## Search found 21 matches

Mon Mar 06, 2017 11:31 pm
Forum: *Organic Reaction Mechanisms in General
Topic: Half arrows
Replies: 4
Views: 666

### Re: Half arrows

Half arrows are used when a single electron is transferred in the attack, compared to a full arrow when a pair of electrons is being transferred.
Thu Feb 23, 2017 2:23 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: How can we calculate the pH of a solution if we dilute with water?
Replies: 1
Views: 1438

### Re: How can we calculate the pH of a solution if we dilute with water?

If you're referring to the 14BL study questions, you use the original molarity given (0.010M) and do the M1V1=M2V2 calculation for the dilution to find the molarity of the solution first. So it would be: (5mL)(0.010M)=(50mL)(M) Once you solve for the molarity, you follow the same procedure you did f...
Tue Feb 21, 2017 11:42 am
Forum: Phase Changes & Related Calculations
Topic: Quiz 2
Replies: 3
Views: 564

### Re: Quiz 2

jeree pucan wrote:what pages in the course reader should we focus on for quiz 2?

Dr. Lavelle said the quiz would cover kinetics through page 73 of the course reader.
Tue Feb 21, 2017 11:41 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: Quiz 2 Practice Question 11
Replies: 2
Views: 362

### Re: Quiz 2 Practice Question 11

We haven't learned how to do these problems yet and Dr. Lavelle said that there will not be a question like this or anything regarding temperature on the quiz!
Wed Feb 15, 2017 10:21 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: When do you add Pt?
Replies: 3
Views: 556

### Re: When do you add Pt?

You add platinum to the diagram of a half reaction if there is no solid substance involved, such as if the reaction goes between two substances in aqueous states, or in the gaseous state. It's not necessarily if there is no solids at all; if the oxidation half reaction involves a solid substance but...
Sat Feb 11, 2017 5:10 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Winter 2013 Midterm
Replies: 1
Views: 248

### Re: Winter 2013 Midterm

The answer explained below the problem is calculated by breaking all of the reactant bonds and forming all of the product bonds, regardless of whether they are the same bonds that were broken in the reactants. I don't think it necessarily needs to be calculated this way, as in the calculations the b...
Mon Jan 30, 2017 10:18 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Quiz 1
Replies: 1
Views: 321

### Re: Quiz 1

You don't turn in your course reader like you did in 14A because the practice quizzes don't count for points, which is why he gave us the answers. They are just to help us study.
Mon Jan 30, 2017 9:44 pm
Forum: Administrative Questions and Class Announcements
Replies: 130
Views: 17479

### Re: Quiz 1 Preparation Answers

Can someone please explain why on #5 the answer has 2NH3 on the product side? When I did the question and canceled everything, I divided 2NH3 by 2 so that it would be the same as in the target equation N2H4 + H2 = NH3. This gave me an enthalpy of -105.1kJ/mol, instead of -151 kJ/mol. Thanks I belie...
Sat Jan 28, 2017 8:58 pm
Forum: General Science Questions
Topic: Sig Figs
Replies: 5
Views: 661

### Re: Sig Figs

Usually it's best to wait to determine sig figs until you reach the final answer, as if you round during the process you may end up with a final answer that is not as accurate as it could have been due to the rounding error.
Thu Jan 19, 2017 11:44 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Help on Problem 8.25
Replies: 1
Views: 272

### Re: Help on Problem 8.25

Because you are calculating the heat lost by solely the calorimeter itself, there is no mass of substance involved. This eliminates the need for mass in the equation, as the heat capacity of the calorimeter is not dependent on its mass like a substance with a specific heat would be. Hope this helps!
Mon Jan 16, 2017 9:41 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Replies: 4
Views: 582

Since there is an equal amount of a strong acid and a strong base that each have the same molarity, each of the reactants will react entirely as the reaction goes to completion. Therefore all of the H+ and OH- will all convert to water and there will be no excess, which explains why the problem only...
Mon Nov 28, 2016 10:00 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Homework Help 12.65
Replies: 4
Views: 1057

### Re: Homework Help 12.65

In order to determine if an aqueous solution of these compounds will have a pH greater, equal to, or less than 7, you must write out the chemical equation that would result by reacting these compounds with water. The salts you are given will ionize and the ions will react with the water to form acid...
Mon Nov 28, 2016 9:38 pm
Forum: Bronsted Acids & Bases
Topic: Common Acids/Bases
Replies: 3
Views: 482

### Re: Common Acids/Bases

Knowing which acids and bases are strong vs. weak will help you in quickly determining whether to use an ICE table or not, so it would probably be useful to have them memorized. However, you can also recognize that if a Ka/Kb value is given the acid/base must be weak, as the value would not be given...
Wed Nov 23, 2016 6:13 pm
Forum: Properties of Light
Topic: 2012 Final Q 1B
Replies: 1
Views: 386

### Re: 2012 Final Q 1B

I think that if you get the correct answer and show your work then you should get all of the points even if you used a different process!
Mon Nov 21, 2016 10:03 pm
Forum: Lewis Acids & Bases
Topic: Acid and Bases
Replies: 1
Views: 318

### Re: Acid and Bases

I believe that today in lecture he explained that these all mean the same thing, as when it ionizes it is also deprotonating and these both result with ions as a product so they all refer to the same number.
Wed Nov 02, 2016 2:02 pm
Forum: Lewis Structures
Topic: Octet rule
Replies: 7
Views: 776

### Re: Octet rule

If the question specifies to follow the octet rule you would not use an expanded octet, just 8e-.
Fri Oct 28, 2016 4:51 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: O3 Polarity
Replies: 1
Views: 408

### Re: O3 Polarity

If you were to draw out the Lewis structure for O3, it ends up with the central O atom having a single bond with one of the oxygen atoms, a double bond with the other oxygen atom, and a lone pair. Because the central atom has a single bond with one of the oxygen atoms and a double bond with the othe...
Wed Oct 26, 2016 4:14 pm
Forum: Hybridization
Topic: Chapter 4 Question 35
Replies: 1
Views: 949

### Re: Chapter 4 Question 35

sp3 is not necessarily for a tetrahedral shape, it is for any molecule with 4 regions of electron density. In this case, Se has 3 bonds, a single bond with each of the three F atoms, and a lone pair in order to satisfy the octet rule and the 26 electrons for the molecule. The 3 single bonds plus the...
Sat Oct 15, 2016 1:15 pm
Forum: Lewis Structures
Topic: Lewis Structure
Replies: 3
Views: 565

### Re: Lewis Structure

A disadvantage of lewis structures is that it is difficult to show resonance structures visually, such as the NO3- example from lecture, as you can't discretely draw 1 and 1/3 bonds between the two atoms.
Fri Oct 07, 2016 11:24 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Assigning Spin to States
Replies: 1
Views: 331

### Re: Assigning Spin to States

In terms of your question about assigning spin to electrons in Px, Py, Pz orbitals, only two electrons can reside in each of the P suborbitals, and if two electrons are in the suborbital they will be assigned parallel spin similar to how you would assign spin to electrons in an S orbital, so one is ...
Fri Sep 30, 2016 7:02 pm
Forum: Student Social/Study Group
Topic: Chemistry Joke
Replies: 18
Views: 1996

### Re: Chemistry Joke

Q: What do you get if you swap the carbon atoms in a benzene ring for iron atoms?
A: A ferrous wheel!