## Search found 28 matches

Sat Mar 17, 2018 8:24 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: Boltzmann Distributions
Replies: 3
Views: 255

### Re: Boltzmann Distributions

My TA said to understand the concept behind it but not draw it.
Sat Mar 17, 2018 8:22 pm
Forum: General Rate Laws
Topic: number of mols effect on result
Replies: 2
Views: 294

### Re: number of mols effect on result

Number of moles affects the molarity of the reactant. Molarity is stated in the rate law. Depending on if moles increases of decreases, the molarity will be affected correspondingly.
Sat Mar 17, 2018 8:20 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Irreversible reactions
Replies: 1
Views: 248

### Re: Irreversible reactions

Why can you say that all irreversible reactions are spontaneous? Wouldn't you need to do the calculation? How can this be true in general?
Sat Mar 17, 2018 8:18 pm
Forum: Calculating Work of Expansion
Topic: Reversible vs Irreversible
Replies: 1
Views: 239

### Re: Reversible vs Irreversible

w= -PdeltaV takes into account that the external pressure is constant. It produces less work than a reversible reaction because for the reversible reaction, exceptions are made that allow the system to be viewed as not losing energy to other factors.
Sat Mar 10, 2018 2:10 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Heterogenous vs homogenous
Replies: 2
Views: 208

### Heterogenous vs homogenous

What determines if a heterogenous or homogenous catalyst should be used? What determines which is more effective?
Sat Mar 10, 2018 2:08 pm
Forum: *Enzyme Kinetics
Topic: Km
Replies: 1
Views: 309

### Km

How is Km a constant if it depends on concentrations of the enzyme and substrate?
Sat Mar 10, 2018 2:03 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Elementary Reaction Rate Law [ENDORSED]
Replies: 1
Views: 115

### Elementary Reaction Rate Law[ENDORSED]

When writing the rate law for each step of the mechanism, how do we know whether to include the reverse reaction? How do we know if it is too slow to effect the rate?
Sat Mar 03, 2018 8:20 pm
Forum: Second Order Reactions
Topic: Limiting Step
Replies: 7
Views: 634

### Re: Limiting Step

Since we haven't covered activation energy, do we always determine the slow step with the determined rate law? Is there any other method we have learned to determine the slow step?
Sat Mar 03, 2018 8:15 pm
Forum: General Rate Laws
Topic: Rate constant units
Replies: 2
Views: 209

### Rate constant units

How would you use units of the rate constant to identify order of the reaction? (What units of molarity and time raised to powers are associated with each order?)
Sat Mar 03, 2018 8:13 pm
Forum: First Order Reactions
Topic: Naming Orders
Replies: 3
Views: 252

### Re: Naming Orders

Even though the overall reaction order is second, I believe the individual orders would both be first.
Sat Feb 24, 2018 2:34 pm
Forum: General Rate Laws
Topic: Reaction Rate
Replies: 3
Views: 220

### Re: Reaction Rate

I think it means to only look at reactants at the start of the reaction (initial rate). Why does the reaction rate depend only on concentration of reactants, but the reaction rate can be set equal to products as well? How is it allowed to just focus on initial rate of reactants?
Sat Feb 24, 2018 2:31 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Galvanic vs electrochemical [ENDORSED]
Replies: 2
Views: 187

### Galvanic vs electrochemical[ENDORSED]

What is the difference between a galvanic and electrochemical cell? Or is galvanic a type of electrochemical cell?
Sat Feb 24, 2018 2:30 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Galvanic cell set up
Replies: 8
Views: 482

### Galvanic cell set up

Since a galvanic cell corresponds to a spontaneous reaction, is the left side of the cell diagram always the anode?
Sat Feb 10, 2018 3:31 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Standard State
Replies: 2
Views: 151

### Re: Standard State

If it is not in standard state, the values of deltaH differ because the temperature it is carried out at is not the temperature at which deltaH was measured. Therefore, the problem must be done in parts, separating the different temperatures and then combining all the values from each separate calcu...
Sat Feb 10, 2018 12:23 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Entropy being a state function
Replies: 2
Views: 156

### Entropy being a state function

Is it only important to note whether a reaction is irreversible or reversible if the variable we are solving for is not a state function and dependent on the path? So an entropy calculation of an irreversible reaction can be found using the reversible calculation and be the same?
Sat Feb 10, 2018 12:19 pm
Forum: Van't Hoff Equation
Topic: Derivation
Replies: 9
Views: 613

### Derivation

Since we go over derivations in lecture, is it necessary to know how to derive the equations we learn or simply how to use them?
Sun Feb 04, 2018 9:44 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: qrev
Replies: 3
Views: 232

### qrev

I'm confused as to what you insert for qrev in delta S? Is it -delta H or nCdeltaT? How do you know when to use which?
Sun Feb 04, 2018 9:37 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: System vs Surrounding
Replies: 4
Views: 313

### System vs Surrounding

In a given problem, how can you determine what is the system and what is the surroundings? When it states that a reaction occurs in the flask, how do you know that the surrounding is the flask, not the lab?
Sun Feb 04, 2018 9:36 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Spontaneity
Replies: 4
Views: 271

### Spontaneity

Can a reaction be determined as spontaneous or not only by delta G?
Sat Jan 27, 2018 9:32 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Internal energy as a state function
Replies: 3
Views: 242

### Internal energy as a state function

How can internal energy be a state function if work (a component of it) is not?
Sat Jan 27, 2018 9:31 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Systems in practice
Replies: 4
Views: 295

### Systems in practice

Can any system truly be isolated or adiabatic in practice or only in theory?
Sat Jan 27, 2018 9:27 am
Forum: Calculating Work of Expansion
Topic: Reversible vs Irreversible
Replies: 2
Views: 188

### Reversible vs Irreversible

Does a reversible reaction always correspond to an isothermal system (because it is constant T) and an irreversible to an isobaric system (because constant P)? Or does P within the system change, and therefore, is it not isobaric?
Sat Jan 20, 2018 12:18 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: ∆U = U final-U initial
Replies: 1
Views: 167

### ∆U = U final-U initial

When comparing U final and U initial to determine if ∆U is positive or negative, are there two different sets of values for q and w to calculate initial and final (since ∆U= q + w) or is it based on one set of data and then identified if final or initial was greater based on the value calculated?
Sat Jan 20, 2018 12:09 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: When to use Cv or Cp? to calculate change in Entropy
Replies: 3
Views: 1198

### Re: When to use Cv or Cp? to calculate change in Entropy

It depends on the type of system the reaction is being carried out in. If the problem specifies that it is isothermal, use Cp. It it is being carried out in isochoric, use Cv. If it is isobaric, use Cp to calculate q because pressure is not changing and change in volume will be accounted for in calc...
Sat Jan 20, 2018 11:59 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: ∆H equation
Replies: 3
Views: 227

### ∆H equation

For calculating ∆H, you solve for KJ(energy)/mol. The mol corresponds to n, but what constant corresponds to KJ?
Sat Jan 13, 2018 10:43 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: hw 8.49
Replies: 1
Views: 91

### Re: hw 8.49

Since the problem provides delta H and number of moles, there is a way to find delta U. It is possible to find delta T by the relationship between the C value that can be found in the table and the delta H value provided. Then solve for delta U by plugging in the values to the equation on page 280 (...
Sat Jan 13, 2018 10:31 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Different Molar Heat Capacities For Gases
Replies: 5
Views: 392

### Re: Different Molar Heat Capacities For Gases

For measuring heat transfer, the equation q=(n)(Cp)(delta T) relates molar heat capacity at a constant pressure with moles. If one were to change, the other would change accordingly. The relation changes if it is at constant volume instead.
Sat Jan 13, 2018 10:20 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Specific heat capacity vs molar heat capacity
Replies: 5
Views: 237

### Specific heat capacity vs molar heat capacity

Is molar heat capacity a type of specific heat capacity since it is per amount?