Search found 53 matches
- Wed Feb 13, 2019 11:26 am
- 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: Degeneracy at its max
- Replies: 2
- Views: 35
Re: Degeneracy at its max
In addition, when the entropy of the system is in equilibrium the entropy of the system is equal to the entropy of the surroundings.
- Wed Feb 13, 2019 11:23 am
- Forum: Calculating Work of Expansion
- Topic: Work of the system
- Replies: 3
- Views: 7
Re: Work of the system
You can assume work is equal to 0 in a vacuum where the external pressure is 0
- Wed Feb 13, 2019 11:21 am
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: 6th edition example 9.6
- Replies: 1
- Views: 11
Re: 6th edition example 9.6
No, I don't think so. You should know the equations on the constant and equations sheet provided. In addition, you should know the equations for derived equations for entropy and work like Lavelle showed us in class.
- Wed Feb 13, 2019 11:20 am
- Forum: Phase Changes & Related Calculations
- Topic: Chapter 8 number 21
- Replies: 4
- Views: 23
Re: Chapter 8 number 21
It doesn't matter which sign you attribute to the system or surroundings. As long as you understand the system and surroundings are equal but opposite in sign, you should get the correct answer.
- Wed Feb 13, 2019 11:18 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Ideal Gas C
- Replies: 2
- Views: 26
Re: Ideal Gas C
You can find those values according to the equipartition theorem for an ideal gas and use U=3/2nRT to substitute and find the values for Cp and Cv. It's on the constant and equations sheet. Just remember to use those for monoatomic ideal gases.
- Wed Feb 06, 2019 11:11 am
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Irreversible/Reversible Processes
- Replies: 2
- Views: 20
Re: Irreversible/Reversible Processes
In addition, in an isothermal irreversible reaction, the pressure is constant. Therefore, the amount of work done is -Pex*V. Because it is isothermal, no heat is lost or gained. In an isothermal reversible reaction, the pressure and volume are increasing or decreasing in small incremental steps. Bec...
- Wed Feb 06, 2019 11:03 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Units
- Replies: 2
- Views: 21
Units
I understand how to do the problems in order to get the enthalpy of a reaction. However, I am confused when the units should be J/mol or just J when calculating enthalpy.
- Wed Feb 06, 2019 11:01 am
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Midterm [ENDORSED]
- Replies: 47
- Views: 434
Re: Midterm [ENDORSED]
I also recommend watching Youtube videos in order to review major concepts. In addition, I like doing the worksheets Karen posts on Chemistry Community. I also like to take notes down while reading the textbook. Reviewing my notes, doing as many problems I can, and attending the reviews sessions has...
- Thu Jan 31, 2019 1:44 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: to change a system
- Replies: 2
- Views: 26
Re: to change a system
As seen in the problems in the book, I noticed that most systems we will be dealing with are closed like pistons. However, work can be done on an open system such as taking a coffee stirrer and stirring coffee. This action represents a force being applied over a distance and it interrupts the moveme...
- Thu Jan 31, 2019 1:36 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: open, closed, isolated system and calculating internal work
- Replies: 1
- Views: 24
Re: open, closed, isolated system and calculating internal work
2. Internal energy is a state function, which means that it is a property that depends only on the current state and disregards how the system was prepared. The internal energy of an object is the sum of the potential and kinetic energy it possesses. You cannot measure the absolute or exact value of...
- Thu Jan 31, 2019 1:21 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Reversible reactions
- Replies: 1
- Views: 15
Re: Reversible reactions
If a system is at equilibrium the external pressure is equal to the internal pressure. In an irreversible system, the external and internal pressures are different and therefore work must be done in order to restore the equilibrium. Because of this instability, the system will expand if the external...
- Sun Jan 27, 2019 3:40 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: 3 Methods to solve for Enthaply
- Replies: 3
- Views: 18
Re: 3 Methods to solve for Enthaply
Because this post will probably be really long if I explained everything, I would refer to Lavelle's lecture notes. His notes break down how to solve the enthalpy for the reactions. If you want a review, I love watching youtube videos. I will leave several links below if you want more examples. http...
- Sun Jan 27, 2019 3:36 pm
- Forum: Ideal Gases
- Topic: Approximations for ICE
- Replies: 13
- Views: 48
Re: Approximations for ICE
In regards to equilibrium equations, you must see the K value when making an assumption. If the K value is less than 10^-3, then you can proceed using x. However, make sure you check your assumption with the 5% condition.
- Fri Jan 25, 2019 1:05 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Adding Inert Gas
- Replies: 10
- Views: 73
Re: Adding Inert Gas
Because an inert gas does not react with the reactants or products, it is essentially not changing the concentration of the products and reactants. In addition, the volume is constant so the concentrations remain untouched. Therefore, this will not effect equilibrium.
- Sun Jan 20, 2019 12:17 pm
- Forum: Acidity & Basicity Constants and The Conjugate Seesaw
- Topic: pKa and Ka
- Replies: 1
- Views: 28
Re: pKa and Ka
Because polyprotic compounds can dissociate multiple times, there will be multiple pKa values for every reaction that occurs. Depending on the information given in the question u will be able to find Ka for a given step.
- Sun Jan 20, 2019 12:14 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Ka and Kb as Inverses?
- Replies: 7
- Views: 47
Re: Ka and Kb as Inverses?
Just to be safe, I would use what we know. And kA*kb=kw is given so use that.
- Sun Jan 20, 2019 12:12 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Sig figs in pH
- Replies: 7
- Views: 33
Re: Sig figs in pH
Depending on the significant figures of the data given in the problem, you will have that many sig figs after the decimal for pH. For example say if you were given a K value of two significant figures a potential pH value could be 2.88. You can double check on the website under everything about sig ...
- Sat Jan 12, 2019 8:51 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Keq
- Replies: 3
- Views: 21
Keq
Is Keq different from Kc, or does it represent the same thing? Also, will we be marked wrong if we wrote Keq instead of Kc for the chemical equilibrium equation?
- Sat Jan 12, 2019 8:45 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: (aq) in calculating K
- Replies: 9
- Views: 38
Re: (aq) in calculating K
These short notations in a chemical reaction represent the form or state of the compound in the equation. "Aq" stands for aqueous solution, "s" represents a solid, "g" represents a gas state, and "l" represents a pure liquid form. When you see a compound with ...
- Sat Jan 12, 2019 8:40 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Change in concentration
- Replies: 3
- Views: 22
Re: Change in concentration
Because Kc measures the concentrations at equilibrium, it is a constant that remains unchanged even if more products or reactants are added as it is a fixed ratio. If there is a change in the initial concentration of reactants and products in a question, then you will be finding Q.
- Sat Dec 08, 2018 9:40 pm
- Forum: Conjugate Acids & Bases
- Topic: Strong acids
- Replies: 3
- Views: 30
Re: Strong acids
a weak conjugate base means a stronger acid
- Sat Dec 08, 2018 3:22 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Relation between Equilibrium Constant and pH
- Replies: 1
- Views: 27
Re: Relation between Equilibrium Constant and pH
when Ka is given you can set up the formula of ka=product of the product concentrations/product of reactant concentrations and solve for the [H+] concentration. Then you would take the -log to find the pH.
- Tue Dec 04, 2018 11:02 am
- Forum: Conjugate Acids & Bases
- Topic: B(OH)3 conjugate base
- Replies: 1
- Views: 29
Re: B(OH)3 conjugate base
Because an acid is a proton donor, it will lose the hydrogen. Therefore, the conjugate base will be H2B03.
- Tue Dec 04, 2018 10:56 am
- Forum: Naming
- Topic: Roman Numerals
- Replies: 3
- Views: 31
Re: Roman Numerals
The transition metals must have roman numerals that match the ion charge.
- Tue Dec 04, 2018 10:53 am
- Forum: Administrative Questions and Class Announcements
- Topic: Naming on the Final
- Replies: 4
- Views: 73
Re: Naming on the Final
I've been memorizing the table in the book in order to remember the names of the molecules. In addition, another helpful source is quizlet. There are many flashcards created to memorize these formulas. I do believe that complicated acids will be provided on the final.
- Sun Dec 02, 2018 4:45 pm
- Forum: *Molecular Orbital Theory Applied To Transition Metals
- Topic: Transition Metals
- Replies: 5
- Views: 68
Re: Transition Metals
Transition metals have many oxidation states because they have the d shell where they can lose electrons from.
- Sun Dec 02, 2018 4:42 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Final [ENDORSED]
- Replies: 5
- Views: 112
Re: Final [ENDORSED]
I know they have review sessions as Dr. Lavelle showed us the pdf in class. I just wanted to know if there would be a practice final like we had on the midterm?
- Sun Dec 02, 2018 4:40 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Molecular shape in relation to polarity and boiling point
- Replies: 5
- Views: 47
Re: Molecular shape in relation to polarity and boiling point
When looking at the Lewis Structure of the molecule, you can see if that molecule has single, double, or triple bonds. Depending on that, you can see how tightly bound the atoms are to the central atom. The higher the bond strength, the harder it is to break the bonds apart or leading to a higher bo...
- Sun Dec 02, 2018 4:35 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Final [ENDORSED]
- Replies: 5
- Views: 112
Final [ENDORSED]
Will there be a practice final exam released on chemistry community like "garlic bread"? Or will we be doing practice during the review sessions this week?
- Sun Nov 25, 2018 2:14 pm
- Forum: Hybridization
- Topic: sp orbitals
- Replies: 3
- Views: 45
Re: sp orbitals
The 2 and 3 represent the number of p orbitals that are being hybridized.
- Sun Nov 25, 2018 2:12 pm
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Polarizability
- Replies: 5
- Views: 47
Re: Polarizability
I may be wrong, but from what I understand is this means that the more electrons that are distorted or unevenly distributed within the cloud, the greater the separation of charge. This separation of charge makes the molecule highly polarizable.
- Sun Nov 25, 2018 2:05 pm
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: Electron-deficient compounds
- Replies: 1
- Views: 18
Re: Electron-deficient compounds
As far as the examples we've done in class with Lavelle, I don't think we need to know that for the test. But, its good to know what they are.
- Sun Nov 18, 2018 3:31 pm
- Forum: Hybridization
- Topic: Energy Level
- Replies: 2
- Views: 76
Re: Energy Level
I haven't gotten that far in the textbook, but I know hybridization can change the energy levels of the orbitals in molecules.
- Sun Nov 18, 2018 3:26 pm
- Forum: Hybridization
- Topic: sp3 hybridization
- Replies: 6
- Views: 54
Re: sp3 hybridization
I believe it should also have an sp3 hybridization.
- Sun Nov 18, 2018 3:23 pm
- Forum: Lewis Structures
- Topic: Polar vs Nonpolar molecules
- Replies: 7
- Views: 82
Re: Polar vs Nonpolar molecules
Like stated above, you can cancel the net dipole moments in order to determine if a molecule is polar or not. However, I think just basing it off the Lewis Structure might not be the best. For me, I like to know the shape of the molecule so I can visualize how the atoms are rearranged and how the di...
- Sun Nov 11, 2018 5:11 pm
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: Dipole
- Replies: 3
- Views: 37
Re: Dipole
A dipole is when a molecule is separated by a partial positive charge and a partial negative charge. For example, H2O has a dipole moment. Oxygen is more electronegative and thus has a negative charge, while the two hydrogen carry a more positive charge. A dipole is quantified by its dipole moment w...
- Sun Nov 11, 2018 5:07 pm
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: Polarizability vs. Polarizing Power
- Replies: 1
- Views: 30
Re: Polarizability vs. Polarizing Power
Polarizing power is the ability for a cation to distort an anion. On the other hand, polarizatibility is the tendency or the likelihood that the anion is becoming polarized.
- Sun Nov 11, 2018 5:03 pm
- Forum: Coordinate Covalent Bonds
- Topic: Coordinate Covalent Bond formation
- Replies: 3
- Views: 36
Re: Coordinate Covalent Bond formation
A coordinate covalent bond is formed when two atoms share a pair of electrons, however those shared electrons come from one atom.
- Wed Oct 31, 2018 10:46 pm
- Forum: Resonance Structures
- Topic: 2C.3 on homework
- Replies: 1
- Views: 71
Re: 2C.3 on homework
I am pretty sure we won't need to memorize all of them right now for the test. I remember Lavelle saying, the more we see them being used, the more we will remember. I wouldn't stress too much about that for the midterm.
- Wed Oct 31, 2018 10:43 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: S-orbital and D-orbital
- Replies: 2
- Views: 74
Re: S-orbital and D-orbital
As the number of orbitals increases, the s and d orbitals become very close in energy with s being slightly lower than d. Therefore, the 4s orbital will fill up first and then the 3d orbital will be filled. However, d becomes favorable when the electron has an uneven amount of electrons. Orbitals li...
- Wed Oct 31, 2018 10:36 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Hw #2.51 6th edition
- Replies: 1
- Views: 49
Re: Hw #2.51 6th edition
For predicting the number of unpaired electrons, you can either write out the electron configuration in order to see how many electrons are left in the valence shell. Or you can locate the element on the periodic table, and see what block it occupies. If you know the block or orbital, you can see it...
- Sat Oct 27, 2018 2:39 pm
- Forum: DeBroglie Equation
- Topic: Homework Question 1B.15
- Replies: 3
- Views: 58
Re: Homework Question 1B.15
Unfortunately, I think the only way to solve this question is by using the mass of the electron because kinetic energy has to do with the mass of the object that is moving at a speed. The equation would then be λ = 2(h*c)/m*v^2 and you would plug in all the numbers to get your value.
- Sat Oct 27, 2018 2:33 pm
- Forum: Ionic & Covalent Bonds
- Topic: Replacement for Modules
- Replies: 7
- Views: 130
Re: Replacement for Modules
I'm not sure if you have taken chemistry or AP Chemistry in high school, but a good resource is the ap books as they supply some of the same information learned in class. I know the ap books break it down and are much easier to comprehend than some sections in this textbook. So for refreshers, you c...
- Sat Oct 27, 2018 2:29 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Valence Electrons
- Replies: 3
- Views: 34
Re: Valence Electrons
Yes, valence electrons are only found in the s and p orbitals. So 2 electrons in the s orbital and 6 in the p orbital add up to the 8 valence electrons that are found in the elements.
- Sun Oct 21, 2018 3:10 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: CH 1 1.55 6TH EDITION
- Replies: 1
- Views: 30
Re: CH 1 1.55 6TH EDITION
For part a), I converted 3600 into meters and then multiplied it to the speed of light. The frequency found was 1.1*10^14 Hz. For part b), I used the equation E=hv, and solved for the E by using Plank's constant and the frequency found in part a. For part c), I used the energy in part b and multipli...
- Sun Oct 21, 2018 3:06 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Diffraction and Spectral Lines
- Replies: 1
- Views: 17
Re: Diffraction and Spectral Lines
I don't think they have a correlation at all. I know diffraction is useful for studying the structure of molecules. The textbook doesn't relate the two, however, they do discuss how this interference relates to the wave-particle duality of electromagnetic radiation. Spectral lines are calculated whe...
- Sun Oct 21, 2018 2:58 pm
- Forum: *Particle in a Box
- Topic: Shape of Wavefunction
- Replies: 2
- Views: 214
Re: Shape of Wavefunction
I know from previous replies, many have stated not to worry about that topic for the midterm or test this Wednesday.
- Sun Oct 14, 2018 2:57 pm
- Forum: Properties of Light
- Topic: Photons
- Replies: 4
- Views: 82
Photons
I understand that a photon must have a high enough energy to remove an electron? However, why can't two photons combine there energy to eject an electron?
- Sun Oct 14, 2018 2:54 pm
- Forum: Properties of Electrons
- Topic: Photoelectric Experiment
- Replies: 9
- Views: 66
Re: Photoelectric Experiment
In order to remove an electron, there has to be a photon and electron interaction. You can have a high intensity, meaning more photons interacting with electrons, however, this does not guarantee that electrons will be emitted. Instead, the photon must have greater energy than the electron in order ...
- Sun Oct 14, 2018 2:45 pm
- Forum: Photoelectric Effect
- Topic: Photoelectric Effect Post Module Questions
- Replies: 2
- Views: 40
Photoelectric Effect Post Module Questions
For one of the questions, it states in order to interpret the results of photoelectric experiments the model of light needs to change from a wave model to a particle model. I understand the experiment and how it works. However, is it wrong to say the light needs to change from a wave model to a phot...
- Wed Oct 03, 2018 9:20 pm
- Forum: Significant Figures
- Topic: Sig Figs
- Replies: 6
- Views: 80
Sig Figs
If a question gives values with three significant figures and an answer is a whole number like 400, would I have to denote the answer with a decimal point like 400.?
- Wed Oct 03, 2018 9:17 pm
- Forum: Limiting Reactant Calculations
- Topic: Two Limiting Reactants
- Replies: 6
- Views: 77
Re: Two Limiting Reactants
You could also have two limiting reactants if there are two different reactions involved in the question.
- Wed Oct 03, 2018 9:10 pm
- Forum: Empirical & Molecular Formulas
- Topic: Empirical Formula
- Replies: 1
- Views: 48
Empirical Formula
When solving for the empirical formula, when do we know when to round up or down? For example, if it's 8.7 moles, should we round to 9 or multiply by a value to reach a whole number?