Search found 31 matches

Fri Mar 16, 2018 12:42 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Midterm Question
Replies: 2
Views: 328

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?
Fri Mar 16, 2018 12:35 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Identifying a catalyst in a reaction
Replies: 4
Views: 3337

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?
Fri Mar 16, 2018 12:33 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Midterm Question
Replies: 2
Views: 328

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?
Fri Mar 16, 2018 12:31 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 15.63
Replies: 1
Views: 174

15.63

In problem 15.63 in the textbook the solution includes the value -0.59. Can anyone tell me where this comes from?
Sun Mar 11, 2018 10:15 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Midterm Question
Replies: 4
Views: 352

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?
Sun Mar 11, 2018 2:04 pm
Forum: Second Order Reactions
Topic: Half life of second order reactions
Replies: 8
Views: 793

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.
Sun Mar 11, 2018 2:01 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Reaction Mechanisms [ENDORSED]
Replies: 2
Views: 169

Reaction Mechanisms[ENDORSED]

Why would we choose to use to use the pre-equilibrium method vs. the stable-state method? What is the difference?
Tue Mar 06, 2018 3:46 pm
Forum: First Order Reactions
Topic: Ordered Reactions
Replies: 1
Views: 173

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...
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: 586

Q vs. K

What is the difference between Q and K and how do we know which one to use in a given problem?
Sat Mar 03, 2018 9:55 pm
Forum: First Order Reactions
Topic: Reaction Orders [ENDORSED]
Replies: 2
Views: 181

Reaction Orders[ENDORSED]

Can someone help clarify what the different reaction orders mean and how we use them?
Sat Mar 03, 2018 9:54 pm
Forum: General Rate Laws
Topic: half-life
Replies: 8
Views: 413

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.
Wed Feb 21, 2018 12:23 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagrams
Replies: 3
Views: 179

Re: Cell Diagrams

The commas are used when both substances are in the same phase, use | when the substances are in different phases.
Wed Feb 21, 2018 12:20 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Oxidizing vs. Reducing agent
Replies: 1
Views: 134

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?
Wed Feb 21, 2018 12:18 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Example 14.8 [ENDORSED]
Replies: 1
Views: 166

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?
Sun Feb 18, 2018 6:19 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: State Functions
Replies: 3
Views: 266

State Functions

Why is being a state function an important property?
Sun Feb 18, 2018 6:17 pm
Forum: Phase Changes & Related Calculations
Topic: Specific heat of water or ice?
Replies: 6
Views: 468

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.
Sun Feb 18, 2018 6:15 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell diagrams
Replies: 1
Views: 103

Cell diagrams

Why does the anode go on the left and the cathode go on the right in a cell diagram?
Sun Feb 11, 2018 11:12 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Homework Problem 9.65
Replies: 2
Views: 173

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...
Sun Feb 11, 2018 11:07 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 9.81
Replies: 2
Views: 172

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?
Sun Feb 11, 2018 4:02 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Stable vs Unstable
Replies: 4
Views: 607

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.
Sat Feb 03, 2018 4:49 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 9.52
Replies: 3
Views: 216

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?
Sat Feb 03, 2018 4:44 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Universe [ENDORSED]
Replies: 3
Views: 245

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.
Sat Feb 03, 2018 4:41 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Test Number 1
Replies: 9
Views: 502

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...
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: 287

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.
Wed Jan 24, 2018 3:07 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: C(deltaT) vs mC(deltaT)
Replies: 4
Views: 1093

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...
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: 140

Homework Problem

Sun Jan 21, 2018 4:05 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: self test 8.7B
Replies: 2
Views: 186

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?
Sun Jan 21, 2018 3:24 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Intensive vs. Extensive
Replies: 3
Views: 401

Intensive vs. Extensive

Can someone explain the difference between and extensive and an intensive property for me please?
Sun Jan 14, 2018 11:18 pm
Forum: Administrative Questions and Class Announcements
Topic: Textbook Question
Replies: 1
Views: 151

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?
Sun Jan 14, 2018 2:38 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Systems
Replies: 3
Views: 284

Systems

I'm having trouble differentiating between closed and isolated systems. Can someone give me some examples of the two?
Sun Jan 14, 2018 2:35 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Systems
Replies: 7
Views: 500

Re: Systems

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