## Search found 25 matches

Tue Mar 08, 2016 10:38 pm
Forum: *Cyclohexanes (Chair, Boat, Geometric Isomers)
Topic: cis conformation
Replies: 2
Views: 387

### Re: cis conformation

Tue Mar 08, 2016 10:26 pm
Forum: *Cyclohexanes (Chair, Boat, Geometric Isomers)
Topic: Boat Conformation Hydrogens
Replies: 1
Views: 294

### Re: Boat Conformation Hydrogens

I believe it's referring to the bottom four hydrogens but I'm not sure
Mon Feb 29, 2016 11:51 pm
Forum: *Organic Reaction Mechanisms in General
Topic: 4.25 charge difference?
Replies: 1
Views: 282

### 4.25 charge difference?

On question 4.25, one of the species involved is Br2. The solution shows that there is an electronegativity difference between the two bromine molecules, saying one is more negative and the other more positive. Why is this so considering it is the same element bonded to itself? Shouldn't there be no...
Sun Feb 21, 2016 9:07 pm
Forum: Zero Order Reactions
Topic: Zero order
Replies: 5
Views: 799

### Re: Zero order

The rate law for a zero order reaction is rate=k. Can also be written as rate=k[A]^0 to more plainly see that it is zero. From this you can tell that the concentration of the reactant will have no affect on the rate of the reaction, as it is solely dependent on the rate constant k.
Thu Feb 18, 2016 10:38 am
Forum: Reaction Mechanisms, Reaction Profiles
Replies: 2
Views: 866

In lecture Dr. Lavelle said to just use the pre-equilibrium method rather than the steady-state one. He purposely only assigned textbook problems that use pre-equilibrium instead of steady-state.
Sun Feb 14, 2016 8:58 pm
Forum: General Rate Laws
Topic: Units for reaction rates
Replies: 1
Views: 298

### Re: Units for reaction rates

Judging from past expectations from Dr. Lavelle, I would assume it doesn't matter unless the answer corresponds to sig figs and has accurate units. As in look at sig figs first and adjust units accordingly.
Sat Feb 06, 2016 2:05 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Notation of cell diagrams
Replies: 1
Views: 291

### Notation of cell diagrams

How do we know when to use a comma versus the vertical line in a cell diagram?
Sat Feb 06, 2016 2:02 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: anode and cathode
Replies: 1
Views: 215

### Re: anode and cathode

The values stated in the table are reduction potentials, so if you have two different pairs of species and are trying to decide which pair undergoes reduction and which undergoes oxidation, the one with the higher reduction potential is the one more likely to be reduced. Therefore the other species ...
Tue Feb 02, 2016 12:37 am
Forum: Balancing Redox Reactions
Topic: example 14.1
Replies: 1
Views: 310

### Re: example 14.1

The molecule is C2H2O4. We know H is almost always +1, and O is almost always -2. The overall charge of the compound is 0. For hydrogen, 2x1 is +2, and for oxygen, 4x(-2) is -8. Adding these together gives -6. So we know that the total charge of the carbons must be +6 for the molecule's charge to eq...
Sun Jan 31, 2016 5:43 pm
Forum: Balancing Redox Reactions
Topic: Coulomb
Replies: 4
Views: 657

### Re: Coulomb

I don't think it's written anywhere in the course reader, but Dr. Lavelle said one coulomb is equivalent to the charge of 10^18 electrons
Sun Jan 24, 2016 4:29 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Homework Question 8.49 - Why can you not use a mole ratio?
Replies: 4
Views: 677

### Re: Homework Question 8.49 - Why can you not use a mole rati

Whenever temperature is not given in a situation where it is needed for calculations, always assume it is 298K (25 degrees Celcius) because that is part of standard conditions.
Sun Jan 24, 2016 4:24 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hess's Law
Replies: 3
Views: 413

### Re: Hess's Law

Remember when you multiply all the coefficients by a common number, that common number doesn't necessarily have to be or yield whole numbers. They could result in improper fractions as well.
Sun Jan 17, 2016 11:40 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Homework 8.31
Replies: 4
Views: 563

### Re: Homework 8.31

The solutions manual includes 20.8 J*mol^-1*C^-1 in the calculation for this solution; where does this value come from?
Mon Jan 11, 2016 11:07 am
Forum: Phase Changes & Related Calculations
Topic: Phase Changes- Melting/Boiling
Replies: 4
Views: 601

### Re: Phase Changes- Melting/Boiling

Usually the constant controlled temperature of the system can be explained by the setup of the experiment, which is not always mentioned. For example, Dr. Lavelle mentioned an experiment that could occur underwater in water of a uniform temperature, or in a closed system such as a calorimeter.
Tue Dec 01, 2015 8:13 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Ka/Kb values not listed
Replies: 1
Views: 325

### Ka/Kb values not listed

Hello, For problems 65 through 73 on the Chapter 12 homework, we are given initial concentrations (or information to find initial concentrations) of acids and bases and are asked to find their pH. However, their K values do not appear in tables 12.1 and 12.2. Do we need to look them up ourselves or ...
Mon Nov 30, 2015 4:47 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8046
Views: 1412593

### Re: Chemistry Jokes

A neutron walks into a bar.
Before leaving, he asks the bartender, "How much?"
The bartender responds, "No charge."
Sun Nov 29, 2015 9:15 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Pressure aspect of Le Chatelier's Principle
Replies: 2
Views: 629

### Re: Pressure aspect of Le Chatelier's Principle

Change in pressure is driven by a change in volume because from the ideal gas law, we can see that P=(nRT)/V. Thus, a change in volume always results in a change in pressure. The change in pressure will never simply be a change in pressure in itself because that would mean calculating the increased ...
Fri Nov 20, 2015 5:05 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Replies: 2
Views: 484

Hi! Adding water could reduce concentration because there would be the same amount of moles of a substance but in a larger volume of solution. However it all depends on the problem, and usually information will be given that would allow you to determine the new initial concentrations to put into the...
Thu Nov 12, 2015 10:00 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Relationship between K and Q
Replies: 3
Views: 508

### Re: Relationship between K and Q

You are correct about K and Q being calculated in the same way. From what I've been seeing, in questions involving Q, K is usually given and you are asked to find Q in order to determine whether or not the reaction is at equilibrium and in what way the reaction will occur to approach equilibrium. I ...
Thu Nov 05, 2015 4:50 pm
Forum: Hybridization
Topic: Unpaired electrons
Replies: 2
Views: 380

### Re: Unpaired electrons

I believe that even an unpaired electron would still count as a region of electron density, so it would be included in hybridization. But we're rarely asked anything about radicals so I wouldn't worry about it too much.
Thu Oct 29, 2015 10:27 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: formal charge
Replies: 3
Views: 486

### Re: formal charge

^The above scenario is something I've never heard of or encountered so I can't give a definite answer for that. However, if two different resonance structures both yield an overall formal charge of 0, the more stable one is one in which more individual atoms have a charge of 0, so if one structure y...
Fri Oct 23, 2015 1:09 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polar Bonds
Replies: 2
Views: 425

### Re: Polar Bonds

^The above procedure determines if the molecule as a whole is polar or not. To answer your question about determining if an individual bond is polar, you have to look at the electronegativity of each element in the bond. If there is a difference in electronegativity, there is a "dipole moment&q...
Fri Oct 16, 2015 11:13 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Resonance Structures and VSEPR
Replies: 1
Views: 345

### Re: Resonance Structures and VSEPR

Resonance structure is reflected in VSEPR in that the double/triple bonds appear shorter than single bonds (shorter lines in the drawings).
Thu Oct 08, 2015 3:35 pm
Forum: Properties of Light
Topic: Wavelength Problem
Replies: 1
Views: 403

### Re: Wavelength Problem

So I see that this problem is from the 5th edition book, which doesn't really correspond much to the 6th edition as far as homework problems go. To solve this you would first use Rydberg's equation: Frequency= Z^2 * R(1/(n initial squared) - 1/(n final squared)) Once you determine the frequency from...
Thu Oct 01, 2015 8:59 pm
Forum: Significant Figures
Topic: Basic Rules for Sig Figs
Replies: 3
Views: 603

### Re: Basic Rules for Sig Figs

-Zeros that are only used to set a decimal point are NOT significant (e.g. 0.0005 has 1 sig fig, as does 2000) -Zeros in between two integers ARE significant (e.g. 6067 has 4 sig figs) -Zeros trailing after a decimal ARE significant (e.g. 6067.300 has 7 sig figs) -100 has 1 sig fig, but 100. has 3 s...