## Search found 56 matches

Sat Mar 17, 2018 1:04 pm
Forum: *Alkanes
Topic: Tips and Tricks for remembering Functional Groups?
Replies: 2
Views: 479

### 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: 123

### 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]
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: 114

### 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: 114

### 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: 302

### 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?
Fri Mar 16, 2018 12:39 am
Forum: Calculating Work of Expansion
Topic: Irreversible Expansion vs. Reversible Expansion
Replies: 2
Views: 359

### 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: 179

### 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: 197

### 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: 147

### 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
Replies: 2
Views: 228

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: 304

### 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: 163

### 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: 666

### 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: 2133

### 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: 165

### 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: 124

### 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: 200

### 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: 244

### 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: 269

### 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: 172

### 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: 509

### 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: 256

### 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: 590

### 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: 633

### 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: 224

### 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: 607

### 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: 726

### 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: 159

### 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: 193

### 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
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: 149

### 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: 280

### 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: 178

### 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: 5607

### 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
Sat Jan 13, 2018 9:12 pm
Forum: Phase Changes & Related Calculations
Topic: Extensive/Intensive
Replies: 5
Views: 710

### 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: 1112

### 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: 484

### 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: 593

### 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: 397

### 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: 2
Views: 778

### 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: 5215

### 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: 339

### 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: 302

### 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: 7870

### 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: 217

### 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: 389

### 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: 169

### 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: 928

### 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: 291

### 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: 277

### 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
Replies: 1
Views: 212

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
Replies: 6
Views: 579

### 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: 1307

### 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: 168

### 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: 526

### 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: 648

### 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: 749

### 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.