Search found 30 matches
- Fri Mar 15, 2019 8:54 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Ecell
- Replies: 4
- Views: 545
Re: Ecell
There are two ways to find Ecell. One way is to use the equation Ecell=E(Cathode)-E(Anode). Remember that cathode is usually on the right whereas anode is on the left. You use the reduction E values of the half reactions and plug into Ecell equation Another way is to not use the equation. Instead yo...
- Fri Mar 15, 2019 8:49 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Pre-equilibrium approach
- Replies: 2
- Views: 358
Re: Pre-equilibrium approach
replacing K helps with understanding the rate of the reactions. When writing the rate law, you use rate constants and not K as K just means the reaction is at equilibrium, Having k/k' is more representative of rates in relation to concentration
- Fri Mar 15, 2019 8:46 pm
- Forum: Student Social/Study Group
- Topic: Studying for the Final
- Replies: 25
- Views: 2840
Re: Studying for the Final
Doing a lot of practice problems helps a lot. Karen posts worksheets on chemistry community that are helpful
- Sat Mar 09, 2019 6:43 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Gases and Liquids in Cell Diagrams
- Replies: 3
- Views: 557
Re: Gases and Liquids in Cell Diagrams
Water should only be included in the cell diagram if H20 is being reduced or oxidized in the reaction. If H20 is reduced to H2(g) then you would include H20 in the cell diagram. Otherwise if nothing is happening to H20 then it does not need to be included
- Sat Mar 09, 2019 6:41 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Test #2 Question 5 (ph acidic or basic)
- Replies: 1
- Views: 272
Re: Test #2 Question 5 (ph acidic or basic)
For this question you use the equation of ln(K2/K1)=delta H/R (1/T2 - 1/T1) . K1 is 10^-14 and T1 is 25 degrees celsius. You plug in delta H=58 kj/mol and plug in T2=10 degrees celsius or 283K. You plug in all values to find K2. K2 is equal to the concentration of H30+ and OH-. You know that the con...
- Sat Mar 09, 2019 6:34 pm
- Forum: General Science Questions
- Topic: Discussion Section Test
- Replies: 3
- Views: 632
Discussion Section Test
For the photosynthesis of glucose in the chloroplasts of an old growth redwood tree, why is deltaG>0 the wrong answer. Isn't photosynthesis endergonic?
- Sun Mar 03, 2019 12:42 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Final Topics
- Replies: 6
- Views: 684
Re: Final Topics
The final is cumulative. You probably only need to remember the basic things from 14A that are also applied in 14B like stoichiometry, lewis structures, etc
- Tue Feb 26, 2019 6:47 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Calculating standard potential of cell
- Replies: 1
- Views: 241
Calculating standard potential of cell
Do you switch the sign of standard E, (cell potential), when you reverse a reaction or does the sign remain the same?
- Tue Feb 26, 2019 3:36 pm
- Forum: Balancing Redox Reactions
- Topic: Cell Diagram
- Replies: 4
- Views: 473
Re: Cell Diagram
An inert electrode is used when half rxns have no conducting solid
- Tue Feb 26, 2019 3:33 pm
- Forum: Balancing Redox Reactions
- Topic: Knowing oxidation states
- Replies: 2
- Views: 221
Re: Knowing oxidation states
You have to look at what Manganese is bonded to.KMnO4 is the compound and based on the periodic table we know the oxidation state of K is 1+ and the oxidation state of O is 2-. You can figure out an unknown oxidation number by knowing the oxidation number of the element it is bonded to
- Tue Feb 26, 2019 3:31 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Potential Diff of Electrodes
- Replies: 1
- Views: 213
Potential Diff of Electrodes
Why is it that when potential diff of electrodes is positive, the electron flow is form left to right?
- Tue Feb 26, 2019 3:22 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Standard Reduction Potential
- Replies: 2
- Views: 273
Re: Standard Reduction Potential
For half reactions you might have to change the sign if you need to reverse the reaction depending on whether the reaction should be oxidized or reduced
- Thu Feb 14, 2019 3:43 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Calorimeter - Type of System
- Replies: 5
- Views: 1025
Re: Calorimeter - Type of System
Calorimeters are isolated systems. that is why you can calculate the final temperature of water inside a calorimeter based on the mass of calorimeter and water and their heat capacities. The heat lost by the calorimeter is absorbed by water since the water is an isolated system and no heat is lost t...
- Thu Feb 14, 2019 3:40 pm
- Forum: Administrative Questions and Class Announcements
- Topic: DOWNLOAD SESSION WORKSHEETS HERE - Sun 7-9PM (Karen)
- Replies: 179
- Views: 24198
Re: DOWNLOAD SESSION WORKSHEETS HERE - Sun 7-9PM (Karen)
Why is for delta H combustion, the equation is the the delta h combustion of reactants minus delta h combustion products whereas for delta h of formation it is the opposite?
- Thu Feb 14, 2019 3:37 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Cp,m
- Replies: 5
- Views: 814
Re: Cp,m
You use Cp for conditions of constant pressure in isothermal reactions. You use Cv for conditions of constant volume in isothermal reactions.
- Sat Feb 09, 2019 3:15 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Midterm topics
- Replies: 3
- Views: 446
Re: Midterm topics
Yes, for the 7th edition Gibbs Free Energy starts at 4J so you need to know the material up to 4I for thermodynamics
- Sat Feb 09, 2019 2:58 pm
- Forum: Phase Changes & Related Calculations
- Topic: 4A3 7th Edition
- Replies: 3
- Views: 347
Re: 4A3 7th Edition
q would equal zero so there is no heat input or output. You can assume the system is adiabatic even though it doesn't explicitly state that
- Sat Feb 09, 2019 2:55 pm
- Forum: Calculating Work of Expansion
- Topic: Expansion work
- Replies: 1
- Views: 242
Re: Expansion work
You would use the equation w=-PdeltaV. To get the final and intial volume you would multiply the grams of water by the density and convert cm3 to L. 1cm3 is 10^-3 L. Then you would use 1070 as the pressure value and plug in deltaV and convert L*atm to Joules to get the final work done.
- Sat Feb 02, 2019 5:27 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Midterm Review
- Replies: 14
- Views: 1267
Midterm Review
Will we be having a midterm review session before the first midterm?
- Tue Jan 29, 2019 5:59 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Internal Energy and Titration
- Replies: 2
- Views: 450
Internal Energy and Titration
Why can we assume that there is no volume change when an acid and base are titrated together for internal energy calculations?
- Tue Jan 29, 2019 5:55 pm
- Forum: Calculating Work of Expansion
- Topic: HW problem 4A.3 from 7th edition
- Replies: 1
- Views: 193
HW problem 4A.3 from 7th edition
I am confused as to why delta V=pi*r^2*d according to the solution manual. Where did the book get that equation from and do we need to know that equation?
- Sat Jan 26, 2019 1:23 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Standard enthalpy of formation
- Replies: 2
- Views: 234
Standard enthalpy of formation
Is there a difference between the standard enthalpy of formation and the standard reaction enthalpy. What do each refer to?
- Sat Jan 26, 2019 1:20 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Changing sign of enthalpy
- Replies: 3
- Views: 420
Re: Changing sign of enthalpy
It depends on whether the exothermic or endothermic reaction is favored. If the forward reaction is endothermic and is favored the delta H would be positive. If the reverse reaction is favored, the delta H becomes negative as the reverse reaction is exothermic.
- Sat Jan 26, 2019 1:17 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Bond enthalpies to calculate change in enthalpy
- Replies: 3
- Views: 543
Re: Bond enthalpies to calculate change in enthalpy
You would determine the change in phases and find the bond enthalpy. You subtract the bond enthalpy of the reactants from the bond enthalpy of the products
- Sun Jan 20, 2019 1:14 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Peer Learning Sessions [ENDORSED]
- Replies: 10
- Views: 7884
Re: Peer Learning Sessions [ENDORSED]
Do we get worksheets to work on at step up sessions or peer learning sessions?
- Sun Jan 20, 2019 1:11 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Discussion Section Test
- Replies: 4
- Views: 489
Discussion Section Test
I was wondering if the test is multiple choice or short answer?
- Sun Jan 20, 2019 1:06 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: HW Problem #12.79 (6th edition)
- Replies: 1
- Views: 101
Re: HW Problem #12.79 (6th edition)
H2SO4 is a strong acid so it dissociates completely. That is why both the hydrogen atoms are deprotonated and you get SO4 as a product
- Wed Jan 09, 2019 3:56 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Audio Visual Topics
- Replies: 1
- Views: 246
Audio Visual Topics
Is there a deadline for when we should complete the audio visual topics. I am confused if we do one audio visual topic a week or how it works?
- Wed Jan 09, 2019 3:49 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Equilibrium Constants Involving Spectator Ions
- Replies: 2
- Views: 135
Re: Equilibrium Constants Involving Spectator Ions
Spectator ions cancel each other out so you do not need to include them in your calculations
- Wed Jan 09, 2019 3:44 pm
- Forum: General Science Questions
- Topic: Lecture Powerpoints
- Replies: 9
- Views: 750
Lecture Powerpoints
Will the lecture powerpoints that are shown in class be posted on the class website?