Search found 27 matches

by EPerez1B
Fri Mar 11, 2016 3:48 pm
Forum: *Organic Reaction Mechanisms in General
Topic: Arrow Pushing Type Questions
Replies: 1
Views: 434

Re: Arrow Pushing Type Questions

You can tell the difference between an addition and substitution by looking at your product. If you started with two reactants and end up with one, it's an electrophilic addition. If you begin with two reactants and end up with two products, it's substitution. Here, one atom is being replaced by ano...
by EPerez1B
Mon Feb 29, 2016 5:21 pm
Forum: *Constitutional and Geometric Isomers (cis, Z and trans, E)
Topic: Constitutional vs. Geometrical Isomers
Replies: 2
Views: 403

Re: Constitutional vs. Geometrical Isomers

Constitutional isomers have the same molecular formulas with different structures (connectivity). Basically, they will differ in the way the carbons are connected. Geometric isomers have the same connectivity with different geometrics (different arrangements in space).
by EPerez1B
Tue Feb 23, 2016 11:23 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Slow reaction vs fast reaction
Replies: 2
Views: 2347

Re: Slow reaction vs fast reaction

I think you can figure it out if you are given reactions that are at equilibrium. If it's at equilibrium, assume it's a fast step. Otherwise, the question will say if it's a fast or slow step.
by EPerez1B
Tue Feb 23, 2016 11:20 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Difference Between K and k
Replies: 2
Views: 13838

Re: Difference Between K and k

Yeah, just think of K as the equilibrium constant (K=k/k') and k as the rate constant.
by EPerez1B
Wed Feb 17, 2016 3:34 pm
Forum: General Rate Laws
Topic: Helpful Video/clarifications on rate laws
Replies: 1
Views: 346

Re: Helpful Video/clarifications on rate laws

Thank you so much, this actually helps a lot!
by EPerez1B
Wed Feb 17, 2016 3:29 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: activation energy: endothermic or exothermic
Replies: 1
Views: 329

Re: activation energy: endothermic or exothermic

This can probably explain better than I can, hope this helps!
by EPerez1B
Wed Feb 17, 2016 2:52 pm
Forum: Zero Order Reactions
Topic: Units [ENDORSED]
Replies: 7
Views: 1121

Re: Units [ENDORSED]

Yes, other ways of writing the same units would be M (molarity)/s or Ms^-1 or mol(L^-1)(s^-1).
by EPerez1B
Sun Feb 07, 2016 8:53 pm
Forum: Phase Changes & Related Calculations
Topic: 2014 Midterm Question 5C
Replies: 2
Views: 471

Re: 2014 Midterm Question 5C

I believe this may be a mistake. E is used for internal energy, which is a state function because it can added or subtracted. I'm pretty sure work and heat are the only non-state functions.
by EPerez1B
Sun Feb 07, 2016 8:43 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 2007 MT Question 1
Replies: 1
Views: 293

Re: 2007 MT Question 1

I don't have the 2007 midterm, but I can walk you through how to get to the equation they are asking for. You start off with the first two equations. Multiply the second equation by two so you get 2B-->2C+2D. The 2Bs cancel out and you're left with A-->2C+2D. Next, you flip the second equation so in...
by EPerez1B
Sun Jan 24, 2016 8:38 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: QUIZ 1 Material
Replies: 7
Views: 993

Re: QUIZ 1 Material

Most TAs should accept that. I haven't heard of TAs who don't accept hand written responses.
by EPerez1B
Sun Jan 17, 2016 6:51 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hess's Law
Replies: 3
Views: 543

Re: Hess's Law

H, N, O, F, Cl, Br, and I will all have an enthalpy of 0. Diatomic forms have enthalpy of 0 because they exist naturally in nature so it doesn't take extra energy to make them.
by EPerez1B
Sun Jan 17, 2016 6:46 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: QUIZ 1 Material
Replies: 7
Views: 993

Re: QUIZ 1 Material

You hand in the self prep quizzes in discussion right before you take your quiz.
by EPerez1B
Sat Jan 09, 2016 4:16 pm
Forum: Phase Changes & Related Calculations
Topic: Systems
Replies: 2
Views: 475

Systems

If a question asks to determine whether the system is open, closed, or isolated, how do you know what part of the question is the system? For example, part a of a question asks what type of system coffee in a high-quality thermos is and part c asks what type of system a bomb calorimeter in which ben...
by EPerez1B
Wed Nov 25, 2015 1:55 am
Forum: Hybridization
Topic: How do you find hybridization?
Replies: 3
Views: 790

Re: How do you find hybridization?

Another easy way to find the hybridization is to use the AXE method. The X denotes the bonding pairs and the E denotes the lone pairs. Add the number of bonding pairs to the number of lone pairs to get the number of regions of high electron density. You use this to figure out your hybridization. For...
by EPerez1B
Wed Nov 25, 2015 1:32 am
Forum: Balancing Chemical Reactions
Topic: Balancing Equations
Replies: 2
Views: 483

Re: Balancing Equations

What helps me and others I know is making a table and writing how many atoms of each type I have down for both sides of the table. If they match up, you have the correct balanced equation, if not, you should go back and check your equation to see where you miscounted.
by EPerez1B
Wed Nov 25, 2015 12:51 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Determining Bond Angle for Various Molecular Shapes
Replies: 2
Views: 2164

Re: Determining Bond Angle for Various Molecular Shapes

I agree with the post above. However, lone pairs don't always cause the bond angles to change. If the lone pairs are evenly spaced out, they will "cancel" each other so the molecular shape will have the angle you expect. For example, AX3E2 will have an angle less than the expected angle, b...
by EPerez1B
Wed Nov 25, 2015 12:14 am
Forum: Biological Examples
Topic: Summary of Biological Importance
Replies: 2
Views: 485

Re: Summary of Biological Importance

Coordination compounds that are critical for enzyme function include manganese, nickel, copper, and zinc.
by EPerez1B
Wed Nov 25, 2015 12:01 am
Forum: Naming
Topic: using bis, tris, tetrakis
Replies: 4
Views: 4862

Re: using bis, tris, tetrakis

When naming coordination compounds, prefixes mono-. di-, tri-, tetra-, penta-, and hexa- are used to indicate the number of ligands present. If a ligand already has a prefix or is polydentate, the prefixes bis-, tris-, or tetrakis- are used.
by EPerez1B
Tue Nov 24, 2015 11:34 pm
Forum: Dipole Moments
Topic: Dipole Moments and Polarity
Replies: 2
Views: 718

Re: Dipole Moments and Polarity

To determine polarity, first you should draw the Lewis structure of the compound. Then, you should determine its shape. If the shape is bent or trigonal pyramidal, the compound will be polar. If the shape is linear, trigonal planar, or tetrahedral, it can be polar or nonpolar (assuming there are no ...
by EPerez1B
Tue Nov 24, 2015 11:00 pm
Forum: Empirical & Molecular Formulas
Topic: VIDEO: Empirical and Molecular Formulas
Replies: 2
Views: 567

Re: VIDEO: Empirical and Molecular Formulas

Please note we made a mistake for the final answer of the empirical formula for example 2. It should say not
by EPerez1B
Tue Nov 24, 2015 10:54 pm
Forum: Empirical & Molecular Formulas
Topic: VIDEO: Empirical and Molecular Formulas
Replies: 2
Views: 567

VIDEO: Empirical and Molecular Formulas

In this video, we go over how to determine empirical and molecular formulas.

Contributors Erin Min and Emilyann Perez

Discussion 1F
by EPerez1B
Tue Nov 24, 2015 9:11 pm
Forum: Empirical & Molecular Formulas
Topic: Which methods to use when finding empirical formulas
Replies: 2
Views: 665

Re: Which methods to use when finding empirical formulas

The second method you described is supposed to be more straightforward, so I think it's preferred; however, I don't think it matters which method you use so long as you arrive at the correct answer.
by EPerez1B
Tue Nov 24, 2015 8:37 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal charge and resonance structures
Replies: 2
Views: 559

Re: Formal charge and resonance structures

You don't have to find the formal charge unless the question specifically asks you to do so. Otherwise, any Lewis structure drawn should be acceptable.
by EPerez1B
Tue Nov 24, 2015 8:31 pm
Forum: Administrative Questions and Class Announcements
Topic: Videos Submissions
Replies: 8
Views: 11639

Re: Videos Submissions

How do we convert the file from .mp4 to anything else? My partner has a mac and I have a pc and we're not sure how to convert the video we created.
by EPerez1B
Tue Nov 24, 2015 8:23 pm
Forum: Lewis Structures
Topic: calculated number of valence e- does not match
Replies: 2
Views: 429

Re: calculated number of valence e- does not match

Lone pairs and hydrogen atoms bonded to carbon atoms are typically not shown in questions similar to these, so you have to remember to take into account those electrons.
by EPerez1B
Tue Nov 24, 2015 8:04 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: MO Diagram Rules
Replies: 2
Views: 451

Re: MO Diagram Rules

As a side note, if you're doing the MO diagram for a molecule with one atom that is Z>8, and one atom that is Z<8, use the MO diagram for Z>8.

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