Search found 43 matches

Sun Mar 19, 2017 11:57 am
Forum: *Alkenes
Topic: Intro to organic chem Ch 1 #12b: cis and trans
Replies: 1
Views: 659

Intro to organic chem Ch 1 #12b: cis and trans

For the answer attached, why isn't there a trans- before the naming? There's a double bond with opposite priority groups on both sides so why didn't the book include trans?
Sat Mar 18, 2017 12:28 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Ch 14 #107
Replies: 1
Views: 418

Ch 14 #107

What range (in volts) does a voltmeter need to have to measure PH in the range of 1 to 14 at 25 degrees Celsius if the voltage is zero when PH=7?

How can we relate PH to the equations we've used for electrochem and solve this problem?
Mon Mar 13, 2017 8:18 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 2013 Final Exam #2
Replies: 3
Views: 582

2013 Final Exam #2

For this problem I'm confused on why we divide by 30.5kj for part a and divide by 30.5kj for part b as well. I was hoping someone could explain this problem in simple terms too.
Sun Mar 12, 2017 8:50 pm
Forum: First Order Reactions
Topic: Deriving the integrated rate laws [ENDORSED]
Replies: 1
Views: 427

Deriving the integrated rate laws[ENDORSED]

How can we derive the integrated rate laws for zero, first, and second order reactions? In the 2014 final exam question 4 asked to derive a second order reaction with A as a reactant so how could we derive this?
Fri Mar 10, 2017 11:25 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 2013 Final Exam practice
Replies: 2
Views: 351

2013 Final Exam practice

For part c of this problem how do we get n=6? I looked at the reaction and it didn't look like there were 6 moles in the system.
Sun Mar 05, 2017 3:33 pm
Forum: *Cycloalkanes
Topic: Quiz 3 prep #4
Replies: 3
Views: 413

Re: Quiz 3 prep #4

How do we tell which substituent has the highest priority? What would it be in this example and how would you tell?
Sun Mar 05, 2017 2:42 pm
Forum: *Cycloalkanes
Topic: Quiz 3 prep #4
Replies: 3
Views: 413

Quiz 3 prep #4

In the question below where do we start to number the carbon atoms? I'm not sure how to label the substituents in the cycloalkane since I don't know where we would start counting the carbon atoms.
Sat Mar 04, 2017 9:51 pm
Forum: *Haloalkanes
Topic: Introduction to Organic Chem ch. 4 #31
Replies: 2
Views: 880

Introduction to Organic Chem ch. 4 #31

For the electrophilic addition reaction of hydrogen bromide, HBr, to propene, CH3CHCH2, producing 2-bromopropane, CH3CHBrCH3, write the rate laws for each elementary step and the overall rate law. Explain your answer for the overall rate law. How can we determine which step is the slow step to creat...
Sun Feb 26, 2017 7:47 pm
Forum: *Alkanes
Topic: Nucleophile vs Electrophile
Replies: 2
Views: 328

Nucleophile vs Electrophile

How do we tell if a compound is a nucleophile or electrophile? There's a list of common ones on pg 81 of the course reader so should we only memorize those ones or is there a way to tell which type it is?
Thu Feb 23, 2017 6:29 pm
Forum: General Rate Laws
Topic: Course reader pg 73 example
Replies: 2
Views: 346

For the pre-equilibrium approach example why is there a 2 in front of the reaction constant? Is it because 2 products (2NO2 ) are formed? Also, is the intermediate only present in the rate law if the first reaction is fast and the second reaction is slow?
Sun Feb 19, 2017 9:12 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Pre-equilibrium approach and steady-state approach
Replies: 3
Views: 2112

Re: Pre-equilibrium approach and steady-state approach

Are there any problems in the hw (or course reader) that show the three methods being used in one problem? I haven't been able to find any so far.
Sun Feb 19, 2017 7:57 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Pre-equilibrium approach and steady-state approach
Replies: 3
Views: 2112

What's the difference between the pre-equilibrium approach and steady-state approach? The course reader states that they give the same result but I'm confused with which method goes to which approach. Also, how would the direct computation method relate to these two approaches?
Sat Feb 18, 2017 10:12 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Quiz prep 2 #11
Replies: 4
Views: 646

Quiz prep 2 #11

The rate constant for the reaction A ---> B is 25 /min at 298k and 35 /min at 350k. Calculate the value of the rate constant at 770k. Give your answer in /min. I used a form of the Arrhenius equation to solve this and only got activation energy. What units are activation energy in and how can I find...
Sun Feb 12, 2017 1:28 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: E and E°, G and G°
Replies: 3
Views: 894

E and E°, G and G°

What's the difference between E and Ecell° as well as G and deltaG°? I know that they're used in the same formulas but I'm wondering under what conditions they'd change. I'm also wondering the names for each of the symbols since I know that there is Gibbs free energy and cell potential but I don't k...
Sat Feb 11, 2017 12:49 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: 14.9 [ENDORSED]
Replies: 1
Views: 304

14.9[ENDORSED]

Calculate the standard Gibbs free energy for the following cell reactions:
a) 2Ce+4 + 3I- ----> 2Ce+3 + I3-, Ecell=+1.08V

I know we used deltaG= -nFE but how do we find n? I thought we need to be given the number of electrons in the reaction.
Sat Feb 04, 2017 2:31 pm
Forum: Balancing Redox Reactions
Topic: Chapter 14.5 part d
Replies: 2
Views: 359

Chapter 14.5 part d

Balance the skeletal equation by using oxidation and reduction half-reactions. All the reactions take place in basic solution. Identify the oxidizing agent and reducing agent in each reaction. d)Reaction of elemental phosphorus to form phosphine, PH3, a poisonous gas with the odor of decaying fish: ...
Sun Jan 29, 2017 10:01 pm
Forum: Calculating Work of Expansion
Topic: Practice Quiz #3
Replies: 3
Views: 411

Re: Practice Quiz #3

You need to solve this problem numerically but I was also wondering the concept behind when u, q, or w would be 0.
Sun Jan 29, 2017 7:23 pm
Forum: Calculating Work of Expansion
Topic: Practice Quiz #3
Replies: 3
Views: 411

Practice Quiz #3

If 2.00 mol of an ideal gas at 300. K and 3.00 atm expands isothermally and reversible from 6.00L to 18.00L and has a final pressure of 1.20 atm, what is w, q, and delta U? The answer key said that delta U is 0 but would it still be 0 if we weren't working with an ideal gas? Also what initial condit...
Mon Jan 23, 2017 2:15 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Chapter 8 #101
Replies: 2
Views: 644

Chapter 8 #101

A technician carries out the reaction 2SO2(g) + O2(g) --> 2SO3(g) at 25°C and 1.00 atm in a constant-pressure cylinder fitted with a piston. Initially, 0.0300 mol SO2 and 0.0300 mol O2 are present in the cylinder. The technician then adds a catalyst to initiate the reaction. a)Calculate the volume o...
Sat Jan 21, 2017 7:05 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Chapter 8 #99
Replies: 1
Views: 266

Chapter 8 #99

Hydrochloric acid oxidizes zinc metal in a reaction that produces hydrogen gas and chloride ions. A piece of zinc metal of mass 8.5g is dropped in an apparatus containing 800.0mL of 0.500M HCL(aq). If the initial temperature of the hydrochloric acid solution is 25°C, what is the final temperature of...
Sun Jan 15, 2017 2:34 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Chapter 8 #65
Replies: 5
Views: 1080

Re: Chapter 8 #65

I'm confused about the second part of the solution. I understand that we needed to find the enthalpy of formation of N2O5 but why is -169.2kJ not the final answer?
Sun Jan 15, 2017 1:15 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Chapter 8 #65
Replies: 5
Views: 1080

Chapter 8 #65

Calculate the standard enthalpy of formation of dinitrogen pentoxide from the following data, and from the standard enthalpy of formation of nitric oxide, NO (see Appendix 2A) 2NO(g) + O2(g) ---> 2NO2(g) Delta h= -114.1kJ 4NO2(g) + O2(g) ---> 2N2O5(g) Delta h = -110.2kJ I'm having trouble getting th...
Sat Jan 14, 2017 4:10 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Chapter 8 #59 [ENDORSED]
Replies: 3
Views: 501

Chapter 8 #59[ENDORSED]

Use the data provided in Appendix 2A to calculate the standard reaction enthalpy for the reaction of calcite with hydrochloric acid: 4HNO3(l) + 5N2H4(l) ----> 7N2(g) + 12H2O(l) The solution manual subtracted the standard enthalpy of products from reactants, however, it didn't include the standard en...
Sat Dec 03, 2016 2:03 pm
Forum: *Titrations & Titration Calculations
Topic: Ch. 13 #97 [ENDORSED]
Replies: 1
Views: 849

Ch. 13 #97[ENDORSED]

How would I calculate the final PH for both friend's?
Thu Dec 01, 2016 6:20 pm
Forum: *Making Buffers & Calculating Buffer pH (Henderson-Hasselbalch Equation)
Topic: Ch.13 #105
Replies: 1
Views: 290

Ch.13 #105

I'm having trouble with part b) since I can't find the new H3O+ concentration. How would I calculate it?
Tue Nov 29, 2016 2:20 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Fall 2015 Final Exam #5
Replies: 1
Views: 271

Fall 2015 Final Exam #5

Write the molecular-orbital valence electron-configuration of the CN radical and determine its bond order. Does the bond order match the type of bond in the Lewis structure? What does your calculated bond order suggest about the stability of the cyanide radical? The answer states that the bond order...
Sun Nov 27, 2016 5:23 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Fall 2015 #5A
Replies: 2
Views: 496

Re: Fall 2015 #5A

This is the image given by the problem
Sun Nov 27, 2016 5:18 pm
Forum: *Titrations & Titration Calculations
Topic: Chapter 13 #35
Replies: 3
Views: 706

Chapter 13 #35

Suppose that 25.0ml of .10M CH3COOH is titrated with .10M NAOH. a)What is the initial PH of the .10M CH3COOH solution? b) What is the PH after the addition of 10.0ml of .10M NAOH?c)What volume of .10M NaOH is required to reach halfway to the stoichiometric point? d) Calculate the PH at that halfway ...
Sun Nov 20, 2016 11:54 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Fall 2015 #5A
Replies: 2
Views: 496

Fall 2015 #5A

There are only two ligands: the cyanide ligand, and the entire ring with its tail which we call "corrin-DMB." State each ligand's total charge.
*See diagram on page 260 for reference
Sun Nov 20, 2016 4:28 pm
Forum: Lewis Acids & Bases
Topic: Fall 2013 Final #7B
Replies: 1
Views: 374

Fall 2013 Final #7B

List the following acids in order of increasing strength and explain why: F3O2H, H3O2H, Cl3O2H, H3C(CH3)2O2H

I'm also wondering how to determine what makes an acid strong. Is it based only on its ability to lose an H atom? How would you determine what makes a base strong too?
Fri Nov 11, 2016 6:42 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Fall 2016 #6C [ENDORSED]
Replies: 2
Views: 533

Fall 2016 #6C[ENDORSED]

Consider the following reaction at 800k, for which you know kc=2.1x10^-3: I2(g)<-->I(g)
If you measure [I2] to be 3.18x10^-4M, calculate the equilibrium concentration of I for this experiment.

The answer is 8.2x10^-4M but I got a number much larger than that
Sun Nov 06, 2016 2:24 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Fall 2014 Quiz 2 prep #9
Replies: 1
Views: 397

Fall 2014 Quiz 2 prep #9

This problem asks which statement is false and the answer was: Atoms or molecules with an even number of electrons are diamagnetic. I was wondering what this was false since I thought that atoms/molecules with an odd amount of electrons were paramagnetic while the ones with event electrons were diam...
Sat Oct 29, 2016 6:03 pm
Forum: DeBroglie Equation
Topic: Fall 2013 Midterm #4
Replies: 3
Views: 669

Fall 2013 Midterm #4

During spontaneous fission uranium-235 emits a neutron with a mass of approximately 1.00866g/mol. If one of these neutrons has an energy of 4.84 Mev, what is its de Broglie wavelength? In your solution use E=p^2/2m and explicitly show that kinetic energy is related to momentum. I'm confused with wha...
Sat Oct 22, 2016 2:27 pm
Forum: Electronegativity
Topic: Ionic/Polar Character
Replies: 1
Views: 686

Ionic/Polar Character

For compounds is ionic character greater when the two elements are further apart or when they have greater ionic energy. For example, would K and Cl have greater ionic character than Mg and F? And would the same principle apply to polar character?
Sun Oct 16, 2016 8:32 pm
Forum: Lewis Structures
Topic: Chapter 3 #57 [ENDORSED]
Replies: 2
Views: 357

Chapter 3 #57[ENDORSED]

The problem states: Write the Lewis structure, including typical contributions to the resonance structure (where appropriate, allow for the possibility of octet exmpansion, including double bonds in different positions), for a) sulfite ion, b) hydrogen sulfite ion; perchlorate ion, d)nitrite ion. I'...
Fri Oct 14, 2016 7:46 pm
Forum: Ionic & Covalent Bonds
Topic: Excited state help
Replies: 1
Views: 302

Excited state help

I was looking through chapter 2 and I'm wondering how can you tell if an element has gone through an excited state? I know that if an electron skips an orbital it can occur but I'm wondering how else it occurs and why does it happen.
Sun Oct 09, 2016 1:28 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Fall 2014 Quiz Prep
Replies: 11
Views: 1138

Re: Fall 2014 Quiz Prep

Thanks for the help! I made Delta E negative since the problem states that energy is emitted and was able to get the right answer.
Thu Oct 06, 2016 12:10 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Fall 2014 Quiz Prep
Replies: 11
Views: 1138

Re: Fall 2014 Quiz Prep

I put n=4 into n-initial and solved for n-final which allowed me to get n=6. I'm wondering why this worked because the problem asked for the quantum level where the electron began.
Thu Oct 06, 2016 7:47 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Fall 2014 Quiz Prep
Replies: 11
Views: 1138

Fall 2014 Quiz Prep

An excited hydrogen atom emits light with a frequency of 1.14x10^14 Hz to reach energy level for which n=4. In what principle quantum level did the electron begin?

I got n=3 but the answer is n=6. I used the different variations of the Rydberg equation and haven't been able get the right answer.
Sun Oct 02, 2016 7:34 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Ch.1 #13
Replies: 1
Views: 279

Ch.1 #13

In the question section of chapter 1 #13 asks: Use the Rydberg formula for atomic hydrogen to calculate the wavelength for the transition from n = 4 to n = 2. b) What is the name given to the spectroscopic series to which this transition belongs? c) Use Table 1.1 to determine the region of the spect...
Wed Sep 28, 2016 1:11 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Uncertainty Problem Help [ENDORSED]
Replies: 4
Views: 774

Re: Uncertainty Problem Help[ENDORSED]

Thanks for the help! I got the wrong answer before since I forget to include 4pi when finding delta x.
Tue Sep 27, 2016 5:36 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Uncertainty Problem Help [ENDORSED]
Replies: 4
Views: 774

Re: Uncertainty Problem Help[ENDORSED]

Find the uncertainty in the position of a marble of mass 1.5g given that its speed is known to within +/- 0.55 m/s. Answer: Delta x= 3.2E-32m
Mon Sep 26, 2016 9:49 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Uncertainty Problem Help [ENDORSED]
Replies: 4
Views: 774

Uncertainty Problem Help[ENDORSED]

In the fall workbook Fall 2015 quiz prep question 3 asks: Find the uncertainty in the position of a marble of mass 1.5g given that its speed is known to within + or - 0.55m/s. I used the uncertainty equation delta x= h/m*delta v and made sure to convert mass to kg and use 1.1 m/sec speed. I got a di...