Search found 27 matches

by rachelbuechler
Mon Feb 15, 2016 10:05 am
Forum: Administrative Questions and Class Announcements
Topic: Quiz 2 Winter 2016
Replies: 18
Views: 6992

QUIZ 2 WINTER 2016

In the workbook for the practice quiz, are there any questions that we should omit because they won't be covered on the actual quiz?
by rachelbuechler
Sun Feb 14, 2016 1:57 pm
Forum: First Order Reactions
Topic: textbook number 15.29??
Replies: 2
Views: 412

Re: textbook number 15.29??

thank you!!
by rachelbuechler
Sun Feb 14, 2016 1:56 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: What does k' mean?
Replies: 1
Views: 344

What does k' mean?

is it the reverse reaction or the forward reaction?
by rachelbuechler
Sun Feb 14, 2016 11:06 am
Forum: First Order Reactions
Topic: textbook number 15.29??
Replies: 2
Views: 412

textbook number 15.29??

Why do we calculate the concentration of A at 3 min by :

[A]t= [A]knot - (1molA/3 mol B) * [B]t ???

and then to determine the rate constant, why is the equation k= ln ([A]knot/[A]t)/t ...i thought it was ln([A]t/[Aknot]) instead?

Thanks
by rachelbuechler
Tue Feb 02, 2016 8:00 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Textbook #14.29 a!!!!
Replies: 1
Views: 211

Textbook #14.29 a!!!!

In this problem they give you:

(a) Co 2+/Co and Ti 3+/Ti 2+

When you're writing the cell diagram, how do you know what the phases of each substance are since they don't give them to you in the problem?
by rachelbuechler
Mon Feb 01, 2016 4:39 pm
Forum: Balancing Redox Reactions
Topic: Ch. 14 #14.3a
Replies: 1
Views: 282

Ch. 14 #14.3a

I'm confused as to why you multiply the reduction half rxn by 4? 4[Cl2 (g) + 2e- --> 2 Cl- (aq)] 1[S2O3 2- (aq) + 5H20(l) --> 2SO4 2-(aq) + 10H+(aq) + 8 e-] if you're supposed to have an equal number of electrons for both half reactions, aren't the amounts already equal without multiplying the first...
by rachelbuechler
Sun Jan 31, 2016 4:57 pm
Forum: Balancing Redox Reactions
Topic: Midterm material?
Replies: 1
Views: 318

Midterm material?

Up to what material will the midterm cover?
by rachelbuechler
Sun Jan 31, 2016 3:20 pm
Forum: Balancing Redox Reactions
Topic: Textbook example p. 567
Replies: 1
Views: 258

Textbook example p. 567

An example of balancing a redox equation in basic solution says in step #5: (p. 568) Balance charge by adding electrons it says: net charge on the left is -7 and on the right it is -1; 6 electrons are needed on the right to lower the net charge from -1 to -7. Br- +6OH- --> BrO3- +3H20 + 6 e- I was w...
by rachelbuechler
Sun Jan 31, 2016 2:57 pm
Forum: Balancing Redox Reactions
Topic: How do you know the Oxidation number??
Replies: 1
Views: 2011

How do you know the Oxidation number??

For example, in the book on page 564 it's balancing a redox equation in acidic solution, and the equation is: MnO4- (aq)+ H2C2O4(aq)--> Mn2+(aq) + CO2(g) and it says identify species being reduced: MnO4- --> Mn2+ and it says the oxidation number of Mn decreases from +7 to +2, so the Mn in the MNO4- ...
by rachelbuechler
Tue Jan 19, 2016 2:11 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy equations?
Replies: 1
Views: 257

Enthalpy equations?

What are the main equations for Delta H that we'll use when we have to solve for enthalpy?
by rachelbuechler
Tue Jan 19, 2016 10:10 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Change in internal energy under constant temperature
Replies: 1
Views: 209

Change in internal energy under constant temperature

If a system has a constant temperature and you're trying to calculate the change in internal energy, do you ALWAYS use the equation:

Delta U= 3/2*k*T ???

THanks!
by rachelbuechler
Mon Jan 18, 2016 10:07 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Ch. 9 #15
Replies: 3
Views: 1039

Re: Ch. 9 #15

Thank you!!
by rachelbuechler
Mon Jan 18, 2016 8:25 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: S=kB*lnw equation
Replies: 1
Views: 350

S=kB*lnw equation

Is Kb a given value? How do we find it?
by rachelbuechler
Mon Jan 18, 2016 6:35 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Cv and Cp for monatomic ideal gas
Replies: 1
Views: 366

Cv and Cp for monatomic ideal gas

How do we know the Cv for a monatomic ideal gas and the Cp for a monatomic ideal gas? Is that just something we memorize?
by rachelbuechler
Mon Jan 18, 2016 6:30 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Ch. 9 #15
Replies: 3
Views: 1039

Ch. 9 #15

the problem says: Use data in table 8.3 or appendix 2A to calculate the entropy change for (a) the freezing of 1 mol H20(l) at 0.00 degrees celsius; (b) the vaporization of 50 g of ethanol, C2H5OH, at 351.5 K. The answer key says you use the equation q/T=Standard change in enthalpy/T= 1.00 mol x(-6....
by rachelbuechler
Sun Jan 17, 2016 1:00 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: quiz??
Replies: 3
Views: 573

quiz??

What chapters will the quiz cover?
by rachelbuechler
Sat Jan 16, 2016 3:19 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Question 8.55-->Hess's law
Replies: 1
Views: 334

Question 8.55-->Hess's law

Can someone go through how you add them up and cancel out things because i'm getting confused. They give you 2Ba(s)+O2(g)-->2BaO(s) standard enthalpy of formation= -1107kj 2Al(s) +O2(g)-->Al2O3(s) standard enthalpy of formation= -1676kj and then you're supposed to calculate the reaction enthalpy for...
by rachelbuechler
Sat Jan 16, 2016 2:43 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Ch. 8 #39
Replies: 4
Views: 601

Re: Ch. 8 #39

thank you! Where is the equation sheet?
by rachelbuechler
Sat Jan 16, 2016 1:57 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Ch. 8 #39
Replies: 4
Views: 601

Ch. 8 #39

How much heat is needed to convert 80 g of ice at 0.0 degrees celsius into liquid water at 20 degrees celsius? (see tables 8.2 and 8.3) in the answer key it says the process is composed of two steps: melting the ice at 0 degrees celsius and then raising the temperature of the liquid water from 0 deg...
by rachelbuechler
Fri Jan 08, 2016 4:35 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Table of Bond Enthalpies
Replies: 1
Views: 276

Table of Bond Enthalpies

Where do we find the table of bond enthalpies? And will we always be given them?
by rachelbuechler
Sun Nov 15, 2015 8:02 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Quiz 3 2014 preparation #7
Replies: 2
Views: 392

Quiz 3 2014 preparation #7

/var/folders/p1/2cbhw5kj46735pgnv6ssq9kc0000gn/T/com.apple.iChat/Messages/Transfers/IMG_4145.JPG for the reaction NH4Hs (s) <---> NH3 + H2S (g) and the initial concentration of PCL3 is 1.0 M and x is the equilibrium concentration of P4, what is the expression for the equilibrium constant? I'm confus...
by rachelbuechler
Sat Nov 14, 2015 10:13 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Calculating the equilibrium composition, course reader ex
Replies: 1
Views: 321

Calculating the equilibrium composition, course reader ex

In the first example in the course reader it says you mix 0.500 mol/L N2 with 0.800mol/L H2. Also given: at equilibrium there is 0.150 mol/L NH3. What is K?

The change in molar concentration for N2 is 0.075, and 0.225 for H2.
I'm confused as to how you find the change in molar concentration.
by rachelbuechler
Mon Nov 02, 2015 11:09 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: When Z greater than or equal to 8 and Z<8 clarification
Replies: 1
Views: 806

Re: When Z greater than or equal to 8 and Z<8 clarification

Z is the atomic number, and the nuclear charge is equal to the atomic number. for z<8, the sigma bond is above the pi bond. For z>8, the sigma bond is below the the pi bond. If you have a heteronuclear molecule, such as CO, sigma is always higher than the pi bond.

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