Search found 27 matches

by edward_qiao_3I
Thu Mar 16, 2017 5:54 pm
Forum: *Alkanes and Substituted Alkanes (Staggered, Eclipsed, Gauche, Anti, Newman Projections)
Topic: How to tell whether a molecule is eclipsed or staggered by looking at the 2D repersentation?
Replies: 4
Views: 994

Re: How to tell whether a molecule is eclipsed or staggered by looking at the 2D repersentation?

To add on to this, you can tell mostly because the Newman projection gives you the 2-D image looking along the C-C bond - think of it as facing C1 head-on so that C2 is perfectly behind it. Staggered and eclipsed just refer to the positions of the hydrogens in this radial image - staggered means tha...
by edward_qiao_3I
Fri Mar 10, 2017 12:28 am
Forum: *Haloalkanes
Topic: Introduction to Organic Chem ch. 4 #31
Replies: 2
Views: 444

Re: Introduction to Organic Chem ch. 4 #31

The reaction is two steps because it creates intermediates. The slower step is determined by which one takes more energy, which in this case means breaking more bonds. Step one breaks one pi and one sigma bond, while step two only forms bonds, so step one takes more energy
by edward_qiao_3I
Fri Mar 10, 2017 12:24 am
Forum: *Alkanes
Topic: Tert vs. Neo?
Replies: 4
Views: 468

Re: Tert vs. Neo?

Not necessarily - tert is used for when the first Carbon, the Carbon attached to the R-group, we'll say, is attached to three other carbons. Neo is used specifically for a tail end Carbon that is connected to three other carbons.
by edward_qiao_3I
Tue Mar 07, 2017 11:11 pm
Forum: *Cycloalkanes
Topic: 3-Ethyl,1,1-dimethyl-2-propylcyclohexane
Replies: 1
Views: 218

3-Ethyl,1,1-dimethyl-2-propylcyclohexane

On page 21 of the OChem reader at the bottom, why is this structure not 1-ethyl-3,3-dimethyl-2-propylcyclohexane since ethyl comes first alphabetically
by edward_qiao_3I
Fri Feb 24, 2017 12:23 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Activation energy and its reliance on temperature
Replies: 3
Views: 312

Re: Activation energy and its reliance on temperature

If Ea is low, then the slope of the line made by the Arrhenius equation is also low, and closer to zero, leading to less variance with respect to temperature. Basically, if Ea is less, the plot of lnk versus temperature becomes more and more of a straight horizontal line.
by edward_qiao_3I
Fri Feb 24, 2017 12:22 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Slow Reaction
Replies: 11
Views: 621

Re: Slow Reaction

Usually, if I'm not mistaken, this will be given to you
by edward_qiao_3I
Fri Feb 24, 2017 12:21 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: Homework 15.19 c & d
Replies: 3
Views: 320

Re: Homework 15.19 c & d

Did you include the rate constant k in that equation?
by edward_qiao_3I
Fri Feb 24, 2017 12:20 am
Forum: General Rate Laws
Topic: Molecularity and Overall Rate Law Relationship [ENDORSED]
Replies: 2
Views: 386

Re: Molecularity and Overall Rate Law Relationship [ENDORSED]

The molecularity by itself does not determine the rate - what determines the rate is whether the step is a slow or fast step. The rate of the slow step = the rate of the overall rxn, since the fast steps will be forced to wait for the slow step to complete - think of the ferry analogy
by edward_qiao_3I
Fri Feb 24, 2017 12:19 am
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Activation Energy
Replies: 4
Views: 410

Re: Activation Energy

Yes. Essentially, because the activation energy is low already, not that much extra kinetic energy is needed to start the reaction, so increasing temperature (and therefore kinetic energy) does not do that much for the reaction
by edward_qiao_3I
Sat Feb 11, 2017 4:53 pm
Forum: Calculating Work of Expansion
Topic: Which process does more work?
Replies: 3
Views: 377

Re: Which process does more work?

So when a question is asking you to consider the difference between reversible or irreversible processes, how can you tell the difference?
by edward_qiao_3I
Thu Feb 02, 2017 11:47 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Entropy Integral
Replies: 1
Views: 251

Re: Entropy Integral

The integral of ds=nCv dT/T equates to Delta S= nCv ln (T1/T2) which gives you your equation for Entropy with temperature change
by edward_qiao_3I
Thu Feb 02, 2017 5:10 pm
Forum: Balancing Redox Reactions
Topic: reduction vs. oxidation
Replies: 3
Views: 312

Re: reduction vs. oxidation

Generally you can tell the oxidation number of an element by its group. Ones toward the right side, the non-metals, will generally have negative oxidation numbers. Ones on the left, the alkali metals, will generally have positive oxidation numbers. The ones that tend to change around are the metals ...
by edward_qiao_3I
Thu Jan 26, 2017 2:17 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Question 8.87
Replies: 1
Views: 227

Re: Question 8.87

So you'll need the specific heat for ice, and use it to calculate the amount of energy needed to raise the temperature of ice to 0 degrees Celsius. Then, the ice undergoes phase change, so you'll need to add the energy needed for that. Repeat the process for water and add all of it together to get y...
by edward_qiao_3I
Thu Jan 26, 2017 2:13 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Example of isolated System
Replies: 4
Views: 1116

Re: Example of isolated System

A bomb calorimeter is also particularly useful since it ensures that there is no volume change within the system and thus can most accurately measure the energy given by a reaction.
by edward_qiao_3I
Fri Jan 20, 2017 2:25 am
Forum: Phase Changes & Related Calculations
Topic: Derivations
Replies: 21
Views: 2006

Derivations

Will there be any questions on quizzes or midterms asking us to complete derivations of equations we learn in class?
by edward_qiao_3I
Mon Jan 09, 2017 2:34 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7337
Views: 788728

Re: Post All Chemistry Jokes Here

People who study organic chemistry can really get into alkynes of trouble
by edward_qiao_3I
Sat Dec 03, 2016 7:41 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Acid/Base Problem Estimation Method
Replies: 1
Views: 303

Re: Acid/Base Problem Estimation Method

If it's going to be anything like the 2015 final, yes, but you will be required to include a justification for why you are allowed to do so.
by edward_qiao_3I
Mon Nov 28, 2016 10:10 am
Forum: Polyprotic Acids & Bases
Topic: Polyprotic Acids and strength
Replies: 2
Views: 561

Re: Polyprotic Acids and strength

I don't think it's safe to assume that all polyprotic acids are weak, but most are because it's difficult to lose the second Hydrogen.
by edward_qiao_3I
Mon Nov 28, 2016 10:04 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: When Should I use the ICE table?
Replies: 6
Views: 10792

Re: When Should I use the ICE table?

You should be using ICE when you're trying to track change in a reaction over time, esp from initial concentrations to equilibrium.
by edward_qiao_3I
Mon Nov 28, 2016 10:00 am
Forum: Properties & Structures of Inorganic & Organic Bases
Topic: Weak Bases
Replies: 4
Views: 665

Re: Weak Bases

Additionally, weak bases are weak bases because they are more stable and are less likely to take another H to form the conjugate acid, and therefore will result in less production of OH- when combined in an aqueous solution.
by edward_qiao_3I
Mon Nov 14, 2016 3:11 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Difference between Pressure and compression/expansion?
Replies: 5
Views: 1896

Re: Difference between Pressure and compression/expansion?

Compression/expansion is just a description of change in volume, which in turn has an impact on pressure given by P=nRT/V, where pressure and volume have an inverse relationship. Most of these problems also hold temperature constant, so you can just use P=n/V
by edward_qiao_3I
Wed Nov 09, 2016 1:24 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: [J] for solute in a dilute solution
Replies: 1
Views: 169

Re: [J] for solute in a dilute solution

the concentration of Zinc Chloride would go in the denominator, while the concentration of Zinc ion and Chloride ion would go in the numerator. EDIT: sorry, since Zinc Chloride actually appears as a solid, it is not included in the calculation of the equilibrium constant. Your end equation for chemi...
by edward_qiao_3I
Thu Oct 27, 2016 9:20 pm
Forum: Hybridization
Topic: sigma and pi bonds
Replies: 3
Views: 387

Re: sigma and pi bonds

A sigma bond is just a bond is just the first bond formed between two atoms. Any additional (double, triple, etc.) are considered pi bonds
by edward_qiao_3I
Thu Oct 27, 2016 9:15 pm
Forum: Hybridization
Topic: Defining Sigma and Pi Bonds [ENDORSED]
Replies: 1
Views: 229

Re: Defining Sigma and Pi Bonds [ENDORSED]

To sort of visualize them, Sigma bonds are basically a direct connection straight from one atom to another, whereas pi bonds form over and around those sigma bonds, if that makes any sense. This is why molecules with pi bonds cannot rotate.
by edward_qiao_3I
Wed Oct 19, 2016 12:35 pm
Forum: Ionic & Covalent Bonds
Topic: Electronegativity and Bond Types
Replies: 2
Views: 347

Re: Electronegativity and Bond Types

For a couple it is straight memorization, but for others it should be fairly evident. For example, for any bond between a halide and a group I or II metal, it should be fairly apparent that this bond will be primarily ionic in character. On the other hand, for bonds between nonmetals, such as betwee...
by edward_qiao_3I
Wed Oct 12, 2016 10:24 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Negative frequency of light?
Replies: 1
Views: 202

Negative frequency of light?

when calculating the change in energy levels, say from n=4 to n=3, plugging this into \Delta E= E_{f} - E_{i} using E_{n}= -(hR)/n^2 gives a negative value for \Delta E . If you try to find frequency from this using E=h\nu , it will be negative, which isn't possible, since you can't have neg...
by edward_qiao_3I
Fri Oct 07, 2016 10:17 am
Forum: Properties of Light
Topic: Work Functions [ENDORSED]
Replies: 1
Views: 207

Work Functions [ENDORSED]

Will we have to know the work functions of different metals for the quiz? Or is that something that will be given with the questions?

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