Search found 55 matches
- Sun Mar 15, 2020 4:27 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Redox from cell diagram
- Replies: 6
- Views: 454
Re: Redox from cell diagram
The commas are used just because they the two molecules are in the same phase, but other than that, the molecule is being reduced.
- Sun Mar 15, 2020 4:25 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: adding platinum
- Replies: 8
- Views: 543
Re: adding platinum
Also, hydrogen electrodes need an inert metal such as platinum.
- Sun Mar 15, 2020 4:21 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: electrodes
- Replies: 3
- Views: 331
Re: electrodes
Is it safe to assume the hydrogen cell will be the anode because when calculating E cell standard, any positive number minus 0 will give a postive voltage?
- Sun Mar 15, 2020 4:17 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Flipping the anode
- Replies: 4
- Views: 358
Re: Flipping the anode
Flipping the anode identifies it as an oxidation reaction and allows us to cancels out the electrons with the cathode side when writing the equation.
- Sun Mar 15, 2020 4:14 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: nernst
- Replies: 5
- Views: 433
Re: nernst
When using the equation delta g = -nFe, e cell doesn't change and G does because of the n which is number of electrons transferred. Doubling the equation means increasing the number of electrons changing the value of G.
- Sun Mar 15, 2020 4:12 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: lnQ
- Replies: 22
- Views: 1352
Re: lnQ
Yes, and also make sure you write out the chemical reaction to find out which are the products and the reactants. Q = products/reactants.
- Sun Mar 15, 2020 4:08 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Test 2 Q6 part b ii
- Replies: 5
- Views: 381
Re: Test 2 Q6 part b ii
In addition, if you look at the equation for it, mass isn't accounted for anywhere.
- Sun Mar 15, 2020 3:59 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Affecting E cell
- Replies: 4
- Views: 394
Affecting E cell
How does changing concentration of reactants or products in a reaction effect E cell?
- Sun Mar 15, 2020 3:57 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell Diagram
- Replies: 11
- Views: 717
Re: Cell Diagram
If we have two molecules that are both solid, do we still have to use Pt or any other inert metal since they are in the same phase.
- Sun Mar 15, 2020 3:55 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: SHE
- Replies: 3
- Views: 320
Re: SHE
Also remember, when writing the cell diagram to add Pt or any other inert metal.
- Sun Mar 15, 2020 3:52 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Galvanic and voltaic cells
- Replies: 5
- Views: 397
Re: Galvanic and voltaic cells
They are the same. The difference comes when comparing them to electrolytic cell. A galvanic cell transforms chemical energy into electrical energy. An electrolytic cell converts electrical energy into chemical energy.
- Sun Mar 15, 2020 3:50 pm
- Forum: Balancing Redox Reactions
- Topic: Half rxns
- Replies: 27
- Views: 1371
Re: Half rxns
To the question : "Do you always add the H2O at opposite ends of where you have added OH or H+?"
You should be adding the h20 first and then adding OH or the H to the opposite side to balance the number of hydrogens.
You should be adding the h20 first and then adding OH or the H to the opposite side to balance the number of hydrogens.
- Sun Mar 15, 2020 3:47 pm
- Forum: Balancing Redox Reactions
- Topic: Half rxns
- Replies: 27
- Views: 1371
Re: Half rxns
I believe the side that has less hydrogens is the side you would add the OH because the purpose of adding it is to balance the number of hydrogen and this is only in basic solutions
- Sun Mar 15, 2020 3:44 pm
- Forum: Balancing Redox Reactions
- Topic: Oxidation/Reduction
- Replies: 17
- Views: 1131
Re: Oxidation/Reduction
To add on, the reducing agent is basically the molecules getting oxidized because it releases the electron that is added and reducing the other molecule. In the same sense, the oxidizing agent is the molecules getting reduced.
- Sun Mar 15, 2020 3:40 pm
- Forum: Balancing Redox Reactions
- Topic: Ecell values
- Replies: 12
- Views: 804
Re: Ecell values
In addition to the answers given, the reason we want to have a positive E cell is because it leads to a negative standard gibbs free energy which in turn means a positive value for entropy meaning the process is spontaneous.
- Sun Mar 15, 2020 3:35 pm
- Forum: Balancing Redox Reactions
- Topic: changing half reactions
- Replies: 6
- Views: 518
Re: changing half reactions
In the anode, usually the reverse of the given half reactions is occuring, because oxidation has to take place in the anode, right?
- Sun Mar 15, 2020 3:31 pm
- Forum: Balancing Redox Reactions
- Topic: Pt in Cell Diagram
- Replies: 14
- Views: 877
Re: Pt in Cell Diagram
Also, pt is used when dealing with hydrogen, and when two of the molecules are in the same phase such as both are aqueous solutions.
- Mon Mar 09, 2020 1:05 am
- Forum: General Rate Laws
- Topic: Making one reactant concentration small
- Replies: 3
- Views: 253
Re: Making one reactant concentration small
I think making of the reaction concentration smaller conceptually simulates the reactant not having as much of an affect on reaction rate allowing us to see kind of affect the other reactant has.
- Mon Mar 09, 2020 12:58 am
- Forum: General Rate Laws
- Topic: Enzyme saturation
- Replies: 6
- Views: 378
Re: Enzyme saturation
When enzyme is saturated, the increase in reaction rate levels off.
- Mon Mar 09, 2020 12:56 am
- Forum: General Rate Laws
- Topic: Difference between each order of reaction
- Replies: 3
- Views: 311
Re: Difference between each order of reaction
zero order reaction occurs at a constant rate. First order reaction rate is dependent on a reactant concentration and second order reaction rate is dependent on the square of a concentration of reactant.
- Mon Mar 09, 2020 12:53 am
- Forum: General Rate Laws
- Topic: Second order reaction
- Replies: 1
- Views: 1264
Second order reaction
What is relationship between the half life of the second order reaction and the concentration of the reactant?
- Mon Mar 09, 2020 12:45 am
- Forum: General Rate Laws
- Topic: Integrated Rate Laws
- Replies: 3
- Views: 218
Re: Integrated Rate Laws
It gives the concentration of reactants or products at anytime after the start of the reaction.
- Mon Mar 02, 2020 6:07 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: 6L.3 e
- Replies: 1
- Views: 113
6L.3 e
for 6L.3 part e, the for the half reaction in the anode the solutions manual says
Sn4+ + 2e- --> Sn2+, but the book problem doesn't show Sn2+, just Sn2 so aren't we supposed to assume it is two molecules of Sn instead a charge of 2+ so the balanced equation should be 2Sn4+ + 8e- -->Sn2?
Sn4+ + 2e- --> Sn2+, but the book problem doesn't show Sn2+, just Sn2 so aren't we supposed to assume it is two molecules of Sn instead a charge of 2+ so the balanced equation should be 2Sn4+ + 8e- -->Sn2?
- Sun Mar 01, 2020 10:50 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Free Energy and Cell Potential Relationship
- Replies: 3
- Views: 261
Re: Free Energy and Cell Potential Relationship
They are related through the equation deltaG = -nF(deltaE). G is Gibbs free energy, n is number of electrons transferred, F is faraday constant, and e is cell potential. If cell potential is negative then reaction is spontaneous and if it is positive then reaction is non spontaneous.
- Sun Mar 01, 2020 10:42 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cathode/Right & Anode/Left
- Replies: 7
- Views: 1004
Re: Cathode/Right & Anode/Left
To add on, the electrode at which the electrons enter and “add to” the cell is the cathode while the electrode at which the electrons leave the cell is the anode.
- Sun Mar 01, 2020 10:38 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Degree symbol
- Replies: 10
- Views: 971
Re: Degree symbol
The degree symbol indicates standard conditions for the process while without the degrees indicates whatever conditions the reaction is given in.
- Sun Mar 01, 2020 10:24 pm
- Forum: Balancing Redox Reactions
- Topic: Reducing Agent
- Replies: 5
- Views: 416
Reducing Agent
In a reaction, the reducing agent is the one that is oxidized and the oxidizing agent is the one that is reduced, right?
- Sun Mar 01, 2020 10:21 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Galvanic and Voltaic Cells
- Replies: 7
- Views: 491
Re: Galvanic and Voltaic Cells
They are the same. The difference is between electrochemical cells and galvanic cells. I believe electrochemical cells convert electrical energy into chemical energy while galvanic cells convert chemical energy into electrical energy.
- Sun Feb 23, 2020 11:14 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: G(not) and G
- Replies: 15
- Views: 711
Re: G(not) and G
Isn't the equation G = Gnot + RTlnQ ?
- Sun Feb 23, 2020 10:58 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Vant Hoff Equation
- Replies: 9
- Views: 732
Re: Vant Hoff Equation
The Vant Hoff equation can also be manipulated and use to calculate K at a different temperature if delta H is known.
- Sun Feb 23, 2020 10:46 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Porous disk
- Replies: 3
- Views: 210
Re: Porous disk
I think there should still be separation of the half reactions as long there is a method for the transport of ions or electrons
- Sun Feb 23, 2020 10:45 pm
- Forum: Balancing Redox Reactions
- Topic: Potential Difference
- Replies: 5
- Views: 420
Potential Difference
Can someone explain what is meant by potential difference?
- Thu Feb 20, 2020 2:09 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: 5G.15
- Replies: 5
- Views: 325
5G.15
for 5G.15 I keep getting -2.7 kj per mol but the answer says -27 kj per mol. Can someone tell me what I'm doing wrong is the answer key wrong.
- Sun Feb 16, 2020 11:13 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Reversible vs Irreversible
- Replies: 5
- Views: 404
Re: Reversible vs Irreversible
Irreversible processes are usually spontaneous and quick where as irreversible processes are slow and maintain equilibrium throughout the entirety of the process. However, I believe it will be clearly stated or inferred in any test.
- Sun Feb 16, 2020 11:08 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: What is residual entropy?
- Replies: 16
- Views: 4798
Re: What is residual entropy?
Yes, positional entropy is a result of change in volume, for example where a gas expands in a larger volume, while residual entropy is I believe a result of dipole dipole interactions.
- Sun Feb 16, 2020 11:04 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: spontaneity
- Replies: 39
- Views: 1846
Re: spontaneity
To add on, when Gibbs free energy is negative that means that according the equation for gibbs free energy, delta S or change in entropy is positive and if change in entropy is positive, it means that a process is spontaneous.
- Sun Feb 16, 2020 10:58 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Delta H
- Replies: 1
- Views: 130
Delta H
I forgot what Dr. Lavelle said in lecture, but it was something about delta H or the change in enthalpy doesn't change even if temperature changes? Can someone explain exactly what he said and what it means?
- Sun Feb 16, 2020 10:47 pm
- Forum: Van't Hoff Equation
- Topic: Van't Hoff Equation
- Replies: 3
- Views: 307
Re: Van't Hoff Equation
The equation is used to find out the change in the equilibrium constant, K, of a chemical reaction with the change in temperature and standard enthalpy change.
- Mon Feb 03, 2020 9:41 pm
- Forum: Phase Changes & Related Calculations
- Topic: -w vs w
- Replies: 15
- Views: 625
Re: -w vs w
When w is negative, it means that the system is doing work, while when w is positive, it means that the system is having work done on it.
- Sun Feb 02, 2020 10:41 pm
- Forum: Phase Changes & Related Calculations
- Topic: enthalpy change
- Replies: 2
- Views: 208
enthalpy change
Is enthalpy change for a reverse reaction the negative of the enthalpy change for the forward reaction?
- Sun Feb 02, 2020 10:29 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Volume and enthalpy
- Replies: 1
- Views: 84
Volume and enthalpy
If the volume stayed constant, could change in enthalpy still be equal to heat added?
- Sun Feb 02, 2020 10:03 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Reaction constant P
- Replies: 3
- Views: 98
Re: Reaction constant P
Gases can change volume depending on pressure but solids and liquids maintain a constant volume.
- Sun Feb 02, 2020 9:52 pm
- Forum: Phase Changes & Related Calculations
- Topic: Reversible and Irreversible
- Replies: 5
- Views: 201
Re: Reversible and Irreversible
Also, irreversible processes almost always do more work than reversible processes.
- Sun Feb 02, 2020 9:44 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Isolated system
- Replies: 10
- Views: 1290
Re: Isolated system
A system is considered isolated when the system cannot exchange energy/heat with its surroundings. An example would be a boiling water in a closed insulated container, like a hydroflask. This is considered an isolated system because the hot water in the container cannot exchange heat/energy with the...
- Sun Jan 26, 2020 10:45 pm
- Forum: Phase Changes & Related Calculations
- Topic: State functions
- Replies: 3
- Views: 90
State functions
So heat isn't a state function but internal energy of an isolated system is a state function. What qualifies something to be, or not to be, a state function?
- Sun Jan 26, 2020 10:32 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Exothermic and Endothermic
- Replies: 11
- Views: 738
Re: Exothermic and Endothermic
Exothermic is negative because it is releasing energy, while endothermic is positive because it is absorbing energy
- Sun Jan 26, 2020 10:23 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: 3 methods
- Replies: 5
- Views: 123
Re: 3 methods
You should use certain methods based on the information you are given, so different methods for different circumstances, but also I believe that the methods using bond enthalpies is the least accurate method because the bond enthalpies of non-diatomic molecules are averages from many different molec...
- Sun Jan 26, 2020 10:13 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Different Enthalpy Strategies
- Replies: 5
- Views: 165
Re: Different Enthalpy Strategies
If I remember correctly, using the strategy with the bond enthalpies is the least accurate method so there is a benefit to using the other two.
- Sun Jan 26, 2020 10:05 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: The 3 methods
- Replies: 4
- Views: 126
The 3 methods
I forgot to write it in my notes, but which of the three methods was supposed to be the least accurate?
- Sun Jan 19, 2020 10:23 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Textbook clarification: weak acids and bases
- Replies: 3
- Views: 116
Re: Textbook clarification: weak acids and bases
OH- are the conjugate base of water. However, if water reacts with an acid, wouldn't it act as a base thus it would have a conjugate acid of hydronium ions?
- Sun Jan 19, 2020 10:13 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: pKa
- Replies: 13
- Views: 455
Re: pKa
pKa = -log Ka; so according to that equation, the lower the pKa is, the higher the Ka will be meaning it is a stronger acid. The higher the pKa is, the lower the Ka will be meaning it will be a weaker acid.
- Tue Jan 14, 2020 11:12 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 5H.2
- Replies: 2
- Views: 106
5H.2
So for problem 5H.2, the book says that for the reaction, K = 2.5 * 10^10, however in the solutions manual they use K = 2.5 * 10^7 for the calculations. Can someone please explain? Am I missing something here?
- Sun Jan 12, 2020 11:24 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Homogenous Equilibrium
- Replies: 13
- Views: 360
Re: Homogenous Equilibrium
It is homogeneous when the products and reactants are in the same phase. Heterogeneous is when the all the products and reactants aren't in the same phase so you would have to omit pure liquids and solids in your equilibrium calculations.
- Sun Jan 12, 2020 11:12 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Calculating K
- Replies: 9
- Views: 206
Re: Calculating K
pure liquids and solids, which includes water, are disregarded for the equilibrium expression because they don't have an affect on reactant amount at equilibrium and they don't have a concentrations to be used to calculate k.
- Sun Jan 12, 2020 11:03 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: pressure and volume
- Replies: 4
- Views: 130
Re: pressure and volume
When you look at the ideal gas , pv=nrt, the numbers have to be constant, so if p is being doubled v has to be halved since they are being multiplied to balance out and keep the value of nrt constant.