Search found 48 matches

by Saira Shahid 3K
Sun Mar 13, 2016 12:40 pm
Forum: *Cyclohexanes (Chair, Boat, Geometric Isomers)
Topic: Chair Flip
Replies: 2
Views: 363

Re: Chair Flip

Thanks!
by Saira Shahid 3K
Sun Mar 13, 2016 12:23 pm
Forum: *Alkanes
Topic: Substituents vs. Functional Groups
Replies: 2
Views: 405

Re: Substituents vs. Functional Groups

Thank you, Kelly!
by Saira Shahid 3K
Sun Mar 13, 2016 12:23 pm
Forum: *Cyclohexanes (Chair, Boat, Geometric Isomers)
Topic: Chair Flip
Replies: 2
Views: 363

Chair Flip

What is the purpose of the chair flip?
by Saira Shahid 3K
Sun Mar 13, 2016 11:50 am
Forum: *Alkanes
Topic: Substituents vs. Functional Groups
Replies: 2
Views: 405

Substituents vs. Functional Groups

What's the difference between substituents and functional groups? Are methyl, ethyl, propyl, etc. substituents or functional groups?
by Saira Shahid 3K
Sun Mar 06, 2016 9:12 pm
Forum: *Cycloalkenes
Topic: difference between benzene and 1,3,5-cyclohexatriene
Replies: 1
Views: 6804

Re: difference between benzene and 1,3,5-cyclohexatriene

For your first question, I believe that the main difference is bond length. This article goes more in depth: https://chemicaltan97.wordpress.com/2014/09/24/why-benzene-is-not-135-cyclohexatriene/
by Saira Shahid 3K
Sat Mar 05, 2016 12:04 pm
Forum: Administrative Questions and Class Announcements
Topic: Online Participation Points In-Advance
Replies: 3
Views: 697

Re: Online Participation Points In-Advance

Yeah, I'm pretty sure you can't make up missed points.
by Saira Shahid 3K
Fri Mar 04, 2016 1:47 pm
Forum: *Alkanes and Substituted Alkanes (Staggered, Eclipsed, Gauche, Anti, Newman Projections)
Topic: Comparing Conformation Stability
Replies: 2
Views: 342

Comparing Conformation Stability

Why is the chair conformation the most stable, and why does it have no steric strain or torsional strain?
by Saira Shahid 3K
Wed Mar 02, 2016 3:17 pm
Forum: *Electrophiles
Topic: Electrophiles and Central Atoms
Replies: 2
Views: 401

Re: Electrophiles and Central Atoms

ok
by Saira Shahid 3K
Sun Feb 28, 2016 1:23 pm
Forum: *Electrophiles
Topic: Electrophiles and Central Atoms
Replies: 2
Views: 401

Electrophiles and Central Atoms

Are central atoms always electrophiles?
by Saira Shahid 3K
Fri Feb 05, 2016 9:57 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs Free Energy and Partial Pressures (2011 Midterm Q4)
Replies: 1
Views: 206

Gibbs Free Energy and Partial Pressures (2011 Midterm Q4)

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Question
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Solution
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I'm having trouble on Question 4 of the 2011 midterm. I did all the steps correctly, but I got stuck when solving for the partial pressures. Can someone explain to me how to get the part I circled (2x/x2)?
by Saira Shahid 3K
Wed Feb 03, 2016 10:44 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Winter 2011 Midterm Practice Q 1A
Replies: 2
Views: 300

Re: Winter 2011 Midterm Practice Q 1A

You put a negative there to cancel out the other negative (the entropy) since heat capacity always has to be positive
by Saira Shahid 3K
Tue Feb 02, 2016 9:17 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Entropy
Replies: 1
Views: 261

Re: Entropy

Monatomic gasses have a larger number of particles than diatomic gasses, so it has a higher change in entropy. As for vibrational active molecules, a gas with molecules that are vibrationally active has additional vibrational states than if the molecules were not vibrationally active. Since it has m...
by Saira Shahid 3K
Tue Feb 02, 2016 6:06 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Residual entropy and statistical entropy
Replies: 1
Views: 263

Re: Residual entropy and statistical entropy

I found this answer in a previous thread where Dr. Lavelle explains them both. Hope this helps! The formula S = k ln(W) is sometimes called statistical entropy. Here W is the number of states that a system can exist in, each state having the same energy. Residual entropy is the same thing but one is...
by Saira Shahid 3K
Mon Feb 01, 2016 7:49 pm
Forum: Administrative Questions and Class Announcements
Topic: Online Participation Points In-Advance
Replies: 3
Views: 697

Online Participation Points In-Advance

If we post on Chemistry Community twice in one week, does it count for two weeks? Or do we still have to post the following week?
by Saira Shahid 3K
Mon Feb 01, 2016 5:19 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Internal Energy and Temperature
Replies: 1
Views: 331

Internal Energy and Temperature

How is temperature related to internal energy? On the Winter 2011 midterm, question 1B, it says "since the internal energy decreased, the temperature of the gas must decrease." Why is this?
by Saira Shahid 3K
Fri Jan 29, 2016 12:06 am
Forum: Phase Changes & Related Calculations
Topic: Change in Internal Energy of Ideal Gas
Replies: 1
Views: 319

Change in Internal Energy of Ideal Gas

How do I find the change in internal energy of an ideal gas that's expanding isothermally and reversibly? I tried using deltaH-delta(n)RT but I don't think I got the right answer.
by Saira Shahid 3K
Mon Jan 25, 2016 11:12 pm
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: Residual Entropy
Replies: 5
Views: 1066

Re: Residual Entropy

Residual entropy is the difference in entropy between a non-equilibrium state and crystal state of a substance at a temperature close to 0 K. I believe you use the equation S=KblnW to solve for it, where S is entropy, K is a constant, and W is degeneracy.
by Saira Shahid 3K
Sun Jan 24, 2016 11:55 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Finding Standard Reaction Entropy Using Molar Entropies
Replies: 1
Views: 213

Finding Standard Reaction Entropy Using Molar Entropies

How do we find the standard reaction entropy if not all molar entropies are listed in our reference sheet? For example, I can't find the standard molar entropy of C6H6 in liquid state.
by Saira Shahid 3K
Sat Jan 23, 2016 5:43 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Comparing Molar Heat Capacities of Substances
Replies: 1
Views: 226

Comparing Molar Heat Capacities of Substances

Is molar heat capacity higher for a substance that is more complex? For example, does CO2 have a higher molar heat capacity than CO because it has more atoms?
by Saira Shahid 3K
Sat Jan 23, 2016 5:33 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat Capacity
Replies: 6
Views: 717

Re: Heat Capacity

Yes, the phase of the substance affects its heat capacity.
by Saira Shahid 3K
Tue Jan 19, 2016 3:39 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Entropy
Replies: 1
Views: 262

Re: Entropy

W is degeneracy, the number of ways of achieving a given energy state. This is not to be confused with w, which is work.
by Saira Shahid 3K
Thu Jan 07, 2016 8:22 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Using Bond Enthalpies in Calculations
Replies: 3
Views: 401

Using Bond Enthalpies in Calculations

I'm confused on how to calculate the change in heat of the reaction by using bond enthalpies. For example, we can refer to the second example on page 18 of the course reader. How do we know which bonds are broken and which are formed?
by Saira Shahid 3K
Sat Dec 05, 2015 9:33 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Shape
Replies: 2
Views: 333

Re: Shape

I draw or visualize the structure to see how many binding sites there are. For some ligands, you can memorize if they're monodentate or polydenate. For example, H20 is always monodentate and en is is always bidentate.
by Saira Shahid 3K
Sat Dec 05, 2015 9:30 pm
Forum: Naming
Topic: "ion"
Replies: 3
Views: 367

Re: "ion"

You put "ion" at the end if the coordination compound has a net electric charge. If the positive and negative charges cancel out, there is no need to put "ion".
by Saira Shahid 3K
Sat Dec 05, 2015 9:26 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: pH of a buffer solution
Replies: 1
Views: 444

Re: pH of a buffer solution

Did you try using the Henderson-Hasselbalch equation?
by Saira Shahid 3K
Sat Dec 05, 2015 9:23 pm
Forum: Identifying Acidic & Basic Salts
Topic: Salts: Solubility of Ionic Compounds in Water
Replies: 1
Views: 418

Re: Salts: Solubility of Ionic Compounds in Water

Solubility is when a solute dissolves in a solvent. In this case, the salt is the solute and the solvent is water. Learning about the solubility of ionic compounds is important for solving titrations and other problems in organic chemistry.
by Saira Shahid 3K
Sat Dec 05, 2015 9:19 pm
Forum: *Titrations & Titration Calculations
Topic: Titration Cheat Sheet
Replies: 1
Views: 1478

Re: Titration Cheat Sheet

Thanks you're a true pal
by Saira Shahid 3K
Sat Dec 05, 2015 9:17 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: strength of acids/ bases
Replies: 3
Views: 551

Re: strength of acids/ bases

Become familiar with the chart on page 151 in the course reader. I think you just have to know these common acids and bases. If it's an uncommon one, the problem will probably state whether is a strong or weak acid/base.
by Saira Shahid 3K
Sat Dec 05, 2015 9:14 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Shape of compounds
Replies: 1
Views: 366

Re: Shape of compounds

A coordination compound is octahedral when there are six things bonded to the transition metal. Br is monodentate, so (Br)2 binds at two sites. en is bidentate, so (en)2 binds at four sites. So in total, there are six binding sites, which makes it octahedral.
by Saira Shahid 3K
Fri Dec 04, 2015 11:14 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Is Kw always 10^-14?
Replies: 2
Views: 584

Is Kw always 10^-14?

In this class, do we always use 10^-14 as the value for Kw?
by Saira Shahid 3K
Tue Dec 01, 2015 3:52 pm
Forum: Identifying Acidic & Basic Salts
Topic: Determine if salt is acidic, basic, or neutral
Replies: 4
Views: 2359

Re: Determine if salt is acidic, basic, or neutral

Thanks! So should we memorize the chart if we're not familiar with it?
by Saira Shahid 3K
Tue Dec 01, 2015 3:07 pm
Forum: Identifying Acidic & Basic Salts
Topic: Determine if salt is acidic, basic, or neutral
Replies: 4
Views: 2359

Re: Determine if salt is acidic, basic, or neutral

How do you know if an acid/base is strong or weak?
by Saira Shahid 3K
Thu Nov 26, 2015 1:03 pm
Forum: Student Social/Study Group
Topic: Effective Studying Methods?
Replies: 1
Views: 741

Effective Studying Methods?

What's the most effective way you study for finals? And how do you stop procrastinating and find motivation to study?
by Saira Shahid 3K
Wed Nov 18, 2015 4:33 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Polydentate and Lewis Structure
Replies: 4
Views: 649

Re: Polydentate and Lewis Structure

Okay thanks! Do we also draw the Lewis structure to find the coordination number?
by Saira Shahid 3K
Wed Nov 18, 2015 11:38 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Polydentate and Lewis Structure
Replies: 4
Views: 649

Polydentate and Lewis Structure

To find out how many sites there are to bind to the central metal atom/ion, do we have to draw the Lewis structure?
by Saira Shahid 3K
Sat Nov 14, 2015 10:48 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Polydentate and Oxidation Numbers
Replies: 4
Views: 761

Re: Polydentate and Oxidation Numbers

So to find out how many sites there are to bind to the central metal atom/ion, do we have to draw the Lewis structure?
by Saira Shahid 3K
Wed Nov 11, 2015 9:29 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium and Disassociation of a Diatomic Molecule (11.7)
Replies: 4
Views: 1880

Equilibrium and Disassociation of a Diatomic Molecule (11.7)

I'm having trouble with this question (11.7): The following flasks show the dissociation of a diatomic molecule, X2, over time (picture attached). (a) Which flask represents the point in time at which the reaction has reached equilibrium? (b) What percentage of the X2 molecules have decomposed at eq...
by Saira Shahid 3K
Wed Nov 11, 2015 8:39 pm
Forum: Administrative Questions and Class Announcements
Topic: On Page 7 in the Course Reader
Replies: 1
Views: 497

Re: On Page 7 in the Course Reader

They're for chapter 11, as written on page 120
by Saira Shahid 3K
Mon Nov 02, 2015 10:49 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Divide Between N and O in Periodic Table
Replies: 1
Views: 163

Divide Between N and O in Periodic Table

I know that there's a divide between N and O in the periodic table and that MO diagrams to the left of the divide look different from MO diagrams to the right of the divide. I was wondering what the reason is for that difference.
by Saira Shahid 3K
Thu Oct 29, 2015 12:02 am
Forum: Hybridization
Topic: Sigma and Pi Bonds
Replies: 4
Views: 918

Re: Sigma and Pi Bonds

Sigma and pi bonds are made when two orbitals overlap. Sigma bonds are made when two hybridized orbitals overlap, and pi bonds are always made from two P-orbitals. A single bond is a sigma bond. A double bond is one sigma and one pi bond. A triple bond is one sigma and two pi bonds. I always draw th...
by Saira Shahid 3K
Thu Oct 22, 2015 5:00 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Molecular Shape and Biological Activity
Replies: 1
Views: 278

Molecular Shape and Biological Activity

How does a molecule's shape determine it's biological activity (odor, taste, etc.)? Can someone give me an example? Thanks.
by Saira Shahid 3K
Thu Oct 22, 2015 4:35 pm
Forum: Student Social/Study Group
Topic: Top of the Hill Study Group
Replies: 5
Views: 925

Re: Top of the Hill Study Group

Sorry I just read your replies! I'd be down to form a study group for Quiz 2. I'll send you guys an email.
by Saira Shahid 3K
Sun Oct 18, 2015 4:22 pm
Forum: Student Social/Study Group
Topic: Exams
Replies: 1
Views: 552

Re: Exams

I found the quiz difficult too, but it was my fault that I waited until the last minute to study. I would recommend doing all the practice quizzes in the workbook. Also reread your notes after each lecture; it helps you retain the information. And don't procrastinate on doing the homework problems. ...
by Saira Shahid 3K
Sat Oct 17, 2015 4:02 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Number of Atomic Orbitals
Replies: 1
Views: 312

Number of Atomic Orbitals

What's the reason we have one s-orbital, three p-orbitals, five d-orbitals, and seven f-orbitals? Is the number of orbitals related to the periodic table?
by Saira Shahid 3K
Sat Oct 10, 2015 8:37 pm
Forum: Empirical & Molecular Formulas
Topic: Name of Formula to Molecular Formula, and Vice Versa
Replies: 3
Views: 622

Re: Name of Formula to Molecular Formula, and Vice Versa

I was wondering the same thing. For example, why is the formula for nitric acid HNO3?
by Saira Shahid 3K
Fri Oct 09, 2015 6:17 pm
Forum: Student Social/Study Group
Topic: Top of the Hill Study Group
Replies: 5
Views: 925

Top of the Hill Study Group

Does anyone at Hedrick Hall, Hedrick Summit, or Hitch want to form a study group? We can meet up this weekend to study for the quiz next week. Let me know if anyone's interested!

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