Search found 26 matches
- Sun Mar 19, 2017 10:04 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Midterm 2016 Q3C
- Replies: 1
- Views: 590
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.
- 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: 1314
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?
- Fri Mar 17, 2017 9:00 pm
- Forum: *Alkanes
- Topic: ORDER OF SUBSTITUENTS
- Replies: 2
- Views: 1431
Re: ORDER OF SUBSTITUENTS
Are you sure? in my discussion we put the methylethyl first, so I'm confused
- Fri Mar 17, 2017 10:45 am
- Forum: *Alkanes
- Topic: ORDER OF SUBSTITUENTS
- Replies: 2
- Views: 1431
ORDER OF SUBSTITUENTS
If one substituent is methylethyl and other is methyl, which one is named first?
- Mon Mar 06, 2017 8:25 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Quiz 2 Winter 2017
- Replies: 160
- Views: 24138
Re: Quiz 2 Winter 2017
Will the answers of quiz 2 (the actal quiz) be posted?
- Sun Feb 26, 2017 2:47 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 2977909
- Sun Feb 19, 2017 4:30 pm
- Forum: Balancing Redox Reactions
- Topic: Oxidation number of oxygen in O3
- Replies: 3
- Views: 13337
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?
- Sun Feb 12, 2017 10:03 am
- Forum: Balancing Redox Reactions
- Topic: Adding H20 AND H+
- Replies: 3
- Views: 3188
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?
- Sat Feb 04, 2017 2:56 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Units in answer
- Replies: 2
- Views: 681
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
- Sat Feb 04, 2017 1:59 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Units in answer
- Replies: 2
- Views: 681
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...
- 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: 430
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...
- 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: 564
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,...
- Sat Jan 21, 2017 9:37 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Chapter 8 Problem 31
- Replies: 1
- Views: 543
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...
- Thu Jan 12, 2017 10:35 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Sign Conventions
- Replies: 1
- Views: 473
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...
- Wed Nov 30, 2016 1:38 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Problem 11.43
- Replies: 2
- Views: 661
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...
- Mon Nov 28, 2016 4:17 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Which flask represents the reaction in equilibrium?
- Replies: 2
- Views: 635
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...
- Sun Nov 20, 2016 3:24 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Why is water always a monodentate?
- Replies: 2
- Views: 873
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?
- 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: 925
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...
- Thu Nov 10, 2016 8:44 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Chemical Equilibrium constant
- Replies: 1
- Views: 456
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.
- 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: 1265
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...
- Sat Oct 22, 2016 11:22 pm
- Forum: Trends in The Periodic Table
- Topic: QUESTION ABOUT IONIC AND ATOMIC RADII
- Replies: 2
- Views: 714
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 ...
- Sun Oct 16, 2016 8:49 pm
- Forum: Lewis Structures
- Topic: Chapter 3 #57 [ENDORSED]
- Replies: 2
- Views: 547
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!
- Sun Oct 09, 2016 10:16 pm
- Forum: DeBroglie Equation
- Topic: Question: How should I decide if I use DeBroglie Equation or the equation for Kinetic Energy?
- Replies: 4
- Views: 781
Re: Question: How should I decide if I use DeBroglie Equation or the equation for Kinetic Energy?
Ohhhhh, now everything is clear! Thank you very much!!!! :)
- 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: 781
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?
- 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: 781
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...
- Sun Oct 02, 2016 8:23 am
- Forum: Phase Changes & Related Calculations
- Topic: Chemistry Humor
- Replies: 26
- Views: 5425
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 ...