## Search found 22 matches

Mon Mar 07, 2016 3:57 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Solution Manual Error Not Yet Spotted? (8.63c)
Replies: 1
Views: 315

### Solution Manual Error Not Yet Spotted? (8.63c)

I don't know whether anybody else has posted about this, but I saw this error today after review some chemistry problems and did not see it in the solutions manual error page. In Chapter 8, #63c, the problem asks you to find the standard reaction enthalpy. The equation is: H2S(aq)+2KOH(aq)->K2S(aq)+...
Sun Mar 06, 2016 10:40 am
Forum: Phase Changes & Related Calculations
Topic: 2010 Final Exam Q1B: Which is greater delta H?
Replies: 1
Views: 304

### 2010 Final Exam Q1B: Which is greater delta H?

The part I'm struggling with is the second part of the question which asks: Which requires more heat: Breaking one mole of carbon-carbon single bonds or melting one mole ice? The answer states "breaking a covalent bond" but aren't both of these bonds O-H and C-C covalent bonds?? I put that...
Thu Feb 25, 2016 10:55 am
Forum: *Aldehydes
Topic: Chapter 2 Number 42: Naming an aldehyde
Replies: 1
Views: 647

### Chapter 2 Number 42: Naming an aldehyde

The question asks: A methyl derivative of citronellal is being tested as a stronger insect repellent against mosquitoes that carry malaria. Write the IUPAC name for: o=CH-CH(CH3)-CH(CH3)-CH2-CH2-CH=C(CH3)2. I got 2,3,7-trimethyloct-6-en-1-al. The book states that the answer is 2,3,7-trimethyloct-6en...
Tue Feb 23, 2016 2:09 pm
Forum: *Alkanes
Topic: Aliphatic Hydrocarbons
Replies: 1
Views: 329

### Re: Aliphatic Hydrocarbons

An aliphatic hydrocarbon actually means that the hydrocarbon does not have a ring present in the structure. This can include double and triple bonds as long as there is no ring.
Tue Feb 16, 2016 11:37 pm
Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
Topic: Electrolytic Cell
Replies: 1
Views: 381

### Electrolytic Cell

Why is an electrolytic cell different than a galvanic cell? How does it work?
Tue Feb 16, 2016 11:34 pm
Forum: General Rate Laws
Topic: Rate Laws in Graphs
Replies: 1
Views: 485

### Rate Laws in Graphs

I know that 2nd order rate laws must be graphed differently in order to determine k, but what is the difference between making a graph molarity vs time, 1/M vs time, and ln(M) vs time?s
Sun Feb 14, 2016 4:55 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Electrodes and Cell Diagrams
Replies: 2
Views: 345

### Re: Electrodes and Cell Diagrams

Galvanic cells are positive cells. The overall charge on a galvanic cell is positive simply because that's the definition of a galvanic cell. Keep in mind that galvanic cells can refer to fuel cells, rocket fuel, a battery cell, or many other names.
Sun Feb 14, 2016 4:51 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: How to separate solids in a cell diagram
Replies: 3
Views: 464

### Re: How to separate solids in a cell diagram

Why would you even need the Pt? One solution is aqueous and the other is solid, and the solid would function as the electrode. Am I missing something?
Fri Jan 29, 2016 7:17 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Residual Molar Entropy
Replies: 3
Views: 521

### Re: Residual Molar Entropy

Use the equation klnW. (Because many organic compounds specify how to draw each one, there are limited ways of drawing them). Count up the different ways and use the equation.
Fri Jan 29, 2016 7:11 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Quiz 1 Preparation Question (Gibbs Free Energy?)
Replies: 2
Views: 1789

### Re: Quiz 1 Preparation Question (Gibbs Free Energy?)

Bonds are being broken, so it is endothermic. The delta H would be positive.
Fri Jan 29, 2016 7:09 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Constant Pressure, Constant Volume Work
Replies: 1
Views: 422

### Re: Constant Pressure, Constant Volume Work

If gas is generated, then work is done so you include work in the change in internal energy.
Fri Jan 29, 2016 7:07 pm
Forum: Calculating Work of Expansion
Topic: calculating work
Replies: 2
Views: 382

### Re: calculating work

Reversible uses more work. The equation for that is w=-nRTln(V2/V1). For irreversible, use the equation w=P delta V. The pressure of work is the pressure of surroundings.
Sun Nov 15, 2015 9:16 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Homework Question 11.63: a question on assuming
Replies: 1
Views: 296

### Homework Question 11.63: a question on assuming

After following the ICE method, I reached an impasse with my calculator when I did the calculation: x^{2}-(1.28\cdot 10^{-33})x^{2} and got 1 (which I should have known seeing as anything 10^{33} will be really close to 0). Anyways, my question is when is the correct time to practice assumin...
Sun Nov 15, 2015 9:05 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Question on a step in 11.61?
Replies: 2
Views: 500

### Re: Question on a step in 11.61?

I believe the solutions manual is wrong. I literally multiplied the calculations they had put together and they didn't even get the numbers they posted. I checked my math roughly about 100 times because I thought I was wrong.
Mon Nov 02, 2015 3:46 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Idean's Chemistry Review Question #8
Replies: 1
Views: 346

### Idean's Chemistry Review Question #8

The question asks, "What is the minimum uncertainty in the position of an electron confined to within the diameter of a zinc atom with an uncertainty in velocity of 3.00x10 6 \pm 2.24* 10^{6} ms? The diameter of a zinc atom is 139 pm. Are we certain that the electron is confined within the atom...
Mon Nov 02, 2015 3:41 pm
Forum: Ionic & Covalent Bonds
Topic: Drawing Ionic Bonds
Replies: 1
Views: 418

### Drawing Ionic Bonds

How would you draw ionic bonds since the bond is actually electrostatic attraction?
Fri Oct 30, 2015 12:30 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8205
Views: 1433323

### Re: Chemistry Jokes

Heisenberg calls up Pauli and says, "I have an idea that will revolutionize quantum physics!" to which Pauli replies, "Are you certain?!"
Heisenberg says, "Not at all!"
Sun Oct 25, 2015 11:45 pm
Forum: Sigma & Pi Bonds
Topic: Conceptual Explanation of Pi Bonds
Replies: 1
Views: 355

### Re: Conceptual Explanation of Pi Bonds

The first bond formed between two atoms is always a sigma bond. This creates an head-on overlapping between bonds. The pi bonds are then formed because the next two regions of electron density are perpendicular to the head-on sigma bonds. Think of two right angles facing each other. Imagine that eac...
Sat Oct 17, 2015 10:16 pm
Forum: Octet Exceptions
Replies: 1
Views: 390

### Re: Homework Problem 3.123: Radicals

Actually, the carbon should bond twice with one of the oxygens, leaving another oxygen with 7 valence electrons. This makes it a radical because there is one uncompleted octet. Because the structure is not ionized, there is no way for the oxygen to gain another electron as it does not apply for the ...
Sun Oct 04, 2015 9:13 pm
Forum: Empirical & Molecular Formulas
Topic: M21
Replies: 2
Views: 518

### Re: M21

Sorry. I made a typo. Find out the percentage of the element in the molecule. You can do that by dividing the mass of the element by the mass of the sample given.
Sun Oct 04, 2015 9:10 pm
Forum: Empirical & Molecular Formulas
Topic: M21
Replies: 2
Views: 518

### Re: M21

Yes. Attempt to find out how much each element would weigh, then find out the percentage of element in each atom. Convert percentages to whole numbers (pretending the sample is made of 100 grams is easiest) and then find the empirical/molecular formula from then on.
Sun Oct 04, 2015 9:07 pm
Forum: Significant Figures
Topic: Multiplying/Dividing with Sig Figs
Replies: 1
Views: 451

### Multiplying/Dividing with Sig Figs

When I use stoichiometry, I cross multiply and cancel in order to cancel out the units. Because of this I often divide or multiply by 1 unit integers. Does this mean when using significant figures, I have to round to 1 sig fig?