## Search found 51 matches

Sat Mar 17, 2018 9:57 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Collision Theory
Replies: 5
Views: 427

### Collision Theory

For the final, how in depth do we need to know collision theory?
Sat Mar 17, 2018 9:08 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: >> [ENDORSED]
Replies: 2
Views: 408

### >>[ENDORSED]

What does >> or << mean?
Sat Mar 17, 2018 7:30 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Stoichiometric coefficients
Replies: 4
Views: 611

### Stoichiometric coefficients

Are stoichiometric coefficients used for elementary reactions? In the book, it states that they are not. However, in lecture, Lavelle has provided examples where there are coefficients in the elementary reactions of a mechanism.
Sun Mar 11, 2018 10:42 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Midterm Question 5 (Step 2)
Replies: 2
Views: 285

### Re: Midterm Question 5 (Step 2)

The question states "as it returns to the original internal energy". It was calculated, in step 1, that the change in internal energy was -158 so to return to the original internal energy, step 2 internal energy would have to be the opposite, +158J.
Sun Mar 11, 2018 10:35 pm
Forum: Phase Changes & Related Calculations
Topic: Exothermic Reaction
Replies: 3
Views: 246

### Re: Exothermic Reaction

The temperature will not change during a phase change. All of the energy being lost is due to a substance changing from one state to another. The energy is used as work to break or form bonds of the molecule.
Sun Mar 11, 2018 10:28 pm
Forum: Van't Hoff Equation
Topic: Derivation
Replies: 5
Views: 490

### Re: Derivation

I am pretty sure you do not need to know the derivation of the equation, just the equation itself. So memorize the equation and you will be good to go.
Tue Mar 06, 2018 10:04 pm
Forum: Zero Order Reactions
Topic: Finding 1/2 or negative orders
Replies: 2
Views: 287

### Re: Finding 1/2 or negative orders

you would use the data on the table just as you would for a positive whole number order.
Sun Mar 04, 2018 10:52 pm
Forum: First Order Reactions
Topic: half-lives
Replies: 4
Views: 279

### half-lives

What is the importance of half-lives? Like why is it significant to know the time needed for the concentration to be half of the initial, why not just calculate the time needed for the concentration to reach zero?
Sun Mar 04, 2018 10:34 pm
Forum: General Rate Laws
Topic: solving for a
Replies: 2
Views: 192

### solving for a

When solving for (a) in rate reaction problems, will the answer always be a whole number or 1,2,etc...?
Sun Mar 04, 2018 9:55 pm
Forum: General Rate Laws
Topic: a value
Replies: 3
Views: 262

### a value

I am still confused how to determine/calculate the a value of a reaction. can someone please explain this to me?
Sun Feb 25, 2018 10:46 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Cell Potential
Replies: 4
Views: 277

### Re: Cell Potential

hydrogen's cell potential is zero so that it is possible to calculate the cell potential of the other electrode. Standard potentials only give us the overall cell potential and not just one electrode. Therefore, we arbitrarily set the standard potential of hydrogen to zero at all temperatures.
Sun Feb 25, 2018 10:42 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagrams
Replies: 4
Views: 341

### Re: Cell Diagrams

Anodes are always on the left and cathodes are always on the right. To figure out which is which you have to determine which reactant is being oxidized and which is being reduced, so look at the electrons.
Sun Feb 25, 2018 10:40 pm
Forum: General Rate Laws
Topic: rate constants
Replies: 7
Views: 493

### rate constants

how are rate constants calculated and what do they represent?
Sun Feb 25, 2018 10:26 pm
Forum: General Rate Laws
Topic: Unique Average Rates
Replies: 1
Views: 146

### Re: Unique Average Rates

I think the unique average rate is just specific to the question/ reaction you are given. So when they ask for the unique average rate of the reaction, they are talking specifically about that certain reaction with those stoichiometric coefficients. When you calculate the average rate, the coefficie...
Sun Feb 25, 2018 10:06 pm
Forum: General Rate Laws
Topic: Negative Sign [ENDORSED]
Replies: 7
Views: 473

### Re: Negative Sign[ENDORSED]

you are finding the average rate of consumption. So, because the reactants are being consumed the delta A or R is going to be negative. For chemical kinetics, the rate is always going to be positive, hence the negative sign.
Sun Feb 11, 2018 11:22 pm
Forum: Phase Changes & Related Calculations
Topic: Lyndons practice midterm
Replies: 3
Views: 300

### Lyndons practice midterm

Can someone please explain to me this concept: "True/False: One cannot calculate the entropy of vaporization for water at room temperature because water has a boiling point of 373K."?
Fri Feb 09, 2018 12:20 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Different Gibbs Free Energy values
Replies: 1
Views: 161

### Different Gibbs Free Energy values

How come you get two different Gibbs free energy values when you solve them using the equation G = H - TS vs G(products) -G(reactants) ?
Thu Feb 08, 2018 11:38 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Entropy
Replies: 7
Views: 407

### Entropy

What is the difference between S°m, S°r, and S°f?
Sun Feb 04, 2018 6:13 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 9.65
Replies: 2
Views: 189

### 9.65

In problem 9.65, what determines the stability of an element? Like what variable measures that and how are we supposed to calculate that?
Sun Feb 04, 2018 6:08 pm
Forum: Calculating Work of Expansion
Topic: Calculating work of expansion on the exam
Replies: 2
Views: 179

### Calculating work of expansion on the exam

If Dr. Lavelle doesn't allow calculators on exams, then how are we supposed to calculate any problem that requires solving an integral?
Sun Feb 04, 2018 6:03 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 9.35
Replies: 4
Views: 223

### Re: 9.35

Think about entropy in a manner of disorder. If things are not vibrating, they are stuck in place and orderly. However, if they are vibrating, there is more movement in general, meaning that there is more disorder and entropy.
Sun Jan 28, 2018 11:39 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 9.3
Replies: 5
Views: 372

### Re: 9.3

when heat is exiting the system, heat is being lost so it is negative. When additional heat is entering a system, heat is being added, hence the positive sign.
Sun Jan 28, 2018 11:28 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: ideal cooler [ENDORSED]
Replies: 5
Views: 370

### ideal cooler[ENDORSED]

What does it mean by "ideal" when a system is an ideal cooler?
Tue Jan 23, 2018 8:50 pm
Forum: Phase Changes & Related Calculations
Replies: 1
Views: 181

Can someone explain to me or give me an example of how energy could be transferred to or from a system as work in an adiabatic container?
Sun Jan 21, 2018 11:10 pm
Forum: Phase Changes & Related Calculations
Topic: ΔU vs. ΔH
Replies: 10
Views: 1418

### Re: ΔU vs. ΔH

I also was wondering what the relationship between the two was. Like are they completely different variables or do they work together?
Sun Jan 21, 2018 9:59 pm
Forum: Phase Changes & Related Calculations
Topic: heat vs ΔH vs work
Replies: 2
Views: 190

### heat vs ΔH vs work

Just for clarification, what is the difference between ΔH, work, and heat? (Conceptually)
Sun Jan 21, 2018 8:47 pm
Forum: Phase Changes & Related Calculations
Topic: Irreversible vs reversible
Replies: 3
Views: 240

### Irreversible vs reversible

Can someone please explain to me the difference between irreversible and reversible processes? I am still a little confused on the concept part of it.
Sun Jan 14, 2018 10:23 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: U vs H
Replies: 2
Views: 126

### U vs H

what is the difference between delta H and delta U? also, what units do you use for each?
Sun Jan 14, 2018 10:21 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard States
Replies: 4
Views: 398

### Standard States

How do you know an element's standard state? are you just supposed to memorize them or...?
Sun Jan 14, 2018 10:19 pm
Forum: Phase Changes & Related Calculations
Topic: Temperature during phase change
Replies: 2
Views: 158

### Temperature during phase change

I understand that the temperature remains constant during phase changes, but then why does the temperature increase of water from when it melts to when it is boiling?
Thu Dec 07, 2017 1:40 pm
Forum: Bronsted Acids & Bases
Topic: Protons/ H+
Replies: 1
Views: 130

### Protons/ H+

In Bronsted acid and Base equations will the proton always be in the form of H+ or could it be something else as well?
Thu Dec 07, 2017 1:38 pm
Forum: Lewis Acids & Bases
Topic: Self-Test 12.2A
Replies: 1
Views: 171

### Self-Test 12.2A

Can someone explain how NO2- is a Lewis base in the reaction HNO2 + HPO4(2-) --> & <-- NO2- + H2PO4-? like how does NO2- have two electrons to donate?
Sun Dec 03, 2017 11:39 pm
Forum: Bronsted Acids & Bases
Topic: water [ENDORSED]
Replies: 2
Views: 212

### water[ENDORSED]

How can water act as a base and an acid?
Sun Dec 03, 2017 11:30 pm
Forum: Bronsted Acids & Bases
Topic: Bronsted vs. Lewis
Replies: 4
Views: 351

### Bronsted vs. Lewis

What is the difference between Bronsted and Lewis acids?
Sun Nov 26, 2017 11:57 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Bond Order
Replies: 5
Views: 399

### Re: Bond Order

whenever there is a decimal, there is a resonance structure meaning that the bond strength is between either a single bond and a double bond, or a double bond and a triple bond
Sun Nov 26, 2017 11:55 pm
Forum: Hybridization
Topic: Question 4.95
Replies: 2
Views: 220

### Re: Question 4.95

the 2 is the principle quantum number (n)
Sun Nov 19, 2017 11:28 pm
Forum: Hybridization
Topic: Hybrid orbitals
Replies: 3
Views: 286

### Hybrid orbitals

How do you draw/fill orbitals? like in what order?
Sun Nov 19, 2017 11:27 pm
Forum: Hybridization
Topic: Sigma Bond
Replies: 3
Views: 306

### Sigma Bond

why can there only be one sigma bond?
Mon Nov 13, 2017 12:57 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Memorization
Replies: 5
Views: 413

### Memorization

With the molecular shape and VSEPR, would it be just easier to memorize the different angles and shapes and names for the test?
Mon Nov 13, 2017 12:53 am
Forum: Ionic & Covalent Bonds
Topic: different types of bonds
Replies: 6
Views: 480

### different types of bonds

how do you know if a bond is ionic, polar, or nonpolar?
Sun Nov 05, 2017 11:26 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge and stability [ENDORSED]
Replies: 7
Views: 4519

### Formal Charge and stability[ENDORSED]

What is the relation between formal charge and stability of the structure?
Sun Nov 05, 2017 11:25 pm
Forum: Octet Exceptions
Topic: Incomplete Octet
Replies: 1
Views: 252

### Incomplete Octet

I am still unsure about the concept behind the incomplete octet of boron trifluoride. I know what it says in the book, can anyone explain this in further detail?
Sun Oct 29, 2017 11:59 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Electron affinity
Replies: 4
Views: 288

### Re: Electron affinity

Electron affinity is equal to the negative change in energy.
Sun Oct 29, 2017 11:44 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Spin of electron [ENDORSED]
Replies: 2
Views: 211

### Spin of electron[ENDORSED]

When writing the arrows denoting the spin of the electron, does it matter if you draw the arrow facing upwards or downwards first?
Sun Oct 29, 2017 11:42 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Super Octet [ENDORSED]
Replies: 2
Views: 2264

### Super Octet[ENDORSED]

I am confused on the concept of a super octet. I thought there could only be up to 8 electrons in the outer shell. So, how is a super octet formed?
Mon Oct 16, 2017 10:27 pm
Forum: Properties of Light
Topic: Lyman and Balmer series.
Replies: 4
Views: 319

### Lyman and Balmer series.

Will we need to know about the Lyman or Balmer series for the test?
Sun Oct 15, 2017 9:56 pm
Forum: Properties of Light
Topic: Speed of Light Constant
Replies: 18
Views: 1056

### Re: I don't know how to post my own topic

Kayla Ikemiya 1H wrote:Can someone please explain how to start a new topic on this please? I also don't understand 30 C on the post module for Photoelectric effect
you have to go to board index --> chem 14a --> select which topic your question pertains to and then click post a new topic
Sun Oct 15, 2017 9:55 pm
Forum: Properties of Light
Topic: Speed of Light Constant
Replies: 18
Views: 1056

### Re: Speed of Light Constant

Since 3.00 x 10^8 m/s is the constant that Dr. Lavelle uses in lecture, I think it is safe to use that on our homework and on tests since the TAs grade them and they know what Lavelle has taught us (i.e 3.00 x 10^8 m/s).
Sun Oct 15, 2017 9:50 pm
Topic: Black body for quiz 2 [ENDORSED]
Replies: 11
Views: 1107

### Re: Black body for quiz 2[ENDORSED]

He did not go over it during lecture very much, so I am sure it is not needed for the test.
Sun Oct 15, 2017 5:54 pm
Forum: Properties of Light
Topic: Intensity
Replies: 3
Views: 236

### Intensity

What is meant by the intensity of a wave or the intensity of the light?
Sun Oct 15, 2017 5:50 pm
Forum: Photoelectric Effect
Topic: Wavelike properties [ENDORSED]
Replies: 4
Views: 304

### Wavelike properties[ENDORSED]

How can we tell if something has wavelike properties?