Search found 102 matches
- Sat Mar 14, 2020 5:40 pm
- Forum: Ideal Gases
- Topic: Weak vs Strong Acids and Bases
- Replies: 3
- Views: 381
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: 608
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: 323
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: 632
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: 459
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: 165
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: 289
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: 230
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: 430
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: 580
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: 593
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: 332
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: 306
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: 294
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: 195
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: 332
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: 885
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: 665
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: 205
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: 351
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: 187
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: 746
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: 832
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: 199
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: 300
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: 702
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: 258
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: 174
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: 289
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: 247
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: 198
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: 106
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: 234
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: 216
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!
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: 229
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: 125
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: 290
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: 9651
- Views: 3862159
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: 242
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: 356
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: 290
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: 114
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: 166
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: 228
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: 103
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: 96
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: 167
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: 152
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: 273
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: 143
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: 167
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: 197
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: 196
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: 454
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: 333
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: 120
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: 307
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: 273
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: 134
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: 272
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: 262
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: 192
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: 89
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: 294
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: 234
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: 464
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
- Topic: Midterm grade
- Replies: 4
- Views: 193
Re: Midterm grade
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: 135
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: 1369
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: 1369
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: 906
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: 270
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: 756
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: 428
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: 880
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
- Topic: Midterm Answers
- Replies: 10
- Views: 754
Midterm Answers
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: 366
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: 225
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
- Topic: Radicals
- Replies: 5
- Views: 217
Re: Radicals
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
- Topic: Radicals
- Replies: 1
- Views: 147
Re: Radicals
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
- Topic: What are radicals
- Replies: 7
- Views: 294
Re: What are radicals
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: 233
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: 270
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: 369
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: 161
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: 152
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: 269
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: 106
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: 913
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: 150
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: 427
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: 210
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: 194
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: 108
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: 90
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: 124
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: 438
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: 210
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: 233
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: 129
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...