## Search found 34 matches

Sat Mar 18, 2017 8:33 pm
Forum: *Cycloalkenes
Topic: Midterm 2013 6a
Replies: 3
Views: 896

### Re: Midterm 2013 6a

This is because the numbering must follow the direction of the double bond. Naming it as 2,3,4,4-tetramethylcyclo-1-hexene would make the number second double bonded carbon as 6, which would be incorrect since double bond carbon atoms are assigned the smallest possible locator numbers unless there i...
Sat Mar 18, 2017 7:42 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Nernst Equation with Log
Replies: 3
Views: 449

### Nernst Equation with Log

Page 52 of the course reader says that at 25 degrees celsius (2.303RT)/F = 0.0592 V
However, when I do the calculation, (2.303(8.314 j*k^-1*mol^-1)(298 K))/(96,4853 C*mol^-1), I get 0.0059 V.
Is there and issue with the calculation or units that is resulting in a different voltage?
Sat Mar 18, 2017 2:03 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 2014 Final 1C
Replies: 3
Views: 548

### Re: 2014 Final 1C

It is multiplied by 1/2 because the questions says that Ron "realizes that half of his 255 g forgetfulness potion has boiled away. Therefore, you would multiply the mass by 1/2 since only half of it was converted into vapor.
Mon Mar 13, 2017 1:31 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Winter 2015 Final Exam Question 5A
Replies: 1
Views: 284

### Winter 2015 Final Exam Question 5A

In a neuron (a nerve cell), the concentration of K ions inside the cell is about 20–30 times as great as that outside. What potential difference between the inside and the outside of the cell would you expect to measure if the difference is due only to the imbalance of potassium ions? The solution s...
Thu Mar 09, 2017 3:20 pm
Forum: *Organic Reaction Mechanisms in General
Topic: Half arrows
Replies: 4
Views: 642

### Re: Half arrows

The practice problems deal with pairs of electrons being transferred so that's why mostly full arrows are used. Each bond consists of two shared electrons. The chlorine is more electronegative than the carbon so you can think about it like the chlorine pulling the electrons towards itself from the b...
Mon Feb 27, 2017 9:58 pm
Forum: *Organic Reaction Mechanisms in General
Topic: 4.40 (c)
Replies: 1
Views: 295

### 4.40 (c)

I thought when ∆Gr°< 0, then the reaction is exergonic and favorable so K > 1 and when ∆Gr°> 0, the endergonic reaction is unfavorable so K < 1. So when part c asks which profiles would have K > 1, I thought they would be 1 and 2 since they both of their ∆Gr°are less than zero. However,the solution ...
Sat Feb 25, 2017 12:24 am
Forum: General Rate Laws
Topic: HW 15.105 [ENDORSED]
Replies: 1
Views: 297

### HW 15.105[ENDORSED]

To prepare a 15-kg dog for surgery, 150 mg of the anesthetic phenobarbitol is administered intravenously. The reaction in which the anesthetic is metabolized (decomposed in the body) is first order in phenobarbitol and has a half-life of 4.5 h. After about 2 h, the drug begins to lose its effect. Ho...
Sun Feb 19, 2017 6:58 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: 15.23 part C
Replies: 1
Views: 285

### 15.23 part C

Determine the rate constant for each of the following first-order reactions, in each case expressed for the rate of loss of A: (a) A --> B, given that the concentration of A decreases to one-half its initial value in 1000. s; (b) A --> B, given that the concentration of A decreases from 0.67 mol L^-...
Fri Feb 17, 2017 2:35 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8017
Views: 1401982

### Re: Post All Chemistry Jokes Here

Sun Feb 12, 2017 1:42 am
Forum: Administrative Questions and Class Announcements
Topic: W '17 midterm
Replies: 2
Views: 466

### Re: W '17 midterm

The midterm consists of material from the course reader to page 54, which covers thermodynamics and electrochemistry. Doing the homework problems and then doing the practice midterms would be good preparation for the midterm. Good luck!
Thu Feb 02, 2017 3:01 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Self-Test 9.15A
Replies: 1
Views: 304

### Re: Self-Test 9.15A

Yes, you are correct. The enthalpy of vaporization is positive because it represents the energy that must be added to the liquid substance to transform a quantity of that substance into gas.
Sun Jan 29, 2017 9:17 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 9.13 Changes in Entropy
Replies: 1
Views: 284

### Re: 9.13 Changes in Entropy

You should use C, it is a typo in the solutions manual.
https://lavelle.chem.ucla.edu/wp-conten ... rs_6Ed.pdf
Thu Jan 26, 2017 5:44 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: HW 8.67
Replies: 1
Views: 362

### HW 8.67

Use the information in Tables 8.3, 8.6, and 8.7 to estimate the enthalpy of formation of each of the following compounds in the liquid state. The standard enthalpy of sublimation of carbon is 717 kJ·mol 1. (a) H2O; (b) methanol, CH3OH; (c) benzene, C6H6 (without resonance); (d) benzene, C6H6 (with r...
Thu Jan 26, 2017 4:11 pm
Forum: Calculating Work of Expansion
Topic: Homework 8.9 [ENDORSED]
Replies: 3
Views: 589

### Re: Homework 8.9[ENDORSED]

The gas constant should be given in different units (J*K^-1*mol^-1, L*atm*K^-1*mol^-1, L*atm*K^-1*mol^-1, L*bar*K^-1*mol^-1, L*Torr*K^-1*mol^-1).
Sun Jan 22, 2017 4:58 pm
Forum: Student Social/Study Group
Topic: Chemistry Joke
Replies: 28
Views: 3699

### Re: Chemistry Joke

If you're not part of the solution, you're part of the precipitate
Thu Jan 12, 2017 2:15 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Help on HW 8.57
Replies: 4
Views: 789

### Re: Help on HW 8.57

The problem gives you the ΔHc for C2H2, C2H6, and H2. ΔHc is the enthalpy for the combustion of that compound. So you would get the three equations by writing the combustion equation for all three of the compounds and balancing them. For example, for C2H2, Combustion means that O2 is a reactant and ...
Sat Dec 03, 2016 5:15 pm
Forum: *Titrations & Titration Calculations
Topic: Fall 2014 Final Exam Q7
Replies: 1
Views: 601

### Fall 2014 Final Exam Q7

Which of the following indicators could you use for a titration of 0.20 M CH3COOH with 0.20 M NaOH. Explain your selection and justify your answer with detailed calculations. The solution for this question states that because the both acid and base have identical concentrations and at the stoichiome...
Wed Nov 30, 2016 3:02 pm
Forum: Polyprotic Acids & Bases
Topic: Strong Acids and Bases
Replies: 2
Views: 602

### Re: Strong Acids and Bases

If an acid is considered strong, that means it completely ionizes so we can say that the concentration of the acid equals the concentration of Hydronium ions. You would not be able to know if if the acid or base completely ionizes unless you know it is strong.
Wed Nov 16, 2016 5:48 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Effect of change in temperature
Replies: 1
Views: 353

### Effect of change in temperature

According to the course reader if a reaction requires heat (endothermic) while forming a product then heating will favor P formation. Does this mean that the equilibria will shift to the right because there would be more products at equilibrium or that the equilibria would shift to the left because ...
Wed Nov 16, 2016 5:38 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: oxalato
Replies: 1
Views: 346

### Re: oxalato

For our purposes, oxalato should have a charge of 2- as shown in the course reader.
Thu Nov 10, 2016 2:16 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Naming NH4[PtCl3(NH3)]
Replies: 2
Views: 3036

### Naming NH4[PtCl3(NH3)]

NH₄[PtCl₃(NH₃)]
The name of this ammoniumamminetrichloroplatinate (II)
I was wondering why the charge of Platinum would be II and why metal is written in terms of an anion as platinate instead of platinum.
Fri Nov 04, 2016 6:03 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Paramagnetic vs Diamagnetic
Replies: 2
Views: 364

### Re: Paramagnetic vs Diamagnetic

To find out if a material is paramagnetic or diamagnetic, you need to know whether it has unpaired electrons. So yes, you would have to use the molecular orbital energy diagram to find out whether it has unpaired electrons or not. If it does have unpaired electrons, then it is diamagnetic and if it ...
Thu Oct 27, 2016 3:30 pm
Forum: Lewis Structures
Topic: Formal Charge vs Octet Rule
Replies: 3
Views: 1269

### Formal Charge vs Octet Rule

I was wondering which rule takes precedence over the other in some cases. For example, If we were following the octet tule PO4^3- will have lone pairs around each oxygen atom with all single bonds between the oxygen atoms and phosphorus. But according to the formal charges, the more stable lewis str...
Mon Oct 24, 2016 1:11 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration for Niobium
Replies: 1
Views: 597

### Electron Configuration for Niobium

The electron configuration for Niobium is [Kr] 4d^4 5s^1. I was wondering why this is an exception and not [Kr] 4d^3 5s^2.
Thu Oct 20, 2016 2:55 pm
Forum: Lewis Structures
Topic: Noble Gas Valence Electrons [ENDORSED]
Replies: 1
Views: 248

### Re: Noble Gas Valence Electrons[ENDORSED]

They do have 8 valence electrons. However, they are not as reactive as other atoms because they already have an octet.
Wed Oct 12, 2016 9:40 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8017
Views: 1401982

### Re: Post All Chemistry Jokes Here

If H2O is water, and H2O2 is hydrogen peroxide, then what is H2O4?

Drinking.
Sun Oct 09, 2016 11:40 pm
Forum: Einstein Equation
Topic: Sif Figs for #4 Fall 2015 Quiz 1 Preparation [ENDORSED]
Replies: 2
Views: 532

### Re: Sif Figs for #4 Fall 2015 Quiz 1 Preparation[ENDORSED]

Thanks!
Sun Oct 09, 2016 6:23 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Concept Question [ENDORSED]
Replies: 1
Views: 308

### Re: Concept Question[ENDORSED]

The change in energy would be negative because the electron is losing energy when it goes from a higher shell to a lower shell.
Sun Oct 09, 2016 6:21 pm
Forum: Einstein Equation
Topic: Sif Figs for #4 Fall 2015 Quiz 1 Preparation [ENDORSED]
Replies: 2
Views: 532

### Sif Figs for #4 Fall 2015 Quiz 1 Preparation[ENDORSED]

If a photon has a wavelength of 5.50 x10^2 nm what is its energy? 5.50 x 10^2 nm = 5.50 x 10^-7 m E = hv = (hc)/λ = ((6.626 x 10^-34 Js) (3.00 x 10^8 m/s))/(5.50 x 10^-7 m) = 3.61 x 10^19 J The answer says 3.6 x 10^-19 J, but the least amount of sig figs in the equation is 3, so I got 3.61 x 10^19 J...
Sat Oct 08, 2016 3:41 pm
Forum: DeBroglie Equation
Topic: 1.37 [ENDORSED]
Replies: 2
Views: 434

### Re: 1.37[ENDORSED]

Thank you!
Sat Oct 08, 2016 12:58 pm
Forum: DeBroglie Equation
Topic: 1.37 [ENDORSED]
Replies: 2
Views: 434

### 1.37[ENDORSED]

1.37 Protons and neutrons have nearly the same mass. How different are their wavelengths? Calculate the wavelength of each particle when traveling at 2.75 x 10^5 m/s in a particle accelerator and report the difference as a percentage of the wavelength of the neutron. Since the mass of protons and ne...
Tue Oct 04, 2016 11:34 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Atomic Spectra Post-module Question
Replies: 1
Views: 391

### Re: Atomic Spectra Post-module Question

I believe that molecular spectroscopy can be used to identify molecules because they exhibit characteristic absorption spectrums similar to how atoms do. Even though there many possible molecules, they are all composed of different elements and different numbers of those elements so molecules will a...
Mon Sep 26, 2016 9:56 pm
Forum: SI Units, Unit Conversions
Topic: Review Principles question E15
Replies: 8
Views: 1171

### Re: Review Principles question E15

OH- is a hydroxide ion, which has a charge of 1-. There are some ions that you have to memorize the charges of. The charges of the single atoms such as Na and O, you can find from the periodic table. This site highlights the trend in the periodic table you can use to find the ionic charge of atoms. ...
Sun Sep 25, 2016 3:37 pm
Forum: SI Units, Unit Conversions
Topic: Review Principles question E15
Replies: 8
Views: 1171

### Re: Review Principles question E15

What they mean by "sulfide of this metal" is the metal sulfide. So you have to write the formula of the metal sulfide. In order to do that you need to know the charge of the unknown metal atom. You can find that by looking at the given formula M(OH)2. Since the formula has the hydroxide io...