Search found 16940 matches

by Chem_Mod
Mon Mar 18, 2019 4:49 pm
Forum: Calculating Work of Expansion
Topic: Work
Replies: 1
Views: 9

Re: Work

I think you are referring to the bomb calorimeter (fixed volume) problem. If there is no change in volume then w = 0.
by Chem_Mod
Mon Mar 18, 2019 4:47 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Enzyme
Replies: 1
Views: 2

Re: Enzyme

An enzyme is a biological catalyst.
by Chem_Mod
Mon Mar 18, 2019 4:45 pm
Forum: General Science Questions
Topic: ATP Coupling
Replies: 1
Views: 18

Re: ATP Coupling

ATP coupling refers to the energy released () during ATP hydrolysis is coupled (used) to drive an unfavorable reaction ().
by Chem_Mod
Mon Mar 18, 2019 4:42 pm
Forum: General Rate Laws
Topic: HW 7.23
Replies: 1
Views: 18

Re: HW 7.23

If water is no longer the solvent then it is part of the equilibrium constant and therefore in the rate law.
by Chem_Mod
Mon Mar 18, 2019 12:40 am
Forum: Administrative Questions and Class Announcements
Topic: Saying Thank You to Dr. Lavelle
Replies: 200
Views: 40361

Re: Saying Thank You to Dr. Lavelle

Thank you.

Signing off for this quarter.

Super long day. Time to zzz.
by Chem_Mod
Mon Mar 18, 2019 12:38 am
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7337
Views: 785880

Re: Post All Chemistry Jokes Here

Giselle1B wrote:"In a sports relay race, a chemical kinetics specialist runs slowly, and his group loses the race. When the chemical kinetics specialist is asked why he ran slowly, his reply was 'I always wanted to be the significant rate determining step.'


Good one!
by Chem_Mod
Mon Mar 18, 2019 12:38 am
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7337
Views: 785880

Re: Post All Chemistry Jokes Here

AngelaZ 1J wrote:What do dipoles say in passing?
"Have you got a moment?"


:-)
by Chem_Mod
Mon Mar 18, 2019 12:35 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Potentials
Replies: 1
Views: 8

Re: Cell Potentials

Standard cell potential is the voltage measured under standard conditions and is therefore a constant.
I discussed this in detail in class.
by Chem_Mod
Mon Mar 18, 2019 12:33 am
Forum: General Rate Laws
Topic: Integral of the Rate Laws [ENDORSED]
Replies: 1
Views: 9

Re: Integral of the Rate Laws [ENDORSED]

Give the integrated rate law = Simply write down the answer
by Chem_Mod
Sun Mar 17, 2019 7:02 pm
Forum: Administrative Questions and Class Announcements
Topic: Final Grade Release Date?
Replies: 7
Views: 39

Re: Final Grade Release Date?

Some TAs have there own final exams next week. Therefore they won't grade until after finals week. Sometime after finals week Chem 14B grades will be submitted.
by Chem_Mod
Sun Mar 17, 2019 6:56 pm
Forum: Administrative Questions and Class Announcements
Topic: Lavelle's other classes
Replies: 3
Views: 21

Re: Lavelle's other classes

No I don't. :-)
by Chem_Mod
Sun Mar 17, 2019 5:07 pm
Forum: Administrative Questions and Class Announcements
Topic: Saying Thank You to Dr. Lavelle
Replies: 200
Views: 40361

Re: Saying Thank You to Dr. Lavelle

You are most welcome.

Time to rest up and prepare for your next final.
by Chem_Mod
Sun Mar 17, 2019 4:34 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Internal energy change
Replies: 1
Views: 13

Re: Internal energy change

q = C delta T

Delta U = q + w

Fixed volume: w = 0

Therefore, Delta U = q
by Chem_Mod
Sun Mar 17, 2019 4:33 pm
Forum: Administrative Questions and Class Announcements
Topic: Final Grade Release Date?
Replies: 7
Views: 39

Re: Final Grade Release Date?

Sometime after final's week.
by Chem_Mod
Sun Mar 17, 2019 4:32 pm
Forum: Administrative Questions and Class Announcements
Topic: Final scores
Replies: 1
Views: 19

Re: Final scores

Sometime after final's week.
by Chem_Mod
Sun Mar 17, 2019 3:10 pm
Forum: *Identifying Primary, Secondary, Tertiary, Quaternary Carbons, Hydrogens, Nitrogens
Topic: Triprotic Acid
Replies: 1
Views: 18

Re: Triprotic Acid

I did this in class.
:-(

Can give off three protons.
by Chem_Mod
Sun Mar 17, 2019 3:08 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Ka and Ionization Constant
Replies: 1
Views: 11

Re: Ka and Ionization Constant

Yes. See my/your lecture notes.
by Chem_Mod
Sun Mar 17, 2019 2:30 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Reducing Power
Replies: 3
Views: 16

Re: Reducing Power

The more positive the standard reduction potential the more favorable the reaction, and therefore is a strong oxidizing agent.
by Chem_Mod
Sun Mar 17, 2019 2:26 pm
Forum: Second Order Reactions
Topic: Half Life for Second Order Reactions
Replies: 1
Views: 11

Re: Half Life for Second Order Reactions

Because for 2nd order reactions the half life depends on the initial concentration.
by Chem_Mod
Sun Mar 17, 2019 2:22 pm
Forum: Balancing Redox Reactions
Topic: 6.73 7th Edition
Replies: 1
Views: 15

Re: 6.73 7th Edition

Yes basic solution.
by Chem_Mod
Sun Mar 17, 2019 2:13 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Intristic values
Replies: 1
Views: 15

Re: Intristic values

Please clarify your question.
by Chem_Mod
Sun Mar 17, 2019 12:27 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 15.76 6th Edition
Replies: 1
Views: 13

Re: 15.76 6th Edition

Are you sure this is the correct question from the 6th edition textbook. The question I see is asking for an explanation regarding the Michaelis constant. There are no activation energies provided here.
by Chem_Mod
Sun Mar 17, 2019 9:52 am
Forum: Calculating Work of Expansion
Topic: Use of the two equations
Replies: 1
Views: 6

Re: Use of the two equations

Which two equations are you referring to?
by Chem_Mod
Sun Mar 17, 2019 9:49 am
Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
Topic: 6O3 7th edition
Replies: 1
Views: 12

Re: 6O3 7th edition

When trying to determine which substance is reduced all you need to pay attention to add reduction potentials that you are comparing. The larger (less negative) reduction potential means that it is more likely to get reduced.
by Chem_Mod
Sun Mar 17, 2019 9:46 am
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Disorder
Replies: 1
Views: 15

Re: Disorder

Heating a system results in an increase in thermal disorder. An increase in volume, which allows a substance to spread results in greater positional order. In comparing the contribution of either you have to see if temperature is increasing, volume is increasing, or both and use the change in entrop...
by Chem_Mod
Sun Mar 17, 2019 9:43 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: DeltaU = 3/2 nRT
Replies: 3
Views: 13

Re: DeltaU = 3/2 nRT

Typically, you would not be expected to calculate change in internal energy in this way. The change in internal energy = Q+W equation is more relevant. However, the equation you are referring is for kinetic energy of monatomic gases.
by Chem_Mod
Sun Mar 17, 2019 9:38 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: pKa and pKb
Replies: 4
Views: 10

Re: pKa and pKb

Yes, you would convert pKa to pKb using pKa+pKb=14 and then convert pKb to Kb using pKb= -logKb.
by Chem_Mod
Sun Mar 17, 2019 9:36 am
Forum: Biological Examples
Topic: ATP example
Replies: 3
Views: 24

Re: ATP example

The hydrolysis of every chemical is not necessarily negative but for ATP in particular when you’re breaking a bond a lot of energy is released because that bond was very unstable.
by Chem_Mod
Sun Mar 17, 2019 9:34 am
Forum: Biological Examples
Topic: atp exmaples
Replies: 1
Views: 10

Re: atp exmaples

What value are you taking about? If you’re asking why delta H is positive it’s because you are forming a very unstable bond that requires a lot of energy to form.
by Chem_Mod
Sun Mar 17, 2019 9:32 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalysts and pathways
Replies: 2
Views: 18

Re: Catalysts and pathways

Well we know that a change in temperature affects the rate constant k based on the Arrhenius equation and the factor by which the rate constant k changes is the same factor by which the rate itself changes according to the rate law. Therefore, you just need to take a ratio of the Arrhenius equation ...
by Chem_Mod
Sun Mar 17, 2019 9:29 am
Forum: First Order Reactions
Topic: First Order Equation
Replies: 3
Views: 12

Re: First Order Equation

This is the integrated rate law for a first order reaction. The integrated rate laws tell you how much concentration of something you have left after some time has passed.
by Chem_Mod
Sun Mar 17, 2019 9:26 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: units of T
Replies: 1
Views: 6

Re: units of T

As a good rule of thumb always convert time into seconds.
by Chem_Mod
Sun Mar 17, 2019 9:25 am
Forum: Ideal Gases
Topic: non gases
Replies: 1
Views: 5

Re: non gases

Yes, you cannot use the ideal gas law for nonideal gases, solids, or liquids.
by Chem_Mod
Sun Mar 17, 2019 9:24 am
Forum: Second Order Reactions
Topic: Plotting second order reactions
Replies: 3
Views: 9

Re: Plotting second order reactions

For a second order reaction, a plot of 1/[A] vs t should give you a straight line with a positive slope.
by Chem_Mod
Sun Mar 17, 2019 1:07 am
Forum: Balancing Redox Reactions
Topic: 6L 5C (7th Edition)
Replies: 1
Views: 14

Re: 6L 5C (7th Edition)

The solutions manual could technically choose any metal for the Au+ being oxidized to Au+3 reaction. They probably just decided to use Au since it's a metal that conducts electricity. But they could've used Pt or any other metal that conducts electricity. :)
by Chem_Mod
Sun Mar 17, 2019 1:00 am
Forum: Van't Hoff Equation
Topic: van't hoff
Replies: 1
Views: 19

Re: van't hoff

You probably won't have to worry about any equation derivations on the final exam. :)
by Chem_Mod
Sun Mar 17, 2019 12:58 am
Forum: Biological Examples
Topic: atp example
Replies: 1
Views: 11

Re: atp example

This is much more biological, but in relatively simple terms, the energy created by breaking the H off of NADH is used to drive the ATP reaction. :)
by Chem_Mod
Sun Mar 17, 2019 12:54 am
Forum: First Order Reactions
Topic: rate law
Replies: 2
Views: 11

Re: rate law

Once you calculate all the orders of the reactants, you would use this along with the rate of the reaction and initial concentrations of those reactants in order to calculate your rate constant, k. :)
by Chem_Mod
Sun Mar 17, 2019 12:49 am
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: molar mass
Replies: 2
Views: 6

Re: molar mass

It might be because you may need to use the molar heat capacity in several of the entropy formulas. When using the molar heat capacity for a substance in these equations, you must be able to convert the substance's mass into moles. :)
by Chem_Mod
Sun Mar 17, 2019 12:46 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Reversible vs irreversible
Replies: 1
Views: 11

Re: Reversible vs irreversible

During a reversible expansion, typically a force must be applied for a longer period of time since during a slow reversible expansion, at every point in the expansion, the internal pressure of the confined gas must be equal to the external pressure of the surrounding gas(es). During an irreversible ...
by Chem_Mod
Sun Mar 17, 2019 12:41 am
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: trials
Replies: 2
Views: 8

Re: trials

You set up the rate law expressions for the different experiments and then you divide one rate law expression by another rate law expression in order to cancel out terms and get only one exponent that you can solve for, using logarithms if necessary. These exponents are the orders. :)
by Chem_Mod
Sun Mar 17, 2019 12:34 am
Forum: Ideal Gases
Topic: ideal gases
Replies: 1
Views: 7

Re: ideal gases

For monoatomic ideal gases, a change could be occurring under the conditions of constant pressure or constant volume. Based on the degrees of freedom for the atoms under constant pressure or constant volume, we'll see that the heat capacity values will be different for constant pressure and constant...
by Chem_Mod
Sun Mar 17, 2019 12:31 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: specific heat
Replies: 1
Views: 7

Re: specific heat

The specific heat technically changes with temperature; however, you do not need to concern yourself with these changes for the final exam. For all intensive purposes, yes, the specific heat for a given chemical species will be a fixed value. :)
by Chem_Mod
Sun Mar 17, 2019 12:28 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: salt bridge
Replies: 4
Views: 24

Re: salt bridge

The main function of the salt bridge is to prevent charge build-up. :)
by Chem_Mod
Sun Mar 17, 2019 12:24 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: porous disk
Replies: 2
Views: 9

Re: porous disk

The porous disk serves the same function as the salt bridge (prevent charge build-up). :)
by Chem_Mod
Sun Mar 17, 2019 12:22 am
Forum: Second Order Reactions
Topic: k'
Replies: 1
Views: 5

Re: k'

You can typically use k' for any step in a multi-step mechanism. When you use k1', it is the symbol for the rate constant of the reverse reaction for step 1 of the mechanism. :)
by Chem_Mod
Sun Mar 17, 2019 12:19 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Liquids and Solids
Replies: 2
Views: 7

Re: Liquids and Solids

For K and Q, you are typically using the concentrations or partial pressures of the chemical species to write those expressions. But it's very difficult to define or even measure the concentrations or partial pressures of pure solids and pure liquids. It's much clearer how to measure the concentrati...
by Chem_Mod
Sun Mar 17, 2019 12:05 am
Forum: Balancing Redox Reactions
Topic: Balancing reaction in basic medium
Replies: 1
Views: 16

Re: Balancing reaction in basic medium

In this case, the P4 has an oxidation state (charge) of zero. On the right side, the P in H2PO2- will get an oxidation state of +1 and the P in PH3 will get an oxidation state of -3. So, P4 would be used as the reactant in both the oxidation and the reduction half reactions. From there, you will fol...
by Chem_Mod
Sat Mar 16, 2019 11:55 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: bomb calorimeter
Replies: 6
Views: 24

Re: bomb calorimeter

A bomb calorimeter is a closed system since it can't absorb or release energy from/to the surroundings and it also can't gain or lose mass to the surroundings. :)
by Chem_Mod
Sat Mar 16, 2019 11:53 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K
Replies: 3
Views: 10

Re: K

Capital K is the equilibrium constant. It represents the value you get when you divide concentrations of the product(s) by the concentrations of the reactant(s) once the chemical reaction has reached a state of chemical equilibrium. :)
by Chem_Mod
Sat Mar 16, 2019 11:50 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Deriving Enthalpy Equations
Replies: 3
Views: 18

Re: Deriving Enthalpy Equations

You probably won't have to worry about deriving equations on the exam. :)
by Chem_Mod
Sat Mar 16, 2019 11:48 pm
Forum: *Enzyme Kinetics
Topic: Elementary Steps
Replies: 1
Views: 8

Re: Elementary Steps

I think what you're referring to is that when you have to calculate the E value for a reaction like this: Ti +4 + 2e- -> Ti +2 , you cannot simply add the E values for the reactions Ti +4 + e- -> Ti +3 and Ti +3 + e- -> Ti +2 . The details about why this happens aren't too important, but this is a g...
by Chem_Mod
Sat Mar 16, 2019 11:34 pm
Forum: Second Order Reactions
Topic: Half Life
Replies: 5
Views: 11

Re: Half Life

While the formula sheets vary from year to year, it's likely that if these half-life equations were on the most recent exam, they will be on the final exam formula sheet. :)
by Chem_Mod
Sat Mar 16, 2019 11:31 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: pseudo rate reactions
Replies: 2
Views: 22

Re: pseudo rate reactions

Not quite, because k1' can represent the rate constant of the reverse reaction for step 1 in a mechanism. But, k' in pseudo rate kinetics often will be equal to k*[some reactant]. :)
by Chem_Mod
Sat Mar 16, 2019 11:27 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: unique rate law and reaction mechanisms?
Replies: 1
Views: 19

Re: unique rate law and reaction mechanisms?

One could set the unique rate of reaction equal to the rate law derived from a mechanism since both are mathematical expressions of the overall rate of the reaction. :)
by Chem_Mod
Sat Mar 16, 2019 11:23 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Elementary Rxns
Replies: 2
Views: 7

Re: Elementary Rxns

If and only if that particular reaction is an elementary reaction (meaning it's a reaction for one step in a mechanism), then yes, the coefficients in the balanced chemical equation will become the orders of those reactants. :)
by Chem_Mod
Sat Mar 16, 2019 11:22 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: standard cell potential and free energy
Replies: 3
Views: 12

Re: standard cell potential and free energy

Turns out that Gibbs free energy is an extensive property. :)
by Chem_Mod
Sat Mar 16, 2019 11:20 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Week 9 Worksheet (2E,I,K)
Replies: 13
Views: 390

Re: Week 9 Worksheet (2E,I,K)

I think this may be due to you using log instead of ln? On the equations sheet for the nearest equation they use ln. Which should we use? Hi Elle, You can use both. Please be aware that the difference is 0.0592 for log and 0.0257 for ln. If you plug in the number into two equations (in attachment),...
by Chem_Mod
Sat Mar 16, 2019 11:16 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Arrhenius equation
Replies: 2
Views: 21

Re: Arrhenius equation

Activation energy is the delta G value between a reactant and a transition state. So you could say that the delta G for the overall reaction = delta H of the reaction - T*(delta S of the reaction). But otherwise, there isn't an equation which relates the activation energy and delta H. :)
by Chem_Mod
Sat Mar 16, 2019 11:12 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Porous Disk vs Salt Bridge
Replies: 3
Views: 14

Re: Porous Disk vs Salt Bridge

The reason isn't too important. What's important is that you know that for a galvanic cell, the notation for a porous disk is a single vertical line and the notation for a salt bridge is 2 vertical lines. :)
by Chem_Mod
Sat Mar 16, 2019 11:07 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy of Fusion
Replies: 1
Views: 14

Re: Enthalpy of Fusion

Yes, it's definitely good to know about the enthalpies associated with the phase changes (melting, boiling, freezing, etc.). :)
by Chem_Mod
Sat Mar 16, 2019 10:52 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: UNITS
Replies: 2
Views: 8

Re: UNITS

The units for deltaS is units J/K
by Chem_Mod
Sat Mar 16, 2019 10:50 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: units
Replies: 1
Views: 6

Re: units

Delta H is typically in joules or joules/mole
by Chem_Mod
Sat Mar 16, 2019 10:49 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Arrhenius Equation
Replies: 3
Views: 15

Re: Arrhenius Equation

A is the pre-exponential or frequency factor which essentially gives you the proportion of reactants that collide in the correct orientation and with enough energy in order to form products.
by Chem_Mod
Sat Mar 16, 2019 10:48 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Units and order
Replies: 1
Views: 6

Re: Units and order

Yes you can solve for the units of the rate constant k because you know that the units for rate is molarity/second and the units for concentration is molarity, therefore the units for the rate constant k changes depending on the exponent of the concentration.
by Chem_Mod
Sat Mar 16, 2019 10:46 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: units
Replies: 1
Views: 5

Re: units

It's either in Joules or Joules/mole
by Chem_Mod
Sat Mar 16, 2019 10:46 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalyst in molecularity
Replies: 1
Views: 7

Re: Catalyst in molecularity

Molecularity is calculated by the number of molecules that must react with each other in order to form your products. Important thing to note is to realize that the stoichiometric coefficients must be accounted for in calculating molecularity.
by Chem_Mod
Sat Mar 16, 2019 10:42 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: ln k and 1/t
Replies: 3
Views: 14

Re: ln k and 1/t

What profile are you talking about. Are you referring to the rate law plots?
by Chem_Mod
Sat Mar 16, 2019 10:37 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: when is w=0 and when is q=0?
Replies: 1
Views: 18

Re: when is w=0 and when is q=0?

Work is 0 when there is no change in volume (isochoric). Heat is 0 for an adiabatic process, which will usually be explicitly stated.
by Chem_Mod
Sat Mar 16, 2019 10:33 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond enthalpy
Replies: 2
Views: 5

Re: Bond enthalpy

Sum of bonds broken - sum of bonds formed because this is essentially the amount of energy you are putting into the system to break bonds - the amount of energy that is released by the formation of new bonds.
by Chem_Mod
Sat Mar 16, 2019 10:29 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Drawing cells
Replies: 3
Views: 15

Re: Drawing cells

In general, you want to include the anode, cathode, ions, salt bridge, and direction the electrons are traveling.
by Chem_Mod
Sat Mar 16, 2019 9:19 pm
Forum: Administrative Questions and Class Announcements
Topic: Saying Thank You to Dr. Lavelle
Replies: 200
Views: 40361

Re: Saying Thank You to Dr. Lavelle

Thank you all your thoughtful and encouraging messages.

Posting that video was great!

A Big Thank You for the Valentine Cappella.
A first and most appreciated.

Great Quarter!
Great Classes!
by Chem_Mod
Sat Mar 16, 2019 9:07 pm
Forum: Student Social/Study Group
Topic: class pictures
Replies: 15
Views: 334

Re: class pictures

WOW.

Many great photos!
:-)

Many Thanks to All!

You Rock!
by Chem_Mod
Sat Mar 16, 2019 7:50 pm
Forum: First Order Reactions
Topic: Clarification
Replies: 2
Views: 7

Re: Clarification

I am not sure what you are referring to.
by Chem_Mod
Sat Mar 16, 2019 7:47 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Standard of Formation
Replies: 1
Views: 4

Re: Standard of Formation

It will be clear what the constants that you are given represent.
by Chem_Mod
Sat Mar 16, 2019 7:45 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: HW 4A.11
Replies: 1
Views: 11

Re: HW 4A.11

Kelvin is the standard unit for temperature. As a good rule of thumb always have your temperature be in Kelvin.
by Chem_Mod
Sat Mar 16, 2019 7:43 pm
Forum: Balancing Redox Reactions
Topic: 6th edition 14.5
Replies: 2
Views: 7

Re: 6th edition 14.5

Please be more specific. Post the problem and part you are stuck on.
by Chem_Mod
Sat Mar 16, 2019 7:42 pm
Forum: Phase Changes & Related Calculations
Topic: heat capacity of an object
Replies: 3
Views: 9

Re: heat capacity of an object

Heat capacity are in those units so that you can multiply it by whatever the mass of your total object is giving you the heat capacity for that object or piece of matter.
by Chem_Mod
Sat Mar 16, 2019 7:41 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Ka and K
Replies: 1
Views: 7

Re: Ka and K

Ka and K are the same thing. Ka is just the equilibrium constant for an a reaction in which an acid is reacting.
by Chem_Mod
Sat Mar 16, 2019 7:39 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Delta S=0 for elemental molecules?
Replies: 1
Views: 5

Re: Delta S=0 for elemental molecules?

The entropy of formation is 0 because they are elemental molecules, meaning this is how they are found in nature, therefore there is no entropy change associated with them being formed.
by Chem_Mod
Sat Mar 16, 2019 7:36 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Reaction Profiles
Replies: 1
Views: 3

Re: Reaction Profiles

For endergonic reactions the reactant has a lower Gibb's free energy value than the products, which makes sense because when you take the gibb's free energy of the products - reactants you get a positive change in gibb's free energy. For an exergonic reaction, the reactants have a higher gibb's free...
by Chem_Mod
Sat Mar 16, 2019 7:32 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Changes in Concentration
Replies: 2
Views: 14

Re: Changes in Concentration

Le Chatelier's Principle states that the reaction will lean toward the side that opposes the change that has just occurred. For example, if you increase products then the reaction will lean to the left and products will turn into reactants, decreasing products. If you decrease products, the reaction...
by Chem_Mod
Sat Mar 16, 2019 7:30 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Equilibrium constant from G
Replies: 1
Views: 4

Re: Equilibrium constant from G

It comes from the equation
When the reaction is at equilibrium is equal to 0 and Q turns into K.
by Chem_Mod
Sat Mar 16, 2019 7:25 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Final Jitters
Replies: 6
Views: 80

Re: Final Jitters

These are some great tips! Some things I would add: 1) If you ever run into a question you have no idea how to tackle, think about the concept it's trying to test. Try to note anything that you remember about that concept. Usually that tells yourself that you do know something. It just may take some...
by Chem_Mod
Sat Mar 16, 2019 7:24 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 7E3 7th edition
Replies: 2
Views: 9

Re: 7E3 7th edition

Please be more specific, posting the problem would be very helpful.
by Chem_Mod
Sat Mar 16, 2019 7:22 pm
Forum: Student Social/Study Group
Topic: Midterm
Replies: 2
Views: 7

Re: Midterm

I do not believe Dr. Lavelle stated the average.
by Chem_Mod
Sat Mar 16, 2019 7:21 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Ka stuff
Replies: 2
Views: 8

Re: Ka stuff

HA and A- are just examples of an acid/base reaction, where HA is any acid and A- is its conjugate base. Know that Ka and Kb are the equilibrium constants for acids and bases respectively and that strong acids/bases do not have Ka/Kb because they dissociate completely.
by Chem_Mod
Sat Mar 16, 2019 7:19 pm
Forum: Calculating Work of Expansion
Topic: 7th Edition, 4.B.13
Replies: 2
Views: 5

Re: 7th Edition, 4.B.13

When the pressure is constant the work does not equal the change in volume. The equation for an irreversible expansion is W=-nRTln(V2/V1).
by Chem_Mod
Sat Mar 16, 2019 7:13 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 7th Edition 7D.5
Replies: 3
Views: 13

Re: 7th Edition 7D.5

Hi Whitney,

You are absolutely correct. That negative should be an equal's sign. Good job!
by Chem_Mod
Sat Mar 16, 2019 5:04 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Intermediates
Replies: 1
Views: 8

Re: Intermediates

In mechanisms, intermediates are chemicals introduced to us as products and then used up as reactants in later mechanism steps. For example:

A + B -> C + D
C + E -> F
D + G -> H

In this scenario, C and D are the only intermediates.

Hope this helps! :)
by Chem_Mod
Sat Mar 16, 2019 5:02 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Heat and Entropy
Replies: 2
Views: 12

Re: Heat and Entropy

Most likely, that would be true. I'm sure other factors are involved, but if heat is transferred from the surroundings to the system, since S = q rev/T, we'd probably expect an increase in entropy (disorder). :)
by Chem_Mod
Sat Mar 16, 2019 4:52 pm
Forum: Ideal Gases
Topic: Bar for partial pressure [ENDORSED]
Replies: 4
Views: 15

Re: Bar for partial pressure [ENDORSED]

You can treat bar and atm as almost the same thing, but if you want to be super safe, you can use that conversion factor to convert atmospheres into units of bar. :)
by Chem_Mod
Sat Mar 16, 2019 4:47 pm
Forum: General Rate Laws
Topic: H.W. Problem 15.17
Replies: 5
Views: 14

Re: H.W. Problem 15.17

In general, it's a good idea to start with the pairs of experiments where only one reactant's concentration is changing while the other concentrations are held constant. Looking at experiments 1 and 2, we see that both [A] and [C] are changing.

Hope this helps! :)
by Chem_Mod
Sat Mar 16, 2019 4:36 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Rate determining step & overall rate law
Replies: 1
Views: 10

Re: Rate determining step & overall rate law

In the case where the first step of the mechanism is the rate determining step, then yes. But in other cases, that's probably not going to be true because other k terms will be introduced if you have to use the pre-equilibrium approach to get rid of intermediate terms in the overall rate law express...
by Chem_Mod
Sat Mar 16, 2019 4:26 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Monoatomic Gas
Replies: 3
Views: 17

Re: Monoatomic Gas

A monoatomic ideal gas can be under conditions of constant T, constant P, and/or constant V, depending on the system presented to you. A monoatomic ideal gas is just an ideal gas (obeys PV = nRT) which has only 1 atom (Ne (g), Ar (g), etc.)

Hope this helps! :)
by Chem_Mod
Sat Mar 16, 2019 4:20 pm
Forum: First Order Reactions
Topic: deriving integrated forms
Replies: 1
Views: 10

Re: deriving integrated forms

You most likely won't be asked to derive the integrated rate laws on the final exam.

Cheers! :)

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