## Search found 53 matches

Fri Mar 13, 2020 4:44 pm
Forum: Administrative Questions and Class Announcements
Topic: UA Final Review - Kate, Riya, Matthew
Replies: 13
Views: 1216

### Re: UA Final Review - Kate, Riya, Matthew

hi, I was just wondering when the solutions were going to be posted? thank you! :)
Thu Mar 12, 2020 12:30 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Battery
Replies: 8
Views: 167

### Re: Battery

Yes because if it is dead it is not spontaneous so delta G = 0
Thu Mar 12, 2020 12:29 pm
Forum: General Rate Laws
Topic: Rate limiting step
Replies: 13
Views: 162

### Re: Rate limiting step

the slowest step of the reaction is the rate-determining step
Thu Mar 12, 2020 12:13 pm
Forum: General Rate Laws
Topic: Units of time
Replies: 5
Views: 49

### Re: Units of time

I think you can use hours, it just depends on what the question is asking for.
Thu Mar 12, 2020 12:10 pm
Forum: Administrative Questions and Class Announcements
Topic: Take Home Final
Replies: 16
Views: 313

### Re: Take Home Final

I'm also not sure if it's going to take place at the same time Sunday for 3 hours like an online quiz or something or a bigger window to turn in?
Tue Mar 10, 2020 10:04 pm
Forum: Administrative Questions and Class Announcements
Topic: review sessions and office hours
Replies: 6
Views: 154

### review sessions and office hours

Will review sessions and office hours now be canceled?
Fri Mar 06, 2020 12:28 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: galvanic cells
Replies: 8
Views: 146

### Re: galvanic cells

if two are given you can't use the formula Ecell = Ecathode - Eanode and then decide which is which based on which arrangement will give you a positive overall value.
Tue Mar 03, 2020 9:24 pm
Forum: Van't Hoff Equation
Topic: derivation?
Replies: 3
Views: 129

### derivation?

Do we actually have to know how to derive the equation for an exam or just understand what it means/what it does? Should we memorize the final equation?
Tue Mar 03, 2020 9:15 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 6N.3c
Replies: 4
Views: 89

### Re: 6N.3c

You can convert torr to atm by dividing the torr values by 760. The units will then cancel out as you solve the equation. after this do you implement the pressures into the Q equation? I keep getting the wrong overall answer so I'm not sure what I'm doing wrong. Yes, you would plug in the converted...
Tue Mar 03, 2020 8:53 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: cell diagram order of phases
Replies: 6
Views: 138

### cell diagram order of phases

is there a specific order that a cell diagram has to be in in terms of phases?

For example:
Cr(s)|Cr3+(aq)||Cl2(g)|Cl-(aq)|C(s)

can the Cl2(g) and Cl-(aq) be switched or does it have to be in this order?
Tue Mar 03, 2020 3:53 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 6N.3c
Replies: 4
Views: 89

### Re: 6N.3c

Ryan Chang 1C wrote:You can convert torr to atm by dividing the torr values by 760. The units will then cancel out as you solve the equation.

after this do you implement the pressures into the Q equation? I keep getting the wrong overall answer so I'm not sure what I'm doing wrong.
Sun Mar 01, 2020 9:22 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6M7
Replies: 3
Views: 62

### Re: 6M7

I'm also confused about this, there are many listed for elements such as copper and I'm not sure which to use.
Sat Feb 29, 2020 10:31 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Potential vs Standard Cell Potential
Replies: 1
Views: 10

### Re: Cell Potential vs Standard Cell Potential

I think the standard cell potential is the value given by the textbook or other lists while the cell potential is one you calculate.
Sat Feb 29, 2020 10:18 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: No Salt Bridge
Replies: 7
Views: 112

### Re: No Salt Bridge

kind of reiterating, but when there is no salt bridge the anode loses electrons because it is sending them to the cathode side, therefore the anode becomes more positive and the cathode becomes more negative. therefore, the positive ions from the salt bridge travel to the side with an excess negativ...
Sat Feb 29, 2020 10:05 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6L. 7 a)
Replies: 2
Views: 41

### Re: 6L. 7 a)

I think you base it off their standard electrode potentials. Use the equation Ecathode - Eanode to determine which way gives you a positive overall Ecell to determine which is the cathode and which is the anode.
Fri Feb 28, 2020 5:55 pm
Forum: Balancing Redox Reactions
Topic: Test 2
Replies: 10
Views: 117

### Re: Test 2

"Test 2 covers 2nd page of Outline 4: Thermodynamics and Outline 5: Electrochemistry and its Applications" this is from the announcements
Fri Feb 28, 2020 5:53 pm
Forum: Balancing Redox Reactions
Topic: Oxidation Numbers
Replies: 7
Views: 150

### Re: Oxidation Numbers

Sun Feb 23, 2020 5:39 pm
Forum: Balancing Redox Reactions
Topic: Oxidation States
Replies: 7
Views: 64

### Re: Oxidation States

I agree with what was said above: try to find the elements that generally have the same oxidation states first and assign them their charge so you can then figure out the states of the other elements to make the overall charge zero or satisfy the overall charge of the molecule.
Sun Feb 23, 2020 5:33 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagram with one reactant
Replies: 1
Views: 33

### Re: Cell Diagram with one reactant

I think it depends on when you break the equations down, is there a clear one that has something being reduced and a clear one that has something being oxidized. Then you can decide which is the anode and which is the cathode.
Sun Feb 23, 2020 5:30 pm
Forum: General Science Questions
Topic: Organic Chemistry Tutor?
Replies: 6
Views: 148

### Re: Organic Chemistry Tutor?

organic chemistry tutor is really good! I always watch his videos for a review, but I wouldn't try to learn everything directly from them as he may not hit everything we need to know.
Sat Feb 22, 2020 1:47 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Salt Bridge
Replies: 5
Views: 39

### Re: Salt Bridge

kind of reiterating, but the positive ions from the salt bridge travel to the side with an excess negative charge while the negative ions travel to the side with an excess positive charge to balance out the charges to neutral.
Sat Feb 22, 2020 1:44 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: E cell
Replies: 6
Views: 131

### Re: E cell

the E cell can be given in a problem, but usually we have to solve it using the standard reduction potentials from the appendix
Wed Feb 12, 2020 3:28 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Pizza Rolls #7
Replies: 3
Views: 97

### Re: Pizza Rolls #7

Question 7 asks you to find the change in internal energy when the reaction occurs with 1 mole of CO2 being produced. The equation for internal energy is q + w. In order to find q, remember that q equals delta at constant pressure. Using the enthalpy of reaction (-245 kJ per mole of rxn) convert th...
Wed Feb 12, 2020 12:15 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: change in Kc
Replies: 5
Views: 76

### Re: change in Kc

you raise Kc to whatever you multiply by. if you multiply by 2 then Kc = Kc^2, if you divide by 2 / multiply by 1/2 then Kc = Kc^1/2 or square root of Kc.
Wed Feb 12, 2020 12:08 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Difference between equations
Replies: 2
Views: 67

### Re: Difference between equations

I think generally either both pressure and temperature will be constant resulting only in a change in volume or pressure and volume would be constant resulting in only a change in temperature. If there is a change in volume use nRln(V2/V1), if there is a change in temperature use nCln(T2/T1).
Wed Feb 12, 2020 10:41 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 4.7
Replies: 2
Views: 47

### Re: 4.7

You need to first write out your balanced equation. The equation that you're going to want to use is w=-PdeltaV. You know that PdeltaV=deltanRT (ideal gas law). From there, you can find that the delta n of the gaseous products is (6-7.5=1.5), and then you just plug in the other values. where did yo...
Tue Feb 11, 2020 5:32 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 4J.13 stability
Replies: 1
Views: 18

### 4J.13 stability

I'm confused on question 4J.13: Determine which of the following compounds are stable with respect to decomposition into their elements under standard conditions at 25 °C (see Appendix 2A): (a) PCl 5 (g ) ; (b) HCN (g); (c) NO (g); (d) SO 2 (g) . I don't really understand what it means by stable in ...
Tue Feb 11, 2020 4:04 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: reversible expansion vs. irreversible free expansion
Replies: 2
Views: 60

### reversible expansion vs. irreversible free expansion

Could someone explain the difference between isothermal, reversible expansion and isothermal, irreversible free expansion? They are mentioned in question 4I.9 on the homework and I'm not really sure what they mean. "Initially an ideal gas at 323 K occupies 1.67 L at 4.95 atm. The gas is allowed...
Sun Feb 09, 2020 12:22 am
Forum: Administrative Questions and Class Announcements
Topic: midterm format
Replies: 8
Views: 98

### midterm format

I was wondering what the format for midterms are usually like? How many questions are there and is it all free-response or any multiple choice?
Sun Feb 09, 2020 12:09 am
Forum: Calculating Work of Expansion
Topic: Midterm equation sheet
Replies: 16
Views: 215

### Re: Midterm equation sheet

yes, I think it is also the same as the one given on the first test we had.
Sat Feb 08, 2020 7:30 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: degeneracy relation to thermo
Replies: 5
Views: 77

### degeneracy relation to thermo

I'm kind of still confused about how degeneracy relates to thermodynamics/thermochemistry. Right now, I think understand it vaguely more in terms of quantum mechanics...? Could someone explain the relation between thermo and degeneracy / energy levels / positions / etc.?
Sat Feb 08, 2020 7:23 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Irreversible Expansion
Replies: 1
Views: 23

### Re: Irreversible Expansion

with free expansion, there is no pressure being put on the system and therefore no work can be done because it is not going against any force.
Sat Feb 08, 2020 7:19 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond Enthalpies
Replies: 3
Views: 32

### Re: Bond Enthalpies

you don't have to draw out the lewis structures but it is very helpful because then you can visualize which bonds are broken and which bonds are formed.
Sun Feb 02, 2020 5:50 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy units
Replies: 5
Views: 70

### Re: Enthalpy units

I think kJ or J is okay as long as it is consistent
Sun Feb 02, 2020 5:49 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Closed vs isolated systems
Replies: 24
Views: 206

### Re: Closed vs isolated systems

closed systems can exchange heat/energy with its surroundings but not actual substance. Isolated systems can exchange neither.
Sun Feb 02, 2020 5:46 pm
Forum: Administrative Questions and Class Announcements
Topic: week 5 homework
Replies: 4
Views: 59

### week 5 homework

should our homework for this week be from the thermochemistry and first law of thermodynamics section or thermodynamics: second and third laws section?
Sat Feb 01, 2020 2:58 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Calorimeter + Heat Transfer
Replies: 4
Views: 28

### Re: Calorimeter + Heat Transfer

If a reaction occurs in a calorimeter and loses heat then that heat cannot go anywhere but stay in the system. Therefore, the calorimeter gains the heat lost by the reaction if that makes sense.
Sat Feb 01, 2020 2:55 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: units for reaction enthalpy and enthalpy of formation
Replies: 3
Views: 47

### Re: units for reaction enthalpy and enthalpy of formation

I think you can use both. If it just says kJ it usually means per mole unless otherwise stated.
Fri Jan 24, 2020 12:17 pm
Forum: Administrative Questions and Class Announcements
Topic: homework for week 4
Replies: 11
Views: 129

### homework for week 4

What section should our homework be from for next week? Thermochemistry and First Law of Thermodynamics?
Fri Jan 24, 2020 12:12 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: solvent
Replies: 10
Views: 60

### Re: solvent

if the states of the molecules are gas (g) or aqueous (aq) they are involved in the reaction but if the states are liquid (l) or solid (s) they are not included.
Tue Jan 21, 2020 2:38 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 6E.3b
Replies: 1
Views: 22

### 6E.3b

I was kinda confused on how to solve this problem: find the pH of 0.10M (COOH)2(aq) at 25 °C. I solved it one way and got 1.25 as the pH but the answer key says 1.28 so I didn't know if I was close enough or if I did it wrong. I wasn't really sure about how the equation would look for (COOH)2 and H2O.
Mon Jan 20, 2020 4:48 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: "Quick Way" for predicting response to changes in volume/pressure
Replies: 3
Views: 37

### Re: "Quick Way" for predicting response to changes in volume/pressure

if you decrease the volume, that means you are adding more pressure to the system. Therefore, if there are more moles on the left of an equation, decreasing the volume will cause the reaction to go to the right because there are less moles of gas on that side/more space so the reaction will want to ...
Mon Jan 20, 2020 4:41 pm
Forum: Student Social/Study Group
Topic: test 1
Replies: 7
Views: 94

### test 1

I was wondering if anyone knew the format of tests for this class maybe if you had Lavelle last quarter? Like length-wise and if there's multiple choice or just free response? Also, what is the best way to study?
Thu Jan 16, 2020 10:13 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Acid and Base Equilibria
Replies: 1
Views: 15

### Re: Acid and Base Equilibria

the pH scale is 1-14 so the closer to 1, the stronger the acid. therefore, weaker acids will have a higher pH value meaning they are less acidic than strong acids.
Thu Jan 16, 2020 9:34 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Exothermic
Replies: 5
Views: 84

### Re: Exothermic

usually when bonds are formed it is more favorable than the atoms being by themselves so therefore they release any extra energy and become more stable.
Thu Jan 16, 2020 9:19 pm
Forum: Administrative Questions and Class Announcements
Topic: test 1/homework
Replies: 4
Views: 86

### test 1/homework

next week do we still have homework due in discussion even though there is a test?
Sun Jan 12, 2020 4:59 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5I.25
Replies: 2
Views: 38

### Re: 5I.25

yes, I got that then I did:
85.0 = (0.02+x)(0.03+x)/(0.02-x)(0.04-x)
but then I think I'm just not solving it correctly or something. probably more of a math issue than chemistry haha
Sun Jan 12, 2020 3:08 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5I.25
Replies: 2
Views: 38

### 5I.25

I'm kinda confused about this problem. It gives the initial concentrations for all components and the K and is asking for the equilibrium concentrations so I know you have to find x and then subtract/add it to the original concentrations but I can't seem to find x. I did an ICE table and set the con...
Thu Jan 09, 2020 7:51 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Temperatures and Equilibrium
Replies: 4
Views: 46

### Re: Temperatures and Equilibrium

I believe reactions can reach equilibrium at multiple temperatures but the K changes.
Thu Jan 09, 2020 7:34 pm
Forum: Administrative Questions and Class Announcements
Topic: homework question
Replies: 5
Views: 79

### homework question

For the homework due tomorrow can it literally just be any 5 problems? Or should it be like one from each section?
Thu Jan 09, 2020 7:29 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5H.3
Replies: 2
Views: 44

### Re: 5H.3

oh, thank you. I was adding the Ks before.
Thu Jan 09, 2020 7:17 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5H.3
Replies: 2
Views: 44

### 5H.3

I'm not sure if I'm looking at the wrong thing or something but the K I found for the equation in this question from the chart it gives does not match the answer I found in the back of the book. How do you find the K?
Thu Jan 09, 2020 7:09 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5G.7
Replies: 5
Views: 51

### Re: 5G.7

this is unrelated but can someone help me please? I can't figure out how to post something without replying to someone...