## Search found 76 matches

Thu Mar 14, 2019 11:05 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Catalysts in Rate Law
Replies: 5
Views: 132

### Re: Catalysts in Rate Law

Catalysts can be included in the rate law, just intermediates cannot.
Thu Mar 14, 2019 11:04 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Activation Energies
Replies: 2
Views: 88

### Re: Activation Energies

If the activation energy for the forward reaction is greater than the reverse reaction then the forward reaction is endothermic because more energy is required in the forward direction. The opposite is true for exothermic reactions: a lower Ea in the forward direction indicates an exothermic reactio...
Mon Mar 11, 2019 9:42 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Ka2 in Acids
Replies: 2
Views: 113

### Re: Ka2 in Acids

Ka2 is considered negligible when it is significantly smaller than Ka1. Unfortunately, I don't there is an actual cut off so I don't think you have to worry too much about.
Mon Mar 11, 2019 9:41 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Calculating heat
Replies: 1
Views: 269

### Re: Calculating heat

This question is asking you to find the final temperature of the mixture. We want to assume that all of the heat is contained within the system, so q(ice) = -q(water). Now you just want to use the heat of phase change (q=n*deltaH) and the nCdeltaT formulas to find the final temperature, which would ...
Mon Mar 11, 2019 8:47 am
Forum: Balancing Redox Reactions
Topic: Basic solution reaction
Replies: 2
Views: 89

### Re: Basic solution reaction

In this reaction, nitrogen is being reduced so the reduction half reaction should be:
NO2- + 5H2O + 6e- ---> NH3 + 7OH-
Mon Mar 11, 2019 8:44 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: PH of a Cell
Replies: 1
Views: 66

### Re: PH of a Cell

You have to use both. Plug in the calculated (or given) standard potential of the cell into the Nernst equation along with the cell potential measured by the ion-selective electrode (should be given in the problem as well). Then you want to create a Q expression for the reaction and plug that in too...
Mon Mar 11, 2019 8:38 am
Forum: Second Order Reactions
Topic: Second Order Reaction Graphs
Replies: 1
Views: 76

### Re: Second Order Reaction Graphs

No, a second order reaction will have a straight line graph and positive slope that is equal to the rate constant only when 1/[A] is graphed vs time. Showing this plot has a straight line is a way of confirming a second order reaction and finding the value of k.
Tue Mar 05, 2019 12:36 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Elementary Reactions and Reaction Mechanisms
Replies: 2
Views: 105

### Re: Elementary Reactions and Reaction Mechanisms

To answer the second part of your question: the decomposition of O3 to O2 can be hypothesized as occurring by different reaction mechanisms that are each made up of different elementary reactions. The decomposition can occur by a one-step reaction mechanism that is composed of just one elementary re...
Tue Mar 05, 2019 12:30 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 6N.15
Replies: 1
Views: 121

### Re: 6N.15

For this problem, you want to recognize that it is a concentration cell reaction, so standard cell potential is zero and cell potential is equal to -(RT/nF) ln Q. In the 6I.1 table, you can find that Ksp = 6.5×10^−18 for Ni(OH)2 which means [Ni][OH]^2 = 6.5x10^-18. Use your concentration of OH to fi...
Tue Mar 05, 2019 12:21 pm
Forum: General Rate Laws
Topic: Orders
Replies: 3
Views: 126

### Re: Orders

Finding the order of a reaction has many applications, including being able to identity the differential and integrated rate laws from the order. Know rate laws allows us to calculate a variety of values such as k and the concentration of a species. Hope that helps!
Mon Feb 25, 2019 8:48 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs Free Energy and equilibrium concentration
Replies: 2
Views: 92

### Re: Gibbs Free Energy and equilibrium concentration

Because ATP is a reactant, it goes on the bottom of the K and Q expressions. So if the concentration of ATP increases by 4, you would want divide K by 4 to get Q.
Mon Feb 25, 2019 8:36 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Positive vs negative voltage
Replies: 1
Views: 79

### Re: Positive vs negative voltage

We prefer positive voltage values because they are an indicator of spontaneity of the reaction. The equation standard delta G = -nF(standard E) where E is cell potential (or voltage), shows that positive values of E give negative values for standard Gibbs free energy, indicating that the cell reacti...
Mon Feb 25, 2019 8:33 am
Forum: Balancing Redox Reactions
Topic: Single Reactant in Redox
Replies: 2
Views: 78

### Re: Single Reactant in Redox

If there is only one reactant, it will often act as both the reducing and oxidizing agent in different half-reactions.
Mon Feb 25, 2019 8:31 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs Free Energy for Equilibrium
Replies: 1
Views: 82

### Re: Gibbs Free Energy for Equilibrium

Change in Gibbs free energy at equilibrium does equal 0; however, standard Gibbs free energy equals -RT ln K. This relates allows for K to be an indicator of spontaneity because at K>1 favors products and produces a negative standard delta G while a K<1 favors reactants and produces a positive stand...
Tue Feb 19, 2019 9:58 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Van't Hoff Equation
Replies: 3
Views: 100

### Re: Van't Hoff Equation

The intention of the van't Hoff equation is to confirm Le Chatelier's principle for the effect of temperature on K not the other way around. I think you want to think of K being dependent on temperature, not vice versa. According to the equation, a change in temperature of a certain amount changes K...
Tue Feb 19, 2019 9:54 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Molar Gibbs free energy
Replies: 3
Views: 145

### Re: Molar Gibbs free energy

You can also have standard molar Gibbs free energy, which can be used to calculate Gibbs free energy of a reaction. That value is the Gibbs free energy of a substance under standard conditions per mole. Hope that helps!
Tue Feb 19, 2019 9:52 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: altering gibbs free energy equations
Replies: 2
Views: 92

### Re: altering gibbs free energy equations

Gibbs free energy of a substance can be measured under any conditions because it is simply a value; however, change in Gibbs free energy is generally measured at constant temperature and pressure. Hope that helps!
Mon Feb 11, 2019 9:43 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Homework during midterm week [ENDORSED]
Replies: 5
Views: 148

### Re: Homework during midterm week[ENDORSED]

I think any thermodynamics/thermochemistry problems are appropriate because its what we covered last.
Mon Feb 11, 2019 9:42 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Homework(calc enthalpies)
Replies: 1
Views: 77

### Re: Homework(calc enthalpies)

for #15, because you were given the standard combustion enthalpies, the question is asking you to write out the chemical equations for the combustions of the reactants and products and use Hess' Law to determine the overall reaction enthalpy. Whereas, for #17, we can use the standard enthalpies of f...
Mon Feb 11, 2019 9:26 am
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Isothermal reactions and delta U
Replies: 1
Views: 91

### Re: Isothermal reactions and delta U

That is what delta U suggests. Especially because internal energy is a state function, it shouldn't matter whether the process is reversible or irreversible, but only for calculating delta U! Reversibility still definitely matters for calculating q and w.
Mon Feb 11, 2019 9:23 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Explaining Hess's Law with enthalpy = a state function?
Replies: 3
Views: 128

### Re: Explaining Hess's Law with enthalpy = a state function?

This just touches on the idea that because enthalpy is a state function, the path taken to reach a certain enthalpy doesn't matter so enthalpies can be calculated by adding together the enthalpies of multiple steps of a larger reaction.
Mon Feb 11, 2019 9:16 am
Forum: Administrative Questions and Class Announcements
Replies: 179
Views: 12268

For question 3 on the midterm review worksheet, I was wondering why the answer is -312 kJ/mol. I'm sure I'm just making a calculator/stupid error, but I got +312 kJ/mol. Thanks for any help with this!
Tue Feb 05, 2019 7:44 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Change in Entropy at a Constant Heat Capacity
Replies: 1
Views: 53

### Change in Entropy at a Constant Heat Capacity

In Topic 4H in the 7th edition of the textbook, it says that "if the heat capacity is constant throughout the temperature range of interest, then ΔS=nRln(T2/T1)." I was just curious about this equation because I thought for a change in temperature, the appropriate equation to use was ΔS=Cl...
Tue Feb 05, 2019 11:42 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: closed systems
Replies: 6
Views: 178

### Re: closed systems

Closed systems can have constant pressure, volume or neither. However, one of the more common examples of a closed system, a beaker with a piston, is usually related to a question in which there is constant pressure.
Tue Feb 05, 2019 11:39 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: HW Problem 8.9 6th edition
Replies: 2
Views: 126

### Re: HW Problem 8.9 6th edition

For this problem, you want to calculate q and w separately and then use the equation delta U = q + w to find the total change in internal energy. q is simply given as 5.5 kJ, but you will need to calculate w using the -P*deltaV equation. Once you have the energy of the work done by the system, you c...
Tue Feb 05, 2019 11:34 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Q change and temperature
Replies: 2
Views: 126

### Re: Q change and temperature

The temperature of a system can remain constant when heat is being supplied if the energy of that heat is being used for the system to do work. For example, if a gas is doing work due to expansion, there may be energy as heat that is driving that expansion and therefore not contributing to an increa...
Tue Feb 05, 2019 11:32 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: isolated systems
Replies: 2
Views: 105

### Re: isolated systems

An isolated system should imply constant volume. Because it cannot exchange energy or matter with its surroundings, a sealed container of constant volume is required for an isolated system.
Mon Jan 28, 2019 11:00 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Heat Capacity of a Calorimeter, Question 4A.11
Replies: 1
Views: 65

### Re: Heat Capacity of a Calorimeter, Question 4A.11

Because the 22.5 kJ of heat is supplied to the system, it is actually calculated as a negative number, so the solution will turn out positive. Hope that helps!
Mon Jan 28, 2019 10:59 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 7th Edit 4A7
Replies: 2
Views: 76

### Re: 7th Edit 4A7

For 4A7, you want to add together both the heat of the copper and the water to get the total heat of the interaction. I believe it comes to something like: a) q = (300.0g)(4.184 J/°C*g)(80°C) + (400.0g)(0.38 J/°C*g)(80°C) q = 112 kJ b) to find the percentage of the heat that went to raising the temp...
Mon Jan 28, 2019 10:52 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Cv and Cp
Replies: 3
Views: 123

### Re: Cv and Cp

Cv or Cp may be specified, but if not you want to be aware of the other factors acting on the system. Cv is molar heat capacity at constant volume, so if your system is in a sealed container, you would use that one. If your system is at constant pressure, like an open container or with a piston, you...
Tue Jan 22, 2019 10:21 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Including mol/L in K calculations
Replies: 2
Views: 77

### Including mol/L in K calculations

I know that K is not written with the units mol/L because of the use of concentration in place of activity for species, but I am wondering if we should include mol/L with the concentrations when writing out our K expression on the test and homework. Just not sure what the correct format/practice is ...
Tue Jan 22, 2019 8:57 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Calculating with Salts
Replies: 1
Views: 37

### Re: Calculating with Salts

In the book, there is a section that details which kinds of cations and anions actually affect the pH of solutions. It's probably a good idea to be familiar with those because they are included in your Ka/Kb calculations while other ions, like group 1 & 2 cations, are not included. Hope that hel...
Tue Jan 22, 2019 8:55 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: when to ignore the second ionization constant
Replies: 3
Views: 144

### Re: when to ignore the second ionization constant

Not sure if this is a foolproof method, but with those questions, as long as Ka2 is less than Ka1, I think you can ignore it. I did not see any specific parameters either.
Tue Jan 22, 2019 8:52 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Exothermic vs Endothermic
Replies: 4
Views: 251

### Re: Exothermic vs Endothermic

For these types of questions, the change in enthalpy (delta H) will probably be given. In that case, positive delta H indicates an endothermic reaction and negative delta H indicates an exothermic reaction. However, a more challenging question may talk about a combustion reaction, which you have to ...
Tue Jan 22, 2019 8:49 am
Forum: Ideal Gases
Topic: ICE table
Replies: 5
Views: 394

### Re: ICE table

It just depends what is given for gases, but you want all of the species in the reaction to be in either concentration or partial pressure form, not a combination of the two. However, either one will work. Hope that helps!
Tue Jan 15, 2019 3:57 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Calculate pOH
Replies: 3
Views: 66

### Re: Calculate pOH

You have to multiply the concentration by two because of the molar ratio between Ba(OH)2 and hydroxide ions. If you don't recognize the difference in moles, your calculation and pH will be way off. Another reason why it's so important to have a balanced reaction before your start making any assumpti...
Tue Jan 15, 2019 3:37 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE Tables [ENDORSED]
Replies: 11
Views: 444

### Re: ICE Tables[ENDORSED]

For ICE tables, you also want to consider where the reaction is if it not at its initial state in terms of which way the reaction will proceed. For example, if you are given the concentrations of some of the reactants and some of the products in the midst of the reaction, you want to calculate Q and...
Tue Jan 15, 2019 3:34 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Changes to K value
Replies: 9
Views: 254

### Re: Changes to K value

When you are looking at changes in the value of K you want to look at whether the reaction is endothermic or exothermic because that will give you a hint as to how K will change if temperature is increased or decreased. For example, if temperature is increased for an endothermic reaction, K increase...
Wed Jan 09, 2019 5:03 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Q
Replies: 6
Views: 136

### Re: Q

Q and K are not always the same because Q represents [P]/[R] at any time in the reaction while K represents that ratio only when the reaction is at equilibrium. If Q does not equal K, we know that the equation is not at equilibrium.
Wed Jan 09, 2019 4:59 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Bar vs. atm
Replies: 4
Views: 81

### Re: Bar vs. atm

It just depends on how the partial pressure of the gas is given. If it is given in bar, use that and same for atm. Just make sure to use the correct form of R if you are converting to a concentration using PV=nRT. The difference between the two is numeric but they serve similar purposes for us.
Wed Jan 09, 2019 4:58 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: solving for equilibrium constants
Replies: 3
Views: 30

### Re: solving for equilibrium constants

If the gas is in a reaction with other aqueous solutions whose equilibrium concentrations are given as concentrations, you may need to convert the partial pressure of your gas to a concentration using the ideal gas equation. In a reaction, you want to use all pressures or all concentrations, not a m...
Tue Dec 04, 2018 3:19 pm
Forum: Conjugate Acids & Bases
Topic: Inductive Effect
Replies: 5
Views: 222

### Re: Inductive Effect

Inductive effect deals with the creation of a permanent dipole in a bond due to electron fluctuations throughout a molecule, it was never discussed in lecture, so I wouldn't worry about it.
Tue Dec 04, 2018 3:06 pm
Forum: Naming
Topic: Naming a Compound
Replies: 2
Views: 111

### Re: Naming a Compound

Hi, Sorry, this doesn't answer your question but I have a similar question so I figured I would add it to this thread. In the textbook, the naming of the compound says to drop the ending of ions and add "-ato" for -ate ions, "-ido" for -ide ions and "-ito" for -ite ions...
Mon Dec 03, 2018 10:24 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Chelates
Replies: 4
Views: 154

### Re: Chelates

Chelating ligands can bind cations tightly because they can bind in multiple locations instead of just one. The multiple binding sites hold the cation more tightly.
Mon Nov 26, 2018 4:33 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Oxidation number
Replies: 9
Views: 245

### Re: Oxidation number

The way Professor Lavelle explained it in class is that you can calculate the oxidation state/number of a transition metal by looking at the charges of the atoms or ions bonded to in a coordinate complex as well as the overall charge of the complex. The oxidation state/number is the charge of the co...
Mon Nov 26, 2018 4:28 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: Size of Atom and Strength of Attractive/Intermolecular Forces
Replies: 1
Views: 166

### Re: Size of Atom and Strength of Attractive/Intermolecular Forces

Larger atoms have stronger intermolecular forces because they are more polarizable (their electron clouds are more easily distorted). This is because they have more electrons surrounding their nucleus and those electrons are not held as tightly by the nucleus due to large energy shells. When we are ...
Mon Nov 26, 2018 4:26 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal charge question Focus 2 (7th Edition)
Replies: 1
Views: 3165

### Re: Formal charge question Focus 2 (7th Edition)

To find the formal charge for C2O4 2- you want to draw the Lewis structure as the book instructs, so with only a single bond between the carbons. This allows for each of the carbons to double bond with one oxygen and single bond with the other. The formal charge of oxygen when it is double bonded is...
Mon Nov 26, 2018 4:17 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: NaCl vs. NiCl
Replies: 3
Views: 139

### Re: NaCl vs. NiCl

For salt, the water completely dissociates the Na and Cl ions because its polarity; the water surrounds all of the separated ions. A similar thing happens with NiCl but here the water actually bonds to the Ni to create a coordinate compound instead of just being electrostatically attracted like with...
Tue Nov 20, 2018 10:14 am
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Polarizability and Ionic Character
Replies: 2
Views: 155

### Re: Polarizability and Ionic Character

It definitely depends on which kinds of elements and ions you want to talk about when discussing polarizing power. As mentioned above, polarizing power describes a cation's ability to create a dipole moment in an anion by disturbing its electron cloud. Because polarizing power follows the same trend...
Tue Nov 20, 2018 10:05 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 3
Views: 121

### Re: Bond Angles

That's right, the textbook is simply saying that both SOCl angles are the same because they have symmetrical shape within the molecule. You are also correct in thinking about the lone pair creating a smaller bond angle for the bound atoms, it's just that that was not what the textbook was asking.
Tue Nov 20, 2018 10:01 am
Forum: Determining Molecular Shape (VSEPR)
Topic: 7th edition problem 2E.5
Replies: 2
Views: 92

### Re: 7th edition problem 2E.5

The shape of the molecule is angular/bent because one of the regions of electron density around the Cl atom is a lone pair, which is not counted when deciding the name of the shape. However, because there are three regions of electron density around the Cl atom, the electron arrangement is trigonal ...
Tue Nov 13, 2018 3:49 pm
Forum: Bond Lengths & Energies
Topic: 2D.13 7th edition
Replies: 3
Views: 128

### Re: 2D.13 7th edition

Drawing the most stable Lewis structure helped me a lot in getting my answer, because the reasoning has to do with the number of bonds between the designated atoms in each of the species.
Tue Nov 13, 2018 3:36 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: The A in the VSEPR Formula [ENDORSED]
Replies: 4
Views: 87

### Re: The A in the VSEPR Formula[ENDORSED]

The A in the VSEPR model has an implied subscript 1 because it is the central atom. I think the purpose is to denote that central atom, but you don't need the superscript because it is implied.
Tue Nov 13, 2018 3:33 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: polarizing power vs polarizability
Replies: 3
Views: 155

### Re: polarizing power vs polarizability

Polarizing power and polarizability are two halves of the same coin. Polarizing power means the power an atom, ion, or molecule has to polarize, or create a dipole in another atom, ion, or molecule. On the other hand, polarizability denotes how easily a species can be polarized. We tend to talk abou...
Tue Nov 13, 2018 3:29 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: Induced Dipole
Replies: 2
Views: 129

### Re: Induced Dipole

Fluctuating electron density definitely results in temporary dipoles (van der Waals forces), but you also might want to think of the fact that these densities are constantly shifting and setting off chain reactions of fluctuating electron densities within the atoms or molecules around it. The consta...
Tue Nov 06, 2018 10:09 am
Forum: Lewis Structures
Topic: Parenthesis for Ions' Lewis Structures
Replies: 2
Views: 106

### Re: Parenthesis for Ions' Lewis Structures

It is a necessary step for the purposes of drawing a correct Lewis structure. If the ion is not bracketed with its charge then there can be significant confusion about the charge of the ion as well as the formal charges of the atoms in the ion. It is best to always put the brackets and denote charge.
Tue Nov 06, 2018 10:07 am
Forum: Trends in The Periodic Table
Topic: Electronegativity vs. Electron Affinity?
Replies: 11
Views: 548

### Re: Electronegativity vs. Electron Affinity?

The trends for ionization energy, electron affinity, and electronegativity are all the same. Electronegativity and electron affinity are very similar, but one major distinction is the fact that electron affinity of an atom doesn't change while its electronegativity can depending on how it is bonding...
Tue Nov 06, 2018 9:57 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: exceptions
Replies: 6
Views: 487

### Re: exceptions

It is correct to think of the 3d^5 4s^1 and 3d^10 4s^1 electron configurations being more stable and lower energy than if the 4s orbital had electrons with paired spins, but as Dr. Lavelle mentioned in lecture, this is because the 3d subshell wants symmetric electron distribution, which is achieved ...
Mon Oct 29, 2018 2:17 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 4f, 5d, and 6s orbitals
Replies: 2
Views: 515

### Re: 4f, 5d, and 6s orbitals

I'm pretty sure Dr. Lavelle said we only needed to know/be able to figure out electron configurations through the 4th period, so I would not worry about it. To answer your question about Cerium, there are a ton of exceptions to the rules that govern the first few periods in the later periods because...
Mon Oct 29, 2018 2:13 pm
Forum: Resonance Structures
Topic: Bond lengths
Replies: 6
Views: 132

### Re: Bond lengths

Yes, the experimentally observed bond lengths for benzene are known/given quantities. In benzene, the fact that the bond lengths are the same matters because it makes the structure symmetrical and therefore lower energy, but you don't have to just know the bond lengths of resonant structures, they w...
Mon Oct 29, 2018 2:10 pm
Forum: Lewis Structures
Topic: 7th Edition 2.B.9
Replies: 5
Views: 99

### Re: 7th Edition 2.B.9

The fact that the potassium ions just float around the phosphorus indicate that the bonds between the atoms are considered ionic, therefore the phosphorus atoms possesses all of the atoms in the model. The way the potassium atoms are floating around the phosphorus I think is pretty arbitrary, they c...
Tue Oct 23, 2018 9:03 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: orbitals and wave functions
Replies: 2
Views: 112

### Re: orbitals and wave functions

Wave functions and orbitals are interchangeable. Orbitals are simply a way to visually represent the wave functions of electrons in certain energy states. So orbitals are the way math functions model electrons. With Dr. Lavelle's mention of experimental data, I think he was just trying to reiterate ...
Tue Oct 23, 2018 8:55 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Bohr Frequency Condition
Replies: 2
Views: 143

### Re: Bohr Frequency Condition

E in that equation actually equals the energy of an electron in that energy shell, not the change in the energy. But yes, you can connect the E=-hR/n^2 to the E=hv equation.
Fri Oct 19, 2018 9:33 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Replies: 1
Views: 137

Hi,

Just wondering if anyone can explain the difference between angular and radial nodes in terms of nodal planes for orbitals. They are mentioned in the textbook, I don't know how to differentiate them. Thanks so much!
Fri Oct 19, 2018 9:28 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Geometric Representations of Orbitals
Replies: 1
Views: 51

### Re: Geometric Representations of Orbitals

I think you want to know that 4 of the 5 d-orbitals have 4 lobes and that the 5th has 2 lobes and the donut, but like Dr. Lavelle said in class, we won't be asked to draw the boundary surfaces necessarily. It just helps with visualization.
Fri Oct 19, 2018 9:26 pm
Forum: Properties of Electrons
Topic: Questions about the energy level [ENDORSED]
Replies: 3
Views: 198

### Re: Questions about the energy level[ENDORSED]

Hi, Energy and energy level are related through the formula: E(n)=-hR/n^2, where E is the energy of the electron, n is the energy level, h is Planck's constant, and R is the Rydberg constant. You're right, in the equation energy and energy level are inversely proportional, but this is because we hav...
Tue Oct 16, 2018 4:14 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Change in energy
Replies: 2
Views: 73

### Re: Change in energy

Hi, delta E is negative because we are talking about the energy of the electron. In class, Dr. Lavelle mentioned how the energy of electron get more negative as they get closer to the nucleus, therefore, when the electron moves from the 4th to the 2nd energy state, it loses (emits) energy in the for...
Tue Oct 16, 2018 4:11 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: converting moles to grams
Replies: 3
Views: 404

### Re: converting moles to grams

Hi,

Yeah, that's totally right. If you have the measured moles of a reactant and want to find the mass of a product, you just need to multiply by the molar ratio of the compounds and then by the molar mass of the product.
Tue Oct 16, 2018 4:06 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Atomic Spectra Module Question
Replies: 2
Views: 129

### Re: Atomic Spectra Module Question

Hi, In order to solve this equation without using Rydberg's equation, you need to find the energy difference of the energy levels with E=hv, which you seem to have. The trick is then to use the negative of that answer when plugging into the deltaE=E(final)-E(initial) equation. Remember, the energy t...
Tue Oct 16, 2018 9:54 am
Forum: Photoelectric Effect
Topic: Energy Unit of keV
Replies: 1
Views: 136

### Re: Energy Unit of keV

Hi, keV stands for kilo electronvolts, so you want to convert that to just electronvolts before using the conversion factor for Joules which is 1 eV/ 1.60218 * 10^-19 J. I'm not sure how often we will use keV but I'm pretty sure the conversion is given on our equations and constants sheet for tests....
Tue Oct 09, 2018 8:18 am
Forum: Properties of Light
Topic: Exam
Replies: 7
Views: 224

### Re: Exam

I think doing all of the homework problems as well as the audio-visual modules is the way to go, because the syllabus said that homework would sometimes be used for tests. Furthermore, the questions in the assessments for the modules were developed by Dr. Lavelle so they may give some sense of what ...
Sat Oct 06, 2018 12:46 pm
Forum: Limiting Reactant Calculations
Topic: Finding Limiting Reactants
Replies: 3
Views: 113

### Re: Finding Limiting Reactants

You do need to take molar ratio into consideration. While amount of moles definitely matters, if the molar amounts are similar for the reactants, comparing their molar ratios with the product you are trying to find will give you a definite limiting reactant. In order to incorporate the molar ratio i...
Sat Oct 06, 2018 12:41 pm
Forum: Significant Figures
Topic: Rounding numbers ending in 5
Replies: 9
Views: 235

### Rounding numbers ending in 5

Hi, I am currently reading Appendix 1C in our textbook about scientific notation. It says that when rounding off numbers ending in 5, the number should be rounded to the "nearest even number." For example, 2.65 would be rounded to 2.6. I feel very much like I have been lied to my entire li...
Wed Oct 03, 2018 5:12 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Molecule vs Formula Unit
Replies: 4
Views: 267

### Re: Molecule vs Formula Unit

Hi, Molecules and formula units are not interchangeable, though they do refer to very similar things. Molecules refer to compounds in which the atoms are bonded covalently, while formula units refer to compounds with atoms that are ionically bonded. People tend to use "molecule" as a blank...
Wed Oct 03, 2018 5:09 pm
Forum: Molarity, Solutions, Dilutions
Topic: Difference between molecules, atoms, and formula units
Replies: 3
Views: 9898

### Re: Difference between molecules, atoms, and formula units

Hi, From what I understand, there is no difference in the calculations for atoms, molecules, and formula units. Because a mole is just 6.022X10^23 things, it doesn't matter whether those things are atoms, molecules, formula units or bicycles. You want to use Avogadro's number as your conversion fact...
Wed Oct 03, 2018 5:06 pm
Forum: Balancing Chemical Reactions
Topic: Molecules present after Dilution
Replies: 2
Views: 127

### Re: Molecules present after Dilution

Hi, This question definitely confused me as well. However, I figured out that while the number of moles and molecules stay the same in the solution as a whole, the molarity, or the number of moles/molecules (once you convert with Avogadro's number) in that 10. mL after 90 dilutions is almost nonexis...