Search found 34 matches

by AuraCruzHeredia_1L
Tue Mar 08, 2016 3:01 pm
Forum: *Alkanes
Topic: naming using halogens
Replies: 1
Views: 296

Re: naming using halogens

If the halogen is the substituent then we use 1. alphabetical order 2. change the suffix to -o (Bromo, Chloro, Iodo,Fluoro...) If the halogen is a substituent of a substituent then you use the same method for naming parent chains and put it all in parentheses. So a propyl group with a bromide attach...
by AuraCruzHeredia_1L
Mon Mar 07, 2016 8:47 pm
Forum: *Cyclohexanes (Chair, Boat, Geometric Isomers)
Topic: Axial/Equitorial Cyclohexane
Replies: 1
Views: 270

Re: Axial/Equitorial Cyclohexane

I believe good way to identify it is

Axial: simply up/down. not at an angle. More like a 180º vertical line.

Equatorial: at an angle (i'd say 60ºish?)
by AuraCruzHeredia_1L
Mon Mar 07, 2016 8:35 pm
Forum: *Alkanes and Substituted Alkanes (Staggered, Eclipsed, Gauche, Anti, Newman Projections)
Topic: Different Strains
Replies: 3
Views: 524

Re: Different Strains

Torsional Strain: When rotating a molecule around a bond, the torsional strain is the repulsion caused by the electrons in between different groups when they pass by each other. (rotational) --> Basically, C-C bonds can rotate so the placements of the substituents relative to each other influence th...
by AuraCruzHeredia_1L
Mon Feb 29, 2016 11:17 pm
Forum: *Alkanes
Topic: Condensed Structural Formula v. Substituents
Replies: 1
Views: 353

Re: Condensed Structural Formula v. Substituents

I think it's a matter of recognition. But, the long way, would be to draw out a lewis structure of the formula. Sometimes it's good to keep track of some general commonalities like for example: CH3 tends to be at the end of a chain a lot of times, which makes sense, since our carbons have to have 4 ...
by AuraCruzHeredia_1L
Mon Feb 29, 2016 11:10 pm
Forum: *Alkanes
Topic: Tert and Neo
Replies: 1
Views: 237

Re: Tert and Neo

Check out: https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=83&t=1419"onclick="window.open(this.href);return false; A neo group is a group that has three methyl groups at the end and AT LEAST five carbons total, ie there is a secondary carbon connecting the branching side chain to the main ch...
by AuraCruzHeredia_1L
Mon Feb 29, 2016 4:35 pm
Forum: *Alkanes
Topic: Using Iso and Neo
Replies: 1
Views: 280

Re: Using Iso and Neo

Here's a chart putting it all together. Let me know if it still isn't clear to identify/you have more concept-based questions!
by AuraCruzHeredia_1L
Mon Feb 29, 2016 4:33 pm
Forum: *Alkanes
Topic: Common Name vs. IUPAC name
Replies: 1
Views: 321

Re: Common Name vs. IUPAC name

Yep! There's a post by Chem_Mod under info for Quiz 3. Unless specified, either works.
by AuraCruzHeredia_1L
Mon Feb 29, 2016 4:32 pm
Forum: *Alkanes
Topic: Order of Naming hydrocarbons
Replies: 1
Views: 213

Re: Order of Naming hydrocarbons

Nope! the di/tri/... prefixes are not relevant when looking at alphabetical order...

so something like dimethyl-ethyl is incorrect and ethyl-dimethyl is correct
by AuraCruzHeredia_1L
Sat Feb 27, 2016 2:51 pm
Forum: *Alkanes
Topic: Source of electrons
Replies: 2
Views: 235

Re: Source of electrons

Can you provide an example? I'm not quite sure what you're asking. I think maybe you're questioning if the e- source is say a double bond or a Cl with 3 lone pairs (maybe something like H2C=CHCl)? In this case, you'd just pay attention to electronegativities (how hard will it be to take away electro...
by AuraCruzHeredia_1L
Thu Feb 18, 2016 9:43 pm
Forum: Phase Changes & Related Calculations
Topic: Cv and Cp
Replies: 4
Views: 609

Re: Cv and Cp

If it's diatomic, we generally say it's linear (such as O=O or F-F) so using Cp = Cv + nR you can get Cv = 5/2R and Cp = 7/2R

Not sure if that's what youre asking?
by AuraCruzHeredia_1L
Wed Feb 17, 2016 1:05 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Equations for finding the Activation Energy
Replies: 1
Views: 284

Re: Equations for finding the Activation Energy

Answer: You can use either, since they're the same equation just one (the ln version) is linearized. I notice you made a mistake: the Arrhenius eq is Ae^(-Ea/(RT)) not A^(-Ea/(RT)) Explanation: So the Arrhenius Eq itself is (1) k = Ae^{\frac{-Ea}{RT}} where k is your rate constant, A is a constant ...
by AuraCruzHeredia_1L
Mon Feb 08, 2016 4:51 pm
Forum: Balancing Redox Reactions
Topic: Homework 14.5d
Replies: 1
Views: 338

Re: Homework 14.5d

P4 --> PH3

first balance the non-H and non-O species (ie. P_

P4 --> 4PH3

then balance the O's (none present) and H's (using H+)

12 H+ + P4 --> 4PH3

then balance the charge (using e-)

12e- + 12H+ + P4 --> 4PH3

(this is for acidic solutions)


Does this help?
by AuraCruzHeredia_1L
Mon Feb 08, 2016 4:47 pm
Forum: Phase Changes & Related Calculations
Topic: Cv and Cp
Replies: 4
Views: 609

Re: Cv and Cp

Usually you'll use Cv = 3/2 R and Cp = 5/2 (for atomic).

Using Cp = Cv + nR you can get the for linear molecules

Cv = 5/2R and Cp = 7/2R
by AuraCruzHeredia_1L
Mon Feb 01, 2016 10:22 am
Forum: Balancing Redox Reactions
Topic: Balancing with O2???
Replies: 1
Views: 237

Re: Balancing with O2???

It's pretty much impossible to get the half reactions without using O2 as a source of oxygen. Since we know OH goes to H2O then to balance the equation you'd have no option but to use O2. Say you had 2 mols of OH then you'd need 2O and 2 H and if you use H2O then you'd have 2H2O to get the 2O but yo...
by AuraCruzHeredia_1L
Thu Jan 28, 2016 1:19 am
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Stoichiometric coefficients in calculating entropy
Replies: 1
Views: 363

Re: Stoichiometric coefficients in calculating entropy

I think this is a mistake... since the mols would obviously cancel out. If you look at the worked-out examples in the reading itself, you'll notice the mols are not present in the final units. So it should just be J/Kmol.
by AuraCruzHeredia_1L
Tue Jan 26, 2016 8:42 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Delta S equations
Replies: 2
Views: 757

Re: Delta S equations

The assumption of each is that there's some change from one state to another. So T2/T1 implies some ∆T = T2 - T1 T IS NOT CONSTANT V2/V1 implies some ∆V = V2 - V1 V IS NOT CONSTANT P2/P1 implies some ∆P = P2 - P1 P IS NOT CONSTANT so logically, we would use the one that has a changing value. Sound g...
by AuraCruzHeredia_1L
Tue Jan 26, 2016 8:34 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Using Bond Enthalpies
Replies: 4
Views: 419

Re: Using Bond Enthalpies

You're given: C_{4}H_{10} + O_{2} --> CO_{2} + H_{2}O I. Balance the equation C_{4}H_{10} + \frac{13}{2}O_{2} --> 4CO_{2} + 5H_{2}O II. Figure out the bonds present per molecule (Lewis Structures) C 4 H 10 3 C-C bonds 10 C-H bonds O 2 1 O=O bond CO 2 1 O=C=O bond H 2 O 2 O-H bonds III. Using your ba...
by AuraCruzHeredia_1L
Tue Jan 26, 2016 8:13 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Adding equations to get a final equation (deltaH)
Replies: 2
Views: 344

Re: Adding equations to get a final equation (deltaH)

Hey, so let's just see what we would get if we did indeed use the answer: 1/2 ∆H1 - ∆H2 - 1/2 ∆H3 1) 1/2 (2A+B-->3C+E) 2) - (2B-->A+D+E) 3) -1/2 (E-->3B+C) would go to A + \frac{1}{2}B --> \frac{3}{2}C + \frac{1}{2}E A + D + E--> 2B \frac{3}{2}B + \frac{1}{2}C -->\frac{1}{2}E then you look to cancel...
by AuraCruzHeredia_1L
Tue Jan 26, 2016 6:03 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Enthalpy/ Quiz 1
Replies: 2
Views: 467

Re: Enthalpy/ Quiz 1

You should likely know how to solve this kind of problem or, at least, know what it's asking. Cp = \frac{dH}{dT} = \frac{∆U+nRT}{dT}=\frac{dU}{dT}+nR = Cv + nR Thus, the relationship between the two molar heat capacities (Cp = constant p and Cv constant v) can be found by dividing the relationship a...
by AuraCruzHeredia_1L
Tue Jan 26, 2016 5:49 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Using Bond Enthalpies
Replies: 4
Views: 419

Re: Using Bond Enthalpies

When atoms get together and form bonds they're doing it so that they can be more stable. Stability implies lower energy. Thus, it would go from a higher energy to a lower energy, signifying that it has to lose (release) energy. For example, imagine there's an F- ion (which we know is the most electr...
by AuraCruzHeredia_1L
Sun Jan 24, 2016 10:45 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Spontaneous reactions
Replies: 1
Views: 282

Re: Spontaneous reactions

If T is constant then, for a reversible reaction, we can use the equations

∆S = q/T

and

q = ∆H

to get ∆S = ∆H/T

you can calculate ∆H using bond enthalpies (bonds broken - bonds formed).
by AuraCruzHeredia_1L
Sat Jan 23, 2016 9:11 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Q.3 Quiz 1 Prep W2014
Replies: 1
Views: 257

Re: Q.3 Quiz 1 Prep W2014

The overarching point of these problems is that Enthalpy (∆H) is a state function. In other words, ∆H can be found by adding the ∆H's of individual steps in a reaction. *State = Additive* So you're given the steps as follows: Step 1. 2A+B --> 3C+E (with ∆H 1 ) Step 2. 2B --> A+D+E (with ∆H 2 ) Step ...
by AuraCruzHeredia_1L
Wed Jan 20, 2016 5:45 pm
Forum: Phase Changes & Related Calculations
Topic: Work During a Phase Change
Replies: 2
Views: 247

Re: Work During a Phase Change

Hey, so for an isothermal system (a system at constant T) you'll find that ∆U = 0 (internal energy = 0). Using ∆U = q + w if ∆U = 0 then we can say 0 = q + w ----> -w = q Negative work (-w) = work done by the system the small change in volume (^) corresponds to a change in displacement because: w = ...
by AuraCruzHeredia_1L
Mon Jan 11, 2016 4:18 pm
Forum: *Aldehydes
Topic: Jokes...
Replies: 1
Views: 2416

Jokes...

Image


I might be a lil' ahead of the game.
by AuraCruzHeredia_1L
Mon Jan 11, 2016 4:16 pm
Forum: Phase Changes & Related Calculations
Topic: Hess's Law
Replies: 3
Views: 442

Re: Hess's Law

Essentially, every chemical reaction can be written in terms of steps... This basically means that your reaction (ie. A + C --> E) with (∆H3) is composed by A + B -> D (this has ∆H1) PLUS (add) D + C -> E + B (∆H2) if you just add things like you would normally, you'll see that the D's and B's cance...
by AuraCruzHeredia_1L
Thu Oct 29, 2015 7:04 pm
Forum: Lewis Structures
Topic: O3 Lewis Structure
Replies: 5
Views: 3727

Re: O3 Lewis Structure

The way I was thinking of drawing it was like this though: :Ö=Ö=Ö: I don't know if this is still relevant but essentially your drawing (as the people above have noted) has 10 e-s around the central O atom (so it's an overfilled octet, which Oxygen cannot have based on it's electron configuration). ...
by AuraCruzHeredia_1L
Thu Oct 29, 2015 6:58 pm
Forum: Hybridization
Topic: Video: Finding Hybridization
Replies: 3
Views: 553

Re: Video: Finding Hybridization

Here's a followup on what that would look like in terms of bonding and orbitals!
by AuraCruzHeredia_1L
Wed Oct 28, 2015 8:56 pm
Forum: Hybridization
Topic: Video: Finding Hybridization
Replies: 3
Views: 553

Video: Finding Hybridization

This is a video showing you where the "answers" come from, but they don't explain what they mean so make sure that you understand that cause otherwise this wont help at all theoretically.
by AuraCruzHeredia_1L
Tue Oct 27, 2015 5:42 pm
Forum: Ionic & Covalent Bonds
Topic: Oxidation state
Replies: 1
Views: 325

Re: Oxidation state

I'm almost certain that it all depends on the bonds that it's forming. The more electronegative, the more likely it is to have a negative charge. Oxidation depends on valence electrons. So, for example, Fluorine (F) has a -1 charge because it's missing 1 electron to fill it's octet. Hydrogen always ...
by AuraCruzHeredia_1L
Tue Oct 27, 2015 4:32 pm
Forum: Lewis Structures
Topic: Drawing Lewis Structures
Replies: 1
Views: 193

Re: Drawing Lewis Structures

Probably just in 2D as long as you recognize the actual shape that they're forming (based on their generic formulas)
by AuraCruzHeredia_1L
Tue Oct 27, 2015 4:30 pm
Forum: Lewis Structures
Topic: O3 Lewis Structure
Replies: 5
Views: 3727

Re: O3 Lewis Structure

O3 has 18 valence electrons (3 * 6e- = 18e-).

Because of this, you can't have 2 pairs of double bonds, since it'd give you the incorrect number of electrons.


:Ö=O=Ö:

only has 16e- but the octets are already filled, so we have to use one sight with only one bond and another with 2 bonds.
by AuraCruzHeredia_1L
Mon Oct 26, 2015 11:13 pm
Forum: Hybridization
Topic: Quiz 2 Preparation
Replies: 3
Views: 809

Re: Quiz 2 Preparation

In case it's hard to conceptualize based on the terminology; just draw the Lewis Structure and then count regions of electron density around the CENTRAL atom (which is essentially anywhere there's a bond or lone pairs of electrons). Then, add up orbitals to equal that amount of regions. Example: SF ...
by AuraCruzHeredia_1L
Mon Oct 26, 2015 10:59 pm
Forum: Hybridization
Topic: Electronegativity and Bonding (3.87)
Replies: 1
Views: 328

Re: Electronegativity and Bonding (3.87)

The more electronegative a molecule, the stronger the bond. Although I'm not sure that this is an all-inclusive statement (since there's so many exceptions to pretty much everything) it's a pretty good guideline. Ionic compounds are thus generally stronger than covalent compounds (this can be seen b...
by AuraCruzHeredia_1L
Sun Oct 25, 2015 2:48 pm
Forum: Ionic & Covalent Bonds
Topic: Coordinate Covalent Bonds
Replies: 2
Views: 340

Re: Coordinate Covalent Bonds

Simply put, a coordinate covalent bond is a bond in which BOTH of the electrons that are being shared come from the SAME atom. This means that it's not one and one, but two from one. NH3 + HCl ---> NH4Cl is an example of this in which both electrons that are shared come from the NH3 (the H from HCl ...

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