Search found 22 matches

by Helen T 2G
Sat Mar 12, 2016 4:04 pm
Forum: *Cyclohexanes (Chair, Boat, Geometric Isomers)
Topic: Specificity of Hydrogen Bonds When Drawing Conformations
Replies: 1
Views: 320

Specificity of Hydrogen Bonds When Drawing Conformations

When asked to draw conformations, does the C-H bond have to be bent at an certain angle (such as away from other H atoms)? Or is does the bond angle not matter too much as long as it is drawn in?
by Helen T 2G
Sat Mar 12, 2016 1:25 pm
Forum: *Cyclohexanes (Chair, Boat, Geometric Isomers)
Topic: Cis and Trans Isomers?
Replies: 3
Views: 469

Re: Cis and Trans Isomers?

zhajee wrote:Molecules with triple bonds cannot have cis and trans isomers right? Since the molecule becomes linear it cannot have different arrangements of groups around the bond?


That is correct. Carbon atoms with triple bonds are sp hybridized, thereby limiting the final "shape" to be linear.
by Helen T 2G
Tue Mar 01, 2016 7:17 pm
Forum: *Nucleophiles
Topic: Carboanions/carbocations valence electrons
Replies: 1
Views: 400

Carboanions/carbocations valence electrons

Why do carboanions have 8 valence electrons while carbocations have 6 valence electrons?
by Helen T 2G
Wed Feb 10, 2016 12:03 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: ΔS of reversible vs. irreversible process
Replies: 1
Views: 340

ΔS of reversible vs. irreversible process

Why is the ΔS of both a reversible and irreversible process the same?
by Helen T 2G
Tue Feb 09, 2016 11:12 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: E°cell = 0.00V
Replies: 1
Views: 371

E°cell = 0.00V

In what conditions is E°cell=0.00V?
by Helen T 2G
Tue Feb 09, 2016 11:02 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Dominance of Positional vs. Thermal Disorder
Replies: 1
Views: 412

Dominance of Positional vs. Thermal Disorder

How can you tell whether the entropy change is primarily a result of changes in positional disorder rather than the thermal disorder (and vice versa)?
by Helen T 2G
Tue Feb 09, 2016 9:46 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Favorable vs. Spontaneous
Replies: 2
Views: 1284

Favorable vs. Spontaneous

Favorable and spontaneous are not synonymous right? I know that when ΔH = - it is favorable and when ΔS = + it is favorable, but that individually that does not designate spontaneity correct? BOTH ΔH & ΔS must be considered in order to determine spontaneity?
by Helen T 2G
Wed Jan 27, 2016 4:28 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Isothermal Processes
Replies: 4
Views: 601

Re: Isothermal Processes

how about for an isolated system? ex) If an isolated system contained +5 kJ of energy, after 100 years deltaU=? why will deltaU eventually reach 0. is it because the system uses those +5kJ of energy for work within the system itself? For an isolated system, delta U is always equal to 0 because no h...
by Helen T 2G
Tue Jan 26, 2016 5:39 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: ΔS=- ΔH=-
Replies: 1
Views: 317

ΔS=- ΔH=-

Why is the reaction spontaneous at low temperatures if ΔS=- ΔH=-?
by Helen T 2G
Tue Jan 26, 2016 4:32 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: ΔU at constant volume
Replies: 1
Views: 356

ΔU at constant volume

If Δv = 0, why is ΔU = qv? Is it because that means no work is done? In addition, why does a reaction occurring at constant pressure have a separate equation of ΔU = ΔH - PΔV?
by Helen T 2G
Tue Jan 19, 2016 10:13 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Error in S vs. Error in w
Replies: 1
Views: 262

Error in S vs. Error in w

Hello, why does entropy (S) have a small error while degeneracy (w) has a large error in the Boltzmann equation?
by Helen T 2G
Sun Jan 10, 2016 11:45 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Units
Replies: 3
Views: 497

Re: Units

Does the molar heat capacity always have units of J and K^-1 instead of kJ and C^-1? Or is it based on the preference of the user? Which units are preferred?
by Helen T 2G
Sat Dec 05, 2015 11:58 pm
Forum: *Titrations & Titration Calculations
Topic: Fall Final 2010 Question 7F
Replies: 4
Views: 596

Re: Fall Final 2010 Question 7F

Suppose that 25.0 mL of 0.10M CH3COOH(aq) (Ka = 1.8 x 1-^-5) is titrated with 0.10 M NaOH (aq).
F) Calculate the pH at the stoichiometric point.
I do not understand why NaCH3CO2 has a concentration of 0.050M.

Sorry about my lack of information provided in the previous post! Thank you for your help.
by Helen T 2G
Sat Dec 05, 2015 11:51 pm
Forum: *Titrations & Titration Calculations
Topic: Fall Final 2010 Question 7F
Replies: 4
Views: 596

Fall Final 2010 Question 7F

Hello, in Fall Final 2010 Question 7F, where did the 0.050 M of NaCH3CO2 come from?
by Helen T 2G
Mon Nov 02, 2015 6:33 am
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Ionic Character and Strength of Bonds
Replies: 4
Views: 2057

Re: Ionic Character and Strength of Bonds

If ionic bonds are stronger, why are they more soluble in water?
by Helen T 2G
Mon Nov 02, 2015 5:41 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Determining Valence Electrons from Electron Configuration
Replies: 1
Views: 572

Determining Valence Electrons from Electron Configuration

In the example of Scandium, Sc, the electron configuration is [Ar]3d14s2. Are the valence electrons in this case 3d1 and 4s2 or is it only 4s2? To reach the ground state configuration, the electrons would be removed from 4s2 correct?
by Helen T 2G
Mon Nov 02, 2015 5:05 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Distinguishing Final vs. Initial While Using Rydberg Eqn
Replies: 1
Views: 818

Distinguishing Final vs. Initial While Using Rydberg Eqn

I still am a little confused on which energy would be considered the final and which would be the initial when calculating the change in energy for an electron ( delta E = E(final) - E(initial) ). Typically if the problem says light is emitted, does that mean the transition is from a higher to a low...
by Helen T 2G
Tue Oct 27, 2015 9:32 pm
Forum: NEWS & RESOURCES
Topic: Electron Configuration of Bonded Atom
Replies: 2
Views: 1919

Electron Configuration of Bonded Atom

I know how to write the electron configuration of a single atom, but how do your write the electron configuration of a molecule?
by Helen T 2G
Sun Oct 11, 2015 4:22 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Rydberg Equation & Different Series
Replies: 1
Views: 572

Rydberg Equation & Different Series

Can the Rydberg Equation only be used for levels within one specific series such as Balmer or Lyman? I have this question because for question 1.57, n-sub1 = 2 because the problem was specifically discussing lines of the Balmer series. There would never be a question asking to find the energy change...
by Helen T 2G
Thu Oct 08, 2015 11:05 pm
Forum: Properties of Light
Topic: Electromagnetic Radiation and Electrical Field
Replies: 1
Views: 307

Electromagnetic Radiation and Electrical Field

I am not too clear what exactly is the electrical field. When the frequency of the electromagnetic radiation decreases, why does the electrical field at a given point also decrease?
by Helen T 2G
Fri Oct 02, 2015 2:43 pm
Forum: Empirical & Molecular Formulas
Topic: L35
Replies: 3
Views: 1922

Re: L35

First, you must convert the 2.50 t of NaBr to grams using the conversion factor 1.0 x 10^6 grams = 1 ton. Then you find the molar mass of NaBr (102.89g) and divide the grams of NaBr by NaBr's molar mass. Next, find the mole ratio between Fe and NaBr which is 3 mol Fe: 8 mol NaBr (don't forget to mak...

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