## Search found 60 matches

Sun Mar 18, 2018 8:44 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Cell Potential for Concentration Cells
Replies: 1
Views: 150

### Re: Cell Potential for Concentration Cells

yes it is. I think it is because you are only using one type of ion/metal and the current is caused by a difference in concentration.
Sun Mar 18, 2018 8:43 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Delta G at equilibrium
Replies: 1
Views: 237

### Re: Delta G at equilibrium

at equilibrium the total change in entropy is 0, so delta g would be zero.
using the formula delta g= deltaH - Temp(deltaS), at Tb or Tf, deltaH=deltaS*T, meaning that delta g would be zero.
Sun Mar 18, 2018 8:39 am
Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
Topic: Electrolytic cells vs Galvanic Cells
Replies: 3
Views: 637

### Re: Electrolytic cells vs Galvanic Cells

electrolytic cell converts electric energy into chemical energy (need external power source to drive current). a galvanic cell converts chemical energy into electrical energy.
Sun Mar 18, 2018 8:37 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Reducing power
Replies: 2
Views: 3035

### Re: Reducing power

if e cell is very positive, it means the element has high oxidizing power because it is able to be reduced very easily.

if e cell is very negative, it means the element has high reducing power because it is able to be oxidized very easily (the reverse reaction, in this case oxidation, is favored).
Sun Mar 18, 2018 8:36 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Galvanic Cells
Replies: 2
Views: 219

### Re: Galvanic Cells

I think we only need to distinguish between a galvanic/voltaic and a concentration cell.
Sun Mar 18, 2018 8:35 am
Forum: General Rate Laws
Topic: rate law
Replies: 6
Views: 557

### Re: rate law

the only thing you would have to take into account the coefficient of the product is the unique rate
Tue Mar 13, 2018 10:20 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalysts
Replies: 2
Views: 164

### Catalysts

Will a catalyst appear in the overall reaction or the rate law?
Fri Mar 09, 2018 7:51 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Equations
Replies: 4
Views: 392

### Re: Equations

there are certain equations that we are expected to know not on the constants sheet I think----I believe these are more intuitive or can be easily derived.
Fri Mar 09, 2018 7:48 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Negative k? [ENDORSED]
Replies: 4
Views: 376

### Re: Negative k?[ENDORSED]

k itself cannot be negative but the slope involving k as with 1rst order or 0 order reactions can be negative.
Fri Mar 09, 2018 7:47 pm
Forum: Balancing Redox Reactions
Topic: Oxidation Number
Replies: 4
Views: 210

### Re: Oxidation Number

aside from set elements like 0, H, etc, the oxidation number can very depending on the compound. most of the time by knowing that 0 is 2- and H is +1 you can figure out the rest of the oxidation states.
Fri Mar 02, 2018 4:28 pm
Forum: Zero Order Reactions
Topic: Will we need to know how to derive equations? [ENDORSED]
Replies: 9
Views: 476

### Re: Will we need to know how to derive equations?[ENDORSED]

yes, I think we do.
Fri Mar 02, 2018 4:27 pm
Forum: First Order Reactions
Topic: Pseudo-First-Order Reactions [ENDORSED]
Replies: 3
Views: 196

### Re: Pseudo-First-Order Reactions[ENDORSED]

Fri Mar 02, 2018 4:27 pm
Forum: Zero Order Reactions
Topic: What role do coefficients play?
Replies: 3
Views: 168

### Re: What role do coefficients play?

coefficients don't directly relate to the order of the reaction. however, for the unique rate, coefficients do matter.
Sun Feb 25, 2018 12:39 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Electromotive Force
Replies: 3
Views: 216

### Re: Electromotive Force

when we are doing calculations it is good to note that we are always calculating the max
Sun Feb 25, 2018 12:34 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Importance of K
Replies: 2
Views: 129

### Re: Importance of K

it is important to note that k is for a given reaction at a fixed temperature. so when T increases, k also increases and vice versa.
Sun Feb 25, 2018 12:29 pm
Forum: Balancing Redox Reactions
Topic: Can the Hydroxide ion ever be reduced/oxidized?
Replies: 3
Views: 311

### Re: Can the Hydroxide ion ever be reduced/oxidized?

theoretically, I think that hydroxide ion can be reduced or oxidized, but I think it usually gains a proton to become h20.
Mon Feb 12, 2018 10:22 am
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: delta u
Replies: 2
Views: 145

### Re: delta u

internal energy cannot change without a temperature change; this means for isothermal reactions delta U is zero. this is because of the equation delta U=(3/2)nR(delta T)---it should be on the equation sheet as internal energy for an ideal gas.
Mon Feb 12, 2018 10:18 am
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: entropy of vaporization of water [ENDORSED]
Replies: 3
Views: 469

### Re: entropy of vaporization of water[ENDORSED]

at room temperature, water does have a entropy of vaporization---its like how a puddle evaporates---no one is boiling the puddle but eventually it becomes vapor. to solve these problems you usually 1) calculate entropy change for raising the temp to boiling point 2) calculate entropy of vaporization...
Mon Feb 12, 2018 10:16 am
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Entropy Definitions
Replies: 2
Views: 155

### Re: Entropy Definitions

I am actually not sure if there is a standard molar entropy of formation?---I thought it was just standard molar entropy for a substance...
for residual entropy, it is the entropy remaining when the temperature is 0K. unless the substance is a perfect crystal at 0k, it will have a residual entropy.
Thu Feb 08, 2018 10:52 am
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: 9.76
Replies: 2
Views: 170

### Re: 9.76

I also had the same question!
Thu Feb 08, 2018 10:51 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 9.61 sig figs
Replies: 2
Views: 177

### Re: 9.61 sig figs

I think the sig figs would just come from the amount of sig figs the book used for the standard Gibbs free energy of formations. in general though, for this unit, I don't think sig figs matter.
Thu Feb 08, 2018 10:49 am
Forum: Biological Examples (*DNA Structural Transitions, etc.)
Topic: problem 9.75
Replies: 2
Views: 444

### problem 9.75

what is the difference between cis and trans isomers?
Thu Feb 08, 2018 10:48 am
Forum: Phase Changes & Related Calculations
Topic: Phase changes with entropy?
Replies: 6
Views: 268

### Re: Phase changes with entropy?

yes, you do. the entropy increases when going from solid to liquid to gas and decreases in the opposite direction. you can use delta s= q(rev)/T. the q for a reversible reaction is equal to the enthalpy of fusion, vaporization etc. this will help you account for the entropy change during phase chang...
Thu Feb 01, 2018 7:51 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 9.47 B
Replies: 2
Views: 143

### Re: 9.47 B

delta s total will only be zero when the system is at equilibrium---for reversible isothermal expansion, it is like the system is at equilibrium, so you can assume delta s total is 0. since part b talks about irreversible expansion, the system is not at equilibrium. this means that delta s total is ...
Tue Jan 30, 2018 8:53 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 9.11 Chemical Equilibrium Question
Replies: 1
Views: 115

### 9.11 Chemical Equilibrium Question

When reading the book on pg 347 there is self test 9.18A: Confirm that liquid water and water vapor are in equilibrium when the temperature is a 100 degree C and the pressure is 1 atm. Data are available in Table 8.3 and 9.2. Does anyone know how to solve this? I understand the concept but I don't g...
Sun Jan 28, 2018 7:58 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Question 9.13
Replies: 1
Views: 81

### Question 9.13

In the corrected solutions manual, for calculating the change in entropy due to temperature, the manual states that Cv,m is equal to (5/2)R. Isn't heat capacity at a constant volume for an ideal gas 3/2R? Did they mean to say to use heat capacity at constant pressure? Could someone share their work ...
Fri Jan 26, 2018 11:13 pm
Forum: Phase Changes & Related Calculations
Topic: 8.41
Replies: 6
Views: 312

### Re: 8.41

for these types of problems, I would highly encourage drawing a diagram---this helps you keep track of the state of the substance at hand so you now the correspond specific heat capacity. since ice melts into water before the water raises temperature, you need to use the specific heat capacity of wa...
Fri Jan 26, 2018 11:12 pm
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: Box 9.1 Absolute Zero
Replies: 2
Views: 142

### Re: Box 9.1 Absolute Zero

Usually if he wants us to know a specific table, he makes sure to point it out on the chapter review sheet---since this box wasn't specifically mentioned, I'm sure you don't have to memorize it.
Fri Jan 26, 2018 11:10 pm
Forum: Calculating Work of Expansion
Topic: 8.93
Replies: 3
Views: 141

### Re: 8.93

when its a combustion reaction, I generally assume the water is in a liquid state.
Fri Jan 26, 2018 11:07 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.99
Replies: 3
Views: 196

### Re: 8.99

ZnCl2 is aq, which means you can think of it as zn 2+ ions and 2 cl- ions (in the solution they appear as ions anyway). look up the enthalpies of formation for these two ions (these are in the book).
Thu Jan 18, 2018 12:01 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Gas in a piston with regards to pressure
Replies: 3
Views: 179

### Re: Gas in a piston with regards to pressure

I agree---if gas in a piston is doing work, it means its pushing the piston, therefore increasing the volume and decreasing the overall pressure. I don't know exactly why T is constant (besides looking at PV=nRT), but maybe it has to do with system vs surroundings? I also don't know for sure if addi...
Thu Jan 18, 2018 11:56 am
Forum: Calculating Work of Expansion
Topic: Homework 8.11
Replies: 8
Views: 459

### Re: Homework 8.11

as a note, for this particular test, I think it was mentioned that we don't need to know calculations for problems concerning reversible, isothermal expansion
Thu Jan 18, 2018 11:52 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.67 Enthalpy of Formation
Replies: 2
Views: 120

### Re: 8.67 Enthalpy of Formation

The enthalpy of formation will be different as we are using bond enthalpies to estimate. While the bond enthalpies for diatomic molecules are accurate (since they are measured for these molecules), the other bond enthalpies are simply estimates---they are found by averaging the data gathered from ma...
Fri Jan 12, 2018 3:41 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: tables in chapter 8
Replies: 5
Views: 253

### Re: tables in chapter 8

I think the only thing we will need to know are the standard states for common reactants like hydrogen, oxygen, etc. all other values should be provided.
Fri Jan 12, 2018 3:39 pm
Forum: Administrative Questions and Class Announcements
Replies: 6
Views: 377

I think what she means (as this was the same for me too), if you do you homework in pencil for example, get something wrong and correct it in pen, and turn in that marked up homework, you still get full credit.
Fri Jan 12, 2018 3:36 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Different Molar Heat Capacities For Gases
Replies: 5
Views: 350

### Re: Different Molar Heat Capacities For Gases

I think when the volume is not constant (like with a piston), you need to take into account work (to move the piston?). im not quite sure though.
Thu Dec 07, 2017 1:00 pm
Forum: Conjugate Acids & Bases
Topic: Weak Acids/Bases and conjugate Bases/acids
Replies: 3
Views: 246

### Re: Weak Acids/Bases and conjugate Bases/acids

general info: a high value of ka or kb correlates with a strong acid or base since the products are heavily favored. a low value of ka or kb correlates with a weak acid or base since the reactants are favored. ka*kb=Kw=10^-14 If its a weak acid, then its ka will be quite small; because Ka*Kb equals ...
Thu Dec 07, 2017 12:52 pm
Forum: Conjugate Acids & Bases
Topic: HW 12.33?
Replies: 1
Views: 160

### HW 12.33?

I part A, but can someone please explain parts B and C to me? In particular, I don't understand the solution manuals work for part b (why do you multiply by 500ml/5ml?).
Sun Dec 03, 2017 8:57 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Question 11.89 Part A
Replies: 2
Views: 198

### Question 11.89 Part A

Why does the answer state that 2A forms B + C. Where did they get 2A from the graph?
Sun Dec 03, 2017 6:18 pm
Forum: Lewis Acids & Bases
Topic: Bronsted vs Lewis
Replies: 6
Views: 368

### Re: Bronsted vs Lewis

if im correct a bronsted base is a proton acceptor and a bronstead acid is a proton donor.
a lewis acid is an electron donor and a lewis base is an electron acceptor.
Sun Dec 03, 2017 6:15 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 11.73 Concept Question
Replies: 3
Views: 204

### Re: 11.73 Concept Question

when you decrease the volume and that results in an increase in pressure, the reaction will go toward the side with less mols (bc that has lower pressure in terms of concentration).
when you increase the pressure in terms of inert gas, nothing happens.
Mon Nov 27, 2017 6:12 pm
Forum: Naming
Topic: Alphabetical Order
Replies: 2
Views: 160

### Re: Alphabetical Order

i think the order only matters when you are naming; when you are writing the equation the order of the ligands doesnt matter. when writing the name of the compound you must list the ligands in alphabetical order.
Mon Nov 27, 2017 6:10 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Writing reaction quotient or equilibrium expression
Replies: 5
Views: 246

### Re: Writing reaction quotient or equilibrium expression

it depends on what the question is asking. if the states are all aqueous, you will need to write concentrations, so use brackets. if it is a gas you can write it as a partial pressure using P or as a concentration using brackets---this will depend on what the question is asking and the information i...
Mon Nov 27, 2017 6:08 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE Box
Replies: 1
Views: 129

### Re: ICE Box

the change for the reactant should be negative if the reactant is turning into product.
Mon Nov 27, 2017 6:07 pm
Forum: Student Social/Study Group
Topic: Is it me?
Replies: 3
Views: 386

### Re: Is it me?

me too for sure----there's just so much content and all of it is new for me since i never took Ap chem.
Sun Nov 19, 2017 8:23 pm
Forum: Hybridization
Topic: Hybridization character (Problem 4.43)
Replies: 1
Views: 139

### Hybridization character (Problem 4.43)

Why would the bond angle increase when the s-character of a hybrid orbital increases? What does it mean to say "the s-character of a hybrid orbital increases"? How does s-character increase?
Sun Nov 19, 2017 7:47 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Double bonds vs. single bonds
Replies: 4
Views: 264

### Re: Double bonds vs. single bonds

the only thing that affects the bond angle in the VSEPR are lone pairs---the more lone pairs on the central atoms, the lesser the angle because the lone pairs push the bonding pairs closer together. bond multiplicity does not matter.
Sun Nov 19, 2017 7:45 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Si02 VSEPR
Replies: 2
Views: 1114

### Re: Si02 VSEPR

Since the electron arrangement is linear and on either side of the Si are 0 atoms, the dipole moments cancel (dipole moments are formed when there is a difference in electronegativity between the two atoms). this means the molecule is non polar.
Sun Nov 12, 2017 3:58 pm
Forum: Ionic & Covalent Bonds
Topic: Bond Strength
Replies: 1
Views: 193

### Re: Bond Strength

i don't quite understand the formatting of your question so i will answer in terms of general concepts in general...anions are larger than the normal atoms bc you add an extra electron which creates more electron to electron repulsion and makes the atom larger. cations are smaller than normal atoms ...
Sun Nov 12, 2017 3:53 pm
Forum: Lewis Structures
Topic: atomic structure of HOCO
Replies: 8
Views: 430

### Re: atomic structure of HOCO

i think the formula is written as HOCO to emphasize the order in which the atoms are bonded (which is why its not CH02 or something).
Sat Nov 04, 2017 8:50 pm
Forum: Bond Lengths & Energies
Topic: Bond Lengths [ENDORSED]
Replies: 8
Views: 613

### Bond Lengths[ENDORSED]

Why are multiple bonds shorter than a single bond between the same two elements?
Sat Nov 04, 2017 6:03 pm
Forum: Resonance Structures
Topic: Bonds
Replies: 4
Views: 291

### Re: Bonds

Keep in mind the number of valence electrons. If your atoms needs a lot more valence electrons to complete its octet, most likely you will be using double or even triple bonds. Atoms like Cl with almost an octet will only need single bonds. It is fine to use just single bonds. Some lewis structure c...
Sat Nov 04, 2017 5:56 pm
Forum: Administrative Questions and Class Announcements
Topic: 14B and 14BL
Replies: 3
Views: 272

### Re: 14B and 14BL

I think its fine to take 14B and 14BL in the same quarter; from what I know, its just not recommended to take 14BL and 14C together.
Thu Oct 26, 2017 7:40 pm
Forum: Trends in The Periodic Table
Topic: Electron Affinity vs Electronegativity
Replies: 2
Views: 1004

### Re: Electron Affinity vs Electronegativity

Essentially they are the same thing. Things with high, positive electron affinity have high electronegativity. Electron affinity is the energy released when an electron is added to a gas phase atom; when the energy is positive is means that the atom "wants" the electron and when its negati...
Tue Oct 24, 2017 12:42 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Core vs Valence Electrons
Replies: 2
Views: 207

### Core vs Valence Electrons

On pg 44 of the book, it states that an atom has an inner core consisting of electrons in filled orbitals that around surrounded by valence electrons, which are the electrons in the outermost shell. Is the "core" the last noble gas or does it also consist of e- in the last filled orbital? ...
Tue Oct 24, 2017 10:47 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: principal quantum numbers
Replies: 2
Views: 201

### principal quantum numbers

I understand that when n, the principal quantum number, increases, the size of the shell of the atom also increases. But, why do increasing values of n also corresponding to increasing energy of the orbital?
Thu Oct 19, 2017 10:46 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Replies: 5
Views: 367

Hi Rachel, We use a negative sign in this equation because the energy of an electron completely removed from an atom is 0; therefore, as it falls and emits a photon, its energy becomes more and more negative. so the energy of an electron you calculate at each energy level will be negative. when you ...
Thu Oct 19, 2017 10:42 am
Forum: Photoelectric Effect
Topic: Unexpected Result [ENDORSED]
Replies: 4
Views: 399

### Re: Unexpected Result[ENDORSED]

Hi Rachel, You are right---if light mirrored a wave, changing the intensity, or the amplitude of the wave, should have increased the energy of the wave and booted off an electron. However, in this instance, light is behaving light a particle. This means that changing the intensity, or the number of ...
Thu Oct 05, 2017 1:36 pm
Forum: Molarity, Solutions, Dilutions
Topic: G5- moles of Na [ENDORSED]
Replies: 5
Views: 510

### Re: G5- moles of Na[ENDORSED]

You are correct to say there are 2 atoms of Na in NA2(C03). However, I would think about that a bit differently. What this really means is that for every mole of sodium carbonate, you have 2 mols of Na; the ratio of Na to sodium carbonate is 2:1. So, to get a certain number of moles of Na, you need ...
Thu Oct 05, 2017 1:28 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: E1
Replies: 6
Views: 842

### Re: E1

This problem is asking you for the length of the fiber---I imagine the fiber to be all the Ag atoms lined up in a row. The length each atom contributes to the total fiber length is its diameter. (eg: if you had 2 atoms each with a diameter of 2cm and you wanted to make a fiber, the fiber would be 4c...