Search found 51 matches

by Regina Chi 2K
Wed Mar 11, 2015 4:09 pm
Forum: *Cyclohexanes (Chair, Boat, Geometric Isomers)
Topic: Newman projection for cyclohexane!
Replies: 1
Views: 544

Newman projection for cyclohexane!

For problem 8C on the the 2013 practice final, I could tell that the Newman projection is showing a cyclohexane molecule, but I was wondering how you be able to tell that it was in the chair conformation.
by Regina Chi 2K
Wed Mar 11, 2015 4:06 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Finding the n value for a redox reaction!
Replies: 2
Views: 2365

Finding the n value for a redox reaction!

For problem 4 in the 2013 practice final exam, I was wondering how they determined the n value to be 4? I understand that we can get the n value by looking at the redox reaction, but looking at the equation, I would think that it is 2, and not 4. I was thinking that it might be coming from the half-...
by Regina Chi 2K
Wed Mar 11, 2015 3:56 pm
Forum: *Cycloalkenes
Topic: Determining cis or trans for a cycloalkene!
Replies: 1
Views: 411

Determining cis or trans for a cycloalkene!

This is a problem on the 2012 practice final exam! It is problem 5 and I wasn't sure how we were supposed to know that molecule B is a a cis molecule and not trans?
by Regina Chi 2K
Wed Mar 11, 2015 3:52 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Determining the cathode and anode!
Replies: 1
Views: 358

Determining the cathode and anode!

This is a problem on the final for 2012. It is problem 3. If we are given the information: 0.0080M CrCl3(aq) and 0.12M CuSO4(aq), how would we know which is the anode and which is the cathode? And I'm not sure why we would know to use the basic Cu and Cr half-reactions on the formula sheet? What wou...
by Regina Chi 2K
Wed Mar 11, 2015 3:45 pm
Forum: *Alkanes
Topic: Geometric isomers for C6H14!
Replies: 4
Views: 874

Geometric isomers for C6H14!

This is question 6 on the 2011 practice final exam. They asked for geometric isomers (2 with a 5 carbon main chain and 2 with a 4 carbon main chain) and I understand how they got their answers. For the molecular formulas, would it matter if we have the parts of the main chain not in parentheses? And...
by Regina Chi 2K
Wed Mar 11, 2015 3:40 pm
Forum: *Cyclohexanes (Chair, Boat, Geometric Isomers)
Topic: Substituent and positioning in chair conformation!
Replies: 1
Views: 477

Substituent and positioning in chair conformation!

I just have a general question. I was doing practice finals and noticed that sometimes I would draw the chair conformation with the "headrest" on the top left and the "footrest" on the bottom right. Sometimes I would situate the substituent on the "headrest" or "fo...
by Regina Chi 2K
Tue Feb 24, 2015 9:41 am
Forum: First Order Reactions
Topic: Question 14.103
Replies: 1
Views: 566

Re: Question 14.103

Hm... I don't really remember exactly why this is true and don't know if I am able to explain it clearly, but if you look in 14.3 Rate Laws and Reaction Order, you would see that the initial rate of consumption = k [x]initial... And they noted that if you plot the concentration against the initial r...
by Regina Chi 2K
Tue Feb 24, 2015 9:37 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Collision Theory and TS Theory
Replies: 1
Views: 536

Collision Theory and TS Theory

I know we were supposed to read 14.12 Collision Theory and 14.13 Transition State Theory; however, Professor Lavelle did not cover these concepts and ideas at all in his lecture and course reader. We also were not asked to do any homework problems associated with these theories. These concepts and t...
by Regina Chi 2K
Mon Feb 23, 2015 3:59 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Questions about 14.85
Replies: 4
Views: 958

Re: Questions about 14.85

I don't remember the question, but could Ar possibly be a catalyst?
by Regina Chi 2K
Mon Feb 23, 2015 3:57 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalyst vs Intermediate
Replies: 6
Views: 65345

Re: Catalyst vs Intermediate

Also, catalysts are used throughout the reaction. So according to my understanding, catalysts appear in the reaction as a reactant, but also appear during the elementary steps of the reaction.
by Regina Chi 2K
Mon Feb 16, 2015 12:19 pm
Forum: First Order Reactions
Topic: Solution manual error?
Replies: 1
Views: 529

Solution manual error?

I think there is a slight error on 14.29B... Instead of t=(ln([A]o/[A]t))/0.17 min-1 and t=(ln(0.015/0.005))/k for the last step, shouldn't it be t=(ln([A]t/[A]o))/k and t=(ln(0.005/.015)/0.17 min-1???
by Regina Chi 2K
Wed Feb 11, 2015 1:06 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Determining cathode and anode from two half-reactions...
Replies: 3
Views: 5130

Re: Determining cathode and anode from two half-reactions...

This may be a little late, but it is because we are finding the Ka of the problem and Ka requires the acid (HF) to be in the denominator of the reaction quotient. So it must be a reactant and not a product.
by Regina Chi 2K
Tue Feb 10, 2015 9:21 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: The value of heat capacities!
Replies: 1
Views: 392

The value of heat capacities!

Just a general question, could the value of heat capacities every be negative? For example, if we were to find the value of the specific heat capacity, and were given q = -1000 joules, mass = 100 grams, and change in temperature is +100 degrees celsius. The resulting specific heat capacity would be ...
by Regina Chi 2K
Mon Feb 09, 2015 11:14 pm
Forum: Calculating Work of Expansion
Topic: Finding total work from several processes...
Replies: 1
Views: 363

Finding total work from several processes...

This is a question referring to problem 4A on the 2013 midterm practice exam. I understand the several steps to calculate the work from A to B, B to C, and C back to A. However, for the last part of question 4A, they calculated the total work for the entire process and added up all the individual st...
by Regina Chi 2K
Mon Feb 09, 2015 6:44 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Determining cathode and anode from two half-reactions...
Replies: 3
Views: 5130

Determining cathode and anode from two half-reactions...

I have posted this problem before, but it was specific to a certain problem. However, if the cell is not defined to be galvanic, and we are given two half-reactions and their respective E values, how will we know which one we should set as the anode and which on as the cathode?
by Regina Chi 2K
Mon Feb 09, 2015 6:40 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Platinum in cell diagrams
Replies: 4
Views: 994

Re: Platinum in cell diagrams

You must have a solid present. If both species are either gases, liquids, or aqueous solutions, you must add an electrode.
by Regina Chi 2K
Sun Feb 08, 2015 8:34 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Course Reader page46 example of "Gold and Nitric Acid"
Replies: 1
Views: 310

Re: Course Reader page46 example of "Gold and Nitric Acid"

I don't think you have to stress over this because we will usually be given the equations such that we are either given the half-reactions or the overall equation (you will have the find the half-reactions from the overall equation). I think in the course reader, Professor Lavelle just happened to h...
by Regina Chi 2K
Sun Feb 08, 2015 8:29 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Determining cathode and anode from two half-reactions!
Replies: 3
Views: 746

Re: Determining cathode and anode from two half-reactions!

Okay thanks, but why is it that for finding Ka, we have to make HF our reactant? I still don't think I really get that.
by Regina Chi 2K
Sun Feb 08, 2015 8:26 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Writing cell-diagrams with other products such as H+...
Replies: 4
Views: 1459

Re: Writing cell-diagrams with other products such as H+...

Thanks! I'll keep that in mind, but where exactly do we know how to position it? Will it be in the front or back of our main species?
by Regina Chi 2K
Sat Feb 07, 2015 1:09 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Determining cathode and anode from two half-reactions!
Replies: 3
Views: 746

Determining cathode and anode from two half-reactions!

This is problem 8 from the 2014 practice midterm exam. But it can also be a very general question (does not have to apply to this specific problem). From two given half-reactions, how do we determine which is the anode and which is the cathode. I usually try to assign anodes and cathodes to get the ...
by Regina Chi 2K
Sat Feb 07, 2015 1:04 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Order of species in cell diagram?
Replies: 3
Views: 642

Re: Order of species in cell diagram?

Usually you have:

anode ll cathode...

In the cell diagram, you would usually have:

electrode (if needed) l reactant l product ll reactant l product l electrode (if needed)...
by Regina Chi 2K
Sat Feb 07, 2015 1:03 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 13.15 cell diagram
Replies: 3
Views: 636

Re: 13.15 cell diagram

Is the Ni (s) electrode present because both species are either aqueous or gas? They just picked Ni (s) for convenience since part of the reaction deals with nickel ions. And for the KOH, I went to office hours and the TA said that it would have been okay to just include OH- and that the K does not ...
by Regina Chi 2K
Sat Feb 07, 2015 12:59 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Writing cell-diagrams with other products such as H+...
Replies: 4
Views: 1459

Writing cell-diagrams with other products such as H+...

There were many homework problems that illustrate my question; however, I came across an example in the 2014 practice midterm exam. This is problem 7C. When writing the cell diagram, how would we know when to include the H+ (aq) and H20 (l)? Do we always include the H+ if it is present in our equati...
by Regina Chi 2K
Sat Feb 07, 2015 12:51 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Finding Cv or Cp for entropy change due to volume change!
Replies: 1
Views: 519

Finding Cv or Cp for entropy change due to volume change!

This is a questions from the 2012 midterm practice exam and it is problem 3B. I understand that in order to find the change in entropy, we have to use that equation, but I though that we could only use (3/2)R or (5/2)R if the species that we are dealing with is an ideal gas? This question does not i...
by Regina Chi 2K
Fri Feb 06, 2015 5:30 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Balancing chemical reactions to find Gibbs or enthalpy!
Replies: 2
Views: 482

Balancing chemical reactions to find Gibbs or enthalpy!

This is a general problem that I have come across many times. When you balance an chemical reaction in order to find the standard values (such as standard Gibbs, enthalpy, and entropy), is there a certain rule we have to abide to to balance the chemical reaction? For example, in problem 5A of the 20...
by Regina Chi 2K
Fri Feb 06, 2015 5:24 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Determining greater change in entropy!
Replies: 2
Views: 610

Determining greater change in entropy!

This is actually a question on the 2010 midterm practice exam. It is part B of the problem 4B. I also realize that this is a homework problem from chapter eight. It asks us which (house exterior or interior) has a greater change in entropy. However, they also mentioned that the temperature stays the...
by Regina Chi 2K
Tue Feb 03, 2015 1:06 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: n when calculating Gibbs Free Energy
Replies: 6
Views: 6129

Re: n when calculating Gibbs Free Energy

If I remember correctly, we are not using the mols of an atom but only the stoichiometric coefficient that accompanies the electrons that get cancelled out in the balanced equation. Hope this helps.
by Regina Chi 2K
Mon Feb 02, 2015 4:16 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Writing cell diagrams and half-reactions!
Replies: 1
Views: 356

Writing cell diagrams and half-reactions!

First of all, I have a general question regarding several problems in the textbook. When do we determine when to look up the values of half reactions in the back of the book? And also, are we not supposed to come up with the half-reactions ourselves because in some certain questions (13.11BDE), ther...
by Regina Chi 2K
Sun Feb 01, 2015 5:17 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Clarification on standard potentials with SHE!
Replies: 1
Views: 283

Clarification on standard potentials with SHE!

In section 13.6 of the chemistry textbook, at the bottom of page 530, Pt(s) l H2(g) l H+(aq) ll Cu2+(aq) l Cu(s) describes the copper electrode as the cathode and the hydrogen components the anode. I think I understand why that is so. However, further on (middle of) page 531 of the same section, the...
by Regina Chi 2K
Sat Jan 31, 2015 11:48 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Self Test 8.3B: Why do we not Include n in our Calculation?
Replies: 1
Views: 592

Re: Self Test 8.3B: Why do we not Include n in our Calculati

I think it is assuming that we have one mol of carbon dioxide gas (ideal gas). So in the answers in the back, this was an assumption and was not included in the calculations. Hope this helps.
by Regina Chi 2K
Thu Jan 29, 2015 6:25 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Units for calculating standard reaction enthalpies...
Replies: 2
Views: 507

Units for calculating standard reaction enthalpies...

I was a bit confused on what units to use when (such as kJ versus kJ/mol). I know that for calculating regular reactions that deal with entropy and internal energy, we would just have J/K and J respectively. However, I need clarification on what units to use when calculating the following: 1. Hess's...
by Regina Chi 2K
Thu Jan 29, 2015 11:16 am
Forum: Phase Changes & Related Calculations
Topic: Calculating heat capacity from q=mCsΔT!
Replies: 2
Views: 764

Calculating heat capacity from q=mCsΔT!

So I have 25.0 grams of a metal at 90°C and that is added to 50.0 grams of water at 25°C. The temperature of the water rises to 29.8°C. And they want us to find the specific heat capacity of the metal. I do understand we use q(metal)=-q(water), but can we assume that the final temperature of the met...
by Regina Chi 2K
Wed Jan 28, 2015 6:09 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard enthalpies of formation of a reaction!
Replies: 1
Views: 365

Standard enthalpies of formation of a reaction!

This is actually specific to a problem in the textbook (7.53). It asks us to find the final temperature for a reaction. However, the part that I do get is how they came up with their value of the standard enthalpy of formation. A few values were not given in the back of the book and I do not underst...
by Regina Chi 2K
Wed Jan 28, 2015 5:49 pm
Forum: Phase Changes & Related Calculations
Topic: Phase change with q=mCsΔT!
Replies: 3
Views: 782

Re: Phase change with q=mCsΔT!

Oh okay. So you're saying when we calculated q=mCsΔT, at that point, the ice cube is already melted into liquid water. And so we would use the specific heat capacity of water to calculate the temperature difference between the two components? This is what you mean right? :)
by Regina Chi 2K
Wed Jan 28, 2015 5:08 pm
Forum: Phase Changes & Related Calculations
Topic: Phase change with q=mCsΔT!
Replies: 3
Views: 782

Phase change with q=mCsΔT!

Hi, this is actually regarding a specific problem in the textbook (7.39). We are trying to find the final temperature when you put an ice cube at 0°C into water at 45°C. The mass for the ice cube is 50.0 grams and for the water it is 400.0 grams. I understand we use the equation q=mCsΔT, but the par...
by Regina Chi 2K
Wed Jan 21, 2015 5:22 pm
Forum: Calculating Work of Expansion
Topic: Quiz 1 preparation, winter 2013 #3
Replies: 5
Views: 834

Re: Quiz 1 preparation, winter 2013 #3

I'm not really sure if my guess is correct, but there is a definite change in volume. And if you see the respective volumes for both pathways, the pressure is constant when there is a volume change. And therefore, you would use 5.0 atm for pathway one and 2.0 atm for pathway two.
by Regina Chi 2K
Wed Jan 21, 2015 10:42 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Units on Question 5.57
Replies: 2
Views: 512

Re: Units on Question 5.57

Personally, I think it should probably be kJ/mol because we are talking about the amount of internal energy or enthalpy of a certain compound or whatnot. And we measure it by kJ/mol. However, I'm not sure what problem you are referring to. It might be better if you can specify.
by Regina Chi 2K
Tue Jan 13, 2015 1:13 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hess's Law Addition?
Replies: 3
Views: 549

Re: Hess's Law Addition?

Regardless of getting "credit" or not, I was wondering how we would know what to include in each of the steps? For example, how would we know which elements to use, what compounds are formed, and how many steps it will take?
by Regina Chi 2K
Sat Jan 10, 2015 10:28 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Thinking Point page 240
Replies: 2
Views: 612

Re: Thinking Point page 240

Hey! I'm not sure about this but I think that in most electric circuits, whenever we want to reverse the direction of the flowing energy, we must reverse the direction of the electric current. For example, to "recharge" a battery, we force the charge to reverse its direction of flow. Hope ...
by Regina Chi 2K
Wed Dec 10, 2014 10:22 pm
Forum: Identifying Acidic & Basic Salts
Topic: Acidic,basic, and neutral aqueous solutions
Replies: 2
Views: 832

Re: Acidic,basic, and neutral aqueous solutions

Cl- doesn't really do anything because it won't pick up a proton. If you look at the chart in that section, all the small and highly, positively charged cations make it acidic. And also if you look at that chart, Cl- is a neutral anion.
by Regina Chi 2K
Tue Dec 09, 2014 12:42 am
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: strength of an acid
Replies: 1
Views: 426

Re: strength of an acid

For binary acids (HA), we must take into account both bond length and the electronegativity of A. Yes, it is true that the longer (more distance) between the bonds of H and A, the easier it is for H to detach from A because there is less attraction (used to compare and contrast A in same vertical gr...
by Regina Chi 2K
Tue Dec 02, 2014 12:10 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Homework Problem 16.31 Part B
Replies: 1
Views: 277

Re: Homework Problem 16.31 Part B

If you look at the Lewis structure of carbonate, you will notice that it demonstrates a resonance structure where one oxygen is double-bonded and the other two are single-bonded to the carbon. Each of these single-bonded oxygens can attach to a metal, making it either monodentate or possibly bidenta...
by Regina Chi 2K
Thu Nov 27, 2014 4:21 pm
Forum: Lewis Structures
Topic: Lowest Ionization Energy on Central Atom NNO
Replies: 1
Views: 422

Re: Lowest Ionization Energy on Central Atom NNO

Regarding your question, sometimes I don't think you need to look at Lewis structures so technically. Nitrogen is in the middle of the molecule because it can form more bonds and also you might need to take a look at the formal charges to determine this. However, this is one of the few exceptions to...
by Regina Chi 2K
Fri Nov 21, 2014 8:16 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Monodentate or bidentate
Replies: 1
Views: 1832

Re: Monodentate or bidentate

CH3NH2 will be a monodenate ligand. You can tell by drawing or picturing the Lewis structure. I'll help you out. CH3NH2 will have a total of 14 electrons to use for the Lewis structure. You would bond 3 hydrogens and 1 nitrogen to the carbon. Then you would bond the two remaining hydrogens to the ni...
by Regina Chi 2K
Mon Nov 10, 2014 10:08 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Central Atom FC
Replies: 1
Views: 390

Central Atom FC

In general, how do we determine which atom gets the FC of 0??? I know that we want all if not most atoms to have a FC of 0, but in the case for anions it is different. For example, if we have a central atom and a bonding atom and one of them can be 1- and the other can be 0 (in regards to FC), which...
by Regina Chi 2K
Sun Nov 09, 2014 1:41 pm
Forum: Significant Figures
Topic: Significant Figures (Fall 2011 Midterm)
Replies: 1
Views: 389

Significant Figures (Fall 2011 Midterm)

For questions such as #4 on the Fall 2011 Midterm: "Heating Copper (I) Chloride to about 1200 C results in blue fireworks. The hot compound emits blue light with energy of 4.40 x 10^-19 J per photon. What is the wavelength of the blue light in nanometers?" In this situation, we did not use...
by Regina Chi 2K
Tue Nov 04, 2014 1:12 pm
Forum: Hybridization
Topic: How Hybridization Occurs
Replies: 2
Views: 549

Re: How Hybridization Occurs

Well, I'm not sure if I can completely answer your question, but hybridization occurs by moving an electron up to a higher energy level because it only takes a very small amount of energy to do so since the energy of the two orbitals (usually the s-orbital and the p-oribital) does not differ by much...
by Regina Chi 2K
Mon Oct 27, 2014 5:34 pm
Forum: Lewis Structures
Topic: Lewis Structures (Oxygen)
Replies: 2
Views: 479

Lewis Structures (Oxygen)

Hi! I have a question regarding the Lewis structure of molecules that have oxygen. Why is it that in some situations, oxygen double bonds and in some others, it has only a single bond? I know that oxygen tends to have double bonds to complete the octet, but for example, why is oxygen single bonded t...
by Regina Chi 2K
Tue Oct 21, 2014 5:44 pm
Forum: Significant Figures
Topic: Rounding to 1 sig fig when there is a 5
Replies: 4
Views: 816

Re: Rounding to 1 sig fig when there is a 5

Hi Soraya! I understand what you mean. The appendix in the back of the textbook says to round to the nearest even number. Despite having 4.45 that would supposedly round to 4.5 (given the fact that the problem only wants two significant figures), the the book says that it should be rounded to 4.4 ac...
by Regina Chi 2K
Thu Oct 16, 2014 11:33 pm
Forum: Properties of Light
Topic: Spectropic Series
Replies: 3
Views: 453

Re: Spectropic Series

Hello! Most of the problems are very "math-based," but I think it definitely doesn't hurt to know a general idea of the Balmer and Lyman Series! Just take a little time to memorize the most popular spectrums such as infrared, visible light, UV, and maybe x-ray and their general range of wa...
by Regina Chi 2K
Wed Oct 08, 2014 6:14 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Avogadro's Number
Replies: 2
Views: 832

Avogadro's Number

I have a really general question! What exactly is Avogadro's number? It seems like it could be used for converting almost anything to mols. For example, sometimes the conversion factor could be atoms, molecules, photons, and even humans... I'm also not quite sure when to use Avogadro's number or whe...

Go to advanced search