## Search found 55 matches

Sat Mar 17, 2018 10:48 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Using Appendix 2A
Replies: 2
Views: 259

### Re: Using Appendix 2A

If I understand your question correctly, I think that all this means is that when you add up the cell potential of an anode (which has a positive value) and a cathode (which has a negative value), the cell will be not spontaneous (-E of the cell) and will not be a useful battery.
Sat Mar 17, 2018 10:45 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Stoichiometric coefficients
Replies: 4
Views: 572

### Re: Stoichiometric coefficients

I think the stoichiometric coefficients are there to help us determine the rate law of the elementary step. It would give us the order of the reactant in the rate law.
Sat Mar 17, 2018 10:42 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Adiabatic vs Isothermal
Replies: 5
Views: 1844

### Adiabatic vs Isothermal

What is the difference between an adiabatic system and an isothermal system? I know isothermal means that no heat is flowing in or out of the system (the system is isolated/insulated).
Sat Mar 17, 2018 2:13 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Strength of Reducing Agents and Strength of Oxidizing Agents
Replies: 3
Views: 409

### Re: Strength of Reducing Agents and Strength of Oxidizing Agents

I understand the mnemonic device to determining which species is being reduced or being oxidized (OIL RIG or LEO GER). Let me clarify my question. In the question 14.25, they ask to list the elements Cu, Zn, Cr, and Fe according to increasing strength as reducing agents. I'm not sure how to determin...
Fri Mar 16, 2018 9:51 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Strength of Reducing Agents and Strength of Oxidizing Agents
Replies: 3
Views: 409

### Strength of Reducing Agents and Strength of Oxidizing Agents

Is there a mnemonic device or easy way to understand which species are stronger reducing agents or oxidizing agents?
Sun Mar 11, 2018 11:00 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagrams
Replies: 6
Views: 373

### Re: Cell Diagrams

Remember to use mnemonic devices to help you determine which is the anode and which is the cathode!

LEO - Lose Electrons Oxidation
GER - Gain Electrons Reduction

or

OIL - Oxidation is Lose (electrons)
RIG - Reduction is Gain (electrons)

REDCAT - Reduction is the Cathode
Sun Mar 11, 2018 10:58 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: rate law
Replies: 5
Views: 492

### Re: rate law

Yes, this is because we need to know how a change in concentration of one of the reactants will change the rate of the reaction. It is impossible to know the order of each reactant for every reaction without conducting experiments. We can come up with a proposed rate law, but it may not always be co...
Sun Mar 11, 2018 10:55 pm
Forum: *Enzyme Kinetics
Topic: 15.67
Replies: 4
Views: 405

### Re: 15.67

"Everything else" meaning temperature and concentration held constant, correct?
Sun Mar 11, 2018 10:51 pm
Forum: Calculating Work of Expansion
Topic: Midterm Q3B
Replies: 7
Views: 519

### Re: Midterm Q3B

In the case above, would molar mass be considered an extensive property since it's value is dependent upon the metal in question?
Tue Mar 06, 2018 10:13 pm
Forum: General Rate Laws
Topic: 15.8 The Rate Laws of Elementary Reactions
Replies: 1
Views: 155

### Re: 15.8 The Rate Laws of Elementary Reactions

I know that the reaction that is the "slow step" will have the same reaction rate as the overall reaction.
Sun Mar 04, 2018 5:12 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Kinetics vs Thermodynamics
Replies: 4
Views: 300

### Re: Kinetics vs Thermodynamics

I think Professor Lavelle used the example of diamond being thermodynamically favored to become a different product (though I'm not too sure what that was), however, we know that diamond does not indeed undergo this reaction because it requires a high amount of activation energy to overcome the ener...
Sun Mar 04, 2018 5:09 pm
Forum: Second Order Reactions
Topic: Second Order/Zero Order Half-Life
Replies: 2
Views: 211

### Re: Second Order/Zero Order Half-Life

I believe this is because for a zero order reaction, the rate at which the reactant is consumed is constant, thus the time it takes for the concentration of the substance to reduce by half would be dependent on the initial concentration. I could imagine that this explanation could almost be applied ...
Sun Mar 04, 2018 5:03 pm
Forum: General Rate Laws
Topic: Rate Law and Initial concentration of Reactant
Replies: 5
Views: 304

### Re: Rate Law and Initial concentration of Reactant

It is definitely a lot harder to find the rate of a reaction when using products because the progress of a reaction occurs at an exponential decay, this, the reaction rate towards the end of a reaction occurs a lot slower than at the beginning of a reaction. Therefore, we using reactant concentratio...
Sun Feb 25, 2018 9:26 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Galvanic cell set up
Replies: 8
Views: 451

### Re: Galvanic cell set up

But in a case in which you were unsure, you can always refer to the written reaction to determine which reactant is being oxidized and which is being reduced. This will help you find out which side is the anode or cathode ("redcat").
Sun Feb 25, 2018 9:23 pm
Forum: General Rate Laws
Topic: Rate Constants
Replies: 4
Views: 306

### Re: Rate Constants

Another way of explaining this is that at higher temperatures, the particles have much more energy in them and will move more and theoretically "clash" with particles of the other reactant, thus accelerating the speed of the reaction.
Sun Feb 25, 2018 9:20 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagrams
Replies: 4
Views: 311

### Re: Cell Diagrams

Yes, make sure to determine which reaction is oxidation and reduction. This will help you in determining the order as the cathode (right) is associated with reduction and the anode (left) is associated with oxidation.
Sun Feb 25, 2018 9:12 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Initial Rates
Replies: 3
Views: 230

### Re: Initial Rates

I think it's okay to assume initial rates because that's where we will be focusing our approximations with (because of the rate decreases as the reaction proceeds).
Sun Feb 18, 2018 9:06 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Platinum electrodes
Replies: 4
Views: 264

### Re: Platinum electrodes

I think Professor Lavelle said that Graphite electrodes are used as well because they do not affect the reaction, but Platinum electrodes are the most common (even though they might be extremely expensive, go figure).
Sun Feb 18, 2018 9:04 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Open System
Replies: 5
Views: 500

### Re: Open System

If this helps for comparison, a closed system would be like a sealed container, where heat can transfer in and out of the system but matter cannot (because the container is sealed).
Sun Feb 18, 2018 9:02 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Delta G= Wmax
Replies: 8
Views: 858

### Re: Delta G= Wmax

Does Wmax usually occur when the system is at equilibrium?
Sat Feb 10, 2018 4:53 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: When to use + sign
Replies: 11
Views: 520

### Re: When to use + sign

This would especially help when applying Le Chatelier's Principle as exothermic and endothermic reactions can shift the equilibrium of a system as well as in Electrochemistry where voltage of a battery should always be positive (it would be a good way to double check that you identified the correct ...
Sat Feb 10, 2018 4:49 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: units conversion for entropy
Replies: 6
Views: 330

### Re: units conversion for entropy

I think temperature is usually expressed in Kelvin as most of the conversions and constants are also expressed in Kelvin, so it makes it easier for calculations and as for Joules versus Kilojoules, q is usually found using heat capacity which is expressed in Joules.
Sat Feb 10, 2018 4:46 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: O2 Microstates
Replies: 2
Views: 336

### Re: O2 Microstates

Yes I believe it is because the molecule is monatomic.
Sun Feb 04, 2018 9:56 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Measuring delta G
Replies: 4
Views: 274

### Re: Measuring delta G

No, there is no machine which we can use to measure DeltaG. The only way to get a value for deltaG is by calculating for it using

deltaG = deltaH - T(deltaS)
Sun Feb 04, 2018 9:54 pm
Forum: Calculating Work of Expansion
Topic: Reversible Expansion Homework Questions
Replies: 1
Views: 120

### Reversible Expansion Homework Questions

I know this might be a bit late, but in preparation for the upcoming midterm, I had trouble looking for problems dealing specifically with reversible expansion of ideal gases (ex: $w = -nRT(ln\frac{V_{f}}{V_{I}})$)

Can someone point me to any good examples they found in the textbook? Thanks!
Sun Feb 04, 2018 9:48 pm
Forum: Phase Changes & Related Calculations
Topic: enthalpy and entropy when it comes to spontaneous reactions
Replies: 6
Views: 394

### Re: enthalpy and entropy when it comes to spontaneous reactions

A quick correction to the post regarding the equation to determine DeltaG and thus spontaneity:
Instead of multiplying temperature and change in enthalpy and subtracting the product from entropy, it is actually

deltaG = deltaH - (temperature)(deltaS)
Mon Jan 29, 2018 11:24 am
Forum: Calculating Work of Expansion
Topic: Deriving Equations for Work [ENDORSED]
Replies: 2
Views: 200

### Re: Deriving Equations for Work[ENDORSED]

It would be useful to know the derivations for the purpose of understanding how we arrived at the 2nd Law of Thermodynamics, but hopefully Dr. Lavelle will clarify this before the midterm.
Mon Jan 29, 2018 11:20 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Entropy Definition [ENDORSED]
Replies: 2
Views: 232

### Re: Entropy Definition[ENDORSED]

We can do this by using Degeneracy and as well as the fact that states of matter can “occupy” more positions when that matter has more entropy. For example, a substance in the gas phase has more entropy and thus can occupy more “positions” than a substance in the solid phase.
Mon Jan 29, 2018 11:18 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: reversible vs. irreversible [ENDORSED]
Replies: 2
Views: 132

### Re: reversible vs. irreversible[ENDORSED]

Reversible systems do more work because it’s is working against equal pressures on both sides (P internal = P external) and a pressure that will be constantly changing and thus will be pressing against a larger pressure than irresversible systems that work against a constant pressure.
Sat Jan 20, 2018 11:58 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: standard enthalpy of formation [ENDORSED]
Replies: 4
Views: 277

### Re: standard enthalpy of formation[ENDORSED]

Adding onto previous answers, I believe you will be using standard reaction enthalpies (from intermediate reactions) to calculate the enthalpy of formation (referring to the final reaction you wish to calculate for) in Hess's Law.
Sat Jan 20, 2018 11:51 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hess's Law
Replies: 2
Views: 80

### Re: Hess's Law

I think that it is acceptable to use fractions in the coefficients for Hess's Law because the final reaction is the sum of all the intermediate reactions, therefore, fractions of each reactant can exist in the intermediate reactions. Fractions may be useful in Hess's Law calculations because it may ...
Sat Jan 20, 2018 11:49 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Reversible and Irreversible
Replies: 4
Views: 277

### Re: Reversible and Irreversible

I think this has something to do with equilibrium. If an reaction is at equilibrium, the the reaction is reversible and if the reaction is not at equilibrium, the the reaction is not reversible. Is there another, better way to explain this? Or is this correct? This is what I've gathered from the las...
Sun Jan 14, 2018 9:26 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Specific Heat Capacities
Replies: 3
Views: 165

### Re: Specific Heat Capacities

I believe it is useful to know the specific heat capacity of water @ standard conditions because it is so commonly used and because it’ll make calculations much easier, but I’m sure for other molecules and substances the specific heat capacity will be given.
Sat Jan 13, 2018 11:18 am
Forum: Phase Changes & Related Calculations
Topic: Intensive vs. Extensive
Replies: 4
Views: 254

### Re: Intensive vs. Extensive

Intensive Properties refers to properties that do not depend on the size or amount of the substance while Extensive Properties do. For example mass and volume are extensive properties while density is not
Sat Jan 13, 2018 11:16 am
Forum: Phase Changes & Related Calculations
Topic: Sublimation
Replies: 4
Views: 306

### Re: Sublimation

You're correct in that the Triple Point is the point in which a substance can exist in all three states of matter. Even more so, this is the minimum pressure that is required for a substance to remain a liquid. You can think of this as a reference point in seeing phase changes, for example at pressu...
Thu Dec 07, 2017 3:52 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: negligible rule [ENDORSED]
Replies: 3
Views: 3690

### Re: negligible rule[ENDORSED]

I think first looking at the reactants and products of the problem would be a good indication for whether the problem is a weak acid/base question, especially if they only give you K instead of K_{A} or K_{B} . If they give you K_{A} or K_{B} , I think its safe to assume that you are working with we...
Thu Dec 07, 2017 3:50 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE table
Replies: 7
Views: 602

### Re: ICE table

Well we can't assume x=0 because then that would mean there was no change and we know that in a weak acid/base reaction, equilibrium is in constant motion. Instead, we assume x is a very small number, so much so that subtracting it from the initial concentration is negligible and wouldn't affect the...
Wed Nov 29, 2017 10:17 am
Forum: Hybridization
Topic: Trick for Hybridization
Replies: 2
Views: 170

### Re: Trick for Hybridization

A quick trick to hybridization is to find out the number of electron densities for a given atom that you want to find the hybridization for, then match it up with the appropriate hybridization which has the same number of orbitals. For example: An element with 2 electron densities = sp (s+p = 2) An ...
Wed Nov 29, 2017 10:11 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Le Chatelier's Principle
Replies: 4
Views: 808

### Re: Le Chatelier's Principle

Exothermic means that the reaction will release heat as a product, therefore when you take heat away from this reaction, the reaction will continue to proceed towards the product to produce more heat to compensate for the fact that you've taken away heat from the products. Endothermic means that the...
Wed Nov 29, 2017 10:07 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K constant
Replies: 1
Views: 133

### Re: K constant

When the problem has has K, it's usually implicit that they are referring to K_{c} or K_{p} . You would just have to pay attention to the units in which the initial concentration/pressures are given. If they give the initial numbers with the units M (molarity) you will know that the problem is refer...
Sat Nov 18, 2017 11:38 am
Forum: Naming
Topic: TM naming
Replies: 2
Views: 233

### Re: TM naming

(Greek prefix) + Ligand names in alphabetical order (that are bonded to the TM) + TM cation + (Roman Numeral) + (if there are anions within the coordination complex we will add a -o) + (if there are anions bonded to the coordination complex) the anion name + (Greek Prefix) + Hydrate. For example: [C...
Sat Nov 18, 2017 11:29 am
Forum: Hybridization
Topic: Hybridization
Replies: 6
Views: 351

### Re: Hybridization

As mentioned above, hybridization is the fusion of two different orbitals (the s and the p) which enable such atoms such as Carbon to form more than just 2 bonds as it would be expected to make. Instead, the "hybridization" of the s and p orbitals further show that Carbon will form 4 bonds...
Sat Nov 18, 2017 11:27 am
Forum: Electronegativity
Topic: Electroegativity
Replies: 9
Views: 678

### Re: Electroegativity

It would be helpful to know that Halogens and elements like Oxygen and Sulfur tend to have high electronegativity values than that of metals. This is because metals tend to lose electrons to form cations while nonmetals tend to want to gain one, two, or three more electrons to complete their octet b...
Sun Nov 12, 2017 11:16 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Molecular shapes
Replies: 2
Views: 91

### Re: Molecular shapes

A simple way to distinguish the differences in shape between polar and nonpolar molecules would be if the shape were "symmetrical" or not. Keep in mind this a simple an easy was to distinguish, but not always true and there are exceptions. However, it does apply to a lot of the shapes.
Sun Nov 12, 2017 11:14 am
Forum: Trends in The Periodic Table
Topic: Hydrogen Electronegativity
Replies: 4
Views: 2492

### Re: Hydrogen Electronegativity

Because Hydrogen does not take an octet (as mentioned above) and it forms a 1+ ion (thus taking a max of 2 valence electrons), Hydrogen will be more willing to complete its unstable 1s shell rather than lose it (because it can't otherwise it wouldn't be an element). And because of this character, it...
Sun Nov 05, 2017 2:32 pm
Forum: Lewis Structures
Topic: 3.51
Replies: 3
Views: 222

### Re: 3.51

Oxygen is in the middle of the structure because it has a higher first ionization energy value. This means it is less likely to give off an electron, and more likely will hold onto its electron and thus draw other electrons towards it. The electronegativity value for Chlorine means that it will more...
Sun Nov 05, 2017 2:27 pm
Forum: Electronegativity
Topic: Comparing Electronegativity of Elements
Replies: 5
Views: 765

### Re: Comparing Electronegativity of Elements

Also, metals are known to form ionic bonds due to their tendency to give off electrons and bond with nonmetals (who more often accept electrons due to their higher electron affinity values).
Sat Oct 28, 2017 8:44 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Delocalization [ENDORSED]
Replies: 3
Views: 398

### Re: Delocalization[ENDORSED]

"Delocalized electrons" speak to the fact that electrons have wave-like properties as well as particle-like properties. Delocalized essentially means that the electrons are in constant movement around the atoms involved in bonding rather than in rigid "orbitals" around a give ato...
Sat Oct 28, 2017 8:42 pm
Forum: Trends in The Periodic Table
Topic: periodic trend exceptions [ENDORSED]
Replies: 2
Views: 174

### Re: periodic trend exceptions[ENDORSED]

I think the exceptions have to do with Oxygen's electron configuration. Given its configuration, 1s^{2}2s^{2}2p^{4} and Nitrogen's 1s^{2}2s^{2}2p^{3} , Nitrogen's completed half shell of the p subshell makes it slightly more stable than oxygen's (which is has one more electron). Nitrogen's relative ...
Sat Oct 21, 2017 8:00 pm
Forum: SI Units, Unit Conversions
Topic: Prefixes [ENDORSED]
Replies: 6
Views: 600

### Re: Prefixes[ENDORSED]

I know for a fact that we will have to know the conversions between micro (10^-6 m), nano (10^-9 m), and picometers (10^-12 m) because of their relation to wavelength. First it is important to realize that the conversions for these three measurements decrease by 1000 (10^-3) beginning with 10^-6. A ...
Sat Oct 21, 2017 7:56 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Configuration Notation [ENDORSED]
Replies: 5
Views: 381

### Re: Configuration Notation[ENDORSED]

In reference to chromium and copper, I think the professor is going to go over this exception this week.
Sat Oct 21, 2017 7:54 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Electric Spin
Replies: 5
Views: 302

### Re: Electric Spin

Generally, according to Hund's Rule, electrons in the same subshell occupy different orbitals with parallel spin due to their repulsion to each other. So more commonly, you can fill in electron configurations first with the spin up electrons until all orbitals are filled, then fill in with spin down...
Sun Oct 15, 2017 11:40 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Atomic Spectroscopy vs Photoelectric Effect
Replies: 3
Views: 318

### Re: Atomic Spectroscopy vs Photoelectric Effect

I also believe that in Atomic Spectroscopy, the goal of the experiment was to determine at what energy levels of photons, will electrons of specific metals become excited to then release the energy. This experiment for Atomic Spectroscopy was more of a verification of the shell model for atoms while...
Sun Oct 15, 2017 11:32 am
Forum: Properties of Light
Topic: Equation/Formula Clarification
Replies: 4
Views: 378

### Re: Equation/Formula Clarification

The equation E_{k}=hv-phi , should be used when trying to find out the kinetic energy of an ejected electron. Also, you may rearrange the terms to solve for hv in which this would be the energy of the photon released. Notice that E_{k} is also equal to \frac{1}{2}(m_{e^{-}})(v_{e^{-}}^2&...
Wed Oct 04, 2017 4:46 pm
Forum: Molarity, Solutions, Dilutions
Topic: Problem G.25 in Fundamentals
Replies: 3
Views: 354

### Re: Problem G.25 in Fundamentals

I believe the reason why the solution manual is trying to prove the amount of doublings that would need to occur before there is only 1 atom of substance X is that after 70 doublings, the solution would essentially have 0 atoms of the substance, thus showing any more doublings past 70 doublings woul...

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