## Search found 47 matches

Sat Mar 17, 2018 1:09 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: delta G
Replies: 1
Views: 262

### delta G

Is delta G the amount of energy free to do work(ie max work) only at standard G or any G? or is it when temp and pressure are constant?
Sat Mar 17, 2018 12:46 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Concentration cell
Replies: 1
Views: 148

### Concentration cell

for a concentration cell the E standard, Delta G standard and K will be 0 but delta G(not standard), E cell and Q will have some value if concentration is different at anode and cathode?
Wed Mar 14, 2018 9:55 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: ln vs log
Replies: 1
Views: 156

### ln vs log

when do we use the Erxn equations containing ln and when do we use the Erxn equation using log? On contains (RT/nF)lnQ and the other one is (0.05916/n)logQ.
Wed Mar 14, 2018 5:12 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: electro motive force
Replies: 1
Views: 138

### electro motive force

What is electro motive force and when is potential of a cell maximum?
Wed Mar 14, 2018 5:11 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: complex molecules
Replies: 8
Views: 625

### complex molecules

Do complex molecules have higher or lower molar entropy than simple molecules and why?
Wed Mar 14, 2018 5:10 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: thermodynamically stable
Replies: 1
Views: 188

### thermodynamically stable

for a thermodynamically stable reaction what will be the signs of delta H, deltaS and delta G?
Wed Mar 14, 2018 5:08 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: reversible and perfect system
Replies: 1
Views: 291

### reversible and perfect system

Is a reversible system the same as a perfect system because in both deltaS system= -delta S of surrounding?
Wed Mar 14, 2018 5:07 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: 2nd law
Replies: 2
Views: 330

### 2nd law

When asked to write the second law of thermodynamics would we explain the delta S for reversible and irreversible processes? and for a reversible does it have to be isothermal reversible for delta Stotal to be 0 or can it simply be just reversible?
Wed Mar 14, 2018 5:00 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: endothermic reaction.
Replies: 5
Views: 348

### endothermic reaction.

IN an endothermic reactions the forward Ea is greater than the reverse Ea so will it favor reactants or products?
Sun Mar 11, 2018 7:30 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Reversible or irreversible?
Replies: 2
Views: 390

### Reversible or irreversible?

Suppose that 50.0 g of H2O(l) at 20.0 C is mixed with
65.0 g of H2O(l) at 50.0 C at constant atmospheric pressure
in a thermally insulated vessel. Calculate S and Stot for the
process.
since delta T is 0 is it reversible or irreversible?
Thu Mar 08, 2018 7:54 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: to find k
Replies: 4
Views: 354

### to find k

To find the k from experimental data do we have to find the k from each experiment and then find its average? Or just any one experiment to find k?
Thu Mar 08, 2018 4:19 pm
Forum: Zero Order Reactions
Topic: graph of 0 order
Replies: 10
Views: 788

### graph of 0 order

What would the differential rate law graph of 0 order reactions look like? how would we graph [A]o against the initial rates? would it be a positive slope negative slope or a line parallel to x or y axis?
Wed Mar 07, 2018 11:57 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: determine K
Replies: 3
Views: 368

### Re: determine K

yes I know how to calculate in terms of A but what about in terms of B?
Wed Mar 07, 2018 9:16 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: determine K
Replies: 3
Views: 368

### determine K

For the first-order reaction A -->3 B +C, when [A]o is
0.015 mol!L"1 , the concentration of B increases to 0.018 mol!L"1
in 3.0 min. What is the rate constant for the reaction expressed
as the rate of loss of B?
Wed Mar 07, 2018 9:10 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: To determine k
Replies: 2
Views: 320

### To determine k

2 A --> B + C, given that [A] is 0.153 mol!L"1 and that after 115 s the concentration of B rises to 0.034 mol!L"1.
In this we find At by subtracting 0.068 from Ao. but if B was a reactant and it was increasing would we add it instead of subtracting?
Wed Mar 07, 2018 8:22 pm
Forum: General Rate Laws
Topic: 15.13
Replies: 4
Views: 284

### 15.13

When 0.52 g of H2 and 0.19 g of I2 are confined to a 750.-mL reaction vessel and heated to 700. K... How come the volume of each is 0.750L. im confused is the total mixture 750ml or or each is 750ml because it says a reaction vessel so wont the total be 750ml? can somebody explain?
Sun Mar 04, 2018 10:53 am
Forum: First Order Reactions
Topic: half life
Replies: 3
Views: 254

### half life

What does n half lives mean?
Sun Mar 04, 2018 10:52 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: 0 order
Replies: 6
Views: 2171

### 0 order

what does the graph of 0 order look like?
Sun Mar 04, 2018 10:51 am
Forum: General Rate Laws
Topic: drivations
Replies: 2
Views: 222

### drivations

Will derivations be included in the test and final?
Thu Feb 22, 2018 9:28 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: K and Q at equilibrium
Replies: 5
Views: 368

### K and Q at equilibrium

At equilibrium is K=1? wouldnt that make Estandard 0? But if Q=1 is Q also at equilibrium? Wouldnt that make Erxn=Estandard?
Thu Feb 22, 2018 9:23 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: E rxn vs E standard at equilibrium [ENDORSED]
Replies: 2
Views: 283

### E rxn vs E standard at equilibrium[ENDORSED]

I know that Erxn at equilibrium is 0. At equilibrium is Erxn=Estandard? So is Estandard also 0 at equilibrium?
Mon Feb 19, 2018 8:42 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: PH meter
Replies: 3
Views: 238

### PH meter

can someone please explain what a PH meter is? An what all is known and what we are trying to find using the PH meter hence what is unknown?
Wed Feb 14, 2018 3:55 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Replies: 2
Views: 316

Does q=0 always imply that deltaT is 0 making deltaU 0?
Wed Feb 14, 2018 2:00 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Delta U as 0
Replies: 3
Views: 293

### Delta U as 0

For which different conditions is Delta U 0 making work=-q. I think deltaU is 0 in an isolated system, isothermal system, at equilibrium and when initial and final conditions are same. Is there any other time when delta U is 0? correct me if im wrong.
Tue Feb 13, 2018 8:11 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: change in pressure
Replies: 1
Views: 139

### change in pressure

in lyndons sample midterm in 3B how do we calculate the final pressure?
Tue Feb 13, 2018 8:06 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: q and change in T
Replies: 1
Views: 157

### q and change in T

When reaction is endothermic at q is positive is change in T always positive implying that Tfinal is greater than T initila and the temperature was increased?
Mon Feb 12, 2018 10:51 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Midterm
Replies: 2
Views: 212

### Midterm

for the midterm on Wednesday do we need to know how to derive any formulas because today in lecture Dr. Lavelle said derivations wont be on the test?
Mon Feb 12, 2018 10:48 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: comparing entropies
Replies: 1
Views: 151

### comparing entropies

In which of the following phase will the substance have higher entropy?
1. gas or aq phase
2. aq or solid phase
3. aq or liquid phase
Mon Feb 12, 2018 6:25 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: enthalpy vs standard
Replies: 2
Views: 164

### Re: enthalpy vs standard

what if the standard reaction takes place for 2 moles? eg 2H2+o2----> 2H20. do we also divide this by 2 to find enthalpy in KJ/mol?
Mon Feb 12, 2018 5:03 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: enthalpy vs standard
Replies: 2
Views: 164

### enthalpy vs standard

what is the difference between enthalpy of a reaction and the standard enthalpy of reaction? for which one do we have to divide it by moles to get it for per mole?
Sat Feb 10, 2018 11:33 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: entropy of irreversible and reversible reactions.
Replies: 2
Views: 235

### entropy of irreversible and reversible reactions.

Are the entropies of irreversible and reversible reactions the same? how are they related?
Sat Feb 10, 2018 11:30 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: system vs surroundings
Replies: 6
Views: 454

### system vs surroundings

if a beaker has a reaction taking place the system is the reaction but is the surroundings the beaker or the atmosphere? also if the beaker was immersed in a water bath the system will still be the reaction but what will the surroundings be? Is it the water bath or the beaker?
Sat Feb 10, 2018 11:28 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: closed vs isolated
Replies: 11
Views: 749

### closed vs isolated

Are the pressures and volumes constant in a closed and isolated system?
Sat Feb 10, 2018 11:27 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.117
Replies: 2
Views: 216

### 8.117

what is the delta(n)? I thought it was 2 but the solutions manual says it is 2/3 why is that?
Sun Feb 04, 2018 10:43 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: change in entropy with change in temperature
Replies: 2
Views: 165

### change in entropy with change in temperature

is deltaS=n*R*ln(T2/T1) or deltaS=n*C*ln(T2/T1)? because the book uses both. Also when do we know which one to use when?
Sat Feb 03, 2018 6:17 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: syllabus
Replies: 4
Views: 265

### syllabus

What chapters will be covered in the coming midterm? and will the new chapter that professor Lavelle teaches next week be included in the syllabus?
Fri Feb 02, 2018 4:45 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Midterm
Replies: 6
Views: 439

### Midterm

What exact parts of chapter 11 do we need to read through for the coming midterm?
Thu Jan 25, 2018 7:36 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: change in enthalpy
Replies: 2
Views: 153

### change in enthalpy

is delta(H)=delta(U)-delta(n)*R*T or delta(H)=delta(U)+delta(n)*R*T? Also is work -P*delta(V) or +P*delta(V)?
Thu Jan 25, 2018 5:40 pm
Forum: Phase Changes & Related Calculations
Topic: enthaply
Replies: 3
Views: 267

### enthaply

the enthalpy of vaporization is deltaH=Hvapor-Hliquid. What is the difference between deltaH and just H and where do we find the values for H(NOT deltaH!) of vapor or liquid of a substance?
Mon Jan 22, 2018 4:31 pm
Forum: Calculating Work of Expansion
Topic: expansion work
Replies: 2
Views: 180

### expansion work

in expansion work the volume increases. does the pressure change or is it constant at 1 atm?
Sun Jan 21, 2018 9:10 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Open System
Replies: 7
Views: 670

### Re: Open System

to change internal energy you can add or subtract matter to or from the system, do work on it or make it do work and add heat or subtract heat from it.
since it is specifically asking how to increase internal energy it can be done by adding heat to it, adding matter and doing work on it.
Sun Jan 21, 2018 9:04 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: bond enthalpies
Replies: 3
Views: 242

### bond enthalpies

In lecture Professor Lavelle said something about converting all products and reactants into gas form to use bond enthalpies. I did not understand what he meant. How do we convert something into gas?
Sun Jan 21, 2018 9:00 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: delta n
Replies: 3
Views: 1442

### delta n

How do we calculate delta n for a given equation? Is it number of moles of the products minus the number of moles of the reactants or the opposite? and do we include solid and liquid products and reactants or just gasses? and what if delta n is 0?
Sat Jan 20, 2018 10:21 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

### standard enthalpy of formation[ENDORSED]

I'm a little confused about the difference between enthalpy of formation and enthalpy of reaction? could someone explain please?
Sun Jan 14, 2018 5:30 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: living plant
Replies: 4
Views: 242

### living plant

Is a living plant an open, closed or isolated system? because a human being is. What about a dead plant?
Sun Jan 14, 2018 5:23 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Heating curves
Replies: 1
Views: 150

### Heating curves

In the book it says that "The steeper the slope of a heating curve, the lower is the heat capacity." why is this true? It also says that "The slope of a heating curve is steeper for a phase with a low heat capacity than for one with a high heat capacity." could someone explain th...
Thu Jan 11, 2018 7:52 am
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8019
Views: 1403735

### Re: Post All Chemistry Jokes Here

Why did the white bear dissolve in water?
Because it was polar!