## Search found 65 matches

Sun Mar 17, 2019 2:38 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Reducing Power
Replies: 3
Views: 342

### Re: Reducing Power

and if you are looking for which is most likely to be oxidized it would be the one with the lowest E
Tue Mar 12, 2019 6:54 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat Capacity at Constant Volume and Pressure
Replies: 2
Views: 266

### Re: Heat Capacity at Constant Volume and Pressure

we use 3/2 when working with monoatomic molecule like Ne and constant volume and 5/2 for a monoatomic molecule constant pressure. Add 1 to both of them when using a diatomic molecule like H2. We don't need to know anything past monoatomic molecules on the test
Tue Mar 12, 2019 6:51 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: reaction profile question
Replies: 2
Views: 95

### Re: reaction profile question

i don't have the 7th edition but if a catalyst is introduced then the activation energy should be lower not higher
Tue Mar 12, 2019 6:49 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: rate determining
Replies: 1
Views: 87

### Re: rate determining

no in this case it would be because while step 2 may have been the determining step n2o2 was substituted by [no]^2 since n2o2 is not in the final equation. Only molecules that are in the overall reaction can be part of the rate law
Wed Mar 06, 2019 9:21 pm
Forum: First Order Reactions
Topic: order
Replies: 5
Views: 194

### Re: order

from what i recall i don't think we can if we are given a random equation as the coeffeicents don't always line up with the order of the reaction so the only sure way to figure it out is through experimental data
Wed Mar 06, 2019 9:18 pm
Forum: First Order Reactions
Topic: Pseudo-First-Order Reaction
Replies: 5
Views: 205

### Re: Pseudo-First-Order Reaction

it certain sense it is since in that we are trying to isolate the reactants to figure out each of their pseudo reaction orders independent of the other reactants
Wed Mar 06, 2019 9:16 pm
Forum: General Rate Laws
Topic: Negative sign for reactant rate
Replies: 2
Views: 103

### Re: Negative sign for reactant rate

yeah it is just a way to balance out the delta concentration of reactants since it will be negative and we want it as a positive since the fact that reactants are used up is implied
Sat Mar 02, 2019 6:10 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6h Edition; 14.23
Replies: 2
Views: 124

### Re: 6h Edition; 14.23

to make sure that you don't confuse your signs it may be best to figure out which method you like the best and stick with that otherwise you may get wrong answers. A good way to check is to see if you get a positive answer as most of the cells should end up having a positive potential
Sat Mar 02, 2019 6:07 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Kinetics vs. Thermodynamics
Replies: 3
Views: 139

### Re: Kinetics vs. Thermodynamics

There can basically be 3 situations The substance is thermodynamically stable so even over a very long period of time it will still stay the same under the same condition The substance is not thermodynamically stable but is kinetically so for the time period that we are worried about the substance w...
Sat Mar 02, 2019 6:02 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: w vs wmax
Replies: 5
Views: 181

### Re: w vs wmax

I think it is the just the maximum amount of work possible like how an isothermal expansion has more work than a constant pressure one
Wed Feb 20, 2019 4:05 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Salt Bridge
Replies: 5
Views: 176

### Re: Salt Bridge

the salt bridge helps to prevent charges from being built up on one side of the cathode and anode interaction so that it can continue creating a current
Wed Feb 20, 2019 3:59 pm
Forum: Van't Hoff Equation
Topic: when to use
Replies: 4
Views: 179

### Re: when to use

you will use it when you want to know the K constant of a reaction at different temperatures when the standard enthalpy of formation is known
Wed Feb 20, 2019 3:56 pm
Forum: Balancing Redox Reactions
Topic: how to balance
Replies: 5
Views: 165

### Re: how to balance

you will balance it like we have been doing it before(making sure the charges balance and matter stays the same), but you will use oxidation numbers to figure out where the charges change in the reaction
Wed Feb 13, 2019 8:36 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Delta n
Replies: 7
Views: 582

### Re: Delta n

Also for most of the reactions you will want to use the change in moles of gases not of all substances
Wed Feb 13, 2019 8:33 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: ΔS=q/t
Replies: 8
Views: 374

### Re: ΔS=q/t

you can use it when t is constant and you can use deltaS=DeltaH/T when pressure is constant
Wed Feb 13, 2019 8:32 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Internal energy (U) of an isolated system
Replies: 17
Views: 979

### Re: Internal energy (U) of an isolated system

how we measure if a system is open, closed, or isolated is if it is able to transfer heat or work with the surroundings which is also how we measure internal energy. In the case of an isolated system it is not able to transfer either so w and q are both 0 which makes deltaU = 0
Wed Feb 13, 2019 11:13 am
Forum: Administrative Questions and Class Announcements
Topic: Midterm Review Question
Replies: 10
Views: 475

### Re: Midterm Review Question

Could someone please explain what we are supposed to do for #14 because I feel like i don't have enough information to do anything
Fri Feb 08, 2019 4:40 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: State Function
Replies: 3
Views: 138

### Re: State Function

For example work is not a state function because the work is different for a isothermal reversible reaction versus a non reversible one even though they both reach the same end points.
Fri Feb 08, 2019 4:38 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 8.49
Replies: 1
Views: 94

### Re: 8.49

for this you will probably just have to assume since 25C is the temperature that the most stable state of a lot of molecules are at and 25C is the same as 298K. Sorry if this isn't much help
Fri Feb 08, 2019 4:34 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: If not Gibbs Free Energy then what is the last topic for midterm?
Replies: 4
Views: 134

### Re: If not Gibbs Free Energy then what is the last topic for midterm?

The last topic is basically all of what we went over today regarding entropy, i.e. system, surrounding and universal entropy. We won't need to do anything relating to gibbs free energy
Fri Feb 08, 2019 4:32 pm
Forum: Calculating Work of Expansion
Topic: Nonexpansion work
Replies: 2
Views: 90

### Re: Nonexpansion work

I think constant volume is what you are trying to calculate for and in that case there would be no work done.
Tue Jan 29, 2019 6:09 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy
Replies: 4
Views: 142

### Re: Enthalpy

enthalpy is defined as the heat in the system so when we are talking about deltaH that is the change in enthalpy between a product and reactant. We can say that heat released is negative because we measure deltaH by products - reactants and if it is exothermic the heat of the product is less than re...
Tue Jan 29, 2019 5:58 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Best Method
Replies: 7
Views: 290

### Re: Best Method

The other option would probably be using the standard enthalpy of formation method because the other method is only for combining the enthalpy of multiple reactions. On the test however the method that we use will probably be dertimned by what information we are given so i wouldn't worry too much ab...
Tue Jan 29, 2019 5:53 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: standard enthalpies of formation
Replies: 2
Views: 93

### Re: standard enthalpies of formation

basically it is the enthalpy required to form the product from reactants that are in their most stable state. Since the product is the most stable state the standard entalphy will be zero. It is a comparative value between the stable reactant and the product
Mon Jan 21, 2019 8:57 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Polyprotic
Replies: 2
Views: 110

### Re: Polyprotic

If we are expected to do any polyphonic calculation then we should be give both ka1 and ka2 so that will tell you if you need to do any extra polyphonic calculations. If they don't give you two then you probably won't need to worry about it
Mon Jan 21, 2019 8:54 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Ka3
Replies: 2
Views: 81

### Re: Ka3

if you look in the textbook the only acid that can even do this is H3PO4 but for that it is such a weak acid that the pKa is over 12 so we won't have to worry about that at all. The max we will have to go is Ka2 and that will probably be only if the first deprotanation is complete
Mon Jan 21, 2019 8:52 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: solving for pka and ka and ph
Replies: 2
Views: 94

### Re: solving for pka and ka and ph

that will give you the molar concentration of h30+ and you can do the same thing for 10^-pOH for the molar concentration of OH-
Mon Jan 14, 2019 4:27 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Acids and Bases
Replies: 7
Views: 264

### Re: Acids and Bases

you basically have to memorize them. Feel free to correct me but I think the list is (there may be a few more bases but i am not 100% sure)
Acids: HCl, HBr, HI, HNO3, HClO3, HClO4, H2SO4
Bases: LiOH, NaOH, KOH, RbOH, CsOH, Ca(OH)2, Sr(OH)2, Ba(OH)2
Mon Jan 14, 2019 4:22 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Module 4 Post Assessment #14
Replies: 3
Views: 205

### Re: Module 4 Post Assessment #14

i think that the answer is c. This is because partial pressure can be derived from concentration using p= conc * r* t and so a decrease in partial pressure basically means that the amount of co2 is less so the reaction will go towards reactants and decrease the concentration of o2
Mon Jan 14, 2019 4:10 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Solids and Liquids in K
Replies: 4
Views: 150

### Re: Solids and Liquids in K

from my understanding it is that you can't really define the concentration of lets a solid block of salt since the entire thing is pure salt, this can also be applied to any other solid. For liquids like water it is because the start and end concentration are so large and similar that it doesn't mat...
Wed Jan 09, 2019 1:13 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: When can "-X" be disregarded?
Replies: 2
Views: 86

### Re: When can "-X" be disregarded?

If i remember correctly from his videos we would disregard it if we were working with a cubic equation and if the k is less than 10^-4
Wed Jan 09, 2019 1:10 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Favoring Products/Reactants
Replies: 3
Views: 126

### Re: Favoring Products/Reactants

basically since q is calculated the same way as k using conc[p]/conc[r], if q > k then that means that there is more product than there should be at equilibrium and the reaction will go towards the reactants and the reverse if q < k
Tue Jan 08, 2019 9:39 pm
Forum: Ideal Gases
Topic: Activity
Replies: 3
Views: 145

### Re: Activity

We don't need to worry much about that since in his videos Lavelle said that we don't need to know anything about activity in undergrad
Tue Dec 04, 2018 11:37 am
Forum: Calculating the pH of Salt Solutions
Topic: Question 12.19 6th edition
Replies: 1
Views: 95

### Re: Question 12.19 6th edition

The way I did this was to simply assign the concentration a random number, I did a concentration of 1M and then do the calculation from there. It doesn't matter what value you use for the initial concentration. You would then calculate the pH of the concentration using -log(concentration). Then do t...
Tue Dec 04, 2018 11:30 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: HW 17.35 6th Ed
Replies: 1
Views: 102

### Re: HW 17.35 6th Ed

b would be the correct answer since the angle between the two NH2 would be in such a way that it could easily bond to two bonding regions of an octahedral Transition metal. A and C on the other hand have to great of an angle between the two NH2 for them to be able to easily bind to a transition meta...
Tue Dec 04, 2018 11:23 am
Forum: Air Pollution & Acid Rain
Topic: Basic Rain
Replies: 5
Views: 418

### Re: Basic Rain

I don't want to say 100% no but it would be highly unlikely as acidic rain occurs due to nonmetal oxides in the atmosphere such as CO2 and for basic rain to theoretically occur there would need to be basic oxides in the atmosphere which doesn't occur in large enough quantities to make the rain basic
Tue Dec 04, 2018 11:20 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Polydentates: HW 17.33 6th Ed
Replies: 2
Views: 153

### Re: Polydentates: HW 17.33 6th Ed

A polydented is a ligand that can bond to the transition metal in multiple places. Usually it is the large molecule that are polydente but for the final since we don't need to know that many it may be easier just to memorize them. ethylenediamine and oxalate are bidentate diethelynetriamine is tride...
Mon Nov 26, 2018 10:06 pm
Forum: Hybridization
Topic: hybrid orbitals
Replies: 1
Views: 76

### Re: hybrid orbitals

no for each set of hybrid orbitals all of the electrons are at the same energy level. For example for CH4 it is sp3 hybridized and has a total of 8 electrons. All eight of the electrons are at the same energy levels since there is new energy level that is in-between 2s and 2p and this allows all 4 o...
Mon Nov 26, 2018 10:01 pm
Forum: Hybridization
Topic: Pi bonds
Replies: 3
Views: 153

### Re: Pi bonds

for the pi bonds you would have to imagine two balloons coming from the top and bottom of each atom and the adjacent balloons slightly overlapping each other. This is because the pi bonds use the p-orbital which are along the axis. Also because each p-orbital has two parts this explains why molecule...
Mon Nov 26, 2018 9:51 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Oxidation number
Replies: 9
Views: 290

### Re: Oxidation number

so is the oxidation number basically the charge on the atom kind of like what the charge would be if the atom was an ion?
Fri Nov 23, 2018 11:15 am
Forum: Hybridization
Topic: HW Problem #81
Replies: 1
Views: 34

### Re: HW Problem #81

The formal charge on all 3 of the Boron is -1 but the formal charge on all 3 of the Nitrogen is +1 so when you add up all of the formal charges to get the total charge of the molecule you get zero. As such there is no need for a lone pair on any of the molecules so for both N and B the hybridization...
Fri Nov 23, 2018 11:11 am
Forum: Hybridization
Topic: Forming the different types of bonds
Replies: 2
Views: 120

### Re: Forming the different types of bonds

Since P has 3 different orbitals it depends if the orbitals from the two atoms are one of the ones that are parallel to each other, and thus have a weaker interaction making a pi bond, or if they or on the same line as each other, and have a much stronger interaction and make a sigma bond. it is imp...
Fri Nov 23, 2018 11:04 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Isoelectric species
Replies: 2
Views: 103

### Re: Isoelectric species

yeah it should work since VSEPR is based off of the lewis structure so as long as we can get a lewis structure we should be able to use VSEPR
Thu Nov 15, 2018 11:19 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Will we have to calculate bond angles?
Replies: 8
Views: 259

### Re: Will we have to calculate bond angles?

we will need to know only generic ones like octahedral is 90 degrees but nothing too specific like how NH3 is 107.5
Thu Nov 15, 2018 11:16 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Homework Question 4.5 (6th edition)
Replies: 2
Views: 120

### Re: Homework Question 4.5 (6th edition)

This is because the overall structure if we include the lone pair is trigonal planar and in trigonal planar the bond angles are all 120 degrees. However this is if all 3 electron regions are bonding pairs, but in this case one of them is a lone pair which has more repulsion and will cause the bond a...
Thu Nov 15, 2018 11:13 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Repulsion Strength
Replies: 2
Views: 98

### Re: Repulsion Strength

This is because the two electrons in the lone pair are held closer together to the single atom compared to a bonding pair which is split between two atoms. Since the lone pair is closer to the central atom they will have more repulsion
Wed Nov 07, 2018 11:29 am
Forum: Dipole Moments
Topic: Dispersion strengths of larger atoms
Replies: 5
Views: 168

### Dispersion strengths of larger atoms

I am slightly confused about how dispersion forces work. Is it just based on the number of electrons that are able to be polarized and so the trend is just the more electrons the greater the dispersion or is there something else that I am missing?
Wed Nov 07, 2018 11:21 am
Forum: Bond Lengths & Energies
Topic: Bond Lengths
Replies: 5
Views: 239

### Re: Bond Lengths

Basically, with resonance structure the resonance bonds are basically a blend of the possible bonds since the electrons are more free to move around between the bonds and so due to some interaction that we don't really need to know too much about they will be something a little bit below the average...
Wed Nov 07, 2018 11:18 am
Forum: Electronegativity
Topic: Electron affinity
Replies: 5
Views: 227

### Re: Electron affinity

the exception also applies to phosphorus so for the 3rd row it would be P<Si<S<Cl
Wed Oct 31, 2018 11:38 am
Forum: Lewis Structures
Topic: Question 3.41c for 6th edition
Replies: 1
Views: 52

### Re: Question 3.41c for 6th edition

For this the way to do it is to break it up into the 3 given sections H2C, NH2 and COOH and then from there combine the 3 parts. In situations like this it is important to note instances where the same element is repeated multiple times such as hydrogen being listed 3 times. This will usually give a...
Wed Oct 31, 2018 11:33 am
Forum: Formal Charge and Oxidation Numbers
Topic: FC in relation to Bonds
Replies: 2
Views: 91

### Re: FC in relation to Bonds

By having more bonds(single double triple) the formal charge will increase as 2 electrons in a bond will take away 1 for the formal charge calculation while 2 paired electrons that are not in a bond will take away 2 from the formal charge valuation.
Tue Oct 30, 2018 5:37 pm
Forum: Ionic & Covalent Bonds
Topic: Number of Unpaired Electrons
Replies: 3
Views: 191

### Re: Number of Unpaired Electrons

Also keep in mind that we are only doing the s and p block and only the first row of the d block so you won't have to remember anything too complicated
Tue Oct 23, 2018 11:23 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Chem Homework 1.45 Question Mistake?
Replies: 3
Views: 216

### Re: Chem Homework 1.45 Question Mistake?

No you are correct, if you look on his website this is listed as a mistake in the solutions manual. To clarify +- 5 would be an uncertainty of 10. Hope this helps!
Tue Oct 23, 2018 5:18 pm
Forum: *Particle in a Box
Topic: Test 2
Replies: 9
Views: 815

### Re: Test 2

I am pretty sure I have heard both my TA and Professor Lavell say that we do not have to know schrodingers wave functions just n,l,ml
Mon Oct 22, 2018 11:08 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Question 1.55 6th edition
Replies: 1
Views: 33

### Question 1.55 6th edition

I was wondering why for the problem "In infrared spectroscopy, it is common to express energy in terms of frequency/c, with the units cm-1 (read as reciprocal centimeters). (a) If an absorption occurs in the infrared spectrum at 3600 cm -1, what is the frequency of radiation that corresponds to...
Wed Oct 17, 2018 4:05 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Nodal Planes
Replies: 3
Views: 103

### Re: Nodal Planes

A nodal plane basically means that an electron cannot be on that plane so the density would decrease as we approached the nodal plane for each of the different orbitals. If we take the p orbitals for example, the point where the two lobes meet is a nodal plane and along that plane there is no chance...
Wed Oct 17, 2018 3:56 pm
Forum: DeBroglie Equation
Topic: DeBroglie Equation
Replies: 2
Views: 87

### Re: DeBroglie Equation

The DeBroiglie Equation can be applied to anything that has a rest mass so it should be able to be applied to protons and neutrons
Wed Oct 17, 2018 3:50 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Orbital Notations
Replies: 3
Views: 89

### Re: Orbital Notations

I don't think we have to know the exact reasons why for this class as we are not doing the math to come up with the plots for the orbitals. Im pretty sure as long as we know that it is on the xy axis that is enough and we may not even have to memorize that.
Wed Oct 10, 2018 3:26 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Calculating energy change (Delta E)
Replies: 4
Views: 663

### Re: Calculating energy change (Delta E)

I was wondering if in this case could we use the Rydberg formula v=R{(1/(n1)^2)-(1/(n2)^2)}
Mon Oct 08, 2018 4:58 pm
Forum: Photoelectric Effect
Topic: Rydberg constant
Replies: 3
Views: 88

### Rydberg constant

Is the Rydberg constant (R= 3.29E15 Hz) something that we have to memorize like Avogadro's number for the tests?
Mon Oct 08, 2018 4:54 pm
Forum: Significant Figures
Topic: Formula sheet?
Replies: 5
Views: 309

### Re: Formula sheet?

I asked professor Lavell and he said that any molecular formula will be given and that we wouldn't need to determine the formula from the name
Thu Oct 04, 2018 3:52 pm
Forum: Significant Figures
Topic: Sig Figs... when to round?
Replies: 7
Views: 302

### Re: Sig Figs... when to round?

If we are not supposed to round until the end does it matter if we have the correct sig figs in each step of the problem or will the sig figs only matter at the end in regards to grading
Mon Oct 01, 2018 11:29 pm
Forum: Significant Figures
Topic: E29 (d.)
Replies: 1
Views: 121

### E29 (d.)

for question E29 "A chemist measured out 8.61 g of copper(II) chloride tetrahydrate, CuCl2 4H2O. (a) How many moles of CuCl2 4H2O were measured out? (b) How many moles of Cl ions are present in the sample? (c) How many H2O molecules are present in the sample? (d) What fraction of the total mass...
Mon Oct 01, 2018 10:38 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Formula Units
Replies: 6
Views: 8761

### Re: Formula Units

From my best understanding a formula unit refers to a group of atoms that are bonded ionically while a molecule refers to a group of atoms that are bonded covalently, but please feel free to correct me as I am still not 100% sure of this myself
Mon Oct 01, 2018 10:04 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Exercise E9
Replies: 3
Views: 171

### Re: Exercise E9

So if something has some prefix-hydrate does that always mean that there is a H20 attached?