## Search found 37 matches

Sun Mar 18, 2018 8:59 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Relation between cell potential and concentration
Replies: 1
Views: 234

### Relation between cell potential and concentration

What is the relationship of concentration to cell potential? For example what would happen is we decreased the concentration of one of the reactants.
Tue Mar 13, 2018 7:47 pm
Forum: General Rate Laws
Topic: 15.19 solving for K
Replies: 2
Views: 149

### Re: 15.19 solving for K

The answer given is in L^4*mmol^-4*s^-1
Tue Mar 13, 2018 7:41 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Test 2 Calculating standard potential #7
Replies: 2
Views: 319

### Test 2 Calculating standard potential #7

Calculate the standard potential for the following reactions using the standard reduction potential on the last page of the test: Cr2O7 + 14H+ +12e- ---> 2Cr(s)+7H2O(l) Eo= 1.33V How would we approach this problem? At first I thought that we had to find the standard Gibbs energy, but this was marked...
Tue Mar 13, 2018 7:38 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Identifying highest reducing/oxidizing power
Replies: 3
Views: 233

### Identifying highest reducing/oxidizing power

How can we tell which elements have a higher reducing/oxidizing power? Do we use a periodic table, or do we have to have equations given in order to find out?
Tue Mar 13, 2018 6:45 pm
Forum: General Rate Laws
Topic: 15.19 solving for K
Replies: 2
Views: 149

### 15.19 solving for K

I am having trouble finding k for the rate:
rate=[A][B]^2[C]^2

I used one of the equations and plugged them in, and got 2.85, but i am confused as to why the answer is 2.85 x10^12. where did the 10^12 come from?
Fri Mar 09, 2018 11:19 am
Forum: First Order Reactions
Topic: Help on 15.3
Replies: 7
Views: 582

### Help on 15.3

In the answers it said that the answer is 2.2x10^-5 mol/(L*s), but I do not understand why they didn't convert the mL to L before solving the problem. Also how do we get those units?
Wed Feb 28, 2018 2:50 pm
Forum: Student Social/Study Group
Topic: Lost ring During Discussion 1F
Replies: 1
Views: 342

### Lost ring During Discussion 1F

Hi,
I was wondering If anyone in discussion 1F found a ring after discussion. It is a rosegold band twisted with a silver(diamond) band. It is very special to me and would appreciate it if someone had found it and returned it to me.
Thanks
Tue Feb 20, 2018 10:00 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14.15 Part C
Replies: 1
Views: 135

### 14.15 Part C

Why is the Galvanic cell for the reaction:

Cd(s) + 2 Ni(OH)3(s) ----> Cd(OH)2(s) + 2 Ni(OH)2(s)

Cd(s)|Cd(OH)2(S)|KOH(aq)||Ni(OH)3|NI(OH2(S)|Ni(s)
Why is there a KOH? where did the K come from?
Also why are we using nickel for the solid on the cathode side?
Tue Feb 20, 2018 9:54 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Help on 14.15 half-reactions
Replies: 1
Views: 184

### Help on 14.15 half-reactions

4.15 Write the half-reactions and devise a galvanic cell (write a cell diagram) to study each of the following reactions: (a) AgBr(s) ---> Ag (aq) + Br (aq), a solubility equilibrium (b) H (aq) + OH (aq) ---> H2O(l), the Brønsted neutralization reaction (c) Cd(s) +2 Ni(OH)3(s) ---> Cd(OH)2(s) + 2 Ni...
Tue Feb 20, 2018 8:21 pm
Forum: Balancing Redox Reactions
Topic: 14.5 Part B
Replies: 1
Views: 135

### 14.5 Part B

b) Br2(l) --->BrO3-(aq)+Br-
Im confused on how the answer ended up with 3Br2

I got
3H2O+Br2 +6OH- ---> BrO3- +6H2O + 5e-
as the oxidation reaction

Im confused on how to approach the reduction one
Tue Feb 13, 2018 10:35 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Calculating how much energy is supplied [ENDORSED]
Replies: 1
Views: 178

### Calculating how much energy is supplied[ENDORSED]

A bowl containing 56 grams of ice cream is sitting out in the sun. The heat from the sun completely melts the ice cream and raises its temperature to 30oC . Assuming that the ice cream was initially a solid with a freezing point at 0oC , how much energy was supplied to the ice cream? ( ΔH f usion of...
Tue Feb 13, 2018 9:38 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Specific Heat capacity
Replies: 1
Views: 443

### Specific Heat capacity

A 245.7g sample of a metal at 75.2 degrees Celsius was placed in 115.43g of water at 22.6oC . The final temperature of the water was 34.6oC . Assuming no heat was lost to the surroundings, calculate the specific heat of the metal. Are we supposed to use q=nCd*delta T, and if so then how to we get to...
Tue Feb 13, 2018 9:20 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Help on 9.19
Replies: 1
Views: 165

### Help on 9.19

Calculate the standard entropy of vaporization of water at 85 C, given that its standard entropy of vaporization at 100. C is 109.0 J K 1 mol 1 and the molar heat capacities at constant pressure of liquid water and water vapor are 75.3 J K 1 mol 1 and 33.6 J K 1 mol 1, respectively, in this range. I...
Thu Feb 08, 2018 9:20 am
Forum: Phase Changes & Related Calculations
Topic: Phase changes with entropy?
Replies: 6
Views: 372

### Phase changes with entropy?

Do we still have to account for phase changes when trying to find the entropy of the system? If so how would we approach doing so.
Tue Feb 06, 2018 9:05 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: How to approach 9.53
Replies: 1
Views: 292

### How to approach 9.53

Calculate the change in molar Gibbs free energy for the process NH3(l) S NH3(g) at 1 atm and (a) 15.0 C; (b) 45. C (see Tables 8.3 and 9.1). In each case, indicate whether vaporization would be spontaneous. Are we supposed to use the delta G = delta H - T * delta S if so which delta H and which delt...
Tue Feb 06, 2018 8:20 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: How to approach 9.19
Replies: 2
Views: 207

### How to approach 9.19

Calculate the standard entropy of vaporization of water at 85 C, given that its standard entropy of vaporization at 100. C is 109.0 J K 1 mol 1 and the molar heat capacities at constant pressure of liquid water and water vapor are 75.3 J K 1 mol 1 and 33.6 J K 1 mol 1, respectively, in this range. I...
Fri Feb 02, 2018 1:50 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: How to tell what happens to entropy by seeing a reaction?
Replies: 6
Views: 477

### How to tell what happens to entropy by seeing a reaction?

C12H22O11(s) + O2(g) ---> CO2(g) +H2O(l)

Given this equation how would we be able to tell what happens to entropy?
Fri Feb 02, 2018 1:41 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Question 3b on the test
Replies: 4
Views: 343

### Question 3b on the test

The question stated :
A balloon filled with gas is expanded to a larger volume and lower pressure while maintaining the same temperature.

I was confused on how to Approach this question, is heat being transferred?
Fri Feb 02, 2018 1:29 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: How do we find out if a system is favorable? [ENDORSED]
Replies: 7
Views: 2219

### How do we find out if a system is favorable?[ENDORSED]

Dr. Lavelle mentioned during Wednesday's class that we can use entropy in order to find out if a system is favorable. He said there where two ways in order to find find this out, but I was not able to catch it.
Tue Jan 23, 2018 7:17 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Solve for reaction enthalpy using bond enthalpies
Replies: 1
Views: 114

### Solve for reaction enthalpy using bond enthalpies

Im confused on which bond enthalpies to use when we are using bond enthalpies. I know we have to add them together, but how do we find them in the appendix, for example for the problem 8.59
Tue Jan 23, 2018 6:55 pm
Forum: Phase Changes & Related Calculations
Topic: How to differentiate when to use certain formulas
Replies: 3
Views: 289

### How to differentiate when to use certain formulas

When approaching a problem are there any keywords that will help identify what equation(s) to use? And just to make sure, which equations should we know how to use
Tue Jan 23, 2018 6:29 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Problem 8.51
Replies: 2
Views: 318

### Problem 8.51

The enthalpy of formation of trinitrotoluene (TNT) is 67 kJ·mol 1, and the density of TNT is 1.65 g·cm 3. In principle, it could be used as a rocket fuel, with the gases resulting from its decomposition streaming out of the rocket to give the required thrust. In practice, of course, it would be extr...
Tue Jan 16, 2018 11:04 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Help understanding what is being asked in 8.19
Replies: 2
Views: 239

### Help understanding what is being asked in 8.19

(a) Calculate the heat that must be supplied to a 500.0-g stainless steel vessel containing 400.0 g of water to raise its temperature from 22.0 C to the boiling point of water, 100.0 C.(b) What percentage of the heat is used to raise the temperature of the water? (c) Compare these answers with those...
Tue Jan 16, 2018 10:11 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Is there a way specific way to approach into seeing if open closed or isolated?
Replies: 9
Views: 534

### Is there a way specific way to approach into seeing if open closed or isolated?

Is there a specific way to figure out if a real life example is open closed or isolated? Some of the examples get harder, but i understand what each one of them is .
Tue Jan 09, 2018 2:38 pm
Forum: Administrative Questions and Class Announcements
Topic: bruincast?
Replies: 1
Views: 390

### bruincast?

Hi all, So I was wondering if there would be any chance that Dr. Lavelle would bruincast this quarter, because he bruincasted his lectures in the past. I do not intend to miss the lectures on purpose, but because of a conflict with work I have to miss Monday lectures, and do not want to fall behind.
Sun Dec 10, 2017 7:22 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: How to tell if an acid or a base (ligand)
Replies: 1
Views: 161

### How to tell if an acid or a base (ligand)

How would we go about on finding out if a ligand is acting as a acid or a base?
Sun Dec 10, 2017 12:52 am
Forum: Quantum Numbers and The H-Atom
Topic: How many electrons with given quantum numbers including ml
Replies: 3
Views: 367

### How many electrons with given quantum numbers including ml

If a question asks how many electrons can there be with the given quantum numbers and they included a ml number is it always going to be on 2? Im assuming this because of the spin number but im not sure if this is correct.
Sat Dec 09, 2017 11:05 pm
Forum: Significant Figures
Topic: Rounding: when and where?
Replies: 10
Views: 553

### Rounding: when and where?

So I am aware of the sig fig rules, but i am having trouble trying to figure out when to round and when to just do the cut off method. For example when i got an answer for a square root i got .000189737, and the answer was 1.89x10^-4. I was wondering if we put 1.90x10^-4 would be marked as wrong.
Thu Dec 07, 2017 2:14 pm
Forum: Naming
Topic: Oxidation Numbers and how to get them
Replies: 4
Views: 424

### Oxidation Numbers and how to get them

I am having trouble in understanding how to find the oxidation numbers of elements in chemical solutions involving ligands. What is the process to go about in finding oxidation numbers of the metals with ligands?
Thu Dec 07, 2017 11:48 am
Forum: Lewis Acids & Bases
Topic: What tables should we know from the book?
Replies: 4
Views: 379

### What tables should we know from the book?

I know we have to know certain values and memorize various acids and bases, and ligands, so I was wondering what tables should i memorize for the final?
Tue Dec 05, 2017 7:47 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: How to tell if bidentate, tri- etc
Replies: 5
Views: 948

### How to tell if bidentate, tri- etc

I am having trouble trying to understand how to tell if a ligand is biadentate, traiadentate etc. On the test in particular i did not understand how to figure it out because it was not in a typical ligand compound. Is there anyway to easily find out what they are?
Tue Dec 05, 2017 7:41 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Delocalization and how to identify it
Replies: 1
Views: 129

### Delocalization and how to identify it

Is there an easy way to find out whether there is delocalization in a compound apart from looking at the lewis diagram? Apart from this what is a good way to explain what delocalization is and how it happens.
Tue Dec 05, 2017 7:37 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Where to put the initial conditions [ENDORSED]
Replies: 1
Views: 133

### Where to put the initial conditions[ENDORSED]

The problem is: Find the initial concentration of HClO with a pH of 4.60(Ka=1.0x10^-8) When solving the problem I converted the pH to M and then put it in the ICE table under the [I] of HClO, but when we solved it, they put it under the [C]. I was confused as to why it went there instead of the I, i...
Wed Nov 08, 2017 10:57 am
Forum: Electronegativity
Topic: Polar or non polar [ENDORSED]
Replies: 4
Views: 444

### Polar or non polar[ENDORSED]

What difference in electronegativity is that for a polar bond, and which for a non polar?
Also are there any electronegativities we should memorize before the midterm?
Wed Nov 01, 2017 2:40 pm
Forum: Octet Exceptions
Topic: Octet Exceptions and How to distinguish them [ENDORSED]
Replies: 1
Views: 213

### Octet Exceptions and How to distinguish them[ENDORSED]

I was working on problems and noticed that there were where exceptions to the octet rule such as XeF6. In this one Xe shares atoms with all 6 F, which breaks the octet rule. My question is how do we know when it is okay to break the octet rule, and or are there only certain exceptions?
Wed Oct 25, 2017 2:17 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Relation of radius/diameter size to precision
Replies: 3
Views: 304

### Relation of radius/diameter size to precision

A question asks : An electron is confined to the size of a magnesium atom(radius=150pm). What is min. uncertainty in its velocity? Another electron is confined to the size of a sodium atom (radius>150pm). In which atom can the velocity of the electron be known with the highest precision and why? For...
Tue Oct 17, 2017 8:26 pm
Forum: Photoelectric Effect
Topic: Help on Photoelectric effect practice question
Replies: 1
Views: 369

### Help on Photoelectric effect practice question

Question: The photoelectric effect is the observation that many metals emit electrons when light shines upon them. Given the threshold energy of copper (7.53*10^-19J), calculate the velocity (in m/s) of an electron that is emitted when electromagnetic radiation with a wavelength of 161 nm is shone o...