Search found 39 matches
- Fri Mar 16, 2018 7:29 am
- Forum: *Alkanes
- Topic: Organic Molecules in general
- Replies: 1
- Views: 1121
Organic Molecules in general
Just to make sure, all organic molecules have carbons that always have four bonds, correct? No lone pairs on carbon allowed? I know this was emphasized in class, but I just want to make sure it applies to all organic molecules.
- Fri Mar 16, 2018 7:25 am
- Forum: *Amines
- Topic: Heterocyclic amines
- Replies: 1
- Views: 1127
Heterocyclic amines
I was watching a nutrition/health video the other day that mentioned the carcinogenic effects of heterocyclic amines, and I want to know more. How are heterocyclic amines produced and why are they carcinogenic?
- Fri Mar 16, 2018 7:19 am
- Forum: *Aldehydes
- Topic: Toxicity
- Replies: 1
- Views: 1114
Toxicity
Are aldehydes toxic to humans? Or rather, does it depend on the type and/or quantity of aldehyde?
- Sat Mar 10, 2018 9:05 am
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Steady-state vs. Pre-equilibrium [ENDORSED]
- Replies: 2
- Views: 488
Steady-state vs. Pre-equilibrium [ENDORSED]
In lecture, Dr. Lavelle said that the pre-equilibrium approach is simpler than the steady-state approach, but it is also less flexible. What did he mean by "less flexible"?
- Sat Mar 10, 2018 8:56 am
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Microscopic Reversibility [ENDORSED]
- Replies: 1
- Views: 282
Microscopic Reversibility [ENDORSED]
When going over reaction profiles, Dr. Lavelle said that "microscopic reversibility" was being assumed, meaning that we assume that the reaction has the same intermediates in the forward and reverse directions. This effectively means that the forward and reverse reactions follow the same p...
- Sat Mar 10, 2018 8:39 am
- Forum: Experimental Details
- Topic: Experimental Techniques
- Replies: 3
- Views: 1010
Experimental Techniques
What are some experimental techniques to measure the rate of the reaction? How would one monitor the concentration at precise instances after the reaction has initiated?
- Wed Feb 28, 2018 7:40 am
- Forum: First Order Reactions
- Topic: Half-life of first order reactions [ENDORSED]
- Replies: 4
- Views: 646
Half-life of first order reactions [ENDORSED]
I understand from the half-life equation that the half-life of a first order reaction does not depend on concentration and that, therefore, it has the same value at all stages of the reaction. However, this does not make sense to me. How can the half-life be the same at all stages of the reaction, e...
- Wed Feb 28, 2018 7:33 am
- Forum: Second Order Reactions
- Topic: Rate of Second-order reactions [ENDORSED]
- Replies: 1
- Views: 255
Rate of Second-order reactions [ENDORSED]
In the textbook, when discussing the rate of second-order reactions, it says that "the larger the rate constant, the greater the dependence of the rate on the concentration of the reactant." Can someone please explain this to me? I have been trying to find this relationship when looking at...
- Wed Feb 28, 2018 7:28 am
- Forum: Second Order Reactions
- Topic: Half-life of Second-Order
- Replies: 2
- Views: 1684
Half-life of Second-Order
In the textbook, at the end of section 15.6, it gives a table detailing all the components of each order of a reaction. For the half-life of a second-order reaction, it writes that the equation is t 1/2 = \frac{1}{k[A]} . However, underneath that, it says "(not used)." Does anyone know wha...
- Wed Feb 28, 2018 7:24 am
- Forum: Zero Order Reactions
- Topic: Half-life of Zero Order [ENDORSED]
- Replies: 4
- Views: 629
Half-life of Zero Order [ENDORSED]
In the textbook, at the end of section 15.6, it gives a table detailing all components of each order of a reaction. When writing the half-life of a zero-order reaction, it stated that it was t 1/2 = \frac{[A]}{2k} , but underneath that it says "(not used)." Does anyone know what this means...
- Wed Feb 28, 2018 7:18 am
- Forum: General Rate Laws
- Topic: 15.3(c)
- Replies: 2
- Views: 394
Re: 15.3(c)
Sorry I would like to make a correction. The unique rate of the reaction refers to any one of the parts of this equation: -\frac{1}{a}\frac{\Delta [A]}{\Delta t}=-\frac{1}{b}\frac{\Delta [B]}{\Delta t}=\frac{1}{c}\frac{\Delta [C]}{\Delta t}=\frac{1}{d}\frac{\Delta [D]}{\Delta t} ; all are equal. How...
- Thu Feb 22, 2018 8:46 pm
- Forum: General Rate Laws
- Topic: 15.3(c)
- Replies: 2
- Views: 394
Re: 15.3(c)
In the textbook, the unique average reaction rate for reaction aA+bB\rightarrow cC+dD is : -\frac{1}{a}\frac{\Delta [A]}{\Delta t} = -\frac{1}{b}\frac{\Delta [B]}{\Delta t} = \frac{1}{c}\frac{\Delta [C]}{\Delta t} = \frac{1}{d}\frac{\Delta [D]}{\Delta t} In problem 15.3, the unique rate of the react...
- Thu Feb 22, 2018 8:32 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Plotting Reaction Rate
- Replies: 2
- Views: 513
Plotting Reaction Rate
Are we going to have to plot the reaction rates (concentration versus time) like the example we did in lecture? If so, is it going to be more specific with precise numbers or is it going to be rough (similar to the example in lecture) to just create a general visual of the change in concentration fo...
- Thu Feb 22, 2018 8:28 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Instantaneous Rate
- Replies: 4
- Views: 660
Instantaneous Rate
What is the value of knowing the instantaneous rate of a reaction? I understand how knowing the average reaction rate would be helpful but I do not understand the importance of knowing the reaction rate at a single point in time.
- Sun Feb 18, 2018 3:59 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell diagram
- Replies: 2
- Views: 397
Re: Cell diagram
You add an inert metallic component (like Pt(s), for example) to the cell with the half reaction that does not have conducting solids. In some reactions, conducting solids such as Zn(s) and Cu(s) are part of the reaction so they make the electrode in that cell and an inert metallic component is not ...
- Sun Feb 18, 2018 3:38 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: w Max Equation
- Replies: 1
- Views: 1943
Re: w Max Equation
The work done when a certain number of moles of electrons travels through a potential difference is their total charge times the potential difference. The charge of one electron is -e so the charge per mole of electrons is -eN A (N A being Avogadro's constant). So putting these together, the work do...
- Sun Feb 18, 2018 3:16 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: "Molar" form/ Pure number
- Replies: 2
- Views: 361
"Molar" form/ Pure number
The textbook writes the equation r = -nrFE. What does the subscript "r" mean? The textbook stated that the subscript "r" is the "molar" form that made nr a pure number, but I do not understand the significance of this either.
- Fri Feb 09, 2018 9:28 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Electrical energy to chemical energy
- Replies: 2
- Views: 421
Electrical energy to chemical energy
Dr. Lavelle said that we are focusing more on Galvanic cells, where a chemical reaction produces an electrical current. However, can someone give an example of the opposite situation, where electrical energy is converted to chemical energy?
- Fri Feb 09, 2018 9:17 am
- Forum: Biological Examples (*DNA Structural Transitions, etc.)
- Topic: Biological systems
- Replies: 7
- Views: 1459
Biological systems
The textbook states that a reaction that produces a lot of entropy can drive a non spontaneous reaction forward, and that this is used extensively in biological systems. Can someone please explain to me how this coupling works? I do not understand how a reaction with excess entropy can make another ...
- Fri Feb 09, 2018 9:08 am
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Entropy Phase Change
- Replies: 2
- Views: 310
Entropy Phase Change
The graph below shows entropy changes having to do with phase changes of a substance. Can someone please explain why entropy increases vertically (AKA why there is a vertical line) at \Delta S fus and \Delta S vap ? [img]https://2012books.lardbucket.org/books/principles-of-general-chemistry-v1.0/sec...
- Fri Feb 09, 2018 8:53 am
- Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
- Topic: Statistical entropy
- Replies: 1
- Views: 240
Statistical entropy
The textbook states that entropy calculated from the Boltzmann formula is statistical entropy. What exactly does this mean?
- Fri Feb 02, 2018 9:15 am
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Trouton's Rule
- Replies: 1
- Views: 336
Trouton's Rule
The textbook states that according to Trouton's Rule, "approximately the same increase in positional disorder occurs when any liquid is converted into a vapor, so we can expect \Delta S to be much the same in each case." Therefore, the value of \Delta S vap is similar for many liquids. Cou...
- Fri Feb 02, 2018 9:05 am
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Assume ideal gas?
- Replies: 4
- Views: 547
Assume ideal gas?
When calculating entropy changes due to changes in volume and temperature of a gas, do we always have to assume that the gas behaves as an ideal gas?
- Fri Feb 02, 2018 9:01 am
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Thermal and positional disorder
- Replies: 2
- Views: 432
Thermal and positional disorder
The textbook refers to thermal disorder as disorder arising from the thermal motion of the molecules and positional disorder as the disorder relating to the locations of the molecules.
Can these be thought of as types, or subcategories, of entropy? If so, are there any other types?
Can these be thought of as types, or subcategories, of entropy? If so, are there any other types?
- Sat Jan 20, 2018 5:11 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Heat Capacity for atoms and molecules
- Replies: 1
- Views: 143
Heat Capacity for atoms and molecules
In the textbook, a table is given with equations for the molar heat capacities of atoms, linear molecules, and nonlinear molecules in terms of constant volume and constant pressure. Why do CV,m and CP,m have different equations for atoms, linear molecules, and nonlinear molecules?
- Sat Jan 20, 2018 5:08 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Heat capacity for monatomic ideal gas
- Replies: 2
- Views: 292
Heat capacity for monatomic ideal gas
The book states that for a monatomic ideal gas, both Cp and Cv are independent of temperature and pressure. Would someone please break this down for me?
- Sat Jan 20, 2018 4:55 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Heat "flow" [ENDORSED]
- Replies: 1
- Views: 320
Heat "flow" [ENDORSED]
The textbook remarks that it is incorrect to say that heat "flows." Why is this incorrect/ what is the reasoning behind this statement?
- Sat Jan 20, 2018 4:44 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Reversible Processes
- Replies: 2
- Views: 369
Re: Reversible Processes
When a system is at equilibrium, an infinitesimal change in a variable can cause the process to reverse. I do not know if this correlates exactly, but I like to think of it this way: Let's say you have two piles of rocks that weigh the same amount and are each placed on one side of a see-saw. The se...
- Tue Jan 16, 2018 8:41 am
- Forum: Phase Changes & Related Calculations
- Topic: Heat and Enthalpy
- Replies: 3
- Views: 432
Re: Heat and Enthalpy
The equation for enthalpy, H, is H=U+PV, where U is internal energy, P is pressure, and V is volume. U, P, and V are all state functions, so enthalpy (with equation H=U+PV) must be a state function as well. Heat is not a state function because it DOES matter what path is taken to achieve the change ...
- Sat Jan 13, 2018 8:32 am
- Forum: Phase Changes & Related Calculations
- Topic: Sublimation
- Replies: 4
- Views: 2451
Sublimation
How does sublimation occur? In other words, how can a subliming substance just skip the liquid phase?
- Sat Jan 13, 2018 8:21 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Periodic Trend for Heat Capacity
- Replies: 2
- Views: 797
Periodic Trend for Heat Capacity
Is there a periodic trend for heat capacity? Does heat capacity relate to size of the atom, the electronegativity of the atom, etc.?
- Sat Jan 13, 2018 8:12 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: q=mCdeltaT
- Replies: 2
- Views: 5563
q=mCdeltaT
Hello! How many different versions of this equation: are there? I know there are different heat capacities and different units of measurement, but I do not know if I am aware of all the options.
- Sun Nov 26, 2017 4:17 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Equilibrium Constant units
- Replies: 2
- Views: 317
Equilibrium Constant units
Why doesn't the equilibrium constant, K, have units? In previous chapters, the constants have had units (such as Planck's constant), so why is this one different?
- Sun Nov 26, 2017 4:09 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Polydentate ligands
- Replies: 2
- Views: 421
Polydentate ligands
If a ligand is polydentate, does it have to have molecules binding to every binding site available when making compounds? In other words, if a ligand is hexadentate, does it need six atoms/molecules to bind to it or can there be less?
- Thu Nov 02, 2017 7:50 pm
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Increasing Covalent Character of Silver Halides
- Replies: 1
- Views: 1773
Increasing Covalent Character of Silver Halides
I am still a little confused as to why the covalent character of silver halides increases as you go down the group of halides (for example, from AgF to AgCl to AgBr). Please clarify :)
Thank you!
Thank you!
- Sun Oct 29, 2017 5:25 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Electron Spins [ENDORSED]
- Replies: 2
- Views: 555
Electron Spins [ENDORSED]
Why do electrons with parallel spins tend to avoid each other and occupy different orbitals? Why would the direction of spin influence this repulsion?
- Sun Oct 29, 2017 5:17 pm
- Forum: Ionic & Covalent Bonds
- Topic: Noble Gases
- Replies: 6
- Views: 863
Noble Gases
I know that noble gases have a completely filled outer shell and are therefore stable. However, can noble gases ever form bonds and create compounds?
- Fri Oct 20, 2017 3:56 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Effective Nuclear Charge
- Replies: 1
- Views: 330
Effective Nuclear Charge
Today in lecture Professor Lavelle used the term "effective nuclear charge." He used it in relation to the inner electrons shielding the outer electrons from the electrostatic attraction of the nucleus, but the meaning of the term is still unclear to me. Can someone please further explain ...
- Fri Oct 20, 2017 3:52 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Electrostatic potential energy [ENDORSED]
- Replies: 2
- Views: 270
Electrostatic potential energy [ENDORSED]
Hello! Today in lecture Professor Lavelle gave this equation: Ep is proportional to (q1)(q2) / r I understand that Ep represents electrostatic potential energy, q represents charge, and r represents distance. However, I need further clarification. What charges are we talking about and what is the di...