## Search found 64 matches

Sun Mar 17, 2019 4:48 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Wmax
Replies: 3
Views: 573

### Re: Wmax

Wmax is equal to delta G which is also equal to -nFEcell
Sun Mar 17, 2019 4:46 pm
Forum: Second Order Reactions
Topic: Non-integer orders
Replies: 7
Views: 372

### Re: Non-integer orders

Lavelle said that most orders will be in whole number calculations.
Sun Mar 17, 2019 4:45 pm
Forum: Second Order Reactions
Topic: Half Life
Replies: 7
Views: 833

### Re: Half Life

The half life equations are on the equation sheet
Sun Mar 10, 2019 11:54 pm
Forum: Zero Order Reactions
Topic: Graphs
Replies: 8
Views: 621

### Re: Graphs

All of the graphs for the ordered reactions should have linear plots. It just depends on what is on the axis that determines what is the order of the reaction.
Sun Mar 10, 2019 11:53 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Final Exam
Replies: 23
Views: 593

### Re: Final Exam

The final is cumulative, so everything we have discussed in class since the first day of the quarter is fair game for the final.
Sun Mar 10, 2019 11:51 pm
Forum: General Rate Laws
Topic: Slow step of reactions
Replies: 3
Views: 120

### Re: Slow step of reactions

The overall rate law of the reaction is dependent on the slowest reaction mechanism. So the overall rate law would be equal to the rate law of the slowest step regardless of the reaction rates of the other steps. Since the slowest step is the "bottleneck" for the whole reaction you only ne...
Mon Mar 04, 2019 3:51 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: 6th edition example 14.8
Replies: 1
Views: 81

### 6th edition example 14.8

In the example 14.8, the textbook gives the reactions AgCl(s)- --> Ag+(aq) + Cl-(aq) and they found the potential of the cell using the half reactions AgCl(s) + e- --> Ag(s) + Cl-(aq) E= +0.22 V and Ag+(aq) + e- --> Ag(s) E= +0.8 V. They reversed the last half reaction to be Ag(s) --> Ag+(aq) + e- a...
Sun Mar 03, 2019 4:20 pm
Forum: Balancing Redox Reactions
Topic: oxidation states
Replies: 4
Views: 177

### Re: oxidation states

To calculate the oxidation state of an element that is a transition metal. You first figure out the oxidation state of the element that it is compounded with. Based on that oxidation state and the overall charge of the compound, you can calculate the transition metal oxidation state. The sum of the ...
Sun Mar 03, 2019 4:18 pm
Forum: General Rate Laws
Topic: Initial Reaction Rates
Replies: 2
Views: 119

### Re: Initial Reaction Rates

It is easier to find the initial reaction rates so you don't have to take into account the rate of the reverse reaction.
Sun Mar 03, 2019 4:16 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Does anyone know if test 2 will be curved?
Replies: 15
Views: 560

### Re: Does anyone know if test 2 will be curved?

I don't think he'll curve it since the way the class is graded is out of a certain number of points :(
Mon Feb 25, 2019 9:07 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Nernst equation with K and Q
Replies: 2
Views: 138

### Nernst equation with K and Q

Can someone explain what the difference is between the E value that is found when you take the log of K and Q and how can we use that number to determine which way the reaction will proceed?
Mon Feb 25, 2019 9:05 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Salt bridge
Replies: 2
Views: 113

### Salt bridge

How do we determine which ions are moving across the salt bridge and in what direction they are moving?
Mon Feb 25, 2019 9:01 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6th Edition 14.13
Replies: 1
Views: 89

### 6th Edition 14.13

Write the half-reactions, the balanced equation for the cell reaction, and the cell diagram for each of the following skeletal equations: Cl2(g) + H2(g) --> HCl(aq) How are we suppose to determine which elements go on which sides of the line? I understand that inert solids are suppose to go on the o...
Mon Feb 18, 2019 3:04 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Change in free energy for a reaction at equilibrium
Replies: 3
Views: 96

### Re: Change in free energy for a reaction at equilibrium

At equilibrium deltaG is 0 when at constant temperature and pressure. The example they give in the textbook is that when the temperature is 0 C, solid water and liquid water are at an equilibrium (as seen in the heating curve because they are both present), so the deltaG is 0.
Mon Feb 18, 2019 3:02 pm
Forum: Van't Hoff Equation
Topic: Temperature Dependence of K
Replies: 5
Views: 250

### Re: Temperature Dependence of K

The Van't Hoff equation allows people to find the new equilibrium constant (K) when temperature changes, knowing the values of enthalpy and entropy.
Wed Feb 13, 2019 12:37 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: Finding W (degeneracy)
Replies: 4
Views: 365

### Finding W (degeneracy)

When calculating for W when there is 1 mol of a substance does this mean that you have to raise the number of microstates available to the power of Avogadro's number?
Mon Feb 11, 2019 11:36 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Cp and Cv
Replies: 3
Views: 100

### Re: Cp and Cv

You only really need to know these when solving for entropy. They're used for monatomic ideal gases for the equation deltaS = n*C*ln(T2/T1). The heat capacity changes depending on if pressure or volume is held constant.
Mon Feb 11, 2019 11:30 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Extensive vs Intensive
Replies: 7
Views: 419

### Re: Extensive vs Intensive

Can someone clarify why heat capacity is extensive but specific heat and molar heat capacity is intensive.
Mon Feb 11, 2019 11:28 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 9.13 6th edition
Replies: 1
Views: 121

### 9.13 6th edition

During the test of an internal combustion engine, 3.00 L of nitrogen gas at 18.5 \$C was compressed suddenly (and irreversibly) to 0.500 L by driving in a piston. In the process, the temperature of the gas increased to 28.1 \$C. Assume ideal behavior. What is the change in entropy of the gas? I know t...
Sun Feb 03, 2019 5:14 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Example 8.6 (6th edition)
Replies: 1
Views: 115

### Example 8.6 (6th edition)

In the 6th edition textbook, the example 8.6 asks to find the heat at constant volume after finding the final temperature at constant volume and pressure. In the example to find heat they use the equation delta U = nC(v,m)deltaT. I understand why the heat capacity at constant volume was used, but in...
Sun Feb 03, 2019 5:06 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: 1st law of thermodynamics
Replies: 7
Views: 249

### Re: 1st law of thermodynamics

The first law of thermodynamics is the conservation of energy, meaning that the internal energy of an isolated system is constant. This relates to the universe because the universe is an isolated system, and therefore the energy within it is constant.
Sun Feb 03, 2019 5:00 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: open system
Replies: 8
Views: 318

### Re: open system

Can someone explain why irreversible processes are held at constant pressure?
Sun Feb 03, 2019 4:54 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Friday 2/1 Lecture Notes
Replies: 2
Views: 123

### Re: Friday 2/1 Lecture Notes

In lecture, Lavelle was explaining that when the reaction goes to completion heat will be released and and delta H will be negative since the heat is leaving the system. He used this example to show how thermodynamics is time independent and only reliant of the initial and final states of a reaction.
Sun Jan 27, 2019 4:30 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy of formation
Replies: 1
Views: 71

### Enthalpy of formation

Can someone explain what the difference is between a standard enthalpy and the enthalpy of formation? And in which situations they should be used in.
Sun Jan 27, 2019 4:26 pm
Forum: Phase Changes & Related Calculations
Topic: Steam
Replies: 7
Views: 223

### Re: Steam

According to the heating curve for water, the graph indicates that steam occurs when water reaches a temperature of 100 degrees Celsius or higher. This means that it contains a greater amount of heat as compared to boiling water which maxes out at 100 degrees Celsius. The more heat energy something ...
Sun Jan 27, 2019 4:23 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 6th edition 8.11
Replies: 2
Views: 93

### Re: 6th edition 8.11

A reversible process is a reaction that can be reversed by an infinitely small change in either direction.
Sun Jan 20, 2019 5:12 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Le Chateliers Principle
Replies: 4
Views: 160

### Re: Le Chateliers Principle

N_{2} + 3H_{2} \rightleftharpoons 2NH_{3} What happens if we increase N_{2} ? Increase NH_{3} ? Decrease H_{2} ? This was explained during lecture, but I'm still a little confused. Can someone explain this to me again? Increasing reactants will push the chemical reaction in favor of the products, a...
Sun Jan 20, 2019 5:08 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Strength and Weakness
Replies: 2
Views: 110

### Re: Strength and Weakness

The strength of an acid is dependent on how likely it is to fully dissociate. Strong acids tend to fully deprotonate so their Ka value is higher. Weak acids do not dissociate as easily and their Ka values will be smaller in comparison.
Sun Jan 20, 2019 5:06 pm
Forum: Student Social/Study Group
Topic: test 1
Replies: 10
Views: 627

### Re: test 1

Test 1 will cover equilibrium and acid and bases equilibrium. So we will probably be asked to calculate pH and molar concentrations after equilibrium has been reached.
Sun Jan 13, 2019 4:51 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium Criteria
Replies: 4
Views: 168

### Re: Equilibrium Criteria

A reaction occurs equilibrium when both the forward reaction and the reverse reaction occur at the same rate, this can also be shown when Q=K.
Sun Jan 13, 2019 4:49 pm
Forum: Ideal Gases
Topic: gases
Replies: 3
Views: 81

### Re: gases

Kp is the equilibrium constant using partial pressure. Normally if all the compounds in a chemical reaction are in the gas phase then you don't need to change the partial pressure of a gas into concentration unless you are asked to find Kc. If a reaction has aqueous and gas compounds then you will h...
Sun Jan 13, 2019 4:46 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: solids in calculating equilibrium constant? [ENDORSED]
Replies: 8
Views: 355

### Re: solids in calculating equilibrium constant?[ENDORSED]

Pure solids and liquids are not included in calculating the equilibrium constant, but aqueous solutions and gases are included.
Sat Dec 08, 2018 7:56 pm
Forum: Ionic & Covalent Bonds
Topic: energy
Replies: 1
Views: 149

### Re: energy

Yes, dissociation energy is the energy required to break a certain bond. The energy required to break a bond will increased with the number of bonds between molecules and if the length of the bond is larger.
Sat Dec 08, 2018 7:53 pm
Forum: Octet Exceptions
Topic: formal charge
Replies: 2
Views: 313

### Re: formal charge

Yes, using formal charge will help to see which structure is the most stable. You want to make the most atoms end up with a formal charge of 0 in order for the molecule to be at its most stable state. This does not apply to molecules that have a charge, for those molecules, you want the formal charg...
Sat Dec 08, 2018 7:49 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Uncertainty Principal
Replies: 1
Views: 347

### Re: Uncertainty Principal

This applies to the DeBroglie equation where wavelength = planck's constant/momentum. Because of this equation as the wavelength increases the momentum decreases, thus the two are inversely proportional.
Thu Dec 06, 2018 5:13 pm
Forum: Amphoteric Compounds
Topic: Amphoteric Compounds
Replies: 1
Views: 135

### Amphoteric Compounds

For the question in the 6th edition textbook 12.17 how can you tell if a compound is amphoteric or not? Specifically looking at As2O3 and Bi2O3, how can you tell that these compounds are amphoteric?
Thu Nov 29, 2018 11:47 am
Forum: Dipole Moments
Topic: London Dispersion Forces vs Dipole Dipole
Replies: 3
Views: 444

### Re: London Dispersion Forces vs Dipole Dipole

Iodine also has a greater number of electrons and therefore has the potential to create a greater dipole movement. London dispersion forces are a weaker form of dipole interactions, and as the number of electrons participating increases, the interaction between molecules will be stronger.
Thu Nov 29, 2018 11:42 am
Forum: Biological Examples
Topic: CH 17 6TH EDITION HW 17.31d
Replies: 4
Views: 190

### Re: CH 17 6TH EDITION HW 17.31d

In the formula above, why is sodium not included inside the brackets?
Thu Nov 29, 2018 11:39 am
Forum: Lewis Acids & Bases
Topic: HF
Replies: 5
Views: 226

### Re: HF

HF is a weak acid because it does not completely dissociate in water. This is most likely due to the fact that the bond between HF is too strong for the molecule to fully dissociate.
Mon Nov 26, 2018 4:34 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Test 3
Replies: 38
Views: 1193

### Re: Test 3

I believe we will need to know the basic angles of the more common shapes, like a tetrahedral has angles of 109.5. I don't think he will make use memorize all bond angles when there are lone pairs involved. I just think that we need to know that a lone pair causes greater repulsion and the bond angl...
Mon Nov 26, 2018 4:32 am
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR
Replies: 9
Views: 319

### Re: VSEPR

Lone pair bonding has the greatest electrons repulsion. That is why we take into account the lone pairs, but we do not take into consideration the number of bonds when determining VSPER shape.
Mon Nov 26, 2018 4:30 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Multiple bonds and electron density
Replies: 3
Views: 84

### Re: Multiple bonds and electron density

The number of bonds connecting 2 atoms is disregarded because they have the same electron repulsion. However, we take into consideration when there are lone pairs because lone pairs give off greater electron repulsion in comparison to bonded electrons.
Sun Nov 18, 2018 7:07 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Lone Pair?
Replies: 4
Views: 286

### Re: Lone Pair?

A lone pair has greater repulsion than bonded electrons and will cause the bond angles between the other atoms to decrease due to this repulsion. There is not a way to know how much a lone pair will decrease a bond angle, but as long as we know that a lone pair results in a bond angle that is lower ...
Sun Nov 18, 2018 7:04 pm
Forum: Trends in The Periodic Table
Topic: Electronegativity vs. Electron Affinity?
Replies: 11
Views: 647

### Re: Electronegativity vs. Electron Affinity?

Electronegativity is how well an atom can attract electrons towards itself. Electron affinity is the amount of energy released when an electron is added to a neutral atom to form a negative ion.
Sun Nov 18, 2018 7:00 pm
Forum: Bond Lengths & Energies
Topic: VSEPR Model Question
Replies: 2
Views: 160

### Re: VSEPR Model Question

When predicting molecular shape we have to take into account the number of electron densities that the molecule has. Nitrogen is the central atom and it bonds to oxygen with a double bond and fluorine with a single bond. Since that only give nitrogen 6 shared electrons, nitrogen also has a lone pair...
Sun Nov 11, 2018 6:55 pm
Forum: Electronegativity
Topic: Electronegativity and Noble Gases
Replies: 3
Views: 75

### Re: Electronegativity and Noble Gases

Electronegativity refers to the ability for an atom to gain an electron. Since noble gases already have a filled valence shell they do not require any extra electrons and do not have electronegativity (their electronegativity is zero).
Sun Nov 11, 2018 6:48 pm
Forum: Lewis Structures
Topic: Double Bonds - Hallogens
Replies: 1
Views: 113

### Re: Double Bonds - Hallogens

Halogens don't form double bonds because they don't need to share any more electrons since their valence shell is filled from the one bond.
Sun Nov 11, 2018 6:40 pm
Forum: Ionic & Covalent Bonds
Topic: hydrogen bonds and melting points
Replies: 3
Views: 107

### Re: hydrogen bonds and melting points

Covalent bonds are intramolecular bonds (bonds within a molecule) whereas hydrogen bonds are intermolecular bonds (bonds between molecules). In H2O the bonds between the different H2O molecules are hydrogen bonded, but in H2S the H2S molecules are bonded with a dipole dipole interaction because hydr...
Sun Nov 04, 2018 11:09 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge Equation
Replies: 13
Views: 2801

### Re: Formal Charge Equation

I'm not entirely sure that there's a shortcut to the equation, but what we learned in lecture was that the formal charge = v - (l- b/2) where v is the number of valence electrons that the element has, l is the number of lone pair electrons that the atom has in the molecule, and b is the number of bo...
Sun Nov 04, 2018 11:05 pm
Forum: Lewis Structures
Topic: Resonance structures
Replies: 2
Views: 98

### Re: Resonance structures

I would show all the possible resonance structures because a resonance is the blend of all of them together, so the most accurate way to depict the bonds of the molecule would be to show all of the blended possibilities. The different resonances of a molecule doesn't vary too much, only the position...
Sun Nov 04, 2018 11:03 pm
Forum: Octet Exceptions
Topic: Incomplete Octet
Replies: 5
Views: 446

### Re: Incomplete Octet

BF4- undergoes a coordinate covalent bond which means that 2 electrons come from one atom which in this case would be the extra fluorine atom. The reason why in BF3 boron is stable with an incomplete octet is because fluorine has such a high ionization energy that it is unlikely to exist with a posi...
Sun Oct 28, 2018 1:02 pm
Forum: Lewis Structures
Topic: Dot's in the Lewis Structure
Replies: 10
Views: 390

### Re: Dot's in the Lewis Structure

Where you place the dots doesn’t matter, but I think you have to make sure each side of the element has a dot before pairing up electrons.
Tue Oct 23, 2018 1:05 am
Forum: Properties of Electrons
Topic: Nodal surfaces
Replies: 3
Views: 251

### Re: Nodal surfaces

I think we will need to know this because it relates to the s,p,d,f orbitals and how the electrons interact with each other.
Tue Oct 23, 2018 1:02 am
Forum: Properties of Light
Topic: Test 2 Equations
Replies: 14
Views: 501

### Re: Test 2 Equations

In my last discussion we went over equations that described the energy of a photon, de Broglie's equation, the uncertainty principle equation, photoelectric effect, and the rydberg equation. It would probably help to learn these equations for the test, but according to the link that someone posted a...
Sat Oct 20, 2018 1:05 pm
Forum: Trends in The Periodic Table
Replies: 4
Views: 141

If he didn't say to skip those readings in the syllabus I think we need to know those concepts. However, for the upcoming test (test 2) we only need to know the concepts up until orbitals and quantum numbers.
Sat Oct 20, 2018 1:02 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Orbitals
Replies: 4
Views: 261

### Re: Orbitals

He said we will not be asked to draw the orbitals ourselves, but I don't know if he'll ask us to name them from a picture that he provides.
Sat Oct 20, 2018 1:01 pm
Forum: Properties of Light
Topic: Do I have to memorize the spectrum?
Replies: 20
Views: 758

### Re: Do I have to memorize the spectrum?

I would know the general order of the atomic spectra, but I don't think we will be asked to know what the exact wavelength ranges are for each type of radiation.
Tue Oct 16, 2018 12:34 am
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8047
Views: 1413034

### Re: Post All Chemistry Jokes Here

Never trust atoms, they make up everything.
Tue Oct 16, 2018 12:31 am
Forum: Einstein Equation
Topic: Calculate Number of Photons
Replies: 3
Views: 117

### Re: Calculate Number of Photons

First you have to calculate the energy from the lamp, which is 32J/s *2s = 64J. Then you can calculate the energy corresponding to the wavelength (using E=hc/wavelength), which would give the the energy per photon of light. Once you have that, you can divide 64J by your answer which is in J/photon t...
Tue Oct 16, 2018 12:26 am
Forum: Ideal Gases
Replies: 147
Views: 104704

I generally like to read the textbook after lectures because once it is discussed in class the content in the textbook seems like a review and a way to dive into more specifics. I also find that it is less intimidating once you have a basic knowledge over the subject beforehand. I really find it hel...
Tue Oct 16, 2018 12:22 am
Forum: Administrative Questions and Class Announcements
Topic: Required knowledge for test/midterm [ENDORSED]
Replies: 13
Views: 592

### Re: Required knowledge for test/midterm[ENDORSED]

He will most likely give you constants and other basic equations in order to help you like on the first test, but if you struggled with the time limit on the first test memorizing certain basic equations might help to cut time when taking the next test.
Tue Oct 16, 2018 12:18 am
Forum: Student Social/Study Group
Topic: Note Taking
Replies: 32
Views: 2518

### Re: Note Taking

I find it best to take notes by hand because it is easier to draw diagrams and other visuals to help understand key concepts. Taking notes by hand also makes it easier to go back and add little comments if the professor adds any extra information. However, if your handwriting is bad I recommend taki...
Tue Oct 16, 2018 12:14 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Negative v. Positive when calculating energy
Replies: 8
Views: 282

### Re: Negative v. Positive when calculating energy

Since the electron is decreasing in energy levels, it is losing energy and therefore would have a negative value. However, as it decreases in energy level it releases a photon which has a positive value in order to offset the previous negative values since energy can neither be created nor destroyed.
Tue Oct 16, 2018 12:10 am
Forum: Einstein Equation
Topic: Question regarding wavelength
Replies: 5
Views: 199

### Re: Question regarding wavelength

In equations, wavelength is typically in the form of meters usually because of the other SI units given in other variables. For example, energy is given as Joules = kgm/s so the wavelength would be in meters.