Search found 65 matches
- Sat Mar 16, 2019 10:47 pm
- Forum: Balancing Redox Reactions
- Topic: Oxidation Numbers
- Replies: 1
- Views: 498
Oxidation Numbers
How do you know the oxidation number for a species? For example in the reaction MnO4- (aq) + H2C2O4 (aq) --> Mn2+ (aq)+ CO2 (g) the oxidation number for Mn decreases from +7 to +2 and the oxidation number for C increases from +3 to +4 but how do you get these values other than the +2 that is shown o...
- Sat Mar 16, 2019 1:35 pm
- Forum: General Rate Laws
- Topic: Microscopic Reversibility [ENDORSED]
- Replies: 1
- Views: 488
Microscopic Reversibility [ENDORSED]
Can someone explain the significance of microscopic reversibility and an example of how we might need to apply it?
- Sat Mar 16, 2019 1:31 pm
- Forum: First Order Reactions
- Topic: Pseudo 1st order rate laws
- Replies: 2
- Views: 522
Re: Pseudo 1st order rate laws
I think the main thing to remember for pseudo-first order rate law is just that N=1 because [B] and [C] are in large excess they remain essentially constant.
- Sat Mar 16, 2019 1:28 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: 4A.13
- Replies: 1
- Views: 513
Re: 4A.13
Since it's asking for the change in the internal energy of the reaction mixture resulting from the neutralization reaction, you use the relation of q(reaction) = -q(calorimeter) like the answer book shows. I think we are supposed to assume deltaU = q for this problem because there is a constant volu...
- Sat Mar 16, 2019 1:23 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Relation between deltaG and E
- Replies: 1
- Views: 546
Relation between deltaG and E
If at equilibrium G=0 and Ecell=0, and if a positive value for E means reduction is spontaneous, would the value for deltaG also be positive? Is this the same type of direct relation?
- Sat Mar 16, 2019 1:20 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Final [ENDORSED]
- Replies: 9
- Views: 1140
Final [ENDORSED]
For the final can we assume that there will be a sheet with the Ecell values for reactions like we had with Test 2?
- Sat Mar 16, 2019 1:18 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: e- transfer
- Replies: 1
- Views: 390
e- transfer
If we can't measure the electron transfer of one cell in a half reaction what can we compare it to when calculating the e redox ? I remember having to compare it to a standard hydrogen electrode but is there an example for this?
- Sat Mar 16, 2019 1:15 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Max Cell Potential
- Replies: 1
- Views: 233
Re: Max Cell Potential
Also is there another method for finding max potential before any current flow besides using the Nernst equation?
- Sat Mar 16, 2019 1:11 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Max Cell Potential
- Replies: 1
- Views: 233
Max Cell Potential
How is max cell potential related to the Gibbs free energy difference between reactions and products in a redox reaction? Can someone give an example to show the relation?
- Sat Mar 16, 2019 1:09 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Standard Conditions
- Replies: 2
- Views: 639
Standard Conditions
When calculating the deltaG of a reaction with standard conditions can we always assume n = 1.00 mol in -nFE?
- Sat Mar 16, 2019 1:07 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Electrical Work & Free Energy
- Replies: 1
- Views: 250
Electrical Work & Free Energy
Is the work done by a system the same thing as Wmax?
- Sat Mar 16, 2019 1:05 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: How Does Concentration Affect Cell Potential
- Replies: 2
- Views: 531
How Does Concentration Affect Cell Potential
In general what is the significance of the dependence on cell potential on concentration? Do we just use Le Chatelier's Principle or is there some other explanation for the relation between increasing/decreasing concentrations and the Ecell?
- Sat Mar 16, 2019 1:01 pm
- Forum: General Rate Laws
- Topic: Rate Law
- Replies: 1
- Views: 436
Rate Law
When finding the rate law (rate function concentration) or the integrated rate law (rate function time), why do we only consider the reactants?
- Sat Mar 16, 2019 12:55 pm
- Forum: Calculating Work of Expansion
- Topic: Integrate Rate Law
- Replies: 2
- Views: 535
Re: Integrate Rate Law
I have the notes for the problem in class if you need that!
- Sat Mar 16, 2019 12:54 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: what is an electrolyte?
- Replies: 1
- Views: 283
Re: what is an electrolyte?
An electrolyte refers to a chemical compound that can conduct electricity by changing into ions when mixed in a solution. In a cell diagram there is an electrolyte and two electrodes (anode and cathode). The electrolyte is usually some solution of water or other solvents in which the ions are dissol...
- Sat Mar 16, 2019 12:49 pm
- Forum: *Organic Reaction Mechanisms in General
- Topic: Method of Initial Rates
- Replies: 1
- Views: 984
Method of Initial Rates
Can someone explain the steps for the method of initial rates to determine k & n ? I couldn't find an example of it in my notes
- Sat Mar 16, 2019 12:46 pm
- Forum: General Rate Laws
- Topic: Unique Rate quick question
- Replies: 2
- Views: 559
Re: Unique Rate quick question
In general for all reactions: aA --> bB + cC
The unique rate is -1/a * d[A]/dt = 1/b * d[B]/dt = 1/c * d[C]/dt
The unique rate is the same for all R & P in that 'unique' reaction
The unique rate is -1/a * d[A]/dt = 1/b * d[B]/dt = 1/c * d[C]/dt
The unique rate is the same for all R & P in that 'unique' reaction
- Sat Mar 16, 2019 12:42 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: The melting of snow on a sunny day
- Replies: 3
- Views: 831
Re: The melting of snow on a sunny day
Was the reasoning of snow/ice melting on a sunny day being spontaneous the same reason for part c of this problem where the cooling of a hot cup of coffee after it was just brewed was also supposed to be ΔG < 0 ? I was confused because I thought the phase change causing an increase in entropy wouldn...
- Sat Mar 16, 2019 12:37 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Reducing Power and Oxidation Power
- Replies: 1
- Views: 501
Reducing Power and Oxidation Power
What are the patterns/relations for ordering species in increasing reducing power going from their neutral to second oxidation state given the E value? And also what are the patterns/relations for ordering species in increasing oxidation power going the opposite way from their second oxidation state...
- Sat Mar 16, 2019 12:33 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Ionic Dissociation
- Replies: 1
- Views: 317
Ionic Dissociation
Can someone explain the steps for this problem please? The ionic dissociation of water is given by the following reaction: The standard enthalpy for the reaction is 58 kJ. mol-1. The Kw for the reaction at 25 degrees Celsius is 10^-14. Is a pH of 7 acidic or basic at 10 degrees Celsius? The reaction...
- Sat Mar 16, 2019 12:28 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Catalysts
- Replies: 2
- Views: 275
Re: Catalysts
I remember during lecture Lavelle went over problems of catalysts in the same phase as R and catalysts in different phases. He also emphasized that catalysts speed up a reaction (k increases) by lowering Ea.
- Sat Mar 16, 2019 12:26 pm
- Forum: Student Social/Study Group
- Topic: Studying for the Final
- Replies: 25
- Views: 2813
Re: Studying for the Final
homework problems! also reviewing lavelle's class notes because he always mentions that any type of problem he goes over during lecture should be known / can show up on exams.
- Sat Mar 16, 2019 12:22 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: 4D.15
- Replies: 1
- Views: 459
Re: 4D.15
First make sure your equations are balanced. The second equation is reversed and added to the first, plus 2x the third equation. When you do this the total change in enthalpy equation should look like this: -1300kJ.mol^-1 + 1560 kJ.mol^-1 + 2(-286 kJ.mol^-1) and when you calculate this you should ge...
- Sat Mar 16, 2019 12:14 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: HW 4F.11
- Replies: 1
- Views: 514
Re: HW 4F.11
You should assume ideal behavior and 1 mol N2 gas so the n value when calculating the change in entropy will be (1.00 mol)
- Sat Mar 16, 2019 12:11 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 5I.33
- Replies: 2
- Views: 401
Re: 5I.33
Did you make sure to convert the 17.4 mg to 0.0174 g CO2? Also when finding the Kc you should be dividing the concentrations of [NH3]^2 and [CO2} by 0.250 not the 25.0 g amount given in the question.
- Sat Mar 16, 2019 12:10 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 5I.33
- Replies: 2
- Views: 401
Re: 5I.33
Did you make sure to convert the 17.4 mg to 0.0174 g CO2? Also when finding the Kc you should be dividing the concentrations of [NH3]^2 and [CO2} by 0.250 not the 25.0 g amount given in the question.
- Wed Feb 27, 2019 10:19 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Standard Conditions
- Replies: 1
- Views: 189
Standard Conditions
When we use the equation deltaG= -nFE what are the standard conditions it is pertaining to? Does this mean the conditions before current flow or is that only related to the Nernst equation?
- Wed Feb 27, 2019 10:12 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Units
- Replies: 2
- Views: 357
Units
When calculating the change in Gibbs free energy, if the change in enthalpy is given in kilojoules and the change in entropy is given in joules is there a preference in the units used when converting?
- Wed Feb 27, 2019 10:10 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Cell Potential
- Replies: 1
- Views: 239
Cell Potential
How is the max cell potential related to the Gibbs free energy difference between reactants & products in redox reactions?
- Wed Feb 13, 2019 11:32 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Changes in Pressure
- Replies: 5
- Views: 580
Changes in Pressure
Why is the ratio (P1/P2) in the equation deltaS=nRln(P1/P2) instead of (P2/P1) like with the case of changing volume and changing temperature?
- Wed Feb 13, 2019 11:23 pm
- Forum: Conjugate Acids & Bases
- Topic: Writing equations
- Replies: 3
- Views: 715
Re: Writing equations
Is there a general structure to follow when writing an equilibrium expression when only given the one reactant for example HClO2(aq)? I understand that the H3O+(aq) ion in addition to the acid's conjugate base(ClO2-(aq)) goes on the right side (product side) of the expression but is H2O(l) always in...
- Wed Feb 13, 2019 11:15 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Stability
- Replies: 5
- Views: 500
Stability
How can you tell when a molecule is more stable given the equilibrium constant? The textbook uses the reasoning that a larger equilibrium constant (for example F2 in comparison to Cl2) to explain that Cl2 is more stable relative to its atoms @ 1000K and I was wondering if someone could explain that ...
- Tue Feb 12, 2019 10:42 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Percentage of Decomposition
- Replies: 1
- Views: 1482
Percentage of Decomposition
How do you calculate the percentage of decomposition at equilibrium in general? For example, problem 5G.5 from the 7th edition textbook asks what percentage of some diatomic molecule, X2 has decomposed at equilibrium and the answer is (6/11)*100=54.5% but I was confused on where to get those numbers...
- Sat Dec 08, 2018 9:42 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Formation Constants
- Replies: 1
- Views: 157
Formation Constants
The textbook mentions the formation constant Kf and refers back to a table with formation constants for other coordination complexes in aqueous solutions in a different section. Do we need to know these?
- Sat Dec 08, 2018 6:49 pm
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: List of Intramolecular Vs. Intermolecular Forces
- Replies: 1
- Views: 4930
List of Intramolecular Vs. Intermolecular Forces
Does anyone have a list of intramolecular vs. intermolecular forces? (specifically for the problems that ask to name which forces are involved)
- Sat Dec 08, 2018 6:46 pm
- Forum: Conjugate Acids & Bases
- Topic: Determining Conjugate Acid
- Replies: 5
- Views: 920
Re: Determining Conjugate Acid
Conjugate acids gains an H+ while the conjugate bases donate an H+
- Sat Dec 08, 2018 6:42 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Ligands
- Replies: 2
- Views: 353
Re: Ligands
Ligands are Lewis bases attached to the central atom or ion in a d-metal complex. They typically have 1 lone pair of electrons with which it bonds to the central atom or ion through a coordinate covalent bond. Ligands make up the coordination sphere of the central atom/ion and the number of points a...
- Sat Dec 08, 2018 6:39 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Polydentate
- Replies: 11
- Views: 1179
Re: Polydentate
based on the amount of bonding sites to the single central atom
- Sat Dec 08, 2018 6:38 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Concept of Chelation
- Replies: 3
- Views: 399
Re: Concept of Chelation
Chelation involves the formation or presence of 2 or more separate coordination bonds between a multiple bonded ligand and central atom. The 'chelate' just refers to that specific type of ligand. You can identify based on its polydentate structure.
Re: CN Charge
Is this referring to the cyanide ligand? If so it has a monoanionic charge
- Sat Dec 08, 2018 6:23 pm
- Forum: Naming
- Topic: Common Ligands
- Replies: 2
- Views: 319
Common Ligands
Is it necessary to have the common ligands from table 9C.1 in the textbook memorized? (Not just the neutral ones but the anionic ligands)
- Sat Dec 08, 2018 6:18 pm
- Forum: Air Pollution & Acid Rain
- Topic: Acid Rain
- Replies: 24
- Views: 3928
Re: Acid Rain
It is possible for rain to be acidic because as it falls from the atmosphere, it collects impurities which change the pH of the rain water to be acidic or alkaline.
- Sat Dec 08, 2018 6:09 pm
- Forum: Identifying Acidic & Basic Salts
- Topic: Neutral salt
- Replies: 3
- Views: 511
Re: Neutral salt
When Ka(cation)=Kb(anion) it is neutral
- Sat Dec 08, 2018 5:58 pm
- Forum: Identifying Acidic & Basic Salts
- Topic: salts of weak acids and bases
- Replies: 4
- Views: 724
Re: salts of weak acids and bases
Basic salts form from the neutralization of a strong base and a weak acid. For example, the reaction of sodium hydroxide (strong base) with acetic acid (weak acid) will yield water and sodium acetate which is a basic salt. Similarly, acid salts form from the neutralization reaction between a strong ...
- Sat Dec 08, 2018 5:46 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: HOCl vs HOI
- Replies: 9
- Views: 4223
Re: HOCl vs HOI
Cl is more electronegative than I. The O-H bond in HOI is stronger than the O-H bond in HOCl. As a result, HOI is a weaker acid.
- Sat Dec 08, 2018 5:44 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Ligands
- Replies: 6
- Views: 1039
Re: Ligands
Porphyrin ligands have 4 linked pyrrole rings that coordinate the metal ion
- Sat Dec 08, 2018 5:38 pm
- Forum: Resonance Structures
- Topic: Resonance and Polarity [ENDORSED]
- Replies: 1
- Views: 494
Resonance and Polarity [ENDORSED]
How does the resonance affect the molecule's polarity?
- Sat Dec 08, 2018 5:35 pm
- Forum: Dipole Moments
- Topic: Dipole Moments signifying polarity
- Replies: 2
- Views: 507
Re: Dipole Moments signifying polarity
The strength of the dipole moment isn't really necessary because as long as the structure of the molecule is not symmetric, it will be polar. The number of dipole moments however is necessary, because if the dipole moments cancel each other out, it will be non-polar.
- Sat Dec 08, 2018 5:29 pm
- Forum: Bond Lengths & Energies
- Topic: H bonding
- Replies: 14
- Views: 1529
Re: H bonding
Melting and boiling points result from the intermolecular forces present. Hydrogen bonding as an intermolecular force will increase both melting and boiling points because greater energy is needed to separate the molecules.
- Sat Dec 08, 2018 5:20 pm
- Forum: Coordinate Covalent Bonds
- Topic: polydentates
- Replies: 5
- Views: 633
Re: polydentates
I think the only way would be to draw the Lewis structure and see if it is attached to the central atom by 2 or more bonds. Knowing the number of donor atoms with electron pairs can also help identify if it would be a polydentate.
- Sat Dec 08, 2018 5:15 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: Representation of each Quantum Number
- Replies: 2
- Views: 546
Re: Representation of each Quantum Number
If the value of the quantum number l=0,1,2,3 then the orbital will be s,p,d,f respectively
- Sat Dec 08, 2018 5:08 pm
- Forum: Trends in The Periodic Table
- Topic: effective nuclear charge
- Replies: 2
- Views: 619
Re: effective nuclear charge
ENC refers to the net positive charge of the protons in the nucleus acting on the valence electrons. It is always less than the number of protons present in the nucleus because of the shielding effect (decrease in attraction) where the more electron shells there are, the greater the shielding effect...
- Sat Dec 08, 2018 5:00 pm
- Forum: Lewis Acids & Bases
- Topic: salts in acids and bases
- Replies: 2
- Views: 174
Re: salts in acids and bases
Since salts consist of a positive ion of a base and the negative ion of an acid, it will neutralize in the reaction.
- Sat Dec 08, 2018 4:53 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Transition metals & their oxidations states
- Replies: 1
- Views: 624
Re: Transition metals & their oxidations states
Transition metals have the highest number of unpaired valence electrons which are unstable and will want to form bonds, allowing for several different oxidation states.
- Sat Dec 08, 2018 4:51 pm
- Forum: Coordinate Covalent Bonds
- Topic: Chelates
- Replies: 4
- Views: 738
Re: Chelates
When they said more than one 'tie' were they referring to ligands bonding through multiple sites and is that the same as bonding through more than one atom?
- Sat Dec 08, 2018 4:45 pm
- Forum: Sigma & Pi Bonds
- Topic: Test 3 Q3D
- Replies: 4
- Views: 691
Re: Test 3 Q3D
I was confused on that too because I drew them next to each other but I wasn't sure if there was overlap or not
- Sat Dec 08, 2018 4:35 pm
- Forum: Hybridization
- Topic: Hybridization of lone pairs.
- Replies: 1
- Views: 157
Re: Hybridization of lone pairs.
I think you can use the bonds around the lone pair to determine the hybridization. If you know the hybrid orbitals used to build the sigma bonds (for example, an sp^2 hybridized nitrogen atom has 3 sp^2 orbitals and 1 p orbital), then you can determine the lone pair of electron is in a p orbital.
- Sat Dec 08, 2018 4:30 pm
- Forum: Polyprotic Acids & Bases
- Topic: Significance of Polyprotic Acids & Bases
- Replies: 6
- Views: 1001
Re: Significance of Polyprotic Acids & Bases
Polyprotic means there are multiple acidic protons that dissociate. Polyprotic acids can lose 2 or more of these protons, which become less acidic as they are lost in sequential steps.
- Sat Dec 08, 2018 4:26 pm
- Forum: Amphoteric Compounds
- Topic: amphoteric
- Replies: 2
- Views: 409
Re: amphoteric
amphoteric = can act as both an acid and a base
I sometimes confuse it with amphiprotic so just a reminder amphiprotic means it can both donate or accept hydrogen!
I sometimes confuse it with amphiprotic so just a reminder amphiprotic means it can both donate or accept hydrogen!
- Sat Dec 08, 2018 4:22 pm
- Forum: Lewis Structures
- Topic: Which resonance structure is the most stable?
- Replies: 2
- Views: 225
Re: Which resonance structure is the most stable?
if both possible structures have similar values for FC, then when the central atom has a formal charge = 0 that should be the most stable resonance structure.
- Sat Dec 08, 2018 4:20 pm
- Forum: Lewis Acids & Bases
- Topic: homework question
- Replies: 1
- Views: 194
Re: homework question
I think if you know the equilibrium constant you can calculate these values similar to pH and pOH.
pKa=-log(Ka)
pKb=-log(Kb)
And then you know a large Kb value indicates the high level of dissociation of a strong base, so a lower pKb value will indicate a stronger base.
pKa=-log(Ka)
pKb=-log(Kb)
And then you know a large Kb value indicates the high level of dissociation of a strong base, so a lower pKb value will indicate a stronger base.
- Sat Dec 08, 2018 4:13 pm
- Forum: Naming
- Topic: en and edta
- Replies: 3
- Views: 648
Re: en and edta
These are the abbreviations for ethylenediamine and ethylenediaminetetraacetic acid when the respective complex compounds are ligands (when attached to a central metal atom through coordinate bonding)
- Fri Oct 12, 2018 12:31 am
- Forum: SI Units, Unit Conversions
- Topic: Homework for Week 2
- Replies: 16
- Views: 1121
Re: Homework for Week 2
Is homework still being collected by TAs at the end of lecture on Friday or are they collecting it during discussion sections now?
- Fri Oct 12, 2018 12:26 am
- Forum: Properties of Light
- Topic: Threshold Energies
- Replies: 5
- Views: 459
Re: Threshold Energies
Depending on the metal's properties, it is easier to remove electrons from some metals than others. The variations in threshold energies are dependent on the metal's work function. The smaller the work function (minimum amount of energy required), the lower the frequency.
- Fri Oct 12, 2018 12:19 am
- Forum: Einstein Equation
- Topic: Symbol for frequency
- Replies: 12
- Views: 2286
Re: Symbol for frequency
The textbook also uses v to represent frequency, for example in the relation lambda (wavelength) * v ( frequency) = c (speed of light)