Search found 141 matches
- Fri Mar 12, 2021 3:54 am
- Forum: First Order Reactions
- Topic: Textbook Question 7.21
- Replies: 2
- Views: 165
Re: Textbook Question 7.21
I'm confused on this as well
- Thu Mar 11, 2021 4:02 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Catalyst Reverse Reaction
- Replies: 3
- Views: 269
Catalyst Reverse Reaction
Why do Catalyst increase the rate of reverse reaction as well as forward reaction?
How does it work in terms of energy graph?
How does it work in terms of energy graph?
- Wed Mar 10, 2021 10:52 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Bottle Neck Effect and Reaction Rate Equation
- Replies: 2
- Views: 222
Bottle Neck Effect and Reaction Rate Equation
When writing the reaction rate equation for bottle neck effect
I understand that you have to change the intermediate into its reverse since it is in equilibrium.
However, I don't understand to how you can get the (k1 * k2) / k'1 value
Will the k'1 be given?
I understand that you have to change the intermediate into its reverse since it is in equilibrium.
However, I don't understand to how you can get the (k1 * k2) / k'1 value
Will the k'1 be given?
- Tue Mar 09, 2021 5:58 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Textbook 6N.7
- Replies: 4
- Views: 307
Re: Textbook 6N.7
for this one, Professor Lavelle mentioned the reason in the "Namaste" post if you search Namaste on Chem community, youll see the answer But the basic reason is because 2H+ --> 2H+ is being cancelled out to 1H+ But if you use 2H+ you still get the same answer since you have to square the Q
- Tue Mar 09, 2021 6:33 am
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Textbook Question 7C.11
- Replies: 1
- Views: 211
Textbook Question 7C.11
For this question part B What does it mean when the answer states "At equilibrium, the "rates" of the forward and reverse reactions are equal. NOT THE RATE CONSTANTS?" I get why they should not be equal since that would mean K would always equal to 0 for every equilibrium reactio...
- Mon Mar 08, 2021 12:35 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Rate Limiting Steps
- Replies: 6
- Views: 498
Re: Rate Limiting Steps
Hi! The rate limiting step is one of the elementary steps within a reaction mechanism. The rate limiting step is always the slowest step of the mechanism which is used to determine the rate of the overall reaction and limits the speed at which the reaction is occurring. The other elementary steps o...
- Mon Mar 08, 2021 12:23 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Molecularity and Mechanism
- Replies: 2
- Views: 221
Molecularity and Mechanism
How are molecularities and mechanisms related?
Molecularities are number of species in elementary steps
and
Mechanisms are sequences of elementary steps by which a chemical reaction occurs.
Do we use molecularities to find mechanisms? Are mechanisms numbers?
Molecularities are number of species in elementary steps
and
Mechanisms are sequences of elementary steps by which a chemical reaction occurs.
Do we use molecularities to find mechanisms? Are mechanisms numbers?
- Mon Mar 08, 2021 12:20 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Rate Limiting Steps
- Replies: 6
- Views: 498
Rate Limiting Steps
What are rate limiting steps? In today's lecture when professor was talking about ways to approach proposed reaction mechanism, he mentions about identifying rate limiting step, using rate law of rate-limiting step as overall rate and compare model with experiment I didn't really get what rate-limit...
- Sun Mar 07, 2021 4:36 am
- Forum: Second Order Reactions
- Topic: Textbook Question 7B 13
- Replies: 2
- Views: 341
Textbook Question 7B 13
For this question, I used half life equation in order to find the time it would take for the concentration to decrease to one-sixteenth of its original, which would be (1/2)^4, making the time 4 x 50.5 seconds. However, the answer used the Second order integrated equation, making the answer equal to...
- Sat Mar 06, 2021 11:30 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Textbook Question 6N.7 Part B [ENDORSED]
- Replies: 3
- Views: 602
Re: Textbook Question 6N.7 Part B [ENDORSED]
Correct, H 2 cancels and one has 2H + ----> 2H + . Which can also be written as: H + ----> H + and E stays the same (intensive property) Remember E stays the same if one multiplies a redox reaction by some multiple (e.g., by 2). Intensive property. You can also see this mathematically. Use the Nern...
- Sat Mar 06, 2021 9:16 am
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Reaction Mechanism
- Replies: 5
- Views: 451
Reaction Mechanism
What exactly is a reaction mechanism in definition?
Also, why is overall rate law the rate law of the slowest step?
Also, why is overall rate law the rate law of the slowest step?
- Sat Mar 06, 2021 7:49 am
- Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
- Topic: Textbook Question 6.63 [ENDORSED]
- Replies: 1
- Views: 285
Textbook Question 6.63 [ENDORSED]
For this question,
Why is concentration of A close to HA in buffer system?
Why is concentration of A close to HA in buffer system?
- Sat Mar 06, 2021 7:31 am
- Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
- Topic: Textbook Question 6.61
- Replies: 1
- Views: 227
Textbook Question 6.61
How is the wording of the exercise suggesting that K+ ions participate in an electrolyte concentration cell reaction?
I am having trouble understanding how we know if a reaction is electrolyte concentration cell reaction and if we need electrodes for the electrolyte concentration cell reaction
I am having trouble understanding how we know if a reaction is electrolyte concentration cell reaction and if we need electrodes for the electrolyte concentration cell reaction
- Sat Mar 06, 2021 7:28 am
- Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
- Topic: Textbook Question 6.57
- Replies: 2
- Views: 335
Textbook Question 6.57
For this question 1. Is the given half reaction reversed to oxidation even thought it has a greater reduction potential BECAUSE the question is asking for the value of Ka for HF? 2. What is the relationship between Ka and K? because in the answer, in order to find Ka, the calculated K was square roo...
- Sat Mar 06, 2021 7:05 am
- Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
- Topic: Textbook Question 6.51
- Replies: 1
- Views: 251
Textbook Question 6.51
For this question the answer states "A negatively charged electrolyte flows from the cathode to the anode." First of all, I was confused to how electrolytes move. I realized that salt bridge is used to balance out the oxidated ions but I still didn't really get how the electrolytes flow Se...
- Sat Mar 06, 2021 2:28 am
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Textbook Question 6M. 13 Part c
- Replies: 4
- Views: 265
Re: Textbook Question 6M. 13 Part c
I see what you are saying about higher reduction potential should be reduction and therefore the cathode, but for this question, I think that it wants you to use the given rxn equation. Therefore, it is asking you to look at which one actually get oxidized and reduced in this rxn and then say which...
- Sat Mar 06, 2021 2:25 am
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Textbook Question 6N.7 Part B [ENDORSED]
- Replies: 3
- Views: 602
Textbook Question 6N.7 Part B [ENDORSED]
For this question, I thought the moles of electrons, or the n value, should be 2, not 1 since there are 2 Hydrogens in 1 H2
But the question puts 1 as the n value, making the E naught cell = 6 x 10^-2
Why do you not divide it by 2?
But the question puts 1 as the n value, making the E naught cell = 6 x 10^-2
Why do you not divide it by 2?
- Fri Mar 05, 2021 11:43 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Textbook Question 6M. 13 Part c
- Replies: 4
- Views: 265
Textbook Question 6M. 13 Part c
For 6M. 13 part c, the even though Pb^4+ / Pb^2+ has a greater standard reduction potential then Pb^2+/Pb, the anode, which is the one that is being oxidized, is Pb^4+ / Pb^2+
Why is it the anode?
Why is it the anode?
- Fri Mar 05, 2021 1:35 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Pseudo K
- Replies: 5
- Views: 271
Pseudo K
Why is there a difference between Pseudo K and just K
I thought if you find the graph of ln[A] vs t for the reaction (if [A] is first order)
the k would be the slope.
Is the large excess of [B] and [C] altering the slope? if so, how?
I thought if you find the graph of ln[A] vs t for the reaction (if [A] is first order)
the k would be the slope.
Is the large excess of [B] and [C] altering the slope? if so, how?
- Fri Mar 05, 2021 12:34 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: 6L 7 A
- Replies: 1
- Views: 137
6L 7 A
Hello For 6L 7 the equation is AgBr(s) --> Ag+ + Br- but the half reactions have Ag(s) in them. I get that Ag gets cancelled out from the reactant and product since there is 1 mole on each side, how do we know there will be Ag(s)? Also, why is cathode Ag+ (aq) + e- --> Ag(s)? I thought since Ag+ is ...
- Fri Mar 05, 2021 12:00 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Textbook Question 6L3 D and 6L5 C
- Replies: 1
- Views: 148
Textbook Question 6L3 D and 6L5 C
Hello I have a question for the balanced redox reaction of these two. For 6L3 D, the balanced reaction was 4H2O -> 4H+ + 4OH- and the reaction was kept this way without the 4H+ and OH- becoming 4H2O But for 6L5 C Cl2 + H2 --> 2Cl- + 2H+ becomes Cl2 + H2 --> 2HCl why does the reaction in 6L5 C have p...
- Thu Mar 04, 2021 11:38 pm
- Forum: Administrative Questions and Class Announcements
- Topic: 14B Final TextBook Questions
- Replies: 5
- Views: 430
14B Final TextBook Questions
Will Textbook Questions come out in the final as it did in the midterms?
- Thu Mar 04, 2021 11:31 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell Diagram Commas
- Replies: 9
- Views: 602
Cell Diagram Commas
For the cell diagrams with commas
ex. Ce^4+ , Ce^3+
Do their orders matter in the diagram?
Also, Do Platinum (Pt)s get used for electrodes all the time whenever the cell requires electrode and the anode is an aqueous solution?
ex. Ce^4+ , Ce^3+
Do their orders matter in the diagram?
Also, Do Platinum (Pt)s get used for electrodes all the time whenever the cell requires electrode and the anode is an aqueous solution?
- Thu Mar 04, 2021 11:01 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Textbook Question 6L 1
- Replies: 4
- Views: 311
Re: Textbook Question 6L 1
Benjamin Chen 1H wrote:n represents the number of moles of electrons transferred in a balanced redox reaction. The 2 is specific to one half reaction and the 6 is specific to the other reaction.
Thank you for the clarification Benjamin!
- Thu Mar 04, 2021 9:04 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Textbook Question 6L 1
- Replies: 4
- Views: 311
Re: Textbook Question 6L 1
Andersen Chu 2H wrote:Try writing out half reactions, n is equal to the number of electrons transferred. You should see 2 and 6 electrons being transferred in the half reactions
Does n always represent the number of moles of electrons in the equation Delta G naught = -nFE naught?
- Thu Mar 04, 2021 9:01 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Concentration vs Cell Potential
- Replies: 5
- Views: 404
Concentration vs Cell Potential
How does Concentration affect Cell Potential?
- Thu Mar 04, 2021 8:49 pm
- Forum: Zero Order Reactions
- Topic: Saturated
- Replies: 3
- Views: 315
Saturated
What does it mean when professor says that the enzyme or the catalyst are saturated?
in terms of zeroth order
in terms of zeroth order
- Thu Mar 04, 2021 7:18 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: K value
- Replies: 20
- Views: 848
K value
Will the K value always be positive?
I believe in yesterday's lecture, professor said that K value is always going to be positive, keeping the half life equation for second order from becoming a negative value.
But I thought that k value can be negative whenever a reactant decomposes etc.
I believe in yesterday's lecture, professor said that K value is always going to be positive, keeping the half life equation for second order from becoming a negative value.
But I thought that k value can be negative whenever a reactant decomposes etc.
- Thu Mar 04, 2021 1:27 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Textbook Question 6L 1
- Replies: 4
- Views: 311
Textbook Question 6L 1
For finding the standard reaction Gibbs Free Energy with the given cell potential, why is n "2" and "6" for a and b which are the number of moles of Ce and Fe?
Didn't the question ask for the Gibbs Free Energy of the cell reaction?
Didn't the question ask for the Gibbs Free Energy of the cell reaction?
- Thu Mar 04, 2021 12:53 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Electrolytic cell vs Galvanic Cell
- Replies: 2
- Views: 164
Electrolytic cell vs Galvanic Cell
What are the differences between these two cells and
once they come out in questions
how are they different in terms of solving the questions?
once they come out in questions
how are they different in terms of solving the questions?
- Wed Mar 03, 2021 10:19 pm
- Forum: Balancing Redox Reactions
- Topic: Oxidation and Reduction
- Replies: 11
- Views: 817
Oxidation and Reduction
How can a compound or a molecule be oxidyzing and reducing at the same time?
- Sun Feb 28, 2021 10:52 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Nernst Equations
- Replies: 7
- Views: 418
Nernst Equations
Hello
I was wondering when you use E (not) = RT/nFlnK
and
E = E(not) - RT/nFlnQ
I thought E not was supposed to equal zero when it is at equilibrium so I don't really get teh equation using K
I was wondering when you use E (not) = RT/nFlnK
and
E = E(not) - RT/nFlnQ
I thought E not was supposed to equal zero when it is at equilibrium so I don't really get teh equation using K
- Fri Feb 26, 2021 11:35 am
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Standard Electromotive Force
- Replies: 2
- Views: 178
Standard Electromotive Force
Professor mentions that "we want to start of with a redox reaction with a positive E not value"
I wasn't really sure to what he meant here because some of the redox reactions have negative E not values.
I wasn't really sure to what he meant here because some of the redox reactions have negative E not values.
- Thu Feb 25, 2021 7:21 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Standard Electromotive Force
- Replies: 1
- Views: 121
Standard Electromotive Force
Hello, I was watching Dr. Lavelle's lecture and I had a quick question on standard electromotive force. So professor mentions that electromotive forces are measures of voltage with respect to standard hydrogen electrode. In this standard hydrogen electrode and transfer of e- with a different cell, t...
- Thu Feb 25, 2021 6:39 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Voltage Change
- Replies: 1
- Views: 142
Voltage Change
How does Voltage change over period of time?
Also, is the E cell (V) the Voltage calculated in the beginning when everything is standardized?
Also, is the E cell (V) the Voltage calculated in the beginning when everything is standardized?
- Thu Feb 25, 2021 3:19 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Electromotive Force
- Replies: 2
- Views: 147
Electromotive Force
Could someone explain this to me? I didn't really get it from Professor
- Wed Feb 17, 2021 2:32 am
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Textbook Question 4H 11
- Replies: 2
- Views: 240
Textbook Question 4H 11
For this question, I balanced the chemical equation to 2H2 + O2 --> 2H2O and I plugged in the standard entropy values in order to find the change standard change in entropy However, I was not able to use that equation but I had to use H2 + 1/2O2 ---> H20 I thought I was able to use standard enthalpy...
- Wed Feb 17, 2021 1:53 am
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Textbook Question 4H.1
- Replies: 1
- Views: 86
Textbook Question 4H.1
what does it mean by
"HBr, because Br is more massive and contains more elementary particles than F in HF" ?
I get that it is more massive but I was having trouble understanding the "elementary particles" part.
"HBr, because Br is more massive and contains more elementary particles than F in HF" ?
I get that it is more massive but I was having trouble understanding the "elementary particles" part.
- Wed Feb 17, 2021 1:52 am
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: High and Low Pressure vs Entropy
- Replies: 3
- Views: 961
High and Low Pressure vs Entropy
Hello, I am getting confused with the comparison of same gas in different pressure in their entropy values. I guess I'm thinking of entropy as a more chaotic substance but I think I am wrong because I've been thinking that greater pressure leads to greater entropy since gas molecules will move at hi...
- Wed Feb 17, 2021 1:46 am
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Mass vs Entropy
- Replies: 8
- Views: 2366
Mass vs Entropy
Why are more Massive compounds or elements greater in molar entropy than those that have less mass?
Also, does this only apply to gas or does it apply to any state of matter?
Also, does this only apply to gas or does it apply to any state of matter?
- Wed Feb 17, 2021 1:17 am
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Textbook 4F. 17
- Replies: 1
- Views: 153
Textbook 4F. 17
Hello, for this problem
when it states to calculate the standard entropy of the vaporization of water, can I conclude that they are trying to find the entropy change from liquid water at 85 degrees Celsius to water vapor at 85 degree Celsius?
when it states to calculate the standard entropy of the vaporization of water, can I conclude that they are trying to find the entropy change from liquid water at 85 degrees Celsius to water vapor at 85 degree Celsius?
- Fri Feb 12, 2021 2:56 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Standard Gibbs Free Energy
- Replies: 8
- Views: 506
Re: Standard Gibbs Free Energy
If K is a large value, ln(K) will be a positive value. Since there is a negative in the front, -RT(+number) will be negative. If K was a value less than 1, the lnK value will be a negative number giving us -RT(-number) making it positive. Delta G (standard) can only be 0 when K=1 (because ln(1)=0) ...
- Fri Feb 12, 2021 2:41 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Standard Gibbs Free Energy
- Replies: 8
- Views: 506
Standard Gibbs Free Energy
In today's lecture, professor talked about the equation Delta G (standard) = -RT ln K, where if K value is large, then it leads to Delta G (standard) being a negatively significant value. However, I thought that delta G of a reaction at equilibrium is supposed to be 0. I don't really understand why ...
- Wed Feb 10, 2021 2:55 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Work Equation for Ideal Gas
- Replies: 5
- Views: 279
Work Equation for Ideal Gas
Hello, For Ideal gas do we have to memorize the change in constant value in front of R (gas constant) based on whether they are monoatomic or diatomic? I think professor said that if ideal gas is monoatomic its w = -n (3/2) R ln (t2/t1) in constant volume or one for constant temperature and 2 = -n (...
- Wed Feb 10, 2021 1:56 pm
- Forum: Administrative Questions and Class Announcements
- Topic: MyUCLA Grade
- Replies: 27
- Views: 1473
Re: MyUCLA Grade
i dont even see the midterm grade. I have to go into myucla to view them even though before, I was able to see all of my grades on the CCLE grade section :/
- Mon Feb 08, 2021 2:38 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Maximum amount of Work
- Replies: 4
- Views: 266
Re: Maximum amount of Work
Also, is the irreversible process always constant volume? or can the piston of the irreversible process go up, changing the volume?
I'm generally confused on understanding the reversible and irreversible processes.
I'm generally confused on understanding the reversible and irreversible processes.
- Mon Feb 08, 2021 2:37 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Constant Pressure
- Replies: 2
- Views: 121
Re: Constant Pressure
Pressure would only increase with increase in moles of gas if the volume is constant ( more gas particles in one space). However, if volume is not constant ( expanding with gas), pressure can remain constant. This is why we can apply the equation w= -P\Delta V to the system to calculate work. This ...
- Mon Feb 08, 2021 2:27 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Maximum amount of Work
- Replies: 4
- Views: 266
Maximum amount of Work
why does Irreversible process do less work than reversible reaction? I get it just with the equations as the external pressure for the irreversible pressure is significantly lower than the internal pressure. but I still don't get why reversible reaction does the maximum amount of work compared to th...
- Mon Feb 08, 2021 1:14 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Constant Pressure
- Replies: 2
- Views: 121
Constant Pressure
Hello, Professor said in lecture 11 that "If there is no change in pressure (delta P = 0) then delta U = Qp + w = delta H - P delta V however, without the increase in moles of gas, there would not be expansion, which would make delta V = 0. He stated that if number of moles of gas changed, P de...
- Mon Feb 08, 2021 1:10 pm
- Forum: Calculating Work of Expansion
- Topic: All Equations So Far
- Replies: 2
- Views: 189
All Equations So Far
Could someone list all the equations we went over in class so far? I believe we went over w = -P delta V w = - integral(vi - vf) PdV ----> COULD SOMEONE EXPLAIN WHEN YOU USE EITHER OR? I BELIEVE THEY ARE NOT INTERCHANGABLE q = mc delta T q = C delta T s = Kb ln W (W=degenerecy) delta U = q + w --> i...
- Sun Feb 07, 2021 11:21 am
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Kinetics and Thermodynamics
- Replies: 1
- Views: 105
Kinetics and Thermodynamics
Hello,
could someone explain why kinetics is time dependent while thermodynamics is time independent?
could someone explain why kinetics is time dependent while thermodynamics is time independent?
- Fri Feb 05, 2021 6:28 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Combustion = Exothermic
- Replies: 23
- Views: 857
Combustion = Exothermic
Hello, I am a little confused on why combustion is exothermic.
I thought combustion uses heat to break bonds so it was going to be endothermic.
What is the explanation to why they are exothermic reactions?
I thought combustion uses heat to break bonds so it was going to be endothermic.
What is the explanation to why they are exothermic reactions?
- Wed Feb 03, 2021 9:37 am
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Reversible and Irreversible System
- Replies: 1
- Views: 97
Reversible and Irreversible System
Hello,
I don't understand why reversible systems do maximum amount of work compared to irreversible systems.
I don't really understand what professor is saying when he says infinite steps either.
what are the differences between the reversible and irreversible systems that lead to this outcome?
I don't understand why reversible systems do maximum amount of work compared to irreversible systems.
I don't really understand what professor is saying when he says infinite steps either.
what are the differences between the reversible and irreversible systems that lead to this outcome?
- Wed Feb 03, 2021 9:24 am
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Expansion of Volume
- Replies: 2
- Views: 130
Expansion of Volume
Hello, so in case of work if the volume expands for the system, which means the internal pressure was greater than the external pressure, does that mean the system did work to the surrounding, decreasing the internal energy of the system? I am hearing from professor that if the work is being done to...
- Wed Feb 03, 2021 9:17 am
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Work Equation
- Replies: 3
- Views: 239
Work Equation
Hello, Professor said in the lecture that work = external pressure x change in volume. does pressure have to always be external? In the example that he gave, the pressure came from inside the beaker, pushing the piston outwards. Wouldnt that be called internal pressure or am I just getting confused ...
- Thu Jan 28, 2021 2:17 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Textbook 5.61
- Replies: 3
- Views: 201
Textbook 5.61
what does this mean? f) Because water is a liquid, it is by definition present at unit concentration, so changing the amount of water will not affect the reaction. As long as the glucose solution is dilute, its concentration can be considered unchanged. I understand that water is a solvent. But sinc...
- Thu Jan 28, 2021 1:48 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Textbook Question 5.39
- Replies: 1
- Views: 83
Textbook Question 5.39
In the answer key, the Kc value that it uses is
1.6 x 10^-2, which is 1 / 6.1 x 10^-3
In the chart given by the textbook *Table 5G.2*, it says the K c value is 1 / 6.1 x 10^23.
I'm confused to which one is the correct one.
1.6 x 10^-2, which is 1 / 6.1 x 10^-3
In the chart given by the textbook *Table 5G.2*, it says the K c value is 1 / 6.1 x 10^23.
I'm confused to which one is the correct one.
- Tue Jan 26, 2021 9:14 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: K greater than 1 or greater than 10^3
- Replies: 4
- Views: 269
K greater than 1 or greater than 10^3
hello I remember professor stating that if k is smaller than 10^-3 more reactants are at equilibrium than the product, which makes total sense. However, I heard that if K is greater than 1 it favors right and if its less than 1 it favors left. what is the point of division between favoring right or ...
- Mon Jan 25, 2021 2:27 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Constant Pressure vs Constant Volume
- Replies: 2
- Views: 174
Constant Pressure vs Constant Volume
I'm still confused on the Constant pressure and Constant volume calorimetry and capacities If its constant pressure capacity, does that mean that it is in open space, so its not sealed and the pressure will be the same as outer pressure, usually 1atm? Also if its constant volume, the pressure inside...
- Mon Jan 25, 2021 2:22 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Energy Question
- Replies: 1
- Views: 124
Energy Question
When the question asks
How much heat was released from the system
Do we hvae to put negative to the energy value since it is exothermic? or since the question is already asking for a negative value, do we just put the absolute value of the energy?
How much heat was released from the system
Do we hvae to put negative to the energy value since it is exothermic? or since the question is already asking for a negative value, do we just put the absolute value of the energy?
- Mon Jan 25, 2021 2:17 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Perfect System
- Replies: 5
- Views: 224
Perfect System
Professor mentioned about perfect system where the energy absorbed or released from the system will be opposite of the energy of surrounding.
do we assume that every reaction we encounter in the problems are in perfect system?
do we assume that every reaction we encounter in the problems are in perfect system?
- Mon Jan 25, 2021 2:12 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Neutralization
- Replies: 25
- Views: 1068
Neutralization
Professor mentioned in his lecture that the reaction of HCl and NaOH is neutralization reaction
What is neutralization and what makes that reaction one of it?
What is neutralization and what makes that reaction one of it?
- Mon Jan 25, 2021 1:46 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Molar heat Capacity
- Replies: 3
- Views: 175
Molar heat Capacity
when writing the Molar Heat capacity professor wrote J * k^-1 * mol^-1
I understand that the unit of energy had to change from kj to j since moles are much smaller than grams. However, why did it have to change from celsius to K? Is it the same reason?
I understand that the unit of energy had to change from kj to j since moles are much smaller than grams. However, why did it have to change from celsius to K? Is it the same reason?
- Mon Jan 25, 2021 1:24 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Standard Enthalpy of Formation
- Replies: 10
- Views: 467
Standard Enthalpy of Formation
Hello
I'm still confused to what Standard Enthalpy of Formation is
Professor said that by definition, it is standard reaction enthalpy for the one mole of substance from its elements in their most stable form.
How do we know for each compounds what their standard enthalpies are?
I'm still confused to what Standard Enthalpy of Formation is
Professor said that by definition, it is standard reaction enthalpy for the one mole of substance from its elements in their most stable form.
How do we know for each compounds what their standard enthalpies are?
- Sun Jan 24, 2021 7:22 pm
- Forum: Phase Changes & Related Calculations
- Topic: State Property
- Replies: 11
- Views: 542
State Property
How can Heat not be a state property? in what case would that be?
- Sun Jan 24, 2021 7:22 pm
- Forum: Phase Changes & Related Calculations
- Topic: State Changes
- Replies: 4
- Views: 265
State Changes
Do water vapors change phase siilar to photon where enough energy is required in order to release an electron?
And I was wondering if we would have to memorize any particular "minimum" energy for such famous compounds like water molecules.
And I was wondering if we would have to memorize any particular "minimum" energy for such famous compounds like water molecules.
- Sun Jan 24, 2021 7:19 pm
- Forum: Phase Changes & Related Calculations
- Topic: Steam
- Replies: 33
- Views: 1977
Re: Steam
It basically goes like this. when vapor meets our skin, which is around 36 degrees Celsius, the vapor, due to thermodynamic equilibrium, cools down to a liquid state with temperature of 36 degrees celsius. In order for this to happen, the vapor first needs to condense to a liquid. If we see the char...
- Sun Jan 24, 2021 6:46 pm
- Forum: Phase Changes & Related Calculations
- Topic: Enthalpy of Reaction
- Replies: 3
- Views: 106
Enthalpy of Reaction
Professor mentioned that the way we have constant temperature for a reaction is that we just measure the heat that was given off during the reaction and wait for the system to come back to the equilibrium, to the initial temperature. How do we know when to measure the temperature given off? do we me...
- Sun Jan 24, 2021 5:39 pm
- Forum: Phase Changes & Related Calculations
- Topic: Carbohydrate Converting into CO2 and H2O
- Replies: 2
- Views: 144
Carbohydrate Converting into CO2 and H2O
Hello,
professor mentioned about carbohydrate converting into co2 and h2o when it gets broken down as energy.
Is that the cause of sweating? The increase of H2o gets released outside of our body to cool down the body as energy gets released?
professor mentioned about carbohydrate converting into co2 and h2o when it gets broken down as energy.
Is that the cause of sweating? The increase of H2o gets released outside of our body to cool down the body as energy gets released?
- Sun Jan 17, 2021 7:51 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: X less than 5 percent
- Replies: 11
- Views: 930
Re: X less than 5 percent
you guys are saying I can approximate, but I'm not sure what you guys mean when yall say i can approximate.
Does that mean x = approximately 0?
Does that mean x = approximately 0?
- Sun Jan 17, 2021 7:50 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: X less than 5 percent
- Replies: 11
- Views: 930
Re: X less than 5 percent
does that mean if the percent ionization is less than 5 percent we approximate x as 0?
- Sun Jan 17, 2021 7:34 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: K < 10^-4
- Replies: 2
- Views: 164
K < 10^-4
why do we have to check whether K is less than 10^-4 in order to approximate? what does that mean?
and if that condition is not met, what happens?
and if that condition is not met, what happens?
- Sun Jan 17, 2021 12:34 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: X less than 5 percent
- Replies: 11
- Views: 930
X less than 5 percent
I have a question from the recent lecture. Professor said that if X is less than 5 percent for the weak acid percent ionization, the approximation is valid. However, couldnt different weak acids have different percent ionization, leading to an x value, which is the H3O+ composed from ionization, big...
- Wed Jan 13, 2021 5:58 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: pKw
- Replies: 7
- Views: 368
pKw
Why is Kw always considered 14?
Weren't there questions where Kw equals to 2.1x10^-14 or other values?
why would Kw always be considered 1 x 10^-14 in any aqueous solutions?
Weren't there questions where Kw equals to 2.1x10^-14 or other values?
why would Kw always be considered 1 x 10^-14 in any aqueous solutions?
- Wed Jan 13, 2021 5:56 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: 5J.5
- Replies: 5
- Views: 257
Re: 5J.5
H2 should go onto the right side of the equation. this should be a typo I think there were already a lot of students who asked about this, finding the typo. Also, maybe the reason why neither the products or reactants are favored is because as pressure increases that means more collision occurs, lea...
- Wed Jan 13, 2021 1:59 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Left vs. Right
- Replies: 29
- Views: 1068
Re: Left vs. Right
Favoring left means that the equation is producing reactants more efficiently than products.
Towards the left means the same thing!
Towards the left means the same thing!
- Tue Jan 12, 2021 8:29 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Neglecting Water
- Replies: 20
- Views: 1094
Neglecting Water
Professor said in the lecture that we neglect the water concentration in the Kw equation because it is excess. What does that mean?
why do we have to neglect it, leading to just the calculation of [H3O+][OH-]?
why do we have to neglect it, leading to just the calculation of [H3O+][OH-]?
- Tue Jan 12, 2021 8:28 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Super Acids and Super Bases
- Replies: 6
- Views: 302
Super Acids and Super Bases
What are super acids and super bases?
Is that when the Kw does not equal to 10^-14? when would those cases be?
Is that when the Kw does not equal to 10^-14? when would those cases be?
- Fri Jan 08, 2021 1:12 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Change in Pressure
- Replies: 4
- Views: 115
Change in Pressure
When discussing about the change in pressure Professor said that when Volume Decreases and more moles of gas are on the left, then reaction will favor products if volume decreases and more moles of gas are on the right, then reaction will favor reactants How can there be more moles on the left and o...
- Fri Jan 08, 2021 12:18 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Lecture 3 PCl5 Example Question
- Replies: 2
- Views: 101
Lecture 3 PCl5 Example Question
Hello, For the first example and the last example of lecture 2 that Professor Lavelle went over, which was 1.50 mol PCl5 is placed in a 500ml reaction vessel and decomposes at 250 C to form PCl3 and Cl2, Kc = 1.80, All 3 compounds are gases at 250 C why is professor using concentration instead of pa...
- Wed Jan 06, 2021 2:34 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: True or False?
- Replies: 4
- Views: 319
True or False?
Why is this true?
"If one starts with higher concentration of reactants, the equilibrium concentrations of the product will be larger"
"If one starts with higher concentration of reactants, the equilibrium concentrations of the product will be larger"
- Wed Jan 06, 2021 12:58 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: K=1
- Replies: 6
- Views: 179
K=1
Why is K=1 rare?
- Wed Jan 06, 2021 12:10 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Partial Pressure
- Replies: 4
- Views: 163
Partial Pressure
What is the meaning of partial pressure?
- Mon Jan 04, 2021 4:52 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Temperature Difference
- Replies: 4
- Views: 301
Temperature Difference
Hello,
I realized that for examples like N2 + 3 H2 <-> 2NH3 the reaction needs to be at a higher temperature since the gas molecules have to collide in order to create a molecule.
What happens if the reaction was in a lower temperature?
Will the reaction even take place?
I realized that for examples like N2 + 3 H2 <-> 2NH3 the reaction needs to be at a higher temperature since the gas molecules have to collide in order to create a molecule.
What happens if the reaction was in a lower temperature?
Will the reaction even take place?
- Mon Jan 04, 2021 4:46 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Lecture Clarification
- Replies: 2
- Views: 183
Lecture Clarification
Hello
When professor was talking about how the change in concentration of solvent was immeasurable, can someone clarify what he was talking about?
It was towards the end of the lecture where he talked about the molar concentration of a pure substance does not change in reaction.
When professor was talking about how the change in concentration of solvent was immeasurable, can someone clarify what he was talking about?
It was towards the end of the lecture where he talked about the molar concentration of a pure substance does not change in reaction.
- Fri Dec 11, 2020 12:35 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Wednesday Professor Lavelle Review Slides
- Replies: 1
- Views: 138
Wednesday Professor Lavelle Review Slides
Hello,
I was wondering where I could find Professor's Review Slides shown on Wednesday
I was wondering where I could find Professor's Review Slides shown on Wednesday
- Wed Dec 09, 2020 9:27 pm
- Forum: Resonance Structures
- Topic: Stabilization
- Replies: 1
- Views: 163
Stabilization
How does resonance stabilize an anion?
- Wed Dec 09, 2020 9:25 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Delocalized
- Replies: 6
- Views: 1111
Re: Delocalized
Also, what does it mean to withdraw electron density??
- Wed Dec 09, 2020 9:19 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Delocalized
- Replies: 6
- Views: 1111
Delocalized
Hello, Professor said as he was explaining relative acidity that "Acid more readily loses H+ if resulting anion is stabilized by resonance and/or electron withdrawing atoms which delocalize and stabilize the negative charge." He also stated that whenever charges delocalize it is most stabl...
- Wed Dec 09, 2020 7:54 pm
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: Favorable forces
- Replies: 1
- Views: 162
Favorable forces
Hello,
what forces are considered favorable??
And how do you compare whether ones more favorable?
Ex.
NH3 has hydrogen bond, london dispersion, and dipole dipole.
which force is the most favorable?
what forces are considered favorable??
And how do you compare whether ones more favorable?
Ex.
NH3 has hydrogen bond, london dispersion, and dipole dipole.
which force is the most favorable?
- Wed Dec 09, 2020 7:52 pm
- Forum: Properties of Electrons
- Topic: How can an electron be excited?
- Replies: 7
- Views: 485
How can an electron be excited?
I realize from the photoelectric effect that the electrons are emitted when each photons have enough energy to meet the threshhold.
And I thought professor said that if each photon energy does not meet the quota, then they just go through the atom.
Then, how do electrons get excited?
And I thought professor said that if each photon energy does not meet the quota, then they just go through the atom.
Then, how do electrons get excited?
- Wed Dec 09, 2020 7:50 pm
- Forum: Lewis Structures
- Topic: H2SeO4
- Replies: 2
- Views: 523
H2SeO4
hello,
I was wondering how you know when drawing the lewis structure that the 2 Hydrogens go to the oxygen rather than making 6 single bonds, 4 oxygen and 2 hydrogens attached to Se.
I was wondering how you know when drawing the lewis structure that the 2 Hydrogens go to the oxygen rather than making 6 single bonds, 4 oxygen and 2 hydrogens attached to Se.
- Tue Dec 08, 2020 4:15 pm
- Forum: Properties & Structures of Inorganic & Organic Bases
- Topic: Oxides
- Replies: 3
- Views: 293
Oxides
Hello,
Can someone clarify why Oxides are strong bases?
Can someone clarify why Oxides are strong bases?
- Tue Dec 08, 2020 4:11 pm
- Forum: Properties & Structures of Inorganic & Organic Bases
- Topic: NH3 and Methylamine
- Replies: 1
- Views: 313
NH3 and Methylamine
Hello,
I was watching lecture 26 and saw that Methylamine, which derives from NH3, ammonia, is a weak acid.
I was wondering what property of NH3 makes it a weak base.
I was watching lecture 26 and saw that Methylamine, which derives from NH3, ammonia, is a weak acid.
I was wondering what property of NH3 makes it a weak base.
- Tue Dec 08, 2020 2:54 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Polydentate
- Replies: 1
- Views: 79
Polydentate
What can and cannot be polydentate?
- Mon Nov 30, 2020 11:12 am
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: EDTA+
- Replies: 2
- Views: 234
EDTA+
Hello, when professor talked about Ethylene - Diamine - Tetra - Acetate, the Ethylene, NH2-CH2-CH2-NH2, can rotate to make a ring, said by professor in his lecture. Is this related to the ideal bonding geometry of ligand that can form more than one bond to the same TM cation (Chelate)? Where ligands...
- Mon Nov 30, 2020 11:10 am
- Forum: Hybridization
- Topic: Pi Bonds break
- Replies: 8
- Views: 445
Pi Bonds break
Hello,
Professor mentioned that Pi bonds can break when the central atoms rotate.
Are there any cases when they do rotate and what is the cause of their rotation?
Professor mentioned that Pi bonds can break when the central atoms rotate.
Are there any cases when they do rotate and what is the cause of their rotation?
- Mon Nov 30, 2020 11:09 am
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: Transition Metal Complexes
- Replies: 5
- Views: 286
Transition Metal Complexes
Hello, I was wondering how many bonds can T.M. complexes make in a solution.
Some say they are tetrahedral and some say they are octahedral. How do we know how many bonds can each transition metals make?
Some say they are tetrahedral and some say they are octahedral. How do we know how many bonds can each transition metals make?
- Mon Nov 30, 2020 11:07 am
- Forum: Hybridization
- Topic: Two Pi Bonds?
- Replies: 4
- Views: 166
Two Pi Bonds?
Hello,
I was confused to whether there are two pi bonds forming in a single pi bond because there are areas of bonding up and down if you look at the 3D graph.
I was confused to whether there are two pi bonds forming in a single pi bond because there are areas of bonding up and down if you look at the 3D graph.
- Mon Nov 30, 2020 11:06 am
- Forum: Hybridization
- Topic: Energy Gap between sp3 and p
- Replies: 2
- Views: 171
Energy Gap between sp3 and p
Hello As professor was giving an example using Ethene, professor said "energy gap is small between hybridized and normal p orbital, so you do not spin pair.: What does that mean? I understand that since sp2 is a mix between s and p orbitals, it is going to be closer to the p orbital. But I do n...