Search found 30 matches

by TarynLane2J
Tue Mar 13, 2018 9:18 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Arrhenius
Replies: 1
Views: 116

Re: Arrhenius

reactions that give straight lines when plotted on the axes 1/T vs. ln(k) are Arrhenius because because it means that they satisfy the equation ln(k)=-Ea/RT + ln(A), where -Ea/R is the slope and ln(A) is the y intercept.
by TarynLane2J
Tue Mar 13, 2018 9:12 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: catalysts and intermediates
Replies: 2
Views: 183

Re: catalysts and intermediates

intermediates will be products of one step, and reactants of a later step, getting used up in the process. They will not remain at the end. Catalysts are there to begin with, and are not used up.
by TarynLane2J
Tue Mar 13, 2018 8:53 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Gas constants
Replies: 2
Views: 138

Re: Gas constants

It depends on units. Look at the units of the other stuff in the calculation and from there choose the value of R that makes sense. I think it's usually the 8.314 but not always
by TarynLane2J
Fri Mar 09, 2018 11:50 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 15.67
Replies: 1
Views: 128

Re: 15.67

I think that would give you the right answer. That's what I did as well.
by TarynLane2J
Fri Mar 09, 2018 11:48 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: reaction profiles in organic chemistry [ENDORSED]
Replies: 1
Views: 95

reaction profiles in organic chemistry [ENDORSED]

In lecture, Dr. Lavelle said that organic chemists write reaction profiles in a different way, using G naught on the y axis. Can someone expand on this and explain how is this different from in regular chemistry?
by TarynLane2J
Fri Mar 09, 2018 11:43 pm
Forum: First Order Reactions
Topic: slope
Replies: 3
Views: 316

slope

What is the slope of the linear plot of a first order reaction?
by TarynLane2J
Fri Mar 02, 2018 3:12 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: E = E^o - (RT/nF) ln Q [ENDORSED]
Replies: 4
Views: 251

Re: E = E^o - (RT/nF) ln Q [ENDORSED]

I think we would use the value 8.314 J/mol.K for R and assume 298K for T unless the problem says otherwise
by TarynLane2J
Fri Mar 02, 2018 2:56 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Arrhenius Reaction
Replies: 6
Views: 250

Re: Arrhenius Reaction

we have not gone over this in lecture, and we don't need to worry about for the test next week, only for the final
by TarynLane2J
Fri Mar 02, 2018 2:54 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: k prime vs k [ENDORSED]
Replies: 2
Views: 1607

k prime vs k [ENDORSED]

Can someone explain the difference between k prime and regular k? thank you!
by TarynLane2J
Fri Feb 23, 2018 12:37 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Reaction Favoring Products
Replies: 2
Views: 154

Re: Reaction Favoring Products

Another way you can think of it is that E represents standard Reduction potential, not oxidation potential, so you want E for the cathode to be big (since reduction occurs at the cathode) and E for the anode to be small, preferably negative, (since oxidation occurs at the anode). If this is true the...
by TarynLane2J
Fri Feb 23, 2018 12:27 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagrams [ENDORSED]
Replies: 7
Views: 379

Re: Cell Diagrams [ENDORSED]

Inert species such as platinum are usually used as electrodes when the species in the redox reaction are nonmetal and aren't able to transport electrodes. But if the species in the redox reaction is already a conductor such as copper or some other metal, then you don't need to add a platinum electro...
by TarynLane2J
Mon Feb 19, 2018 2:49 pm
Forum: Balancing Redox Reactions
Topic: H+ or H3O+
Replies: 2
Views: 148

H+ or H3O+

On the test, when balancing redox reactions in acidic solution, should we use H+ or H3O+, or does it not matter?
by TarynLane2J
Wed Feb 14, 2018 1:59 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Delta S(tot)
Replies: 5
Views: 477

Re: Delta S(tot)

Also, specifically for in a reversible system, deltaS(tot) is equal to 0, so deltaS(sys) = -deltaS(surr)
by TarynLane2J
Wed Feb 14, 2018 1:57 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: Standard molar entropy vs. residual entropy
Replies: 2
Views: 283

Re: Standard molar entropy vs. residual entropy

I think that residual entropy is the entropy left over once you cool a substance to absolute zero (or as close as you can get to absolute zero). So this would mean that all substances, except for perfect crystals, have some amount of residual entropy because the molecules can have multiple orientati...
by TarynLane2J
Wed Feb 14, 2018 1:50 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Difference between Gibbs Free Energy and standard Gibbs Free Energy
Replies: 2
Views: 1123

Re: Difference between Gibbs Free Energy and standard Gibbs Free Energy

In addition, delta G standard is equal to -RTlnK, while delta G (not under standard conditions) is equal to delta G standard +RTlnQ
by TarynLane2J
Thu Feb 08, 2018 8:37 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Circumstances of delta G
Replies: 3
Views: 173

Re: Circumstances of delta G

In addition, Gibbs free energy represents energy that is free to do useful work, so when delta G is zero i guess that means that there is no change in the amount of energy that is free to do work
by TarynLane2J
Thu Feb 08, 2018 8:04 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Delta G Standard
Replies: 2
Views: 451

Re: Delta G Standard

To answer the first part of your question, when delta G standard is negative, yes that means that the reaction is spontaneous at standard temperature and pressure (298 K and 1 atm)
by TarynLane2J
Tue Feb 06, 2018 12:27 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: salt bridge
Replies: 3
Views: 119

salt bridge

Can someone explain the purpose of the salt bridge in the redox reaction?
by TarynLane2J
Sun Feb 04, 2018 2:17 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: standard states
Replies: 3
Views: 191

standard states

For all standard states in general, is the pressure 1 atm or 1 bar? or does it not matter?
by TarynLane2J
Sun Feb 04, 2018 2:15 pm
Forum: Van't Hoff Equation
Topic: Change in Entropy Remains Constant
Replies: 3
Views: 200

Re: Change in Entropy Remains Constant

I think it has to do with the fact that at two different temperatures, the actual values for entropy are different, but as long as the substances are the same the change in entropy, delta S, is the same amount. Its like if you had the values 2 and 4, and then at a different temperature the values we...
by TarynLane2J
Sun Feb 04, 2018 2:04 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: second law of thermodynamics
Replies: 2
Views: 126

second law of thermodynamics

Why is it that as an object approaches absolute zero, the change in entropy approaches zero but entropy itself is only zero when it is a perfect crystal?
by TarynLane2J
Tue Jan 23, 2018 2:05 pm
Forum: Calculating Work of Expansion
Topic: work of expansion formula
Replies: 1
Views: 119

work of expansion formula

Can someone explain on a conceptual basis the reason for the negative sign in the equation ?
by TarynLane2J
Tue Jan 23, 2018 1:17 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 3/2RT
Replies: 4
Views: 260

Re: 3/2RT

I don't think so because I don't remember going over it in class but I could be wrong
by TarynLane2J
Tue Jan 23, 2018 1:10 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Calorimeters
Replies: 1
Views: 113

Calorimeters

Can someone explain what exactly a calorimeter is and how it works?
by TarynLane2J
Thu Jan 18, 2018 1:07 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Isolated system
Replies: 8
Views: 391

Isolated system

Can you do work on an isolated system? I know you cannot add any substances or heat/cool an isolated system, but what about doing work?
by TarynLane2J
Tue Jan 16, 2018 10:44 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: homework question 8.57
Replies: 1
Views: 74

homework question 8.57

In 8.57 the question uses the notation of delta H with the subscript c. What does the subscript c mean? thanks in advance!
by TarynLane2J
Tue Jan 16, 2018 10:37 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: question 8.55
Replies: 1
Views: 76

question 8.55

I did question 8.55 and then I realized that it is not included on the list of homework problems. Does this mean that it will not count as one of my 14 homework questions for this week?
by TarynLane2J
Thu Jan 11, 2018 3:09 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hess's Law example from lecture
Replies: 3
Views: 198

Re: Hess's Law example from lecture

Wenjie Dong 2E wrote:The equations should be:
N2 + O2 --> 2NO
2NO + O2 --> 2NO2
-----------------------
N2 + 2O2 --> 2NO2


Oh thank you so much I had them written down wrong. Does that mean that they are added together to get the third reaction?
by TarynLane2J
Thu Jan 11, 2018 3:02 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hess's Law example from lecture
Replies: 3
Views: 198

Hess's Law example from lecture

In the example for Hess's Law from Wednesday's lecture, we had the equations: N2 + O2 --> 2NO 2NO2 + O2 --> 2NO2 N2 + 2O2 --> 2NO2 Can someone clarify how the three equations are related and why we are able to add the enthalpies of the first two reactions in order to find the elthalpy of the third r...
by TarynLane2J
Thu Jan 11, 2018 2:41 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy of sublimation
Replies: 3
Views: 183

Re: Enthalpy of sublimation

Another way to think of it is that melting is going from solid to liquid, and vaporization is going from liquid to gas. But sublimation goes straight from solid to gas, eliminating the middle man, so conceptually it makes sense to add the vaporization enthalpy and fusion enthalpy to get sublimation ...

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