## Search found 26 matches

Fri Mar 17, 2017 3:12 pm
Forum: Phase Changes & Related Calculations
Topic: Boiling point and Delta H of fusion
Replies: 3
Views: 689

### Re: Boiling point and Delta H of fusion

"suppose you want to use methane gabs (delta h of combustion = -890. kJ/mol^-1) to boil 50.0 mL of water at 25.0 degrees celsius. how many grams would need to be combusted to generate the required heat?" when it says boiled, are we supposed to interpret this as all of the water turning int...
Fri Mar 17, 2017 1:32 pm
Forum: Phase Changes & Related Calculations
Topic: Boiling point and Delta H of fusion
Replies: 3
Views: 689

### Boiling point and Delta H of fusion

Do we generally take account for the enthalpy of fusion when boiling a liquid? In one of the practice questions, it doesn't include the enthalpy of fusion to calculate the total amount of heat. The solutions only calculated for the change of temperature. why is this?
Thu Mar 16, 2017 11:18 am
Forum: *Constitutional and Geometric Isomers (cis, Z and trans, E)
Topic: Practice Problems
Replies: 23
Views: 2878

### Re: Practice Problems

thank you!
Wed Mar 15, 2017 9:40 pm
Forum: *Constitutional and Geometric Isomers (cis, Z and trans, E)
Topic: Practice Problems
Replies: 23
Views: 2878

### Re: Practice Problems

Have the solutions for problem set 2 been posted already?
Tue Mar 14, 2017 8:56 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Q2B on 2008 Final
Replies: 1
Views: 313

### Re: Q2B on 2008 Final

yeah pretty much! the equation come from delta G = -RTln(k). You would then solve for "k" and get k = e^[-delta G/(RT)]. You then set up a ratio of the two systems mentioned and solve using the division rules of e
Sat Mar 11, 2017 8:24 pm
Forum: General Rate Laws
Topic: Pre-Equilibrium Approach for Molecules with Exponents
Replies: 1
Views: 249

### Pre-Equilibrium Approach for Molecules with Exponents

Is the pre-equilibrium approach still possible to calculate for intermediates that have a coefficient in the rate limiting step? for example, how would you calculate the rate law for this, considering that the second step is the slow step:

Tue Mar 07, 2017 10:08 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalysts and Drawing Transition States
Replies: 1
Views: 296

### Catalysts and Drawing Transition States

How would we draw the transition state of a reaction that involves a catalyst? Would the catalyst even be included in the drawing?
Tue Mar 07, 2017 9:18 am
Forum: *Cycloalkanes
Topic: Determining the Dominance between a Cycloalkane and a Long Carbon Chain
Replies: 3
Views: 553

### Re: Determining the Dominance between a Cycloalkane and a Long Carbon Chain

For this case, what would the name be?
Mon Mar 06, 2017 3:34 pm
Forum: *Cycloalkanes
Topic: Determining the Dominance between a Cycloalkane and a Long Carbon Chain
Replies: 3
Views: 553

### Determining the Dominance between a Cycloalkane and a Long Carbon Chain

In terms of figuring out the root object within a structure, what happens when a main part of the cycloalkane is part of the long carbon chain and the carbon chain is dominant? How would we name this? Would we say that the long carbon chain is composed of 12 carbons or 11? Screen Shot 2017-03-06 at ...
Thu Mar 02, 2017 10:54 am
Forum: *Free Energy of Activation vs Activation Energy
Topic: Delta G Double Dagger, Delta H Double Dagger, Delta S Double Dagger
Replies: 3
Views: 3379

### Delta G Double Dagger, Delta H Double Dagger, Delta S Double Dagger

Conceptually, why are delta G double dagger and delta H double dagger values always positive? Why could delta S double dagger be positive or negative? What are examples of situations for pos/neg situations for delta s double dagger?
Wed Mar 01, 2017 8:28 pm
Forum: *Organic Reaction Mechanisms in General
Topic: Concept of pseudo equilibrium
Replies: 1
Views: 2729

### Concept of pseudo equilibrium

When examining a reaction with one step, what does it mean when the slowest step is at pseudo equilibrium? Does this refer to the inability for products to overcome the transition state so they end up becoming reactants again? This is in correlation to reaction profiles and delta G.
Sat Feb 25, 2017 8:40 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: relationship between Temperature and rate constants
Replies: 1
Views: 369

### Re: relationship between Temperature and rate constants

From my understanding, the question shows that kinetic energy would be predominant at low temperatures since the activation required for the reaction to happen is so low that it won't take much kinetic energy for things to occur. I don't think this refers to the rate constant becoming larger in this...
Mon Feb 20, 2017 12:06 pm
Forum: First Order Reactions
Topic: Concept of Half Life [ENDORSED]
Replies: 3
Views: 478

### Re: Concept of Half Life[ENDORSED]

i believe there would be a trend since the half life of a first order reaction depends on the reaction constant. We will go over the arrhenius equation later on which will show how activation energy, temperature, and collision frequency all affect the rate constant, thus affecting the half life. and...
Mon Feb 20, 2017 12:03 pm
Forum: Zero Order Reactions
Topic: Concept of Zero Order
Replies: 5
Views: 2138

### Concept of Zero Order

Conceptually, second order is based on two molecules or atoms colliding and reacting with each other. First order would include radioactive decay of one object. What would the process be for something of zero order?
Sun Feb 19, 2017 12:02 am
Forum: First Order Reactions
Topic: Concept of Half Life [ENDORSED]
Replies: 3
Views: 478

### Concept of Half Life[ENDORSED]

Conceptually, how would you explain why a first order half life does not depend on the initial concentration?
Fri Feb 17, 2017 6:49 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Calculating reaction rates from initial concentrations
Replies: 1
Views: 300

### Calculating reaction rates from initial concentrations

Usually when we carry out the ratios, we get whole numbers that are pretty straight forward. Will there ever be a situation where we won't get a reaction order as a whole number? If so, what do we do?
Fri Feb 10, 2017 10:51 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Different Forms of Nernst Equations
Replies: 1
Views: 709

### Re: Different Forms of Nernst Equations

we can use the equations interchangeably! they may give answers that are a bit off from each other, but both answers are technically correct
Mon Feb 06, 2017 7:44 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Life Question! [ENDORSED]
Replies: 2
Views: 472

### Re: Life Question![ENDORSED]

Oh that makes a lot of sense! Thank you! To add onto this question, I was also wondering about something that question 9.107 touched a little upon within our homework. In terms of evolutionary biology, how can we explain how complex structures formed from basic components (ex. cells to tissue, tissu...
Sun Feb 05, 2017 9:00 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Life Question! [ENDORSED]
Replies: 2
Views: 472

### Life Question![ENDORSED]

According to the Second Law of thermodynamics, "the total entropy of an isolated system always increases over time, or remains constant." Considering this, how do we explain the intricacy and detail of the earth we live in? As one example, plants are formed with the various parts they need...
Fri Feb 03, 2017 12:11 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Winter 2014 Midterm Question 5C
Replies: 1
Views: 219

### Winter 2014 Midterm Question 5C

The question asks to distinguish state and path functions between a set of variables (w, G, q, E, S). It mentions that E is a path function, but we learned in class that it is a state function. Is this question referring to electrode potential or a different value of E?
Sun Jan 29, 2017 8:53 pm
Forum: Administrative Questions and Class Announcements
Topic: Found Periodic Table
Replies: 1
Views: 207

### Found Periodic Table

Someone left their periodic table during one of the UA office hours today in hedrick. If you're looking for it, it should still be at the front desk
Sun Jan 29, 2017 9:59 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Quiz 1 #9
Replies: 1
Views: 276

### Quiz 1 #9

For this question, I thought entropy was supposed to be a state function, but the answer to this question should be "delta G and delta S of the system." Why isn't delta S of the surroundings equal to zero?
Tue Jan 24, 2017 7:21 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Entropy and Irreversible and Reversible Systems
Replies: 1
Views: 228

### Entropy and Irreversible and Reversible Systems

Why does the equation for the change in entropy (q/T) include the "q" of only a reversible reaction? What's the difference between entropies of reversible and irreversible reactions? How would we calculate the entropy of an irreversible reaction?
Mon Jan 16, 2017 5:27 pm
Forum: Phase Changes & Related Calculations
Topic: Different enthalpy of vaporizations for water
Replies: 3
Views: 367

### Different enthalpy of vaporizations for water

On page 284 in the textbook, there are two listed enthalpy of vaporizations for water. Why is this the case? If this is already the standard enthalpy of physical change, shouldn't 25 degrees Celsius already by assumed? When should the 40.7 degrees Celsius value be used?
Mon Jan 16, 2017 12:37 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: When can we assume that temperature is 298K?
Replies: 1
Views: 340

### When can we assume that temperature is 298K?

For number 8.117, we need to use the equation, delta U= delta H -(delta n)*R*T. When is it ok to assume that we should use standard temperature for T? Under what contexts can we use 298K when answering problems?
Thu Jan 12, 2017 11:34 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: varying equations for heat capacity
Replies: 1
Views: 186

### varying equations for heat capacity

For clarification, I was wondering why there were multiple equations for heat capacity in terms of constant volume, constant pressure, and whether looking at an atom, linear molecule, or nonlinear molecule. Why does something with constant pressure have a higher heat capacity than that of something ...