: 202

Concepts for Chapter 8 [ENDORSED]

I was wondering if anyone who had Dr. Lavelle last quarter has any suggestions as to how study for conceptual problems for this chapter. Thank you!
by Katelyn 2E
Mon Jan 22, 2018 2:42 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Determining Enthalpy of Vaporization
Replies: 4
Views: 139

Re: Determining Enthalpy of Vaporization

Intermolecular forces are the forces of attraction between molecules. Ranked from weakest to strongest, the IMFs we learned last quarter in Chem 14A are London dispersion forces, dipole-induced dipole, ion-induced dipole, dipole-dipole, hydrogen bonding, and ion-dipole. What you are referring to wit...
by Katelyn 2E
Sun Jan 21, 2018 2:43 am
Forum: Calculating Work of Expansion
Topic: Reversible vs Isothermal
Replies: 3
Views: 138

Re: Reversible vs Isothermal

Just to be clear, Dr. Lavelle said this wouldn't be on this week's test right?
by Katelyn 2E
Sun Jan 21, 2018 2:42 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Exercise 8.7
Replies: 2
Views: 113

Re: Exercise 8.7

My TA said that sig figs aren't as big a deal this quarter because students end up focusing more on worrying about sig figs than they do about getting the actual concepts down/the problems right. But yes, answer is written in scientific notation just for the purpose of sig figs.
by Katelyn 2E
Tue Jan 16, 2018 11:46 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond Enthalpies
Replies: 2
Views: 110

Bond Enthalpies

For bond enthalpies, I was wondering how we know which bonds to exclude from our calculations. Is it just the ones that repeat in the reactants and the products?
by Katelyn 2E
Tue Jan 16, 2018 11:44 am
Forum: Phase Changes & Related Calculations
Topic: Good hw questions to practice?
Replies: 2
Views: 127

Re: Good hw questions to practice?

I found the sections under "Reaction Enthalpies," "Hess's Law," "Standard Enthalpies of Formation," and "Bond Formation" to align with what we have learned in class up to this point.
by Katelyn 2E
Tue Jan 16, 2018 11:39 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: living plant
Replies: 4
Views: 163

Re: living plant

A living plant is an open system. Just think about it in terms of photosynthesis where it takes carbon dioxide from its surroundings to produce oxygen; thus there's a constant exchange/flow of mass and energy between the plant and its surroundings.
by Katelyn 2E
Sun Jan 14, 2018 10:46 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard States
Replies: 3
Views: 172

Re: Standard States

A standard state of a substance is its phase (the most stable one) at 1 atm and 25°C. Liquid is the standard state for mercury and bromine. Gas is the standard state for noble gases, halogens, fluorine, chlorine, hydrogen, nitrogen, and oxygen, while all other elements are solid in their standard st...
by Katelyn 2E
Wed Jan 10, 2018 11:33 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Closed System
Replies: 7
Views: 243

Closed System

In discussion, one of the examples for a closed system my TA used was a coolant in a refrigerator coil. Can someone explain how it functions in a manner that makes it a closed system?
by Katelyn 2E
Wed Jan 10, 2018 11:25 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7337
Views: 786274

Re: Post All Chemistry Jokes Here

Anne 2L wrote:what did the ice cube say to his mom as he was melting

MOM ITS JUST A PHASE
by Katelyn 2E
Wed Jan 10, 2018 11:13 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond Enthalpies
Replies: 6
Views: 207

Bond Enthalpies

Can someone please explain to me why bond enthalpies (method 2) are always positive? Thank you!

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