Search found 65 matches

by 605168557
Sat Mar 16, 2019 9:47 pm
Forum: Balancing Redox Reactions
Topic: Oxidation Numbers
Replies: 1
Views: 13

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...
by 605168557
Sat Mar 16, 2019 12:35 pm
Forum: General Rate Laws
Topic: Microscopic Reversibility [ENDORSED]
Replies: 1
Views: 13

Microscopic Reversibility [ENDORSED]

Can someone explain the significance of microscopic reversibility and an example of how we might need to apply it?
by 605168557
Sat Mar 16, 2019 12:31 pm
Forum: First Order Reactions
Topic: Pseudo 1st order rate laws
Replies: 2
Views: 10

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.
by 605168557
Sat Mar 16, 2019 12:28 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 4A.13
Replies: 1
Views: 6

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...
by 605168557
Sat Mar 16, 2019 12:23 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Relation between deltaG and E
Replies: 1
Views: 6

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?
by 605168557
Sat Mar 16, 2019 12:20 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: 53

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?
by 605168557
Sat Mar 16, 2019 12:18 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: e- transfer
Replies: 1
Views: 14

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?
by 605168557
Sat Mar 16, 2019 12:15 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Max Cell Potential
Replies: 1
Views: 7

Re: Max Cell Potential

Also is there another method for finding max potential before any current flow besides using the Nernst equation?
by 605168557
Sat Mar 16, 2019 12:11 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Max Cell Potential
Replies: 1
Views: 7

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?
by 605168557
Sat Mar 16, 2019 12:09 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Standard Conditions
Replies: 2
Views: 6

Standard Conditions

When calculating the deltaG of a reaction with standard conditions can we always assume n = 1.00 mol in -nFE?
by 605168557
Sat Mar 16, 2019 12:07 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Electrical Work & Free Energy
Replies: 1
Views: 2

Electrical Work & Free Energy

Is the work done by a system the same thing as Wmax?
by 605168557
Sat Mar 16, 2019 12:05 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: 10

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?
by 605168557
Sat Mar 16, 2019 12:01 pm
Forum: General Rate Laws
Topic: Rate Law
Replies: 1
Views: 5

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?
by 605168557
Sat Mar 16, 2019 11:55 am
Forum: Calculating Work of Expansion
Topic: Integrate Rate Law
Replies: 2
Views: 8

Re: Integrate Rate Law

I have the notes for the problem in class if you need that!
by 605168557
Sat Mar 16, 2019 11:54 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: what is an electrolyte?
Replies: 1
Views: 6

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...
by 605168557
Sat Mar 16, 2019 11:49 am
Forum: *Organic Reaction Mechanisms in General
Topic: Method of Initial Rates
Replies: 1
Views: 16

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
by 605168557
Sat Mar 16, 2019 11:46 am
Forum: General Rate Laws
Topic: Unique Rate quick question
Replies: 2
Views: 11

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
by 605168557
Sat Mar 16, 2019 11:42 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: The melting of snow on a sunny day
Replies: 3
Views: 38

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...
by 605168557
Sat Mar 16, 2019 11:37 am
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: 12

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...
by 605168557
Sat Mar 16, 2019 11:33 am
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: 10

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...
by 605168557
Sat Mar 16, 2019 11:28 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalysts
Replies: 2
Views: 8

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.
by 605168557
Sat Mar 16, 2019 11:26 am
Forum: Student Social/Study Group
Topic: Studying for the Final
Replies: 25
Views: 168

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.
by 605168557
Sat Mar 16, 2019 11:22 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 4D.15
Replies: 1
Views: 10

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...
by 605168557
Sat Mar 16, 2019 11:14 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: HW 4F.11
Replies: 1
Views: 4

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)
by 605168557
Sat Mar 16, 2019 11:11 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5I.33
Replies: 2
Views: 9

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.
by 605168557
Sat Mar 16, 2019 11:10 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5I.33
Replies: 2
Views: 9

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.
by 605168557
Wed Feb 27, 2019 10:19 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Standard Conditions
Replies: 1
Views: 28

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?
by 605168557
Wed Feb 27, 2019 10:12 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Units
Replies: 2
Views: 26

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?
by 605168557
Wed Feb 27, 2019 10:10 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Cell Potential
Replies: 1
Views: 29

Cell Potential

How is the max cell potential related to the Gibbs free energy difference between reactants & products in redox reactions?
by 605168557
Wed Feb 13, 2019 11:32 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Changes in Pressure
Replies: 5
Views: 39

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?
by 605168557
Wed Feb 13, 2019 11:23 pm
Forum: Conjugate Acids & Bases
Topic: Writing equations
Replies: 3
Views: 86

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...
by 605168557
Wed Feb 13, 2019 11:15 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Stability
Replies: 2
Views: 40

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 ...
by 605168557
Tue Feb 12, 2019 10:42 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Percentage of Decomposition
Replies: 1
Views: 39

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...
by 605168557
Sat Dec 08, 2018 9:42 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Formation Constants
Replies: 1
Views: 27

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?
by 605168557
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: 74

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)
by 605168557
Sat Dec 08, 2018 6:46 pm
Forum: Conjugate Acids & Bases
Topic: Determining Conjugate Acid
Replies: 5
Views: 83

Re: Determining Conjugate Acid

Conjugate acids gains an H+ while the conjugate bases donate an H+
by 605168557
Sat Dec 08, 2018 6:42 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Ligands
Replies: 2
Views: 29

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...
by 605168557
Sat Dec 08, 2018 6:39 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Polydentate
Replies: 11
Views: 141

Re: Polydentate

based on the amount of bonding sites to the single central atom
by 605168557
Sat Dec 08, 2018 6:38 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Concept of Chelation
Replies: 3
Views: 46

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.
by 605168557
Sat Dec 08, 2018 6:34 pm
Forum: Naming
Topic: CN Charge
Replies: 2
Views: 40

Re: CN Charge

Is this referring to the cyanide ligand? If so it has a monoanionic charge
by 605168557
Sat Dec 08, 2018 6:23 pm
Forum: Naming
Topic: Common Ligands
Replies: 2
Views: 23

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)
by 605168557
Sat Dec 08, 2018 6:18 pm
Forum: Air Pollution & Acid Rain
Topic: Acid Rain
Replies: 9
Views: 478

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.
by 605168557
Sat Dec 08, 2018 6:09 pm
Forum: Identifying Acidic & Basic Salts
Topic: Neutral salt
Replies: 3
Views: 53

Re: Neutral salt

When Ka(cation)=Kb(anion) it is neutral
by 605168557
Sat Dec 08, 2018 5:58 pm
Forum: Identifying Acidic & Basic Salts
Topic: salts of weak acids and bases
Replies: 4
Views: 66

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 ...
by 605168557
Sat Dec 08, 2018 5:46 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: HOCl vs HOI
Replies: 9
Views: 98

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.
by 605168557
Sat Dec 08, 2018 5:44 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Ligands
Replies: 6
Views: 66

Re: Ligands

Porphyrin ligands have 4 linked pyrrole rings that coordinate the metal ion
by 605168557
Sat Dec 08, 2018 5:38 pm
Forum: Resonance Structures
Topic: Resonance and Polarity [ENDORSED]
Replies: 1
Views: 41

Resonance and Polarity [ENDORSED]

How does the resonance affect the molecule's polarity?
by 605168557
Sat Dec 08, 2018 5:35 pm
Forum: Dipole Moments
Topic: Dipole Moments signifying polarity
Replies: 2
Views: 44

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.
by 605168557
Sat Dec 08, 2018 5:29 pm
Forum: Bond Lengths & Energies
Topic: H bonding
Replies: 12
Views: 157

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.
by 605168557
Sat Dec 08, 2018 5:20 pm
Forum: Coordinate Covalent Bonds
Topic: polydentates
Replies: 5
Views: 63

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.
by 605168557
Sat Dec 08, 2018 5:15 pm
Forum: Quantum Numbers and The H-Atom
Topic: Representation of each Quantum Number
Replies: 2
Views: 28

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
by 605168557
Sat Dec 08, 2018 5:08 pm
Forum: Trends in The Periodic Table
Topic: effective nuclear charge
Replies: 2
Views: 33

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...
by 605168557
Sat Dec 08, 2018 5:00 pm
Forum: Lewis Acids & Bases
Topic: salts in acids and bases
Replies: 2
Views: 23

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.
by 605168557
Sat Dec 08, 2018 4:53 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Transition metals & their oxidations states
Replies: 1
Views: 46

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.
by 605168557
Sat Dec 08, 2018 4:51 pm
Forum: Coordinate Covalent Bonds
Topic: Chelates
Replies: 4
Views: 45

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?
by 605168557
Sat Dec 08, 2018 4:45 pm
Forum: Sigma & Pi Bonds
Topic: Test 3 Q3D
Replies: 4
Views: 60

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
by 605168557
Sat Dec 08, 2018 4:35 pm
Forum: Hybridization
Topic: Hybridization of lone pairs.
Replies: 1
Views: 25

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.
by 605168557
Sat Dec 08, 2018 4:30 pm
Forum: Polyprotic Acids & Bases
Topic: Significance of Polyprotic Acids & Bases
Replies: 6
Views: 73

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.
by 605168557
Sat Dec 08, 2018 4:26 pm
Forum: Amphoteric Compounds
Topic: amphoteric
Replies: 2
Views: 36

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!
by 605168557
Sat Dec 08, 2018 4:22 pm
Forum: Lewis Structures
Topic: Which resonance structure is the most stable?
Replies: 2
Views: 33

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.
by 605168557
Sat Dec 08, 2018 4:20 pm
Forum: Lewis Acids & Bases
Topic: homework question
Replies: 1
Views: 29

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.
by 605168557
Sat Dec 08, 2018 4:13 pm
Forum: Naming
Topic: en and edta
Replies: 3
Views: 37

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)
by 605168557
Thu Oct 11, 2018 11:31 pm
Forum: SI Units, Unit Conversions
Topic: Homework for Week 2
Replies: 16
Views: 197

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?
by 605168557
Thu Oct 11, 2018 11:26 pm
Forum: Properties of Light
Topic: Threshold Energies
Replies: 5
Views: 54

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.
by 605168557
Thu Oct 11, 2018 11:19 pm
Forum: Einstein Equation
Topic: Symbol for frequency
Replies: 12
Views: 147

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)

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