Search found 102 matches
- Thu Mar 12, 2020 4:46 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Arrhenius Equation
- Replies: 3
- Views: 67
Re: Arrhenius Equation
You can also use the Arrhenius equation to compare a reaction at two different temperatures and determine how a temperature change affects the activation energy or rate constant.
- Thu Mar 12, 2020 4:44 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Slow step of reaction?
- Replies: 5
- Views: 106
Re: Slow step of reaction?
I think if you know the overall rate law that was determined experimentally, then the rate law of the slow step will be the same as the reaction rate law. You also might need to use the pre-equilibrium method if the rate law of the slow step has an intermediate.
- Wed Mar 11, 2020 4:03 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: dilutions and Ecell
- Replies: 16
- Views: 224
Re: dilutions and Ecell
If it is a concentration cell, diluting the side with a lower concentration would increase the concentration difference between the anode and the cathode, causing the cell potential to increase.
- Wed Mar 11, 2020 3:58 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Change in Ecell
- Replies: 5
- Views: 88
Re: Change in Ecell
No, if you increase the mass of the solid it doesn't affect Ecell (I'm pretty sure this was one of the questions on test two).
- Wed Mar 11, 2020 3:47 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Identifying Catalysts and intermediates
- Replies: 4
- Views: 71
Re: Identifying Catalysts and intermediates
A catalyst has to be there for a reaction to begin, whereas an intermediate is formed during one of the elementary steps and then used up in a later step.
- Tue Mar 10, 2020 9:04 pm
- Forum: Student Social/Study Group
- Topic: Review Sessions
- Replies: 4
- Views: 176
Review Sessions
Does anyone know if any of the other final review sessions have posted a worksheet beside Lyndon's?
- Sun Mar 08, 2020 11:42 am
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: order of reactions
- Replies: 7
- Views: 148
Re: order of reactions
First-order tells us that an increase in the concentration of the reactant is directly proportional to the rate, so doubling the reactant will double the rate. Second-order means that doubling the reactant will increase the rate by a factor of four, and zero-order means that the rate does not depend...
- Sun Mar 08, 2020 11:35 am
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: intermediates
- Replies: 5
- Views: 93
Re: intermediates
I'm pretty sure we won't have to figure out or guess the intermediates for a reaction.
- Sun Mar 08, 2020 11:33 am
- Forum: Zero Order Reactions
- Topic: Not used Half life
- Replies: 8
- Views: 513
Re: Not used Half life
I thought that zero-order does have a half-life. In my notes, I have that it's [A]initial / 2k.
- Sun Mar 08, 2020 11:27 am
- Forum: General Rate Laws
- Topic: Rate law
- Replies: 3
- Views: 115
Re: Rate law
I think this could mean when you have multiple reactants and the concentration of each reactant might affect the rate differently.
- Sun Mar 08, 2020 11:25 am
- Forum: General Rate Laws
- Topic: integrated rate laws
- Replies: 7
- Views: 92
Re: integrated rate laws
An integrated rate law represents the rate of a reaction with respect to time, so you can use it to find how quickly a reaction has progressed over a certain amount of time. A rate law only involves the initial rates.
- Sat Feb 29, 2020 8:22 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Anode vs Cathode
- Replies: 5
- Views: 66
Anode vs Cathode
Is there a way to determine from two half-reactions which one will be the anode and which will be the cathode? Is it always that the reaction with a more positive E will be the cathode?
- Sat Feb 29, 2020 8:18 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Equilibrium constant in terms of standard potential
- Replies: 1
- Views: 18
Re: Equilibrium constant in terms of standard potential
When Ecell is positive, then everything on the right side of this equation is positive. Then, to solve for K you take e to the power of nFE/RT, which will give a large positive number.
- Sat Feb 29, 2020 8:16 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Outline of Thermodynamics
- Replies: 3
- Views: 85
Re: Outline of Thermodynamics
Free energy is equal to the amount of energy that is available to do work. I think this means that the value of delta G is the maximum amount of work that a system can do.
- Sat Feb 29, 2020 8:13 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell Potential
- Replies: 3
- Views: 93
Re: Cell Potential
Standard cell potential is the difference in reduction potentials between the cathode and anode when the reaction is occurring at standard conditions (1 M and 1 bar). Cell potential is when the reaction is occurring at conditions other than standard, and it changes when concentration changes, wherea...
- Sat Feb 29, 2020 8:09 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Adding an inert electrode
- Replies: 3
- Views: 58
Re: Adding an inert electrode
You add Pt if there are no solids involved in the reduction or oxidation reactions.
- Sun Feb 23, 2020 11:23 am
- Forum: Balancing Redox Reactions
- Topic: What is Being Reduced?
- Replies: 10
- Views: 126
Re: What is Being Reduced?
I think it's better to be specific and include the charges. You could also write out the half-reactions to show that Fe3+ is gaining one electron and is being reduced.
- Sun Feb 23, 2020 11:21 am
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: test 2 material clarification
- Replies: 10
- Views: 175
Re: test 2 material clarification
I think that will be on the test. It is included in the part of the thermodynamics outline that we covered after the midterm.
- Sun Feb 23, 2020 11:19 am
- Forum: Balancing Redox Reactions
- Topic: Cell Diagrams
- Replies: 6
- Views: 118
Re: Cell Diagrams
The diagram tells us that the elements on the left side of || are involved in oxidation and the elements on the right are involved in reduction. With this information, you can figure out each half-reaction and determine which are reactants and products based on whether electrons are being lost or ga...
- Sun Feb 23, 2020 11:13 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Galvanic Cell emf
- Replies: 3
- Views: 64
Re: Galvanic Cell emf
If G is positive for a galvanic cell, the redox reaction is unfavorable, and therefore electrons would not flow from anode to cathode. In order for a battery to work, G must be negative so that you get a positive voltage and the electron flow from anode to cathode is favorable.
- Sun Feb 23, 2020 11:10 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: platinum
- Replies: 4
- Views: 52
Re: platinum
You can use solid platinum as the electrode if there is no solid conductor in the reaction already. Some reactions occur with both reactants and products being aqueous, so you need to add a solid that can easily conduct electricity and will not interfere with the reaction, such as platinum or carbon...
- Sat Feb 15, 2020 2:13 pm
- Forum: Van't Hoff Equation
- Topic: When to apply the Van't Hoff Equation
- Replies: 5
- Views: 427
Re: When to apply the Van't Hoff Equation
It can be used to compare the equilibrium constants when the reaction takes place at two different temperatures.
- Sat Feb 15, 2020 2:08 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Delta G and spontaneity
- Replies: 4
- Views: 91
Re: Delta G and spontaneity
Yes because a spontaneous reaction means that the reaction is more likely to proceed and more products are likely to form. If a reaction is not spontaneous, the reactants are unlikely to form products, so the reverse reaction is favored.
- Sat Feb 15, 2020 2:05 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Delta U = 0
- Replies: 8
- Views: 213
Re: Delta U = 0
Delta U = 0 for reversible processes, since any work done is replaced by an equal amount of heat (q = -w)
- Sat Feb 15, 2020 2:03 pm
- Forum: Calculating Work of Expansion
- Topic: Isothermal Irreversible
- Replies: 6
- Views: 203
Re: Isothermal Irreversible
I thought that the only way to have an isothermal irreversible expansion is if there is free expansion, meaning the external pressure is 0. Most irreversible expansions involve a temperature change.
- Sat Feb 15, 2020 1:59 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: Boltzmann Equation
- Replies: 10
- Views: 184
Re: Boltzmann Equation
It is used to calculate entropy if you know the number of ways particles can be arranged while still having the same energy (residual entropy).
- Sat Feb 08, 2020 1:51 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: Perfect Crystal
- Replies: 3
- Views: 26
Re: Perfect Crystal
If the system can only be arranged in one way, meaning it only has one possible microstate, then W = 1 (it doesn't matter how many particles are in the system because 1 raised to any power is always 1). Since the natural log of 1 is 0, then the entropy of the system is S = kBln(1) = 0.
- Sat Feb 08, 2020 12:23 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Entropy of transition
- Replies: 8
- Views: 124
Re: Entropy of transition
Adding on to your comment, I think you would need a third component where you calculate q when cooling the substance back to the original temperature. Then, find the change in entropy for cooling and add all three entropy changes to find the total.
- Sat Feb 08, 2020 12:18 pm
- Forum: Phase Changes & Related Calculations
- Topic: General Phase Change Calculations
- Replies: 6
- Views: 55
Re: General Phase Change Calculations
I find it helpful to remember the heating curve graph that Lavelle showed in class. If the reaction is going through a phase change, its temperature stays constant, so it wouldn't make sense to use the q = mC(delta T) since delta T would be 0. Instead, you use the hopefully given delta H value and m...
- Sat Feb 08, 2020 12:09 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Bomb Calorimeter Differences
- Replies: 2
- Views: 31
Re: Bomb Calorimeter Differences
If you're finding q using the equation q = nC(delta T), you would use the value of Cp if the reaction is at constant pressure and the value Cv when at constant volume.
- Sat Feb 08, 2020 12:05 pm
- Forum: Calculating Work of Expansion
- Topic: Constant Volume and Pressure Values
- Replies: 8
- Views: 118
Re: Constant Volume and Pressure Values
The monatomic values are on the constants and equations sheet. But for diatomic, it's not that hard to remember since you just add 1 to each of the ratios. I haven't seen any practice problems where we need to use polyatomic values, though.
- Sat Feb 01, 2020 7:11 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Enthalpies of Formation
- Replies: 1
- Views: 19
Enthalpies of Formation
What is the difference between standard enthalpy of formation and standard reaction enthalpy?
- Sat Feb 01, 2020 7:07 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: reversible vs irreversible expansion
- Replies: 4
- Views: 50
Re: reversible vs irreversible expansion
I think it is also important to know that the graph for an irreversible expansion will be a horizontal line (since pressure is constant), but the graph of a reversible expansion is a curved line (since pressure is changing). This means that the work done by a reversible expansion is greater since it...
- Sat Feb 01, 2020 9:21 am
- Forum: Calculating Work of Expansion
- Topic: 4A.5
- Replies: 1
- Views: 33
Re: 4A.5
For A, use the equation w = -P(delta V), which finds the work done during an irreversible expansion. Then, convert your answer to joules using the conversion of 101.325 J/ 1 L.atm. For part B, since it is a reversible expansion, use the equation w = -nRT ln(V2/V1). This was the formula that came fro...
- Sat Feb 01, 2020 9:14 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Ideal Gases: Heat Capacity
- Replies: 2
- Views: 37
Re: Ideal Gases: Heat Capacity
I think there was a homework problem where we needed to use those ratios, so I'm assuming we should know it.
- Sat Feb 01, 2020 9:10 am
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Work and ideal gas law
- Replies: 4
- Views: 48
Re: Work and ideal gas law
The ideal gas law is PV = nRT, and work is equal to -P(change in V). So, if you know the number of moles and the temperature of a reaction, you can solve for work using the idea that work = -nRT. I think there was an example of this in Friday's lecture.
- Sat Jan 25, 2020 7:36 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Bond Enthalpy Method
- Replies: 5
- Views: 45
Bond Enthalpy Method
Why is using bond enthalpies to calculate H the least accurate method?
- Sat Jan 25, 2020 7:31 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Enthalpy
- Replies: 2
- Views: 31
Re: Enthalpy
In the heating curve graph that Lavelle showed in class, the amount of energy needed for melting is much lower than the energy required for vaporization. This means that heat is absorbed in order to go from a liquid to a vapor, so the vapor would have a higher enthalpy.
- Sat Jan 25, 2020 6:57 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Excluding H2O from Ka and Kb
- Replies: 5
- Views: 60
Re: Excluding H2O from Ka and Kb
When H2O is a solvent it is in so much excess that its concentration doesn't change.
- Sat Jan 25, 2020 8:51 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: state functions
- Replies: 4
- Views: 48
Re: state functions
Some examples of state functions are energy, pressure, and temperature.
- Sat Jan 25, 2020 8:48 am
- Forum: Phase Changes & Related Calculations
- Topic: Proton transfer in water
- Replies: 3
- Views: 32
Re: Proton transfer in water
For a proton transfer between water molecules, the reactants would be 2 H2O molecules and the products would be H3O+ and OH-. Then when you write Ka, you exclude H2O and its just Ka = [H3O+] [OH-], which equals 10^-14 (Kw).
- Sat Jan 18, 2020 8:14 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Change in Pressure
- Replies: 5
- Views: 53
Re: Change in Pressure
When the pressure is increased by decreasing volume, the reaction will move in whichever direction will reduce the pressure. This means that it will move towards the side with fewer moles (so fewer molecules), which causes the pressure to decrease.
- Sat Jan 18, 2020 8:09 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: ice table/quadratic
- Replies: 6
- Views: 57
Re: ice table/quadratic
The homework problem 5I.25 is a good example of this type of situation. In this problem, there are initial concentrations of both reactants and products present, and you end up getting a quadratic equation where x is two positive values.
- Sat Jan 18, 2020 8:02 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Temperature
- Replies: 2
- Views: 27
Re: Temperature
An endothermic reaction is one that requires heat to form products. For example, the reaction N2 -> 2N is endothermic because it requires energy to break the N-N bonds and form product. When an endothermic reaction is heated, its equilibrium constant increases, since more heat is absorbed by the rea...
- Sat Jan 18, 2020 7:54 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: K comparison
- Replies: 4
- Views: 66
Re: K comparison
For ICE tables, you can simplify the calculation if K is less than 10^-3.
- Sat Jan 18, 2020 7:52 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: K and Kc
- Replies: 3
- Views: 40
Re: K and Kc
I think K and Kc mean the same thing, but Kc is just more specific because it tells us that we're dealing with concentrations.
- Sat Jan 11, 2020 11:09 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: ICE Table Calculations
- Replies: 4
- Views: 32
ICE Table Calculations
When solving for x in an ICE table, how do we know when to use the quadratic equation and when to assume that x is very small and simplify the expression.
- Sat Jan 11, 2020 11:07 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Partial Pressure
- Replies: 3
- Views: 46
Partial Pressure
What are partial pressures? I understand that we use the partial pressures of R and P to calculate Kp, but what do the values actually represent?
- Sat Jan 11, 2020 11:04 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: ICE Table Ratios
- Replies: 7
- Views: 82
Re: ICE Table Ratios
You'll get the same answer in the end, but I would choose the ratio that makes solving for x the simplest.
- Sat Jan 11, 2020 11:01 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: ICE Tables
- Replies: 5
- Views: 59
Re: ICE Tables
For ICE tables, only include the reactants and products that you would use to calculate K.
- Sat Jan 11, 2020 10:51 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: K vs. Q
- Replies: 10
- Views: 110
Re: K vs. Q
K is a fixed ratio and will therefore always be the same number (for each reaction at a certain temperature), but Q is the P/R ratio calculated at any point in the reaction. Q can be used to figure out whether a reaction is at equilibrium, and if not, which direction the reaction is moving.
- Wed Dec 04, 2019 8:59 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Shape of Coordination Compounds
- Replies: 1
- Views: 47
Shape of Coordination Compounds
Is there a way to tell whether a coordination compound will be tetrahedral or square planar?
- Wed Dec 04, 2019 8:52 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: K constant and pK value
- Replies: 3
- Views: 46
Re: K constant and pK value
I'm pretty sure we aren't going to do actual calculations with Ka until 14B. What does Kw represent, though? I don't remember learning that
- Wed Dec 04, 2019 8:47 pm
- Forum: Einstein Equation
- Topic: units for energy
- Replies: 2
- Views: 166
Re: units for energy
The unit is J, but in the E=hv equation you are finding the energy of a photon, so technically this value means the amount of energy per photon. I think you can just write J in your answer though.
- Wed Dec 04, 2019 8:45 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Chelate
- Replies: 5
- Views: 139
Re: Chelate
Chelates form when a ligand can bind to a metal atom at more than one site, creating a ring of atoms.
- Wed Dec 04, 2019 8:42 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Coordinate Compounds
- Replies: 3
- Views: 62
Re: Coordinate Compounds
I think it's important to know the charges and names of the different ligands to help with naming coordination compounds.
- Fri Nov 29, 2019 8:40 pm
- Forum: General Science Questions
- Topic: hydrogen vs hydronium
- Replies: 5
- Views: 90
Re: hydrogen vs hydronium
When an acid is dissolved in water, it loses a proton (hydrogen ion) and transfers it to water, forming a hydronium ion (H30+). I think H30+ is more specific and it is what you would use when writing a chemical equation.
- Fri Nov 29, 2019 8:32 pm
- Forum: Bronsted Acids & Bases
- Topic: Acids and Bases
- Replies: 3
- Views: 42
Re: Acids and Bases
For Lewis acids and bases, it would be helpful to draw the structures to see whether the molecule has a lone pair that it can donate.
- Fri Nov 29, 2019 8:28 pm
- Forum: Naming
- Topic: Common Names
- Replies: 2
- Views: 72
Re: Common Names
I've never heard of ferricyanide, but I think it's safer to just follow the naming system we learned in class
- Fri Nov 29, 2019 8:24 pm
- Forum: Naming
- Topic: Polydentate Ligands
- Replies: 3
- Views: 132
Re: Polydentate Ligands
In the textbook, it says that the ligands ethylenediamine (en) and oxalato are bidentate, diethylenetriamine (dien) is tridentate, and (edta) is hexadentate. I'm not sure if these will always be polydentate though, or if it is only in certain cases.
- Fri Nov 29, 2019 8:16 pm
- Forum: Naming
- Topic: Coordination Compounds on the Final
- Replies: 4
- Views: 89
Re: Coordination Compounds on the Final
Based on the homework, I'm guessing it will mostly just be naming.
- Fri Nov 22, 2019 9:23 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: Homework 3F1
- Replies: 4
- Views: 120
Re: Homework 3F1
I had trouble with part c at first, but H2SeO4 will also have hydrogen bonding. This is because its lewis structure has the four oxygens bonded to the central Se atom, and the two H atoms are bonded to two of the hydrogens. Any time an H atom is bonded to an O, F or N atom, there will be hydrogen bo...
- Fri Nov 22, 2019 9:19 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: 2E.5
- Replies: 5
- Views: 117
Re: 2E.5
A molecule that has three regions of electron density will have a bent shape if one of the regions is a lone pair and the other two are bonding pairs. If all three regions are bonded atoms, then the shape is trigonal planar. In this problem, the molecule has a bent shape because Cl has a lone pair a...
- Fri Nov 22, 2019 9:14 am
- Forum: Dipole Moments
- Topic: Determining intermolecular forces
- Replies: 4
- Views: 119
Re: Determining intermolecular forces
There are also dipole-induced dipole forces, which occur between a polar and a nonpolar molecule.
- Fri Nov 22, 2019 9:09 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: Hydrogen Bonding Atoms
- Replies: 6
- Views: 87
Re: Hydrogen Bonding Atoms
If the intermolecular forces are between two of the same molecule, each molecule must have a hydrogen atom attached to an F, O, or N atom.
- Fri Nov 22, 2019 8:43 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Lone Pairs
- Replies: 8
- Views: 201
Re: Lone Pairs
Lone pairs are more likely to be found in equatorial positions because they experience less repulsion.
- Sat Nov 16, 2019 9:45 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: Types of Forces
- Replies: 2
- Views: 64
Types of Forces
Is it possible for a molecule to have the potential to form both dipole-induced dipole and dipole-dipole bonds?
- Sat Nov 16, 2019 9:42 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bond Angles
- Replies: 9
- Views: 147
Bond Angles
How do we predict the bond angles of a molecule?
- Sat Nov 16, 2019 9:38 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Repulsion
- Replies: 1
- Views: 46
Repulsion
Does a greater repulsion strength between bonding pairs result in a larger bond angle? How would we determine which bonding pairs have a greater repulsion when looking at a molecule with multiple bonds?
- Fri Nov 15, 2019 6:58 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-induced dipole bond
- Replies: 5
- Views: 99
Re: Dipole-induced dipole bond
Why is the London Dispersion Force found in every bond? London dispersion forces happen in all atoms because they all have the potential to form instantaneous dipole moments, which is when the electron density is not evenly distributed around the nucleus and is more concentrated in one area. This c...
- Fri Nov 15, 2019 6:48 pm
- Forum: Dipole Moments
- Topic: CH
- Replies: 3
- Views: 66
Re: CH
There is not a dipole moment for CH bonds because the electronegativity difference between C and H is very small, so the bond is considered nonpolar.
- Sun Nov 10, 2019 10:28 am
- Forum: Bond Lengths & Energies
- Topic: Strength of Interactions
- Replies: 3
- Views: 49
Strength of Interactions
What causes certain interactions to form liquids or solids?
- Sun Nov 10, 2019 10:23 am
- Forum: Bond Lengths & Energies
- Topic: Hydrogen Bonding
- Replies: 3
- Views: 59
Hydrogen Bonding
Why are the attractive forces of hydrogen bonds always -20 kJ/mol?
- Sun Nov 10, 2019 10:20 am
- Forum: Dipole Moments
- Topic: Interactions
- Replies: 4
- Views: 60
Interactions
Is there a difference between dispersion and london forces?
- Sun Nov 10, 2019 10:18 am
- Forum: Bond Lengths & Energies
- Topic: Ionic/covalent Character
- Replies: 3
- Views: 70
Ionic/covalent Character
What makes some molecules such as salts more soluble in water?
- Sun Nov 10, 2019 10:12 am
- Forum: Bond Lengths & Energies
- Topic: Bond Lengths
- Replies: 3
- Views: 57
Re: Bond Lengths
Triple bonds have the largest number of shared electrons and the greatest attraction between atoms, so they are harder to break and shorter in length. Single bonds are the largest in length, so they are the weakest.
- Sat Nov 02, 2019 2:00 pm
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Polarizable vs Polarizing
- Replies: 6
- Views: 110
Polarizable vs Polarizing
What is the difference between "highly polarizable" and "high polarizing power"? They both result in an ionic bond with a greater covalent character.
- Sat Nov 02, 2019 1:58 pm
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Polarizing Power
- Replies: 3
- Views: 62
Polarizing Power
Does polarizing power follow any trends on the periodic table?
- Sat Nov 02, 2019 1:56 pm
- Forum: Dipole Moments
- Topic: Interactions between ions and molecules
- Replies: 1
- Views: 37
Interactions between ions and molecules
At the end of the lecture on Friday Lavelle talked about the interactions that give rise to attractive forces (ion-ion, ion-dipole, etc.) but why are the kJ/mol always negative?
- Sat Nov 02, 2019 1:52 pm
- Forum: Dipole Moments
- Topic: Induced Dipole
- Replies: 5
- Views: 104
Induced Dipole
What causes an induced dipole?
- Sat Nov 02, 2019 1:40 pm
- Forum: Trends in The Periodic Table
- Topic: Trends
- Replies: 2
- Views: 49
Re: Trends
Ionization energy is the minimum energy required to remove an electron, electron affinity is an atom's likelihood of gaining an electron, and electronegativity is how tightly an atom holds onto their electrons. All three trends increase as you go up and to the right on the periodic table.
- Wed Oct 23, 2019 9:08 pm
- Forum: Ionic & Covalent Bonds
- Topic: What's the difference between valence electrons and the valence of an atom?
- Replies: 3
- Views: 110
Re: What's the difference between valence electrons and the valence of an atom?
The valence of an atom means the number of covalent bonds it has, and valence electrons are the electrons in the outer shell.
- Wed Oct 23, 2019 9:06 pm
- Forum: Resonance Structures
- Topic: bond lengths
- Replies: 4
- Views: 68
Re: bond lengths
I think this happens because the double bond can occur at three different locations (remember the three different structure diagrams for NO3 that he showed in class), so this bond length of 1.24 A is kind of like an average or combination of the different structures.
- Wed Oct 23, 2019 9:00 pm
- Forum: Photoelectric Effect
- Topic: Hw Help 1B.15
- Replies: 2
- Views: 55
Re: Hw Help 1B.15
I had a hard time with this problem too. For part A, we can use the De Broglie equation (wavelength = h/p) since we know the mass and velocity of the electron. For B, they give the frequency required to remove one electron, so you can use that in the equation E = h x frequency. This gives the energy...
- Wed Oct 23, 2019 8:40 pm
- Forum: Trends in The Periodic Table
- Topic: Effective Nuclear Charge
- Replies: 5
- Views: 96
Effective Nuclear Charge
What does the effective nuclear charge describe about an atom? Do certain elements tend to have a higher or lower effective nuclear charge?
- Wed Oct 23, 2019 8:29 pm
- Forum: Trends in The Periodic Table
- Topic: Aufbau Principle
- Replies: 11
- Views: 180
Re: Aufbau Principle
This means that electrons always fill up the lowest energy orbitals first before occupying the higher orbitals. So when we write electron configurations, we start with 1s, then 2s, etc.
- Sat Oct 19, 2019 2:57 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Spin Magnetic Quantum Number
- Replies: 1
- Views: 47
Spin Magnetic Quantum Number
How are we supposed to know what the spin state of an electron is? For all of the homework problems I've done so far they have only been asking about the first three quantum numbers, but I don't understand how we would know what the spin state is unless it is given.
- Sat Oct 19, 2019 2:51 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Exceptions (Cr and Cu)
- Replies: 2
- Views: 47
Exceptions (Cr and Cu)
Why do certain elements (like Cr and Cu) not follow the same electron configuration pattern as most elements?
- Sat Oct 19, 2019 2:48 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Writing Electron Configurations
- Replies: 7
- Views: 83
Writing Electron Configurations
How do we know when to include x, y, and z when writing electron configurations? For example, nitrogen is 1s^2, 2s^2, 2px^1, 2py^1, 2pz^1
- Sat Oct 19, 2019 2:42 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Paired Electrons
- Replies: 5
- Views: 66
Paired Electrons
I'm having a hard time visualizing the electron configurations that we learned about on Friday. What does it mean when two electrons are paired? How is this different than two electrons being parallel?
- Sat Oct 19, 2019 2:29 pm
- Forum: Photoelectric Effect
- Topic: One photon one atom interaction
- Replies: 14
- Views: 239
Re: One photon one atom interaction
I don't think that increasing the frequency would increase the number of electrons ejected, since the number of electrons ejected still depends on the number of photons. But, if the energy of light is already greater than the minimum energy needed to eject an electron, then increasing the frequency ...
- Sun Oct 13, 2019 3:11 pm
- Forum: Properties of Light
- Topic: Photon vs Wave Model
- Replies: 5
- Views: 79
Photon vs Wave Model
With the photon model, energy is proportional to frequency, whereas with the wave model, energy is proportional to intensity. What is the difference between frequency and intensity?
- Sun Oct 13, 2019 3:08 pm
- Forum: Einstein Equation
- Topic: Equations and their purpose
- Replies: 3
- Views: 75
Re: Equations and their purpose
The De Broglie equation (wavelength = h/p) can be used to find the wavelength of any moving particle with a momentum. The equation E(n) = -[hR/n^2] can be used to find the energy of an electron at a certain energy level (n), and then you can calculate the change in energy if you know the initial and...
- Sun Oct 13, 2019 3:00 pm
- Forum: Properties of Light
- Topic: speed of light
- Replies: 10
- Views: 111
Re: speed of light
I think for most of the problems we'll be doing this quarter we can just assume that C = the speed of light in a vacuum.
- Sun Oct 13, 2019 2:49 pm
- Forum: Properties of Light
- Topic: Photon Model
- Replies: 3
- Views: 53
Photon Model
I'm having a hard time conceptualizing what a photon is. Lavelle described them as "packets" of energy, but they also travel in waves, and each photon interacts with one electron?
- Sun Oct 13, 2019 2:35 pm
- Forum: Photoelectric Effect
- Topic: Work Function
- Replies: 2
- Views: 51
Work Function
In the lecture last week Lavelle explained that to find the kinetic energy of an ejected electron, you subtract the work function from the energy of a photon (E=hv). What does the work function represent? Is it something that we need to know how to find or will it always be a given number in problems?
- Sun Oct 06, 2019 11:45 am
- Forum: Balancing Chemical Reactions
- Topic: Net Ionic Equations, HW problem M9
- Replies: 1
- Views: 83
Net Ionic Equations, HW problem M9
In problem M9, it asks to find the net ionic equation for when copper (II) nitrate reacts with sodium hydroxide to produce a precipitate of light blue copper (II) hydroxide. I understand what a net ionic equation is, but I wasn't able to figure out how to get the answer shown in the solutions book. ...
- Sun Oct 06, 2019 11:38 am
- Forum: Limiting Reactant Calculations
- Topic: Limiting Reactant Tips
- Replies: 4
- Views: 110
Re: Limiting Reactant Tips
Once you convert each of the reactants to moles, you can just choose one of the reactants and use the mole ratio from the balanced equation to find the amount of moles that are required of the other reactant. If the number of moles calculated of the second reactant is less than the amount given in t...
- Sun Oct 06, 2019 11:28 am
- Forum: Molarity, Solutions, Dilutions
- Topic: HW problem G25
- Replies: 1
- Views: 92
HW problem G25
I feel like I understand the concept of molarity and dilutions, but problem G25 threw me off because the solution is diluted by doubling the volume 90 times. How would we go about solving this problem and finding the number of molecules in the final solution?
- Sun Oct 06, 2019 11:23 am
- Forum: Empirical & Molecular Formulas
- Topic: Compound Names, HW problem G17
- Replies: 2
- Views: 83
Compound Names, HW problem G17
What does it mean when compounds have water molecules added to them? For example, in G17 A it asks for the mass of CuSO4 needed for a dilution, but in part B it asks for the mass of CuSO4*5H2O. What is the difference between these two compounds? Also, if we're finding the molar mass of CuSO4*5H2O, d...