Search found 62 matches
- Sat Mar 16, 2019 8:47 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Delta S?
- Replies: 2
- Views: 565
Re: Delta S?
Irreversible situations are always in isolated containers. This means delta S of surroundings equals delta S of system so total delta S is 0.
- Sat Mar 16, 2019 8:46 pm
- Forum: General Rate Laws
- Topic: coefficient of product
- Replies: 1
- Views: 457
Re: coefficient of product
You can directly use the coefficients of a balanced reaction for the rate law of an intermediate equation.
- Sat Mar 16, 2019 8:45 pm
- Forum: Student Social/Study Group
- Topic: Lyndon's Review Question 7 clarification
- Replies: 2
- Views: 609
Re: Lyndon's Review Question 7 clarification
delta G = delta G (eq 1) - delta G (eq 2)
You are subtracting the delta Gs from each other, but also be very aware of the negative signs from -nFE.
In total it should be:
-nFE(total) = -nFE(eq1) + nFE(eq2)
You will get 1.26 V
You are subtracting the delta Gs from each other, but also be very aware of the negative signs from -nFE.
In total it should be:
-nFE(total) = -nFE(eq1) + nFE(eq2)
You will get 1.26 V
- Sat Mar 16, 2019 8:42 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: THERMO with KINETICS
- Replies: 2
- Views: 538
Re: THERMO with KINETICS
I would say the graph of different steps of equations that have intermediates is a good concept to test us on both. There is kinetics in terms of speed of reaction and also thermo with Gibbs free energy.
- Sat Mar 16, 2019 8:39 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Activation Energy
- Replies: 3
- Views: 340
Re: Activation Energy
It is not inverse. Activation energy is a part of the negative exponent. But, this means that a higher activation energy is related to a lower rate, just not directly.
- Sat Mar 16, 2019 11:42 am
- Forum: Bronsted Acids & Bases
- Topic: pH and pOH
- Replies: 1
- Views: 534
Re: pH and pOH
Bronsted acids and bases participate in the conjugate seesaw, meaning a weak acid and base either gains or loses a H+ to become the conjugate acid/base. This results in an OH- or H30+ ion being created. These directly contribute to the pH.
- Sat Mar 16, 2019 11:40 am
- Forum: General Rate Laws
- Topic: exponential decay
- Replies: 2
- Views: 554
Re: exponential decay
Rate laws are usually directly dependent on the amount of reactants, so if the reactants are lower, the rate law will be lower.
- Sat Mar 16, 2019 11:37 am
- Forum: Calculating Work of Expansion
- Topic: expansion work question
- Replies: 1
- Views: 505
Re: expansion work question
If there is said to be no change in volume, then no expansion work has been done. If you are given moles and temperature, you can calculate work from -nRT. If that is positive and you are not in an isolated system, expansion work has been done.
- Sat Mar 16, 2019 11:35 am
- Forum: *Enzyme Kinetics
- Topic: graphing intermediates
- Replies: 2
- Views: 435
Re: graphing intermediates
No graphing of catalysts is needed. The intermediates are essentially your product after your first reaction that are your reactants of your second reaction.
- Sat Mar 16, 2019 11:34 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Phases Cell Diagram
- Replies: 2
- Views: 311
Re: Phases Cell Diagram
It is always solid on the outside, then gases/liquids, then aqueous
- Sat Mar 16, 2019 11:32 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Shifting K with changes in volume
- Replies: 4
- Views: 636
Shifting K with changes in volume
So I know that the reaction will shift toward the side with less moles of gas if the volume is getting smaller/pressure is getting bigger. But what happens if the volume is getting bigger and the pressure is getting smaller? Will the reaction shift to the side with more moles of gas?
- Sat Mar 16, 2019 11:31 am
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Coefficients for the rate of reaction
- Replies: 1
- Views: 168
Coefficients for the rate of reaction
Why is that you can use the coefficients from a reaction in the rate law for elementary reaction but not other types of reactions?
- Fri Mar 15, 2019 9:41 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Electrolytic cell
- Replies: 2
- Views: 264
Electrolytic cell
What kinds of problems do we have to be able to do with electrolytic cells? Or do we just have to know that they are the opposite of galvanic cells?
- Fri Mar 15, 2019 5:49 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Test 2 question 7b
- Replies: 1
- Views: 345
Re: Test 2 question 7b
Since this releases heat, it seems like it is a spontaneous reaction.
- Fri Mar 15, 2019 5:44 pm
- Forum: Balancing Redox Reactions
- Topic: Test 2
- Replies: 5
- Views: 460
Re: Test 2
Reducing ability is the ability for a molecule to reduce another molecule and oxidize itself. When ranking these molecules, the ones that will oxidize the strongest are the ones with the lowest standard reduction potential.
- Fri Mar 15, 2019 5:41 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Test 2 question 7b
- Replies: 1
- Views: 345
Test 2 question 7b
The dissolving of a salt in water which causes the release of a small amount of heat.
Is this spontaneous, non spontaneous, or at equilibrium?
Is this spontaneous, non spontaneous, or at equilibrium?
- Fri Mar 15, 2019 5:07 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Test 2 help!
- Replies: 3
- Views: 434
Re: Test 2 help!
I used the van't Hoff equation to get the equilibrium constant at 40 degrees Celsius, but how do I use this to find pH?
- Fri Mar 15, 2019 3:54 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Test 2 help!
- Replies: 3
- Views: 434
Test 2 help!
Could someone help me out with an explanation for #5? This is the question that asks for an analysis of whether the pH of a water solution is acidic or basic?
- Fri Mar 15, 2019 3:30 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Increasing volume
- Replies: 5
- Views: 723
Increasing volume
So I know if you decrease volume, K will shift to increase whichever side has less moles of gas. But, if volume increases, will K shift to increase whichever side has more moles of gas? or will K not change at all?
- Thu Mar 07, 2019 11:06 pm
- Forum: Zero Order Reactions
- Topic: definitions
- Replies: 2
- Views: 307
definitions
Can someone define zero, first, second order reactions? I thought it had to do with how many components are coming together, but that wouldn't make sense for a zero order rxn.
- Thu Mar 07, 2019 9:51 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Electrodes in a concentration cell
- Replies: 1
- Views: 245
Re: Electrodes in a concentration cell
Nope. The Ecell value is intensive, meaning it isn't determined by the volume of the reactants or products.
- Thu Feb 28, 2019 11:18 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Standard Conditions
- Replies: 1
- Views: 174
Re: Standard Conditions
The standard conditions relate to being at equilibrium for E and a balanced equation for n.
- Thu Feb 28, 2019 11:17 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Finding n for Galvanic Cell Equations
- Replies: 2
- Views: 293
Re: Finding n for Galvanic Cell Equations
Exactly. It is the amount of electrons transferred.
- Thu Feb 28, 2019 11:17 pm
- Forum: Balancing Redox Reactions
- Topic: Short hand notation
- Replies: 8
- Views: 802
Re: Short hand notation
A salt bridge is a tube that is enclosed and allows for transfer of the salt ion from cathode to anode.
- Thu Feb 28, 2019 11:16 pm
- Forum: Balancing Redox Reactions
- Topic: Adding H+ and H2O
- Replies: 13
- Views: 2794
Re: Adding H+ and H2O
You can do both. Both are needed to balance reactions.
- Thu Feb 28, 2019 11:13 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: H+ in cell diagrams
- Replies: 5
- Views: 583
Re: H+ in cell diagrams
The only things that we add into cell diagrams are the solid and the salt ions. I don't think H+ is ever supposed to be in cell diagrams.
- Tue Feb 12, 2019 5:22 pm
- Forum: Phase Changes & Related Calculations
- Topic: Negative and Positive values of delta H and w
- Replies: 6
- Views: 3779
Negative and Positive values of delta H and w
Can someone explain the transfer of energy that happens when both delta H and w are negative and positive? I know the when work is positive, energy is going into the system. This means that some sort of pressure is condensing the system or the volume is getting smaller. When delta H is negative, is ...
- Thu Jan 10, 2019 11:14 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Q vs K
- Replies: 5
- Views: 414
Re: Q vs K
Q and K and calculated the same exact way: concentration of products over concentration of reactants. However, Q calculates the status of a reaction when it is not in equilibrium; the purpose is to understand what direction the reaction is currently moving in.
- Thu Jan 10, 2019 11:07 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Clarification from lecture 1 - Jan 7th
- Replies: 2
- Views: 162
Re: Clarification from lecture 1 - Jan 7th
All values for the reactants and products will be the same. However, if you are just finding the equilibrium constant of the inverse, you know that the numerator and denominator of the reaction will be flipped. So, you can simply take the inverse of the equilibrium for the forward reaction.
- Thu Jan 10, 2019 10:46 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 5H3 from 7th edition
- Replies: 2
- Views: 99
5H3 from 7th edition
The problem asks you to the find the equilibrium constant of a reaction from a separate table in the book. 2BrCl + H2 --> Br2 + 2HCl can be broken down into 2BrCl --> Br2 + Cl2 AND H2 + Cl2 --> 2HCl and the equilibrium constants for both of these reactions can be found in the table. However, the ans...
- Fri Dec 07, 2018 11:08 pm
- Forum: Coordinate Covalent Bonds
- Topic: Chelates
- Replies: 4
- Views: 702
Re: Chelates
Chelates are basically complexes that have ligands that form a ring of atoms around the transition metal ion. When ligands bond at more than one tie, they are likely to form a chelate.
- Fri Dec 07, 2018 11:07 pm
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Difference Between Polarizability and Polarizing Power
- Replies: 3
- Views: 5046
Re: Difference Between Polarizability and Polarizing Power
Polarizability is how easy it is to move or pull an atom's cloud of electrons. Polarizing power is how good an atom is at pulling on bonded electrons. These two concepts are directly opposite. Atoms with high polarizability are bigger and have a greater negative charge, while atoms that have a highe...
- Fri Dec 07, 2018 11:05 pm
- Forum: Biological Examples
- Topic: What should we know for the final?
- Replies: 9
- Views: 982
Re: What should we know for the final?
I definitely think we should know cisplatin! It is the well known chemotherapy drug that forms coordination compounds with DNA to stop cell division. The two chlorides are on one side and can bond with the guanines in two separate locations to effectively stop uncontrolled division.
- Fri Dec 07, 2018 11:01 pm
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Least to Most Polarizable/Polarizing Power
- Replies: 3
- Views: 2021
Re: Least to Most Polarizable/Polarizing Power
Both size and charge need to be taken into account when organizing atoms. The charge density, which is a measure of the charge in terms of the volume that the atom takes up, is used to compare atoms to each other (not solely charge or solely size). s2- is smaller and should be more difficult to pola...
- Fri Dec 07, 2018 10:55 pm
- Forum: Hybridization
- Topic: Sigma and pi bonds
- Replies: 5
- Views: 506
Re: Sigma and pi bonds
We need to know the hybridization of the bonds. This means we must be able to find the hybridization of the neighboring atoms and represent the bond with both of them.
- Fri Dec 07, 2018 10:54 pm
- Forum: Sigma & Pi Bonds
- Topic: Rotation
- Replies: 5
- Views: 1029
Re: Rotation
This relates directly to labeling molecules as bidentate. My TA gave an example of two aspects of a molecule connected by a double bond versus a single bond. The single bond could spin any way it wanted to, so rotating one aspect of the molecule 180 degrees put the two nitrogen atoms right next to e...
- Fri Dec 07, 2018 10:44 pm
- Forum: Hybridization
- Topic: Hybridizaiton
- Replies: 1
- Views: 268
Re: Hybridizaiton
Hybridization isn't necessarily lowering the energy to allow an atom to form more bonds. Instead, it is establishing that all electrons have an equal likelihood of forming an equal bond with another atom. For carbon, this does seem to look like you are forming more bonds as you move from 2 unpaired ...
- Fri Dec 07, 2018 10:42 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Final Exam
- Replies: 1
- Views: 413
Re: Final Exam
All the equations we learned related to the quantum world will be given to us on the test, so memorization is not needed. The equations such as E=hv and c = wavelength(v) deal specifically with photons. De Broglie's equation, wavelength = h/p and kinetic energy E=(1/2)mv^2 are for any particle that ...
- Fri Dec 07, 2018 1:45 pm
- Forum: Lewis Acids & Bases
- Topic: Bronsted vs Lewis
- Replies: 4
- Views: 380
Bronsted vs Lewis
What's the main difference between Brontsted acids and bases and Lewis acids and bases? Why is AlCl3 a Lewis acid as opposed to a Bronsted acid?
- Fri Dec 07, 2018 1:43 pm
- Forum: General Science Questions
- Topic: Determining states
- Replies: 1
- Views: 331
Determining states
When writing out a full reaction of molecules, how do we know whether a molecule is a solid, liquid, gas, or aqueous? Are we just supposed to memorize the states of important molecules?
- Mon Nov 26, 2018 10:21 pm
- Forum: Bond Lengths & Energies
- Topic: Bond Length
- Replies: 2
- Views: 255
Re: Bond Length
Single bonds have the longest bond lengths. As it progresses to double and triple bonds, the bond lengths get shorter.
- Mon Nov 26, 2018 9:27 pm
- Forum: Hybridization
- Topic: hybridization
- Replies: 3
- Views: 345
Re: hybridization
Also, when an atom bonds, it realistically forms bonds that are equal in strength. Therefore, hybridization mixes together different orbital levels to create an entirely new orbital that equalizes all bonds.
- Mon Nov 26, 2018 8:18 pm
- Forum: Sigma & Pi Bonds
- Topic: Homework 2F.3 7th Edition Part B
- Replies: 1
- Views: 165
Re: Homework 2F.3 7th Edition Part B
The resonance structure of SO2 would also include a Lewis structure that only had one bond between S and an O. Resonance structure simply refers to another way of arranging the electrons in a way that fits them all in. The most stable structure would be the one with 2 double bonds because the formal...
- Mon Nov 26, 2018 6:12 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: 2F3 part B (7th edition)
- Replies: 1
- Views: 113
2F3 part B (7th edition)
The problem asks about the amount of sigma and pi bonds in the molecule SO2. The answer key gives two answers (2 sigma, 2 pi OR 2 sigma, 1 pi depending on resonance structure). It seems like the problem is considering the resonance structures as one double bond between the S and an O and two double ...
- Sun Nov 04, 2018 10:37 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Ionization Energies
- Replies: 4
- Views: 372
Re: Ionization Energies
Yes. It gets progressively harder to remove electrons. We are getting closer to the positively charged nucleus that is pulling electrons towards it.
- Sun Nov 04, 2018 10:07 pm
- Forum: Resonance Structures
- Topic: Resonance Structures
- Replies: 3
- Views: 388
Re: Resonance Structures
I think so. If a problem asks for the Lewis structure, we should show all logical possibilities of it.
- Sun Nov 04, 2018 10:01 pm
- Forum: Lewis Structures
- Topic: Expanded Octet Rule
- Replies: 1
- Views: 79
Re: Expanded Octet Rule
If the atom includes d orbitals, it is 10. If the atom includes f orbitals, it is 14.
- Sun Nov 04, 2018 10:01 pm
- Forum: Ionic & Covalent Bonds
- Topic: electronegativity difference
- Replies: 4
- Views: 553
Re: electronegativity difference
If you look at a periodic table that includes electronegativity of atoms, you can calculate the electronegativity difference between the 2 bonding atoms and determine which molecule is more electronegative. C - 2.55 S - 2.58 O - 3.44 There is a greater difference between C and O, making CO2 more ele...
- Sun Nov 04, 2018 9:55 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Formal Charge and Lewis Structures
- Replies: 5
- Views: 612
Re: Formal Charge and Lewis Structures
I don't think so. I'm guessing the question will explicitly ask for the formal charge if needed.
- Sun Nov 04, 2018 9:47 pm
- Forum: Photoelectric Effect
- Topic: Work Function, Kinetic Energy
- Replies: 2
- Views: 639
Re: Work Function, Kinetic Energy
Energy of photon - work function = kinetic energy
If you just need to find the kinetic energy and you have the velocity, plug in the mass of the electron (given value) and solve Ek = (1/2)mv^2.
If you just need to find the kinetic energy and you have the velocity, plug in the mass of the electron (given value) and solve Ek = (1/2)mv^2.
- Sun Nov 04, 2018 8:55 pm
- Forum: Resonance Structures
- Topic: Resonance with formal charge
- Replies: 6
- Views: 587
Re: Resonance with formal charge
Yes. Resonance is simply different ways of drawing a molecule's structure in terms of double bonds. Formal charge is the most stable structure of all resonance structures.
- Sun Nov 04, 2018 8:49 pm
- Forum: Ionic & Covalent Bonds
- Topic: Identifying ionic compounds
- Replies: 1
- Views: 200
Re: Identifying ionic compounds
Usually bonds between metals and non-metals are ionic and bonds between non-metals and non-metals are covalent. When looking at bonding between molecules, however, I think we just have to be aware of the common ionic molecules. NH^4 always has a positive charge and OH- always has a negative charge.
- Sun Nov 04, 2018 8:47 pm
- Forum: Properties of Electrons
- Topic: Frequency of an electron equation
- Replies: 2
- Views: 537
Re: Frequency of an electron equation
De Broglie's equation is used with things that have mass (i.e. electrons). The photoelectric effect includes three components. E=hv is used ONLY for photons/light. The threshold equation is the energy needed to eject an electron and that is usually a given value. The kinetic energy of the electron i...
- Sun Nov 04, 2018 8:40 pm
- Forum: Photoelectric Effect
- Topic: Test 2 #4 neon lamp light emitted
- Replies: 1
- Views: 295
Re: Test 2 #4 neon lamp light emitted
Convert kilojoules to joules. Use E/h = v. The answer should be 5.45 x 10^14 Hz.
- Sun Nov 04, 2018 8:37 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Uncertainty concept
- Replies: 1
- Views: 256
Re: Uncertainty concept
When diameter of a region is referred to in a Heisenberg uncertainty principle problem, the question is usually asking whether the electron is within that region (alveoli sac in this question). If the delta x is larger than the diameter of the region, we know that the electron is not confined to tha...
- Sun Nov 04, 2018 8:36 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Formal charges in charged molecules
- Replies: 5
- Views: 290
Re: Formal charges in charged molecules
There is no difference in process. You still draw all the resonance Lewis structures and use the F = valence - (non bonding electrons - (bonding electrons/2)) equation.
- Sun Nov 04, 2018 8:06 pm
- Forum: Lewis Structures
- Topic: Double bonds vs. lone pairs
- Replies: 5
- Views: 3063
Re: Double bonds vs. lone pairs
Before even calculating formal charge, we have to find a structure that contains all 20 valence electrons. Carbon is in the middle because it has 4 potential bonding sites. We know the both hydrogens have to bond to carbon with a single bond because hydrogens can only have two electrons in their val...
- Sun Nov 04, 2018 8:01 pm
- Forum: *Shrodinger Equation
- Topic: Midterm
- Replies: 3
- Views: 613
Re: Midterm
I don't think so. I think we just need to conceptually understand it, but we do not need to ever apply the equation.
- Sun Nov 04, 2018 8:00 pm
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Electron Configuration
- Replies: 4
- Views: 518
Re: Electron Configuration
The electron configuration of nickel is [Ar]3d^8 4s^2. When you take away 3 electrons to make it Ni3+, you take 2 electrons off of the 4s orbital (highest energy state) and one electron off the 3p orbital. This is not to be confused with considering Ni3+ to be Mn. The electron configuration of Mn is...
- Sun Nov 04, 2018 7:13 pm
- Forum: Properties of Light
- Topic: Quantum Test
- Replies: 11
- Views: 1199
Re: Quantum Test
Since the equations are all provided for us, I think we just have to understand when to use them. E = hν, c = λν, and, therefore, E = hc/λ, are only used for calculations relating to light/photons. De Broglie's equation, λ = h/mv, is mostly used for particles that have mass, but it can also be appli...
- Sun Nov 04, 2018 6:56 pm
- Forum: Properties of Light
- Topic: 3b on Quantum Test
- Replies: 2
- Views: 283
Re: 3b on Quantum Test
The speed does not change as intensity increases. Since photons have particle properties, they can only eject one electron at a time. Increasing intensity will only increase the amount of electrons ejected.
- Sun Nov 04, 2018 6:38 pm
- Forum: Empirical & Molecular Formulas
- Topic: Limiting Reactants
- Replies: 3
- Views: 586
Re: Limiting Reactants
Either product can be used to understand which reactant is limiting. The moles and of product are always proportional to each other, and they both rely on the same limiting reactant to determine how much is produced.