## Search found 12 matches

Sat Dec 13, 2014 11:57 pm
Forum: *Making Buffers & Calculating Buffer pH (Henderson-Hasselbalch Equation)
Topic: Choosing a Buffer
Replies: 2
Views: 392

### Re: Choosing a Buffer

ohh pKa! Thanks!
Sat Dec 13, 2014 11:53 pm
Forum: Lewis Structures
Topic: SO2 Lewis Structure
Replies: 3
Views: 722

### Re: SO2 Lewis Structure

But in question 5B of Final Exam 2011, the answer given has only one double bond. Even though it says that a two-double-bond structure is also acceptable, why is a one-double-bond structure even permissible in the first place?
Sat Dec 13, 2014 11:51 pm
Forum: *Titrations & Titration Calculations
Topic: Titrant Equations
Replies: 2
Views: 508

### Titrant Equations

How do you write the equation for a titration problem? The 2011 Final Exam Q#8B mentions NH3 in the question but writes the ICE box equation as NH4(+) + H2O <---> NH3 + H3O+ It also says you have the salt NH4Cl and water. But how do you know that that molecule is formed and why is it not in the equa...
Sat Dec 13, 2014 11:41 pm
Forum: *Making Buffers & Calculating Buffer pH (Henderson-Hasselbalch Equation)
Topic: Choosing a Buffer
Replies: 2
Views: 392

### Choosing a Buffer

How do you choose a buffer for a reaction?
I know you need the pH of the buffer to be specific to keep the reaction in optimal conditions, but will we be given the pH's of buffers in a question, or do we have to memorize pH's of common buffers to be able to use them on the final?
Sat Dec 13, 2014 11:36 pm
Forum: Lewis Structures
Topic: SO2 Lewis Structure
Replies: 3
Views: 722

### SO2 Lewis Structure

Does the lewis structure of SO2 have two double bonds or only a double bond on one of the oxygens? I've seen examples of the latter, but that doesn't make sense to me because the formal charges would be +1 and -1.
Sat Dec 13, 2014 11:24 pm
Forum: Student Social/Study Group
Topic: Points for Chemistry Community
Replies: 1
Views: 766

### Points for Chemistry Community

So do you still get points for Chemistry Community if all of your posts are on the night before the final? Even if they are serious questions that you've been wondering about for a while but have never gotten around to asking?
Sat Dec 13, 2014 11:15 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Strength of Acids
Replies: 2
Views: 471

### Strength of Acids

Are there any easy tricks to determine if an acid or base is strong or weak?
Sat Dec 13, 2014 11:12 pm
Forum: Amphoteric Compounds
Topic: How to tell something is amphoteric?
Replies: 4
Views: 1972

### Re: How to tell something is amphoteric?

What about for other molecules that are not in a similar As2O3 form? How do you tell if they are amphoteric or not?
Sat Dec 13, 2014 11:10 pm
Forum: Significant Figures
Topic: pH Sig Figs
Replies: 2
Views: 684

### pH Sig Figs

Why are the sig figs in the answers to pH problems always off by one?
For example:
2011 Final Exam Q#8B
Kb is 1.8 x 10^-5 and has two sig figs but the answer is 5.24 with three sig figs.
Sat Dec 13, 2014 11:05 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Final 2011 #2A
Replies: 1
Views: 355

### Final 2011 #2A

At the bottom of the page, it says "If students leave change in energy as positive 5.00x10^-19J" that they don't get full credit.
I know Dr. Lavelle said something about negative energy in class, but can someone explain how a positive answer would be wrong?
Sat Dec 13, 2014 10:59 pm
Forum: Lewis Acids & Bases
Topic: Amphoteric Oxides
Replies: 2
Views: 698

### Re: Amphoteric Oxides

For example Aluminum hydroxide will act as a base when there is an acid for it to neutralize:
Al(OH)3 + 3 HCl → AlCl3 + 3 H2O

but it will act as an acid when it has to neutralize a base:
Al(OH)3 + NaOH → Na[Al(OH)4]
Sat Dec 13, 2014 10:50 pm
Forum: *Titrations & Titration Calculations
Topic: Henderson-Hasselbach Equation
Replies: 4
Views: 629

### Henderson-Hasselbach Equation

When would you use the Henderson-Hasselbach equation?