Search found 61 matches
- Thu Mar 14, 2019 7:54 pm
- Forum: First Order Reactions
- Topic: Edition 6 15.23
- Replies: 2
- Views: 327
Re: Edition 6 15.23
It is a second order reaction, Im pretty sure that's a typo for that problem as in 15.39 they mention the same equation (2A --> B + C) and call it a second-order reaction
- Tue Mar 12, 2019 7:02 pm
- Forum: Van't Hoff Equation
- Topic: Van't Hoff use
- Replies: 13
- Views: 2145
Re: Van't Hoff use
You would use the Van't Hoff equation when there is a temperature change and you are looking to find an equilibrium constant.
- Tue Mar 12, 2019 7:00 pm
- Forum: First Order Reactions
- Topic: Units of Rate Constant
- Replies: 5
- Views: 661
Re: Units of Rate Constant
I wouldn't always convert the time units to seconds, because often times the units depend on the context of the problem. If the problem operates in hours or minutes, then you should use those units.
- Tue Mar 12, 2019 6:53 pm
- Forum: General Rate Laws
- Topic: Rate Laws
- Replies: 8
- Views: 887
Re: Rate Laws
I think you should have a general understanding of the derivation, but you shouldn't stress yourself out over studying that, as the formulas will be on the formula sheet.
- Tue Mar 12, 2019 6:50 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Log version vs ln Version
- Replies: 7
- Views: 835
Re: Log version vs ln Version
It does not matter which one you use, however I would use the ln one, since that is the one that is included on the equation sheet that we are given on tests and the final
- Tue Mar 12, 2019 6:49 pm
- Forum: First Order Reactions
- Topic: Rate dependency
- Replies: 5
- Views: 561
Re: Rate dependency
We focus a lot on initial reactants, as that tells us about the initial rate.
- Tue Mar 12, 2019 6:47 pm
- Forum: Second Order Reactions
- Topic: amounts of reactant and its affect on rate
- Replies: 6
- Views: 573
Re: amounts of reactant and its affect on rate
Yes, that is precisely what happens.
- Tue Mar 12, 2019 6:46 pm
- Forum: Zero Order Reactions
- Topic: zero order in rate law
- Replies: 7
- Views: 1254
Re: zero order in rate law
In this case, you would not need to include it since any number to the power of zero is one.
- Tue Mar 12, 2019 6:38 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Largest E°cell question test #2
- Replies: 4
- Views: 571
Re: Largest E°cell question test #2
You would choose the largest reducing agent as well as the largest oxidizing agent
- Mon Feb 25, 2019 2:42 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gibbs Free Energy
- Replies: 7
- Views: 927
Re: Gibbs Free Energy
When a reaction is exergonic, energy is released from the system to the surroundings, and when a reaction is endergonic, energy is taken in (absorbed) from the surroundings
- Mon Feb 25, 2019 2:41 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gibbs Free Energy Units
- Replies: 5
- Views: 585
Re: Gibbs Free Energy Units
When the question gives you a chemical reaction or units with moles, I would use kJ/mol
- Mon Feb 25, 2019 2:40 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Free Energy is a state function?
- Replies: 5
- Views: 633
Re: Free Energy is a state function?
Since Gibbs Free Energy is a combination of multiple state functions, the resulting function is also a state function.
- Sat Feb 09, 2019 11:06 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Converting Celsius to Kelvin
- Replies: 7
- Views: 718
Converting Celsius to Kelvin
When we are given a temperature in degrees Celsius and we are required to convert to Kelvin, are we supposed to add 273 or 273.15?
- Sat Feb 09, 2019 11:02 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: formulas given on midterm
- Replies: 4
- Views: 440
Re: formulas given on midterm
It will be the same equation sheet that we've been given for previous tests. It's also on his website under "Constants and Equations"
- Mon Feb 04, 2019 1:57 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Units
- Replies: 7
- Views: 659
Re: Units
It would be J/C*mol
- Mon Feb 04, 2019 1:55 pm
- Forum: Phase Changes & Related Calculations
- Topic: Type of systems
- Replies: 12
- Views: 1364
Re: Type of systems
No, because they are two distinct types of systems. An isolated system does not allow energy or matter transfer, whereas a closed system allows energy transfer.
- Mon Feb 04, 2019 1:52 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Midterm [ENDORSED]
- Replies: 49
- Views: 4936
Re: Midterm [ENDORSED]
I would say definitely doing the homework problems and reading the textbook as well as class notes are the best way to prepare.
- Sun Jan 27, 2019 10:47 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Heat Capacity
- Replies: 8
- Views: 783
Re: Heat Capacity
Heat Capacity is extensive
- Sun Jan 27, 2019 10:44 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: pKa vs. pH
- Replies: 15
- Views: 3020
Re: pKa vs. pH
This is because pKa is a the -log of Ka, the acid dissociation constant, it is a measure of acid strength. pH, on the other hand is a measure of the concentration of H+ ions.
- Sun Jan 27, 2019 10:42 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Advice from a Medical Student [ENDORSED]
- Replies: 297
- Views: 426793
Re: Advice from a Medical Student [ENDORSED]
Thanks for the advice
- Sun Jan 27, 2019 10:40 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Standard Temperature
- Replies: 7
- Views: 666
Re: Standard Temperature
I believe it is 25 degrees celsius, unless the problem says differently
- Sun Jan 27, 2019 10:38 pm
- Forum: Phase Changes & Related Calculations
- Topic: Enthalpy signs
- Replies: 13
- Views: 1724
Re: Enthalpy signs
When Delta H is positive, it's endothermic and when it's negative, it's exothermic
- Tue Jan 22, 2019 6:02 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Salt on Test 1
- Replies: 5
- Views: 397
Re: Salt on Test 1
Yes, salts are going to be on the test, since they were on the lecture, meaning they are fair game for the test.
- Tue Jan 22, 2019 5:45 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: ignoring x
- Replies: 10
- Views: 901
Re: ignoring x
You should ignore it when k is equal to or less than 10^-3
- Tue Jan 22, 2019 5:41 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: What Happens to a Reaction if Inert Gas is Added?
- Replies: 7
- Views: 2296
Re: What Happens to a Reaction if Inert Gas is Added?
The reaction does not change if an inert gas is added
- Sat Jan 12, 2019 5:01 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: defining Q
- Replies: 6
- Views: 594
Re: defining Q
Yes, it will continue until it reaches dynamic equilibrium.
- Sat Jan 12, 2019 4:58 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Example in Class
- Replies: 7
- Views: 458
Re: Example in Class
This is because the system would react in order to favor the production of NH3. Since you're removing NH3, it would allow the reactants to form more product
- Sat Jan 12, 2019 4:53 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Solids and Liquids in Rxn
- Replies: 6
- Views: 613
Re: Solids and Liquids in Rxn
If the reaction was only made up of solids and liquids, then K would be equal to 1.
- Thu Dec 06, 2018 3:24 pm
- Forum: Naming
- Topic: Name to Formula
- Replies: 1
- Views: 289
Name to Formula
When going from the name to formula, if there are multiple ligands, how do we know which order to put them in for the formula?
Re: Spelling
It is spelled ammine.
- Wed Dec 05, 2018 9:20 pm
- Forum: Naming
- Topic: cyanido vs cyano
- Replies: 1
- Views: 193
cyanido vs cyano
When do we use cyanido vs cyano in naming?
For 9C.1 in the book, I thought the name of [Fe(CN)6]4- was hexacyanidoferrate(II), but the answer key has it as hexacyanoferrate(II).
For 9C.1 in the book, I thought the name of [Fe(CN)6]4- was hexacyanidoferrate(II), but the answer key has it as hexacyanoferrate(II).
- Sun Dec 02, 2018 9:42 pm
- Forum: Hybridization
- Topic: Hybridization Notation
- Replies: 10
- Views: 932
Re: Hybridization Notation
both ways of writing it are correct
- Sun Dec 02, 2018 9:38 pm
- Forum: Hybridization
- Topic: Pi bonds in triple bond
- Replies: 17
- Views: 1895
Re: Pi bonds in triple bond
There is one sigma bond and two pi bonds in a triple bond.
- Sun Dec 02, 2018 9:31 pm
- Forum: Hybridization
- Topic: S Hybridization?
- Replies: 5
- Views: 501
Re: S Hybridization?
Yes, however we don't really use s hybridization since we focus on more complex molecules that typically involve p orbitals as well.
- Sun Dec 02, 2018 9:27 pm
- Forum: Hybridization
- Topic: CH2O hybridization
- Replies: 9
- Views: 15358
Re: CH2O hybridization
Since there are 3 hybrid orbitals and 3 regions of electron density, the hybridization is sp2.
- Sun Dec 02, 2018 9:23 pm
- Forum: Hybridization
- Topic: lone pairs
- Replies: 20
- Views: 2139
Re: lone pairs
Yes, Lone pairs do indeed count as an area of electron density, so yes, they count for hybridization.
- Wed Nov 28, 2018 9:01 pm
- Forum: Hybridization
- Topic: Sp3d or dsp3
- Replies: 22
- Views: 2230
Re: Sp3d or dsp3
I don't think it matters which order it is written, but I prefer to do sp3d
- Mon Nov 26, 2018 9:02 pm
- Forum: Dipole Moments
- Topic: TEST 3: Polarity
- Replies: 7
- Views: 636
Re: TEST 3: Polarity
I believe the arrow should always point to the negative, and thats the way Lavelle did it in class, so I would probably do it that way
- Mon Nov 26, 2018 8:56 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Formal Charge
- Replies: 8
- Views: 3535
Re: Formal Charge
The one I find the most helpful is # of valence electrons - (Lone electrons + Bonds)
- Mon Nov 26, 2018 8:53 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Can an octahedral be polar?
- Replies: 4
- Views: 2230
Re: Can an octahedral be polar?
No, an octahedral cannot be polar, because the shape is symmetric
- Mon Nov 19, 2018 11:55 am
- Forum: Ionic & Covalent Bonds
- Topic: delta positive delta negative
- Replies: 15
- Views: 2339
Re: delta positive delta negative
Delta negative is the one that accepts electrons, while Delta positive is the one that gives electrons
- Mon Nov 19, 2018 11:40 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bond Angles in 7E 2E.13.b
- Replies: 4
- Views: 484
Re: Bond Angles in 7E 2E.13.b
Double bonds don't have nearly the same effect on bond angles that lone pairs do. Double bonds and single bonds both are the same electron density thus it doesn't affect the bond angle
- Mon Nov 19, 2018 11:35 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Rotation from Sigma and Pi bonds
- Replies: 2
- Views: 361
Re: Rotation from Sigma and Pi bonds
Sigma bonds have their electron density along the bond axis, while pi bonds have their electron density above and below the bond axis. Therefore, pi bonds cannot rotate the same way as sigma bonds since rotation would break the pi bond interaction.
- Mon Nov 19, 2018 11:33 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bond Angle
- Replies: 8
- Views: 798
Bond Angle
Is there a set degree amount a lone pair causes bond angles to change? I know it lessens the angles, but is there a specific amount?
- Mon Nov 19, 2018 11:25 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Dipole moments
- Replies: 8
- Views: 3348
Re: Dipole moments
As long as each dipole moment is equal in charge and opposite in direction, then they will cancel each other out.
- Mon Nov 05, 2018 3:37 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Why does PCl5 break the Octet Rule?
- Replies: 8
- Views: 7115
Re: Why does PCl5 break the Octet Rule?
This is because Phosphorous is in the 3rd energy level, which means it can access the d-orbitals in order to have an expanded octet and form more than 4 bonds.
- Mon Nov 05, 2018 12:41 am
- Forum: Sigma & Pi Bonds
- Topic: Midterm1
- Replies: 10
- Views: 1161
Re: Midterm1
That information wasn't covered in the sections we are required to know for the midterm, nor have we gone over the material in class, so they will not be on the midterm.
- Mon Nov 05, 2018 12:36 am
- Forum: Formal Charge and Oxidation Numbers
- Topic: Alternative version of formula
- Replies: 7
- Views: 1000
Re: Alternative version of formula
Yes, your formula work, but I prefer to use FC = Valence Electrons - (Lone Electrons + Shared Electrons/2)
- Mon Nov 05, 2018 12:33 am
- Forum: DeBroglie Equation
- Topic: DeBroglie Equation Units
- Replies: 4
- Views: 848
Re: DeBroglie Equation Units
All of the equations use SI units in order for them to all follow the same units. That's why its in meters, because meters is the SI unit for measurement of length.
- Mon Nov 05, 2018 12:32 am
- Forum: Properties of Light
- Topic: Practice Midterm 8b
- Replies: 3
- Views: 577
Re: Practice Midterm 8b
Make sure to use wavelength = h/p in order to find the velocity of the electron. Once you find the velocity, you then plug the values into KE = E - work function in order to solve for E. Once you find E, you use E = hV, in order to solve for frequency.
- Mon Nov 05, 2018 12:13 am
- Forum: Resonance Structures
- Topic: Bond Lengths
- Replies: 7
- Views: 2082
Bond Lengths
When there are double bonds in a structure, for example the Nitrate ion, NO3 2-, and chemists observe the actual N-O bond length, is every bond length the same length, despite the fact that we draw it with one double bond and two single bonds indicating that they are different lengths?
- Sun Nov 04, 2018 6:55 pm
- Forum: Administrative Questions and Class Announcements
- Topic: MIDTERM PRACTICE - Garlic Bread Review Session [ENDORSED]
- Replies: 121
- Views: 20107
Re: MIDTERM PRACTICE - Garlic Bread Review Session [ENDORSED]
For number 11, part b why would delta E be a negative value? If the problem is asking for the change in energy from n = 6 to n = 4, and the formula is
E = -hR(1/n1^2 - 1/n2^2), the energy released from n = 6 to n = 4 equals 7.5689 x 10^-20 J. So, why is the answer negative?
E = -hR(1/n1^2 - 1/n2^2), the energy released from n = 6 to n = 4 equals 7.5689 x 10^-20 J. So, why is the answer negative?
- Sun Oct 28, 2018 9:44 pm
- Forum: Lewis Structures
- Topic: General Q on Lewis Structures
- Replies: 2
- Views: 195
General Q on Lewis Structures
Is there a difference between using a line to represent bonds rather than 2 dots? Is there a chemical difference?
- Sun Oct 28, 2018 9:39 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: px,py,pz???
- Replies: 6
- Views: 2203
Re: px,py,pz???
px, py, and pz are helpful also to remember to follow Hund's Rule where every orbital in a subshell is singly occupied with one electron before any one orbital is doubly occupied. Thus 1px, 1py, 1pz instead of 2px, 1py.
- Sun Oct 28, 2018 9:27 pm
- Forum: Lewis Structures
- Topic: octets
- Replies: 13
- Views: 1121
Re: octets
An electron must have a full octet before It goes to the next energy level. Hydrogen and Helium are satisfied with only two electrons in their outermost valence shell.
- Mon Oct 22, 2018 11:45 am
- Forum: Properties of Electrons
- Topic: Test on Wednesday
- Replies: 3
- Views: 401
Re: Test on Wednesday
The test will only cover material that we went over in class until last Friday's lecture. The lecture on Monday will not be on the upcoming test.
- Mon Oct 22, 2018 11:45 am
- Forum: Properties of Light
- Topic: Test 2 Equations
- Replies: 14
- Views: 1090
Re: Test 2 Equations
I believe we will be given the same first sheet with many equations and constants as we were given during the first test.
- Mon Oct 22, 2018 11:42 am
- Forum: Properties of Light
- Topic: TEST 2
- Replies: 7
- Views: 838
Re: TEST 2
I believe we will be given the same first sheet as we were during the first test where it provides us with many equations and constants.
- Sun Oct 14, 2018 6:57 pm
- Forum: Properties of Electrons
- Topic: Energy Q
- Replies: 4
- Views: 237
Energy Q
What does it mean that energy is quantized?
- Sun Oct 14, 2018 6:53 pm
- Forum: Properties of Electrons
- Topic: Electron Question
- Replies: 6
- Views: 600
Electron Question
Why can an electron only exist on specific energy levels?
- Sun Oct 14, 2018 6:45 pm
- Forum: Properties of Electrons
- Topic: Energy Level Question
- Replies: 4
- Views: 378
Energy Level Question
How does the wavelength of an electron change as it jumps to a new energy level?