## Search found 31 matches

Sat Mar 17, 2018 1:12 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Rate Laws and Catalysts
Replies: 1
Views: 163

### Re: Rate Laws and Catalysts

Yes, they are incorporated.
Fri Mar 16, 2018 10:53 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Review Session Question
Replies: 1
Views: 131

### Review Session Question

Question 2C on Lyndon's worksheet asked to explain the purpose of the platinum solid. I know he explained it during the session but I missed it so can someone summarize its purpose?
Fri Mar 16, 2018 10:49 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Porous Disks vs Salt Bridges
Replies: 1
Views: 253

### Porous Disks vs Salt Bridges

What is the difference between salt bridges and porous disks and the purpose of each one? How do we know which one is being used?
Sun Mar 11, 2018 5:00 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: HW 15.95
Replies: 2
Views: 171

### Re: HW 15.95

The two local minima represent the intermediates between transition states illustrated by the local maxima of the graph.
Sun Mar 11, 2018 4:58 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: SN2
Replies: 3
Views: 271

### SN2

What is the importance of studying SN2 reactions?
Sun Mar 11, 2018 4:48 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Calculating standard enthalpy [ENDORSED]
Replies: 3
Views: 431

### Re: Calculating standard enthalpy[ENDORSED]

The bond enthalpies are averages therefore, they are less accurate. This leads to different answers, but the numbers should not be too far from one another.
Sun Mar 04, 2018 10:15 pm
Forum: First Order Reactions
Topic: 15.23
Replies: 6
Views: 462

### Re: 15.23

Use the half life equation for first order reactions, t1/2=0.693/k (you can find the derivation on page 628). Using this equation and the information given, we can find the rate constant, k. The t1/2 is the time it takes for the concentration of A to decrease to half its original concentration, whic...
Sun Mar 04, 2018 10:11 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: 15.47
Replies: 1
Views: 159

### Re: 15.47

Essentially, you just cancel out any compounds that appear on the reactant and product sides. By doing this, you are getting rid of intermediate compounds that do not contribute to the overall reaction equation, but still play a role in the development of the final compounds.
Sun Mar 04, 2018 10:08 pm
Forum: General Rate Laws
Topic: Rate laws
Replies: 4
Views: 316

### Rate laws

Will we ever need to assume the order of a reaction? Are we always going to be told if a reaction is in the zero, first, or second order?
Sat Feb 24, 2018 11:05 pm
Forum: Second Order Reactions
Topic: 15.35
Replies: 2
Views: 215

### Re: 15.35

The equation is derived from A=k[A]2, shown in section 15.6 (page 630) of the textbook.
Wed Feb 21, 2018 11:54 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Finding Q
Replies: 2
Views: 317

### Re: Finding Q

I'm also confused with this one. When I exponentiated both sides to solve for Q, my answer was 3.27x106. Why does it only show 106 as the answer?
Wed Feb 21, 2018 11:46 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14.19
Replies: 2
Views: 218

### Re: 14.19

E°= E°(cathode) - E°(anode). The cell potential given (-0.689 V) is the E°, and you have to look for the E°(anode),0.34 V, which is the standard potential of the copper couplet. Solve for the E°(cathode). It seems that you were attempting to plug in the numbers to solve for the cell potential which ...
Sun Feb 18, 2018 7:08 pm
Forum: Balancing Redox Reactions
Topic: Balancing Redox Reactions
Replies: 4
Views: 462

### Balancing Redox Reactions

When balancing redox reactions, you add H+ to an acidic solution and OH- for a basic solution, right? Why do we not use H3O+?
Sun Feb 18, 2018 4:16 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: galvanic cells and voltaic cells
Replies: 2
Views: 143

### Re: galvanic cells and voltaic cells

I believe so. I think the electrochemical cell was just named after two different people.
Wed Feb 14, 2018 11:27 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hess's Law
Replies: 5
Views: 405

### Re: Hess's Law

Enthalpy is a state function/property.
Sun Feb 11, 2018 10:14 pm
Forum: Van't Hoff Equation
Topic: Reaction Coefficient, Q
Replies: 2
Views: 327

### Re: Reaction Coefficient, Q

Q, in comparison to K, tells us whether reaction is favors the products or reactants. When Q>K, the reaction favors reactants. When Q<K, the reaction favors the products. It's basically products/reactants, each component raised to the number of moles in the chemical formula.
Sun Feb 11, 2018 9:45 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Number of Bonds and Entropy
Replies: 3
Views: 228

### Number of Bonds and Entropy

Can entropy be increased/decreased based on whether a molecule has multiple bonds vs one? Can we use this information when comparing two molecules to determine which has a higher entropy?
Sun Feb 11, 2018 9:23 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: formula for temperature change
Replies: 1
Views: 142

### Re: formula for temperature change

The solution in the manual is incorrect. The correct solution is posted on the class website. The equation deltaS=nCln(T2/T1) is correct.
Sun Feb 04, 2018 11:46 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: test question 7 [ENDORSED]
Replies: 6
Views: 449

### Re: test question 7[ENDORSED]

What do you mean initial deltah? All of them were given on the equations sheet. Unless you were talking about the calculation of the phase change?
Sun Feb 04, 2018 11:38 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: maximum G
Replies: 3
Views: 214

### Re: maximum G

Adding on to this, during the lecture on 1/29, it was said that when G is a minimum, a system can no longer change as well. Why is this the case?
Sun Feb 04, 2018 11:18 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Friday Lecture Concept
Replies: 2
Views: 136

### Friday Lecture Concept

Can someone explain the difference between approaching problems that are at equilibrium vs the ones that are not based on Friday's lecture?
Sun Jan 28, 2018 1:27 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Gas Expansion [ENDORSED]
Replies: 3
Views: 275

### Gas Expansion[ENDORSED]

Can someone explain to me why even though deltaU=0, a gas can still expand?
Tue Jan 23, 2018 8:46 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Solve for reaction enthalpy using bond enthalpies
Replies: 1
Views: 118

### Re: Solve for reaction enthalpy using bond enthalpies

Use the standard enthalpies of formation method for 8.59. When using bond enthalpies, use table 8.6 and 8.7.
Tue Jan 23, 2018 8:35 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Reaction Enthalpies vs other methods
Replies: 2
Views: 169

### Re: Reaction Enthalpies vs other methods

The three methods are different ways to solve for the reaction enthalpies.
Sun Jan 21, 2018 9:51 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 8.99 Negative Specific Heat Capacity
Replies: 3
Views: 263

### 8.99 Negative Specific Heat Capacity

When solving for the final temperature, I used q=nC(Tf-Ti). Since we are using liquid water's specific heat capacity, 4.184 J/C*g would be plugged in for C, however in the solutions manual, it is negative. Why would it be negative in this case?
Sun Jan 21, 2018 4:29 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 8.67
Replies: 3
Views: 245

### Re: 8.67

The solutions manual had the reaction H2(g)+1/O2(g)->H20(l). How can we know what phase any product is in, especially H2O?
Sat Jan 20, 2018 1:33 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.51
Replies: 5
Views: 243

### Re: 8.51

The nitrogen gas can be included with the other products but it would not change the answer because the standard enthalpy formation of an element in its most stable form is equal to zero. Is there a specific part in the problem that you are having trouble with, or are you confused of how to approach...
Fri Jan 19, 2018 9:05 pm
Forum: Calculating Work of Expansion
Topic: 8.13- negative signs?
Replies: 2
Views: 128

### Re: 8.13- negative signs?

Since 947 kJ is being absorbed as heat by the surroundings, there must be a release of heat by the system itself. Therefore, this would result in a negative q.
Sun Jan 14, 2018 10:13 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Extensive vs Intensive Properties
Replies: 3
Views: 192

### Extensive vs Intensive Properties

Heat capacity is listed as an extensive property while specific heat capacity and molar heat capacity are listed as intensive properties. What is the difference between the two properties?
Sun Jan 14, 2018 10:04 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard State
Replies: 2
Views: 160

### Standard State

When solving for standard enthalpy, everything must be balanced and in its standard state in the reaction. How can we determine if something is in its standard state or not? Also what should we do if something is in fact not in its standard state?
Sat Jan 13, 2018 9:27 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: The 3 Methods for Calculating the Enthalpy of a Reaction
Replies: 4
Views: 282

### The 3 Methods for Calculating the Enthalpy of a Reaction

Dr. Lavelle went over three methods to solve for the enthalpy of different reactions. How do you know which method should be used to solve problems, or can any method be applied and it is just a matter of what is given and preferred?