## Search found 60 matches

Sat Mar 16, 2019 9:10 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: concentration cell vs galvanic cell
Replies: 3
Views: 371

### Re: concentration cell vs galvanic cell

Angela Cong 3C wrote:Does a concentration cell always have to have a porous disk?

A concentration cell can have a salt bridge as well, its essentially the same as a porous disk but one of these is needed
Sat Mar 16, 2019 9:09 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Ecell Always Positive
Replies: 3
Views: 165

### Re: Ecell Always Positive

Is there a case where Ecell could be negative?
Sat Mar 16, 2019 9:07 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Platinum
Replies: 5
Views: 178

### Re: Platinum

Platinum is used in a cell diagram as an electrode when no other solids are present, it is added to either end of a cell diagram depending on where its needed
Sun Mar 10, 2019 12:01 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: test 2
Replies: 1
Views: 92

### Re: test 2

Delta G is positive in photosynthesis, photosynthesis requires light making it not spontaneous
Sun Mar 10, 2019 11:59 am
Forum: Van't Hoff Equation
Topic: Overview
Replies: 8
Views: 564

### Re: Overview

You can use the equation to find the K value at two different temperatures
Sun Mar 10, 2019 11:55 am
Forum: Van't Hoff Equation
Topic: Van't Hoff use
Replies: 13
Views: 1086

### Re: Van't Hoff use

You can use this equation to find a lot of things depending on how you decide to rearrange the equation, but you know you need to use if the reaction involves a temperature change
Sun Mar 03, 2019 2:03 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell diagrams and solids
Replies: 9
Views: 376

### Re: Cell diagrams and solids

More often than not the solid used is going to be platinum but you can also use graphite as a conducting solid
Sun Mar 03, 2019 2:01 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Does anyone know if test 2 will be curved?
Replies: 15
Views: 615

### Re: Does anyone know if test 2 will be curved?

Technically nothing in the class is curved, the tests are given a score but not a grade and then at the end of the quarter once everyone’s scores out of the total 500 for the class is known is when a grade is given
Sun Mar 03, 2019 1:55 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs Free Energy and Entropy
Replies: 6
Views: 512

### Re: Gibbs Free Energy and Entropy

It doesn’t always mean that entropy is lower, you could have different sign combinations for enthalpy and entropy causing the negative delta G
Sat Feb 23, 2019 3:46 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Test 3
Replies: 14
Views: 483

### Re: Test 3

Since it’s in the homework I would assume so
Sat Feb 23, 2019 3:44 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Salt Bridges
Replies: 3
Views: 144

### Re: Salt Bridges

They both have the same purpose so the question should tell you what’s used
Sat Feb 23, 2019 3:35 pm
Forum: Balancing Redox Reactions
Topic: Test 2 Material
Replies: 11
Views: 319

### Re: Test 2 Material

705170809 wrote:Do you think he will also have enthalpy and entropy questions imbedded in Gibbs questions, since Gibbs free energy contains a formula that requires both delta H and delta S?

I’m not really sure but it wouldn’t hurt to know it just in case
Sun Feb 17, 2019 1:01 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Monatomic VS Diatomic Gases and their C
Replies: 3
Views: 343

### Re: Monatomic VS Diatomic Gases and their C

Cp and Cv are different because Cp is used at constant pressure and Cv is used when volume is constant, they’re both calculated using R and some other number which should be given on the equations sheet
Sat Feb 16, 2019 5:09 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Entropy equations
Replies: 8
Views: 559

### Re: Entropy equations

Can someone please explain the derivation of deltaS = nRlnV2/V1 ? I do not understand why this can be used. This equation is used in an isothermal reaction so temperature is constant which means that deltaU is 0, this allows q=-w, because w=-nRTln(v2/v1) then q=nRTln(v2/v1), then, since deltaS=q/T,...
Sat Feb 16, 2019 5:05 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Changes in Pressure
Replies: 5
Views: 213

### Re: Changes in Pressure

Because the equation P1V1=P2V2 is true, you can manipulate it so P1/P2=V2/V1
Sat Feb 09, 2019 11:19 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Delta U
Replies: 3
Views: 139

### Re: Delta U

Delta U is the change in internal energy and its a state function so its only dependent on the end state, its just the difference between where you start and end up in terms of energy
Sat Feb 09, 2019 11:13 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Converting Celsius to Kelvin
Replies: 7
Views: 295

### Re: Converting Celsius to Kelvin

I think either works, the solutions manual for the seventh edition I’m pretty sure uses 273
Sat Feb 09, 2019 11:06 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Cv/Cp versus R
Replies: 4
Views: 233

### Re: Cv/Cp versus R

R is used for reversible reactions when temp is constant, usually like if you have deltaS=nRln(v2/v2), then use deltaS=nCvln(t2/t1) for a constant volume and a change in temp and then deltaS=nCpln(t2/t1) for a constant pressure and a change in temp
Thu Jan 31, 2019 6:06 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Changing Pressure
Replies: 6
Views: 313

### Re: Changing Pressure

Concentration is calculated by mol/L so if you change the volume it will cause a change in concentrations and therefore a shift in equilibrium, but if you dont change the volume and just pump in inert gas then the reaction will stay the same because none of the variables within the equation for conc...
Thu Jan 31, 2019 6:03 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Decreasing volume and chemical equilibrium
Replies: 8
Views: 372

### Re: Decreasing volume and chemical equilibrium

When volume is decreased it is most likely that that will cause pressure to increase, therefore causing the reaction to shift to the side with fewer moles
Thu Jan 31, 2019 5:59 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: closed vs isolated
Replies: 14
Views: 374

### Re: closed vs isolated

In a closed system, energy can be exchanged with the surroundings but not matter, the example used in class was a beaker that had been sealed, in an isolated system does not allow for heat or energy to be exchanged with the surroundings, a helpful way for me to think of it is to think of it similar ...
Fri Jan 25, 2019 10:49 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: State Properties
Replies: 6
Views: 155

### Re: State Properties

Their value cannot be determined based solely on their current state, the path taken must be considered, whereas something like enthalpy can be determined on its current state
Fri Jan 25, 2019 10:46 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: State properties
Replies: 3
Views: 131

### Re: State properties

Heat does not have state properties because it is not a state function meaning that heat relies on the ‘path taken’ where as enthalpy does not and its value is determined by its current state
Fri Jan 25, 2019 10:43 pm
Forum: Phase Changes & Related Calculations
Topic: Enthalpy and States
Replies: 8
Views: 292

### Re: Enthalpy and States

Yes, when calculating net enthalpy change, you will have to take into account enthalpy changes between states of matter
Sun Jan 20, 2019 9:41 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE calculation sig figs
Replies: 5
Views: 162

### Re: ICE calculation sig figs

Don't round any answers until you've reached the end of your work, then round off to as many sig figs as the equation used
Sun Jan 20, 2019 9:40 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Ionization and deprotonation
Replies: 3
Views: 55

### Re: Ionization and deprotonation

They are often used interchangeably because they are the same thing, although its more common to see ionization
Sun Jan 20, 2019 9:37 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Partial Pressure
Replies: 2
Views: 110

### Re: Partial Pressure

Usually the equation will tell you whether if it wants partial pressure or concentrations, but if within the chemical equation there is an aqueous solution then it will most likely be asking for concentrations
Sat Jan 12, 2019 11:06 pm
Forum: Ideal Gases
Topic: Pressure and volume
Replies: 4
Views: 191

### Re: Pressure and volume

If the pressure is increased by decreasing volume then that is correct but if pressure is increased by pumping gas in then that would be incorrect because moles and volume will have stayed constant and therefore the concentrations will have stayed constant and no change in the reaction will occur
Sat Jan 12, 2019 10:56 pm
Forum: Ideal Gases
Topic: Concentration or Partial Pressure
Replies: 13
Views: 365

### Re: Concentration or Partial Pressure

You can also tell by looking at if the equation is made up of all gases or if its made up of aqueous solutions, gases meaning use Kp and aqueous solutions meaning use Kc
Sat Jan 12, 2019 10:55 pm
Forum: Ideal Gases
Topic: bar or atm
Replies: 8
Views: 304

### Re: bar or atm

Bar and atm can be used interchangeably because they’re so close to equal in value
Sun Dec 09, 2018 10:21 am
Forum: Bronsted Acids & Bases
Topic: Lewis vs Bronsted
Replies: 10
Views: 844

### Re: Lewis vs Bronsted

Bronsted focuses more on the transfer of protons and lewis focuses more on the transfer of pairs of electrons
Sun Dec 09, 2018 10:18 am
Forum: Air Pollution & Acid Rain
Topic: Acid Rain Formation
Replies: 6
Views: 480

### Re: Acid Rain Formation

Acidic rain occurs when sulfur dioxide and nitrogen oxide mix with water molecules and create acid, acid rain can be prevented by lowering emissions and using more renewable energy sources
Sun Dec 09, 2018 10:16 am
Forum: Calculating the pH of Salt Solutions
Topic: pH of acids
Replies: 13
Views: 669

### Re: pH of acids

if the pH is lower then the acid is stronger, I feel like its just something you kinda have to know
Sun Dec 02, 2018 11:16 am
Forum: Hybridization
Topic: Pi bonds in triple bond
Replies: 17
Views: 867

### Re: Pi bonds in triple bond

every bond after that first sigma bond is going to be a pi bond so there is one sigma bond and then two pi bonds in a triple bond
Sun Dec 02, 2018 11:14 am
Forum: Hybridization
Topic: Hybridization Notation
Replies: 10
Views: 349

### Re: Hybridization Notation

On a test will both notations be counted as correct?
Sun Dec 02, 2018 11:13 am
Forum: Hybridization
Topic: 2SP^3 vs. SP^3
Replies: 6
Views: 261

### Re: 2SP^3 vs. SP^3

Does it matter if we put the 2 in front of it on tests? or are both ways counted correct?
Sun Nov 25, 2018 4:09 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: pi and sigma bonds
Replies: 9
Views: 439

### Re: pi and sigma bonds

every bond begins with a sigma bond, then when you have a double bond you have a sigma bond and pi bond, the bonds after that first sigma bond are going to be pi bonds
Sun Nov 25, 2018 4:05 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Linear structure with lone pairs
Replies: 6
Views: 275

### Re: Linear structure with lone pairs

All of these are 180 degrees right? regardless of the number of lone pairs of elections?
Sun Nov 25, 2018 4:01 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Shapes Not covered in Lecture
Replies: 10
Views: 471

### Re: Shapes Not covered in Lecture

its probably best to be prepared, just in case it does come up on the test, and since it is in the homework I'm sure its expected that we know it
Tue Nov 13, 2018 11:03 am
Forum: Bond Lengths & Energies
Topic: Bond Length
Replies: 9
Views: 507

### Re: Bond Length

within a lewis structure if there is single and double bonds, then the bond length of all the bonds is going to going to be the same and it will be a length somewhere in between that of the length of the single bond and the length of the double bond, this is because this creates a more stable struct...
Tue Nov 13, 2018 11:00 am
Forum: Bond Lengths & Energies
Topic: Drawing resonance structures?
Replies: 6
Views: 274

### Re: Drawing resonance structures?

If it is a structure where you can change where the double bonds go while keeping the charges the same except for the molecules that you shifted the bond between, then draw the resonance structures and the double arrows between them because the most stable structure is a mixture of the resonance str...
Tue Nov 13, 2018 10:56 am
Forum: Bond Lengths & Energies
Topic: finding bond length
Replies: 6
Views: 251

### Re: finding bond length

also if the structure has some single bonds and some double bonds the overall bond length will be somewhere between the given values for two types of bonds
Fri Nov 09, 2018 10:12 pm
Forum: Bond Lengths & Energies
Replies: 3
Views: 208

final grades are assigned at the end of the quarter once they figure out the class average, we kind of just have to wait to see what an A is
Fri Nov 09, 2018 10:10 pm
Forum: Bond Lengths & Energies
Topic: MIDTERM Bond Length Question
Replies: 15
Views: 576

### Re: MIDTERM Bond Length Question

does anyone happen to know why it averages out so they're all the same length as opposed to just letting the double bond be a different strength than the single bond?
Fri Nov 09, 2018 10:08 pm
Forum: Bond Lengths & Energies
Topic: boiling points
Replies: 4
Views: 190

### Re: boiling points

the stronger the bond the harder to break therefore resulting in a higher boiling point
Sun Nov 04, 2018 10:07 pm
Forum: Electronegativity
Topic: Calculating electronegativity
Replies: 10
Views: 673

### Re: Calculating electronegativity

Are we also supposed to have memorized the exceptions to the electronegativity trend? i.e C, N, O, F
Sun Nov 04, 2018 10:04 pm
Forum: Ionic & Covalent Bonds
Topic: Chem Midterm
Replies: 13
Views: 526

### Re: Chem Midterm

we just need a pen, a simple scientific (non-graphing) calculator, and a photo ID
Sat Nov 03, 2018 11:49 am
Forum: Trends in The Periodic Table
Topic: 7th Edition 1F 11
Replies: 1
Views: 73

### 7th Edition 1F 11

Which element of the following pairs has the higher electron affinity: a)tellurium or iodine, b)beryllium or magnesium, c)oxygen or sulfur, d)gallium or indium; i thought that as you moved across a period and up a group electron affinity increased, but the answer key says that suffer has higher elec...
Sun Oct 28, 2018 9:12 pm
Forum: Electronegativity
Topic: Periodic Trends
Replies: 8
Views: 347

### Re: Periodic Trends

how would one know that O>Cl?
Sun Oct 28, 2018 8:58 pm
Forum: Lewis Structures
Topic: octets
Replies: 13
Views: 497

### Re: octets

if the element has 8 valence electrons then its a full octet, the main exceptions to the rule are hydrogen, helium, lithium and barium
Sun Oct 28, 2018 8:41 pm
Forum: Trends in The Periodic Table
Topic: Electron Affinity Equation
Replies: 1
Views: 79

### Re: Electron Affinity Equation

im not quite positive but i think it has something to do with the fact that electron affinity is measuring the amount of energy released, therefore the change in energy is going to be negative
Sun Oct 21, 2018 8:25 pm
Forum: Photoelectric Effect
Topic: Test #2
Replies: 9
Views: 476

### Re: Test #2

I'm pretty sure Lavelle said that only what was covered up until Friday's lecture is going to be on the test
Sun Oct 21, 2018 8:23 pm
Forum: Photoelectric Effect
Topic: Test 2
Replies: 16
Views: 569

### Re: Test 2

The test will only cover what we've learned in the quantum world up until Friday's lecture
Tue Oct 16, 2018 3:05 pm
Forum: DeBroglie Equation
Topic: 1B.15
Replies: 4
Views: 127

### Re: 1B.15

with this question, I know I'm supposed to use de Broglie equation which is wavelength=h/p, where p equals mass times velocity, i was just wondering how to find the mass of the electron so that i can find p
Sun Oct 14, 2018 6:57 pm
Forum: Properties of Light
Topic: Test 2
Replies: 17
Views: 491

### Re: Test 2

I think test 2 is going to be chapter one and some of chapter two but I'm not quite positive
Sun Oct 14, 2018 3:45 pm
Forum: Properties of Light
Topic: Colors and Frequency
Replies: 14
Views: 839

### Re: Colors and Frequency

I think it would just be helpful to be able to know kind of generally where different wavelengths fall within the spectrum and then know the order in which they fall, like knowing which types of light are bigger and smaller than what other types based on their wavelength
Sun Oct 14, 2018 3:34 pm
Forum: Properties of Light
Topic: 1A.3 7th edition
Replies: 1
Views: 66

### 1A.3 7th edition

what exactly is meant by the extent of the change in the electrical field at a given point?
Thu Oct 04, 2018 3:29 pm
Forum: SI Units, Unit Conversions
Topic: Homework Questions [ENDORSED]
Replies: 14
Views: 573

### Re: Homework Questions[ENDORSED]

Does anyone know if/when the modules are due and if they're graded at all?
Thu Oct 04, 2018 3:02 pm
Forum: Significant Figures
Topic: Decimal point
Replies: 14
Views: 510

### Re: Decimal point

Can someone explain what the rule is for 120 to be only two significant figures while 120. is three
Thu Oct 04, 2018 2:50 pm
Forum: SI Units, Unit Conversions
Topic: How does grading for discussion posts work?
Replies: 80
Views: 3902

### Re: How does grading for discussion posts work?

Does anyone know when the cutoff for week one's discussion period is? Like how long we have to post for week one and when week two starts?