Search found 34 matches
- Sat Mar 17, 2018 11:51 am
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Concentration cells
- Replies: 2
- Views: 515
Concentration cells
For concentration cells with different concentration, why does the product has to have lesser concentration than the reactant when we write the overall reactions?
- Wed Mar 14, 2018 2:54 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: E cell value
- Replies: 2
- Views: 374
Re: E cell value
Thank you! And if it wasn't a galvanic cell, and the overall E could be negative. how do we know which one to flip?
- Wed Mar 14, 2018 2:34 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: E cell value
- Replies: 2
- Views: 374
E cell value
In the second electrochem problem Lavelle went through today in lecture, why did we flip the E value for the second equation? Do we always flip the equation with a much more negative value?
- Sun Mar 11, 2018 11:25 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Ways to approach reaction mechanism
- Replies: 2
- Views: 375
Ways to approach reaction mechanism
In lecture, Lavelle went through the 3 ways to to calculate reaction mechanism, Steady state, pre equilibrium and the "direct computation: solve for differential equations". What exactly is the "direct computation" approach. I'm kinda confused.
- Sun Mar 11, 2018 11:20 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Intermediates in Rate law
- Replies: 3
- Views: 4171
Intermediates in Rate law
Clarification:
When we write rate law based on order, we only include the intermediates if we're writing the rate law for the specific reaction (say step 1 or step 2) right? If it's the overall reactions, we always have to cancel out the intermediates?
When we write rate law based on order, we only include the intermediates if we're writing the rate law for the specific reaction (say step 1 or step 2) right? If it's the overall reactions, we always have to cancel out the intermediates?
- Sun Mar 11, 2018 11:14 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: K and K'
- Replies: 4
- Views: 608
Re: K and K'
is there a way to numerically calculate k' from k without knowing the K?
- Mon Mar 05, 2018 3:27 pm
- Forum: Second Order Reactions
- Topic: 15.35
- Replies: 2
- Views: 437
15.35
For 15.35 part a, the half life for the second order reaction of a substance A is 50.5s when [A]initial is 0.84M. it then asks us to calculate the time needed for the concentration of A to decrease to one sixteenth of its original value. For this question why can't we just multiply 50.5s by 4 like w...
- Sun Mar 04, 2018 5:19 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: 15.29
- Replies: 1
- Views: 279
15.29
when we express the loss of one reactant corresponding to the coefficient of another reactant (like we did in 15.29) , does it only work for first order reactions?
- Sun Mar 04, 2018 4:36 pm
- Forum: First Order Reactions
- Topic: half life
- Replies: 2
- Views: 405
half life
is half life an extensive or intensive property?
- Wed Feb 28, 2018 4:37 pm
- Forum: Zero Order Reactions
- Topic: Units [ENDORSED]
- Replies: 7
- Views: 1936
Re: Units [ENDORSED]
There's also one using kPA/sec. Does anyone know how kPA relates to the rate of reactions?
- Wed Feb 28, 2018 4:35 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: When do we calculate for k
- Replies: 3
- Views: 490
When do we calculate for k
I've seen problems that uses k either from the value given in the textbook or by calculating it. how do we know when we calculate for it ourselves and when we simply use the table provided in the textbook?
- Wed Feb 28, 2018 4:28 pm
- Forum: Second Order Reactions
- Topic: positive slope in second ordre graph
- Replies: 2
- Views: 1374
positive slope in second ordre graph
Could someone explain why there is a positive linear slope for the second order reaction while the slopes are both negative for zero order and first order? Wouldn't the positive slope mean that the concentration in increasing? I'm alittle confused
- Tue Feb 20, 2018 2:33 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Salt Bridge
- Replies: 1
- Views: 254
Salt Bridge
Could someone help explain what exactly happens in the salt bridge as well as with what it does to the reaction? I'm not clear on how the ions gets transferred across it.
- Tue Feb 20, 2018 2:21 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: 14.91 Electrolyte
- Replies: 2
- Views: 437
Re: 14.91 Electrolyte
i think this is referring to the external wire circuit. From what i know, salt bridges don't exist in Electrolytic cells.
- Tue Feb 20, 2018 2:18 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: electrolysis
- Replies: 1
- Views: 284
electrolysis
How much of Electrolysis are we supposed to know regarding the test this week?
- Mon Feb 12, 2018 5:15 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Anode/ Cathode
- Replies: 6
- Views: 827
Anode/ Cathode
In the anode/cathode diagram we saw, is Anode always on the left side or can it be switched? If so, how would we know which is which?
- Sun Feb 11, 2018 11:02 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Monoatomic Ideal Gases
- Replies: 1
- Views: 249
Monoatomic Ideal Gases
What exactly are monoatomic ideal gases? When finding the Cv of F2, would we use 3/2R or 5/2R?
- Sun Feb 11, 2018 10:53 pm
- Forum: Calculating Work of Expansion
- Topic: different ways to calculate w
- Replies: 4
- Views: 589
different ways to calculate w
when do we use -PdeltaV and when do we use -nRTln(V2/V1) in calculating w? What's the difference between the two?
- Wed Feb 07, 2018 5:42 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: K to Kc equation
- Replies: 2
- Views: 426
K to Kc equation
In the equation that converts K to Kc, what does the "c" represent?
- Wed Feb 07, 2018 2:23 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Predicting signs of entropy [ENDORSED]
- Replies: 1
- Views: 282
Predicting signs of entropy [ENDORSED]
I understand that going from solid to gas from reactant to product would lead to an increase in entropy. I also understand that increase in number of moles lead to an increase in entropy. But what happens when a reaction has an increase in the number of moles but also goes from gas to solid in the p...
- Tue Feb 06, 2018 11:46 am
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: 9.15
- Replies: 4
- Views: 634
9.15
Could someone help with how to solve 9.15? I'm not sure where to start
- Wed Jan 31, 2018 3:16 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Gibbs free energy which method is the most accurate? [ENDORSED]
- Replies: 1
- Views: 676
Gibbs free energy which method is the most accurate? [ENDORSED]
Would the values of deltaG be the same regardless of which method is being used to calculate it or is there one that is less accurate than others?
- Wed Jan 31, 2018 3:04 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Entropy Change factors
- Replies: 6
- Views: 791
Re: Entropy Change factors
Would the value of entropy differ based on bond strength as well? Would there be less entropy in a triple bond than in a single bond?
- Wed Jan 31, 2018 3:00 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Phase change question demonstrated in Lecture
- Replies: 4
- Views: 661
Phase change question demonstrated in Lecture
In the lecture, Dr Lavelle went over the phase change problem from Br(l)--> Br(g). There, he talked about how deltaH + is a endothermic reaction that does not favor forward processes. I understand that deltaH + refers to reactions being spontaneous at high temperature but what did Dr Lavelle mean by...
- Mon Jan 22, 2018 9:43 pm
- Forum: Phase Changes & Related Calculations
- Topic: Heating Capacity from Heating Curve
- Replies: 2
- Views: 332
Re: Heating Capacity from Heating Curve
Because Heating capacity refers to the amount of temperature required to raise a certain substance by 1 degree celcius, lower heat capacity means higher rise in temperature over once heated. So on the heating curve, the temperature rises higher thus making the slope of the curve steeper.
- Mon Jan 22, 2018 4:25 pm
- Forum: Phase Changes & Related Calculations
- Topic: enthalpy of phase change
- Replies: 1
- Views: 199
enthalpy of phase change
In the question Dr Lavelle showed us in lecture, Br2(l) --> 2Br(g), i understand that we have to add the enthalpy of vaporization with the bond enthalpies. But what would the enthalpy of vaporization be? is it the normal n*heat of vaporization or is there another way of it?
- Mon Jan 22, 2018 3:25 pm
- Forum: Phase Changes & Related Calculations
- Topic: Heat and Work relation
- Replies: 6
- Views: 733
Heat and Work relation
Based on the deltaU=q+w equation, if a system is endothermic and q is positive, would the work always be negative? If not, when does it become positive?
- Wed Jan 17, 2018 5:09 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Born Haber
- Replies: 2
- Views: 312
Born Haber
Do we need to know the born haber cycle for the test?
- Wed Jan 17, 2018 4:16 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Energy Change in an Isolated System
- Replies: 4
- Views: 628
Re: Energy Change in an Isolated System
So does that mean deltaU=q+w does not apply to an isolated system?
- Wed Jan 17, 2018 4:07 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Extensive vs. Intensive
- Replies: 3
- Views: 484
Re: Extensive vs. Intensive
Extensive properties depend on the amount of the substance so basically an example would be Heat Capacity (the amount of heat required to change the temp by 1 Degree celcius of a substance. But for intensive properties (which are much more useful), it would be things like specific heat capacity or m...
- Wed Jan 17, 2018 4:01 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Bong Enthalpy accuracy [ENDORSED]
- Replies: 3
- Views: 345
Bong Enthalpy accuracy [ENDORSED]
Why again are bond enthalpies the least accurate? In exams, do we always try to use Hess Law unless told otherwise?
- Thu Jan 11, 2018 1:43 pm
- Forum: Phase Changes & Related Calculations
- Topic: Hess Law [ENDORSED]
- Replies: 5
- Views: 510
Hess Law [ENDORSED]
In Hess Law, if we flip the equation product reactant-wise, do we take the reciprocal of the enthalpy value or multiply it by '-'?
- Wed Jan 10, 2018 5:52 pm
- Forum: Phase Changes & Related Calculations
- Topic: Reaction in a Flask
- Replies: 5
- Views: 2166
Re: Reaction in a Flask
Endothermic reaction in a flask feels cool because endothermic reactions use up energy(heat) from the surrounding. Therefore the surroundings loses heat and cools down.
- Wed Jan 10, 2018 5:25 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Heating Curve: How is the kJ calculated?
- Replies: 2
- Views: 223
Heating Curve: How is the kJ calculated?
In the Heating Curve shown in lecture today, how do we know kJ/mol values of each solid/liquid/gas phases depending on the temperatures? Will it always be given?