Search found 33 matches

by Michelle Chernyak 1J
Thu Mar 15, 2018 8:39 pm
Forum: *Electrophiles
Topic: what is going to be on the final? [ENDORSED]
Replies: 12
Views: 843

what is going to be on the final? [ENDORSED]

Because these topics were gone over after the midterm, will electrochem and kinetics make up a bigger part of the final?
by Michelle Chernyak 1J
Thu Mar 15, 2018 8:37 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Midterm #5
Replies: 1
Views: 84

Re: Midterm #5

Because the system returns to its original internal energy, the overall deltaU of the reaction is 0. That means whatever deltaU we calculated in the first step we have to do the reverse of in the second step in order for them to cancel out and go back to 0.
by Michelle Chernyak 1J
Mon Mar 12, 2018 9:22 pm
Forum: *Enzyme Kinetics
Topic: Temperature and rate constants
Replies: 2
Views: 231

Temperature and rate constants

Can someone explain to me how raising the temperature will affect the rate constant?
by Michelle Chernyak 1J
Mon Mar 12, 2018 8:57 pm
Forum: *Enzyme Kinetics
Topic: Catalysis 15.69
Replies: 3
Views: 271

Catalysis 15.69

Help! I'm really confused with this problem. I feel like i need to solve for k of the first reaction and then use that to solve for the activation energy of the second but I don't even know if that's right. Also, when they say that all other factors are equal, do they mean to each or to their values...
by Michelle Chernyak 1J
Mon Mar 12, 2018 12:07 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Multiplying Equilibrium Constants
Replies: 1
Views: 90

Re: Multiplying Equilibrium Constants

Because we are combining two equations, we now have 2 equilibrium constants, each with a different set of products over a different set of reactants. It would be impossible to add the two equilibrium constants together without altering the reaction (simple math; you'd have to bring it to a common de...
by Michelle Chernyak 1J
Mon Mar 12, 2018 12:00 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Collision Cross Section
Replies: 2
Views: 184

Re: Collision Cross Section

if a molecule is not at the proper orientation when a collision happens, then the reaction will not occur
by Michelle Chernyak 1J
Sun Mar 11, 2018 11:58 pm
Forum: General Rate Laws
Topic: Rate law constant
Replies: 4
Views: 150

Re: Rate law constant

i don't think the number itself can be a negative number, but k will be negative when it is the slope of a zero order or first order reaction.
by Michelle Chernyak 1J
Sun Mar 11, 2018 11:57 pm
Forum: Administrative Questions and Class Announcements
Topic: Chapters in Final Exam
Replies: 3
Views: 282

Re: Chapters in Final Exam

nope, just the ones on the syllabus!
by Michelle Chernyak 1J
Sun Mar 11, 2018 11:56 pm
Forum: Zero Order Reactions
Topic: Half life
Replies: 7
Views: 580

Re: Half life

yes
by Michelle Chernyak 1J
Mon Mar 05, 2018 4:31 pm
Forum: Balancing Redox Reactions
Topic: Test 2 Q8
Replies: 2
Views: 124

Re: Test 2 Q8

When the two reactions are combined, Cl- is a product and I- is a reactant. Because we do not include solids or liquids when calculating the equilibrium quotient, Q= [Cl-]/[I-]
by Michelle Chernyak 1J
Mon Mar 05, 2018 4:26 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Molecularity
Replies: 3
Views: 109

Re: Molecularity

Molecularity is only used to describe elementary reactions
by Michelle Chernyak 1J
Mon Mar 05, 2018 4:25 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Elementary Reactions
Replies: 2
Views: 96

Re: Elementary Reactions

It depends. I think sometimes we will need to figure out the components on our own.
by Michelle Chernyak 1J
Mon Feb 26, 2018 4:48 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Standard Potential
Replies: 4
Views: 182

Re: Standard Potential

standard potentials occur at 1 bar and when the substances in question are at their most stable states
by Michelle Chernyak 1J
Mon Feb 26, 2018 4:46 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14.25
Replies: 1
Views: 83

Re: 14.25

When it comes to voltaic cells, an input of energy/electric current is necessary in order for the reaction to occur. Because of this, a large negative cell potential would require a large input of energy.
by Michelle Chernyak 1J
Mon Feb 26, 2018 4:43 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Activation Energy and Temperature Dependence of Rates
Replies: 2
Views: 112

Re: Activation Energy and Temperature Dependence of Rates

Because they have low activation energies, these reactions only require a small energy input in order to occur, therefore increasing the temperature would not make that big of a difference. This is because the reaction is already close to happening and therefore does not need a huge input so there w...
by Michelle Chernyak 1J
Mon Feb 26, 2018 4:39 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Slowest Elementary Step
Replies: 4
Views: 159

Re: Slowest Elementary Step

Have you ever heard of the saying that a team is only as strong as its weakest link? Well basically its the same type of situation. Even if there are faster steps in the reaction, the slowest step is the one that governs the reaction because the rate of the reaction must accommodate for that step as...
by Michelle Chernyak 1J
Wed Feb 14, 2018 10:17 am
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Work
Replies: 5
Views: 247

Re: Work

Yes you are correct. There s no work being done as a gas expands in a volume because there is no opposing force.
by Michelle Chernyak 1J
Wed Feb 14, 2018 10:15 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: State Properties
Replies: 5
Views: 360

Re: State Properties

Specific heat capacity is the amount of energy it requires to raise 1 g of a substance by 1 degree of temperature while heat capacity is the amount of energy it requires to raise the given amount 1 degree of temperature. Specific heat is an intensive property, meaning that regardless of the amount p...
by Michelle Chernyak 1J
Wed Feb 14, 2018 10:10 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Why are standard free energies of formation zero for elements in their stablest form?
Replies: 2
Views: 144

Re: Why are standard free energies of formation zero for elements in their stablest form?

It is favorable for a substance to be at its most stable state, therefore when a substance reaches that, it is going to want to maintain that most stable state. This means that it wont spontaneously progress in either direction, it will just stay in its current form.

Hope that helps!
by Michelle Chernyak 1J
Wed Feb 14, 2018 10:07 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibb's Energy and Work
Replies: 4
Views: 338

Re: Gibb's Energy and Work

w=-PdeltaV applies to the work done in a irreversible expansion and yes both irreversible and reversible processes do expansion work, there are just two different equations used to solve for w.
by Michelle Chernyak 1J
Wed Feb 14, 2018 10:01 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: heat vs thermal energy [ENDORSED]
Replies: 2
Views: 160

Re: heat vs thermal energy [ENDORSED]

Thermal energy is q while the heat required to raise a substance to a certain temperature is the specific heat capacity. Based off of this, the first is asking for q in q=mCdeltaT and the second is asking for the C.
by Michelle Chernyak 1J
Wed Feb 14, 2018 9:58 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: delta S total and delta G
Replies: 2
Views: 324

Re: delta S total and delta G

delta S total is the total entropy change that occurs during a reaction, while delta G is the total change in gibbs free energy that dictates if the reaction is spontaneous or not. In order to solve for delta G, we can often use delta S in the equation, delta G= deltaH -Tdelta S
by Michelle Chernyak 1J
Sun Feb 04, 2018 8:24 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: thermodynamically favored
Replies: 6
Views: 739

thermodynamically favored

When it says a reaction is thermodynamically favored, it is referring to just the enthalpy or the free energy?
by Michelle Chernyak 1J
Sun Feb 04, 2018 8:12 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: state functions
Replies: 3
Views: 102

state functions

Because all of the function in deltaG= deltaH -TdeltaS are state functions, does that mean that free energy is a state function as well?
by Michelle Chernyak 1J
Sun Feb 04, 2018 8:08 pm
Forum: Phase Changes & Related Calculations
Topic: enthalpy and entropy when it comes to spontaneous reactions
Replies: 6
Views: 227

enthalpy and entropy when it comes to spontaneous reactions

What carries more weight when determining if a reaction is spontaneous, the enthaply of the reaction (if it is endothermic or exothermic) or the entropy of the reaction? Or do they carry the same weight?
by Michelle Chernyak 1J
Sun Feb 04, 2018 8:06 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: combustion
Replies: 4
Views: 169

combustion

This question maybe really stupid but is it possible to just subtract the enthalpies of formation of the products from the enthapies of formation of the reactants when doing a combustion problem?
by Michelle Chernyak 1J
Sun Feb 04, 2018 8:03 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond enthalpies vs. enthalpy of formation
Replies: 1
Views: 85

Bond enthalpies vs. enthalpy of formation

Why do you subtract products minus reactants for enthalpies of formation but do reactants minus products for bond enthalpies?
by Michelle Chernyak 1J
Wed Jan 24, 2018 8:09 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Homework question 8.41
Replies: 4
Views: 186

Homework question 8.41

Hi, I'm struggling with the set up for this question (8.41). I thought I knew how to do it, ( I set -q_ice=q_water) but my answer is off by a little bit. Can anyone help out please?
by Michelle Chernyak 1J
Wed Jan 24, 2018 5:27 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Question regarding 8.39 homework question
Replies: 5
Views: 222

Question regarding 8.39 homework question

The question (8.39) is "how much heat is needed to convert 80.0 g of ice at 0.0C into liquid water at 20.0C?"

I understand how to do the problem but I don't understand why we need to employ the specific heat capacity of liquid water rather than ice. Can someone please explain that to me?
by Michelle Chernyak 1J
Wed Jan 24, 2018 1:33 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Question about today's lecture 1/24/18
Replies: 1
Views: 99

Question about today's lecture 1/24/18

In today's lecture, Dr. Lavelle stated that in the isothermal reversible reaction, the gas expanding against the vacuum is exerting work. This confused me because I thought that with a vacuum, there is no opposing force, therefore work cannot be done because work= opposing force X distance. Can some...
by Michelle Chernyak 1J
Wed Jan 17, 2018 10:18 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Work in relation to pressure and volume
Replies: 1
Views: 97

Work in relation to pressure and volume

Why does a change in volume at constant pressure result in a negative work?
by Michelle Chernyak 1J
Wed Jan 17, 2018 10:15 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Celsius vs Kelvin with heat capacities [ENDORSED]
Replies: 3
Views: 222

Celsius vs Kelvin with heat capacities [ENDORSED]

In the book, it seems as though they sometimes use Celsius and kelvin interchangeably without applying a conversion when referring to heat capacities. Why is that?
by Michelle Chernyak 1J
Wed Jan 17, 2018 10:08 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Specific Heat capacity
Replies: 2
Views: 124

Specific Heat capacity

When there are two substances present in a calorimeter or the calorimeter is made up of a certain material, how do we know which specific heat capacity to use?

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