Search found 102 matches

Sat Mar 14, 2020 5:40 pm
Forum: Ideal Gases
Topic: Weak vs Strong Acids and Bases
Replies: 3
Views: 130

Re: Weak vs Strong Acids and Bases

you do not have to use an ICE table when working with strong acids/bases because they dissociate completely.
Sat Mar 14, 2020 5:38 pm
Forum: Ideal Gases
Topic: 5% Rule
Replies: 6
Views: 228

Re: 5% Rule

when using the approximation (removing x when you are subtracting/adding it to something) you must check to make sure that x is less than 5% of the reactant that it is formed from (x will likely be H or OH- so you would use the acid or base)
Sat Mar 14, 2020 5:36 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Reaction enthalpy
Replies: 3
Views: 140

Re: Reaction enthalpy

there are multiple ways to solve this question, it just depends on what information you are given/not given
Sat Mar 14, 2020 5:36 pm
Forum: Ideal Gases
Topic: Kc
Replies: 7
Views: 169

Re: Kc

if something can have a concentration you have to include it i believe, gases/aqueous.
Sat Mar 14, 2020 5:32 pm
Forum: General Rate Laws
Topic: Initial Rate
Replies: 5
Views: 152

Re: Initial Rate

i think they would have to give you one experiment where the concentration is held constant and then if both change in a different one you would first find the change from the one you already know and then find the change from the other change in concentration.
Sat Mar 14, 2020 5:31 pm
Forum: General Rate Laws
Topic: 7A.3 Hw question
Replies: 1
Views: 53

Re: 7A.3 Hw question

unique rate is always positive i believe so you do not have to cancel out a negative
Sun Mar 08, 2020 7:44 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Solids/Liquids
Replies: 3
Views: 94

Re: Solids/Liquids

because rate is measured in change in concentration versus time only things that have concentrations can change it, so only gases and aqueous substances are included i believe.
Sun Mar 08, 2020 7:40 pm
Forum: General Rate Laws
Topic: negatives?
Replies: 2
Views: 89

Re: negatives?

if you were finding the forward rate law you would add a negative if using the unique rate for reactants and vice versa.
Sun Mar 08, 2020 7:37 pm
Forum: General Rate Laws
Topic: 7A.3
Replies: 4
Views: 127

Re: 7A.3

the unique rate is the same for all reactants and products in that unique reaction. so the rate at which the product forms and the reactant is used up must equal each other, so they have to have the same sign.
Sun Mar 08, 2020 7:35 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Equations
Replies: 8
Views: 190

Re: Equations

∆G° = ∆H° - T∆S°and ∆G° = - RT ln K are the essential equations for thermodynamics
Sun Mar 08, 2020 7:32 pm
Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
Topic: Types of Batteries
Replies: 8
Views: 148

Re: Types of Batteries

the chemical rxn in rechargeable batteries is reversible while in non rechargeable batteries it is not.
Sun Mar 01, 2020 9:30 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Initial Rates
Replies: 3
Views: 120

Re: Initial Rates

the only way to determine reaction order is through experiment so i believe we will always be given initial concentrations and rates
Sun Mar 01, 2020 9:28 pm
Forum: Zero Order Reactions
Topic: Reaction Order Number
Replies: 3
Views: 67

Re: Reaction Order Number

they will always be a whole number i believe
Sun Mar 01, 2020 9:27 pm
Forum: General Rate Laws
Topic: Rate of Reactant
Replies: 3
Views: 73

Re: Rate of Reactant

rate always decreases because as you form products you start to form reactants again
Sun Mar 01, 2020 9:24 pm
Forum: General Rate Laws
Topic: Differential Rate Law
Replies: 2
Views: 68

Re: Differential Rate Law

k is the rate constant and is what allows for different rates when there is the same concentration of reactants and products
Sun Mar 01, 2020 9:23 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Comparing Experimental Data
Replies: 3
Views: 123

Re: Comparing Experimental Data

the concentration doubled for one of the reactants and the rate doubled so to find the order you use the equation: change in rate = change in concentration ^ order where you are solving for the order
Mon Feb 24, 2020 11:12 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: gibbs free energy
Replies: 15
Views: 241

Re: gibbs free energy

gibbs free energy is the energy available to do work
Mon Feb 24, 2020 11:10 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Usage for Nernst equation
Replies: 7
Views: 257

Re: Usage for Nernst equation

standard conditions are a specific ratio of products to reactants and if the ratio is not that then you have to use the nernst equation
Mon Feb 24, 2020 11:08 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: work max
Replies: 2
Views: 70

Re: work max

Work(max) is equal to the negative charge times the max cell potential
Mon Feb 24, 2020 11:07 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Electromotive Force
Replies: 3
Views: 70

Re: Electromotive Force

the electromotive force is Ecell, the max potential when very little current is flowing. When there is no current flowing, that is when the difference is at its maximum.
Mon Feb 24, 2020 11:05 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Free energy difference
Replies: 2
Views: 41

Re: Free energy difference

i believe it means that if a reaction is spontaneous (negative delta g) then max cell potential is positive, and vice versa
Sun Feb 16, 2020 8:17 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K
Replies: 12
Views: 237

Re: K

use anything that has a concentration or a pressure (so only aqueous things or gases!)
Sun Feb 16, 2020 8:15 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Spontaneous
Replies: 13
Views: 245

Re: Spontaneous

A reaction is spontaneous when delta G is negative. for this to happen either delta H has to be negative, delta S has to be positive, or both are true. these factors creative spontaneity by driving the reaction either by enthalpy or entropy.
Sun Feb 16, 2020 8:13 pm
Forum: Van't Hoff Equation
Topic: Variable Explanations
Replies: 3
Views: 45

Re: Variable Explanations

the K values are the equilibrium constants at the two different temperatures, delta H not is the reaction enthalpy, and R is a constant.
Sun Feb 16, 2020 8:10 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: How to incorporate 2nd Law of Thermo
Replies: 3
Views: 88

Re: How to incorporate 2nd Law of Thermo

In the midterm question the change in entropy of the system was not equal to the change in entropy of the surroundings in the irreversible reaction because the reaction occurred in a vacuum and if there are no molecules in the surroundings then you can't change their entropy. I'm not exactly sure ho...
Sun Feb 16, 2020 8:06 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: How to interpret reversible/irreversible graphs
Replies: 6
Views: 161

Re: How to interpret reversible/irreversible graphs

I think the temperature is constant because most reactions occur at a constant external temperature and pressure
Sun Feb 09, 2020 8:40 pm
Forum: Phase Changes & Related Calculations
Topic: irreversible equations
Replies: 2
Views: 76

Re: irreversible equations

i think Wrev and Wirr are the only ones that specify!
Sun Feb 09, 2020 8:39 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Isothermal and Reversible
Replies: 6
Views: 46

Re: Isothermal and Reversible

isothermal means that the reaction takes place at a constant temperature and if a reaction takes place at a constant temperature it is reversible, as such they mean the same thing
Sun Feb 09, 2020 8:36 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Volume decrease
Replies: 7
Views: 102

Re: Volume decrease

This rule only applies when gases are present, if the system only has solids or liquids then a change in volume would not shift the equilibrium because compressing solids and liquids does not make them react more/less
Fri Feb 07, 2020 11:46 am
Forum: Calculating Work of Expansion
Topic: Difference in Wirr and Wrev
Replies: 4
Views: 64

Re: Difference in Wirr and Wrev

irreversible processes are done under constant pressure while reversible are not, and since w is a product of pressure and volume, work is higher when pressure is not constant because the gas will have to do more work
Fri Feb 07, 2020 11:38 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Entropy
Replies: 4
Views: 43

Re: Entropy

entropy is an extensive property because it depends on the amount of substance present. more of a substance = a higher entropy.
Thu Jan 30, 2020 1:38 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard Reaction Enthalpies
Replies: 2
Views: 27

Re: Standard Reaction Enthalpies

i think we are probably equally likely to be tested over any of the three methods for calculating enthalpy
Thu Jan 30, 2020 1:36 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond Enthalpies
Replies: 5
Views: 55

Re: Bond Enthalpies

bond enthalpies is the least accurate because bond enthalpy is an average value not a standard value
Thu Jan 30, 2020 1:35 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Homework Help
Replies: 1
Views: 63

Re: Homework Help

to solve this question you use the given equation: q=nC ΔT
you are directly given q, n, and the initial temperature and must use the equations: ideal gas, Cp=(5/2)R and Cv=(3/2)R to find C for parts a and b to find final temperature

hope this helps!
Thu Jan 30, 2020 1:30 pm
Forum: Phase Changes & Related Calculations
Topic: Molar Heat Capacity at Cp s. Cv
Replies: 4
Views: 69

Re: Molar Heat Capacity at Cp s. Cv

molar heat capacity of the same gas is different at a constant pressure vs a constant volume, you can use that equation with both Cp and Cv it would just result in a different answer for Cp vs Cv
Thu Jan 30, 2020 1:28 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond enthalpy
Replies: 2
Views: 39

Re: Bond enthalpy

using bond enthalpies to calculate delta h is the least accurate method, but to do so you would be given the bond enthalpies of the products/reactants and you would plug them into the equation we are given
Sun Jan 26, 2020 6:19 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Pressure and equilibrium
Replies: 9
Views: 86

Re: Pressure and equilibrium

concentration of either the products or reactants do not change the equilibrium constant, they simply shift the reaction
Sun Jan 26, 2020 6:17 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8894
Views: 1531740

Re: Post All Chemistry Jokes Here

You're so hot you could change an equilibrium constant
Sun Jan 26, 2020 6:16 pm
Forum: Phase Changes & Related Calculations
Topic: Phase changes
Replies: 8
Views: 80

Re: Phase changes

Some of the energy that is used to heat up something is also used to create a phase change, so there could be no measurable change in heat while there was heat absorbed.
Sun Jan 26, 2020 6:14 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Order of homework for Thermochem unit
Replies: 6
Views: 110

Re: Order of homework for Thermochem unit

I would do the questions that relate to the stuff we've learned in class, so skip those two sections and come back to them when we've learned that information.
Sun Jan 26, 2020 6:12 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Pressure and equilibrium
Replies: 9
Views: 86

Re: Pressure and equilibrium

You are right, pressure does not affect the equilibrium constant.
Sun Jan 26, 2020 6:10 pm
Forum: Phase Changes & Related Calculations
Topic: Method 2 for calculating enthalpy changes
Replies: 1
Views: 36

Re: Method 2 for calculating enthalpy changes

Method 2 would possibly be used if the only information you are given is bond enthalpy. I would also make sure you understand why it is the least accurate though as well.
Sun Jan 26, 2020 6:09 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Best method for reaction enthalpies
Replies: 2
Views: 19

Re: Best method for reaction enthalpies

I think method 1 and method 3 are both accurate so it depends on what information you are given as to which one you use.
Sun Jan 26, 2020 6:07 pm
Forum: Phase Changes & Related Calculations
Topic: work and heat
Replies: 3
Views: 42

Re: work and heat

They both depend on the path that was taken to get to the initial state to the final state.
Sun Jan 26, 2020 6:04 pm
Forum: Phase Changes & Related Calculations
Topic: Standard reaction enthalpy vs. Standard enthalpy of formation
Replies: 2
Views: 37

Re: Standard reaction enthalpy vs. Standard enthalpy of formation

Reaction enthalpy is the heat given off/absorbed during a reaction while enthalpy of formation is the difference between the elements in their standard state and the compound they form. You will need to use these in the different methods for calculating enthalpy.
Sun Jan 26, 2020 6:02 pm
Forum: Phase Changes & Related Calculations
Topic: Method 3
Replies: 1
Views: 34

Re: Method 3

In method 3 the values of delta H were given.
Thu Jan 09, 2020 3:24 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Purity
Replies: 3
Views: 67

Re: Purity

The only thing that effects the equilibrium coefficient is a change in temperature
Thu Jan 09, 2020 3:22 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Direction
Replies: 4
Views: 52

Re: Direction

if Q is less than K then the reaction will proceed in the forward direction, while if Q is greater than K the reaction will proceed in the reverse direction.
Thu Jan 09, 2020 3:21 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE Table Ratios
Replies: 7
Views: 82

Re: ICE Table Ratios

I believe both work but a balanced equation should always have whole number coefficients so I would use whole number ratios.
Thu Jan 09, 2020 3:17 pm
Forum: Ideal Gases
Topic: Ideal Gases
Replies: 3
Views: 36

Re: Ideal Gases

I think we need to know how to use the idea gas law to go from pressure to concentration. We may use it for other applications in the future but at this point I think that’s it.
Thu Jan 09, 2020 3:15 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Q
Replies: 4
Views: 41

Re: Q

The reaction quotient can be compared to K to find out if the reaction is in pre-equilibrium (Q<K), equilibrium(Q=K), or post-equilibrium(Q>K).
Mon Dec 02, 2019 5:35 pm
Forum: Lewis Acids & Bases
Topic: HW Question J23
Replies: 1
Views: 61

Re: HW Question J23

H2CO3 is a little less common but CO3 is carbonate and when naming an acid you add -ic to it so it is carbonic acid and H2SO4 is sulfuric acid and Dr. Lavelle has talked about it in class so you should make sure to memorize it.
Mon Dec 02, 2019 5:30 pm
Forum: Amphoteric Compounds
Topic: water
Replies: 3
Views: 63

Re: water

Yes, water is an amphoteric compound because it can both accept and donate a H atom.
Mon Dec 02, 2019 5:29 pm
Forum: Bronsted Acids & Bases
Topic: Defining brosted and lewis
Replies: 5
Views: 99

Re: Defining brosted and lewis

It should be the reverse. The definition of a Lewis acid/base is more general than Bronstead acid/base.
Mon Dec 02, 2019 5:22 pm
Forum: Lewis Structures
Topic: 2.61
Replies: 2
Views: 179

Re: 2.61

I think the radical is on the carbon because it is only forming 3 bonds
Mon Dec 02, 2019 5:21 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: 9C.9
Replies: 1
Views: 34

9C.9

I understand (a) and (b) in this question but I am confused as to how to determine the coordination number for (c) [PtCl2(en)2]2+ and (d)[Cr(edta)]-
Wed Nov 27, 2019 3:50 pm
Forum: Conjugate Acids & Bases
Topic: What are conjugates?
Replies: 3
Views: 78

Re: What are conjugates?

Conjugate acids/bases are the compounds formed from a reaction involving an acid/base. You identify them by figuring out what compound on the reactant side is an acid/base and then finding the compound that looks like it on the product side. Acids form conjugate bases and bases form conjugate acids.
Wed Nov 27, 2019 3:48 pm
Forum: Amphoteric Compounds
Topic: Amphoteric Compounds other than Be, Al, Ga, Sn, Pb, and Sb
Replies: 3
Views: 62

Amphoteric Compounds other than Be, Al, Ga, Sn, Pb, and Sb

I understand that Be, Al, Ga, Sn, Pb, and Sb form amphoteric compounds but how do we tell for other compounds? I know that H2O is amphoteric but it doesn't have any of these elements so how do we tell for other compounds?
Wed Nov 27, 2019 3:44 pm
Forum: Conjugate Acids & Bases
Topic: Determining Conjugate Acid and Bases
Replies: 2
Views: 55

Re: Determining Conjugate Acid and Bases

Acids and bases will be on the reactant side while their conjugate base/acid will be on the product side. You should be able to identify the acid/base by identifying which is the proton donor/acceptor.
Wed Nov 27, 2019 3:40 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordinate covalent bonds
Replies: 3
Views: 99

Re: Coordinate covalent bonds

Although one atom is contributing 2 electrons, these electrons are being shared by the two atom that the bond is between rather than being transferred from one atom to another.
Wed Nov 27, 2019 3:38 pm
Forum: Lewis Acids & Bases
Topic: Bronsted and Lewis Acids
Replies: 4
Views: 64

Re: Bronsted and Lewis Acids

In addition, all Bronstead acids are Lewis acids and all Bronstead bases are Lewis acids, but not vice versa. The definition of a Lewis acid/base is more general than Bronstead acid/base.
Sun Nov 24, 2019 12:25 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordination Compounds
Replies: 3
Views: 39

Re: Coordination Compounds

A coordination compound occurs in a compound that has a coordinate covalent bond. This means that one atom has supplied both electrons in the bond.
Sun Nov 24, 2019 12:24 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: CN- Coordination Compound
Replies: 1
Views: 38

Re: CN- Coordination Compound

C donates the lone pair because it has the lower electronegativity I believe, you should always show C making the coordinate covalent bond in this structure.
Sun Nov 24, 2019 12:21 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Non-polar atoms with lone pairs
Replies: 4
Views: 63

Re: Non-polar atoms with lone pairs

Atoms with lone pairs can be non-polar, for example I2.
Sun Nov 24, 2019 12:20 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Non-polar molecules with different non-central atoms
Replies: 3
Views: 47

Re: Non-polar molecules with different non-central atoms

It depends on the arrangement of the atoms, for example CH2Cl2 is polar.
Sun Nov 24, 2019 12:17 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Hybridization
Replies: 7
Views: 137

Re: Hybridization

Hybridization occurs when an atom uses both its s and p orbitals to bond with another atom. This creates an imbalance in energy levels so hybridization occurs to level out the energy as it combines these orbitals.
Wed Nov 13, 2019 2:24 pm
Forum: Administrative Questions and Class Announcements
Replies: 4
Views: 89

We got our physical midterms passed back today after class by our TAs so if you didn't get yours I would email your TA to see if you can get it from them.
Wed Nov 13, 2019 2:04 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR formula for molecules of the same atom
Replies: 3
Views: 38

Re: VSEPR formula for molecules of the same atom

In this case it does result in a linear formula but O3 would be bent, so that is not a rule.
Wed Nov 13, 2019 2:01 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Linear VSEPR model
Replies: 21
Views: 671

Re: Linear VSEPR model

In lecture Dr. Lavelle only went over examples where there are no lone pairs, but yes lone pairs do influence shape and I believe we will learn about it on Friday during lecture.
Wed Nov 13, 2019 1:59 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Linear VSEPR model
Replies: 21
Views: 671

Re: Linear VSEPR model

If the central atom has either zero or three non bonding electron domains in addition to the two bonding it is linear but any other number would be some other shape.
Wed Nov 13, 2019 1:58 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Molecular Shape Name
Replies: 17
Views: 345

Re: Molecular Shape Name

I think it's necessary to learn the names for all the shapes that Dr. Lavelle talks about in lecture. I found it easiest to memorize when I looked at all shapes that have the same number of electron domains and memorized them in decreasing bonding domain order.
Wed Nov 13, 2019 1:55 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Resonance VSEPR
Replies: 6
Views: 78

Re: Resonance VSEPR

It does not matter what resonance structure you look at when determining molecular shape using the VSEPR model because it only looks at bonding pairs and not the amount of bonds.
Wed Nov 13, 2019 1:54 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Sulfur Hexafluoride VSEPR
Replies: 3
Views: 103

Re: Sulfur Hexafluoride VSEPR

Octahedral shape describes a compound with 6 shared pairs of electrons and since there are 6 bonds in SF6 it is octahedral.
Wed Nov 13, 2019 1:53 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Methane VSEPR
Replies: 7
Views: 118

Re: Methane VSEPR

Because areas of electron density should be spread as far apart as possible and actual molecules do not exist in 2D, bond angles of 109.5 allow this to occur.
Wed Nov 13, 2019 1:50 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Test 2
Replies: 15
Views: 279

Re: Test 2

I think that everything that we have learned that was not tested on the midterm will be on test 2 plus probably drawing lewis structures. (outlines 3 and 4)
Wed Nov 13, 2019 1:47 pm
Forum: Administrative Questions and Class Announcements
Replies: 10
Views: 244

Does anyone know if there is an answer key to the midterm posted anywhere? I thought Dr. Lavelle mentioned one during lecture today but I can't find it.
Sun Nov 03, 2019 2:59 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Central atom
Replies: 8
Views: 168

Re: Central atom

When drawing lewis structures your goal should not be to have the central element have a formal charge of zero but rather have the most elements have a formal charge of zero and the most electronegative elements carry the negative formal charges.
Sun Nov 03, 2019 2:56 pm
Forum: Bond Lengths & Energies
Topic: Ions for the Midterm
Replies: 3
Views: 67

Re: Ions for the Midterm

Dr. Lavelle said in class he would give us the formulas for any compounds we have not been exposed to a lot (like he might not give us the formula for water but he'd give us those)
Sun Nov 03, 2019 2:51 pm
Forum: Lewis Structures
Replies: 5
Views: 100

In the example Dr. Lavelle gave in class, the carbon held the unpaired electron rather than the hydrogen because carbon only contributed to three bons and as such it has one electron left.
Sun Nov 03, 2019 2:49 pm
Forum: Octet Exceptions
Replies: 1
Views: 47

In the example Dr. Lavelle gave in class you were able to tell that the carbon held the unpaired electron because in a methyl radical the H has one bond so its formal charge is zero but the carbon does not so it holds the unpaired electron.
Sun Nov 03, 2019 2:47 pm
Forum: Octet Exceptions
Replies: 7
Views: 92

A radical is any compound with an unpaired electron (such as a methyl radical formed by burning hydrocarbons). They are significant because they are another example of an exception to the octet guideline and are so highly reactive that they can react with DNA and damage it.
Sun Oct 27, 2019 1:33 pm
Forum: Lewis Structures
Topic: Clarification
Replies: 6
Views: 85

Re: Clarification

I think in lecture Dr. Lavelle said that obtaining a formal charge of zero is more important than following the octet rule which is why there are so many exceptions to it. Because having an octet on one element does not mean that the surrounding elements will also have an octet.
Sun Oct 27, 2019 1:30 pm
Forum: Bond Lengths & Energies
Topic: Bond Length
Replies: 4
Views: 93

Re: Bond Length

triple bonds are shorter in length than double, and double than single. This is because these types of bonds are stronger and therefore draw the elements closer. And yes, quadruple bonds exist but they are most stable among transition metals.
Sun Oct 27, 2019 1:26 pm
Forum: Resonance Structures
Topic: formal charge
Replies: 3
Views: 74

Re: formal charge

If each element in a compound has a formal charge of zero than it is the most stable form of that compound, and because a lot of compounds are stable they have a formal charge of zero on all the elements. The sulfur did not have a charge in the example given in class because oxygen is more electrone...
Sun Oct 27, 2019 1:24 pm
Forum: Resonance Structures
Topic: Multiple Resonant Structures
Replies: 2
Views: 32

Re: Multiple Resonant Structures

I think that the number of resonance structures a compound can form doesn't necessarily mean much about it, I think more the fact that it has multiple resonance structures is a defining characteristic of the compound because it means the electrons are delocalized.
Sat Oct 26, 2019 3:45 pm
Forum: Properties of Light
Topic: frequency/intensity
Replies: 2
Views: 52

Re: frequency/intensity

Intensity is proportional to a wave's amplitude and it typically refers to the amount of photons being emitted, so it is something completely separate from frequency.
Sun Oct 20, 2019 6:55 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Why is copper like this?
Replies: 6
Views: 82

Re: Why is copper like this?

If the 3d sub-shell is either half full or full that is more stable so the 4s sub-shell will not be full then!
Sun Oct 20, 2019 6:53 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 3d vs 4s
Replies: 2
Views: 37

Re: 3d vs 4s

Electrons are removed in the order that you write the configuration, so 4s first.
Sun Oct 20, 2019 6:50 pm
Forum: *Shrodinger Equation
Topic: Schrodinger for exam
Replies: 20
Views: 453

Re: Schrodinger for exam

Yeah I don’t think we need to know absolutely everything about it but understanding how it relates to the other things that were mentioned already!
Sun Oct 20, 2019 6:48 pm
Forum: *Shrodinger Equation
Topic: Schrodinger’s Wave Function
Replies: 3
Views: 66

Re: Schrodinger’s Wave Function

As was said above, the equation represents the wave characteristic of electrons, so be squaring it you are able to find out how likely you are to find an electron.
Sun Oct 20, 2019 6:46 pm
Forum: Properties of Light
Topic: Week 3 Homework
Replies: 9
Views: 194

Re: Week 3 Homework

Yeah we can do quantum for this week but next weeks homework will be the next unit!
Sat Oct 12, 2019 6:34 pm
Forum: Properties of Light
Topic: Wave Properties of Electrons
Replies: 3
Views: 59

Re: Wave Properties of Electrons

I think Dr. Lavelle used the example of constructive and destructive interference in light waves to illustrate the idea of diffraction so that he could show us that because electrons passing through a crystal show diffraction they have wave-like properties. So if you were asked to explain how electr...
Sat Oct 12, 2019 6:29 pm
Forum: Properties of Light
Topic: Balmer vs Lyman series
Replies: 4
Views: 98

Re: Balmer vs Lyman series

The Balmer series includes the wavelengths of light emitted when an electron falls from an outer energy level to n=2 and Lyman series is the same except for the electron falls to n=1 instead.
Sat Oct 12, 2019 6:09 pm
Forum: Properties of Light
Topic: 1B3
Replies: 3
Views: 52

Re: 1B3

Yes, photoelectric effect is correct because if light only had wave properties, increasing the amplitude should eject more electrons, but that was not the case as the only thing that increased the amount of electrons ejected was increasing frequency/decreasing wavelength.
Sat Oct 12, 2019 6:04 pm
Forum: Properties of Light
Topic: UV photons vs. photons of visible light
Replies: 2
Views: 23

Re: UV photons vs. photons of visible light

Yes, the energy of a photon of light is equal to Planck's constant times frequency, so as frequency increases (as when going from visible light to UV) energy also increases.
Sat Oct 12, 2019 6:00 pm
Forum: Properties of Light
Topic: Homework 1A3
Replies: 2
Views: 61

Re: Homework 1A3

In addition to what was said already, the speed of light is a constant because as the frequency decreases the wavelength increases proportionally, so speed never changes.
Thu Oct 03, 2019 2:25 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Fundamentals E.3
Replies: 7
Views: 228

Re: Fundamentals E.3

The way the diagram is set up is kind of confusing as there are 9 astatine atoms shown, but it is not saying that you need to put all nine it is asking how many you need which is not necessarily all nine as the calculations show.
Thu Oct 03, 2019 2:21 pm
Forum: Significant Figures
Topic: Sig Fig Rules
Replies: 3
Views: 101

Re: Sig Fig Rules

Typically the amount of sig figs you have in your final answer is equal to the amount of sig figs in the given number that has the least sig figs. So if you were given two initial masses, one with 3 sig figs and one with 4, and your final answer was also a mass you would most likely round to 3 sig f...
Thu Oct 03, 2019 2:18 pm
Forum: Balancing Chemical Reactions
Topic: Question L37
Replies: 2
Views: 101

Re: Question L37

I believe that in the solutions it is telling you how you would do this in a lab situation, and when you are mixing acids and bases you must always add the acid in order to the water and not the other way around so the exothermic reaction that occurs during mixing can be somewhat limited, but the am...
Thu Oct 03, 2019 2:13 pm
Forum: Limiting Reactant Calculations
Topic: Fundamentals M7
Replies: 3
Views: 64

Re: Fundamentals M7

The way I was taught to find the limiting reactant is to convert from grams to moles and then to divide the amount of moles you find by the coefficient in the reaction and then compare those numbers so you do not have to go about comparing ratios and the math gives you a more clear answer as to whic...