Search found 53 matches

by Mara Lockhart 3J
Thu Mar 12, 2015 10:58 am
Forum: *Constitutional and Geometric Isomers (cis, Z and trans, E)
Topic: E/Z Configuration: 2011 Final Question 7B
Replies: 5
Views: 755

E/Z Configuration: 2011 Final Question 7B

For question 7B on the 2011 final, we are asked to give the IUPAC name of the structure (as seen in the attachment). I feel comfortable with naming the structure, up until deciding if it is E or Z. I through the molecule was E, because COOH gets the priority on one C and CH2 get the priority on the ...
by Mara Lockhart 3J
Mon Mar 09, 2015 8:04 pm
Forum: *Alkanes
Topic: Do dashes in naming matter
Replies: 3
Views: 600

Do dashes in naming matter

If you are naming a structure that is 2-methylbutane, but wrote it as 2-methyl-butane, would you still get full credit? Does having the dash in-between methyl and butane matter? If so, how?
by Mara Lockhart 3J
Mon Mar 09, 2015 8:01 pm
Forum: *Cycloalkenes
Topic: Diene
Replies: 4
Views: 747

Re: Diene

Oh. okay! Thank you, so if there was three double bonds, it would be trinene?
by Mara Lockhart 3J
Mon Mar 09, 2015 6:45 pm
Forum: *Cycloalkenes
Topic: Diene
Replies: 4
Views: 747

Diene

When naming the cycloalkenes, why do we put diene as oppose to just -ene? (We can see this on problem 1.21 in the Organic Chemistry Textbook).
by Mara Lockhart 3J
Sat Mar 07, 2015 4:32 pm
Forum: *Constitutional and Geometric Isomers (cis, Z and trans, E)
Topic: Naming Alkenes
Replies: 2
Views: 507

Naming Alkenes

On number 25 in the yellow Introduction to Organic Chemistry textbook, I am confused on how you name the alkene. I was confused and looked at the answer, but it confused me even more. I know it is Z (or cis) because the two largest molecules are on the same side, and on the bottom of each sidearm me...
by Mara Lockhart 3J
Tue Feb 24, 2015 9:06 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Sample problem involving equilibrium
Replies: 2
Views: 541

Re: Sample problem involving equilibrium

Hello! We could see a problem that could involve calculating the temperature a reaction would occur at. I will use a first order reaction as an example. As you stated, at equilibrium the rate constant, k, is the same as the reverse rate constant, k', so a problem could involve knowing that the two a...
by Mara Lockhart 3J
Tue Feb 24, 2015 8:37 pm
Forum: General Rate Laws
Topic: Reverse Rate
Replies: 2
Views: 562

Re: Reverse Rate

Okay, that makes sense. Thank you.
by Mara Lockhart 3J
Sun Feb 22, 2015 10:40 pm
Forum: General Rate Laws
Topic: Reverse Rate
Replies: 2
Views: 562

Reverse Rate

Why is the reverse rate the same as the forward rate? This is seen in number 14.91, I just don't get why they're the same. Thank you!
by Mara Lockhart 3J
Sat Feb 21, 2015 10:22 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: Reaction rate for specific reactants
Replies: 2
Views: 557

Re: Reaction rate for specific reactants

Oh, okay! That makes sense! Thank you!
by Mara Lockhart 3J
Sat Feb 21, 2015 8:23 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: Reaction rate for specific reactants
Replies: 2
Views: 557

Reaction rate for specific reactants

When calculating the order for each reactant, how do you know what experiments to use. For example, in problem 14.15, to find the order for A, when you use experiments 2 and 4, you get 2^a=2, so a=1. However when you use experiments 3 and 4, you get a completely different answer for a, as you get 2^...
by Mara Lockhart 3J
Sat Feb 21, 2015 8:18 am
Forum: General Rate Laws
Topic: Unique rate law
Replies: 5
Views: 1325

Re: Unique rate law

Whats the difference of the two? On question 14.5, the question just asked what is the unique rate of the reaction, so are they asking for the unique average rate or the unique rate law?
by Mara Lockhart 3J
Fri Feb 20, 2015 7:56 pm
Forum: General Rate Laws
Topic: Unique rate law
Replies: 5
Views: 1325

Re: Unique rate law

I think I found the answer to my own question, but if anyone has additional comments, please add on! To find the unique rate of a reaction, you take the rate (of any product or reactant) and divide by the stoichiometric coefficient of that chosen species. It does not matter what rate you choose, bec...
by Mara Lockhart 3J
Fri Feb 20, 2015 7:31 pm
Forum: General Rate Laws
Topic: Unique rate law
Replies: 5
Views: 1325

Unique rate law

In kinetics, what does a unique rate law mean?
by Mara Lockhart 3J
Sat Feb 07, 2015 5:39 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Finding Partial Pressures
Replies: 5
Views: 822

Re: Finding Partial Pressures

Thank you! I had forgotten how to calculate x and use the products over reactants, but this was super helpful!
by Mara Lockhart 3J
Sat Feb 07, 2015 9:20 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard Enthalpy Midterm 2011 2.A
Replies: 1
Views: 465

Standard Enthalpy Midterm 2011 2.A

For question 2.A in the 2011 midterm, why do we have to use the HCl-->HCl and AlCl3---->AlCl3 and their standard enthalpies when finding the standard reaction enthalpy? If we only use the 2Al(s) + 6HCl(aq)--->2AlCl3+ 3H2 and H2(g) + 3Cl2(g)----> 2HCl(g), we are able to still form the final reaction,...
by Mara Lockhart 3J
Fri Feb 06, 2015 3:21 pm
Forum: Balancing Redox Reactions
Topic: Determining Oxidation numbers
Replies: 2
Views: 537

Determining Oxidation numbers

For problem 13.1, part a asks us to identify the elements undergoing changes in oxidation state and indicate the initial and final oxidation numbers for these elements. I am not sure how to to find the initial and final (the solutions manual got C was oxidized from 2- to 1-). How do we identify thes...
by Mara Lockhart 3J
Thu Feb 05, 2015 2:27 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Finding Partial Pressures
Replies: 5
Views: 822

Finding Partial Pressures

I am not sure if we will need to be able to do this on the midterm, but for problem 10.105, we are asked a series of multiple questions. Part C. of this problem asks us to find the partial pressures of each of the gases when the system reaches equilibrium. I understand to set up the table and you ha...
by Mara Lockhart 3J
Thu Feb 05, 2015 11:43 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Calculating Delta G, Delta S, and Delta H
Replies: 3
Views: 2050

Re: Calculating Delta G, Delta S, and Delta H

Okay! That makes a lot more sense! Thank you
by Mara Lockhart 3J
Thu Feb 05, 2015 11:42 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Phases for Sodium Metal
Replies: 2
Views: 470

Re: Phases for Sodium Metal

Thank you! I did not see the question had been asked previously. but I appreciate the further clarification!!
by Mara Lockhart 3J
Tue Feb 03, 2015 4:12 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Phases for Sodium Metal
Replies: 2
Views: 470

Phases for Sodium Metal

In problem 8.105, the question states NaN3 goes to form nitrogen gas and sodium metal, but they put (g) next to Na in the balanced reaction. Why is Sodium metal written in gas form?
by Mara Lockhart 3J
Tue Feb 03, 2015 3:58 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Calculating Delta G, Delta S, and Delta H
Replies: 3
Views: 2050

Calculating Delta G, Delta S, and Delta H

For problem 8.101 in the book, I am confused as to what products and reactants are to be used for the standard enthalpies and entropies. Well, now looking at it more, I am just confused over all. Could some one explain how we use the lewis structures and compounds to find the Delta H, Delta S, and D...
by Mara Lockhart 3J
Fri Jan 30, 2015 10:17 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: Does degeneracy = 0?
Replies: 6
Views: 1010

Re: Does degeneracy = 0?

Okay, thank you! Could degeneracy be undefined ever? Or is degeneracy always going to be a whole number greater than 0?
by Mara Lockhart 3J
Sat Jan 24, 2015 8:56 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: Does degeneracy = 0?
Replies: 6
Views: 1010

Does degeneracy = 0?

Will or does degeneracy, W, ever equal 0? If so, under what circumstances would make it 0 (a specific phase, isothermal, isobaric, reversible, irreversible)?
by Mara Lockhart 3J
Wed Jan 21, 2015 7:17 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Finding the change in entropy with volume and temperature
Replies: 2
Views: 467

Finding the change in entropy with volume and temperature

For problem numer 8.11 in the textbook and Q4.A on the 2010 Winter Midterm (they are the same question), we are asked to calculate the change in entropy of the gas. We are given a situation of a decrease of volume and simultaneously an increase in the heat. This question is regarding nitrogen and in...
by Mara Lockhart 3J
Tue Jan 20, 2015 9:42 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Generating entropy - the usage of signs
Replies: 3
Views: 383

Generating entropy - the usage of signs

When calculating the change in entropy, we use the equation deltaS=q/T. For problem 8.1, we use this equation and specifically use the rate of heat generation over temperature; however, the solutions manual uses a negative sign in front of the equation in the work, but not in the answer. Where did t...
by Mara Lockhart 3J
Mon Jan 19, 2015 11:08 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Calculating Bond Enthalpies - #7.115
Replies: 6
Views: 596

Calculating Bond Enthalpies - #7.115

On part (b) of problem 7.115, we are asked to use bond enthalpies to calculate the enthalpy of combustion of each fuel, assuming they burn to produce gaseous CO2 and gaseous H2O. For CH4, I know we have to find all of the enthalpies and add them together, but why do the products, CO2 and H20, have n...
by Mara Lockhart 3J
Sun Jan 18, 2015 4:44 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Error in Solutions Manual 7.99
Replies: 1
Views: 317

Re: Error in Solutions Manual 7.99

Although the molar mass of CO2 was not correct in the solutions manual, the answer in the solutions manual and correct answer are still the same! :) (The solutions manual go 0.4873 g CO2 and I calculated, with the correct molar mass, a final mass of CO2 as 0.4973)
by Mara Lockhart 3J
Sat Jan 17, 2015 3:26 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Reaction Enthalpies - #7.53
Replies: 3
Views: 450

Re: Reaction Enthalpies - #7.53

Thank you both! I had gotten stuck, but this helped a lot.
by Mara Lockhart 3J
Sat Jan 17, 2015 2:15 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy Density and TNT
Replies: 2
Views: 583

Enthalpy Density and TNT

For number 7.55, we are asked to find the enthalpy density of TNT. We first find the enthalpy of reaction, which comes out to be -13168 kj/mol. Why do we only use one fourth of this amount of energy for the amount that will be released per mole of TNT consumed?
by Mara Lockhart 3J
Sat Jan 17, 2015 1:25 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Reaction Enthalpies - #7.53
Replies: 3
Views: 450

Reaction Enthalpies - #7.53

To calculate the change in temperature of solution, we have to plug into the equation q=mCsdeltaT. For the q, I am confused as to where -20,000 came from? The question gave a hint of "Assume the density and molar heat capacity of the hydrochloric acid solution are the same as those of water and...
by Mara Lockhart 3J
Wed Jan 14, 2015 4:57 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hess's Law, Multiplying Coefficients
Replies: 2
Views: 4914

Hess's Law, Multiplying Coefficients

On problem 7.63, we have to find the balanced equations of three reactions and for one of the reactions, we find it to be H2(g) + 1/2O2(g) ---> H20. We then have to multiply the reaction by 2, leading us to multiply the delta H by two as well. However, why can't we just have the reaction as 2H2 + O2...
by Mara Lockhart 3J
Sat Jan 10, 2015 9:19 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Contribution to the heat capacity
Replies: 3
Views: 1829

Contribution to the heat capacity

How do you predict the contribution to the heat capacity, in this case Cv,m, made by molecular motions for a molecule or atom, for example C2H6? or Ar? (Also, what does the "m" in Cv,m stand for?)
by Mara Lockhart 3J
Sat Jan 10, 2015 8:59 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Molar heat capacity of an ideal monatomic gas
Replies: 1
Views: 535

Molar heat capacity of an ideal monatomic gas

For textbook question 7.27, we are asked to find the heat released by 5.025g of Kr(g) at 0.400 atm as it cools from 97.6 degree celsius to 25 degree celsius. For part (a) we are asked to find this at a constant pressure. For the Cp,m, how does the book get 5/2 (where do those number come from? Also,...
by Mara Lockhart 3J
Tue Dec 09, 2014 11:13 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Determining what the pH of an aqueous solution of slats
Replies: 1
Views: 501

Determining what the pH of an aqueous solution of slats

For homework question 11.71, we are asked to determine an aqueous solution of each of the following salts has a pH equal to, greater than, or less than 7. For part (e), which is AlCl3 and part (f), which is C5H5NHCl, how do you determine the pH. More specifically how does the reaction for AlCl3 beco...
by Mara Lockhart 3J
Wed Dec 03, 2014 4:09 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Calculating the concentration of OH-
Replies: 1
Views: 307

Calculating the concentration of OH-

On HW Question 11.35, I understand how the concentration of [H+] was calculated, but I am confused on how the concentration of [OH-] was calculated. We are given pH=13.25.
by Mara Lockhart 3J
Wed Dec 03, 2014 11:12 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: HW Question 11.33
Replies: 1
Views: 294

HW Question 11.33

We are asked to convert pH values into the molarity of H3O+. I see from the solutions manual, to do this, we have to take the anti log of the pH value, but why is this?
by Mara Lockhart 3J
Tue Dec 02, 2014 11:04 am
Forum: Lewis Acids & Bases
Topic: HW Question 11.17
Replies: 3
Views: 565

HW Question 11.17

For part (b), why is the Lewis structure of SO2 written with only one double bond? Shouldn't it be two double bonds to satisfy the formal charges?
by Mara Lockhart 3J
Tue Dec 02, 2014 9:19 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: SigFigs in finding concentration problems
Replies: 1
Views: 356

Re: SigFigs in finding concentration problems

Three sig figs are used in the final answer because the amount of moles given to us all have three sig figs, for example 0.245 mol SO3 and 0.240 mol SO2. When finding the amount of moles of NO that must be added to a 1.00-L vessel, we will write the final answer with having three sig figs as well to...
by Mara Lockhart 3J
Tue Dec 02, 2014 9:11 am
Forum: Conjugate Acids & Bases
Topic: HW Question 11.9
Replies: 1
Views: 393

HW Question 11.9

For this question, we are asked which of the following reactions can be classified as reactions between Bronsted acids and bases. For those that can be classified, we are asked to identify the acid and base. In part (c) of this question, CH 3 COOH(aq) + NH 3 (aq) ---> CH 3 CONH 2 (aq) + H 2 O (l) is...
by Mara Lockhart 3J
Tue Nov 25, 2014 11:26 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Homework Question 69
Replies: 5
Views: 603

Homework Question 69

For this question, we are given the reaction 2HCl(g) ---> H2(g) + Cl2 (g), which has K=3.2x10^-34 at 298 . The initial partial pressure are H2 1.0 bar, HCl 2.0 bar, and Cl2 3.0 bar. At equilibrium there ia 1.0 mol H2 (g). We are asked to find the volume of the container. I drew out the I.C.E box, ho...
by Mara Lockhart 3J
Sun Nov 23, 2014 1:05 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: HW Question 10.37
Replies: 2
Views: 401

Re: HW Question 10.37

Thank you! This helped a lot!
by Mara Lockhart 3J
Sun Nov 23, 2014 11:25 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: HW Question 10.37
Replies: 2
Views: 401

HW Question 10.37

Given the reaction N(2)(g)+3H(2)(g)-->2NH(3)(g) at 400.K, K=41. We are asked to find the value of K for each of the following reactions at the same temperature including (a) 2NH(3)(g)--->N(2)+3H(2)(g). For part a, I know K=[N(2)][H(2)]^3/[NH(3)]^2, but I am confused as to how we find the vale of K w...
by Mara Lockhart 3J
Sun Nov 09, 2014 8:34 pm
Forum: Hybridization
Topic: Midterm Prep -Fall 2012
Replies: 3
Views: 442

Re: Midterm Prep -Fall 2012

Where is the other H bond?
by Mara Lockhart 3J
Sat Nov 08, 2014 11:01 pm
Forum: Lewis Structures
Topic: Midterm Prep - Fall 2012 question 5 B. in course reader
Replies: 1
Views: 318

Midterm Prep - Fall 2012 question 5 B. in course reader

For question 5 B. in the Fall 2012 course reader midterm prep, we are asked to determine which gases can contribute to global warming by writing the Lewis structures. For (a)CO, I wrote it with 0 formal charges, making it so it would not contribute to global warming, however the course reader has th...
by Mara Lockhart 3J
Sat Nov 08, 2014 10:49 pm
Forum: Hybridization
Topic: Midterm Prep -Fall 2012
Replies: 3
Views: 442

Midterm Prep -Fall 2012

On question 6.A, it asks us what is the hybridization of the carbon atoms in the ring structure. I found it to have a hybridization of sp2, but the course reader answer tells us it is sp3. Why is this? It only has 3 regions of electron density.
by Mara Lockhart 3J
Tue Nov 04, 2014 11:22 am
Forum: Administrative Questions and Class Announcements
Topic: Uploading Multimedia
Replies: 2
Views: 421

Re: Uploading Multimedia

Thank you!!
by Mara Lockhart 3J
Sat Nov 01, 2014 3:19 pm
Forum: Lewis Structures
Topic: Problem 2.57 in textbook
Replies: 2
Views: 392

Re: Problem 2.57 in textbook

Thank you!
by Mara Lockhart 3J
Sat Nov 01, 2014 8:56 am
Forum: Administrative Questions and Class Announcements
Topic: Uploading Multimedia
Replies: 2
Views: 421

Uploading Multimedia

I tired to look at the instruction on how to upload multimedia and it says a password is needed. What is the password we are supposed to type in?
by Mara Lockhart 3J
Fri Oct 31, 2014 8:46 pm
Forum: Lewis Structures
Topic: Problem 2.57 in textbook
Replies: 2
Views: 392

Problem 2.57 in textbook

In problem 2.57 in the textbook, we are asked to write the Lewis Structure of reactive species and indicate which are radicals. In part (a), we are given ClO. In the Lewis Structure of ClO, Cl does not fulfill the octet rule. Is this okay in this certain situation? If so, why is it able to break the...
by Mara Lockhart 3J
Thu Oct 09, 2014 4:45 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Negative Frequencies when using the Rydberg Formula
Replies: 1
Views: 389

Negative Frequencies when using the Rydberg Formula

For questions such as number 1.7 on the suggested homework, when we are using the Rydberg formula , frequency=R[1/(n1)^2-1/(n2)^2], to calculate wavelength for the transition from one energy level to another and we come across a negative number as the answer for the frequency, do we keep the negativ...

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