Search found 30 matches
- Sun Mar 17, 2019 12:48 am
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: K vs k1/k'1
- Replies: 6
- Views: 1457
Re: K vs k1/k'1
I do not think it really matters which one you write it as. It is however important to know that K is equal to k1/k'1 if you are only given the values of k1 and k'1 and not a value for K.
- Thu Mar 14, 2019 9:50 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Hydronium
- Replies: 2
- Views: 298
Re: Hydronium
If there are hydronium ions in your balanced redox reaction, they should be included in your cell diagram.
- Mon Mar 11, 2019 12:43 am
- Forum: Zero Order Reactions
- Topic: Integration/Derivation
- Replies: 3
- Views: 508
Re: Integration/Derivation
I do not believe that derivation/integration would be asked of us, simply how to apply the derived formulas to problems.
- Mon Mar 11, 2019 12:41 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Spontaneous Reaction
- Replies: 5
- Views: 742
Re: Spontaneous Reaction
I am also confused. I understand that delta H would be negative if you are freezing and thus losing heat, but wouldn't delta S also be negative if you are losing entropy going from a liquid to a solid? Thanks in advance!
- Mon Mar 11, 2019 12:07 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell Potential
- Replies: 2
- Views: 287
Re: Cell Potential
You would want to use a cathode with the weakest reducing power (strongest oxidizing power) and an anode with the weakest oxidizing power (strongest reducing power).
- Mon Mar 11, 2019 12:04 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell Diagram
- Replies: 3
- Views: 359
Re: Cell Diagram
H+ is included in the cell diagram, but H2O (l) and electrons are not.
- Sun Mar 10, 2019 11:17 pm
- Forum: First Order Reactions
- Topic: Half-Life
- Replies: 7
- Views: 719
Re: Half-Life
Typically we would use the half-life formula to determine how long an element has been decaying.
- Sun Mar 10, 2019 11:08 pm
- Forum: General Rate Laws
- Topic: Rate Laws
- Replies: 8
- Views: 833
Re: Rate Laws
I think he shows us the derivation to establish some kind of fundamentals, but it really just confuses the [censored] out of me. I don't think we would ever be asked to derive them on a test, just to apply them to problems similar to homework and tests.
- Sat Mar 09, 2019 4:50 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: 6M. 1 7th Edition
- Replies: 2
- Views: 278
Re: 6M. 1 7th Edition
This sounds like the question is just trying to be tricky. We were taught to write anode on the left and cathode on the right.
- Sat Mar 09, 2019 4:47 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Calculating E naught
- Replies: 5
- Views: 906
Re: Calculating E naught
Given the reduction half reactions, you will use the appendix to find E naught values. The lower E naught value is the anode because it is the stronger reducing agent. Then, to get E naught of the cell you do cathode - anode = E naught cell
- Sat Mar 09, 2019 4:05 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: negative and k
- Replies: 3
- Views: 410
Re: negative and k
K cannot be negative because you can't have a negative concentration
- Wed Feb 27, 2019 8:30 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Galvanic Cell Diagram [ENDORSED]
- Replies: 3
- Views: 479
Re: Galvanic Cell Diagram [ENDORSED]
Molecules of the same phase in the cell diagram are written in the order: oxidized, reduced
- Sun Feb 24, 2019 1:41 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Oxidation and Reduction
- Replies: 3
- Views: 330
Re: Oxidation and Reduction
I think the most important thing is that the electrons are on opposite sides in reduction vs oxidation half reactions, but given that that is how we did it in class I assume that is how we should do it on an exam.
- Sun Feb 24, 2019 1:38 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: n value
- Replies: 11
- Views: 869
Re: n value
n is moles so I assume it will either be a given value or we will need to convert to moles from a given mass of a compound or element.
- Sun Feb 24, 2019 1:37 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Spontaneous cell reaction
- Replies: 2
- Views: 322
Re: Spontaneous cell reaction
Because the equation is delta G = -nFE, a positive cell potential (or E value) results in a negative delta G, and thus a spontaneous reaction.
- Mon Feb 18, 2019 5:53 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gibbs Free Energy
- Replies: 4
- Views: 418
Re: Gibbs Free Energy
K is the equilibrium constant. Concentration of products at equilibrium over the concentration of reactants at equilibrium.
- Mon Feb 18, 2019 5:52 pm
- Forum: Van't Hoff Equation
- Topic: Van't Hoff Equation
- Replies: 4
- Views: 428
Re: Van't Hoff Equation
I'm pretty sure R is the ideal gas constant
- Mon Feb 18, 2019 5:43 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Entropy
- Replies: 3
- Views: 426
Re: Entropy
Entropy is a state function and thus increases or decreases in a phase change. As said above, solids have the lowest entropy, then liquid, and gases have the highest entropy.
- Sun Feb 03, 2019 10:39 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Open vs Closed System
- Replies: 13
- Views: 4458
Re: Open vs Closed System
In a closed system, only energy can exchange with surroundings. An example is a sealed beaker of water. You cannot change the volume but you can heat the container because it isn't insulated and thus change the energy.
- Sun Feb 03, 2019 10:27 pm
- Forum: Calculating Work of Expansion
- Topic: Work sign changes
- Replies: 3
- Views: 376
Re: Work sign changes
I believe this is because the formula is w = - P (delta V). If it is expansion, delta V will be positive and thus work negative. In compression delta V is negative and thus work is positive.
- Sun Feb 03, 2019 10:04 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Quiz 1 Number 3c
- Replies: 6
- Views: 622
Re: Quiz 1 Number 3c
The units should be mol/L (Molarity) because it's asking for the concentration.
- Sun Jan 27, 2019 5:21 pm
- Forum: Ideal Gases
- Topic: Calculating partial pressure
- Replies: 4
- Views: 380
Re: Calculating partial pressure
You may be able to if you are given a concentration: n/V, or moles/liter.
- Sun Jan 27, 2019 3:36 pm
- Forum: Ideal Gases
- Topic: Approximations for ICE
- Replies: 20
- Views: 1529
Re: Approximations for ICE
You can use approximations if the Ka value is less than 1x10^-3. You should check to see that it was appropriate to use approximation by seeing if the equilibrium concentration is less than 5% of the initial concentration.
- Sun Jan 27, 2019 3:31 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: pKa values
- Replies: 3
- Views: 440
Re: pKa values
I'm not sure if there is an index of these values. They should be given to you by problem or the problem may tell you to look at a table to find the pKa or Ka values. Also if you are given the Ka you know the pKa and vice versa.
- Sun Jan 20, 2019 4:10 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Bars vs. Molarity
- Replies: 5
- Views: 571
Re: Bars vs. Molarity
bars are a unit of pressure just like atm or TORR
- Sun Jan 20, 2019 4:06 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Autoprotolysis
- Replies: 3
- Views: 299
Re: Autoprotolysis
The equation is 2H2O → H3O + + OH-. The significance is that shows that water is amphoteric (able to react as an acid and a base).
- Sun Jan 20, 2019 3:33 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: HW Q
- Replies: 2
- Views: 182
Re: HW Q
You have to dilute the solution by multiplying .025M(200ml/250ml). Then, take the negative log of that new concentration and you should get the correct pH.
- Sun Jan 13, 2019 3:11 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Equations
- Replies: 6
- Views: 471
Re: Equations
Kp = Kc x (RT) ^ stoichiometric coefficient
In general, Kp uses partial pressures and Kc uses concentrations
In general, Kp uses partial pressures and Kc uses concentrations
- Sun Jan 13, 2019 2:19 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Difference between Kc, Kp, and K
- Replies: 2
- Views: 1102
Re: Difference between Kc, Kp, and K
Kc: concentration of products over concentration of reactants when at equilibrium
Kp: partial pressures of products over partial pressures of reactants when at equilibrium
Kp: partial pressures of products over partial pressures of reactants when at equilibrium
- Sun Jan 13, 2019 2:12 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: ICE table question
- Replies: 2
- Views: 257
Re: ICE table question
So far we have typically used ICE tables to calculate equilibrium concentrations of the products and reactants when given a Kc and initial concentrations.