## Search found 35 matches

Fri Mar 13, 2015 6:41 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 2010 Final #2A RXN Enthalpy
Replies: 2
Views: 464

### 2010 Final #2A RXN Enthalpy

Hey Everyone!

Why was the standard enthalpy for 3BaO(s)-->3Ba(s)+3/2O2 deltaH=1660.5 kJ
when all we changed originally was flipping the equation, so only the sign should change?

Thank you!!
Thu Mar 12, 2015 11:01 pm
Forum: First Order Reactions
Topic: KemiStry with Kayla and Sarah - Quiz 2 Review!
Replies: 6
Views: 2278

### Re: KemiStry with Kayla and Sarah - Quiz 2 Review!

Awesome!

Thank you, Neil!!
Thu Mar 12, 2015 5:06 pm
Forum: First Order Reactions
Topic: KemiStry with Kayla and Sarah - Quiz 2 Review!
Replies: 6
Views: 2278

### Re: KemiStry with Kayla and Sarah - Quiz 2 Review!

Hey Neil!

Thank you!

So is the integration rule adding one to the exponent then putting that exponent in front?
Thu Mar 12, 2015 4:52 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: KemiStry with Kayla and Sarah - Pre-Equilibrium/Steady State
Replies: 5
Views: 2227

### Re: KemiStry with Kayla and Sarah - Pre-Equilibrium/Steady S

Hey Kayla and Sarah!

When explaining why to use the 2 and 3 steps, it was said that "use the forward slow and fast reverse" but on the board it is written "Slow..., reverse."

Which is it?

Thank you!!
Thu Mar 12, 2015 4:05 pm
Forum: First Order Reactions
Topic: KemiStry with Kayla and Sarah - Quiz 2 Review!
Replies: 6
Views: 2278

### Re: KemiStry with Kayla and Sarah - Quiz 2 Review!

Hey Kayla & Sarah! Can you explain again why in the second order we derive [A] -2 to be -[A] -1 instead of -2[A] -3 ? I'm not sure how negatives work with these derivatives. Also, just for clarification, are each of the final equations are set up to find a new concentration since in each eaquati...
Wed Feb 11, 2015 3:09 pm
Forum: Administrative Questions and Class Announcements
Topic: Re: **Important Midterm Information Winter 2015**
Replies: 6
Views: 11829

### Re: **Important Midterm Information Winter 2015**

To clarify for the butterfinger & child example, we are using the grams/mass of the child in the specific heat capacity equation because we are solving for the T f of the what happens to the surroundings (child)? Whereas we include the heat released since it is released into the surroundings, de...
Wed Feb 11, 2015 2:05 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Video: KemiStry with Kayla & Sarah/Multi-Step Entropy Change
Replies: 3
Views: 797

### Re: Video: KemiStry with Kayla & Sarah/Multi-Step Entropy Ch

Hope you two upload more! :)
Wed Feb 11, 2015 10:25 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Video: KemiStry with Kayla and Sarah KEG Party
Replies: 10
Views: 1786

### Re: Video: KemiStry with Kayla and Sarah KEG Party

I have a mac too, I think the problem is firefox asked for me to download or activate flip (which didn't work), but Safari allows me to play them.

Wed Feb 11, 2015 10:06 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Video: KemiStry with Kayla and Sarah KEG Party
Replies: 10
Views: 1786

### Re: Video: KemiStry with Kayla and Sarah KEG Party

Is there a way that I don't have to download the video to watch it? I tried to watch both uploads.
Thu Jan 29, 2015 11:51 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Quiz 1 Prep #11, two-step process, adiabatically to deltaU
Replies: 1
Views: 535

### Quiz 1 Prep #11, two-step process, adiabatically to deltaU

#11 "A system undergoes a two-step process. In step 1, it expands adiabatically from 1L to 2.56L at 1atm (external pressure). In step 2, it releases 73J of heat at 1atm as it returns to the original internal energy. Find the final volume of the system." Can anyone please outline the steps ...
Wed Jan 28, 2015 10:23 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Replies: 1
Views: 797

Hey everyone!! I need some clarification on entropy; when are we supposed to add entropies vs. subtract entropies? Do we add only when a change of volume as change of temperature is given (& no equation is given)? And subtract if an equation w/ the entropies of an equation w/ products & reac...
Tue Jan 27, 2015 10:44 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Video: Heat and 1st Law of Thermodynamics - Week 2
Replies: 3
Views: 760

### Re: Video: Heat and 1st Law of Thermodynamics - Week 2

Just to clarify with the concept q sys =-q surr in your video, in the first example we are told we are working with an ideal gas, and in the second example, we are told no energy is lost to the surroundings, and we use q sys =-q surr for both; so this means that for an ideal gas, it never loses ener...
Mon Jan 26, 2015 10:51 pm
Forum: Phase Changes & Related Calculations
Topic: General Enthalpy & Phase Change Idea Q.
Replies: 1
Views: 515

### General Enthalpy & Phase Change Idea Q.

Hey Everyone! I am confused on what the change of enthalpy is calculating exactly in terms of each phase state and change. Is it the amount of heat energy constantly being lost or absorbed at that time (pressure?)? And could this be regardless of if it's changing phases (or is it always changing?)? ...
Fri Jan 09, 2015 12:35 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hess' Law & Standard enthalpy subtr. 7.13A Self-test
Replies: 1
Views: 396

### Hess' Law & Standard enthalpy subtr. 7.13A Self-test

Hey everyone!

In 7.13A, why is the second equation & change in enthalpy subtracted from the first equation & change in enthalpy?
When does this occur versus addition?

Thank you!!
Sat Dec 13, 2014 11:38 am
Forum: Empirical & Molecular Formulas
Topic: Midterm Q2A How to find Xylitol (first step)
Replies: 1
Views: 1292

### Midterm Q2A How to find Xylitol (first step)

Hey! So I know a question regarding the same problem is on here already, but it's not the same question as mine. Why did we have to multiply the molar mass by the non-percentage form of the problem? I thought we could just see the percentages as grams and divide by molar weights (ex: 39.43g of C; th...
Thu Dec 11, 2014 3:31 pm
Forum: Identifying Acidic & Basic Salts
Topic: F-H weak acid significance
Replies: 1
Views: 451

### F-H weak acid significance

Hey! I was reviewing the podcast for 12/03 and Professor Lavelle made a point to emphasize that FH is a weak acid, so F is a strong conjugate base, thus making a basic/alkaline solution. I'm just confused on why this was emphasized (as in, what makes F not likely to be a weak base?). Is it because F...
Thu Dec 11, 2014 3:27 pm
Forum: Identifying Acidic & Basic Salts
Topic: Acidic,basic, and neutral aqueous solutions
Replies: 2
Views: 864

### Re: Acidic,basic, and neutral aqueous solutions

^ just as above, so, in this case the Al3+ is the ion acting as an acid; thus, making the solution acidic.

Other examples are in the course reader, such as: Fe3+, Cr3+, Fe2+, Cu2+, Ni2+ (and Mg2+ I believe)
Tue Dec 02, 2014 12:12 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: #6 Quiz 3 WKBK Prep
Replies: 2
Views: 471

### Re: #6 Quiz 3 WKBK Prep

Thank you so much!!
Mon Dec 01, 2014 8:04 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Video: Drawing Coordination Compounds
Replies: 8
Views: 1408

### Re: Video: Drawing Coordination Compounds

All right, thank you!!
Mon Dec 01, 2014 8:02 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Quiz 3 Prep #7, setting up ICE box
Replies: 5
Views: 1328

### Re: Quiz 3 Prep #7, setting up ICE box

The expression for the equilibrium constant would thus be:

(x)(6x)6 = Kp
(1-4x)4

Correct?
Mon Dec 01, 2014 7:54 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: #6 Quiz 3 WKBK Prep
Replies: 2
Views: 471

### #6 Quiz 3 WKBK Prep

Hey everyone! Can someone explain to me the changes in concentrations and how to know that in terms of changes in heat? Also, are we only going to be given questions where we predict or state conditions for the formation of concentrations? In #6 (below), I see that since the heat is positive, it is ...
Sun Nov 30, 2014 8:34 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Cubic Equations
Replies: 8
Views: 1387

### Re: Cubic Equations

Awesome, thank you!
Sun Nov 30, 2014 8:32 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Quiz 3 Prep, Fall 2012 #8
Replies: 6
Views: 793

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

All right! Thank you! I solved for it and got 0.1698 atm for HI, which is basically .17 atm. I looked at your work, where you probably got thrown off is when foiling and combining like terms, which is probably due to not including more numbers after the decimal point. For my final Quadratic equation...
Sun Nov 30, 2014 7:55 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Quiz 3 Preparation #8 atm^2 for Kp
Replies: 3
Views: 571

### Re: Quiz 3 Preparation #8 atm^2 for Kp

Okay, and atm being written with a power of 2 is the same as atm? And since atm 2 is saying the answer is in atm, there is no conversion regarding bar, yea? About the 1:1 rate ratio, you are referring to the change in composition for the I.C.E table, correct? As in what the stoichiometric coefficien...
Sun Nov 30, 2014 7:41 pm
Forum: Naming
Topic: Chloride for both Cl and Cl2
Replies: 2
Views: 770

### Re: Chloride for both Cl and Cl2

Awesome! Thank you, Eduardo!!
Sun Nov 30, 2014 7:07 pm
Forum: Naming
Topic: Chloride for both Cl and Cl2
Replies: 2
Views: 770

### Chloride for both Cl and Cl2

Hey! So do we call Cl and Cl 2 when outside the brackets chloride? Even though Cl 2 is called chlorine? I'm getting confused when it comes to writing a formula for a name that has chloride in it. Is chloride just an overarching name for any amount of Cl? So the number of Cl just depends on the oxida...
Sun Nov 30, 2014 6:21 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Quiz 3 Preparation #8 atm^2 for Kp
Replies: 3
Views: 571

### Quiz 3 Preparation #8 atm^2 for Kp

#8 Has the value of Kp at .11atm2
Since Kp is unitless, and there is a unit here, and there are no concentrations/partial pressures for the reactants or products, can this problem not be solved?

Thank you!
Sat Nov 29, 2014 3:49 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Quiz 3 Prep, Fall 2012 #8
Replies: 6
Views: 793

### Quiz 3 Prep, Fall 2012 #8

In #8, where we need to calculate the new partial pressure (in atom) of HI in the new equilibrium mixture when HI is halved, why is it that only the value of HI is affected by "Half the HI is removed from the container and equilibrium reestablished"? Why didn't the concentrations of the re...
Sat Nov 29, 2014 3:36 pm
Forum: Naming
Topic: Remembering polydentates
Replies: 4
Views: 647

### Re: Remembering polydentates

I'm having trouble making or finding a lewis structure for dien. How is it that the central N also has a lone pair?
Sat Nov 29, 2014 2:44 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Video: Drawing Coordination Compounds
Replies: 8
Views: 1408

### Re: Video: Drawing Coordination Compounds

Would we ever deal with lone pairs or only bonds?
What does it mena for a ligand to make multiple bonds when drawing it?

Do we always have to separate the Cl2 that were outside the brackets? (The Cl2 is still considered a part of the complex, correct?)
Sat Nov 29, 2014 2:12 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: 2012 Quiz 3 Number 4
Replies: 4
Views: 619

### Re: 2012 Quiz 3 Number 4

I'm pretty confused about drawing ligands. How do we know that N attaches, and not C? Does the Pt 2+ have any real significance then? In figuring this out, would we be drawing how it looks? Also, we assume that the other 4 bonds are being occupied by another compound, so the NH2CH2CH2NH2 would have ...
Fri Nov 28, 2014 9:31 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Cubic Equations
Replies: 8
Views: 1387

### Re: Cubic Equations

At what point can we assume a "cut-off" for Kc being so small it's insignificant to the change?

Like 10-#? What would that number be?

Thank you!
Fri Nov 28, 2014 9:23 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE box
Replies: 2
Views: 463

### Re: ICE box

I thought of it this way, just look at the molar ratio of the respective reactant to the product (since we are given the product at equilibrium, and the rest of the info given is initial), this leaves us with: 1N2:2NH3 which is 1/2. Since the reactants form the product, it is decreasing by half the ...
Fri Nov 28, 2014 6:30 pm
Forum: Naming
Topic: Remembering polydentates
Replies: 4
Views: 647

### Re: Remembering polydentates

So the number of sites a ligand can bond to are determined by number of lone pairs?
Fri Nov 28, 2014 6:28 pm
Forum: Naming
Topic: How to write structural formula order?
Replies: 5
Views: 816

### Re: How to write structural formula order?

Aren't neutral ligands before anionic ligands? Then the Transition metal?