Search found 42 matches
- Fri Mar 16, 2018 2:21 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Quick conceptual question?
- Replies: 1
- Views: 447
Quick conceptual question?
Why is the Gibbs free energy change of water boiling at 100 celsius equal to zero?
- Thu Mar 15, 2018 5:09 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: question 14.97
- Replies: 2
- Views: 1043
question 14.97
Question 14.97 is Use the data in Appendix 2B and the fact that, for the half-reaction F2(g) + 2 H^(+)(aq) + 2e -> S 2 HF(aq), E standard =3.03 V, to calculate the value of Ka for HF.How are we supposed to determine which half-reaction is the anode and which is the cathode? I don't understand why we...
- Wed Mar 14, 2018 5:35 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Question 14.41 [ENDORSED]
- Replies: 2
- Views: 1299
Question 14.41 [ENDORSED]
In question 14.41 part be you are given the concentration cell of H2, why is n=1 if the half reactions are are H2+2e -> 2H+. Shouldn't the n=2?
- Tue Mar 13, 2018 2:30 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: question 15.47
- Replies: 4
- Views: 456
question 15.47
why is the Cl ion not included in the overall reaction, nor is it written as an intermediate in the solution manual. What happened to the Cl ion?
- Mon Mar 12, 2018 3:53 pm
- Forum: Balancing Redox Reactions
- Topic: Balancing redox reactions in question 14.13
- Replies: 2
- Views: 383
Balancing redox reactions in question 14.13
For part d of question 14.13, where you are asked to write the half reactions of (d) Au(+) → Au + Au(3+), how do we know that one of the half-reactions is Au → Au(3+) + 3e instead of Au(+) → Au(3+) + 2e. I assumed that both half reactions would begin with Au(+), how should I have known that one was ...
- Mon Mar 12, 2018 2:12 pm
- Forum: Balancing Redox Reactions
- Topic: Reduction Potential [ENDORSED]
- Replies: 2
- Views: 337
Reduction Potential [ENDORSED]
If the reduction potential of Fe (2+) in [Fe (2+) + 2e → Fe] is -.44, does that mean that the reduction potential of Fe is positive .44. Or will the reduction potential of Fe also be -.44?
- Sun Mar 11, 2018 3:46 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: standard cell potential
- Replies: 1
- Views: 255
Re: standard cell potential
Because E is not a state function.
- Sun Mar 11, 2018 3:42 am
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: change in entropy
- Replies: 1
- Views: 331
Re: change in entropy
It depends on the entropy equation that is being used.
- Sun Mar 11, 2018 3:39 am
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: residual entropy
- Replies: 2
- Views: 684
Re: residual entropy
Residual entropy is essentially the disorder of a molecule, near absolute zero, that is the result of it's different possible microstates. Whenever a question is given on residual entropy it is usually asking you to measure entropy through the amount of microstates in a molecule(s). I believe that h...
- Mon Mar 05, 2018 4:04 pm
- Forum: General Rate Laws
- Topic: Are there any textbook problems involving pseudo reactions?
- Replies: 1
- Views: 393
Are there any textbook problems involving pseudo reactions?
Are there any textbook problems involving pseudo reactions? I haven't been able to find one in the assigned homework and would like some practice. Any help would be appreciated.
- Sat Mar 03, 2018 5:36 pm
- Forum: General Rate Laws
- Topic: Test 3
- Replies: 2
- Views: 421
Re: Test 3
My TA said it's fair game because it's technically in the section.
- Sat Mar 03, 2018 5:33 pm
- Forum: Second Order Reactions
- Topic: Non-integer orders [ENDORSED]
- Replies: 3
- Views: 533
Re: Non-integer orders [ENDORSED]
My TA said that it's very likely not relevant to the problems that will be tested.
- Sat Mar 03, 2018 5:31 pm
- Forum: Zero Order Reactions
- Topic: slope
- Replies: 9
- Views: 4751
Re: slope
Whatever it takes to make k positive
- Sat Mar 03, 2018 5:28 pm
- Forum: First Order Reactions
- Topic: Half Lives
- Replies: 2
- Views: 395
Re: Half Lives
Because decay is typically a first order reaction
- Sun Feb 25, 2018 12:10 am
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: kinetics
- Replies: 5
- Views: 721
Re: kinetics
They both play a role in determining the extent of reactions
- Sun Feb 25, 2018 12:06 am
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3006241
Re: Post chem jokes here
Iron you glad I didn't say copper?
- Mon Feb 19, 2018 3:40 pm
- Forum: Balancing Redox Reactions
- Topic: Half reaction of O3 to O2
- Replies: 1
- Views: 961
Half reaction of O3 to O2
In question 14.5 the balanced half reaction for O3 (g) --> O2 (g) is H2O (l) + O3 (g) + 2e- --> O2 (g) + 2OH- (aq) . How are we supposed to know that it takes 2 elections to form O2. Where is the number 2 coming from?
- Mon Feb 19, 2018 12:59 pm
- Forum: Balancing Redox Reactions
- Topic: Are we going to be given the periodic table for test 2?
- Replies: 1
- Views: 415
Are we going to be given the periodic table for test 2?
Are we going to be given the periodic table for test 2?
- Sat Feb 17, 2018 12:52 am
- Forum: Balancing Redox Reactions
- Topic: Oxidizing vs. Reducing Agent
- Replies: 7
- Views: 836
Re: Oxidizing vs. Reducing Agent
Oxidizing agents help substances oxidize by being reduced. The opposite is true for reducing agents.
- Sat Feb 17, 2018 12:49 am
- Forum: Calculating Work of Expansion
- Topic: Isolated System
- Replies: 5
- Views: 663
Re: Isolated System
Yes, but be careful determining whether a question is asking for the change in energy of the system or a reaction within the system. Because all those terms could very well not be equal to zero for to a reaction within an ideal bomb calorimeter. But the total energy of the bomb calorimeter will be u...
- Tue Feb 13, 2018 11:09 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Practice Midterm W18 by Lyndon and Michael (Q 1B)
- Replies: 2
- Views: 513
Re: Practice Midterm W18 by Lyndon and Michael (Q 1B)
consider the q=mcT + 0.5(mH)
mH is divided by 2 because only half of the ice cream, make sure your answer is in line with the units that the question is asking
mH is divided by 2 because only half of the ice cream, make sure your answer is in line with the units that the question is asking
- Tue Feb 13, 2018 3:28 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Is it possible to force a reaction that will decrease the entropy of the universe?
- Replies: 1
- Views: 281
Is it possible to force a reaction that will decrease the entropy of the universe?
Is it possible to force a reaction that will decrease the entropy of the universe? Or would that defy the second law of thermodynamics
- Sat Feb 10, 2018 11:33 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Delta G
- Replies: 4
- Views: 533
Re: Delta G
When Delta =0 it means that neither the formation of products nor reactants will be favored. This relates to our previous understanding of equilibrium from Chem 14 A where we understood that at equilibrium the rate of creation of products and reactants will be stable.
- Wed Feb 07, 2018 7:31 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Will dissolving a salt in water affect the entropy of the water?
- Replies: 3
- Views: 1399
Will dissolving a salt in water affect the entropy of the water?
If I were to dissolve a salt in water by stirring it (let's say NaCl), will I be affecting the entropy of the water that surrounds it
- Wed Feb 07, 2018 7:29 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: 9.63
- Replies: 4
- Views: 459
Re: 9.63
A negative change in Gibbs free energy means that the product will be spontaneously favoured and therefore more stable
- Wed Feb 07, 2018 5:26 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Concept of constant P and "thermally insulated" [ENDORSED]
- Replies: 1
- Views: 333
Concept of constant P and "thermally insulated" [ENDORSED]
Why is constant pressure and thermally insulated mentioned in question 9.43 Suppose that 50.0 g of H2O(l) at 20.0 C is mixed with 65.0 g of H2O(l) at 50.0 C at a constant atmospheric pressure in a thermally insulated vessel. Calculate S and Stot for the process. What does having a constant pressur...
- Sun Feb 04, 2018 12:12 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Example from Wednesday's Lecture
- Replies: 3
- Views: 354
Re: Example from Wednesday's Lecture
I believe he was just demonstrating that that specific temperature is a threshold. A student asked and professor said that you could also set up an inequality; the final answer would be the same .
- Sun Feb 04, 2018 12:08 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: What does it mean for a reaction to be "thermodynamically favored?"
- Replies: 6
- Views: 31406
Re: What does it mean for a reaction to be "thermodynamically favored?"
It means that it is energetically favorable and naturally occurring ( spontaneous). This is represented by a negative delta G
- Sun Feb 04, 2018 12:05 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Spontaneous
- Replies: 14
- Views: 1932
Re: Spontaneous
Spontaneous simply means that it can naturally occur without outside influences. It makes sense that because everything in nature attempts to have as low of an energy level as it can, losing free energy ( negative Delta G) will happen naturally
- Sun Feb 04, 2018 12:01 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: G at minimum
- Replies: 6
- Views: 554
Re: G at minimum
I like to also think about the fact that equilibrium is measured where the change in G is equal to 0. This also explains why negative G values are spontaneous, because they are approaching a lower number (where dG=0). If there is less free energy it is safe to assume that there is less potential for...
- Sat Jan 27, 2018 11:44 pm
- Forum: Calculating Work of Expansion
- Topic: The integral equation
- Replies: 8
- Views: 699
Re: The integral equation
The integral is an equation that gave origin to several others we derived in class. It was meant to help our comprehension, yet we do not need it in our calculations.
- Sat Jan 27, 2018 11:41 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: W as a maximum
- Replies: 3
- Views: 422
Re: W as a maximum
This signifies that when there are more possible states available that a substance will be more stable (at equilibrium)
- Sat Jan 27, 2018 11:35 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Reversible Vs Irreversible
- Replies: 3
- Views: 430
Re: Reversible Vs Irreversible
I believe that being at thermodynamic equilibrium (constant heat) is part of the definition of a reversible reaction whereas it is not required for irreversible.
- Sat Jan 27, 2018 11:30 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Why do we calculate reversible vs irreversible expansion?
- Replies: 1
- Views: 226
Why do we calculate reversible vs irreversible expansion?
In thermodynamics we are often calculating for reversible expansion even though professor said that most real life cases are irreversible. Why are we calculating for maximum work if it might be less accurate?
- Mon Jan 22, 2018 6:26 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Does Dr Lavelle post his PowerPoints online
- Replies: 1
- Views: 154
Does Dr Lavelle post his PowerPoints online
Does Dr Lavelle post his PowerPoints online? I can't seem to find it
- Sat Jan 20, 2018 9:25 pm
- Forum: Calculating Work of Expansion
- Topic: Work done on / work done by system
- Replies: 5
- Views: 570
Re: Work done on / work done by system
Work done on a system means that the internal energy of the system will increase, because the surroundings are placing work unto the system.
Work done by a system means that the internal energy of the system will decrease, because the system is placing work unto the surroundings.
Work done by a system means that the internal energy of the system will decrease, because the system is placing work unto the surroundings.
- Sat Jan 20, 2018 9:21 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: When is the change in work or heat = to zero?
- Replies: 2
- Views: 261
Re: When is the change in work or heat = to zero?
A Bomb Calorimeter is a isolated system, meaning that no heat or work will be exchanged with its surroundings, because q and w are a measure of energy transfer to surroundings it is safe to assume that the change in work and heat will be zero.
- Sat Jan 20, 2018 9:12 pm
- Forum: Calculating Work of Expansion
- Topic: Irreversible and Reversible Processes
- Replies: 4
- Views: 482
Re: Irreversible and Reversible Processes
An irreversible process would be as if I took a single 10g weight off of a balloon, allowing it to quickly expand. While a reversible process would be as if I individually removed from a balloon infinitely small weights that all collectively added up to 10g. The work in the second case would be much...
- Sat Jan 13, 2018 6:45 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: When considering enthalpy (Δ H=q), is the letter "H" or "ΔH" Enthalpy?
- Replies: 3
- Views: 405
When considering enthalpy (Δ H=q), is the letter "H" or "ΔH" Enthalpy?
When considering enthalpy (Δ H=q), is the letter "H" or "ΔH" Enthalpy? Online the definition of enthalpy is given as a measure of the internal heat of a system, but whenever we are talking about enthalpy it has to do with change. Sometime Professor call "ΔH" enthalpy an...
- Sat Jan 13, 2018 6:35 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Intensive vs Extensive [ENDORSED]
- Replies: 4
- Views: 378
Re: Intensive vs Extensive [ENDORSED]
We generally prefer extensive properties in chemistry because they are more specific. I would guess that your second question depends on the specific chemistry question you're answering.
- Sat Jan 13, 2018 6:31 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Δ H=q
- Replies: 3
- Views: 402
Re: Δ H=q
You are right to determine that enthalpy is a state function while heat is not. The only reason that they are equivalent in the equation (Δ H=q) is because it is at a constant pressure, mathematically leading allowing for the equation to be derived. Just because they are different types of functions...
- Sat Jan 13, 2018 6:22 pm
- Forum: Phase Changes & Related Calculations
- Topic: Why can state properties be added?
- Replies: 11
- Views: 1239
Re: Why can state properties be added?
Think about the example Professor gave in class with altitude. Altitude can be measured using a difference of distances, ie subtraction. You can also get altitudes, a state function, by adding two smaller altitudes. Try not to overthink it