## Search found 30 matches

Wed Mar 14, 2018 2:49 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Catalyst and Intermediate
Replies: 5
Views: 381

### Catalyst and Intermediate

In a mechanism reaction, can you ideally have both catalysts at the beginning and intermediates throughout the same reaction?
Wed Mar 14, 2018 2:48 pm
Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
Topic: Electrolysis
Replies: 1
Views: 237

### Electrolysis

Is all we need to know for electrolysis is that it takes a external supply of energy/current supply to drive a non-spontaneous reaction? Also, that it takes electrical energy to chemical energy? What else would we be required to know?
Wed Mar 14, 2018 2:46 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Calculating Standard Cell Potential
Replies: 2
Views: 165

### Calculating Standard Cell Potential

Just for confirmation, there are two ways to calculate the standard cell potential. For example if you were given the following: A --> A +1 + 1e - E = 0.70 V B --> B +2 + 2e - E= -0.20 V You can calculate the standard cell potential by determining that the highest E value will be the cathode and the...
Wed Mar 07, 2018 3:58 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Elementary Steps for Reaction Mechanisms
Replies: 2
Views: 154

### Elementary Steps for Reaction Mechanisms

When given a problem about reaction mechanisms, will we be given the elementary steps or will we have to figure these steps out ourselves? If we do have to figure out the steps by hand, how would we approach a problem like this?
Wed Mar 07, 2018 3:55 pm
Forum: General Rate Laws
Topic: Psuedo Rate Laws
Replies: 1
Views: 124

### Psuedo Rate Laws

I understand the various steps that need to occur to experimentally determine the order of each reactant but will we ever be asked to do these calculations by hand?
Wed Mar 07, 2018 3:51 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Pre-Equilibrium Mechanism Reaction
Replies: 1
Views: 85

### Pre-Equilibrium Mechanism Reaction

If given a mechanism reaction and we are asked whether or not the reaction is valid, what will be given in order to solve out the problem?
Thu Mar 01, 2018 11:07 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Units for the Different Order Reactions [ENDORSED]
Replies: 2
Views: 208

### Units for the Different Order Reactions[ENDORSED]

If the units for rate is always mols*L-1*s-1, how can we determine the units of our final answer depending on the different order reactions?
Thu Mar 01, 2018 11:03 pm
Forum: General Rate Laws
Topic: Instantaneous Rate vs. Unique Rate [ENDORSED]
Replies: 2
Views: 142

### Instantaneous Rate vs. Unique Rate[ENDORSED]

What is the difference between instantaneous rate and unique rate? I understand that instantaneous rate is the rate at a specific moment of time but what is unique rate and how is it relevant to rate laws?
Thu Mar 01, 2018 11:02 pm
Forum: Zero Order Reactions
Topic: Graph of Zero Order vs First and Second Order [ENDORSED]
Replies: 3
Views: 204

### Graph of Zero Order vs First and Second Order[ENDORSED]

Will we ever be asked to determine the order of a reaction just by looking at a graph given to us?
Wed Feb 21, 2018 1:09 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagram Order
Replies: 3
Views: 179

### Cell Diagram Order

I understand the general idea of what the cell diagram should look like but I was wondering if the order of the species on the anode or the cathode side matters. For example, if one had a species of H 2 and H + for the anode, does it matter which is written first on the left side of the cell diagram?
Wed Feb 21, 2018 1:07 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Picking between the different applications of the Nernst Equation
Replies: 2
Views: 221

### Picking between the different applications of the Nernst Equation

Shown in class, there are multiple versions of the Nernst equations, the one that use the base 10 logarithm and the other using the natural log. Is there a specific one we should use for certain reactions or can we use both interchangeably ?
Wed Feb 21, 2018 1:03 pm
Forum: Balancing Redox Reactions
Topic: Defining Cathodes and Anodes through standard cell potential
Replies: 2
Views: 166

### Defining Cathodes and Anodes through standard cell potential

Just to confirm. When comparing a species couple, to determine which would be the anode and which would be the cathode, the higher/more positive standard potential would represent the cathode while the lower/more negative standard potential would represent the anode.
Wed Feb 14, 2018 11:54 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Change in Entropy for the Surroundings vs. System
Replies: 2
Views: 286

### Change in Entropy for the Surroundings vs. System

Is there a conceptual reason why $\Delta S_{surround} = -\frac{\Delta H_{system}}{T}$ is negative compared to $\Delta S_{system} = \frac{\Delta H_{system}}{T}$ which is a positive value?
Wed Feb 14, 2018 11:49 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Total Change in Entropy [ENDORSED]
Replies: 1
Views: 123

### Total Change in Entropy[ENDORSED]

Is it true that when you have a process that is reversible or a process that is at equilibrium, your total change in entropy is equal to zero? And if so, why?
Wed Feb 14, 2018 11:42 pm
Forum: Balancing Redox Reactions
Topic: Balancing Redox Reactions
Replies: 2
Views: 111

### Balancing Redox Reactions

When balancing redox reactions, do we always use water, hydrogens, and oxygens to balance our redox reactions?
Mon Feb 05, 2018 10:54 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Calculating Potential Difference between Electrodes
Replies: 3
Views: 175

### Calculating Potential Difference between Electrodes

Why is it that when we calculate the potential difference between electrodes, we take the limit as it approaches zero?
Mon Feb 05, 2018 10:52 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Standard Molar Entropies
Replies: 1
Views: 127

### Standard Molar Entropies

When calculating standard molar entropies, does this just mean the total or net entropy value of the entire reaction per mole?
Mon Feb 05, 2018 10:48 pm
Forum: Van't Hoff Equation
Topic: Friday Lecture:
Replies: 2
Views: 326

### Re: Friday Lecture:

He also introduced equation for the Difference of Van't Hoff Equation which is taken to calculate two different K (equilibrium constant) values assuming that $\Delta S^{\circ}$ and $\Delta H^{\circ}$ are constant.
Mon Jan 29, 2018 11:45 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Degeneracy (W) [ENDORSED]
Replies: 8
Views: 575

### Re: Degeneracy (W)[ENDORSED]

Degeneracy, like previously stated, is the number of states a system can have. The more states, the higher its degeneracy. Moreover, it can be seen that the more complex a molecule is, the higher its degeneracy as well.
Mon Jan 29, 2018 11:35 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: Limit of Entropy as temperature approaching 0 K
Replies: 2
Views: 183

### Limit of Entropy as temperature approaching 0 K

Could someone explain the science/significance of taking the limit of entropy as temperature approaches 0 K. I understand that it is related to the idea of perfectly ordered materials but I am not entirely sure what that means.
Mon Jan 29, 2018 11:22 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Perfect Crystal in terms of Entropy
Replies: 2
Views: 97

### Perfect Crystal in terms of Entropy

I was wondering what the connection was between Entropy and the idea of a perfect crystal. I remember writing down how a perfect crystal has no impurities, no defects and can be cooled down to 0 K, but does this have to do with Entropy directly?
Wed Jan 24, 2018 2:19 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Assuming Temperature
Replies: 3
Views: 157

### Re: Assuming Temperature

When temperature is not specifically given, you can assume that the reaction is under standard conditions which means 25 degrees Celcius.
Wed Jan 24, 2018 2:17 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Mean Bond Enthalpy
Replies: 2
Views: 160

### Re: Mean Bond Enthalpy

Since mean bond enthalpy is the least accurate approach when calculating the total enthalpy of a reaction, the answer you receive from this method compared to a bond of formation method is decently close.
Wed Jan 24, 2018 2:14 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Energy of systems
Replies: 4
Views: 233

### Re: Energy of systems

You can also change the energy of a system by adding or removing the amount of substance in a system. This is primarily seen in open systems.
Tue Jan 16, 2018 9:51 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.31
Replies: 4
Views: 190

### Re: 8.31

It is also good to note that part (a) contains a monatomic ideal gas at a constant pressure while part (b) contains a monataomic ideal gas at constant volume.
Tue Jan 16, 2018 9:44 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Problem 8.75 (b)
Replies: 3
Views: 152

### Re: Problem 8.75 (b)

You can calculate all the bonds in both the reactants and the products and compare the difference, then calculate the bond ethalpies based off your findings. For example: CH 4 (g) + Cl 2 (g) ----> CH 3 Cl (g) + HCl (s) Reactants: C-H = 4 ; Cl-Cl = 1 Products: C-H = 3 ; C-Cl = 1 ; Cl-H = 1 (After you...
Tue Jan 16, 2018 9:43 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Free Expansion
Replies: 2
Views: 113

### Free Expansion

I was wondering if the only example of free expansion occurs in a vacuum. And if so, this is because the external pressure and work within this system is equal to zero.
Sat Jan 13, 2018 9:04 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Heat and Ethalpy
Replies: 3
Views: 168

### Re: Heat and Ethalpy

Heat is defined as q, which more specifically means the quantity of heat.
While Enthalpy is defined as H or delta H
Wed Jan 10, 2018 9:15 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Method 2 for Calculating Net Enthalpy
Replies: 2
Views: 117

### Re: Method 2 for Calculating Net Enthalpy

For standard equations, the reactants contain the molecules where you "break" bonds which are then used to "form" bonds on the product side of the reaction. Like previously stated, if you wished to "break" bonds with the products and "form" bonds with the reac...
Wed Jan 10, 2018 9:05 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Most Stable Form for an Element
Replies: 4
Views: 258

### Most Stable Form for an Element

When reading Section 8.17, I was wondering what the text meant by "the most stable form of each element" in terms of the standard enthalpies of formation. Does this mean the element's most simplest form? I was wondering if someone can clarify this concept or provide another definition to t...