## Search found 48 matches

Sat Mar 16, 2019 11:58 pm
Forum: Balancing Redox Reactions
Topic: calculating standard cell potential
Replies: 5
Views: 332

### calculating standard cell potential

Why is standard cell potential sometimes equal to the difference between the standard potentials of the two electrodes and sometimes its the sum of the standard potentials of the cathode and the anodes?
Sat Mar 16, 2019 9:57 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: fast/slow step and reaction constant
Replies: 1
Views: 319

### fast/slow step and reaction constant

Are fast and slow steps directly related to the reaction constant? As in large reaction constants are indicative of a fast step and small reaction constants are indicative of slow steps?
Sat Mar 16, 2019 9:03 pm
Forum: Balancing Redox Reactions
Topic: 6.73 7th Edition
Replies: 1
Views: 285

### 6.73 7th Edition

I don't completely understand what the chemical reaction for this problem would be. The solutions manual seems to use (unbalanced) Al + O2 --> AL (OH)3. Is OH the product because a given condition is that the reaction is in basic solution?
Sat Mar 16, 2019 8:12 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 6.63 7th Edition
Replies: 1
Views: 236

### Re: 6.63 7th Edition

Or is this just a variation of the Nernst equation?
Sat Mar 16, 2019 8:12 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 6.63 7th Edition
Replies: 1
Views: 236

### 6.63 7th Edition

Can anyone possibly explain how the solutions manual arrives at 0.06V = Enot - (0.025693/1)(2.303)log(H+)? particularly the numbers plugged in for (RT/nF)lnH+
Fri Mar 15, 2019 12:35 pm
Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
Topic: Corrosion
Replies: 2
Views: 264

### Corrosion

Should we be familiar with the process of corrosion, particularly due to exposure to water and oxygen, and corrosion prevention for the final?
Wed Mar 13, 2019 12:42 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: enthalpy and spontaneity/favorability
Replies: 1
Views: 243

### enthalpy and spontaneity/favorability

Can the change in enthalpy be used to determine whether the forward reaction or reverse reaction is favored? (as in 4.45 7th edition)
Wed Mar 13, 2019 12:41 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: enthalpy and spontaneity/favorability
Replies: 2
Views: 252

### enthalpy and spontaneity/favorability

Can the change in enthalpy be used to determine whether the forward reaction or reverse reaction is favored? (as in 4.45 7th edition)
Tue Mar 12, 2019 2:05 pm
Forum: Calculating Work of Expansion
Topic: 4.17 7th Edition
Replies: 1
Views: 280

### 4.17 7th Edition

For part c of this problem, where you have to solve for the final volume of the pressure constant cylinder including excess reactant, why wouldn't you calculate the volume using the excess reactant in addition to the volume for all of the reactants used in the reaction?
Sun Mar 10, 2019 5:31 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: question 5 on Test 2
Replies: 2
Views: 149

### Re: question 5 on Test 2

The negative log of the H+ concentration essentially gives you the new "neutral" pH at the second temperature. So as was said above, pH 7 > pH x, so pH 7 is basic
Wed Feb 27, 2019 4:54 pm
Forum: Balancing Redox Reactions
Topic: oxidation numbers (hw 6k.1 7th ed)
Replies: 2
Views: 95

### oxidation numbers (hw 6k.1 7th ed)

Why is it that, when identifying oxidized and reduced elements and determining their oxidation numbers, sometimes the oxidation numbers are given for homonuclear diatomic molecules and sometimes its given for just the singular element? Like in 6K.1 (a), the oxidation number for Cr is 6+ (which is wh...
Tue Feb 26, 2019 3:18 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: test 2
Replies: 6
Views: 180

### Re: test 2

How much of outline 4 will be on this test (if any at all)? Is it just the material having to do with Gibbs free energy or the content prior to that as well?
Mon Feb 25, 2019 10:54 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: E not
Replies: 2
Views: 128

### Re: E not

According to Lavelle's lecture, E not is the standard reduction potential and gives voltage difference between two standard electrodes which are always the same, as in these values are empirically predetermined and can be found on a table. Ecell is the cell potential but I don't think it can be empi...
Tue Feb 12, 2019 4:00 pm
Forum: Phase Changes & Related Calculations
Topic: rotational v vibrational energy
Replies: 5
Views: 476

### rotational v vibrational energy

What exactly is the difference between rotational and vibrational energy? If a molecule has one does it also always have the other?
Tue Feb 12, 2019 2:09 pm
Forum: Phase Changes & Related Calculations
Topic: joules conversion factor
Replies: 7
Views: 511

### joules conversion factor

Should we memorize the conversion factor for atm L to joules?
Tue Feb 12, 2019 1:30 pm
Forum: Phase Changes & Related Calculations
Topic: reversible processes and equilibrium
Replies: 4
Views: 175

### reversible processes and equilibrium

If a process is reversible, does that mean that it's also essentially always in equilibrium?
Sun Feb 10, 2019 9:50 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Most stable form?
Replies: 4
Views: 199

### Most stable form?

How do you determine an element's most stable form (as it pertains to standard enthalpy of formation)?
Sun Feb 10, 2019 9:49 pm
Forum: Phase Changes & Related Calculations
Topic: Combustion/form of water produced
Replies: 2
Views: 111

### Combustion/form of water produced

What dictates what form water products will take? The combustion equations given in 4D.3 of the 7th Edition textbook give one equation where the water product is gas and one where it is liquid.
Tue Jan 22, 2019 11:37 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5G.3 7th Edition (When to use P vs molecular formula/concentrations)
Replies: 5
Views: 169

### Re: 5G.3 7th Edition (When to use P vs molecular formula/concentrations)

So if the chemical equilibrium equation consists only of gases and K isn't specified as Kc or Kp, you'd most likely use P subscripts?
Tue Jan 22, 2019 11:10 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5G.3 7th Edition (When to use P vs molecular formula/concentrations)
Replies: 5
Views: 169

### 5G.3 7th Edition (When to use P vs molecular formula/concentrations)

This question gives a chemical equation and asks you to write the expression for K, and the solutions manual uses P subscript molecular formula rather than just the molecular formula and concentrations. Are these two forms interchangeable when the question doesn't specifically ask for concentrations...
Wed Jan 16, 2019 8:47 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Q vs K [ENDORSED]
Replies: 4
Views: 189

### Q vs K[ENDORSED]

What exactly is the difference between the reaction quotient and the equilibrium constant?
Sun Dec 09, 2018 8:57 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Ka/Kb, pKa/pKb [ENDORSED]
Replies: 1
Views: 81

### Ka/Kb, pKa/pKb[ENDORSED]

Should we know how to calculate Ka/Kb, pKa/pKb, or just understand them conceptually with relation to acid and base strength?
Sun Dec 09, 2018 8:45 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: 6B.5c (7th Edition)
Replies: 1
Views: 78

### 6B.5c (7th Edition)

For question 6B.5c, why do you multiply M of Ba(OH)2 by 2?
Sat Dec 08, 2018 11:33 pm
Forum: Bronsted Acids & Bases
Topic: Fundamentals J.17 (7th Edition)
Replies: 1
Views: 120

### Fundamentals J.17 (7th Edition)

(With regard to weak acids and bases) why is it that for proton transfer reactions such as those in J.17, some of the atoms in the weak acid or base are not included in the chemical equation? I think I remember prof explaining this in lecture, but I don't exactly remember the explanation.
Sat Dec 08, 2018 5:56 pm
Forum: Conjugate Acids & Bases
Topic: Strong acids and bases to memorize
Replies: 9
Views: 915

### Re: Strong acids and bases to memorize

So if we can memorize strong acids/bases, is it necessary to memorize common weak acids/bases? Or, like the original poster said, can we just assume that anything now on the list of strong acids/bases is a weak acid/base?
Sat Dec 08, 2018 5:53 pm
Forum: Conjugate Acids & Bases
Topic: NH3, acid or base?
Replies: 12
Views: 2683

### NH3, acid or base?

With problems using ammonia, when would ammonia be a Bronsted acid versus a Bronsted base? Is it just a given that when NH3 reacts with water it acts as a base and becomes NH4-?
Sat Dec 08, 2018 5:51 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Oxyacids
Replies: 4
Views: 432

### Oxyacids

For oxyacids, what is it about molecules with more oxygen atoms that make the molecules more acidic?
Fri Nov 30, 2018 12:30 am
Forum: Hybridization
Topic: 2F.3b (7th Edition)
Replies: 1
Views: 100

### 2F.3b (7th Edition)

When identifying bond types in a molecule, would you always use the lowest energy lewis structure? Because for this question, the solutions manual essentially gives two answers, one for a lewis structure with resonance and one for without, and the two would yield different answers about the number o...
Thu Nov 29, 2018 6:01 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 2E.19b (7th Edition)
Replies: 2
Views: 126

### 2E.19b (7th Edition)

For the lewis structure of (CH3)2Be, where beryllium is connecting the two methyl groups, does that connecting atom need to have a complete octet or not/is Be just an exception to the rule where it can exist with only four valence electrons?
Thu Nov 29, 2018 5:56 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: trans/cis
Replies: 4
Views: 221

### Re: trans/cis

So the only way to identify whether a molecule is trans or cis is by the molecule's systematic name rather than merely by the molecular formula?
Thu Nov 29, 2018 4:06 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: trans/cis
Replies: 4
Views: 221

### trans/cis

Could someone help explain trans/cis molecules and what dictates which structure a molecule is? The book (7th edition) uses dichloroethene (C2H2Cl2) as an example of trans and cis molecules.
Mon Nov 26, 2018 10:46 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: test #3
Replies: 14
Views: 713

### Re: test #3

Like the other posters said, Dr. Lavelle said to memorize basic VSEPR model bond angles and the general reasons behind them. But in addition he said to understand conceptually the bond angles for molecules with lone pairs on the central atom.
Mon Nov 26, 2018 10:41 pm
Forum: Resonance Structures
Topic: Labelling Resonance Structures
Replies: 3
Views: 323

### Labelling Resonance Structures

When drawing resonance structures, is it necessary to label the atoms numerically like the solutions manual does? (e.g. the solution for 2B.17 7th edition)
Fri Nov 16, 2018 1:00 am
Forum: Sigma & Pi Bonds
Topic: Differences in energy
Replies: 5
Views: 239

### Re: Differences in energy

Do sigma and pi bonds directly correspond with bond length AND bond energy?
Fri Nov 16, 2018 12:58 am
Forum: Lewis Structures
Topic: Axial Bond Angles
Replies: 3
Views: 130

### Re: Axial Bond Angles

Do axial bond angles only exist in conjunction with equatorial bond angles?
Fri Nov 16, 2018 12:54 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Linear shape alternate forms
Replies: 3
Views: 107

### Re: Linear shape alternate forms

But in the same vein, why is the answer for 2E.1 (7th ed) that there MAY be lone pairs on the central atom rather than there are none?
Fri Nov 02, 2018 3:43 am
Forum: Lewis Structures
Topic: Expanded octets
Replies: 6
Views: 317

### Re: Expanded octets

What do you mean by "an extra ten electrons?" I thought that the total amount of electrons an expanded octet could hold was twelve?
Fri Nov 02, 2018 3:40 am
Forum: Bond Lengths & Energies
Topic: Lengths of Bonds
Replies: 9
Views: 260

### Re: Lengths of Bonds

The concept is sort of similar to how as you move across a period on the periodic table the atomic radius becomes shorter because the charge is greater so there's more attraction between the valence shell and the nucleus. Similarly, the more bonds there are, the shorter the distance between atoms
Fri Nov 02, 2018 3:37 am
Forum: Dipole Moments
Topic: London Forces
Replies: 7
Views: 428

### Re: London Forces

I know that relative to dipole-dipole and hydrogen bond IMFs, London dispersion forces are the weakest. But since LDFs depend on charge, is there ever an instance where an LDF is stronger than a dipole-dipole force?
Thu Oct 25, 2018 10:43 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: nodal planes for d-orbitals
Replies: 3
Views: 152

### nodal planes for d-orbitals

I know p-orbitals have one nodal plane (I think), but do d-orbitals always have two nodal planes or does it depend on the orientation of planes?
Thu Oct 25, 2018 5:30 pm
Forum: Properties of Electrons
Topic: mass of electron
Replies: 5
Views: 287

### mass of electron

Is the mass of an electron something we should memorize?
Thu Oct 25, 2018 5:13 pm
Forum: Einstein Equation
Topic: 1B.9 (7th edition)
Replies: 1
Views: 362

### 1B.9 (7th edition)

The textbook says, "...the intensity of radiation is an indication of the number of photons present, whereas E = hv is a measure of the energy of each individual photon." But in 1B. 9 (of the 7th edition), the question asks for the number of photons that can be generated and how many moles...
Sun Oct 14, 2018 10:51 pm
Forum: DeBroglie Equation
Topic: Wavelength Verification in Lab
Replies: 2
Views: 53

### Re: Wavelength Verification in Lab

I think he said it was experimentally verifiable because the electron does exhibit detectable wavelength properties, whereas in the prior problem the car (?) didn't have any detectable wavelength properties because the wavelength was too small.
Sun Oct 14, 2018 10:42 pm
Forum: Student Social/Study Group
Topic: Note Taking
Replies: 32
Views: 2450

### Re: Note Taking

Personally I prefer handwriting everything, even if it does get messy, because I find that when I physically write out notes or problems, it processes and sticks much better than typing something out and then going back to try to look at that. Plus, since most of the stuff in lecture is also in the ...
Sun Oct 14, 2018 10:38 pm
Forum: Properties of Light
Topic: Wavelength and Energy
Replies: 2
Views: 120

### Re: Wavelength and Energy

I think that essentially, the shorter the wavelength, the higher the frequency of the wave, hence the higher energy and vice versa.
Sun Oct 07, 2018 9:47 pm
Forum: Balancing Chemical Reactions
Topic: Where to start [ENDORSED]
Replies: 10
Views: 798

### Re: Where to start[ENDORSED]

When I was first taught to balance chemical reactions, we were told to draw out basic symbols to represent each atom/molecule (like circles or x's) so that you could more tangibly recognize when the equation is balanced. So that may help, but also like Jillian said, starting with the least represent...
Sun Oct 07, 2018 9:45 pm
Forum: Empirical & Molecular Formulas
Topic: Compound Names
Replies: 9
Views: 485

### Re: Compound Names

I think someone asked this in class and the professor essentially said, for now at least, we'll be given the formula's alongside the names and do not need to memorize polyatomic ions.
Sat Oct 06, 2018 10:23 pm
Forum: Empirical & Molecular Formulas
Topic: Empirical formula set up
Replies: 9
Views: 314

### Re: Empirical formula set up

If you assume a 100g sample, it's then easier to analyze the percent composition factors and work through the problem quantitatively and qualitatively.