## Search found 51 matches

Fri Mar 16, 2018 10:34 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: State Properties
Replies: 5
Views: 487

### Re: State Properties

Heat capacity is the energy required to raise the temperature of a substance by 1 degree C, and it is an extensive property. Specific heat capacity is the energy required to raise one gram of substance by 1 degree C, and is an intensive property. The difference lies in that one in extensive and one...
Fri Mar 16, 2018 10:32 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: State Properties
Replies: 5
Views: 487

### Re: State Properties

heat capacity is q=c(delta t) specific heat capacity is q=mc(delta t) basically specific heat capacity is specific to your sample because it incorporates mass. To clarify, these are the equations you would use to find q using heat capacity or specific heat capacity. The actual heat capacity and spe...
Fri Mar 16, 2018 10:24 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: closed vs isolated
Replies: 11
Views: 747

### Re: closed vs isolated

An example would be the expansion of a balloon. Say the pressure outside the balloon decreased, the volume of the balloon would increase as it expanded. However, it is still a closed system because the balloon never actually lost any matter, it just reacted to outside conditions.
Fri Mar 16, 2018 10:12 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Replies: 5
Views: 467

It could be either conceptual, such as just describing what it means, or he could make integrate it into an actual problem to test if we really understand what it entails. Question 5 dealt with an adiabatic process in a problem, so I'd say it's definitely fair game for the final.
Fri Mar 16, 2018 10:08 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Split of questions on the final
Replies: 3
Views: 402

### Re: Split of questions on the final

Agreed, during 14A with Lavelle his final was pretty evenly split. Also, the TA's mentioned that all material will be covered equally on the final (to an extent, as obviously we can't cover every single topic in one test).
Fri Mar 16, 2018 10:02 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Work and derivations
Replies: 2
Views: 311

### Re: Work and derivations

To clarify, if volume is constant but Pext is changing, would work still be done by the system? Such as if your lungs had 3L of air in them at 1 atm, then after you dive down under water the pressure is 2 atm but your lungs still remain at 3L. Could we just use w=-nRTln(P1/P2) to find work, or is it...
Fri Mar 16, 2018 9:52 pm
Forum: Calculating Work of Expansion
Topic: Different work problems?
Replies: 2
Views: 271

### Re: Different work problems?

You would use w=-Pext(deltaV) when pressure is constant, and w=-nRTln(V2/V1) when pressure is changing as well.
Thu Mar 15, 2018 10:11 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Practice final problem
Replies: 2
Views: 324

### Re: Practice final problem

How come the answer is 4390 C and not 4395 C, if they originally started at 25 C?
Thu Mar 15, 2018 10:05 pm
Forum: Phase Changes & Related Calculations
Topic: Helium
Replies: 1
Views: 244

### Re: Helium

Search up "helium melting exothermic" on google, and Dr. Lavelle's Chemistry Community explanation is the first answer to come up. It's really long and complicated so I won't attempt to copy it down, but it should help out!
Thu Mar 15, 2018 9:53 pm
Forum: Phase Changes & Related Calculations
Topic: Internal Pressure in Reversible vs Irreversible Processes
Replies: 1
Views: 237

### Re: Internal Pressure in Reversible vs Irreversible Processes

We don't actually need to know how much the internal energy changed, as it will be proportional to the change in volume. Because is it a gas, P1V1=P2V2. We will only ever have one unknown, so we can figure out how much the internal pressure has changed based on delta V.
Thu Mar 15, 2018 9:49 pm
Forum: Phase Changes & Related Calculations
Topic: Origin of Internal Energy
Replies: 2
Views: 315

### Re: Origin of Internal Energy

I don't think so, we never went over it in class and it isn't on the syllabus. At most I think we'd just need to know that they exist.
Thu Mar 15, 2018 9:44 pm
Forum: *Ethers
Topic: Nucleophile
Replies: 3
Views: 997

### Re: Nucleophile

Ok, so we essentially just look for the lewis base in the reaction. Thank you!
Thu Mar 15, 2018 9:34 pm
Forum: *Ethers
Topic: Nucleophile
Replies: 3
Views: 997

### Nucleophile

What is a nucleophile, and how would we determine what molecule is acting as one if we are given an equation?
Mon Feb 19, 2018 9:39 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Delta G= Wmax
Replies: 8
Views: 846

### Re: Delta G= Wmax

Scott Chin_1E wrote:Does Wmax usually occur when the system is at equilibrium?

No, at equilibrium Delta G and Ecell are equal to zero, and therefore work at equilibrium would be equal to zero. This makes sense, as at equilibrium there would be no electrons flowing between the anode and the cathode.
Mon Feb 19, 2018 9:27 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: anode?
Replies: 5
Views: 360

### Re: anode?

You can also remember that in a galvanic cell, the electrons flow from left to right. Since the oxidation is the process of losing electrons, it must occur in the left side of the cell, which is the anode.
Mon Feb 19, 2018 9:22 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Potential - Intensive Property
Replies: 2
Views: 189

### Re: Cell Potential - Intensive Property

Conceptually, it is an intensive property because the unit of voltage is V, which is the amount of joules consumed per charge of one coulomb (J/C). No matter how big the size of the sample or cell you have, the energy consumed by per coulomb will be the same as it's just a ratio.
Mon Feb 19, 2018 9:14 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: OH- ions
Replies: 1
Views: 117

### Re: OH- ions

The redox reaction is occurring in a basic (alkaline) environment, as we can tell by the OH- in the reaction. KOH (aq) is a very common alkaline solution and is the solution present in the anode.

Hope this helps!
Mon Feb 19, 2018 9:08 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Inert Electrode
Replies: 2
Views: 239

### Re: Inert Electrode

I don't think we would ever have a situation when both the reactant and the product are in solid form, as Dr. Lavelle stated that anytime something gets oxidized it will turn into an aqueous solution. For the purpose of our course I believe we only need to know when both the reactant and product are...
Mon Feb 19, 2018 9:04 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Platinum in Cell Diagrams
Replies: 1
Views: 154

### Re: Platinum in Cell Diagrams

We would use an inert conductor, such as platinum, when one of the half reactions have no conducting solids in the reactants or products. An example of this would be Fe 3+ (aq) going to fe 2+ (aq). Because there is no solid for the electrons to go through, we need to place one there that can conduct...
Sun Feb 04, 2018 2:04 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Change in Entropy of Universe
Replies: 3
Views: 287

### Re: Change in Entropy of Universe

Can you explain why delta S universe can be zero during a reversible process, but is always positive for a spontaneous process? I thought it was always positive no matter what.
Sun Feb 04, 2018 1:58 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: reversible vs irreversible
Replies: 3
Views: 271

### Re: reversible vs irreversible

Agree with Matthew above, work is definitely done in an irreversible process, it's just much smaller as the changes in the volume are much smaller than those in a reversible process, and occurs much more slowly.
Sun Feb 04, 2018 1:43 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Spontaneity
Replies: 4
Views: 251

### Re: Spontaneity

Like Dr. Lavelle said, sometimes you do not need to fully calculate delta G in order to determine if the reaction is spontaneous. Often if you know delta h and delta s then you can tell automatically if a reaction is spontaneous. For example, if delta h is positive and delta s is negative, we know t...
Sun Feb 04, 2018 1:32 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Equilibrium Value K
Replies: 3
Views: 247

### Re: Equilibrium Value K

Actually I think K can be any value, its just a ratio of products to reactants at equilibrium. When K>1 its favored to have more products than reactants at equilibrium, and visa versa when K<1. K=1 is really rare because you'd have to have exactly the same concentration of products and reactants.
Sun Feb 04, 2018 1:28 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: G at minimum
Replies: 6
Views: 262

### Re: G at minimum

How come the system isn't necessarily at equilibrium when delta G naught is zero?
Sun Feb 04, 2018 1:24 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Value of G
Replies: 4
Views: 206

### Re: Value of G

What exactly is G, and how does it differ from delta G in terms of what we use it for?
Sat Jan 20, 2018 8:18 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Molar Heat Capacity
Replies: 6
Views: 1441

### Re: Molar Heat Capacity

I don't think the specific heat capacities of NO and NO2 are the same, in fact I believe that of NO is slightly larger. This is due to the fact that even though NO2 has a larger molar heat capacity, one gram of NO is a higher percentage of its molar mass that 1 gram of NO2 is of its molar mass.
Sat Jan 20, 2018 7:54 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Work vs. Heat
Replies: 6
Views: 396

### Re: Work vs. Heat

Does the energy that gets transferred into heat always have to be equal to or greater than the energy converted into work, or can either be larger than the other?
Sat Jan 20, 2018 7:48 pm
Forum: Calculating Work of Expansion
Topic: Irreversible and Reversible Processes
Replies: 4
Views: 280

### Re: Irreversible and Reversible Processes

So if the difference is that reversible reactions occur at equilibrium, what makes a reaction that occurs at non-equilibrium irreversible?
Mon Jan 15, 2018 7:55 pm
Forum: Phase Changes & Related Calculations
Topic: Signs on energy changes
Replies: 3
Views: 245

### Re: Signs on energy changes

So in number 7, would it be endothermic because it is absorbing heat?
Mon Jan 15, 2018 7:46 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 3 Methods
Replies: 4
Views: 250

### Re: 3 Methods

How come with Hess' Law we subtract the enthalpies of the reactants from that of the products, but when calculating bond enthalpies we essentially subtract the products from the reactants?
Mon Jan 15, 2018 7:39 pm
Forum: Phase Changes & Related Calculations
Topic: Open/Closed/Isolated
Replies: 11
Views: 577

### Re: Open/Closed/Isolated

How do we distinguish between an isolated system and a closed system?
Sat Dec 09, 2017 10:00 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Shell, subshell, and orbital
Replies: 5
Views: 444

### Re: Shell, subshell, and orbital

For a value of l greater than 4, what would the orbital be? Are there orbitals beyond f orbitals that we don't cover in this class, or is it simply that any l that is 5 or above is considered an f orbital?
Sat Dec 09, 2017 9:55 pm
Forum: Hybridization
Topic: how to determine hybridization
Replies: 4
Views: 370

### Re: how to determine hybridization

In a case where the central atom is bonded to two outer atoms via double bonds, would the hybridization of the central atom be sp, because there are only two sites where the atoms are bonded, or sp3, because there are four bonds?
Sat Dec 09, 2017 9:52 pm
Forum: Bronsted Acids & Bases
Topic: Bronsted and Lewis Acids
Replies: 3
Views: 301

### Re: Bronsted and Lewis Acids

So does that mean that all acids are Lewis acids, but not all acids are Bronsted acids? And the same for bases.
Sat Dec 09, 2017 9:45 pm
Forum: Sigma & Pi Bonds
Topic: Delocalization
Replies: 3
Views: 297

### Re: Delocalization

Do delocalized pi bonds only occur in a molecule with a 6-carbon ring, or can they occur any time there are overlapping p orbitals?
Sat Dec 09, 2017 9:39 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Strength of an acid
Replies: 14
Views: 819

### Re: Strength of an acid

Then how come HF is a stronger base than HOH, even though fluorine is more electronegative than oxygen? Does the strength of an acid increase as we go across the periodic table?
Sun Dec 03, 2017 10:33 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Drawing Coordination Compounds
Replies: 5
Views: 678

### Re: Drawing Coordination Compounds

No, as long as all of the ligands are present and bonded to the metal, it doesn't matter where they are on the lewis structure.
Sun Dec 03, 2017 10:28 am
Forum: Naming
Topic: Iron v ferrate in coordination compound naming
Replies: 8
Views: 2061

### Re: Iron v ferrate in coordination compound naming

Wouldn't we only use ferrate if the compound is an anion? I think if the compound is neutral or a cation then we use iron, correct?
Sun Dec 03, 2017 10:26 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: 17.35 Chelating Complexes
Replies: 4
Views: 372

### Re: 17.35 Chelating Complexes

Is there any way to tell if a molecule is a chelating complex just by looking at the molecular formula? Or do we need to see the Lewis structure to be sure?
Sat Nov 18, 2017 10:45 pm
Forum: Hybridization
Topic: Filling the hybrid orbitals?
Replies: 12
Views: 854

### Re: Filling the hybrid orbitals?

For a molecule that has 2sp^2 hybridization like in C2H4 shown above, what is the difference between that and sp^2 hybridization? What does the first coefficient actually represent?
Sat Nov 18, 2017 10:39 pm
Forum: Hybridization
Topic: Difference between sigma and pi bonds?
Replies: 6
Views: 1262

### Re: Difference between sigma and pi bonds?

I know you can have multiple pi bonds, but can you have multiple sigma bonds? In all of our examples it seems that there is only ever one sigma bond.
Fri Nov 10, 2017 7:19 pm
Forum: Ionic & Covalent Bonds
Topic: Polar vs. Non-polar
Replies: 7
Views: 437

### Re: Polar vs. Non-polar

In order to determine if the bond itself is polar, we look at the difference in electronegativity of the elements involved along with the characteristics of these elements (does it dissolve in water, etc.). If asked if the entire molecule is polar or nonpolar, that is when we look at if the molecule...
Fri Nov 10, 2017 7:14 pm
Forum: Ionic & Covalent Bonds
Topic: Midterm
Replies: 6
Views: 570

### Re: Midterm

It was actually SiO2, but nevertheless it is still polar, as the difference in electronegativity was greater than 1.5.
Sat Nov 04, 2017 9:25 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: For the test vsepr and lewis
Replies: 3
Views: 230

### Re: For the test vsepr and lewis

How would we know when to call it trigonal pyramidal and when to call it tetrahedral?
Sat Nov 04, 2017 9:22 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Magnetic Quantum Number
Replies: 6
Views: 491

### Re: Magnetic Quantum Number

Is there any way for us to tell exactly what magnetic quantum number an electron would have within an orbital without doing an experiment? Will we ever be asked which magnetic quantum number an electron has?
Sat Oct 28, 2017 10:36 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: s- electrons vs p- electrons [ENDORSED]
Replies: 7
Views: 656

### Re: s- electrons vs p- electrons[ENDORSED]

Then how come even when the 4s orbitals are filled first, they still have a higher energy than the 3d orbital, hence why we write 3d before 4s?
Sat Oct 28, 2017 10:27 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Putting s orbital or p orbital first [ENDORSED]
Replies: 4
Views: 419

### Re: Putting s orbital or p orbital first[ENDORSED]

What about with Chromium and Copper, when the 4s orbital isn't completely filled and an electron gets transferred to the 3d orbital? Do we still list the 3d orbitals ahead of the 4s?
Sun Oct 15, 2017 12:16 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: H Equation [ENDORSED]
Replies: 6
Views: 503

### Re: H Equation[ENDORSED]

Also, is the only thing that would change in different equations for different elements the Rydberg constant? Or would the entire makeup of the quantum equation for that element be different from what we learned for hydrogen?
Sun Oct 15, 2017 12:07 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: H Equation [ENDORSED]
Replies: 6
Views: 503

### Re: H Equation[ENDORSED]

Are we only going to learn the quantum equation for Hydrogen, or are we expected to know it for others, such as carbon an oxygen?
Sat Oct 07, 2017 8:22 pm
Forum: Molarity, Solutions, Dilutions
Topic: Molarity unit [ENDORSED]
Replies: 11
Views: 1074

### Re: Molarity unit[ENDORSED]

What is the difference between molarity and molality?
Sat Oct 07, 2017 8:17 pm
Forum: Significant Figures
Topic: All students read this sig fig post [ENDORSED]
Replies: 131
Views: 17047

### Re: All students read this sig fig post[ENDORSED]

In a multistep problem, should we use sig figs with every step, or only when it comes to the final answer? Will we be penalized if we use more than the amount of sig figs in intermediate steps but have the correct amount for the final answer?