Search found 32 matches

by Matt Jacobs 3H
Sat Mar 12, 2016 4:22 pm
Forum: *Organic Reaction Mechanisms in General
Topic: 2014 Final q6 step3
Replies: 1
Views: 303

Re: 2014 Final q6 step3

I got the same thing you did and I'm pretty sure it's correct, I don't know why the answer is shown that way in the solution.
by Matt Jacobs 3H
Sat Mar 12, 2016 1:09 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 2016 Midterm Q8A sig figs
Replies: 1
Views: 183

2016 Midterm Q8A sig figs

I was lost a point for significant figures in my answer to this question which asked for the maximum potential of the cell. There were only two significant figures in the question but the answer has three for some reason. Is there some rule that standard potential of a cell must have three sig figs?...
by Matt Jacobs 3H
Fri Mar 11, 2016 3:55 pm
Forum: *Cyclohexanes (Chair, Boat, Geometric Isomers)
Topic: Drawing the Chair
Replies: 1
Views: 246

Drawing the Chair

When we draw the chair conformation is it necessary to include all of the hydrogens? Usually the question is asking about two substituents on the chair and it seems like a waste of time to also draw in all the hydrogen bonds when they are implied.
by Matt Jacobs 3H
Fri Mar 11, 2016 1:15 am
Forum: *Free Energy of Activation vs Activation Energy
Topic: Question 7B 2012 Final
Replies: 2
Views: 307

Re: Question 7B 2012 Final

That was perfect thank you!
by Matt Jacobs 3H
Fri Mar 11, 2016 12:31 am
Forum: *Free Energy of Activation vs Activation Energy
Topic: Question 7B 2012 Final
Replies: 2
Views: 307

Question 7B 2012 Final

This question is more math than it is chemistry, I understand how they set everything up but there is one math step that I didn't understand:
Why is (e-0.60Ea/RT)/(e-Ea/RT) equal to e0.40Ea/RT?

Can someone please clarify how this result for that step was found?
by Matt Jacobs 3H
Sun Mar 06, 2016 3:27 pm
Forum: *Alcohols
Topic: Phenol example
Replies: 3
Views: 980

Phenol example

There was no forum for phenols so I'm just going to put my question here. On page 56 of the organic chemistry book, on the bottom right there is an example of 2,3,4-Trichlorophenol. The only way to get this numbering is to start at the carbon with the OH group then continue going clockwise. The prob...
by Matt Jacobs 3H
Sun Mar 06, 2016 12:09 pm
Forum: *Haloalkenes
Topic: Priority with double/triple bonds
Replies: 1
Views: 607

Priority with double/triple bonds

When numbering carbons does a double bond get priority over a triple bond for the lowest number or is it the other way around?Or does this question not matter because there will always be other functional group to decide the priority?
by Matt Jacobs 3H
Mon Feb 29, 2016 8:48 pm
Forum: *Alkanes
Topic: quiz 3 prep 1 number 4
Replies: 4
Views: 521

Re: quiz 3 prep 1 number 4

How do you know what vinyl is? I've never heard of it before is it somewhere in the book?
by Matt Jacobs 3H
Fri Feb 26, 2016 11:44 pm
Forum: *Alkenes
Topic: Self-Test 1.5A (b)
Replies: 1
Views: 246

Self-Test 1.5A (b)

The question asks you to write the structural formula for 2-methyl-2-butene, I know how to go about solving this but I had two other questions: 1) For a structural formula is it incorrect to include the double bonds in the formula? For instance (CH 3 ) 2 C=CHCH 3 ? Or should I not include the double...
by Matt Jacobs 3H
Sun Feb 21, 2016 9:12 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 15.65 Effect of temperature on k
Replies: 1
Views: 347

Re: 15.65 Effect of temperature on k

Because the slope of the Arrhenius plot is proportional to E a , it follows that the higher the activation energy, the stronger is the temperature dependence of the rate constant. The equation is lnk= -(E a /R)(1/T) + lna which corresponds to y=mx + b. The slope, m is the (E a /R) term in the Arrhen...
by Matt Jacobs 3H
Wed Feb 10, 2016 12:29 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Delta U and Pressure
Replies: 3
Views: 574

Re: Delta U and Pressure

Yes I understand that much, but why does the temperature decrease when deltaU decreases?
by Matt Jacobs 3H
Tue Feb 09, 2016 9:14 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Delta U and Pressure
Replies: 3
Views: 574

Delta U and Pressure

What is the relationship between the change in internal energy and pressure? How does the sign of deltaU tell you whether the pressure increased or decreased? In the 2011 practice midterm Q1B they explain that "since internal energy decreased the temperature of the gas must decrease, so the pre...
by Matt Jacobs 3H
Tue Feb 02, 2016 11:14 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14.15 c [ENDORSED]
Replies: 3
Views: 468

14.15 c [ENDORSED]

The answer in the solutions manual says: Cd(s)|Cd(OH) 2 (s)|KOH(aq) || Ni(OH) 3 (s)|Ni(OH) 2 (s)|Ni(s) First of all how did they determine this order? I saw in an earlier post Chem.mod said that cell diagrams are typically written to where the reaction proceeds from the outside towards the middle, t...
by Matt Jacobs 3H
Wed Jan 27, 2016 5:38 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Reversible vs Irreversible
Replies: 1
Views: 299

Reversible vs Irreversible

Can someone distinguish which equations are used for reversible processes, which are used for irreversible processes, and which can be used for either reversible or irreversible?
by Matt Jacobs 3H
Sun Jan 24, 2016 3:01 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: HW 9.73
Replies: 1
Views: 227

HW 9.73

Why is it that when deltaS totalr >0 it provides a criterion for assessing the spontaneity of a reaction? I know that deltaS o does not give you enough information to determine spontaneity because it still is dependent on the deltaH o value, but why does the sign of deltaS totalr tell you about spon...
by Matt Jacobs 3H
Thu Jan 21, 2016 5:54 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Example 9.6 page 329
Replies: 2
Views: 312

Example 9.6 page 329

In example 9.6 we are calculating the entropy of vaporization of acetone. The book goes about solving this by calculating three entropy values to then sum together for the total entropy of vaporization: 1) The entropy change accompanying the heating of acetone from it's original temperature to its b...
by Matt Jacobs 3H
Mon Jan 18, 2016 2:17 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: q
Replies: 1
Views: 323

q

Why can q be written as delta H when the pressure is constant?
by Matt Jacobs 3H
Sat Jan 09, 2016 7:51 pm
Forum: Phase Changes & Related Calculations
Topic: Homework 8.25
Replies: 1
Views: 224

Homework 8.25

Can someone explain what the solution manual did? I understand finding the heat capacity and q calorimeter , but why is q reaction + q calorimeter equal to zero? Is it because it is a neutralization reaction? Also the question is asking for the change in internal energy yet that is not solved for in...
by Matt Jacobs 3H
Sat Dec 05, 2015 9:20 pm
Forum: Naming
Topic: "ion"
Replies: 3
Views: 349

"ion"

When is it appropriate to put "ion" after naming a coordination complex? I always see it on an anion, but some cations are labeled with "ion" while others are not.
by Matt Jacobs 3H
Sat Dec 05, 2015 6:15 pm
Forum: Calculating the pH of Salt Solutions
Topic: Going from Ka to pH
Replies: 3
Views: 825

Re: Going from Ka to pH

Thank you!
by Matt Jacobs 3H
Sat Dec 05, 2015 1:39 pm
Forum: *Titrations & Titration Calculations
Topic: Henderson Hasselbalch's equation
Replies: 2
Views: 417

Re: Henderson Hasselbalch's equation

You can always use the Henderson-Hasselbalch when a buffer problem shows up in a titration calculation, i.e. when you know the concentration of a weak acid and it's conjugate base, or the concentration of a weak base and its conjugate acid. You usually have the Pk a already, or you can find it by ta...
by Matt Jacobs 3H
Fri Nov 27, 2015 3:14 pm
Forum: Calculating the pH of Salt Solutions
Topic: Going from Ka to pH
Replies: 3
Views: 825

Going from Ka to pH

In question 12.77 it sets up a problem that seems normal at first. 3.38-g of the sodium salt of alanine is given, which is said to be diluted to 50.0mL. They give you two K a values (K a1 and K a2 ). However, in the solutions manual, they show something completely different to get the answer; they n...
by Matt Jacobs 3H
Sun Nov 22, 2015 2:39 pm
Forum: Amphoteric Compounds
Topic: Determining if oxides are acidic, basic, or amphoteric
Replies: 2
Views: 1644

Determining if oxides are acidic, basic, or amphoteric

How is it possible to tell whether an oxide is acidic, basic, or amphoteric? For example, the oxides BaO, SO3, As2O3, and BiO3 are questioned in homework problem 12.17. Do you have to write out the lewis structure to see what e- pairs are available to be donated or accepted?
by Matt Jacobs 3H
Thu Nov 19, 2015 7:11 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: I do not understand 11.45
Replies: 2
Views: 299

Re: I do not understand 11.45

The 1.2x10-7 is found in Table 11.2 on page 428. Looking at the reaction Cl2 (g) <--> 2Cl (g), the question says that the temperature is 1000k and the corresponding Kc value is 1.2x10-7
by Matt Jacobs 3H
Thu Nov 19, 2015 6:52 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 2013 Quiz 3 Preparation #10
Replies: 10
Views: 999

Re: 2013 Quiz 3 Preparation #10

I have tried this calculation in about 10 different ways and I'm still not getting the answer 1.0 bar. Can someone show how to set up the equation? I want to make sure I'm starting it right
by Matt Jacobs 3H
Tue Nov 10, 2015 6:19 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Using Gibbs free energy to calculate K
Replies: 1
Views: 276

Using Gibbs free energy to calculate K

In the book question 11.29 you are provided with a Q value (in this example Q=1.0) for a reaction (N 2 (g) + O 2 (g) ---> 2NO(g)). The question then asks you to determine whether the reaction will have a tendency to form products or reactants. How do you find the equilibrium constant value K using t...
by Matt Jacobs 3H
Sun Nov 08, 2015 1:01 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Determining if ligands can be polydentate
Replies: 1
Views: 256

Determining if ligands can be polydentate

How does one know how many lone pairs are on an atom? For example, on the ligand HN(CH 2 CH 2 NH 2 ) 2 , I am aware that this ligand can be polydentate because it has three nitrogens each with a lone pair that are available for bonding to a metal center. But how do we know that each nitrogen has tha...
by Matt Jacobs 3H
Mon Oct 26, 2015 5:23 pm
Forum: Hybridization
Topic: Increasing the s-character of Hybrid Orbitals
Replies: 1
Views: 1021

Increasing the s-character of Hybrid Orbitals

When you increase the s-character of a hybrid orbital, how does that effect the bond angle? For example, if you have a sp 3 hybrid orbital (which has a bond angle of 109.5 degrees), would increasing the s-character increase the bond angle or decrease the bond angle between two hybrid orbitals? Is th...
by Matt Jacobs 3H
Sun Oct 25, 2015 3:53 pm
Forum: Resonance Structures
Topic: Resonance structure of five N atoms
Replies: 2
Views: 877

Resonance structure of five N atoms

The N 5 + cation, in which five N atoms are connected in a long chain. How would you draw the resonance structures of this ion? It is confusing trying to determine where the double bonds and triple bonds and lone pair electrons are placed. Is there a certain process to do this on this complex struct...
by Matt Jacobs 3H
Fri Oct 16, 2015 5:41 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Determining principle quantum number
Replies: 1
Views: 337

Determining principle quantum number

When you start getting into elements that are located in the first row of the d-block, such as iron (Fe), is the principle quantum number (n) still equal to 4? Or would it be 3 because now electrons are starting to be added to the 3d orbitals? I always had in mind that the principle quantum number w...
by Matt Jacobs 3H
Fri Oct 09, 2015 2:36 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Finding n values in Rydberg
Replies: 1
Views: 368

Finding n values in Rydberg

Lines in the Balmer series of the hydrogen spectrum are observed at 656.3, 486.1, 434.0, and 410.2 nm. What is the wavelength of the next line in the series?

I am wondering how you configure the n values in the Rydberg equation to find the frequency and thus the wavelength?
by Matt Jacobs 3H
Wed Sep 30, 2015 9:50 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Molar Mass and Metal/Sulfides
Replies: 1
Views: 2573

Molar Mass and Metal/Sulfides

The molar mass of the metal hydroxide M(OH)2 is 74.10 g/mol. What is the molar mass of the sulfide of this metal?
Can someone please explain what the sulfide of a metal is, and how it's molar mass differs from the metal. Thanks.

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