## Search found 58 matches

Wed Mar 14, 2018 11:38 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: 2nd law
Replies: 2
Views: 348

### Re: 2nd law

I don't think we have to do that. I think we can just say that entropy of the universe is greater than 0 for a spontaneous process and deltaS = q/t
Wed Mar 14, 2018 11:27 pm
Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
Topic: Electrolysis Anode and Cathode
Replies: 2
Views: 305

### Re: Electrolysis Anode and Cathode

The anode is the one with the lower reduction potential. I don't know if this helps, but this is basically because the reduction potential is showing you what it would be if that element was the one that was reduced, but since the compound is oxidized, we would flip the equation, which would also fl...
Tue Mar 13, 2018 9:17 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 15.63 How to know what A is
Replies: 7
Views: 500

### 15.63 How to know what A is

Can someone explain how you would know what A is in these types of problems? In the solutions manual for this problem at the end of the set up for the problem, they put in -0.59 and I'm assuming that this is from ln A from the equation we're supposed to use, but I'm not sure how we would go about so...
Sun Mar 11, 2018 8:30 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Rate Constants, Special EQ Situation?
Replies: 1
Views: 146

### Re: Rate Constants, Special EQ Situation?

no the rate of reaction will be equal at equilibrium, but the rate constant will not change (it won't be equal for the forward and reverse reaction). Also I think temperature is what causes the rate constant to change. Hope that helps.
Tue Mar 06, 2018 8:50 pm
Forum: General Rate Laws
Topic: Products and Rate Law
Replies: 3
Views: 239

### Re: Products and Rate Law

No you wouldn't include C because it is a product. Your rate law is dependent on your reactants.
Tue Mar 06, 2018 8:48 pm
Forum: Administrative Questions and Class Announcements
Topic: review session schedule?
Replies: 2
Views: 199

### Re: review session schedule?

yup it's on his website under Important Final Exam Information
Sat Mar 03, 2018 5:03 pm
Forum: General Rate Laws
Topic: Integrated Rate Law Units
Replies: 4
Views: 321

### Re: Integrated Rate Law Units

I think mol/L is more common, but I think you can use anything as long as it matches.
Sat Mar 03, 2018 10:31 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Step Speed
Replies: 3
Views: 202

### Re: Step Speed

I'm not entirely sure about the first part of the question, but as for the second part, I think there shouldn't be multiple slow steps.
Fri Mar 02, 2018 10:21 pm
Forum: Zero Order Reactions
Topic: Relation between rate law and zero order [ENDORSED]
Replies: 3
Views: 237

### Re: Relation between rate law and zero order[ENDORSED]

Yup you can always make that connection because if you were to look at it using the formula, you see that like it becomes [CO]^0 which would be 1. So in this example it would look somewhat like Rate = k [NO2]^2 (1) and the 1 would come from the CO which is 0 order. Hopefully that helps!
Sun Feb 25, 2018 10:36 pm
Forum: Calculating Work of Expansion
Topic: Midterm 4A
Replies: 3
Views: 238

### Re: Midterm 4A

you would use w = -P deltaV because we know that this is an irreversible isothermal reaction. After we find work using that equation we would multiply it by the conversion between J and L*atm.
Sun Feb 25, 2018 9:36 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: Importance of K
Replies: 2
Views: 170

### Re: Importance of K

k is the rate constant. It links the reaction rate with the pressures or concentrations of the reactants.
Mon Feb 19, 2018 3:49 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: 14.27
Replies: 6
Views: 420

### 14.27

Using data in Appendix 2B, calculate the standard potential for the half-reaction U4+ + 4e ---> U

I understand that we need to use the standard potential from appendix 2B, but why do we first need to calculate delta G? Is it because the standard potential is an intensive property?
Sun Feb 18, 2018 10:48 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Inert Conductor
Replies: 3
Views: 165

### Re: Inert Conductor

An inert conductor basically allows electron flow from the anode to a cathode without contributing to the electron flow itself. It's only used when a solid conductor isn't present.
Sun Feb 18, 2018 12:31 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagrams
Replies: 2
Views: 157

### Re: Cell Diagrams

If you have a metal, then you won't need an inert conductor like Platinum. But in cases like this, where you only have aqueous compounds and only nonmental solids, you would need platinum so that there would be a transfer of electrons. I hope this helps!
Sun Feb 18, 2018 12:22 am
Forum: Balancing Redox Reactions
Topic: Test 2
Replies: 5
Views: 276

### Re: Test 2

I think we will need to know how to come up with the half reactions but we will be given the E values when we need them.
Sat Feb 10, 2018 10:12 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Stability in Gibbs standard free energy of formation
Replies: 2
Views: 576

### Re: Stability in Gibbs standard free energy of formation

I think that's true.
Sat Feb 10, 2018 10:10 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: cell diagram (hw14.11)
Replies: 3
Views: 205

### Re: cell diagram (hw14.11)

so in cases where our cell is not using conducting metals, you'll need to add an inert conductor, and the most common is platinum. So I think it's safe to assume that if we ever see Pt in a cell diagram we can say it is being used to allow electron flow without contributing to the reaction itself. I...
Sat Feb 10, 2018 5:24 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Derivations of Equations
Replies: 5
Views: 350

### Re: Derivations of Equations

I don't think so. I think he said we don't have to in class.
Sat Feb 03, 2018 5:14 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: ΔS(universe)
Replies: 6
Views: 380

### Re: ΔS(universe)

I think the entropy of the universe can only increase. I'm not sure how to explain it, but I know it can't decrease.
Sat Feb 03, 2018 5:12 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 9.65
Replies: 6
Views: 349

### Re: 9.65

As I understand it, we can calculate the standard entropies of formation for each compound and whichever is lowest (in this case, it would be PCl5) would be the one that is less stable.
Sat Feb 03, 2018 5:02 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 9.52
Replies: 3
Views: 227
If deltaS is positive and deltaH is positive, that would be an endothermic reaction, but it would become spontaneous at high temperatures. This is because G = H - (delta T x S), so we would want out delta T x S to be very big because that would be the only way G could be negative because when G is n...
Tue Jan 23, 2018 3:47 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Why is enthalpy a state function? Why is heat not a state function?
Replies: 5
Views: 3161

### Re: Why is enthalpy a state function? Why is heat not a state function?

By paths taken it refers to how you got from one state to another. Like if you wanted to go from the solid state to a gas state, how you got from a solid to a gas would be the pathway. Like whether you went from solid to liquid and then finally to gas, or from the a solid directly to gas would be a ...
Tue Jan 23, 2018 3:42 pm
Forum: Phase Changes & Related Calculations
Topic: HW 8.31
Replies: 3
Views: 264

### HW 8.31

For part a, the pressure is held constant. I know we are multiplying by the number of moles of Kr by the change in temperature but i just don't understand where they are getting the rest. When I checked the solution manual for part a, they were multiplying the change in temperature by the number of ...
Tue Jan 23, 2018 3:37 pm
Forum: Phase Changes & Related Calculations
Topic: HW 8.1
Replies: 2
Views: 166

### Re: HW 8.1

So a thermos essentially makes sure that there is no transfer of heat or matter from the system (inside of the thermos) and the surroundings. So because there would be no exchange of matter or heat, it's an isolated system. Hope that helps!
Sun Jan 21, 2018 1:13 pm
Forum: Phase Changes & Related Calculations
Topic: Test 1 translation and rotational energy?
Replies: 1
Views: 140

### Re: Test 1 translation and rotational energy?

No I don't think he will because he never covered it.
Sun Jan 21, 2018 1:12 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Why is enthalpy a state function? Why is heat not a state function?
Replies: 5
Views: 3161

### Re: Why is enthalpy a state function? Why is heat not a state function?

Enthalpy is a state function because it depends on the state, not necessarily the path, while heat does not. For example, if you go from a solid to a gas, whether you go directly from a solid to a gas or whether you go from a solid to a liquid to a gas, the enthalpy would be the same. It doesn't dep...
Sun Jan 21, 2018 1:08 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Reaction Enthalpy units
Replies: 1
Views: 62

### Re: Reaction Enthalpy units

I think it's kJ/mol
Sat Jan 20, 2018 3:50 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Perfect System
Replies: 1
Views: 129

### Re: Perfect System

yup I think we do.
Sun Jan 14, 2018 6:42 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.57
Replies: 1
Views: 124

### 8.57

the question wants us to find the reaction enthalpy for the hydrogenation of ethyne to ethane which is C2H2 + 2H2 --> C2H6. Then it gives us the enthalpies of each element. What I did was use the sum of the products - the sum of the reactants, but the answer book did something else and the answer wa...
Sun Jan 14, 2018 6:36 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: U=q or U=q+w?
Replies: 3
Views: 222

### Re: U=q or U=q+w?

so U is always U=q+w, so as I understand it, U=q when there is no work being done by or on the system.
Sun Jan 14, 2018 6:33 pm
Forum: Phase Changes & Related Calculations
Topic: problem 8.29
Replies: 2
Views: 189

### Re: problem 8.29

You would expect NO2 to have the higher molar heat capacity since it has more atoms within the molecule, and more atoms within the molecule means more bond variation, so it takes more energy to break the bonds of NO2 than it does to break the bonds of NO.
Sun Jan 14, 2018 6:30 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: problem 8.47
Replies: 1
Views: 134

### Re: problem 8.47

So to find delta U, you add the work and the energy as heat. So basically you would do -15 kJ + 22kJ and you would get your delta U to be 7 kJ.
Sun Dec 10, 2017 1:13 am
Forum: Trends in The Periodic Table
Topic: Electron shielding
Replies: 2
Views: 309

### Re: Electron shielding

So I think of it in a weird way. Like I think of it as akin to a performer and a crowd. So say someone is performing and there's a crowd around him. The closer you are to the performer, the more you can see, the more captivated you are and it's harder to pull you away from the performer. Now say the...
Sat Dec 09, 2017 7:50 pm
Forum: Einstein Equation
Topic: Test 2 #5
Replies: 3
Views: 323

### Re: Test 2 #5

But when I did that I got 2.92x10^15 for the energy and 4.41x10^48 for the frequency?
Sat Dec 09, 2017 7:47 pm
Forum: Naming
Topic: Naming
Replies: 9
Views: 642

### Re: Naming

If the whole compound is either positively or negatively charged (it would be at the end of the compound). If the compound has no charge then it won't be called an ion.
Sat Dec 09, 2017 7:45 pm
Forum: Einstein Equation
Topic: Test 2 #5
Replies: 3
Views: 323

### Test 2 #5

5. Determine the frequency of the emitted photon when an electron in a hydrogen atom drops from the quantum state of n=3 to n=1.

The answer is apparently 2.92 x 10^15. Could someone explain how we would get that?
Sat Dec 09, 2017 5:13 pm
Forum: Naming
Topic: Test 4 # 4 Name
Replies: 1
Views: 268

### Re: Test 4 # 4 Name

I think it would be diammine not bisammine, but the rest of the name is correct. It wouldn't be bisammine because NH3 is neither a polydentate nor a ligand that already has the di/tri/tetra etc. in it's name.
Sat Dec 09, 2017 5:11 pm
Forum: Bronsted Acids & Bases
Topic: 12.131
Replies: 1
Views: 201

### Re: 12.131

(a) So when your body produces lactic acid in the muscles, more hemoglobin is produced and the O2 in hemoglobin is released and reacts with the H+ from the lactic acid, so the concentration of HbO2 is decreased. As I understand it, this is essentially done to help our body return back to equilibrium...
Wed Dec 06, 2017 5:28 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: ICE Chart [ENDORSED]
Replies: 9
Views: 603

### Re: ICE Chart[ENDORSED]

We can, but I don't think we will have a problem with more than 2 products and 2 reactants mainly because it would get complicated.
Mon Dec 04, 2017 11:34 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Pi and sigma bonds [ENDORSED]
Replies: 7
Views: 450

### Re: Pi and sigma bonds[ENDORSED]

If there's resonance, do the sigma and pi bonds become delocalized?
Mon Dec 04, 2017 11:19 am
Forum: Polyprotic Acids & Bases
Topic: Polyprotic pH approximation
Replies: 1
Views: 549

### Re: Polyprotic pH approximation

I think it depends on whether the polyprotic acid is initially a strong acid. Like in the problem in part c, the acid is H2S which is a strong acid, but HS is a weak acid, so in that case you could ignore the second deprotonation because strong acids dissociate almost completely. However, in the cas...
Sun Dec 03, 2017 4:51 pm
Forum: Naming
Topic: Naming Coordination Compounds
Replies: 8
Views: 483

### Re: Naming Coordination Compounds

yup
Mon Nov 27, 2017 11:39 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordination Number
Replies: 1
Views: 134

### Re: Coordination Number

it's related to the number of bonds.
Mon Nov 27, 2017 11:34 pm
Forum: Naming
Topic: Naming Coordination Compounds
Replies: 8
Views: 483

### Re: Naming Coordination Compounds

If the overall compound is an anion, then you add the -ate, but if it's a cation then you don't add the -ate.
Mon Nov 20, 2017 8:19 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: HW 4.75
Replies: 2
Views: 251

### Re: HW 4.75

It's polar because the electrons are not shared equally. Oxygen is very electronegative while Hydrogen is not, so the electrons will spend more time around Oxygen than the Hydrogens and this will cause Oxygen to have a slight negative charge and Hydrogens to have a slight positive charge, which resu...
Mon Nov 20, 2017 8:13 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Chapter 11 Reading
Replies: 1
Views: 177

### Re: Chapter 11 Reading

That refers to Gibbs free energy and the way it's used I think it's just telling us if the reaction is exothermic or endothermic. (Basically whether is energy released or absorbed).
Mon Nov 20, 2017 7:04 pm
Forum: Naming
Topic: H2O in Coordination compounds
Replies: 2
Views: 335

### Re: H2O in Coordination compounds

I think if it's referred to as diaqua it's OH2 but if it's referred to as hydrate then it's H2O.
Mon Nov 13, 2017 9:48 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Organic vs inorganic molecules
Replies: 3
Views: 270

### Re: Organic vs inorganic molecules

Organic molecules must have carbon and hydrogen and along with carbon and hydrogen they may contain nitrogen, oxygen and phosphorus. I could be wrong, so if anyone could confirm this that would be great, but i think the difference is that with most organic molecules, you have a carbon backbone.
Fri Nov 10, 2017 4:44 pm
Forum: Lewis Structures
Topic: Lewis structure
Replies: 4
Views: 336

### Re: Lewis structure

The atom with the lowest ionization energy will be in the center. I'm not too sure what you mean by "when they will alternate" though sorry/
Fri Nov 10, 2017 4:42 pm
Forum: Lewis Structures
Topic: Lewis acids and bases [ENDORSED]
Replies: 3
Views: 340

### Re: Lewis acids and bases[ENDORSED]

A lewis acid accepts an electron pair and a lewis base donates an electron pair.
Thu Nov 02, 2017 10:10 pm
Forum: Ionic & Covalent Bonds
Topic: Chemical bonds create lower energy?
Replies: 4
Views: 272

### Re: Chemical bonds create lower energy?

I think it's because when atoms bond, energy is released, so in general when bonded they have less energy than when separate.
Mon Oct 30, 2017 8:25 pm
Forum: Trends in The Periodic Table
Topic: 2-43e tungsten e- config
Replies: 1
Views: 191

### Re: 2-43e tungsten e- config

That wouldn’t be the ground state because it would have too many electrons. You only need 74 electrons but if [Xe]4f^14 5d^5 6s^2 is your configuration you would have 75 electrons. Also I think the only times you make it into d^5 by removing an electron from the s orbital is for chromium. So basical...
Fri Oct 27, 2017 8:47 pm
Forum: Resonance Structures
Topic: Resonance in SO4
Replies: 5
Views: 481

### Re: Resonance in SO4

Also I think we want the central atom to have a formal charge be zero, or at least as close to 0 as it can get. If we made all the oxygen atoms have a formal charge of 0, we would have the total formal charge of -2, but the structure would be less stable since the formal charge of sulfur would becom...
Wed Oct 25, 2017 8:37 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Electron Configuration
Replies: 2
Views: 248

### Re: Electron Configuration

I think it's because the oribital are in order of increasing energy, so we would write 3d before 4s since 3d is a less energy orbital than a 4s orbital.
Wed Oct 18, 2017 9:47 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: s-,p-, d-, and f- orbitals
Replies: 7
Views: 503

### Re: s-,p-, d-, and f- orbitals

As I understand it, the s, p, d, and f orbitals essentially tell us where we are most likely to find electrons for a certain atom. The number of electrons varies based on level (s can hold max 2, p can hold a maximum of 6, d can hold a maximum of 10, and f can hold a maximum of 14) as the size of th...
Wed Oct 18, 2017 9:04 pm
Forum: *Shrodinger Equation
Topic: Atomic Orbitals and Energy [ENDORSED]
Replies: 3
Views: 372

### Re: Atomic Orbitals and Energy[ENDORSED]

There is some overlap between the orbitals as the orbitals are three dimensional and also in different shapes, but in general, the energy will increase. Like the p orbital would be higher in energy than the s orbital.
Thu Oct 05, 2017 9:58 pm
Forum: Empirical & Molecular Formulas
Topic: Combustion Analysis
Replies: 5
Views: 424

### Re: Combustion Analysis

Other elements can be involved in a combustion reaction. Usually it's that O2 is a reactant and the products must include CO2 and H2O. If there are other elements involved, we would be told in the problem.
Thu Oct 05, 2017 9:17 pm
Forum: Significant Figures
Topic: 3 Sig Figs 1795.507? [ENDORSED]
Replies: 5
Views: 536

### Re: 3 Sig Figs 1795.507?[ENDORSED]

I think you could round it to 1800 and then put it into scientific notation so that it would be 1.80 x 10^3

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