Search found 53 matches
- Sun Mar 11, 2018 10:23 pm
- Forum: Balancing Redox Reactions
- Topic: redox
- Replies: 6
- Views: 878
Re: redox
The oxidizing agent gains electrons and reducing agent losses electrons. A easy way to remember this is that Oxygen usually (not always!) acts as the oxidizing agent in redox reactions and it gains electrons during redox reactions.
- Sun Mar 11, 2018 10:18 pm
- Forum: Balancing Redox Reactions
- Topic: Ranking elements
- Replies: 8
- Views: 1147
Re: Ranking elements
You could refer to activity series of metals. For example, https://www.thoughtco.com/activity-seri ... als-603960.
- Sun Mar 11, 2018 10:12 pm
- Forum: Balancing Redox Reactions
- Topic: 14.5 Part a
- Replies: 4
- Views: 585
Re: 14.5 Part a
No, you don't have to. It may be canceled out or doesn't never needed to balance the equation.
- Sun Mar 11, 2018 10:09 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Test 2 Question 2
- Replies: 4
- Views: 599
Re: Test 2 Question 2
Ecell=-0.44 V-(-0.74 V)=0.30V, and then use the equation mentioned above to calculate K.
- Sun Mar 11, 2018 10:06 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Electrochem Review session problem 14.47
- Replies: 2
- Views: 390
Re: Electrochem Review session problem 14.47
I think it's out of the sig figs problem.
- Sun Mar 04, 2018 11:19 pm
- Forum: General Rate Laws
- Topic: Negative Order 15.3
- Replies: 2
- Views: 376
Re: Negative Order 15.3
Negative order means that increasing the concentration slows down the reaction. I believe it happens when products' concentrations affect the reaction rate.
- Sun Mar 04, 2018 11:14 pm
- Forum: First Order Reactions
- Topic: k
- Replies: 16
- Views: 1568
Re: k
There is no need to do so unless other calculation is needed.
- Sun Mar 04, 2018 11:09 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Friday Lecture
- Replies: 5
- Views: 606
Re: Friday Lecture
It's because CO2 is the other reactant in this reaction. Since it does not occur in the reaction of NO2, there must be a subsequent reaction that involves CO2.
- Sun Mar 04, 2018 11:04 pm
- Forum: General Rate Laws
- Topic: Rate laws
- Replies: 4
- Views: 545
Re: Rate laws
I think graphs will be given or the correlation will be explained.
- Sun Mar 04, 2018 11:03 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: k units [ENDORSED]
- Replies: 7
- Views: 1213
Re: k units [ENDORSED]
It's because the unit of the reaction rate is always the same.
- Sun Mar 04, 2018 11:01 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Kinetics Test
- Replies: 3
- Views: 474
Re: Kinetics Test
Same question.
- Sun Feb 18, 2018 11:45 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Cell potential calculation
- Replies: 4
- Views: 574
Re: Cell potential calculation
I guess you should always reverse the less reactive one.
- Sun Feb 18, 2018 11:37 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Salt Bridge
- Replies: 2
- Views: 488
Re: Salt Bridge
Agar with solutions of high concentration.
- Sun Feb 18, 2018 11:34 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: redox
- Replies: 7
- Views: 1192
Re: redox
Agree. The substance loss electrons is oxidized and that gain electrons is reduced.
- Sun Feb 18, 2018 11:32 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Electromotive force and Why is E a Maximum
- Replies: 2
- Views: 373
Re: Electromotive force and Why is E a Maximum
As for other chemical experiments, there is always less an efficiency for actual operations than that by calculations.
- Mon Feb 05, 2018 12:42 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Heat transfer
- Replies: 7
- Views: 841
Re: Heat transfer
Same question!
- Mon Feb 05, 2018 12:40 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: q=-w [ENDORSED]
- Replies: 5
- Views: 869
Re: q=-w [ENDORSED]
Christina Bedrosian 1B wrote:This formula is true for instances of isothermal expansions since having deltaT=0 (no change in temp), then deltaU (internal energy) would be 0 and since deltaU=q+w, then q would equal -w
Agree.
- Mon Feb 05, 2018 12:39 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Test Number 1
- Replies: 9
- Views: 1036
Re: Test Number 1
Bansi Amin 1D wrote:So the heat was transferred to make up for the change in energy in the system?
Heat is transferred because of a temperature different. The work is done by the system through giving off heat and the work is done to the system by increasing its heat.
- Mon Feb 05, 2018 12:37 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Test question [ENDORSED]
- Replies: 16
- Views: 1704
Re: Test question [ENDORSED]
Kyung_Jin_Kim_1H wrote:Conservation of energy in the universe.
(I didn't even think of elaborating...)
Same.
- Mon Feb 05, 2018 12:35 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Delta S vs Delta U [ENDORSED]
- Replies: 5
- Views: 2889
Re: Delta S vs Delta U [ENDORSED]
Abigail Yap 2K wrote:Hi,
Delta S is the change in entropy and delta U is the change in internal energy.
Agree.
- Mon Feb 05, 2018 12:27 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Delta G equal Zero [ENDORSED]
- Replies: 4
- Views: 682
Re: Delta G equal Zero [ENDORSED]
Lily Guo 1D wrote:Not necessarily, but delta G = 0 does mean that the reaction is at equilibrium.
Agree.
- Mon Feb 05, 2018 12:25 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gibbs Free Energy
- Replies: 7
- Views: 788
Re: Gibbs Free Energy
Wenjie Dong 2E wrote:"It measures the maximum or reversible work that may be performed by a thermodynamic system at a constant temperature and pressure. (isothermal, isobaric)"
from Wikipedia
- Mon Feb 05, 2018 12:25 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gibbs Free Energy
- Replies: 7
- Views: 788
Re: Gibbs Free Energy
"It measures the maximum or reversible work that may be performed by a thermodynamic system at a constant temperature and pressure. (isothermal, isobaric)"
- Mon Feb 05, 2018 12:15 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Net Increases in Amount of Gas
- Replies: 3
- Views: 464
Re: Net Increases in Amount of Gas
Not sure. But an increase in the amount of gas increases the moles of molecules and thus increases the possibilities of microstate arrangements, which leads to higher entropy.
- Mon Feb 05, 2018 12:11 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: negative entropy [ENDORSED]
- Replies: 10
- Views: 5668
Re: negative entropy [ENDORSED]
There is no such thing as negative entropy. The negative delta entropy means a decrease in disorder.
- Mon Feb 05, 2018 12:07 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: determining number of microstates
- Replies: 3
- Views: 436
Re: determining number of microstates
Ryan Sydney Beyer 2B wrote:I'm not too certain that we will have to calculate the number of microstates for a specific molecule, but rather if the molecule can be in place A or place B. I think it'll more like probability in place A vs. place B and that is the number of microstates.
Agree.
- Mon Feb 05, 2018 12:04 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Delta U (Concept Clarification)
- Replies: 6
- Views: 669
Re: Delta U (Concept Clarification)
There is no change in internal energy in the system when delta U=0.
- Sat Jan 20, 2018 1:17 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Heat Capacity Properties
- Replies: 3
- Views: 362
Re: Heat Capacity Properties
Heat capacity is an extensive property because for one substance it changes when the amount of substance changes. Specific Heat Capacity and Molar Heat Capacity are intensive property because they are identical for one substance, independent on the amount.
- Sat Jan 20, 2018 1:13 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: ∆U = U final-U initial
- Replies: 1
- Views: 508
Re: ∆U = U final-U initial
Just always subtract the initial U from the final one no matter which one is larger.
- Sat Jan 20, 2018 1:09 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: change in internal energy
- Replies: 4
- Views: 304
Re: change in internal energy
When there is no word done to the system, the change of internal energy is the same as the heat change. When there is no heat exchange, the change of internal energy is equal to the work done.
- Thu Jan 11, 2018 3:05 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Hess's Law example from lecture
- Replies: 3
- Views: 437
Re: Hess's Law example from lecture
The equations should be:
N2 + O2 --> 2NO
2NO + O2 --> 2NO2
-----------------------
N2 + 2O2 --> 2NO2
N2 + O2 --> 2NO
2NO + O2 --> 2NO2
-----------------------
N2 + 2O2 --> 2NO2
- Thu Jan 11, 2018 3:03 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Hess's Law vs. Using Bond Enthalpies
- Replies: 3
- Views: 1561
Re: Hess's Law vs. Using Bond Enthalpies
Hess's Law is more macroscopic while bond enthalpies method is more microscopic. Hess's Law focuses merely on the heat changes during reactions and presents the conclusion that "the total enthalpy change for the reaction is the sum of all changes." Bond enthalpies method concentrates on th...
- Wed Jan 10, 2018 9:31 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Most Stable Form for an Element
- Replies: 4
- Views: 629
Re: Most Stable Form for an Element
It means the form when the element has the least energy.
- Thu Dec 07, 2017 8:09 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Change in concentration
- Replies: 2
- Views: 211
Re: Change in concentration
If not given, it's usually resulted from the change in volume.
- Thu Dec 07, 2017 8:01 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Dentates
- Replies: 4
- Views: 565
Re: Dentates
Same question!
- Thu Dec 07, 2017 7:59 pm
- Forum: Conjugate Acids & Bases
- Topic: HW 12.45
- Replies: 4
- Views: 1191
Re: HW 12.45
Christina Cen 3E wrote:pkb = 14 - pka
The lower the pkb is, the stronger the base, so the higher the pka = smaller pkb = stronger base
I agree with your explanation!
- Fri Nov 24, 2017 10:01 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bond Angles Question
- Replies: 3
- Views: 448
Re: Bond Angles Question
Just remember lone pair has stronger repulsive force and results in relatively larger bond angles around it.
- Fri Nov 24, 2017 9:58 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Oxalate Ligand Bonding
- Replies: 1
- Views: 260
Re: Oxalate Ligand Bonding
I happened to see a picture that indicates it's two oxygens attached to one carbon but I'm not sure.
- Sun Nov 19, 2017 11:42 am
- Forum: Hybridization
- Topic: Electron density question
- Replies: 4
- Views: 736
Re: Electron density question
It will. For example, NH3 has a lone pair in N and its hybridization is sp3.
- Sun Nov 19, 2017 11:39 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Lone Pair Repulsion
- Replies: 2
- Views: 359
Re: Lone Pair Repulsion
Electrons are less stable in long pairs and thus have higher energy. Higher energy causes higher repulsion.
- Sun Nov 19, 2017 11:38 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Cis- & Trans-
- Replies: 3
- Views: 266
Re: Cis- & Trans-
Cis- is for atoms that are next to each other, while trans- is for those are opposite to each other.
For example, PtCl2(NH3)s, we use "cis-" for the molecule with the structure of Cl next to each other and "trans-" for Cl opposite to each other.
For example, PtCl2(NH3)s, we use "cis-" for the molecule with the structure of Cl next to each other and "trans-" for Cl opposite to each other.
- Sun Nov 19, 2017 11:31 am
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Maximum number of ligands
- Replies: 3
- Views: 903
Re: Maximum number of ligands
I guess it is, but we might not go that further into that.
- Sun Nov 19, 2017 11:29 am
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: General Understanding of Coordination Sphere
- Replies: 2
- Views: 502
Re: General Understanding of Coordination Sphere
I agree with Ryan.
- Wed Oct 25, 2017 5:53 pm
- Forum: Lewis Structures
- Topic: Double or single bonds
- Replies: 4
- Views: 514
Re: Double or single bonds
Subtract total valence electrons from electrons needed to form octets structure in all atoms. Half that number we get, and then use the answer to determine whether we need single, double or triple bonds.
- Wed Oct 25, 2017 5:47 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Difference between subshell and orbital [ENDORSED]
- Replies: 9
- Views: 2626
Re: Difference between subshell and orbital [ENDORSED]
We can have many orbitals (s, p, d, f) under one subshell.
- Sun Oct 22, 2017 9:26 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: P orbitals
- Replies: 4
- Views: 1852
Re: P orbitals
StephanieDoan3B wrote:All three orbitals have the same energy, and the electron will fill any of them first. We designate that px is filled first, then py, and pz because of convention.
I agree. So there will be a second electron on any of the orbit only if px, py, and pz are all filled with one already.
- Sun Oct 22, 2017 9:22 pm
- Forum: Photoelectric Effect
- Topic: Work Function [ENDORSED]
- Replies: 5
- Views: 668
Re: Work Function [ENDORSED]
I agree with the above two answers. Both yes.
- Thu Oct 19, 2017 10:18 pm
- Forum: Properties of Light
- Topic: Converting Units [ENDORSED]
- Replies: 11
- Views: 1391
Re: Converting Units [ENDORSED]
It is better to convert to the most used units.
- Thu Oct 19, 2017 10:17 pm
- Forum: Properties of Light
- Topic: Lyman and Balmer series.
- Replies: 4
- Views: 463
Re: Lyman and Balmer series.
I guess we don't need to.
- Thu Oct 19, 2017 10:15 pm
- Forum: Photoelectric Effect
- Topic: Ionization in energy levels
- Replies: 4
- Views: 594
Re: Ionization in energy levels
Julie Steklof 3C wrote:The energy required to ionize an electron is the same as the energy required to remove an electron.
I agree.
- Thu Oct 12, 2017 9:49 pm
- Forum: Properties of Light
- Topic: Electric Field and Magnetic Field of Light
- Replies: 4
- Views: 363
Re: Electric Field and Magnetic Field of Light
Mia Navarro 1J wrote:the shift of an electron's flight with respect to a photon's energy being shot at it.
What is this experiment? Can u explain more of it?
- Thu Oct 12, 2017 8:28 pm
- Forum: Properties of Light
- Topic: Electric Field and Magnetic Field of Light
- Replies: 4
- Views: 363
Electric Field and Magnetic Field of Light
Can anybody explain Electric Field and Magnetic Field of Light for me?
- Tue Oct 03, 2017 9:29 pm
- Forum: Student Social/Study Group
- Topic: Fundamental M.25
- Replies: 3
- Views: 1535
Re: Fundamental M.25
1. Use the molecule formula C10H7OH to calculate mass percentage composition of C, H, O 2. Get the simplest ratio of mass of C, H, O in C10H7OH (C:H:O=15:1:2) 3. Get the percentage of O in C10H7OH in the sample using the ratio above (H : O = 5.20% : ? = 1:2 --> ? = 10.40%) 4. Add up the percentage o...