## Search found 60 matches

Mon Mar 11, 2019 2:30 pm
Forum: General Rate Laws
Topic: Rate Laws
Replies: 8
Views: 302

### Re: Rate Laws

I have asked some of the TA's and UA's this question and they said he has begun to stray away from asking for a straight up derivation but I would not totally cancel it out as a possible conceptual problem for the final. Honestly its not too hard to memorize the steps as there is a pattern you can f...
Mon Mar 11, 2019 2:27 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Arrhenius Equation-Review
Replies: 1
Views: 117

### Re: Arrhenius Equation-Review

I believe you would use this equation to solve for the K rate coefficient. This will be used to see the effects of temperature dependence for reaction rates.
Mon Mar 11, 2019 2:25 pm
Forum: Zero Order Reactions
Topic: Graphs
Replies: 8
Views: 668

### Re: Graphs

All the graphs will be linear however, the K sign for the slope will be different. Zero and first order graphs will have a negative slope while a second order graph will have a positive K slope.
Mon Mar 04, 2019 12:18 pm
Forum: Balancing Redox Reactions
Topic: Acidic vs basic solutions
Replies: 10
Views: 421

### Re: Acidic vs basic solutions

A acidic solution had a greater abundance of hydrogen ions making the solution acidic while a basic solution will have a greater abundance of hydroxyl (OH-).
Mon Mar 04, 2019 12:17 pm
Forum: Balancing Redox Reactions
Replies: 13
Views: 563

### Re: Adding H+ and H2O

for a acidic solution you should begin by balancing the non hydrogen and oxygen elements. Once you have done this you should balance the oxygen by adding H2O to the side that is lacking oxygen. Then you would add H+ to the other side to balance the number of hydrogen molecules.
Mon Mar 04, 2019 12:15 pm
Forum: Balancing Redox Reactions
Topic: Cell diagrams
Replies: 8
Views: 296

### Re: Cell diagrams

If there are no solid metals in the reaction then you would ad Pt (solid) as the reaction needs a solid metal to work therefore Pt (solid) or C(Gr) are often used to replace these needed elements.
Wed Feb 27, 2019 7:09 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Value of n
Replies: 7
Views: 396

### Re: Value of n

Once the redox reaction is balanced you should have an equal number of electrons on both sides of the equation. That will be the n value. There can only be one value for n. If you think you have two then you did not balance your redox equations correctly.
Wed Feb 27, 2019 7:08 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: platinum [ENDORSED]
Replies: 6
Views: 306

### Re: platinum[ENDORSED]

On the side with no solid metal on it. The platinum will be used to replace the missing solid metal needed for the reaction to proceed.
Wed Feb 27, 2019 7:07 pm
Forum: Balancing Redox Reactions
Topic: Balancing Redox Reactions
Replies: 3
Views: 154

### Re: Balancing Redox Reactions

After the excess H2O molecules are canceled out the H20 molecules must stay on the same side the excess was originally on. It can not be moved to the other side of the reaction.
Fri Feb 22, 2019 8:21 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Spontaneity
Replies: 6
Views: 265

### Re: Spontaneity

Gabs free energy is the same thing as the amount of work a system can do. Therefore when gabs free energy us negative it is spontaneous as the system is doing work.
Fri Feb 22, 2019 8:20 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Reversible Reactions
Replies: 8
Views: 597

### Re: Reversible Reactions

Not all isothermal reactions are reversible but if a reaction is said to be reversible it is usually isothermal. because there is no temperature change delta U is equal to zero according to the equation U= 3/2nRdeltaT.
Fri Feb 22, 2019 8:18 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: q=0
Replies: 4
Views: 229

### Re: q=0

yes you can assume that q is equal to zero. In this type of reaction, say a piston, the piston moves so quickly it does not allow an exchange of heat with the surroundings therefore there is no heat for an adiabatic system.
Sat Feb 16, 2019 10:34 pm
Forum: Calculating Work of Expansion
Topic: Reversible expansion
Replies: 4
Views: 251

### Re: Reversible expansion

reversible expansion will allow you to use the isothermal equation w= nrtln(delta V) while reversible isothermal can only use W=-pdeltaV.
Sat Feb 16, 2019 10:33 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Isobaric
Replies: 11
Views: 724

### Re: Isobaric

for a isobaric equation to find work you will want to use W= -p delta V.
Sat Feb 16, 2019 10:32 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: ΔU = 0?
Replies: 4
Views: 314

### Re: ΔU = 0?

Usually for isothermal delta U is zero. This is because if the equation from the first law of thermodynamics. 3/2nRT, when T equal zero delta U will be zero.
Thu Feb 07, 2019 11:20 pm
Forum: Phase Changes & Related Calculations
Topic: Units of enthalpy
Replies: 5
Views: 232

### Re: Units of enthalpy

Enthalpy is kJ/ mol
Thu Feb 07, 2019 11:19 pm
Forum: Phase Changes & Related Calculations
Topic: Heat Curve
Replies: 6
Views: 219

### Re: Heat Curve

I believe you should memorize it as it will help with bomb Calorimeter problems and other problems with various phase changes. Even if the curve is given I believe it would be helpful to memorize it anyways. It will save you time on the exam.
Thu Feb 07, 2019 11:18 pm
Forum: Phase Changes & Related Calculations
Topic: Negative work
Replies: 11
Views: 408

### Re: Negative work

Yes you can have negative work on a system. An example of this would be the system doing work on its surroundings. Increasing the volume does count as negative work by the system.
Thu Jan 31, 2019 10:59 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Open, closed, or isolated systems
Replies: 10
Views: 6452

### Re: Open, closed, or isolated systems

An open system, like a cup of water, can exchange matter and energy with the environment. A closed system, like a closed water bottle, can only exchange energy. A isolated system like a sealed thermos can exchange neither.
Thu Jan 31, 2019 10:56 pm
Forum: Phase Changes & Related Calculations
Topic: Steam vs Boiling Water
Replies: 10
Views: 1804

### Re: Steam vs Boiling Water

It takes more energy; in the form of heat; to go from water to steam than it does to go from water to boiling water. Since it takes more energy to go through that phase change you would get a worse burn.
Thu Jan 31, 2019 10:55 pm
Forum: Phase Changes & Related Calculations
Topic: J vs. kJ
Replies: 9
Views: 345

### Re: J vs. kJ

It depends on what the problem specifies. If it does not ask I usually keep the answer in the units the problem gave the values as.
Thu Jan 24, 2019 1:41 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5% Rule
Replies: 5
Views: 254

### Re: 5% Rule

you can use the 5% rule for a K value that is less than 10^-3 for acids and bases or equilibrium concentrations and pressures.
Thu Jan 24, 2019 1:39 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: converting between kp and kc
Replies: 4
Views: 202

### Re: converting between kp and kc

you will want to use the formula PV=nRT. if you just move the V to the other side you get P=nRT/v. But n/v is just concentration. So you replace n/v with your concentration for kc then you plug in your T and R constant to get P.
Thu Jan 24, 2019 1:38 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Units
Replies: 2
Views: 147

### Units

What is the unit for pressure concentration used in Chem? Is it still molarity?
Thu Jan 17, 2019 1:25 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Inert Gases
Replies: 5
Views: 216

### Re: Inert Gases

Inert gases will not react with a reaction therefore it is not considered when calculating the equilibrium constant equation as nothing is changing for that gas and it is also not changing anything.
Thu Jan 17, 2019 1:23 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Changes to K value
Replies: 9
Views: 268

### Re: Changes to K value

Temperature is the only modification that can affect the K value. Pressure, volume, and concentration does not affect the K value but it does affect which side of the reaction is favored more.
Thu Jan 17, 2019 1:22 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Q vs K [ENDORSED]
Replies: 4
Views: 194

### Re: Q vs K[ENDORSED]

The Q is the same thing as the K value however it is the constant when the reaction is not in equilibrium. So you often compare K and Q to see which side of the reaction is favored when it is not in equilibrium.
Fri Jan 11, 2019 7:42 pm
Forum: Ideal Gases
Topic: Pressure of gasses
Replies: 5
Views: 292

### Re: Pressure of gasses

I don't think we will be using it. He hasn't mentioned it in lecture yet.
Fri Jan 11, 2019 7:36 pm
Forum: Ideal Gases
Topic: Pv=nRT [ENDORSED]
Replies: 12
Views: 353

### Re: Pv=nRT[ENDORSED]

yes it is in Kelvin. If you need to convert to K from C add 273.
Fri Jan 11, 2019 7:34 pm
Forum: Ideal Gases
Topic: Q and K [ENDORSED]
Replies: 35
Views: 1737

### Re: Q and K[ENDORSED]

There is no difference.
Wed Dec 05, 2018 12:27 pm
Forum: Significant Figures
Topic: Sig Figs in the Middle of a Problem
Replies: 9
Views: 930

### Re: Sig Figs in the Middle of a Problem

I would suggest waiting until the very end to round to the nearest sig fig. That way you still get the most accurate answer.
Wed Dec 05, 2018 12:26 pm
Forum: Empirical & Molecular Formulas
Topic: Determining Empirical formula
Replies: 4
Views: 460

### Re: Determining Empirical formula

You should first convert all your elements into moles. you then divide by the smallest mole value to get your empirical equation values. Last multiply if needed to get whole numbers.
Wed Dec 05, 2018 12:21 pm
Forum: Naming
Topic: Oxidation number
Replies: 2
Views: 171

### Re: Oxidation number

Cl will always have a negative 1- charge. So say you have something that says Cl2 then the overall charge will be 2-. In the case of [Fe Cl(OH2)5]^+ you will find the oxidation number of Fe. So Oh2 is a neutral ligand therefore there is no charge from this molecule. Since Cl is the only component th...
Sat Dec 01, 2018 12:38 am
Forum: Ionic & Covalent Bonds
Topic: Intra vs Intermolecular forces
Replies: 9
Views: 4355

### Re: Intra vs Intermolecular forces

Intermolecular forces are weaker than intramolecular forces. Therefore it would be easier to break the bond between atoms that make up a molecule than to separate molecules. Intramolecular forces also consist of weak forces such as London dispersion and Van der Waals.
Sat Dec 01, 2018 12:34 am
Forum: Hybridization
Topic: Delocalized Pi Bonding
Replies: 3
Views: 129

### Re: Delocalized Pi Bonding

A delocalized pi bond is when electrons can freely move more that two nuclei. You will often see this in a lewis structure in carbon rings. Carbon rings often consist of double bonds. These pi bonds that are spread out over the lewis structure means the pi bonds are delocalized as they do not reside...
Sat Dec 01, 2018 12:30 am
Forum: Administrative Questions and Class Announcements
Topic: Saying Thank You to Dr. Lavelle
Replies: 291
Views: 136057

### Re: Saying Thank You to Dr. Lavelle

Thank you so much Dr. Lavelle for all the you do. Your lectures and all your resources have helped me do well and keep up with the class.
Sat Nov 24, 2018 1:14 am
Forum: Ionic & Covalent Bonds
Topic: Bond Lengths
Replies: 10
Views: 579

### Re: Bond Lengths

There is resonance therefore, you take the average of the two.
Sat Nov 24, 2018 1:11 am
Forum: Administrative Questions and Class Announcements
Topic: How to find my posts
Replies: 76
Views: 49028

### Re: How to find my posts

If you click on your account it should show you your post. Also if you had replied to someone there is a section that shows you how many times you have posted. If you click that it will should you all of your posts.
Sat Nov 24, 2018 1:09 am
Forum: Administrative Questions and Class Announcements
Topic: Saying Thank You to Dr. Lavelle
Replies: 291
Views: 136057

### Re: Saying Thank You to Dr. Lavelle

Thank you Dr. Lavelle for always keeping the class engaging. I also enjoy the fact that you have been using models in class to explain the molecular structure! Looking forward to your 14b lectures next quarter!
Thu Nov 15, 2018 8:01 pm
Forum: Electronegativity
Topic: Electronegativity
Replies: 8
Views: 440

### Re: Electronegativity

Electronegativity will increase upward and to the right of the periodic table. Some exceptions include noble gases, lanthanides, and actinides.
Thu Nov 15, 2018 8:00 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge
Replies: 10
Views: 803

### Re: Formal Charge

The formal charge is the best way to ensure your lewis structure is in the most stable state and to find its molecular shape via VSPER. Some ions may throw people off so formal charges are the best way to check your work.
Thu Nov 15, 2018 7:58 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Memorizing the VSPER Models
Replies: 4
Views: 228

### Memorizing the VSPER Models

I am currently trying to memorize all the VSPER models from the chart from the text book. What would be the best way to memorize all the information about the angles and what shapes belong with what?
Thu Nov 08, 2018 2:52 pm
Forum: Resonance Structures
Replies: 11
Views: 790

A radical has lone pairs. Usually a single electron for example the element NH4+.
Thu Nov 08, 2018 2:50 pm
Forum: Lewis Structures
Topic: Double Bonds
Replies: 7
Views: 290

### Re: Double Bonds

I usually check to see if a double bond is needed through the formal charges or through the pairs. If there is an odd number and there is a single lone electron I usually find a way to make it a double bond. Formal charges are the best way to check if another bond is needed.
Thu Nov 08, 2018 2:48 pm
Forum: Lewis Structures
Topic: Formal charge question
Replies: 9
Views: 376

### Re: Formal charge question

Once I see every element has its respective electrons and all the needed bond have been inserted I use the formal charge to solidify the lewis structure is in its most stable form. Its a great way to check your work.
Tue Oct 30, 2018 10:55 pm
Forum: Trends in The Periodic Table
Topic: Electron affinity
Replies: 3
Views: 234

### Re: Electron affinity

Electron affinity represents the energy spent or released when an electron is added to a gaseous molecule to create an ion. An example of this is the electron affinity of chlorine (-349 kJ mol-1) the negative sign represents a release in energy. Electronegativity is the tendency of atoms to attract ...
Tue Oct 30, 2018 10:48 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: px,py,pz???
Replies: 6
Views: 775

### Re: px,py,pz???

x,y, and z represent the different sections of an orbital each pair of elections can fill. These are just ways to distinguish between the different positions within the orbital.
Tue Oct 30, 2018 10:46 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: How to do e- configuration shorthand?
Replies: 3
Views: 160

### Re: How to do e- configuration shorthand?

You would only need to put [Xe] for the shorthand way as it is the closest Nobel gas.
Tue Oct 23, 2018 12:36 pm
Forum: Einstein Equation
Topic: Joules per photon?
Replies: 5
Views: 324

### Re: Joules per photon?

You can just leave it in Joules.
Tue Oct 23, 2018 12:34 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Value of Delta X
Replies: 9
Views: 545

### Re: Value of Delta X

The delta x in the equation is usually in meters and is often what is solved for or given. If it is in pm you would need to convert it to m so you can solve the problem.
Tue Oct 23, 2018 12:32 pm
Forum: Properties of Light
Topic: Photoelectric Effect
Replies: 8
Views: 451

### Re: Photoelectric Effect

The photoelectric effect is the emission of electrons caused by the threshold of the metal and the energy of the photon.
Fri Oct 19, 2018 10:05 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Lyman vs Balmer
Replies: 6
Views: 356

### Re: Lyman vs Balmer

the Lyman series releases electrons to the n=1 level and is often associated with UV rays, while the Balmer series will release electrons to the n=2 energy level and is often associated with visible light.
Fri Oct 19, 2018 10:01 pm
Forum: Empirical & Molecular Formulas
Topic: Is it possible for the Empirical and Molecular formula to be the same? [ENDORSED]
Replies: 8
Views: 443

### Re: Is it possible for the Empirical and Molecular formula to be the same?[ENDORSED]

yes! if the molecular formula can not be simplified it is the same as the molecular formula.
Fri Oct 19, 2018 9:58 pm
Forum: Properties of Light
Topic: color of light
Replies: 11
Views: 459

### Re: color of light

I have looked at a few sites and many have stated though the frequency and wavelength are inversely proportional to speed of light the wave length is often the indicator of what the color is.
Wed Oct 10, 2018 9:13 pm
Forum: Empirical & Molecular Formulas
Topic: Empirical & Molecular Formulas
Replies: 11
Views: 967

### Empirical & Molecular Formulas

Can the empirical and molecular formula be the same?
Wed Oct 10, 2018 9:12 pm
Forum: SI Units, Unit Conversions
Topic: Scientific Notation
Replies: 7
Views: 377

### Re: Scientific Notation

There really isn't a difference but I would get use to writing in scientific notation as Dr. Lavelle said scientific notation is often used is in the lab. there is no specific time to convert it to scientific notation. I would just automatically make it into scientific notation just in case. It is a...
Wed Oct 10, 2018 9:09 pm
Forum: Einstein Equation
Topic: sig fig numbers
Replies: 4
Views: 143

### sig fig numbers

When you are doing an exam should the final answer be in the lowest number or the highest number of sig figs from the problem?
Wed Oct 03, 2018 11:04 pm
Forum: Balancing Chemical Reactions
Topic: notation
Replies: 4
Views: 282

### Re: notation

Yes he said it is important to do during an exam and it is also good practice once you begin working in labs and doing research.
Wed Oct 03, 2018 11:03 pm
Forum: Balancing Chemical Reactions
Topic: Balancing reactions tips
Replies: 29
Views: 1218

### Re: Balancing reactions tips

When I balance equations I like to write the number of elements on both sides so I can see everything visually.

B2O3+Mg ------> MgO+B

B:2 B:1
O:3 O:1
Mg:1 Mg:1

Then you can see where to balance everything out.
Wed Oct 03, 2018 10:55 pm
Forum: Significant Figures
Topic: Sig Figs?
Replies: 3
Views: 174

### Sig Figs?

How do sig figs work?