## Search found 54 matches

Tue Mar 13, 2018 12:19 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 15.63
Replies: 3
Views: 268

### Re: 15.63

I had the same question, and I was also wondering if the solutions made a mistake when it wrote down that K was 3130 and it actually meant 310 K. Thank you!
Tue Mar 13, 2018 12:14 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Hw 15.67
Replies: 5
Views: 1049

### Re: Hw 15.67

In this equation you cancel out A, but if you didn't what is A and what do you plug into the equation for it?
Tue Mar 13, 2018 12:13 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 15.61
Replies: 3
Views: 309

### Re: 15.61

I think that when you look at K it is K = k/k', but when you are looking at ln then it is ln(k'/k)
Tue Mar 13, 2018 12:11 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Replies: 3
Views: 275

If the catalyst is the solid in the reaction and the reaction occurs in the surface of the solid, can it be assumed that the catalyst is the excess substance in the reaction? Or will this not always be the case?
Sat Mar 03, 2018 12:50 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Straight line
Replies: 7
Views: 682

### Re: Straight line

It is also important to note that the slopes of these graphs will be either -k or k
Sat Mar 03, 2018 12:48 pm
Forum: General Rate Laws
Topic: Finding reaction rate [ENDORSED]
Replies: 5
Views: 381

### Re: Finding reaction rate[ENDORSED]

There was a question in which the answer was in mmol. I guess this is ok as long as what you are solving for maintains the units you used.
Sat Mar 03, 2018 12:47 pm
Forum: General Rate Laws
Topic: Rate Law dependent on Reactants [ENDORSED]
Replies: 4
Views: 323

### Re: Rate Law dependent on Reactants[ENDORSED]

How would we take into account temperature and activation energy when calculating k? Also, I'm confused about all the meanings we have given K in this class. Is k here the rate or the equilibrium constant?
Sat Mar 03, 2018 12:44 pm
Forum: General Rate Laws
Topic: 15.3 C
Replies: 8
Views: 857

### Re: 15.3 C

All you have to do to change and correct your answer if find the rate PER mole
Sat Mar 03, 2018 12:42 pm
Forum: General Rate Laws
Topic: Deriving integrated rate laws
Replies: 4
Views: 273

### Re: Deriving integrated rate laws

Does the y=mx+b form refer to anything else than the graphs we looked at in class?
Sat Mar 03, 2018 12:41 pm
Forum: General Rate Laws
Topic: Unique Reaction Rates [ENDORSED]
Replies: 33
Views: 77896

### Re: Unique Reaction Rates[ENDORSED]

Does this mean that even if all the stoichiometric coefficients were different, because of the concentrations of each species then all rates would be the same? And does unique rate refer to the equality of all rates or of one species only?
Sat Mar 03, 2018 12:36 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Overall order
Replies: 4
Views: 395

### Re: Overall order

The order of each individual reactant or product serves to solve for the reactions used in class. But I don't see what the overall order would be used for.
Sat Mar 03, 2018 12:32 pm
Forum: *Free Energy of Activation vs Activation Energy
Topic: What is Free Energy of Activation
Replies: 5
Views: 1412

### Re: What is Free Energy of Activation

When you say it includes both entropy and enthalpy are you saying that because when one calculates Gibbs free energy you use both in the equation? Would both of the values used be referring to the activation energy?
Thu Feb 22, 2018 3:53 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Activation Energy
Replies: 4
Views: 620

### Re: Activation Energy

If the amount of energy that is needed to make a reaction happen is small, then no matter how much you raise temperature, the reaction will occur regardless because it only needs a small increase in order to occur.
Thu Feb 22, 2018 3:40 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Diamond and graphite
Replies: 8
Views: 1838

### Re: Diamond and graphite

Diamond turns into graphite spontaneously, but that does not mean it occurs fast. In fact, it happens very very slowly, for kinetics rather than thermodynamics is controlling this reaction. The diamond is kinetically stable with respect to graphite, yet thermodynamically unstable.
Thu Feb 22, 2018 3:30 pm
Forum: General Rate Laws
Topic: Convention of the Negative Sign [ENDORSED]
Replies: 1
Views: 195

### Convention of the Negative Sign[ENDORSED]

I understand why in class we were told that since the concentration of the reactants decreases, then a negative sign is placed in front of the equation so that the resulting answer is positive. However, why not keep it in order to have it be an indicator that the species is in fact a reactant? If th...
Wed Feb 14, 2018 10:19 pm
Forum: Balancing Redox Reactions
Topic: Salt Bridges
Replies: 14
Views: 522

### Re: Salt Bridges

How would the charges of each side be balanced using a porous disk? Also, a single line in the shorthand equation serves as a porous disk too instead of two lines signifying a salt bridge, and when the reactants and products of one half equation are in the same state you separate them by a comma.
Wed Feb 14, 2018 10:16 pm
Forum: Balancing Redox Reactions
Topic: 14.1 Question
Replies: 2
Views: 196

### Re: 14.1 Question

How I usually do it is that I use the simple reduction and oxidation reactions and once I have those down into one overall reaction, I balance the charges adding H protons, and balance the H and Os adding water.
Wed Feb 14, 2018 10:14 pm
Forum: Balancing Redox Reactions
Topic: Standard Reduction Potentials Concept
Replies: 4
Views: 424

### Re: Standard Reduction Potentials Concept

I understand that all values are for standard reduction potentials, but when using the Ecell=Ecathode-Eanode we plug in both values for the reduction potential of the equations from the anode and cathode even when we know the reaction at the anode is actually the reverse reaction since it is actuall...
Sat Feb 10, 2018 1:22 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Free expansion
Replies: 2
Views: 201

### Re: Free expansion

So no work is done but there still is a change in internal energy due to the change in volume?
Sat Feb 10, 2018 1:19 pm
Forum: Calculating Work of Expansion
Topic: Work Equations [ENDORSED]
Replies: 9
Views: 637

### Re: Work Equations[ENDORSED]

Will the problem always say that the reaction is isothermal? Or will it not always be the case and how does this change your way of approaching the problem?
Sat Feb 10, 2018 1:09 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Degeneracy (W) [ENDORSED]
Replies: 8
Views: 609

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

I have seen some problems in which W also sometimes is calculated using Avogadro's number. When would this be the case instead of doing 2^molecules in the system?
Sat Feb 10, 2018 1:07 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Reversible an Irreversible [ENDORSED]
Replies: 4
Views: 383

### Re: Reversible an Irreversible[ENDORSED]

Is it correct to think that in a reversible expansion, the deltaStotal would be zero, and that in an irreversible expansion the deltaSsurrounding would be zero?
Thu Feb 01, 2018 4:43 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Bomb calorimeter
Replies: 7
Views: 395

### Re: Bomb calorimeter

Also, an easy way to remember that it is bomb calorimeter is that since the volume does not change, pressure builds up inside against the constant volume!
Thu Feb 01, 2018 4:40 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Second Law of Thermodynamics [ENDORSED]
Replies: 5
Views: 478

### Re: Second Law of Thermodynamics[ENDORSED]

So according to the law, disorder increases until equilibrium is reached? So disorder does not always increase?
Thu Feb 01, 2018 4:37 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Lunchbox?
Replies: 3
Views: 289

### Re: Lunchbox?

Hi! I guess the lunchbox, if it is completely sealed and no matter was taken from its inside it could be isolated? As long as no matter and energy are lost then it would be.
Mon Jan 22, 2018 12:02 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Question 8.103
Replies: 1
Views: 135

### Question 8.103

Can someone explain why the solution manual states that the average kinetic energy expression is 3/2RT, when the constants sheet states nRT? Can we assume this is an ideal gas and that there is only one mol so it matches up with the J/mol?
Sun Jan 21, 2018 11:59 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Problem 8.99
Replies: 6
Views: 337

### Re: Problem 8.99

How does calculating limiting reactant impact this problem?
Sun Jan 21, 2018 11:59 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Problem 8.99
Replies: 6
Views: 337

### Re: Problem 8.99

In the previous explanation for this question, how is the ZnCl2 separated? Should we say they are separated into their ionized versions and calculate the enthalpies of each? Isn't the product ZnCl2 and we should use bond enthalpies of two ZnCl bonds? And how is the enthalpy of formation of 2Cl somet...
Wed Jan 17, 2018 11:04 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Self-Test 8.5B
Replies: 3
Views: 186

### Re: Self-Test 8.5B

Did you use an equation provided by the equations sheet? OR can we also think about this logically? I am finding it really hard to think about what to subtract or add from something else with the way things are worded.
Wed Jan 17, 2018 11:00 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Q 8.13
Replies: 9
Views: 531

### Re: Q 8.13

Does it matter if we are talking about work or heat? I understand that when heat is lost it is negative, but what about work? I am confused about these two terms
Wed Jan 17, 2018 10:56 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: U and H
Replies: 3
Views: 287

### U and H

Can someone please clarify the difference between deltaU and deltaH and how they relate to each other in the equation deltaU = deltaH-pdeltaV
Wed Jan 10, 2018 7:41 pm
Forum: Phase Changes & Related Calculations
Topic: Enthalpy is a state property
Replies: 13
Views: 737

### Re: Enthalpy is a state property

We can also think about state properties in the way Dr Lavelle showed us in class with the mountain image. In class, the path the hikers took to get from point A to B did not matter, which is what the rest was saying about the initial and final points.
Wed Jan 10, 2018 7:39 pm
Forum: Phase Changes & Related Calculations
Topic: Supercooling and Superheating
Replies: 2
Views: 218

### Re: Supercooling and Superheating

Do you think we will be asked to pdo problems in which the delta Hs refer to supercooling and superheating problems? Would they be solved the same way or do some specific rules apply?
Wed Jan 10, 2018 7:37 pm
Forum: Phase Changes & Related Calculations
Topic: Endo and Exothermic Ways to Remember
Replies: 28
Views: 5635

### Re: Endo and Exothermic Ways to Remember

Adding to what everyone else has said and like someone said, it is also important to see how these terms refer to a reaction. If the reaction is exothermic, you are releasing heat, meaning that on the products side of your reaction you could add heat. Meanwhile, if the reaction is endothermic, you a...
Tue Dec 05, 2017 10:49 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Problem 12.69
Replies: 6
Views: 1082

### Re: Problem 12.69

How do you go about solving the problem (a) is you only have Kb of NH3 and it is on the products side? Are you supposed to solve for Ka or should you keep Kb and work to the other side?
Tue Dec 05, 2017 4:42 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: 12.57
Replies: 3
Views: 316

### Re: 12.57

Can someone please explain how to do this problem? I've been trying to do it for over thirty minutes now.
Sun Nov 26, 2017 9:37 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 11.41
Replies: 2
Views: 222

### 11.41

Can someone please explain what method we are supposed to use to solve 41?
Sun Nov 26, 2017 9:00 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 11.31 and 11.33
Replies: 2
Views: 221

### 11.31 and 11.33

Hi! I was doing questions 31 and 33 from chapter 11 and run into some controversy. While the answer for 31 says that if Q is less than K then more products will be formed, the answer to 33 says that if Q is greater than K then more product will be formed too. Is this a problem with the answers?
Mon Nov 20, 2017 6:30 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Homework question 17.33
Replies: 4
Views: 277

### Homework question 17.33

Hi, can someone please explain how to solve for questions b and c of this question? Why is b) a mono or bidentate when there are so many free electron pairs, and why in is it a monodentate in part c) if there are also multiple free electron pairs that could form bonds?
Mon Nov 20, 2017 6:28 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Homework Q17.37
Replies: 2
Views: 195

### Re: Homework Q17.37

Hi, can someone please go through what bonds of the molecule one should look at to determine coordination compounds for these molecules? I was tried to do it by free electron pairs but I can't get the right answers.
Mon Nov 13, 2017 7:51 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 13.a)
Replies: 3
Views: 274

### Re: 13.a)

I read the previous answer to this question, but in the answers it places both electron lone pairs on the same side of the Iodine central atom, not on opposite sides. Is this because the answer booklet placed the electrons arbitrarily? Or because they actually do go on one side of the Iodine.
Mon Nov 13, 2017 7:48 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 13.a)
Replies: 3
Views: 274

### 13.a)

I don't understand why the Iodine chain would be linear if there are two lone pairs bonded to the central atom. Shouldn't it be bent/angular instead of linear?
Mon Nov 06, 2017 4:30 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm Materials [ENDORSED]
Replies: 7
Views: 486

### Re: Midterm Materials[ENDORSED]

Should we be able to know the conversion from eV to Joules for the midterm?
Mon Nov 06, 2017 4:26 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: H- atom equation for other elements
Replies: 1
Views: 160

### H- atom equation for other elements

I know that the En equation to determine the energy of an H-atom changing energy levels only works for Hydrogen because it only has one electron, but how would its energy amounts compare to another element, like for example, potassium? I know that since there are more electrons you would need to tak...
Mon Oct 30, 2017 5:01 pm
Forum: Quantum Numbers and The H-Atom
Topic: Direction of the Spin Magnetic Quantum Number
Replies: 5
Views: 442

### Re: Direction of the Spin Magnetic Quantum Number

So does this mean that the +/- signs are relative to each other? And also, when you draw a pair of electrons of a lone electron, do you by convention draw then up or does it not matter meaning you could draw them pointing down?
Mon Oct 30, 2017 4:59 pm
Forum: Quantum Numbers and The H-Atom
Topic: Values of Quantum Numbers
Replies: 3
Views: 762

### Re: Values of Quantum Numbers

When do you know if you should be using the n-1 equation for l of that s= n=0; p= l=1; etc.? I am really confused because I understand the material but then always get the values wrong when it comes to l because I don't know when to use the equation or the set l values that correspond to n levels.
Wed Oct 25, 2017 3:55 pm
Forum: *Particle in a Box
Topic: What is the equation: En= (n^2*h^2)/(8*m*L^2) used for? [ENDORSED]
Replies: 5
Views: 1502

### Re: What is the equation: En= (n^2*h^2)/(8*m*L^2) used for?[ENDORSED]

I am having trouble understanding the math questions that we could be asked in the test that could have to do with this concept. I understand the idea, but we have never seen it in class. Will we need to use it in the test?
Wed Oct 25, 2017 3:48 pm
Forum: *Shrodinger Equation
Topic: Using Shrodinger's Equation
Replies: 4
Views: 586

### Re: Using Shrodinger's Equation

I had the same exact question. I was unsure of how to apply the equation for math problems and did not understand how we were going to be asked this in the test. I am guessing the questions about it will be like the conceptual questions we had on the past two tests.
Mon Oct 16, 2017 9:44 pm
Forum: Properties of Electrons
Topic: De Broglie Equation
Replies: 3
Views: 318

### Re: De Broglie Equation

When do we use 1/2mv2 for Ek and when do we use de broglies equation for Ek?
Mon Oct 16, 2017 9:40 pm
Forum: Properties of Electrons
Topic: Threshold level and Work Function [ENDORSED]
Replies: 6
Views: 577

### Re: Threshold level and Work Function[ENDORSED]

When do we use 1/2mv2 for Ek and when do we use de broglies equation for Ek?
Tue Oct 10, 2017 12:27 pm
Forum: Einstein Equation
Topic: Stefan-Boltzmann Law
Replies: 2
Views: 252

### Stefan-Boltzmann Law

Can someone please explain the Stephan-Boltzmann law? I am having a hard time understanding how to use it and what it is supposed to tell us.
Tue Oct 10, 2017 12:25 pm
Forum: Einstein Equation
Topic: How does E = hv lead to Einsteins equation E=MC2?
Replies: 4
Views: 2086

### Re: How does E = hv lead to Einsteins equation E=MC2?

Can someone explain the theory behind these equations? I don't understand what the photon energy is used to represent or what chemistry theories are represented.
Wed Oct 04, 2017 4:59 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Scientific Notation [ENDORSED]
Replies: 3
Views: 376

### Re: Scientific Notation[ENDORSED]

If we are converting a number like 0.0380 to scientific notation, we do need to include the last zero in the sense that we'd have to write it as 3.80 x 10^2 right?
Wed Oct 04, 2017 4:57 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Atomic Mass: Intensive or Extensive Property [ENDORSED]
Replies: 3
Views: 1165

### Re: Atomic Mass: Intensive or Extensive Property[ENDORSED]

Can someone please clarify the definition or difference between an intensive and extensive property regarding chemistry? I do not understand what they are supposed to reflect.