Search found 31 matches

by Abel Thomas 2C
Wed Mar 14, 2018 5:22 pm
Forum: Calculating Work of Expansion
Topic: Conditions for reversible vs. irreversible [ENDORSED]
Replies: 1
Views: 217

Conditions for reversible vs. irreversible [ENDORSED]

From the review session 2 days ago, he stated about three conditions that can differentiate reversible or irreversible expansion. For example, one of the conditions was speed. What are the conditions, and can someone explain why? I was also confused why delta S= 0 for reversible expansion.
by Abel Thomas 2C
Mon Mar 12, 2018 2:18 pm
Forum: Balancing Redox Reactions
Topic: Reduction Potential [ENDORSED]
Replies: 2
Views: 124

Re: Reduction Potential [ENDORSED]

I think the reduction potential of Fe will be a different value altogether, since reducing Fe would require adding even more electrons.
by Abel Thomas 2C
Mon Mar 12, 2018 2:13 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: Greater Residual Entropy: NO or BF3
Replies: 2
Views: 168

Re: Greater Residual Entropy: NO or BF3

At 0K all residual entropy is from the amount of states available to the system. NO has a resonance between a double and a triple bond and is a non-symmetric system, while BF3 only has 1 configuration which is symmetric.
by Abel Thomas 2C
Mon Mar 12, 2018 2:10 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Identigying Anode/Cathode when just given species names and concentrations
Replies: 4
Views: 202

Re: Identigying Anode/Cathode when just given species names and concentrations

I think for these types of problems we will be given a sheet of half-reactions. The larger the cell potential is for the specific half reaction, the more likely it is to be reduced. Thus, we can say that this half-reaction occurs at the cathode. Therefore, the other half-reaction will occur at the a...
by Abel Thomas 2C
Mon Mar 05, 2018 12:43 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: k'
Replies: 4
Views: 139

Re: k'

The book states: "The rate law for a pseudo-first-order reaction is much easier to analyze than the
true rate law because it depends on the concentration of only one substance."
by Abel Thomas 2C
Mon Mar 05, 2018 12:37 pm
Forum: First Order Reactions
Topic: Example 15.4
Replies: 3
Views: 150

Example 15.4

Since we are not allowed to use a graphing calculator, how would we determine whether the problem in example 15.4 was first order? Would we be told that the graph is first order or that it is linear?
by Abel Thomas 2C
Mon Mar 05, 2018 12:33 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Quiz 3
Replies: 3
Views: 150

Re: Quiz 3

The test will cover all material from 15.1 to 15.6.
by Abel Thomas 2C
Sun Mar 04, 2018 3:41 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: 15.47
Replies: 1
Views: 85

Re: 15.47

This might have to do with the fact that the chlorine ion is a conjugate of a strong acid so it would remain neutral in a solution.
by Abel Thomas 2C
Sun Mar 04, 2018 3:27 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 15.67 b
Replies: 1
Views: 81

Re: 15.67 b

Rate enhancement is lower at higher temperatures because the average kinetic energy of the particles is already high. Thus, there are fewer ways to increase the rate of the reaction. When the temperature is low, you can increase the rate of the reaction more significantly.
by Abel Thomas 2C
Sun Mar 04, 2018 3:23 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: slow reaction mechanisms
Replies: 4
Views: 174

Re: slow reaction mechanisms

This is because the total reaction can only go as fast as it's slowest reaction. Thus, the overall rate law is mostly dependent on its slowest reaction mechanism.
by Abel Thomas 2C
Tue Feb 20, 2018 11:37 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Standard Reduction Potential
Replies: 3
Views: 107

Re: Standard Reduction Potential

Yes, the book states: "...the most negative-the most strongly reducing-are usually found toward the left of the periodic table, and the most positive-the most oxidizing-are found toward the upper right." Look at pg. 580 if you need further clarification.
by Abel Thomas 2C
Tue Feb 20, 2018 11:18 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Standard Potential of a couple
Replies: 3
Views: 122

Re: Standard Potential of a couple

The book states: "The more negative the potential, the greater is the electron-donating power of the oxidation half-reaction and therefore the more strongly reducing the redox couple (that is, the stronger the tendency for the half-reaction to occur as an oxidation)".
by Abel Thomas 2C
Tue Feb 20, 2018 11:14 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Calculating lnQ in Homework 14.37 and 14.41
Replies: 1
Views: 87

Re: Calculating lnQ in Homework 14.37 and 14.41

Regardless of whether pressure or M is used, the ratio of products to reactants must still be the same. Thus, the value of Q remains the same as well.
by Abel Thomas 2C
Fri Feb 16, 2018 2:20 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell diagram acidic/basic
Replies: 3
Views: 120

Re: Cell diagram acidic/basic

Yes because their relative concentrations are necessary for the proper balance of electrons in the half reactions.
by Abel Thomas 2C
Fri Feb 16, 2018 2:13 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Concentration Cells
Replies: 2
Views: 136

Re: Concentration Cells

The nerve cell is actually a good example of a concentration cell. The differences of the concentrations of Na+ and K+ inside and outside the cell create the voltage necessary for the cell's action potential.
by Abel Thomas 2C
Fri Feb 16, 2018 2:08 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Nernst equation
Replies: 2
Views: 124

Re: Nernst equation

ln and log are interchangeable in this equation. The only difference between the two is that log has 10 as its base and ln has e as its base. Thus, the equations are essentially the same and will get the same answer.
by Abel Thomas 2C
Sun Feb 11, 2018 6:06 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Standard Conditions and Temperature
Replies: 5
Views: 637

Re: Standard Conditions and Temperature

KayleeMcCord1F wrote:Also, how should we know when to leave answers in terms of J vs. kJ?

It usually does not matter unless the question specifically asks for one or the other.
by Abel Thomas 2C
Sun Feb 11, 2018 6:04 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 4 on Midterm Review Worksheet
Replies: 1
Views: 148

4 on Midterm Review Worksheet

What was the value for delta S for #4 on the practice midterm worksheet from sunday's review session and how would you calculate it?
by Abel Thomas 2C
Tue Jan 30, 2018 12:15 am
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: Limit of Entropy as temperature approaching 0 K
Replies: 2
Views: 141

Re: Limit of Entropy as temperature approaching 0 K

As the temperature approaches 0 K, entropy is decreasing because the number of possible states decreases. Since, the thermal energy is decreasing, you are going from a less ordered system to more ordered system. If the system was at 0 K, or absolute zero, the system would be perfectly ordered. Think...
by Abel Thomas 2C
Tue Jan 30, 2018 12:04 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: isothermal
Replies: 3
Views: 158

Re: isothermal

Yes you are correct. deltaU=0 in an isothermal system.
by Abel Thomas 2C
Mon Jan 29, 2018 11:55 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: standard Gibbs free energy of reaction
Replies: 1
Views: 101

Re: standard Gibbs free energy of reaction

The Gibbs free energy of a reaction is the free energy of the products-the free energy of the reactant. If you look at a reaction curve, the energy of the reaction will increase in order the activation energy to be reached so that the reactants may react to become the products. Then after the reacti...
by Abel Thomas 2C
Fri Jan 26, 2018 2:31 pm
Forum: Phase Changes & Related Calculations
Topic: Carbon as graphite [ENDORSED]
Replies: 7
Views: 337

Re: Carbon as graphite [ENDORSED]

In graphite, carbon is sp2 hybridized and possesses free electrons which are delocalized. In diamond, carbon is sp3 hybridized and there are no free electrons. Delocalization is what makes graphite more stable than diamond, since there are more van der waals interactions.
by Abel Thomas 2C
Fri Jan 26, 2018 2:11 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Reversible and Irreversible
Replies: 3
Views: 152

Re: Reversible and Irreversible

Another way to think about it is, for a reversible process, the system is always in equilibrium with its surroundings. For an irreversible process, on the other hand, there will always be an entropy change.
by Abel Thomas 2C
Fri Jan 26, 2018 2:06 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Entropy Question [ENDORSED]
Replies: 3
Views: 135

Entropy Question [ENDORSED]

Why are there a greater number of states when entropy increases? Can someone specify what this means?
by Abel Thomas 2C
Tue Jan 16, 2018 1:47 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: HW Ch.8 #59 and 63
Replies: 7
Views: 307

Re: HW Ch.8 #59 and 63

I think generally we have to give the answer in kJ. You only have to give the answer in kJ/mol when the question explicitly asks you to.
by Abel Thomas 2C
Tue Jan 16, 2018 12:47 am
Forum: Calculating Work of Expansion
Topic: Ch 8.1 Solving work
Replies: 2
Views: 160

Re: Ch 8.1 Solving work

I think the textbook's answer for this problem is not precise. If you don't round till the end, W should be -0.94 kJ, so you should be correct.
by Abel Thomas 2C
Tue Jan 16, 2018 12:22 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: HW 8.21
Replies: 2
Views: 122

Re: HW 8.21

Well the negative sign could be on either side of the equation and it would still be correct. However, the problem is asking for the final temperature of the water. Thus, for the purpose of writing the equation to solve the problem, it is stated that heat lost by the system (metal) = - heat gained b...
by Abel Thomas 2C
Wed Jan 10, 2018 7:36 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Why is fusion another name for melting?
Replies: 4
Views: 214

Re: Why is fusion another name for melting?

It may have to do with the fact the etymology of the word fusion comes from the Latin "fundere" which means "melting together".
by Abel Thomas 2C
Wed Jan 10, 2018 1:59 pm
Forum: Phase Changes & Related Calculations
Topic: Temperature during Phase Change
Replies: 6
Views: 223

Temperature during Phase Change

Why does temperature remain constant during a phase change even when more heat is added?
by Abel Thomas 2C
Wed Jan 10, 2018 11:42 am
Forum: Phase Changes & Related Calculations
Topic: Endothermic Reaction
Replies: 10
Views: 1006

Re: Endothermic Reaction

One way to think about this is in terms of the average kinetic energy of the water molecules. When water is a solid in the form of ice, the average kinetic energy of the water molecules is low. When water is a liquid, the average kinetic energy of the water molecules is larger. Thus, in order for ph...

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