## Search found 23 matches

Sat Mar 07, 2015 8:59 pm
Forum: *Alkanes and Substituted Alkanes (Staggered, Eclipsed, Gauche, Anti, Newman Projections)
Topic: Butane Newman Projection
Replies: 3
Views: 766

### Re: Butane Newman Projection

If a problem does not specify which bond to look at, can we assume it's the c2-c3 bond in butane's case?
Sat Mar 07, 2015 9:26 am
Forum: *Alkanes and Substituted Alkanes (Staggered, Eclipsed, Gauche, Anti, Newman Projections)
Topic: Butane Newman Projection
Replies: 3
Views: 766

### Butane Newman Projection

For butane, is the newman projection alwats drawn with respect to the C2-C3 bond?
Tue Feb 10, 2015 1:36 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: When to use Cv vs Cp
Replies: 6
Views: 1017

### Re: When to use Cv vs Cp

I still don't quite understand how it can compress but still have the same volume? If it's compressing its volume is supposed to decrease. Therefore there is a change in volume.
Tue Feb 10, 2015 10:57 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: When to use Cv vs Cp
Replies: 6
Views: 1017

### Re: When to use Cv vs Cp

Bumppp
Mon Feb 09, 2015 7:56 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Solving for concentration using G=-RTlnK
Replies: 1
Views: 824

### Solving for concentration using G=-RTlnK

For Midterm 2010 5B, why do we need to solve for concentration of HBr using traditional stoichiometry given that there is 120. ml of H2 gas at 273.15K and 1.00 atm? Could we use G=-RTlnK and plug in G which was solved for in part a along with the given info which would be values plugged into K=P/R?
Mon Feb 09, 2015 7:46 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: When to use Cv vs Cp
Replies: 6
Views: 1017

### When to use Cv vs Cp

For Midterm 2010 4A, I don't understand why we need to use Cv when the volume is obviously changing due to compression. I read in a post from last year that we can just assume that since pressure isn't mentioned in the problem that we don't know if pressure is constant. I still can't wrap my head ar...
Thu Feb 05, 2015 3:31 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: n when calculating Ecell (h2,h+)
Replies: 1
Views: 410

### n when calculating Ecell (h2,h+)

When calculating Ecell, the n value for the redox rxn for H2 and H+ should be 2 since the half reactions need 2 electrons to balance the charges. For HW 39b, the solutions says that for this particular redox rxn n=1, but for the same redox rxn in 41a, they use n=2...I'm a bit confused as to why this...
Sun Jan 18, 2015 9:06 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: HW 101(b) enthalpy of combustion
Replies: 1
Views: 356

### HW 101(b) enthalpy of combustion

For 101 part b, why do we need to use the enthalpy of formation for c6h6 when calculating the enthalpy of the rxn if benzene is involved in a combustion rxn? Shouldn't we use the enthalpy of combustion for benzene?
Sat Jan 10, 2015 12:28 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Replies: 3
Views: 543

For a problem like 7.63, why do we need to write out all of the equations of the reactants and products? Why can't we simply use the equation: delta H rxn = sum(delta H products) - sum(delta H reactants)?
Thu Jan 08, 2015 10:59 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard enthalpy of Zn(s)
Replies: 2
Views: 9624

### Re: Standard enthalpy of Zn(s)

Oh! So basically the zncl2 separates into aqueous species in solution? So that's why its calculated separately! Thank you!!
Thu Jan 08, 2015 10:19 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard enthalpy of Zn(s)
Replies: 2
Views: 9624

### Standard enthalpy of Zn(s)

For 7.53 in the txt book, the standard enthalpy of Zn(aq) (-153.89 kj/mol) is used in determining the delta h of the rxn 2hcl(aq)+zn(s)--> h2(g)+zncl2(aq). I don't understand why 0 is not used for solid zinc since it is in its natura most stable state.
Sat Dec 13, 2014 7:07 am
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Ka vs Kb
Replies: 1
Views: 998

### Re: Ka vs Kb

We know to use ka when the final equation has an h30+ on the products side because then the resulting solution would be acidic. Use kb when the final equation has oh- on the products side because the resulting solution will be basic. At the stoich pt the ph>7 bc this a weak acid/strong base calculat...
Sat Dec 13, 2014 6:59 am
Forum: *Making Buffers & Calculating Buffer pH (Henderson-Hasselbalch Equation)
Topic: Guide to calculating buffer problems
Replies: 1
Views: 418

### Guide to calculating buffer problems

Attached is what I found to be a useful guide to calculating buffer problems which I definitely think are tricky. Hope it helps!
Sat Dec 13, 2014 6:57 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: How to calculate equilibrium problems
Replies: 1
Views: 509

### How to calculate equilibrium problems

Attached is a helpful guide to solving different equilibrium problems. Hopefully it can clear up any confusion on how to calculate various aspects of equilibrium problems.
Tue Dec 09, 2014 8:04 pm
Forum: *Titrations & Titration Calculations
Topic: Calculating each phase of a Titration
Replies: 2
Views: 407

### Calculating each phase of a Titration

For 12.29 part b, it asks to calculate what the pH will be when 5.0 mL of ACID is added to the titration of 0.150 M HCl and 25.0 mL of 0.110 M NaOH. ((NaOH) is the titrant). In the solutions manual it calculates the excess OH- in order to determine the final [OH-] to determine the pOH. I don't under...
Tue Dec 09, 2014 7:36 pm
Forum: *Titrations & Titration Calculations
Topic: Calculating each phase of a Titration
Replies: 1
Views: 401

### Calculating each phase of a Titration

For 12.29 part b, it asks to calculate what the pH will be when 5.0 mL of ACID is added to the titration of 0.150 M HCl and 25.0 mL of 0.110 M NaOH. ((NaOH) is the titrant). In the solutions manual it calculates the excess OH- in order to determine the final [OH-] to determine the pOH. I don't under...
Mon Dec 01, 2014 7:43 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Quiz 3 #10
Replies: 8
Views: 1102

### Re: Quiz 3 #10

There's a conversion formula to convert Kp into Kc which would match the mole/L aspect of the problem. The formula is: Kp=Kc(RT)^delta n Where R is the gas constant 0.08206 (L x atm)/ (mol X K) T is the temp in Kelvins delta n is the number of gaseous moles in product - number of gaseous moles in re...
Mon Dec 01, 2014 7:15 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Quiz 3 Prep Fall 2012 #5
Replies: 3
Views: 451

### Re: Quiz 3 Prep Fall 2012 #5

Stoichiometric coefficients can be fractions as long as the equation is balanced correctly. For gases, Kp and Kc can both be applied since gases can be measured using pressure units (atm, bar etc..) or concentration (moles/L).
Mon Dec 01, 2014 7:13 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Quiz 3 Preparation Fall 2013 Quiz: #10
Replies: 9
Views: 1471

### Re: Quiz 3 Preparation Fall 2013 Quiz: #10

For determining the new partial pressure of BrCl in the new equilibrium mixture, I'm a unclear as to whether we are supposed to use the rxn given, 2BrCl --> Br2 + Cl2, or the reverse rxn, Br2 + Cl2 --> 2BrCl, since a NEW equilibrium is being established from the remaining pressures of the initial eq...
Sun Nov 30, 2014 9:35 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Quiz 3 Prep, Fall 2012 #8
Replies: 6
Views: 744

### Re: Quiz 3 Prep, Fall 2012 #8

So far this is what I've worked out so far but I can't seem to get the correct x values. I don't know if it's because I calculated the quadratic incorrectly or if I didn't set up the problem right. Any suggestions are appreciated! :)
Sun Oct 19, 2014 10:50 am
Forum: Trends in The Periodic Table
Topic: Trends in Atomic and Ionic Radius
Replies: 2
Views: 524

### Re: Trends in Atomic and Ionic Radius

I talked to my TA and confirmed with him that the answers in the Solutions Manual are wrong for 129. The answers are indeed switched around.
Sat Oct 18, 2014 2:12 pm
Forum: DeBroglie Equation
Topic: Quiz 1 Prep Fall 2013 Q10
Replies: 2
Views: 563

### Quiz 1 Prep Fall 2013 Q10

I can't seem to figure this one out. The only equation to solve for kinetic energy is E=1/2(mv)^2. For this problem the wavelength is given as 194 nm and I need to solve for max KE. Since velocity is not given, I used the debroglie wavelength formula to solve for velocity, plugged that answer into E...
Sat Oct 18, 2014 1:15 pm
Forum: Trends in The Periodic Table
Topic: Knowing Electronegativity
Replies: 2
Views: 489

### Re: Knowing Electronegativity

You don't need to necessarily memorize the electronegativity values because there is a concept as to why the trend increases from left to right and decreases from top to bottom. Since there are more protons as you go from L to R, the attraction between the nucleus (where protons are located) and ele...