Search found 67 matches
- Sat Mar 16, 2019 11:04 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Concentration cells Ecell
- Replies: 1
- Views: 227
Re: Concentration cells Ecell
Yes. For concentration cells, the Enot is always zero.
- Sat Mar 16, 2019 10:49 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Concentration Cells
- Replies: 1
- Views: 275
Re: Concentration Cells
In concentration cells there is no need to identify which side is oxidized or reduced. Just realize that the one with the smaller concentration is always the product and the one with the higher concentration is the reactant.
- Sat Mar 16, 2019 10:24 am
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Activated structure [ENDORSED]
- Replies: 2
- Views: 308
Re: Activated structure [ENDORSED]
Dr. Lavelle said we don't need to know how to draw structures for 14B.
- Sun Mar 10, 2019 11:00 pm
- Forum: First Order Reactions
- Topic: reaction orders
- Replies: 3
- Views: 374
Re: reaction orders
Yes. There is a possibility in which the order can be any sign and any fraction.
- Sat Mar 09, 2019 9:51 pm
- Forum: Second Order Reactions
- Topic: rate constant k
- Replies: 3
- Views: 431
Re: rate constant k
Rate constants are never negative in any reactions. The value of k will always be positive.
- Sat Mar 09, 2019 3:54 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: negative and k
- Replies: 3
- Views: 437
Re: negative and k
The "k" value can never be negative. For a first order reaction, the slope=-k. Since the slope is negative, k is the opposite sign of what ever the slope is.
- Sun Mar 03, 2019 11:54 pm
- Forum: Van't Hoff Equation
- Topic: Sample problem
- Replies: 2
- Views: 572
Re: Sample problem
It is useful in problems to fine K at a different temperature if delta H is known.
- Sun Mar 03, 2019 11:52 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Class on 2/27 and 3/1
- Replies: 2
- Views: 326
Re: Class on 2/27 and 3/1
Last Wednesday we finished electrochemistry and began Kinetics.
- Sun Mar 03, 2019 2:32 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Molecularity
- Replies: 1
- Views: 255
Re: Molecularity
The number of reactants ultimately determines molecularity.
For example:
A-->products is unimolecular
A+A---> products is bimolecular
A+B--->products is also bimolecular
A+B+B---> products is termolecular
A+B+C----> products is also termolecular
For example:
A-->products is unimolecular
A+A---> products is bimolecular
A+B--->products is also bimolecular
A+B+B---> products is termolecular
A+B+C----> products is also termolecular
- Sun Mar 03, 2019 1:31 pm
- Forum: First Order Reactions
- Topic: Possiility
- Replies: 2
- Views: 328
Re: Possiility
Yes, it is possible to have all reactants be in first order.
- Sun Feb 24, 2019 1:51 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: cell potential
- Replies: 2
- Views: 285
Re: cell potential
We need to know how to calculate standard reduction potentials of cells from given reactions.
- Sat Feb 23, 2019 11:10 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Finding n in Delta G = -nFE
- Replies: 3
- Views: 627
Re: Finding n in Delta G = -nFE
You find n by finding the number of moles of electrons transferred in a reaction.
- Fri Feb 22, 2019 10:27 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Spontaneity
- Replies: 6
- Views: 712
Re: Spontaneity
When delta G is negative, the forward reaction is spontaneous and the products are more stable.
- Thu Feb 21, 2019 11:46 pm
- Forum: Balancing Redox Reactions
- Topic: Balancing / Skeletal Equations
- Replies: 4
- Views: 622
Re: Balancing / Skeletal Equations
We sometimes add H2O or H+ to balance redox reactions to ensure to correct amount of oxygens and hydrogens are balanced on each side.
- Sun Feb 17, 2019 1:49 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: spontaneity
- Replies: 2
- Views: 281
Re: spontaneity
When reactions are spontaneous, they do not need anything extra to occur. Therefore, these reactions will naturally form products.
- Sun Feb 17, 2019 1:38 pm
- Forum: Van't Hoff Equation
- Topic: Different Constants of Eqn
- Replies: 3
- Views: 400
Re: Different Constants of Eqn
Yes, we need a constant temperature to use that equation.
- Sat Feb 16, 2019 2:47 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Homework question 9.55
- Replies: 1
- Views: 250
Re: Homework question 9.55
The default temperature when dealing with standard energy is usually 25 degrees Celsius unless otherwise noted.
- Sun Feb 10, 2019 9:41 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: DeltaU=q+w
- Replies: 5
- Views: 500
Re: DeltaU=q+w
q and w inherently denote change because it is a transfer of energy.
- Sun Feb 10, 2019 12:21 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Units
- Replies: 6
- Views: 994
Re: Units
There are no units for Keq or Kc or Kp.
- Sat Feb 09, 2019 5:02 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Spontaneity
- Replies: 1
- Views: 145
Re: Spontaneity
Phase changes can be spontaneous or non spontaneous.
- Sun Feb 03, 2019 10:52 pm
- Forum: Phase Changes & Related Calculations
- Topic: Heating Curve
- Replies: 4
- Views: 425
Heating Curve
I had trouble understanding why steam creates a more severe burn then hot water. Can someone explain this concept again please?
- Sat Feb 02, 2019 9:48 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Test Question
- Replies: 4
- Views: 484
Re: Test Question
You would usually use Kp when dealing with gases. However, if the question explicitly states find the Kc, then just use Kc when doing calculations.
- Thu Jan 31, 2019 9:55 pm
- Forum: Calculating Work of Expansion
- Topic: Equations for w
- Replies: 5
- Views: 496
Re: Equations for w
Dr. Lavelle was basically showing us the proof behind the work equation which is why he got the integral.
- Sat Jan 26, 2019 5:22 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: method 1
- Replies: 3
- Views: 328
Re: method 1
Yes. The 2NO's cancel each other which is why NO is not in the final reaction.
- Sat Jan 26, 2019 5:19 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: method 2
- Replies: 2
- Views: 280
Re: method 2
You have it flipped. It requires energy to break the bonds on the reactant side, and it releases energy when bonds are formed on the product side.
- Wed Jan 23, 2019 9:16 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Kw - applies to solutions other than 100% water?
- Replies: 3
- Views: 338
Re: Kw - applies to solutions other than 100% water?
The question implies that it is about water since it has hydroxide and hydronium ion.
- Tue Jan 22, 2019 6:18 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Salts
- Replies: 4
- Views: 502
Re: Salts
A salt has a anion and cation. For example, NaF is a salt since Na+ is a cation and F- is an anion.
- Sun Jan 20, 2019 6:10 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Ionization and deprotonation
- Replies: 3
- Views: 130
Re: Ionization and deprotonation
Yes. The two terms mean the exact same thing.
- Wed Jan 16, 2019 9:54 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Le Chatelier's Principle
- Replies: 4
- Views: 449
Re: Le Chatelier's Principle
Without adding more reactants, you would have to decrease the amount of products (NH3) in order to yield more products.
- Wed Jan 16, 2019 4:03 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Temperature and Equilibrium
- Replies: 3
- Views: 370
Re: Temperature and Equilibrium
Because endothermic reactions require heat in the reactants, increasing the temperature will result in the reaction sitting to the products in order to relieve the stress added to reaction. The same goes for exothermic reactions as the reaction will lay to the reactants if temperature is increased.
- Wed Jan 16, 2019 3:59 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Pure Solids and Pure Liquids
- Replies: 4
- Views: 471
Re: Pure Solids and Pure Liquids
The equilibrium constant is not affect by pure liquids or solids. Only gases and aqueous solutions affect equilibrium.
- Wed Jan 16, 2019 12:04 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Test topics for next week
- Replies: 3
- Views: 355
Re: Test topics for next week
Test 1 will cover chemical equilibrium and most of acid/base.
- Sat Jan 12, 2019 11:32 pm
- Forum: Ideal Gases
- Topic: Homework Week 2
- Replies: 10
- Views: 1048
Re: Homework Week 2
Yes. From now on the homework is due in discussion every week.
- Fri Jan 11, 2019 9:36 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Effect of Pressure
- Replies: 3
- Views: 210
Re: Effect of Pressure
The information you googled was briefly mentioned in class, but Dr. Lavelle made it clear that this is only true if the pressure changes by also changing the volume. If the pressure changes by inserting an inert gas, then there is no equilibrium shift.
- Fri Jan 11, 2019 5:22 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: ICE
- Replies: 2
- Views: 214
Re: ICE
I-initial concentration
C-change
E-equilibrium concentration
C-change
E-equilibrium concentration
- Thu Jan 10, 2019 11:44 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: 5G.11 b
- Replies: 3
- Views: 291
Re: 5G.11 b
The main rule is that liquids and solids are not included in the equilibrium constant expression. Aqueous solutions and gases are included.
- Thu Dec 06, 2018 10:56 am
- Forum: Conjugate Acids & Bases
- Topic: Inverse Proportional
- Replies: 2
- Views: 327
Re: Inverse Proportional
Yes, a weak acid has a strong conjugate base. And a strong base has a weak conjugate acid.
- Thu Dec 06, 2018 10:54 am
- Forum: Calculating the pH of Salt Solutions
- Topic: Calculating pH of Acid/Base
- Replies: 1
- Views: 409
Re: Calculating pH of Acid/Base
Lavelle said we do not need to worry about those specific calculations because that is more 14B. All we need to know is the regular pH calculation of an acid or base based on its concentration.
- Tue Dec 04, 2018 8:01 pm
- Forum: Acidity & Basicity Constants and The Conjugate Seesaw
- Topic: K
- Replies: 3
- Views: 429
Re: K
K means constant.
- Thu Nov 29, 2018 11:16 am
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: coordination sphere
- Replies: 1
- Views: 69
Re: coordination sphere
A coordinate sphere is the area in a transition metal complex where the ligands are directly attached to the central atom.
- Tue Nov 27, 2018 9:06 pm
- Forum: Lewis Structures
- Topic: 3.71 6th edition
- Replies: 1
- Views: 118
Re: 3.71 6th edition
You will need to calculate formal charge to see which one is favorable.
- Tue Nov 27, 2018 4:31 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Sigma and Pi bonds
- Replies: 2
- Views: 317
Re: Sigma and Pi bonds
A sigma bond has two orbitals that interact end to end to form the bond. Sigma bonds allow rotation of atoms. A pi bond has two orbitals that overlap side to side to form the bond. Pi bonds do not allow the atoms to rotate. When two atoms are bound by more than one covalent bond, the additional orbi...
- Sat Nov 24, 2018 10:14 am
- Forum: Resonance Structures
- Topic: Resonance in VSEPR Theory
- Replies: 1
- Views: 1165
Re: Resonance in VSEPR Theory
Resonance does occur in vsepr structures. However, resonance does not change the name or structure of the molecule.
- Sat Nov 24, 2018 10:12 am
- Forum: Hybridization
- Topic: hybridization problems
- Replies: 4
- Views: 423
Re: hybridization problems
To find the hybridization of an atom in a molecule, count the number of regions of electron density. If there are two regions, then the hybridization is sp. If three, then it is sp2. If four, then it is sp3. If there are five regions, then it is sp3d.
- Sat Nov 24, 2018 10:09 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: double and triple bonds
- Replies: 10
- Views: 1138
Re: double and triple bonds
Double and triple bonds are still only one region of electron density; therefore, it does not affect the naming of the molecule or the vsepr structure.
- Fri Nov 23, 2018 11:33 am
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: Distinctions between intermolecular forces
- Replies: 2
- Views: 263
Re: Distinctions between intermolecular forces
Those three forces are used interchangeably.
- Thu Nov 15, 2018 8:56 pm
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: 6th edition 4.31
- Replies: 1
- Views: 276
Re: 6th edition 4.31
sp has two electron density groups which is a linear orientation. sp2 has three electron density groups which is a trigonal planar orientation.
- Wed Nov 14, 2018 5:46 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Electrons and VSEPR
- Replies: 4
- Views: 420
Re: Electrons and VSEPR
Lone pair electrons do affect the shape of molecules. They also slightly decrease the angle of the atoms.
- Wed Nov 14, 2018 4:26 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Dipole moments and VESPR
- Replies: 3
- Views: 355
Re: Dipole moments and VESPR
Dipole moments aren't directly related to VSEPR theory, but they will determine whether a molecule is polar or nonpolar.
- Wed Nov 07, 2018 4:32 pm
- Forum: Dipole Moments
- Topic: dispersion forces vs. london forces
- Replies: 2
- Views: 298
Re: dispersion forces vs. london forces
They are the same type of attractive forces. In other words, those terms can be used interchangeably.
- Wed Nov 07, 2018 4:31 pm
- Forum: Bond Lengths & Energies
- Topic: bond lengths and strengths
- Replies: 9
- Views: 967
Re: bond lengths and strengths
Single bonds are the weakest because they are the longest. Double and triple bonds are stronger because they are smaller and held tighter to the atoms.
- Wed Nov 07, 2018 4:29 pm
- Forum: Octet Exceptions
- Topic: List of octect exceptions
- Replies: 6
- Views: 698
Re: List of octect exceptions
The first four elements (H, He, Li, Be) are exceptions along with radicals and elements in the third period and below.
- Fri Nov 02, 2018 10:18 pm
- Forum: Ionic & Covalent Bonds
- Topic: Ionic and Covalent bonds with covalent/ionic characteristics
- Replies: 3
- Views: 336
Re: Ionic and Covalent bonds with covalent/ionic characteristics
In the case of NaCl, the cation Na+ exerts an electrostatic attraction on the electrons surroundings the anion Cl-. Therefore, the anion's electrons are pulled into the bonding region which creates a shared region of electrons between the bond of NaCl. As a result, this salt has some covalent charac...
- Wed Oct 31, 2018 11:49 pm
- Forum: Ionic & Covalent Bonds
- Topic: Multi-Electron Atom
- Replies: 3
- Views: 431
Re: Multi-Electron Atom
This cannot be applied to a hydrogen atom because hydrogen is not a multi electron atom. In other words, it must have more than one electron.
- Wed Oct 31, 2018 11:42 pm
- Forum: Resonance Structures
- Topic: Radicals and "damaging"
- Replies: 5
- Views: 411
Re: Radicals and "damaging"
Yes. This is because radicals only have one free electron instead of an electron pair.
- Fri Oct 26, 2018 10:55 pm
- Forum: Trends in The Periodic Table
- Topic: Ionization Energy and Electron Affinity
- Replies: 9
- Views: 1878
Re: Ionization Energy and Electron Affinity
Ionization energy is the amount of energy needed to remove an electron from an atom. Atoms that form cations have lower IE because they want to give away their electrons, which requires less energy. Electron affinity is the energy released when an electron is added to an atom. In simple terms, atoms...
- Thu Oct 25, 2018 9:05 pm
- Forum: Trends in The Periodic Table
- Topic: Electron Affinity Trend
- Replies: 9
- Views: 1138
Re: Electron Affinity Trend
The elements on the top right of the periodic table have a negative (-) charge, which means they really want one electron to be neutral. This means they also have a high electron affinity.
- Wed Oct 24, 2018 9:28 pm
- Forum: Trends in The Periodic Table
- Topic: Sizes of ions and neutral atoms
- Replies: 4
- Views: 564
Re: Sizes of ions and neutral atoms
Since anions gain electrons while maintaining the same number of protons, the electron cloud enlarges and there is more electron-electron repulsion.
- Sat Oct 20, 2018 10:51 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: HW: 2.13
- Replies: 1
- Views: 101
Re: HW: 2.13
We do not need to know how to depict/draw the orbitals and their orientations. It is just too complicated to draw free hand.
- Sat Oct 20, 2018 10:48 pm
- Forum: *Shrodinger Equation
- Topic: Book Example 1.8:
- Replies: 4
- Views: 476
Re: Book Example 1.8:
Dr. Lavelle said that we do not need to know how to do any calculations with Schrodinger's Equation. He just wants us to have a conceptual idea of the wave model. Calculations won't be on the test.
- Wed Oct 17, 2018 8:43 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Heisenberg Uncertainty Equation
- Replies: 3
- Views: 298
Re: Heisenberg Uncertainty Equation
It really just depends on what the question is asking for. If it gives you the momentum (p), then solve for the uncertainty in position (x). And visa versa.
- Thu Oct 11, 2018 11:31 pm
- Forum: Properties of Electrons
- Topic: Quantum World
- Replies: 6
- Views: 560
Re: Quantum World
Correct. Frequency and wavelength are inversely proportional. As one increases, the other decreases.
- Thu Oct 11, 2018 4:16 pm
- Forum: Einstein Equation
- Topic: Question 9; 6th edition
- Replies: 3
- Views: 380
Re: Question 9; 6th edition
The standard units for frequency are Hertz (Hz). Also the standard units for wavelength is meters. You always want to convert the units to this standard when using them for calculations.
- Wed Oct 10, 2018 9:51 pm
- Forum: Properties of Electrons
- Topic: Bohr frequency condition equation
- Replies: 2
- Views: 723
Re: Bohr frequency condition equation
When an electron goes from a high energy level and drops to a lower energy level, the difference in energy (ΔE) is given off as a photon.
- Thu Oct 04, 2018 11:47 pm
- Forum: SI Units, Unit Conversions
- Topic: 6th Edition E27, First Part
- Replies: 5
- Views: 486
Re: 6th Edition E27, First Part
All you do is divide 1 by Avogadro's number. The calculation should looks like this: 1/(6.02 x 10^23).
- Thu Oct 04, 2018 11:14 am
- Forum: Empirical & Molecular Formulas
- Topic: Molar mass and molecular weight
- Replies: 3
- Views: 497
Re: Molar mass and molecular weight
Just to clarify, the molar mass measures the weight of 6.02 x 10^23 particles of a substance.
- Thu Oct 04, 2018 10:52 am
- Forum: Molarity, Solutions, Dilutions
- Topic: measuring mols vs grams in dilutions
- Replies: 2
- Views: 130
Re: measuring mols vs grams in dilutions
To find the mols in a molarity problem, you can multiply the concentration by the number of liters. Then you can convert to number of mols to grams.