## Search found 20 matches

Sat Mar 12, 2016 11:22 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Winter Final Exam 2013 4A
Replies: 4
Views: 766

### Re: Winter Final Exam 2013 4A

The oxidation state of 2Fe(s) is 0. The oxidation state of Fe in 2Fe(OH)2 is +4, so 4 electrons are being transferred.
Sat Mar 12, 2016 9:13 am
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: Residual Entropy
Replies: 1
Views: 366

### Residual Entropy

Could someone please explain how to find degeneracy in the equation S=kB lnW?
Thu Mar 10, 2016 7:18 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Equations for E
Replies: 1
Views: 333

### Equations for E

Is there a difference between the two equations for E? (One that uses ln: E = E° - (RT/nF)lnQ and one that uses log: E = E° - (.05916 V/n)logQ). I get similar answers when using each of them but they are still off by a bit, does it matter when we use one equation or the other?
Sun Feb 28, 2016 4:38 pm
Forum: *Constitutional and Geometric Isomers (cis, Z and trans, E)
Topic: Priority of Atoms in Geometric Isomers
Replies: 3
Views: 615

### Re: Priority of Atoms in Geometric Isomers

The priority is based on the atomic number of the atom bound to the sp2 carbon atom, so the double bond.
Highest I>Br>Cl>SH>OH>NH2>CH3>H Lowest
If two atoms are the same, look at the next set of bound atoms
-CH2-Cl> -Ch2-OH > -CH2-NH2 > -CH2-CH3 > -CH2-H
Sun Feb 14, 2016 1:01 pm
Forum: General Rate Laws
Topic: half life
Replies: 1
Views: 384

### half life

For the first order reaction cyclobutane(g)--> 2ethylene(g) at 800 K, the half-life is 0.43 seconds. Calculate the time needed for the concentration of cyclobutane to fall to 1/64 of its initial value.
Wed Feb 10, 2016 10:11 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Midterm 2012 Q7B
Replies: 1
Views: 322

### Midterm 2012 Q7B

Determine the equilibrium constant for the reaction: Mn(s)+Ti2+->Mn2+(aq) + Ti(s)
In the solutions it gives the half reactions as Ti2+(aq) + 2e- -> Ti (s) E(cathode)=-1.63 V and Mn2+(aq) + 2e- -> Mn(s) E(anode)= -1.18 V. Why is the half reaction for the anode not reversed?
Tue Feb 09, 2016 8:06 pm
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: W for BH2F
Replies: 3
Views: 1758

### Re: W for BH2F

In the equation S=kB*ln(W), I understand how to find the degeneracy, but where does the kB value come from?
Sun Jan 24, 2016 2:15 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond enthalpies
Replies: 3
Views: 494

### Re: Bond enthalpies

How do you calculate the reaction enthalpy then? I understand the concept I just don't know how to do the calculations and figure out which bonds are breaking.
Sun Jan 24, 2016 10:59 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond enthalpies
Replies: 3
Views: 494

### Bond enthalpies

This is question 3 in the Winter 2014 quiz 1 preparation. For the reaction C4H10 + O2 --> CO2 + H20, how do you find the reaction enthalpy? The bond enthalpies given are: C-H 412 kJ/mol, C-C 348 kJ/mol, O=O 496 kJ/mol, C=O 743 kJ/mol, O-H 463 kJ/mol. I know that you add up the bonds that are broken ...
Sat Dec 05, 2015 1:51 pm
Forum: Ideal Gases
Topic: Decomposition reaction
Replies: 1
Views: 718

### Decomposition reaction

Question Q6B on Fall 2012 final
The equilibrium constant, Kc, equals 0.045 at 250 C for the composition reaction: PCl5-->PCl3+Cl2. Calculate the percentage of PCl5 that dissociates if 0.05 mole of PCl5 is placed in a closed vessel (constant volume) at 250 C and 2.00 atm pressure.
Thu Dec 03, 2015 11:18 pm
Forum: *Titrations & Titration Calculations
Topic: 12.23
Replies: 11
Views: 1958

### Re: 12.23

This is what I did to find the final pH, which is what he did above. You know that the base has been completely diluted with the acid that was added, so therefore the pH is based only on HCl. To find the pH you use pH=-log[H30+], so pH=-log(0.05)=2.30, which is the final pH.
Tue Nov 24, 2015 10:48 am
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Equilibrium constant
Replies: 1
Views: 487

### Equilibrium constant

How do you find the equilibrium constant using the acidity constant and basicity constant? For example in question 12.117: Write the equilibrium constant for the following reaction and calculate the value of K at 298 K for the reaction HNO2+NH3-> NH4+NO2 using the data in tables 12.1 and 12.2. In th...
Mon Nov 23, 2015 10:37 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Determining pH
Replies: 3
Views: 704

### Determining pH

Rank the following solutions in order of increasing pH: a) 1.0x10^-5 M HCl, b) 0.20 M CH3NH3Cl(aq), c) 0.20 M CH3COOH(aq), d) 0.20 M C6H5NH2
Sun Nov 22, 2015 7:38 pm
Forum: Lewis Acids & Bases
Topic: Conjugate base
Replies: 2
Views: 1728

### Re: Conjugate base

HF(pKa=3.45) Conjugate base: F- (pKb=14-3.45=10.55) CH3COOH(pKa=4.75) Conjugate base: CH3CO2 (pKb=14-4.75=9.25) HClO(pkA=7.53) Conjugate base: ClO (pKb=14-7.53=6.47) HIO(pKa=10.64) Conjugate base: I- (pKb=14-10.64= 3.36) HCOOH(pKa=3.75) Conjugate base: HCO2 (pKb=14-3.75=10.25) In this example, the o...
Thu Nov 12, 2015 8:19 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: chemical equilibrium question
Replies: 1
Views: 441

### chemical equilibrium question

Bromine chloride, bromine, and chlorine gases have reached equilibrium in a container at 500 K according to the reaction, 2BrCl(g)-->Br2(g)+Cl2(g). Equilibrium partial pressures are 1.08 bar BrCl, 4.9 Br2, and 7.6 bar Cl2. Half the BrCl is removed from the container and equilibrium is reestablished....
Tue Nov 03, 2015 9:58 pm
Forum: DeBroglie Equation
Topic: de Broglie wavelength
Replies: 2
Views: 512

### de Broglie wavelength

Question 4 from the fall 2013 midterm: During spontaneous fission uranium-235 emits a neutron with a mass of approximately 1.00866 g/mol. If one of these neutrons has an energy of 4.84 MeV, what is its de Broglie wavelength? I'm confused on what the 1.00866 g/mol is used for, is it to find the mass ...
Sat Oct 31, 2015 6:05 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Lewis structure of SO2Cl2
Replies: 1
Views: 4906

### Lewis structure of SO2Cl2

In question 31 from the homework, it asks for the Lewis structure of SO2Cl2. I drew it with S as the central atom, with double bonds on the oxygens and single bonds on the chlorines, however in the solutions manual they are all single bonds. Wouldn't it be a more stable atom if the oxygens had doubl...
Sun Oct 25, 2015 9:50 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: homework question
Replies: 1
Views: 422

### homework question

Just as AlCl3 forms dimers, in the [Bi2Cl4]2- ion two of the Cl atoms form "bridges" between the two Bi atoms. Propose a structure for the [Bi2Cl4]2- ion.
Sun Oct 18, 2015 1:39 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron configuration
Replies: 2
Views: 711

### Electron configuration

Why is the electron configuration for Ag [Kr] 4d10 5s1? I thought that the 5s subshell filled up first so why isn't it [Kr] 4d9 5s2?
Fri Oct 09, 2015 10:32 pm
Forum: Limiting Reactant Calculations
Topic: Combustion analysis
Replies: 1
Views: 1444

### Combustion analysis

Question M5 Polychlorinated biphenyls (PCBs) were once widely used industrial chemicals but were found to pose a risk to health and the environment. PCBs contain only carbon, hydrogen, and chlorine. Aroclor 1254 is the trade name for a PCB with molar mass 360.88 g/mol. Combustion of 1.52 g of Aroclo...