Search found 26 matches

by E_Villavicencio 2N
Sun Mar 19, 2017 10:04 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Midterm 2016 Q3C
Replies: 1
Views: 308

Re: Midterm 2016 Q3C

I did not fully understand the reason why, but Dr. Lavelle said it was fine if we just included the ions in each part of the reaction.
by E_Villavicencio 2N
Fri Mar 17, 2017 9:03 pm
Forum: *Constitutional and Geometric Isomers (cis, Z and trans, E)
Topic: Substituents, naming Z or E
Replies: 1
Views: 505

Substituents, naming Z or E

If you have a substituent and a methyl in one side of the double bond (to the right for example) but on the other side (left) you just have two methyl molecules, you don't have to name it Z or E, right?
by E_Villavicencio 2N
Fri Mar 17, 2017 9:00 pm
Forum: *Alkanes
Topic: ORDER OF SUBSTITUENTS
Replies: 2
Views: 614

Re: ORDER OF SUBSTITUENTS

Are you sure? in my discussion we put the methylethyl first, so I'm confused
by E_Villavicencio 2N
Fri Mar 17, 2017 10:45 am
Forum: *Alkanes
Topic: ORDER OF SUBSTITUENTS
Replies: 2
Views: 614

ORDER OF SUBSTITUENTS

If one substituent is methylethyl and other is methyl, which one is named first?
by E_Villavicencio 2N
Mon Mar 06, 2017 8:25 pm
Forum: Administrative Questions and Class Announcements
Topic: Quiz 2 Winter 2017
Replies: 160
Views: 15319

Re: Quiz 2 Winter 2017

Will the answers of quiz 2 (the actal quiz) be posted?
by E_Villavicencio 2N
Sun Feb 19, 2017 4:30 pm
Forum: Balancing Redox Reactions
Topic: Oxidation number of oxygen in O3
Replies: 3
Views: 3870

Oxidation number of oxygen in O3

What is the oxidation number of oxygen when in Ozone O3? If we have it in a reaction, and we have to balance the reaction, how many electrons are transferred between O3--->O2?
by E_Villavicencio 2N
Sun Feb 12, 2017 10:03 am
Forum: Balancing Redox Reactions
Topic: Adding H20 AND H+
Replies: 3
Views: 343

Adding H20 AND H+

When balancing some reactions, sometimes water or hydrogen is added to one of the half reactions. Can somebody explain when you add each of those?
by E_Villavicencio 2N
Sat Feb 04, 2017 2:56 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Units in answer
Replies: 2
Views: 325

Re: Units in answer

In page 340 of the book, they cancel out the units of entropy when they are adding the quantities because it goes #of moles x Sm(of each substance), and they get a result in J/K
by E_Villavicencio 2N
Sat Feb 04, 2017 1:59 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Units in answer
Replies: 2
Views: 325

Units in answer

If we have a reaction such as 2H2O2(l)--->2H2O(l)+O2(g), is the enthalpy of the reaction expressed in kJ/mol, or just kJ? Because the solutions manual adds all the values and expresses them in kJ/mol. Doesn't the mol part cancel out? Along with this question, if we are given the enthalpy and entropy...
by E_Villavicencio 2N
Tue Jan 31, 2017 4:40 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Chapter 9 Problem 43
Replies: 1
Views: 252

Chapter 9 Problem 43

In the solution of this problem, we have to consider two samples of water that were mixed and obtain the change in entropy. However, when we have to use the formula delta S=nCln(T2/T1) the solution manual uses 75.3 J/K as the heat capacity of water. Can someone explain to me where that value came fr...
by E_Villavicencio 2N
Sun Jan 22, 2017 8:31 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Homework: Chapter 8, #67
Replies: 2
Views: 335

Re: Homework: Chapter 8, #67

Yes, this happens with all the compounds. The enthalpy of reverse processes only differs in the sign. In this case, the process of vaporization (from liquid to gas) requires heat, that's why the sign is positive, whereas condensation, which is the reverse process (from gas to liquid), releases heat,...
by E_Villavicencio 2N
Sat Jan 21, 2017 9:37 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Chapter 8 Problem 31
Replies: 1
Views: 320

Re: Chapter 8 Problem 31

These values come from the equipartition theorem , which is used to estimate the translational (energy due to motion through space) and rotational (energy due to the rotational motion of a molecule) contributions to the internal energy of an ideal gas. The book doesn't derive the main equation of th...
by E_Villavicencio 2N
Thu Jan 12, 2017 10:35 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Sign Conventions
Replies: 1
Views: 232

Re: Sign Conventions

Hi Katrina! When the system does work the sign will be negative, because it is losing internal energy when it does that work. When work is being done on the system, the sign will be positive because the system is gaining energy. For example, if a system expands, it will be doing work because it is p...
by E_Villavicencio 2N
Wed Nov 30, 2016 1:38 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Problem 11.43
Replies: 2
Views: 405

Problem 11.43

This problem says: Consider the reaction 2NO2(g)<--->N2(g)+O(g). If the initial pressure of NO is 1.0 bar, and x is the equilibrium concentration of N2, what is the correct equilibrium relation? The answer is K=x^2/(1.0-2x)^2 My question was: the problem gives the pressure of one and the concentrati...
by E_Villavicencio 2N
Mon Nov 28, 2016 4:17 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Which flask represents the reaction in equilibrium?
Replies: 2
Views: 301

Which flask represents the reaction in equilibrium?

In question number 7 of Chapter 11, we are given the pictures of 4 flasks of a reaction of dissociation, and we are asked to select the flask that represents equilibrium. I see the same number of molecules and atoms in both flask 3 and flask 4. The answer says Flask 3. Why is flask 3 the one at equi...
by E_Villavicencio 2N
Sun Nov 20, 2016 3:24 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Why is water always a monodentate?
Replies: 2
Views: 415

Why is water always a monodentate?

A ligand can use its lone pairs to bond in a coordination compound. Water has two lone pairs, why can't it be a bidentate? Can somebody explain that to me please?
by E_Villavicencio 2N
Mon Nov 14, 2016 2:37 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: MO Diagram for Heteronuclear Diatomic Molecules [ENDORSED]
Replies: 2
Views: 435

MO Diagram for Heteronuclear Diatomic Molecules [ENDORSED]

When we have to do a MO Diagram of a compound such as HF, where the 1s orbital from H and the 2s from F combine, how do we label the resulting molecular orbital? Do we put sigma 2s? Because the book does not label them like that, it labels them 1 sigma, 2 sigma*, 3 sigma,etc., but I don't remember w...
by E_Villavicencio 2N
Thu Nov 10, 2016 8:44 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Chemical Equilibrium constant
Replies: 1
Views: 207

Re: Chemical Equilibrium constant

Yes, the equilibrium constant Kc is the same for a reaction in an specific temperature, independently of the concentrations. If the temperature changes, K is going to change. Usually if you are not given a temperature, you assume that the reaction is taking place at 25 degrees Celsius.
by E_Villavicencio 2N
Thu Nov 03, 2016 9:39 am
Forum: Properties of Light
Topic: What to do when a Energy is given in kJ*mol-1?
Replies: 6
Views: 781

What to do when a Energy is given in kJ*mol-1?

When a problem gives you an energy needed to break a C-C bond in kJ*mol, and asks you for the wavelength required in order to break that bond, do you need to convert that energy in J (by multiplying by 10^3) and then divide it by the Avogadro's number? I am not sure about the moles part (whether you...
by E_Villavicencio 2N
Sat Oct 22, 2016 11:22 pm
Forum: Trends in The Periodic Table
Topic: QUESTION ABOUT IONIC AND ATOMIC RADII
Replies: 2
Views: 361

QUESTION ABOUT IONIC AND ATOMIC RADII

Question number 93 in the book says: Below is pictured the reaction between an atom of sodium and an atom of chlorine. Identify each element and the ions formed and explain your reasoning. The picture shows the atoms A (SMALLER) and B(LARGER), and then the ions C (LARGER) and D(SMALLER) Taking into ...
by E_Villavicencio 2N
Sun Oct 16, 2016 8:49 pm
Forum: Lewis Structures
Topic: Chapter 3 #57 [ENDORSED]
Replies: 2
Views: 280

Re: Chapter 3 #57 [ENDORSED]

The least electronegative atom goes in the center. Check how the trends in the periodic table go regarding to electronegativity, and then you put the least electronegative in the center of the Lewis Structure. The exception is Hydrogen, that one never goes in the center. Hope it helps!
by E_Villavicencio 2N
Sun Oct 09, 2016 2:04 pm
Forum: DeBroglie Equation
Topic: Question: How should I decide if I use DeBroglie Equation or the equation for Kinetic Energy?
Replies: 4
Views: 419

Re: Question: How should I decide if I use DeBroglie Equation or the equation for Kinetic Energy?

I know, but what I did was to use the KE equation and then calculate the wavelenght using E=h(c/lamda)... Is that wrong?
by E_Villavicencio 2N
Sun Oct 09, 2016 8:51 am
Forum: DeBroglie Equation
Topic: Question: How should I decide if I use DeBroglie Equation or the equation for Kinetic Energy?
Replies: 4
Views: 419

Question: How should I decide if I use DeBroglie Equation or the equation for Kinetic Energy?

Question #33 in the book says: The velocity of an electron that is emitted from a metallic surface by a photon is 3.6x10^3 km/s. What is the wavelenght of the ejected electron? When I started solving the problem, the first equation that came to my mind was the kinetic energy one (as the electron was...
by E_Villavicencio 2N
Sun Oct 02, 2016 8:23 am
Forum: Phase Changes & Related Calculations
Topic: Chemistry Humor
Replies: 26
Views: 2585

Chemistry Jokes :)

What did one charged atom say to the other? I've got my ion you! Why was the mole of oxygen molecules excited when he walked out of the singles bar? Because he got Avogadro's number! What does the diamond say to the diamond? “Sorry, I’ve been under a lot of pressure lately” The other they I went to ...

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