Search found 56 matches
- Sat Mar 17, 2018 1:04 pm
- Forum: *Alkanes
- Topic: Tips and Tricks for remembering Functional Groups?
- Replies: 2
- Views: 4073
Re: Tips and Tricks for remembering Functional Groups?
In addition to what was said above, I remember based off each functional group. Here is a list of the ones we learned in class. When there is an OH (hydroxyl group) : - Alcohol (there is an OH group at the end of a carbon chain), ex. C-OH For an O single bonded to 2 carbon s: - Ether (O is in the mi...
- Fri Mar 16, 2018 11:28 pm
- Forum: General Rate Laws
- Topic: Test 3 #5
- Replies: 1
- Views: 340
Test 3 #5
Given the instantaneous rate of reaction is 1.43 * 10^-2, and the initial mass of each reactant is 0.6 confined to a 750 mL vessel, how do you find the rate constant?
The rate law is rate = k [NO]^2 [O2]
The rate law is rate = k [NO]^2 [O2]
- Fri Mar 16, 2018 11:25 pm
- Forum: General Rate Laws
- Topic: Finding the effect on the rate when changing the amount of reactant (test 3 #5)
- Replies: 1
- Views: 291
Re: Finding the effect on the rate when changing the amount of reactant (test 3 #5)
Are you supposed to just determine it based on the rate equation, so that doubling oxygen makes the rate 1/2 slower, or halving the amount of NO makes the rate 1/4?
- Fri Mar 16, 2018 11:24 pm
- Forum: General Rate Laws
- Topic: Finding the effect on the rate when changing the amount of reactant (test 3 #5)
- Replies: 1
- Views: 291
Finding the effect on the rate when changing the amount of reactant (test 3 #5)
The problem is: Given: 2NO + O2 = 2NO2 The rate of the reaction was first order wrt O2, and the rate was second order wrt nitrogen monoxide. How are you supposed to find the effect of changing the amount of oxygen/amount of nitrogen monoxide? More specifically, How do you find out what happens to th...
- Fri Mar 16, 2018 12:56 am
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Temperature in Entropy Change for Monoatomic Ideal Gas Midterm Question 6B
- Replies: 2
- Views: 604
Temperature in Entropy Change for Monoatomic Ideal Gas Midterm Question 6B
Hi,
This question asks to calculate the entropy change for a monoatomic ideal gas at 1 atm, 303 K, and in a balloon of 53.48 L when the gas is heated to 333 K at a constant volume.
When calculating the n=PV/RT, why do you use the initial temperature instead of the final temperature?
This question asks to calculate the entropy change for a monoatomic ideal gas at 1 atm, 303 K, and in a balloon of 53.48 L when the gas is heated to 333 K at a constant volume.
When calculating the n=PV/RT, why do you use the initial temperature instead of the final temperature?
- Fri Mar 16, 2018 12:39 am
- Forum: Calculating Work of Expansion
- Topic: Irreversible Expansion vs. Reversible Expansion
- Replies: 2
- Views: 582
Irreversible Expansion vs. Reversible Expansion
I'm still kind of confused going, how can you tell if something is expanding irreversibly vs. reversibly?
- Tue Mar 13, 2018 1:08 am
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Arrhenius Equation, Temperature, and Rate Constants
- Replies: 1
- Views: 382
Arrhenius Equation, Temperature, and Rate Constants
I'm still kind of confused. How do the rate constants at different temperatures relate to the Arrhenius equation, and how do you solve these problem types where you need to determine either a rate constant or the activation energy. Basically, how do you set up with Arrhenius equation with rate const...
- Sat Mar 10, 2018 11:39 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: SN2 Organic Reaction
- Replies: 3
- Views: 415
Re: SN2 Organic Reaction
Why is it important to study the SN2 reaction in the chemical kinetics section?
- Sat Mar 10, 2018 11:37 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Rate determining step
- Replies: 2
- Views: 358
Re: Rate determining step
When using the pre-equilibrium approach, you are trying to make sure that the proposed rate law is the same as the experimentally determined rate law. You use the pre-equilibrium approach to reason what the rate law for the equation is when the slow step has a reaction intermediate in it. By using t...
- Sat Mar 10, 2018 11:13 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Steady-state vs. Pre-equilibrium [ENDORSED]
- Replies: 2
- Views: 514
Re: Steady-state vs. Pre-equilibrium [ENDORSED]
In a steady state approach, a constant intermediate concentration (the d[intermediate]/dt = 0). The pre-equilibrium approach means the reaction before the rate-limiting step is at equilibrium, so you can use the equilibrium constant K. The pre-equilibrium approach is less flexible because it applies...
- Sat Mar 03, 2018 6:40 pm
- Forum: General Rate Laws
- Topic: Test 3 - Derivations
- Replies: 4
- Views: 692
Re: Test 3 - Derivations
Yes, if you look at the chemical kinetics outline one of the bullets says "Know how to derive the differential and integrated rate laws for zero, 1st and 2nd order reactions and know how to derive their respective half-life equations."
- Sat Mar 03, 2018 6:36 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Proposing Reaction Mechanisms [ENDORSED]
- Replies: 1
- Views: 351
Proposing Reaction Mechanisms [ENDORSED]
Are we supposed to be able to know how propose reaction mechanisms?
- Sat Mar 03, 2018 6:21 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Rate Constant Units
- Replies: 9
- Views: 1338
Rate Constant Units
How do we tell what the units for the rate constant are based on the order of the reaction?
- Sun Feb 25, 2018 2:37 am
- Forum: Zero Order Reactions
- Topic: Concept of Zero Order
- Replies: 5
- Views: 2538
Re: Concept of Zero Order
Another example of a zero order reaction is the decomposition of nitrous oxide to n2 gas and o2 gas.
- Sun Feb 25, 2018 2:34 am
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: Importance of K
- Replies: 2
- Views: 374
Importance of K
Why is it important theoretically to know what k is/does? What is its relation in terms to the reaction?
- Mon Feb 19, 2018 9:34 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: 14.21 and Cell Diagrams/Standard Potentials
- Replies: 1
- Views: 237
14.21 and Cell Diagrams/Standard Potentials
How come for both of the half reactions derived from the cell diagram, you add the electron in both cases? Shouldn't the left side of the cell diagram be an oxidation reaction, in which the species loses an electron instead of gaining an electron?
- Wed Feb 14, 2018 1:32 am
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Relationship between Internal Energy, Temperature, Work, and Heat
- Replies: 1
- Views: 456
Relationship between Internal Energy, Temperature, Work, and Heat
I know that the change in internal energy is equal to q+w (the first law of thermodynamics). Where does temperature come into play with this (specifically regarding isothermal processes)? How come when the change in internal energy is zero, the change in temperature is also zero, but work and heat h...
- Wed Feb 14, 2018 1:07 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: Third Law Clarification/ Practice Midterm Question 3E
- Replies: 2
- Views: 461
Third Law Clarification/ Practice Midterm Question 3E
Why is it false that molecules at exactly 0 degrees Kelvin have no entropy? In theory, isn't the third law of thermodynamics that the entropy of a perfect crystal is zero when the temperature is equal to absolute zero (0 K)?
- Wed Feb 14, 2018 12:45 am
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Practice Midterm #3b Equation
- Replies: 3
- Views: 505
Practice Midterm #3b Equation
What equation do you use to find the final pressure after knowing the total volume is 11.0L in #3 of the practice midterm (where delta S was 33.0 J/K)?
- Sat Feb 10, 2018 11:45 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: 9.13
- Replies: 1
- Views: 373
9.13
Why do we use 5/2 instead of 3/2 for the ideal diatomic gas?
- Sat Feb 10, 2018 11:37 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Concept of Second Law of Thermodynamics
- Replies: 6
- Views: 965
Concept of Second Law of Thermodynamics
My notes are a little confusing. What exactly is the second law of thermodynamics? I know it has to do with entropy, but what about it?
- Sat Feb 10, 2018 11:17 pm
- 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: Degeneracy (W)
- Replies: 4
- Views: 521
Degeneracy (W)
How do you calculate the degeneracy of something?
- Fri Feb 02, 2018 3:16 pm
- Forum: Van't Hoff Equation
- Topic: Van't Hoff Eq.
- Replies: 5
- Views: 1045
Re: Van't Hoff Eq.
From what we learned in class today, I'm assuming we only need to know how to use the equation when delta S and delta H are held constant.
- Fri Feb 02, 2018 3:15 pm
- Forum: Calculating Work of Expansion
- Topic: Work Equations [ENDORSED]
- Replies: 9
- Views: 1446
Re: Work Equations [ENDORSED]
Do we need to know how to derive these equations/the reasoning that's involved to come up with the equations ourselves?
- Fri Feb 02, 2018 3:12 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gibbs Free Energy Equations
- Replies: 3
- Views: 603
Gibbs Free Energy Equations
Can someone go over a summary of a situation you should use each Gibbs equation in?
- Sat Jan 27, 2018 8:48 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Degeneracy (W) [ENDORSED]
- Replies: 8
- Views: 1270
Degeneracy (W) [ENDORSED]
Can someone quickly explain the concept of/meaning of degeneracy?
- Sat Jan 27, 2018 8:46 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Irreversible vs. Reversible [ENDORSED]
- Replies: 10
- Views: 1574
Re: Irreversible vs. Reversible [ENDORSED]
When you think of an irreversible or reversible process, think in terms of the piston and external pressure example. In one, the system had 2 atm and the Pexternal was 2 atm. In the other, the system had 2 atm and the Pexternal was 1 atm. In the first example, the pressures are at thermal equilibriu...
- Sat Jan 27, 2018 8:42 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Second Law Explanation
- Replies: 1
- Views: 392
Second Law Explanation
Can someone explain to me briefly what the second law of thermodynamics is for and why we use it?
- Sat Jan 20, 2018 6:05 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: change in internal energy
- Replies: 4
- Views: 324
Re: change in internal energy
The fundamental equation necessary to understand this is that U = q + w (deltas implied)
When there is no work done on the system, U = q
When there is no heat transferred to or from the system, U = w
When there is no work done on the system, U = q
When there is no heat transferred to or from the system, U = w
- Sat Jan 20, 2018 6:01 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: When is the change in work or heat = to zero?
- Replies: 2
- Views: 277
When is the change in work or heat = to zero?
How do you know that the work is equal to zero while using a bomb calorimeter? like in question 8.53
- Sat Jan 20, 2018 4:58 pm
- Forum: Calculating Work of Expansion
- Topic: Irreversible and Reversible Processes
- Replies: 4
- Views: 509
Re: Irreversible and Reversible Processes
In class, the example Dr. Lavelle used was with two systems compressed with pistons. Irreversible expansion: will have sudden expansion (results in a large change in volume) Pressure of external atmosphere- 1 atm Pressure of system- 2 atm Reversible expansion: system will change slowly (results a ve...
- Sun Jan 14, 2018 4:09 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Work
- Replies: 1
- Views: 375
Work
How can you tell whether or not work was done on the system of if the system did work?
- Sat Jan 13, 2018 10:10 pm
- Forum: Phase Changes & Related Calculations
- Topic: Endo and Exothermic Ways to Remember
- Replies: 28
- Views: 11657
Re: Endo and Exothermic Ways to Remember
think in terms of where the heat is added or where the heat is released.
endothermic
A+HEAT-> B+C
exothermic
A+B -> HEAT + C
endothermic
A+HEAT-> B+C
exothermic
A+B -> HEAT + C
- Sat Jan 13, 2018 9:12 pm
- Forum: Phase Changes & Related Calculations
- Topic: Extensive/Intensive
- Replies: 5
- Views: 1684
Extensive/Intensive
Can someone explain the difference and why it is important to know this property?
- Sat Jan 13, 2018 9:11 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Bomb Calorimetry
- Replies: 4
- Views: 1849
Bomb Calorimetry
Can someone explain how bomb calorimetry works/the main differences as to why it is different from coffee cup calorimetry?
- Sat Dec 09, 2017 6:12 pm
- Forum: Acidity & Basicity Constants and The Conjugate Seesaw
- Topic: Assumption for Subtracting X in Ka or Kb calculation [ENDORSED]
- Replies: 3
- Views: 834
Assumption for Subtracting X in Ka or Kb calculation [ENDORSED]
For ICE charts we make, what is the reasoning for why we assume there is little change (so little that it is negligible) if Ka is small?
- Sat Dec 09, 2017 5:56 pm
- Forum: Air Pollution & Acid Rain
- Topic: Acid Rain for Final [ENDORSED]
- Replies: 1
- Views: 786
Acid Rain for Final [ENDORSED]
For the final, should we know toolbox 12.1? I know we didn't really cover acid rain in lecture/discussion, so I was wondering if any actual questions would be asked about the impact of acid rain/chemical reactions that influence acid rain.
- Sat Dec 09, 2017 5:49 pm
- Forum: Acidity & Basicity Constants and The Conjugate Seesaw
- Topic: Strengths of Acids
- Replies: 2
- Views: 596
Strengths of Acids
Can anyone help explain to me how we are supposed to classify acid strength given something like a group of different acids? I keep reading that for oxoacids, the greater the number of highly electronegative atoms attatched to the central atom, the stronger the acid is, but I don't really understand...
- Sat Dec 09, 2017 2:24 pm
- Forum: *Crystal Field Theory
- Topic: Coordination Complex
- Replies: 3
- Views: 1515
Re: Coordination Complex
I think that for Chem 14A we are not expected to know Crystal Field Theory, however the basic concept is that ligands as they approach the metal ion experience greater repulsion and cause crystal field splitting. In a d to d transition, an electron in is excited by a photon to another d orbital of h...
- Fri Dec 08, 2017 5:07 pm
- Forum: Properties of Electrons
- Topic: Velocity of Ejected electron
- Replies: 4
- Views: 14659
Velocity of Ejected electron
Hi I had a question about the work function, specifically from #7 part b on the second quiz that we took. I know we were supposed to use the formula Ek=1/2*m*v^2, but were we supposed to use the work function at all during this part? What exactly is the work function other than being the threshold e...
- Sat Dec 02, 2017 5:11 pm
- Forum: Bronsted Acids & Bases
- Topic: Bronsted Acid vs Lewis Acid [ENDORSED]
- Replies: 3
- Views: 637
Re: Bronsted Acid vs Lewis Acid [ENDORSED]
No, the only difference is the definition. The Bronsted acid is a proton donor, the Bronsted base is a proton acceptor. A Lewis acid is an electron pair acceptor, while a lewis base is an electron pair donor. The Lewis definitions are broader than Bronsted definitions. The Bronsted definitions are m...
- Sat Dec 02, 2017 5:02 pm
- Forum: Conjugate Acids & Bases
- Topic: conjugates
- Replies: 2
- Views: 524
Re: conjugates
An acid donates a proton (H+); once it donates the proton, the remaining species is a conjugate base. A base accepts a proton (H+); once it accepts the proton, the remaining species is the conjugate acid.
- Sat Nov 25, 2017 8:04 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Polarity of NH3?
- Replies: 4
- Views: 26310
Re: Polarity of NH3?
Remember that NH3's lewis structure is a central nitrogen atom, attached to 3 hydrogen atoms and with one lone pair of electrons. The molecule is polar because the molecule is not symmetrical. There is a lone pair on the nitrogen, so the dipoles cannot cancel.
- Sat Nov 25, 2017 8:02 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: 4.25 (b)- Polarity
- Replies: 2
- Views: 407
Re: 4.25 (b)- Polarity
The bonds between the C and Cl are polar because there is a large dipole due to the difference in electronegativity, but the molecule itself is nonpolar.
- Sat Nov 18, 2017 10:01 pm
- Forum: Bond Lengths & Energies
- Topic: Regions of Electron Density
- Replies: 4
- Views: 838
Re: Regions of Electron Density
Regions of electron density can be thought of the parts of the Lewis structure where you put either a bond (or multiple bonds) or a lone pair of electrons. If you are thinking about molecular shape and structure, a double bond would count as one region of electron density.
- Sat Nov 18, 2017 9:55 pm
- Forum: Naming
- Topic: Naming Ligands
- Replies: 1
- Views: 257
Re: Naming Ligands
I would assume you should know all the ligands in the spectrochemical series. You should definitely be familiar with the common ligands like water, ammonia, hydroxide, and the halogens.
- Sun Nov 12, 2017 4:00 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Shape Memorization [ENDORSED]
- Replies: 7
- Views: 1988
Re: Shape Memorization [ENDORSED]
It's fairly easy to remember the shapes when you classify molecules by their electron domain geometry. Try to visualize the structures Dr. Lavelle showed during lectures to remember the names. Molecules with the same formula have the same general shape (bond angles may differ slightly). For example:...
- Sun Nov 12, 2017 3:45 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: VSEPR Notation
- Replies: 3
- Views: 587
Re: VSEPR Notation
Basically there is the electron domain geometry and the actual shape of the molecule. The electron domain formula is AX n , where n is the number of domains. The number of domains includes both the lone pairs and the bonded pairs around the central atom. To determine the shape, the same basic concep...
- Mon Nov 06, 2017 12:21 am
- Forum: Resonance Structures
- Topic: Resonance structure and formal charges
- Replies: 2
- Views: 429
Re: Resonance structure and formal charges
I find that it's the easiest to remember the formula (FC=V-L+S/2), where the number of valence electrons is V, the number of of bonding electrons are S, and the number of lone pair electrons is L. A formal charge of 0 is the most stable.
- Mon Nov 06, 2017 12:19 am
- Forum: Octet Exceptions
- Topic: Designating radicals [ENDORSED]
- Replies: 1
- Views: 434
Re: Designating radicals [ENDORSED]
Yes, radicals are normally designated with one dot next to the element name (in free radical halogenation, the radical is designated by Cl with one dot). A radical is a compound with an unpaired electron.
- Mon Oct 23, 2017 9:09 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Understadning Heisenberg Indeterminacy Equation
- Replies: 6
- Views: 1376
Re: Understadning Heisenberg Indeterminacy Equation
We do not know the precise location of a particle if it behaves like a wave, and we can't specify the location of a particle with a precise linear momentum. The Heisenberg Uncertainty Principle is meant to explain how we cannot know both location and momentum simultaneously. The equation then hopes ...
- Mon Oct 23, 2017 8:57 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: The 4 Quantum Numbers [ENDORSED]
- Replies: 5
- Views: 3242
Re: The 4 Quantum Numbers [ENDORSED]
Can someone describe more about how to deduce what l and m sub l is when you know what n is? I'm still kind of confused.
- Sat Oct 14, 2017 8:14 pm
- Forum: Properties of Electrons
- Topic: Scientists/Experiments [ENDORSED]
- Replies: 1
- Views: 292
Scientists/Experiments [ENDORSED]
Does anyone think we will be tested on scientists in the textbook (Rutherford, Millikan, Geiger, and Marsden)? I know that they had contributions to explaining subatomic particles, but I'm not sure if we will need to know them to explain different properties of electrons.
- Sat Oct 14, 2017 5:28 pm
- Forum: Photoelectric Effect
- Topic: Confused about photoelectric effect! [ENDORSED]
- Replies: 6
- Views: 986
Re: Confused about photoelectric effect! [ENDORSED]
It's important to understand that the photoelectric effect experiment shined light on a metal surface to try and measure the energy needed to remove electrons from different metals. This experiment was important because it had an unexpected outcome; the experiment showed that unless E(photon)is grea...
- Thu Oct 05, 2017 7:16 pm
- Forum: Molarity, Solutions, Dilutions
- Topic: Homework Problem G23
- Replies: 2
- Views: 1226
Homework Problem G23
In the problem, "A lab technician has made up a 100.0mL solution containing 0.50g NaCl and 0.30g of KCl, as well glucose and other sugars.This question asks that we find the concentration of the chloride ions in the solution. How do you go about solving this problem/what steps do you need to ta...
- Thu Oct 05, 2017 12:55 pm
- Forum: Significant Figures
- Topic: Number of sig figs in answer
- Replies: 8
- Views: 1198
Re: Number of sig figs in answer
Should we be rounding w/ significant figures in every calculation in a problem or just in our final answer? My TA told me that we should, but I recalled Dr. Lavelle saying that we only needed to acknowledge sig figs in our final answer.