Search found 31 matches

by Hailey Johnson
Thu Mar 15, 2018 11:42 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Midterm Question
Replies: 2
Views: 213

Re: Midterm Question

Also, in part a, why do we have to use the temperature in degrees Celsius instead of K? I know the total heat is different when I use temperature in Kelvin, but the percent of heat used to heat the water is the same, so, does it matter which form of temperature I use?
by Hailey Johnson
Thu Mar 15, 2018 11:35 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Identifying a catalyst in a reaction
Replies: 4
Views: 149

Identifying a catalyst in a reaction

How do we differentiate between an intermediate and a catalyst in a reaction mechanism if they both cancel out and are not included in the overall chemical equation?
by Hailey Johnson
Thu Mar 15, 2018 11:33 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Midterm Question
Replies: 2
Views: 213

Midterm Question

On part b of question 3 on the midterm, why do we use specific heat capacity to determine which pot is more energy efficient instead of the molar heat capacity?
by Hailey Johnson
Thu Mar 15, 2018 11:31 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 15.63
Replies: 1
Views: 86

15.63

In problem 15.63 in the textbook the solution includes the value -0.59. Can anyone tell me where this comes from?
by Hailey Johnson
Sun Mar 11, 2018 9:15 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Midterm Question
Replies: 4
Views: 231

Midterm Question

In question 3 on the midterm, when calculating the heat required to change the temperature of the pot and the water, why do we use degrees Celsius and not Kelvin? Does it matter which one I use in future problems?
by Hailey Johnson
Sun Mar 11, 2018 1:04 pm
Forum: Second Order Reactions
Topic: Half life of second order reactions
Replies: 8
Views: 416

Re: Half life of second order reactions

Definitely ignore that in the book. It confused me too, but on the third test the equation for the half-life of a second order reaction was on the formula sheet, so we are expected to know how to use it.
by Hailey Johnson
Sun Mar 11, 2018 1:01 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Reaction Mechanisms [ENDORSED]
Replies: 2
Views: 81

Reaction Mechanisms [ENDORSED]

Why would we choose to use to use the pre-equilibrium method vs. the stable-state method? What is the difference?
by Hailey Johnson
Tue Mar 06, 2018 3:46 pm
Forum: First Order Reactions
Topic: Ordered Reactions
Replies: 1
Views: 69

Ordered Reactions

I understand that the difference between first and second order reactions it that in first order reactions, the rate is proportional to the first power of the concentration, and for second order reactions the rate is proportional to the second power of the concentration, but can anyone give me a mor...
by Hailey Johnson
Sat Mar 03, 2018 9:58 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Q vs. K
Replies: 8
Views: 317

Q vs. K

What is the difference between Q and K and how do we know which one to use in a given problem?
by Hailey Johnson
Sat Mar 03, 2018 9:55 pm
Forum: First Order Reactions
Topic: Reaction Orders [ENDORSED]
Replies: 2
Views: 80

Reaction Orders [ENDORSED]

Can someone help clarify what the different reaction orders mean and how we use them?
by Hailey Johnson
Sat Mar 03, 2018 9:54 pm
Forum: General Rate Laws
Topic: half-life
Replies: 8
Views: 176

Re: half-life

A half- life tells you how long it takes for the reactants to reach half of their initial concentrations. It can be used to predict the concentration of a substance in a reaction over time.
by Hailey Johnson
Wed Feb 21, 2018 12:23 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagrams
Replies: 3
Views: 76

Re: Cell Diagrams

The commas are used when both substances are in the same phase, use | when the substances are in different phases.
by Hailey Johnson
Wed Feb 21, 2018 12:20 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Oxidizing vs. Reducing agent
Replies: 1
Views: 70

Oxidizing vs. Reducing agent

Can someone help clarify the difference between an oxidizing and reducing agent? Also, how do we use cell potential to determine what is an oxidizing and what is a reducing agent?
by Hailey Johnson
Wed Feb 21, 2018 12:18 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Example 14.8 [ENDORSED]
Replies: 1
Views: 84

Example 14.8 [ENDORSED]

In example 14.8 from the book why do we reverse the second half-reaction if it has a higher cell potential than the first half-reaction?
by Hailey Johnson
Sun Feb 18, 2018 6:19 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: State Functions
Replies: 3
Views: 134

State Functions

Why is being a state function an important property?
by Hailey Johnson
Sun Feb 18, 2018 6:17 pm
Forum: Phase Changes & Related Calculations
Topic: Specific heat of water or ice?
Replies: 6
Views: 183

Re: Specific heat of water or ice?

Use the specific heat of ice when the water is a solid and it melting, and use the specific heat of water when it is in its liquid form.
by Hailey Johnson
Sun Feb 18, 2018 6:15 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell diagrams
Replies: 1
Views: 55

Cell diagrams

Why does the anode go on the left and the cathode go on the right in a cell diagram?
by Hailey Johnson
Sun Feb 11, 2018 11:12 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Homework Problem 9.65
Replies: 2
Views: 87

Re: Homework Problem 9.65

Knowing whether something will be more or less stable as T increases depends on delta S. Use the equation delta G= delta H -TdeltaS. If delta S is negative, then -TdeltaS will be positive and as T increases so will the positive value of -TdeltaS, causing the compound to be less stable. If delta S is...
by Hailey Johnson
Sun Feb 11, 2018 11:07 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 9.81
Replies: 2
Views: 86

9.81

In the solutions manual we write the reaction 4Fe3O4 + O2----> 6Fe2O3. Can someone explain why Fe3O4 is on the reactant side and not Fe2O3?
by Hailey Johnson
Sun Feb 11, 2018 4:02 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Stable vs Unstable
Replies: 4
Views: 123

Stable vs Unstable

How does the stability of a compound relate to its free energy? I read this section in the book, but am still having trouble connecting the two.
by Hailey Johnson
Sat Feb 03, 2018 4:49 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 9.52
Replies: 3
Views: 99

9.52

This problem from the book asks " Explain how an endothermic reaction can be spontaneous." Since this is an even numbered problem we don't have the answer to this question. Can someone explain this concept for me?
by Hailey Johnson
Sat Feb 03, 2018 4:44 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Universe [ENDORSED]
Replies: 3
Views: 132

Re: Universe [ENDORSED]

The universe is an isolated system because it has no boundaries that could be used to distinguish it from its surroundings, and, therefore, it cannot exchange energy or matter with its surroundings.
by Hailey Johnson
Sat Feb 03, 2018 4:41 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Test Number 1
Replies: 9
Views: 267

Test Number 1

I need someone to explain a concept question from test 1. For the question that asks if heat is being transferred during the expansion of a balloon when temperature is constant I answered that heat wasn't being transferred, but got it wrong. Can someone tell me how heat is being transferred even tho...
by Hailey Johnson
Sun Jan 28, 2018 6:07 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Work done by Reversible vs. Irreversible Reactions
Replies: 4
Views: 121

Work done by Reversible vs. Irreversible Reactions

Hi, I missed a few minutes of a lecture last week and missed Dr. Lavelle talking about this concept in detail. Can someone please explain to me why a reversible reaction does more work than an irreversible reaction.
by Hailey Johnson
Wed Jan 24, 2018 3:07 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: C(deltaT) vs mC(deltaT)
Replies: 4
Views: 159

Re: C(deltaT) vs mC(deltaT)

Heat capacity is just heat added divided by the change in temperature. For example, if it takes 30 calories to raise the temperature of a substance 5 degrees Celsius, then the heat capacity is 6 calories per degree Celsius. The specific heat capacity is the heat capacity per unit of mass or moles. I...
by Hailey Johnson
Sun Jan 21, 2018 10:52 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Homework Problem
Replies: 2
Views: 98

Homework Problem

Can someone please explain ch8 problem 29 please?
by Hailey Johnson
Sun Jan 21, 2018 4:05 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: self test 8.7B
Replies: 2
Views: 106

self test 8.7B

Hi I'm doing the practice problems in the book and there isn't an answer available for self-test 8.7B. Can anyone who did that problem tell me what the change in enthalpy is?
by Hailey Johnson
Sun Jan 21, 2018 3:24 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Intensive vs. Extensive
Replies: 3
Views: 158

Intensive vs. Extensive

Can someone explain the difference between and extensive and an intensive property for me please?
by Hailey Johnson
Sun Jan 14, 2018 11:18 pm
Forum: Administrative Questions and Class Announcements
Topic: Textbook Question
Replies: 1
Views: 97

Textbook Question

I am using the 7th edition of the textbook. Does anyone know if it is the same as the 6th edition and ok to use for this class?
by Hailey Johnson
Sun Jan 14, 2018 2:38 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Systems
Replies: 3
Views: 167

Systems

I'm having trouble differentiating between closed and isolated systems. Can someone give me some examples of the two?
by Hailey Johnson
Sun Jan 14, 2018 2:35 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Systems
Replies: 7
Views: 250

Re: Systems

Boiling water in a pot without a lid is another example.

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