## Search found 44 matches

Wed Feb 25, 2015 9:34 am
Forum: First Order Reactions
Topic: 1st Order RXN calculation when given conc C
Replies: 2
Views: 553

### Re: 1st Order RXN calculation when given conc C

Thank you!
Wed Feb 25, 2015 9:34 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Quiz 1, Winter 2014 Solving for Activation Energy
Replies: 4
Views: 4053

### Re: Quiz 1, Winter 2014 Solving for Activation Energy

Thank you so much!
Mon Feb 23, 2015 5:35 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Quiz 1, Winter 2014 Solving for Activation Energy
Replies: 4
Views: 4053

### Quiz 1, Winter 2014 Solving for Activation Energy

For the reaction, HO + H2 --> H2O + H, a plot of lnk versus 1/T gives a straight line with a slope equal to -5.1x10^3 K What is the activation energy for this reaction? from the Arrhenius EQ, I found that Ea= lnK- lnA/ -RT However, I don't know how to find the values of lnK, lnA, and T? I realize th...
Mon Feb 23, 2015 12:28 pm
Forum: First Order Reactions
Topic: 1st Order RXN calculation when given conc C
Replies: 2
Views: 553

### 1st Order RXN calculation when given conc C

For Quiz Prep 2013 #6,

First order reaction of 2A--> B + 3C +D
What is the rate constant if the concentration of C is 0.40 M after 4.0 min and the initial concentration of A is 0.50 M?

How do we solve for k when given the concentration of C instead of A?
Thu Feb 19, 2015 10:49 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Determining initial rate of decamp of N2O5
Replies: 1
Views: 407

### Determining initial rate of decamp of N2O5

14.11

2N2O5--> 4NO2 + O2

3.45 g N2O5 , 0.750 L

When solving for the concentration of N2O5, I understand that you multiply the molar mass of N2O5 and then divide by the liters given, but why wouldn't you multiply by 2 from the balanced EQ?
Tue Feb 10, 2015 8:12 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Writing a cell diagram, electrodes
Replies: 7
Views: 4364

### Re: Writing a cell diagram, electrodes

Thank you so much! Would there be a time when you don't need to place the Pt in the equation? If there is, how do you know?
Mon Feb 09, 2015 1:38 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Writing a cell diagram, electrodes
Replies: 7
Views: 4364

### Writing a cell diagram, electrodes

A galvanic cell

Zn + 2NO3(-) + 4H(+) --> 2NO2 + 2H20 + Zn(2+)

The cell diagram is:

Zn| Zn2+ || NO3- , H+ | NO2 | Pt (s)

How do you know where to put the electrode Platinum?
Also, why is the H+ included but not the water?

Thanks!
Mon Feb 09, 2015 1:34 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Benzene or Hexane-- molar entropy
Replies: 2
Views: 1805

### Re: Benzene or Hexane-- molar entropy

Thank you! Would this also have to do with the fact that benzene is in a ring structure, while hexane is not?
Mon Feb 09, 2015 12:34 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Benzene or Hexane-- molar entropy
Replies: 2
Views: 1805

### Benzene or Hexane-- molar entropy

How do we know that hexane has a higher molar entropy value at 25C than benzene?

Thank you!
Fri Feb 06, 2015 2:37 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 13.9 b, the n in Gibbs free energy
Replies: 1
Views: 299

### 13.9 b, the n in Gibbs free energy

Hello, For the equation 6Fe(3+) +3Cr(3+) +7H20 --> 6Fe(2+) +Cr2O7(2-) + 14H(+) How do you break this equation up into 1/2 reactions? Is this how you find out the n in the equation -nFE, by calculating the electrons added? (Please correct me if I'm wrong) Also, wouldn't the electrons added be differe...
Fri Feb 06, 2015 2:00 pm
Forum: Balancing Redox Reactions
Topic: 13.3 b Reducing/Oxidizing Agent
Replies: 2
Views: 584

### 13.3 b Reducing/Oxidizing Agent

For the reaction MnO4- +H2SO3 --> Mn2+ +HSO4- the solutions manual says that MnO4- is the oxidizing agent and H2SO3 is the reducing agent. Why is this? I realize that the oxidizing agent is the one being reduced, and the reducing agent is the one being oxidized, and that oxidation is the loss of ele...
Wed Feb 04, 2015 4:05 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Q2 Winter 2007 Midterm molecular weight and calorimeters
Replies: 1
Views: 336

### Q2 Winter 2007 Midterm molecular weight and calorimeters

Hello, enthalpy of combustion of benzoic acid=> -3227 kJ.mol-1 1.453g benzoic acid burned in calorimeter, temp increased by 2.265 C This question asks to calculate the heat capacity of the calorimeter. I understand that the formula to do so would be C=q/deltaT because we don't take into account/ kno...
Mon Feb 02, 2015 2:43 pm
Forum: Balancing Redox Reactions
Topic: 13.3 a Multiplying by appropriate factors
Replies: 3
Views: 724

### 13.3 a Multiplying by appropriate factors

For 13.3 , The solutions manual says to multiply the oxidation and reduction half-reactions by appropriate factors that will result in the same # of electrons in both half reactions. I guess I'm just kind of confused with how to do this/ why you have to do this?

Thanks for the help!
Sat Jan 24, 2015 5:00 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond Enthalpies, Formation of Benzene
Replies: 1
Views: 367

### Bond Enthalpies, Formation of Benzene

For 7.81,(3C2H2 --> C6H6) I subtracted 3 C double bonds + 3 C single bonds + 6 C-H bonds from 3 double C bonds + 6 C-H bonds. However, in the solutions manual, the C-H bonds do not come into play when calculating the bond enthalpies, only the C double bonds do. I don't understand why that is? Thanks!
Wed Dec 10, 2014 11:18 pm
Forum: *Making Buffers & Calculating Buffer pH (Henderson-Hasselbalch Equation)
Topic: values of Ka and Kb
Replies: 1
Views: 351

### values of Ka and Kb

When we are setting up ICE charts, etc. I noticed in the solutions manual that the value of Ka is given...unless it's a problem where we are specifically solving for Ka, is Ka something that is going to be given to us to solve the problem? Or is there a way to calculate it?

Thank you!
Wed Dec 10, 2014 10:46 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Memorize
Replies: 4
Views: 635

### Re: Memorize

My TA said that we should be able to recognize the 7 strong acids and bases, that way it's easy to identify the weak ones...so I'm guessing we might need to know the formulas then?
Tue Dec 09, 2014 10:58 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: HW 11.33
Replies: 4
Views: 656

### Re: HW 11.33

Thank you, John!
Tue Dec 09, 2014 10:57 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: calculating pOH
Replies: 4
Views: 600

### Re: calculating pOH

Thank you so much!
Tue Dec 09, 2014 10:38 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: HW 11.33
Replies: 4
Views: 656

### Re: HW 11.33

Why is the unit for volume in mL for these problems? Is it better to keep it in mL instead of L?
Tue Dec 09, 2014 10:20 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: calculating pOH
Replies: 4
Views: 600

### Re: calculating pOH

Ohh...is pH+pOH=14 just a general rule...and if so, why?

Thank you so much!
Tue Dec 09, 2014 8:21 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: calculating pOH
Replies: 4
Views: 600

### calculating pOH

Hi! In 11.33, it asks to calculate the pH and pOH for each aqueous solutions of strong acid or base

ie in part a) 0.0146 M HNO3

I found the pH to be 1.84, however how do you calculate pOH?
I understand that it's the -log[OH-] but I'm not sure how to do that?
Thank you!
Tue Dec 09, 2014 11:29 am
Forum: Determining Molecular Shape (VSEPR)
Topic: When can Cl be an acceptable central atom?
Replies: 2
Views: 1527

### When can Cl be an acceptable central atom?

In drawing the shape of the ClO2- ion, Cl is drawn in the middle, and I was just wondering when is that acceptable?
Tue Dec 09, 2014 11:28 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Lewis structures that obey the octet rule
Replies: 3
Views: 1293

### Lewis structures that obey the octet rule

Hi! When a problem tells you to "use only Lewis structures that obey the octet rule," what does this mean? And also, does this mean no double bonds?
Tue Dec 09, 2014 11:22 am
Forum: Empirical & Molecular Formulas
Topic: Converting from moles of H20 to moles of H, Fall 2009 Exam
Replies: 2
Views: 411

### Re: Converting from moles of H20 to moles of H, Fall 2009 Ex

Ohhh my goodness! Thank you! :)
Mon Dec 08, 2014 11:22 pm
Forum: Empirical & Molecular Formulas
Topic: Converting from moles of H20 to moles of H, Fall 2009 Exam
Replies: 2
Views: 411

### Converting from moles of H20 to moles of H, Fall 2009 Exam

Q1C An industrial by-product consists of C, H, O, and Cl. When 0.100g of the compound was analyzed by combustion analysis, 0.0682 g of CO2 and 0.0140g of H20 were produced. The mass percentage of Cl i the compound was found to be 55.0%. The molar mass of the compound is 64.47 g.mol-1. Find the EF/MF...
Mon Dec 01, 2014 4:07 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Quiz 3 Prep #7, setting up ICE box
Replies: 5
Views: 1138

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

Problem: For the following reaction, if the initial concentration of PCl3 (g) is 1.0M and x is the equilibrium concentration of P4 (g), what is the expression for the equilibrium constant? PCl3 <--> P4 + Cl2 I balanced the equation... 4PCl3 <--> P4 + 6Cl2 In setting up my ICE box, I realize that the...
Mon Nov 17, 2014 2:47 pm
Forum: Naming
Topic: H2O vs OH2
Replies: 2
Views: 2924

### H2O vs OH2

When writing the formula for the coordination compounds, does it matter if we write H2O versus OH2?
Mon Nov 17, 2014 2:44 pm
Forum: Naming
Topic: 16.29 part c
Replies: 1
Views: 264

### 16.29 part c

The coordination compound given is: tetraammineaquacobalt (III) bromide

I was checking my answer in the solution manual, and this is what was given:
[Co (NH3)4 (H2O)2] Br3

Why are there 2 H2Os? And how do you know that the subscript for bromine is 3?
Tue Nov 04, 2014 10:39 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 3.1 Must/May/Cannot have LP on Central Atom
Replies: 3
Views: 479

### Re: 3.1 Must/May/Cannot have LP on Central Atom

Thank you both so much!
Mon Nov 03, 2014 2:07 pm
Forum: Lewis Structures
Topic: 2 #101 Ground State v Excited State
Replies: 2
Views: 426

### Re: 2 #101 Ground State v Excited State

Ohhh! Thank you so much, Patrick!
Mon Nov 03, 2014 2:02 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 3.1 Must/May/Cannot have LP on Central Atom
Replies: 3
Views: 479

### 3.1 Must/May/Cannot have LP on Central Atom

How do you know if a central atom must, may or cannot have LP of electrons based on its molecular shape?
Mon Nov 03, 2014 1:30 pm
Forum: Resonance Structures
Topic: O3 vs O2, why is there only one observed bond length?
Replies: 3
Views: 2310

### Re: O3 vs O2, why is there only one observed bond length?

Why can't 03 have two double bonds?
Mon Nov 03, 2014 1:13 pm
Forum: Bond Lengths & Energies
Topic: Chapter 2, #83
Replies: 3
Views: 3382

### Re: Chapter 2, #83

Thank you so much Karina!
If the CO were to have a triple bond, where would the lone pairs of electrons be placed?
Mon Nov 03, 2014 1:09 pm
Forum: Lewis Structures
Topic: 2 #101 Ground State v Excited State
Replies: 2
Views: 426

### 2 #101 Ground State v Excited State

How do I tell by an element's electron configuration whether it is in the ground state or excited state? Sorry, super basic question, but it came up in the homework for chapter 2.. (2.101)
Sun Nov 02, 2014 3:24 pm
Forum: Electronegativity
Topic: Ionic Character
Replies: 5
Views: 2908

### Re: Ionic Character

Thank you!
Sun Nov 02, 2014 3:19 pm
Forum: Bond Lengths & Energies
Topic: Chapter 2, #83
Replies: 3
Views: 3382

### Chapter 2, #83

Place the following in order of decreasing bond length
the CO bond in CO, CO2, and CO3 (2-)

I drew Lewis dot structures for these, but I don't know how to determine the bond length of them? Thank you!
Sun Nov 02, 2014 2:42 pm
Forum: Electronegativity
Topic: Ionic Character
Replies: 5
Views: 2908

### Re: Ionic Character

If we don't have a table of electronegativity, though, how would we figure this problem out?
Tue Oct 21, 2014 12:48 pm
Forum: DeBroglie Equation
Topic: Calculating velocity when given De Broglie wavelength
Replies: 1
Views: 7917

### Calculating velocity when given De Broglie wavelength

At what velocity is an electron moving if it has a de Broglie wavelength of 7.0 × 10-11 m?

I'm not quite sure how to manipulate the equation to solve for velocity?
Tue Oct 21, 2014 11:08 am
Forum: Molarity, Solutions, Dilutions
Topic: Fall 2012 Quiz 1 Preparation, #10
Replies: 4
Views: 716

### Re: Fall 2012 Quiz 1 Preparation, #10

Thank you so much! I forgot to see which reactant would be the limiting reagent!
Tue Oct 21, 2014 11:06 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Quiz 1 Preparation #3, Question 10
Replies: 4
Views: 591

### Re: Quiz 1 Preparation #3, Question 10

Thank you so much!
Tue Oct 21, 2014 9:46 am
Forum: Photoelectric Effect
Topic: Solving for Frequency
Replies: 1
Views: 274

### Solving for Frequency

In a photoelectric effect problem, how do I solve for frequency when the velocity and work function are given?
Mon Oct 20, 2014 1:53 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Quiz 1 Preparation #3, Question 10
Replies: 4
Views: 591

### Quiz 1 Preparation #3, Question 10

An excited hydrogen atom emits light with a frequency of 1.14 x 10^14 Hz to reach the energy level for which n=4. In what principle quantum level did the electron begin?

What are the steps to use in order to solve this problem?
Mon Oct 20, 2014 1:10 pm
Forum: Molarity, Solutions, Dilutions
Topic: Fall 2012 Quiz 1 Preparation, #10
Replies: 4
Views: 716

### Fall 2012 Quiz 1 Preparation, #10

You start with 0.55M CaCl2 in 60 mL and 0.22 M AgNO3 M in 125 mL. What is the resulting mass of AgCl(s)?

How do you approach this problem and solve it?
Mon Oct 20, 2014 1:08 pm
Forum: Photoelectric Effect
Topic: Fall 2012 Quiz 1 Preparation, #10
Replies: 1
Views: 302

### Fall 2012 Quiz 1 Preparation, #10

You start with 0.55M CaCl2 in 60 mL and 0.22 M AgNO3 M in 125 mL. What is the resulting mass of AgCl(s)?

How do you approach this problem and solve it?