Search found 64 matches
- Thu Mar 14, 2019 11:28 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Test 2
- Replies: 6
- Views: 1797
Re: Test 2
For the snowflakes, delta H is negative because the snowflakes lose heat, and delta S is negative because going from a liquid to a solid is less chaotic. Negative delta H minus a negative delta S makes a negative delta G. For the sublimation, delta H is positive because heat is going in, and delta ...
- Thu Mar 14, 2019 11:22 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: pseudo rate law
- Replies: 7
- Views: 1048
Re: pseudo rate law
I was wondering the same thing. Dr.Lavelle mentioned it during class, but I am still confused.
- Thu Mar 14, 2019 11:20 pm
- Forum: First Order Reactions
- Topic: integrated rate laws
- Replies: 3
- Views: 394
Re: integrated rate laws
This really helped! I am glad that this question was asked.
- Thu Mar 14, 2019 11:17 pm
- Forum: Van't Hoff Equation
- Topic: pH and van’t hoff
- Replies: 6
- Views: 1392
Re: pH and van’t hoff
When temperature increases, the Kw increases as well, which causes the neutral [H+] to increase and neutral pH to decrease. On the flip side, when temperature decreases, the Kw and neutral [H+] decrease, so the neutral pH increases. Neutral pH of 7 is only true at 298K. Thank you this is very helpf...
- Thu Mar 14, 2019 11:14 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: catalyst vs intermediate
- Replies: 2
- Views: 311
Re: catalyst vs intermediate
A catalyst is at the very beginning of the reaction and gets used; while intermediates only join in the later time and get used.
- Thu Mar 14, 2019 11:12 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Catalysts in Rate Law
- Replies: 5
- Views: 538
Re: Catalysts in Rate Law
I asked my TA today, he said catalysts can be included in elementary step rate laws, but not the overall?
- Wed Mar 13, 2019 10:23 pm
- Forum: First Order Reactions
- Topic: Integrated Rate Law
- Replies: 2
- Views: 311
Re: Integrated Rate Law
What is the exponential first-rate law?
- Wed Mar 13, 2019 10:21 pm
- Forum: First Order Reactions
- Topic: Time Conversions
- Replies: 9
- Views: 1071
Re: Time Conversions
Yes, just make sure that your units are consistent.
- Wed Mar 13, 2019 10:18 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Catalyst vs. Intermediate
- Replies: 8
- Views: 763
Re: Catalyst vs. Intermediate
A catalyst is involved in the starting of the reaction, while an intermediate joins in later. Both of them are not included in the rate law. Today, my TA said that a catalyst can be included in the rate law. Can someone clarify? Sorry! I made a mistake. Yes it is possible for a catalyst to appear i...
- Wed Mar 13, 2019 10:11 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Determining Catalysts
- Replies: 2
- Views: 306
Re: Determining Catalysts
Yes, if it is not one of the reactants of the first step, it would be an intermediate instead.
- Wed Mar 13, 2019 1:23 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Sig Figs
- Replies: 9
- Views: 1113
Re: Sig Figs
I think they are worth one point per question based on the midterm, so I think it is graded.
- Wed Mar 13, 2019 1:21 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Catalyst vs. Intermediate
- Replies: 8
- Views: 763
Re: Catalyst vs. Intermediate
A catalyst is involved in the starting of the reaction, while an intermediate joins in later. Both of them are not included in the rate law.
- Wed Mar 13, 2019 1:20 pm
- Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
- Topic: Batteries
- Replies: 2
- Views: 489
Re: Batteries
A non-rechargeable battery is an example of galvanic cell
- Sun Mar 10, 2019 10:08 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Elementary Steps
- Replies: 1
- Views: 225
Re: Elementary Steps
Basically the elementary steps help you determine the rate for the whole reaction. The step that has the slowest rate would be the rate for the whole reaction.
- Sun Mar 10, 2019 10:05 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Final
- Replies: 18
- Views: 1955
Re: Final
The new materials would weight more percentage I think.
- Sun Mar 10, 2019 10:03 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: 797
Re: Log version vs ln Version
The ln version might be more convenient, but both log and ln give the same ratio/result.
- Sun Mar 10, 2019 10:01 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Test 2
- Replies: 12
- Views: 1058
Re: Test 2
Since a combustion releases heat, you can therefore say that the reaction is exothermic and Gibbs free energy is negative
- Sun Mar 10, 2019 9:59 pm
- Forum: First Order Reactions
- Topic: Molar coefficients
- Replies: 4
- Views: 469
Re: Molar coefficients
No, the coefficients do no effect order
- Wed Mar 06, 2019 5:17 pm
- Forum: Zero Order Reactions
- Topic: General Meaning of "Zero Order" Reactions
- Replies: 7
- Views: 698
Re: General Meaning of "Zero Order" Reactions
Danielle_Gallandt3I wrote:This typically occurs when the reactant concentration is already very high, so adding more reactant doesn't change the rate
Thank you for clarifying!
- Wed Mar 06, 2019 5:16 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: Units for rate laws
- Replies: 2
- Views: 373
Re: Units for rate laws
It is not necessary, but make sure to keep the units constant.
- Sat Feb 16, 2019 11:45 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Bond Enthalpies
- Replies: 4
- Views: 435
Re: Bond Enthalpies
If you know the lewis structures, it would be very helpful since you would know what bonds are breaking/forming.
- Sat Feb 16, 2019 11:40 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Pressure Equation
- Replies: 7
- Views: 787
Re: Pressure Equation
When the temperature is constant, you can either use V2/V1 or P1/P2 depends on what you are given because in the formula PV=nRT, P and V has a proportional relationship.
- Sat Feb 16, 2019 11:35 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Converting to q rev
- Replies: 4
- Views: 640
Re: Converting to q rev
Yes, qrev/Delta T would be the formula for irreversible reaction.
- Sat Feb 16, 2019 11:31 pm
- Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
- Topic: How to calculate W
- Replies: 9
- Views: 1383
Re: How to calculate W
(Numbers of possible ways)^numbers of molecules.
- Sun Jan 27, 2019 6:15 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Lecture Slides
- Replies: 5
- Views: 462
Re: Lecture Slides
Nope but the book covers pretty much everything that he mentions.
- Sun Jan 27, 2019 6:12 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Standard Temperature
- Replies: 7
- Views: 637
Re: Standard Temperature
I think it might be 25 Celcius degree.
- Sun Jan 27, 2019 6:09 pm
- Forum: Ideal Gases
- Topic: SI Units
- Replies: 5
- Views: 646
Re: SI Units
atm, but other units can also be used. Ps, different units of pressure are correspond to a different value of R.
- Sun Jan 27, 2019 6:07 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Catalysts in Kc
- Replies: 6
- Views: 676
Re: Catalysts in Kc
They speed up the process but do not change the concentrations.
- Sun Jan 27, 2019 6:07 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Inert Gas
- Replies: 6
- Views: 562
Re: Inert Gas
Since the volume is not changed after gas is being inserted, the partial pressure for each molecule is not changed therefore the equilibrium stays.
- Sun Jan 27, 2019 6:04 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Exothermic vs. Endothermic
- Replies: 10
- Views: 3139
Re: Exothermic vs. Endothermic
An exothermic reaction has a negative delta H while an endothermic reaction has a positive delta H. Delta H=Change in enthalpy.
- Sun Jan 27, 2019 6:02 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: ICE
- Replies: 19
- Views: 1424
Re: ICE
The concentration of reactants and products(excluded solids and liquids) in the equilibrium state.
- Sun Jan 27, 2019 5:54 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 5%
- Replies: 10
- Views: 744
Re: 5%
If the concentration of H+ or OH- is less than 5% of the concentration of HA or HB, you can ignore the x when it is being subtracted or added(i.e. 2-x=2).
- Sun Jan 13, 2019 10:12 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: HW PROBELM 1 PART D
- Replies: 4
- Views: 454
Re: HW PROBELM 1 PART D
Since the equilibrium constant(K) does not change, that means the ratio of product/reactant has to be constant. If you add more concentration to one of them, the other has to increase in order to make the ratio constant.
- Sun Jan 13, 2019 10:10 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Test Dates
- Replies: 3
- Views: 378
Re: Test Dates
It depends on when your discussion session is. Test 1 should be in week 3 and test 2 should be in week 7
- Sun Jan 13, 2019 10:07 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Pure Solids and Liquids
- Replies: 4
- Views: 667
Re: Pure Solids and Liquids
My TA said they dont affect equilibrium
- Sun Dec 02, 2018 12:04 am
- Forum: Hybridization
- Topic: lone pairs
- Replies: 20
- Views: 1991
Re: lone pairs
Yes, one lone pair is considered as one electron density. Since hybridization is based on the number of electron density, you consider lone pairs too.
- Sun Dec 02, 2018 12:01 am
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: polarizing power and polarizability
- Replies: 5
- Views: 668
Re: polarizing power and polarizability
Since polarizing power describes the power of cations pulling electrons from the anions, small and highly charged cations would have a strong polarizing power to distort the electron clouds from the anions. Polarizability is the ability for anions to pull their electrons. Big and highly charged anio...
- Sat Dec 01, 2018 11:54 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Lone pairs
- Replies: 4
- Views: 537
Re: Lone pairs
Lone pairs create strong repulsions since the charges are the same(negative). Therefore, they try to get away from each other and cause the bond angle to decrease. Also, the bonded atoms would most likely end up being close together since the lone pairs are getting away from each other.
- Tue Nov 27, 2018 12:42 pm
- Forum: Ionic & Covalent Bonds
- Topic: Question 6.9 ranking dipole forces
- Replies: 1
- Views: 742
Question 6.9 ranking dipole forces
6.9 Place the following types of molecular and ion interactions in order of increasing strength: (a) ion–dipole; (b) induceddipole–induced-dipole; (c) dipole–dipole in the gas phase; (d) ion–ion; (e) dipole–dipole in the solid phase. Can someone explain why is the order dipole-induced-dipole=dipole ...
- Sun Nov 25, 2018 5:26 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Formal charge vs octet rule
- Replies: 5
- Views: 760
Re: Formal charge vs octet rule
You should try to give every atom an octet, then you can see if the formal charges are all equal to zero. If not, then check to see if the central atom is in 3p orbital, therefore, you can violate the octet rule. Most of the times the structure should satisfy both the octet rule and the formal charge.
- Sun Nov 25, 2018 5:20 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Dipole
- Replies: 2
- Views: 280
Re: Dipole
A dipole is when a positively charged atom bonds with a negatively charged atom. The electronegative force between the two atoms is not the same, thus a dipole moment happens which is that one of the atoms is more electronegative than the other.
- Sun Nov 25, 2018 5:14 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Sigma vs pi bonds
- Replies: 7
- Views: 727
Re: Sigma vs pi bonds
A sigma bond is the very first bond between two atoms, while pi bonds are the ones that come after the sigma bond. For example in a triple bond, there is one sigma bond and two pi bonds.
Hope this helps.
Hope this helps.
- Sun Nov 18, 2018 10:05 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Lone pairs
- Replies: 5
- Views: 523
Re: Lone pairs
Yes, the lone pairs also affect the bond angles, and different type of VSEPR models have different bond angles.
- Sun Nov 18, 2018 10:02 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bond Angles for H2O
- Replies: 8
- Views: 8866
Re: Bond Angles for H2O
In my notes I have that since H2O has two lone pair electrons and two pairs of bonding electrons, the lone pairs make the bond angle decrease a bit.
Hope this helps.
Hope this helps.
- Sun Nov 18, 2018 10:00 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Molecular Shape Patterns
- Replies: 5
- Views: 565
Re: Molecular Shape Patterns
I think in the lecture we went over some notations about the VSEPR model: A=central atom X=bonded atom E=lone pair For example, AX3 is trigonal planar, AX2E2 is bend, AX4 is tetrahedral, AX4E is trigonal bipyramidal, and AX4E2 is Square planer. I think remembering these can save you some time. Hope ...
- Tue Nov 13, 2018 3:12 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Test 3
- Replies: 8
- Views: 1701
Re: Test 3
For 6th edition, do we also study chapter 6.4 and 6.5?
- Tue Nov 13, 2018 1:08 pm
- Forum: Administrative Questions and Class Announcements
- Topic: MIDTERM PRACTICE - Garlic Bread Review Session [ENDORSED]
- Replies: 121
- Views: 17168
Re: MIDTERM PRACTICE - Garlic Bread Review Session [ENDORSED]
Elle_Mendelson_4I wrote:Will someone explain 10A?
As more electrons and photons are added to the atom from left to right, the force of increasing protons creates a stronger pull that attracts the electrons to get closer to the nucleus. Therefore the atom shrinks for silicon and has a smaller radius than aluminum.
- Tue Nov 13, 2018 12:58 pm
- Forum: Administrative Questions and Class Announcements
- Topic: MIDTERM PRACTICE - Garlic Bread Review Session [ENDORSED]
- Replies: 121
- Views: 17168
Re: MIDTERM PRACTICE - Garlic Bread Review Session [ENDORSED]
For number 5, I keep getting .127 M after setting the problem up like (.211 M)(.150 L) = M2(.250 L). But in my notes, I believe Lyndon got 1.69 x 10^-2. I was wondering if anyone knows what I am doing wrong. Thanks! Hi! Since the problem stated that only 20ml was removed to the 2nd flask, you put 0...
- Tue Nov 13, 2018 12:55 pm
- Forum: Bond Lengths & Energies
- Topic: Drawing resonance structures?
- Replies: 6
- Views: 665
Re: Drawing resonance structures?
The resonance structures should be equally stable. However, the Lewis structure for this specific compound does not represent its real appearance because a compound that has resonance structures actually have the resonance bond constantly changing from atom to atom, so that is why we said we can hav...
- Sun Nov 04, 2018 4:14 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: HW 1.15, 6th edition
- Replies: 1
- Views: 412
Re: HW 1.15, 6th edition
1)Convert 102.6nm to 1.03*10^-7m.
2)Use c=v*lamda to find the frequency.
3)Use Rydberg formula, v=R(1/(n^2)-1/(n^2)) to find n2. Note that the first n is n1 and the second n is n2.
4)Since it's Lyman's series, you know n1=1.
2)Use c=v*lamda to find the frequency.
3)Use Rydberg formula, v=R(1/(n^2)-1/(n^2)) to find n2. Note that the first n is n1 and the second n is n2.
4)Since it's Lyman's series, you know n1=1.
- Sun Nov 04, 2018 3:43 pm
- Forum: Administrative Questions and Class Announcements
- Topic: MIDTERM PRACTICE - Garlic Bread Review Session [ENDORSED]
- Replies: 121
- Views: 17168
Re: MIDTERM PRACTICE - Garlic Bread Review Session [ENDORSED]
For number 5, I keep getting .127 M after setting the problem up like (.211 M)(.150 L) = M2(.250 L). But in my notes, I believe Lyndon got 1.69 x 10^-2. I was wondering if anyone knows what I am doing wrong. Thanks! Hi! Since the problem stated that only 20ml was removed to the 2nd flask, you put 0...
- Sun Nov 04, 2018 11:31 am
- Forum: Administrative Questions and Class Announcements
- Topic: MIDTERM PRACTICE - Garlic Bread Review Session [ENDORSED]
- Replies: 121
- Views: 17168
Re: MIDTERM PRACTICE - Garlic Bread Review Session [ENDORSED]
Hi can anyone explain 8a? I don't know how to correctly word my answers...
- Sun Oct 28, 2018 11:10 pm
- Forum: Lewis Structures
- Topic: Electron Configurations
- Replies: 3
- Views: 298
Re: Electron Configurations
You remove electrons starting with the highest level. Since there is only one electron in the 4s shell, you need to subtract another electron from the 3d shell.
Hope this helps.
Hope this helps.
- Sun Oct 28, 2018 11:04 pm
- Forum: Ionic & Covalent Bonds
- Topic: Cations/Anions
- Replies: 4
- Views: 320
Re: Cations/Anions
For your first example, the whole 5p1 represents one electron only. In the future, you can know the number of electrons in each shell by looking at their superscript. For example, 5p5 means there are 5 electrons in the 5p shell. For your second example, p shells contain 6 electrons in total. In orde...
- Tue Oct 23, 2018 10:21 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Rydberg Equation
- Replies: 7
- Views: 673
Re: Rydberg Equation
I think in the book they stated that it should be n(initial)-n(final). I ran into the same problem. For one of the homework questions, I got a negative answer when I put n(initial)-n(final), but the answer key says it is positive. They flipped the other to get a positive number. I think I'll go with...
- Sun Oct 21, 2018 11:04 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Heisenberg equation
- Replies: 2
- Views: 312
Re: Heisenberg equation
I have the same question too.
- Sun Oct 21, 2018 11:00 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Coulomb's Law and Effective Nuclear Charge on test
- Replies: 2
- Views: 212
Re: Coulomb's Law and Effective Nuclear Charge on test
I think you should at least be familiar with it. Even though we didn't do too much on those topics, but it doesn't hurt to learn a little more.
- Sun Oct 21, 2018 10:55 pm
- Forum: Properties of Light
- Topic: Test 2 Equations
- Replies: 14
- Views: 1031
Re: Test 2 Equations
I think you should be familiar with them, but don't try too hard to memorize them. I would recommend knowing the E of photon formula, De Broglie Equation, the Uncertainty Principle, and the Photoelectric effect.
- Thu Oct 11, 2018 11:34 pm
- Forum: Properties of Electrons
- Topic: Quantum World
- Replies: 6
- Views: 511
Re: Quantum World
Yes, short wavelength lights have high frequency and long wavelength lights have low frequency. This can be proved by using the electromagnetic equation c=vλ where c is the speed of light, v is the frequency, and λ is the wavelength. They have a universal relationship.
- Thu Oct 11, 2018 11:23 pm
- Forum: Balancing Chemical Reactions
- Topic: Balancing Chemical Equations [ENDORSED]
- Replies: 4
- Views: 382
Re: Balancing Chemical Equations [ENDORSED]
In order to balance a chemical equation, you need to figure out the reactants and products first. In this case, you only have one compound which means this is not a chemical equation. After you have had all the reactants and products, you can then try to come up with accurate coefficients in front o...
- Thu Oct 11, 2018 11:19 pm
- Forum: SI Units, Unit Conversions
- Topic: formula units [ENDORSED]
- Replies: 69
- Views: 32401
Re: Solution Concentration [ENDORSED]
How do you know which is the initial molarity, initial volume, final molarity, and/or final volume from a given problem? How do you figure it out? I think most of the questions will state them if not, you can look for hints in the question. For example, if the question is adding water to dilute the...
- Thu Oct 04, 2018 4:19 pm
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Conversion of grams to moles
- Replies: 4
- Views: 414
Re: Conversion of grams to moles
Yes. For example, if the question asks you to convert 2.0g of CO2 to moles. What you do is first add up the molar mass for CO2 which is 12.011(C)+15.999*2(O)=44.009grams. Then you use 2/44.009 to get the moles. You always consider the subscripts.
- Thu Oct 04, 2018 4:16 pm
- Forum: Molarity, Solutions, Dilutions
- Topic: Concentration- Calculating Volume
- Replies: 4
- Views: 372
Re: Concentration- Calculating Volume
When asked to look for Molarity/volume/moles, one of the common equation that we use is M=moles/volume. You are given the moles and molarity, which means you can use this formula to find the volume.
- Thu Oct 04, 2018 4:02 pm
- Forum: Empirical & Molecular Formulas
- Topic: Problem F.1b
- Replies: 3
- Views: 394
Re: Problem F.1b
I think as long as your answer is close enough to the book answer, TAs won't make you wrong. In this case, your answer is very close.