Search found 21 matches

by Kevin_Li_2F
Fri Mar 17, 2017 4:42 pm
Forum: *Cycloalkanes
Topic: 2015 Practice Final 9A
Replies: 1
Views: 560

Re: 2015 Practice Final 9A

In this case I think the cycloheptane is treated as a substituent while the propane is treated as the main carbon chain because propane contains the functional OH group, and the main/longest carbon chain must always contain the functional group. This explains the anomalous naming.
by Kevin_Li_2F
Tue Feb 28, 2017 8:12 pm
Forum: *Alkanes
Topic: Multiple Line Structures
Replies: 1
Views: 195

Multiple Line Structures

When drawing line structures, what makes one line structure more valid/correct than another? For example... https://snag.gy/ZQDNoi.jpg All represent 3,3-dimethylpentane, yet each differ slightly by bond angle or whether a line turns up or down. Is there a standardized correct method for these line s...
by Kevin_Li_2F
Tue Feb 28, 2017 1:22 am
Forum: *Alkanes
Topic: prop-1-enyl vs prop-1-ene
Replies: 1
Views: 220

prop-1-enyl vs prop-1-ene

I've seen both used in the textbook. Is prop-1-enyl simply a way of writing prop-1-ene when a substituent of Benzene? They both seem to refer to a propyl with a double bond on the 1 to 2 carbon.
by Kevin_Li_2F
Mon Feb 13, 2017 3:19 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Sig Figs for K Calculations from Gibbs Free Energy
Replies: 1
Views: 224

Re: Sig Figs for K Calculations from Gibbs Free Energy

I understand that the least number of given sig figs is the number of sig figs you use, but does that mean in this case we just ignore all log rules we learned for pH? And which case there's still the question of if we use the rounded value of G or the unrounded value for additional precision (the a...
by Kevin_Li_2F
Mon Feb 13, 2017 3:15 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Sig Figs for K Calculations from Gibbs Free Energy
Replies: 1
Views: 224

Sig Figs for K Calculations from Gibbs Free Energy

For example (#6 in Midterm 2015) we must calculate E^{\circ} , \Delta G ^{\circ} , K . With a calculated E^{\circ} = 0.82V , we get that \Delta G ^{\circ} = -nFE^{\circ} = -1.582... \times 10^5 \approx -1.6 \times 10^5 J . When we proceed to calculate K from \Delta G^{\circ} = -RTlnK , do we use the...
by Kevin_Li_2F
Thu Feb 02, 2017 7:12 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: How to keep track of significant figures?
Replies: 2
Views: 385

How to keep track of significant figures?

For example in HW Question 14.39 using the Nernst equation to solve for the concentration of a compound in a battery, how many significant figures does the final answer have? You have to keep track of the ln rules, and then there's the fact that you're subtracting one term from another, so you have ...
by Kevin_Li_2F
Wed Feb 01, 2017 12:54 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: HOMEWORK 9.35
Replies: 2
Views: 301

Re: HOMEWORK 9.35

A single atom can move only translationally in 3 axises, so 3\times \frac{1}{2}RT = \frac{3}{2}RT . A nonlinear molecule can move translationally, but also rotate along 3 axises, so \frac{3}{2}RT + 3(\frac{1}{2}RT) = \frac{6}{2}RT = 3RT . A linear molecule would be similar but it can only ro...
by Kevin_Li_2F
Tue Jan 24, 2017 5:50 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: Significant figures for Boltzmann Equation
Replies: 1
Views: 217

Significant figures for Boltzmann Equation

I know that for logs, the rule is the log(X) where X has n significant figures means the answer must go out to n decimal places. However, this property only made sense in the context of 10^x, where the base = 10. What is the rule for ln, where the base is ~2.72, is it the same as logs?
by Kevin_Li_2F
Tue Jan 24, 2017 5:39 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: What is "standard" [ENDORSED]
Replies: 1
Views: 213

What is "standard" [ENDORSED]

What is the exact definition of Standard Enthalpy, entropy, and gibbs free energy? Is it at a defined temperature and pressure? What is a "pure state" for gibbs free energy standard.
by Kevin_Li_2F
Tue Jan 17, 2017 1:31 pm
Forum: Phase Changes & Related Calculations
Topic: How can internal energy be zero when isothermal reversible expansion?
Replies: 1
Views: 288

How can internal energy be zero when isothermal reversible expansion?

Why is when a gas expands reversibly and isothermally? Because and w < 0 (work being done on surroundings), where does the +q come from to counteract internal energy leaving as work?
by Kevin_Li_2F
Wed Jan 11, 2017 8:52 pm
Forum: Phase Changes & Related Calculations
Topic: Reversible Isothermal Reactions
Replies: 1
Views: 302

Reversible Isothermal Reactions

Why does a reversible reaction need to be isothermal for us to calculate the work done? How does work relate to temperature?

Why does U = 0 when isothermal compression/expansion of gas?
by Kevin_Li_2F
Sun Dec 04, 2016 7:35 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7569
Views: 1011410

Re: Post All Chemistry Jokes Here

Image
by Kevin_Li_2F
Mon Nov 14, 2016 6:57 pm
Forum: Naming
Topic: Rules for Writing Formula [ENDORSED]
Replies: 1
Views: 320

Rules for Writing Formula [ENDORSED]

What are the rules for writing the formula of coordination compounds? Is it alphabetical like writing the name? And if so, is it alphabetical by the symbol (Na = N) or the actual name (Sodium = S). I've also heard that neutral ligands are written before charged ones, is this true? Does charge affect...
by Kevin_Li_2F
Sat Nov 05, 2016 4:32 pm
Forum: Naming
Topic: HW 17.31 About alphabetic sequence in writing symbols and naming them
Replies: 1
Views: 213

Re: HW 17.31 About alphabetic sequence in writing symbols and naming them

1) I think writing it as (OH2) is safer because that's how the book does it.
2) In naming you write the neutral ligands first (so OH2 first because it's neutral). Otherwise it's alphabetical, and if 2 ligands contain the same element the ligand with fewer elements comes first.
by Kevin_Li_2F
Thu Nov 03, 2016 11:29 am
Forum: Lewis Structures
Topic: Best Method for Drawing Lewis Structures
Replies: 1
Views: 296

Best Method for Drawing Lewis Structures

My TA has a great way of doing Lewis Structures, evaluating the valence electrons of each atom one by one instead of totaling up the electrons as a whole and arbitrarily filling octets. I feel like this way better shows how the actual bonds form; for example in CO2 in doing it this way you see each ...
by Kevin_Li_2F
Tue Oct 25, 2016 8:29 pm
Forum: Lewis Structures
Topic: N2O Lewis Structure; how can N form a double bond?
Replies: 1
Views: 2714

N2O Lewis Structure; how can N form a double bond?

https://upload.wikimedia.org/wikipedia/commons/3/33/Muatan_masing-masing_atom_pada_N2O.jpg In structure 2, how can the N form a double bond (2 electrons contributed) and have 2 lone pair of elections (4 electrons). 2e- + 4e- = 6e-, but nitrogen only has 5 valence electrons. How come?
by Kevin_Li_2F
Mon Oct 17, 2016 1:59 pm
Forum: Lewis Structures
Topic: Best Way to Determine Central Atom [ENDORSED]
Replies: 1
Views: 587

Best Way to Determine Central Atom [ENDORSED]

The textbook says least electronegative while Doctor Lavelle says lowest ionization energy or electron affinity.

What is the difference between electron affinity and electronegativity? Which way is most reliable to determine central atom?
by Kevin_Li_2F
Mon Oct 10, 2016 1:05 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Aufbau Principal Exceptions
Replies: 1
Views: 314

Aufbau Principal Exceptions

Can someone explain why Ag's electron configuration is abnormal? What other exceptions should we know?
by Kevin_Li_2F
Mon Oct 10, 2016 1:03 pm
Forum: Trends in The Periodic Table
Topic: Electron Affinity
Replies: 3
Views: 589

Electron Affinity

The textbook says electron affinity increases to the right. But what about up and down? Whats the explanation for the trend?
by Kevin_Li_2F
Mon Oct 10, 2016 1:01 pm
Forum: *Shrodinger Equation
Topic: Shrodinger Equation
Replies: 4
Views: 539

Shrodinger Equation

So I know that we dont actually have to know how to do calculations with the equation. So what DO we need to know about the equation conceptually?
by Kevin_Li_2F
Fri Sep 30, 2016 12:58 am
Forum: Properties of Light
Topic: Mass of Atoms to Energy
Replies: 1
Views: 632

Re: Mass of Atoms to Energy

You have to use DeBroglie's equation, pictured below.

Image

From there you can find the frequency from the wavelength and the energy from E = hv, or alternatively e = hc/λ.

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