Search found 76 matches
- Mon Mar 02, 2020 8:51 am
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Kelvin or Celsius?
- Replies: 86
- Views: 5239
Re: Kelvin or Celsius?
You should use Kelvin because R uses Kelvin.
- Mon Mar 02, 2020 8:49 am
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: k
- Replies: 10
- Views: 576
Re: k
k has no units because it is a ratio
- Mon Mar 02, 2020 8:47 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: free energy and work
- Replies: 5
- Views: 380
Re: free energy and work
when energy is released, that energy can be used to do work. So if the reaction has a -delta G you know that energy is being released.
- Mon Mar 02, 2020 8:46 am
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: Determining n
- Replies: 5
- Views: 444
Re: Determining n
n is the moles being transferred.
- Mon Mar 02, 2020 8:46 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: the cell diagram for 6M.5a
- Replies: 2
- Views: 187
Re: the cell diagram for 6M.5a
Dr. Lavelle sent an updated link for the solution manual errors. I would check that out to see if that's one of them
- Tue Feb 04, 2020 2:46 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Thermochemistry vs Thermodynamics
- Replies: 2
- Views: 203
Re: Thermochemistry vs Thermodynamics
Thermochemistry is a branch of thermodynamics.
- Tue Feb 04, 2020 2:45 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Energy of a system
- Replies: 5
- Views: 338
Re: Energy of a system
When delta H is negative, the rxn is exothermic and releases heat. When delta H is positive the rxn is endothermic and absorbs heat.
- Tue Feb 04, 2020 2:43 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: C = K?
- Replies: 5
- Views: 358
Re: C = K?
We talked about it in discussion and it just means that it is scaled the same. If you were to add one degree to each that wouldn't change the ratio.
- Tue Feb 04, 2020 2:42 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: closed vs isolated
- Replies: 14
- Views: 449
Re: closed vs isolated
Closed can not interact with the environment at all. Isolated can interact slightly.
- Tue Feb 04, 2020 2:41 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Midterm
- Replies: 6
- Views: 311
Re: Midterm
A lot of equations are derived from one central equation and that is typically shown on the equation sheet. As long as you are able to derive the specific equations to set it equal to the variable you are looking for than you should be fine.
- Tue Feb 04, 2020 2:40 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Topics on the Midterm
- Replies: 22
- Views: 1057
Re: Topics on the Midterm
Everything in outlines 1-4 are covered.
- Tue Feb 04, 2020 2:39 pm
- Forum: Phase Changes & Related Calculations
- Topic: internal energy
- Replies: 11
- Views: 566
Re: internal energy
Internal energy is found using the delta U equation which will contain q.
- Tue Feb 04, 2020 2:39 pm
- Forum: Calculating Work of Expansion
- Topic: Calculus on The Midterm
- Replies: 8
- Views: 434
Re: Calculus on The Midterm
We aren't required to have previous knowledge of calculus so I don't think it will be on the exam.
- Tue Feb 04, 2020 2:38 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Equation
- Replies: 2
- Views: 148
Re: Equation
I think that has to do with the derivation of other equations and its more conceptual. I don't think it will be used to solve problems.
- Sun Jan 19, 2020 3:36 pm
- Forum: General Science Questions
- Topic: glow sticks
- Replies: 1
- Views: 218
Re: glow sticks
The reaction between the two chemicals in the glow stick tube is catalyzed by a base, usually sodium salicylate. The sticks consist of a tiny inner container that can be easily broken and that sits within a flexible outer container. Each container holds a different solution and when the glow stick i...
- Sun Jan 19, 2020 3:32 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Test 1 Acids and Bases Topic
- Replies: 9
- Views: 510
Re: Test 1 Acids and Bases Topic
There was a list of acids and bases that Lavelle made for 14A that were the ones he suggested memorizing but I can't seem to find the list.
- Sun Jan 19, 2020 3:29 pm
- Forum: *Titrations & Titration Calculations
- Topic: Acid/Base bonds
- Replies: 5
- Views: 861
Re: Acid/Base bonds
Longer bond length means that it is a weaker bond which results in it being a stronger acid.
- Sun Jan 19, 2020 3:27 pm
- Forum: Student Social/Study Group
- Topic: Chemistry Community
- Replies: 8
- Views: 1314
Re: Chemistry Community
You are given credit for all posts at the end of the quarter.
- Sun Jan 19, 2020 3:25 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Exothermic and Endothermic Reactions
- Replies: 5
- Views: 296
Re: Exothermic and Endothermic Reactions
Every reaction is either exothermic or endothermic. You are correct about the relationship to delta H
- Sun Jan 19, 2020 3:23 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: lewis structure
- Replies: 11
- Views: 416
Re: lewis structure
He said that it won't be required to draw them but it is a helpful way to visualize the reaction.
- Sun Jan 12, 2020 7:00 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Reaction Quotient Units
- Replies: 10
- Views: 283
Re: Reaction Quotient Units
You can determine the units by what will cancel out and if not than it can be unitless.
- Sun Jan 12, 2020 6:58 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: pressure and volume
- Replies: 4
- Views: 130
Re: pressure and volume
Boyle's Law states that pressure and volume have an inverse relationship when temperature is help constant. That is why double the original pressure would result in half of the original volume.
- Sun Jan 12, 2020 6:56 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: What is this?
- Replies: 23
- Views: 1411
Re: What is this?
It is also called "The Equilibrium Law" because it states that when any system is at equilibrium for a long period of time it is subjected to change in concentration, temperature, volume, or pressure. The system changes to a new equilibrium and this change partly counteracts the applied ch...
- Sun Jan 12, 2020 6:53 pm
- Forum: Ideal Gases
- Topic: P=(n/v)RT
- Replies: 12
- Views: 955
Re: P=(n/v)RT
n/V is how concentration is calculated and the derived equation includes concentration. I believe it is written that way to show that it means concentration.
- Sun Jan 12, 2020 6:52 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Reaction Quotient Q
- Replies: 6
- Views: 147
Re: Reaction Quotient Q
You are usually told which variable you are looking for but I believe Q is found when the reaction is not at equilibrium and K is found when the reaction is at equilibrium.
- Sat Dec 07, 2019 9:20 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Ka. Kb, Kw
- Replies: 4
- Views: 1343
Re: Ka. Kb, Kw
Ka refers to the pH formula and Kb refers to the pOH formula. Kw is a constant.
- Sat Dec 07, 2019 9:19 pm
- Forum: Lewis Acids & Bases
- Topic: Water
- Replies: 63
- Views: 2710
Re: Water
Water can act as either an acid or a base
- Sat Dec 07, 2019 9:18 pm
- Forum: Lewis Acids & Bases
- Topic: neutralization
- Replies: 6
- Views: 553
Re: neutralization
As long as an acid and base react to form salt and water it is considered neutralization
- Sat Dec 07, 2019 9:18 pm
- Forum: Hybridization
- Topic: Lone pairs in hybridization
- Replies: 4
- Views: 373
Re: Lone pairs in hybridization
Yes. A lone pair is a region of electron density along with a bond
- Sat Dec 07, 2019 9:17 pm
- Forum: Calculating the pH of Salt Solutions
- Topic: pH formula?
- Replies: 69
- Views: 3615
Re: pH formula?
-log[H+] and I think we just need to know that pH+pOH= 14
- Thu Dec 05, 2019 8:17 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Naming acids
- Replies: 2
- Views: 246
Re: Naming acids
Dr. Lavelle posted a chart to help but I don’t think we need to know how to name them
- Thu Dec 05, 2019 8:17 pm
- Forum: Limiting Reactant Calculations
- Topic: missed question test 1
- Replies: 4
- Views: 822
Re: missed question test 1
convert the g/mol mass to moles and multiply that by the molar ratio and then multiply by the g/mol mass of Si to get grams of Si
- Thu Dec 05, 2019 8:13 pm
- Forum: Amphoteric Compounds
- Topic: H2O
- Replies: 8
- Views: 438
Re: H2O
yes. Water can act as an acid or a base
- Thu Dec 05, 2019 8:13 pm
- Forum: Bronsted Acids & Bases
- Topic: Strong Bases
- Replies: 3
- Views: 272
Re: Strong Bases
on page F75 in the textbook there is a little chart that gives you the common strong acids and bases that are the ones we should memorize.
- Thu Dec 05, 2019 8:10 pm
- Forum: Ionic & Covalent Bonds
- Topic: Hydrogen bonding
- Replies: 2
- Views: 193
Re: Hydrogen bonding
Yes. F, O, and N are the only ones that hydrogen bond.
- Fri Nov 29, 2019 11:57 am
- Forum: Lewis Acids & Bases
- Topic: Bonds and pH
- Replies: 4
- Views: 272
Re: Bonds and pH
the longer and weaker a bond is, the more likely it is to be soluble in water and dissociate. it is the opposite for short and strong bonds
- Fri Nov 29, 2019 11:55 am
- Forum: Bronsted Acids & Bases
- Topic: Difference between bronsted and lewis acid/base?
- Replies: 6
- Views: 347
Re: Difference between bronsted and lewis acid/base?
My TA showed us in a table like this:
Acid Base
Bronsted : proton donor proton acceptor
Lewis : electron acceptor electron donor
Acid Base
Bronsted : proton donor proton acceptor
Lewis : electron acceptor electron donor
- Fri Nov 29, 2019 11:51 am
- Forum: Bronsted Acids & Bases
- Topic: Bronsted Acid and base
- Replies: 8
- Views: 501
Re: Bronsted Acid and base
Bronsted Acid = proton donor
Bronsted Base = proton acceptor
Bronsted Base = proton acceptor
- Fri Nov 29, 2019 11:49 am
- Forum: Bronsted Acids & Bases
- Topic: Naming Acids and Bases
- Replies: 3
- Views: 217
Re: Naming Acids and Bases
I think Lavelle emailed us a chart that is supposed to help.
- Fri Nov 29, 2019 11:46 am
- Forum: Student Social/Study Group
- Topic: Preparing for the final
- Replies: 25
- Views: 1195
Re: Preparing for the final
I felt the same as you did. I did all the homework problems and still felt unprepared for the midterm. I think going to TA and peer learning workshops where extra problems are provided is another good way. Review sessions and khan academy videos can be helpful too.
- Sun Nov 17, 2019 5:57 pm
- Forum: Student Social/Study Group
- Topic: test 2
- Replies: 8
- Views: 379
Re: test 2
Homework and chemistry community responses are worth 50 points each and each test is also worth 50 points each.
- Sun Nov 17, 2019 5:56 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: two central atoms
- Replies: 3
- Views: 219
Re: two central atoms
We didn't go over this scenario in lecture so I would assume it's not something we need to know for this week. However, you could determine that the bond angle would be 180 between the central atoms and the structure around each central atom would depend on the atoms around it.
- Sun Nov 17, 2019 5:54 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: single, double, and triple bonds
- Replies: 6
- Views: 441
Re: single, double, and triple bonds
In regards to VSEPR I think that multiple bonds have higher electron density than a single bond, because the electrons take up more space.
- Sun Nov 17, 2019 5:51 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Test 2
- Replies: 19
- Views: 831
Re: Test 2
By drawing the most stable lewis structure, you will be able to determine the correct shape.
- Sun Nov 17, 2019 5:50 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: repulsion strength
- Replies: 5
- Views: 280
Re: repulsion strength
The strength of the bonds determine the repulsion and the shape of the molecule. LP-LP has the strongest repulsion.
- Sun Nov 17, 2019 5:49 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Grading
- Replies: 7
- Views: 432
Re: Grading
I think all life science chemistry classes are curved so that the average is a B. So if the class average was a 70 than a 70 would become a B and everything else would shift as well.
- Sun Nov 17, 2019 5:47 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: VSEPR repulsion model
- Replies: 8
- Views: 570
Re: VSEPR repulsion model
Repulsion helps to determine shape and bond angle. The stronger bonds must be further apart.
- Sat Nov 16, 2019 9:29 pm
- Forum: General Science Questions
- Topic: Midterm
- Replies: 7
- Views: 516
Re: Midterm
Talking to your TA or go to office hours
- Sat Nov 16, 2019 9:27 pm
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: Hydrogen Bonding
- Replies: 5
- Views: 133
Re: Hydrogen Bonding
Yes it is a special kind of dipole dipole interaction
- Sat Nov 16, 2019 9:26 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Acids and Bases
- Replies: 4
- Views: 204
Re: Acids and Bases
This isn't anything in the homework problems so I think its not necessary to know.
- Sat Nov 16, 2019 9:24 pm
- Forum: General Science Questions
- Topic: Test 2
- Replies: 5
- Views: 266
Re: Test 2
Anything covered before the midterm that we weren't tested on and anything covered up until Friday.
- Sat Nov 16, 2019 9:20 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bond Angles
- Replies: 8
- Views: 307
Re: Bond Angles
I think memorizing them would be a good idea but he didn't specifically say we needed to memorize it.
- Sat Nov 16, 2019 9:19 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: What is VSPER
- Replies: 14
- Views: 954
Re: What is VSPER
VSEPR stands for Valence shell electron pair repulsion but he said we didn't need to memorize it.
- Sat Nov 16, 2019 9:18 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Test #2
- Replies: 4
- Views: 310
Re: Test #2
Any points not on the midterm from Chemical Bonds section and material covered last week.
- Sat Nov 16, 2019 9:15 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Melting Points
- Replies: 7
- Views: 450
Re: Melting Points
Memorizing the specific melting points isn't necessary but you can assume the boiling point from the interaction.
- Sat Nov 02, 2019 1:53 pm
- Forum: Dipole Moments
- Topic: Induced Dipole
- Replies: 5
- Views: 230
Re: Induced Dipole
A dipole-induced dipole attraction is a weak attraction that happens when a polar molecule induces a dipole in an atom or in a nonpolar molecule by disturbing the arrangement of electrons in the nonpolar species.
- Sat Nov 02, 2019 1:53 pm
- Forum: Photoelectric Effect
- Topic: Work Function
- Replies: 6
- Views: 352
Re: Work Function
The work function is the required about of energy to remove an electron. It refers to the photoelectric effect.
- Sat Nov 02, 2019 1:52 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Midterm
- Replies: 6
- Views: 283
Re: Midterm
My TA didn't mention anything about it in section so I don’t think we would be tested over it unless he mentions it in class Monday before the midterm.
- Sat Nov 02, 2019 1:50 pm
- Forum: Ionic & Covalent Bonds
- Topic: Midterm
- Replies: 28
- Views: 1233
Re: Midterm
fundamentals, quantum, and chemical bonds up to 2D
- Sat Nov 02, 2019 1:48 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Energy change and Energy of photon
- Replies: 5
- Views: 326
Re: Energy change and Energy of photon
You cant have negative energy of a photon so just because the energy change is negative it doesn't mean you have negative energy.
- Mon Oct 14, 2019 11:23 pm
- Forum: Properties of Light
- Topic: Wave Frequency
- Replies: 9
- Views: 470
Re: Wave Frequency
I think it is the amount of energy in each individual photon because of the wave model.
- Mon Oct 14, 2019 11:20 pm
- Forum: Balancing Chemical Reactions
- Topic: Writing Out Reactions
- Replies: 6
- Views: 353
Re: Writing Out Reactions
Yes eventually we will need to be able to write a chemical equation from the name of the equation.
- Mon Oct 14, 2019 11:19 pm
- Forum: DeBroglie Equation
- Topic: De Broglie's Equation
- Replies: 13
- Views: 485
Re: De Broglie's Equation
Any problem referring to wavelength, velocity, and mass.
- Mon Oct 14, 2019 11:17 pm
- Forum: DeBroglie Equation
- Topic: de Broglie vs Heisenberg
- Replies: 2
- Views: 173
Re: de Broglie vs Heisenberg
De Broglie refers to wavelength, velocity and mass whereas Heisenberg refers to position and nuclear diameter.
- Mon Oct 14, 2019 11:13 pm
- Forum: Properties of Light
- Topic: Angstrom
- Replies: 10
- Views: 492
Re: Angstrom
Most exam questions will tell you specifically what units to convert your answer to.
- Fri Oct 11, 2019 11:33 am
- Forum: Balancing Chemical Reactions
- Topic: Balancing Chemical Reactions
- Replies: 20
- Views: 1085
Re: Balancing Chemical Reactions
I find that writing the amount of each reactant and each product helps me visualize what I need to add to make the equation balanced.
- Fri Oct 11, 2019 11:32 am
- Forum: Empirical & Molecular Formulas
- Topic: Mass Percentage Question
- Replies: 9
- Views: 853
Re: Mass Percentage Question
To determine mass percentage composition you find the molar mass of the compound then find the molar mass of each element in the compound and divide each elements mass by the total mass and multiply by 100 to find the percentage.
- Fri Oct 11, 2019 11:29 am
- Forum: Limiting Reactant Calculations
- Topic: Showing Work for Limiting Reactant Calculations on Tests [ENDORSED]
- Replies: 68
- Views: 6657
Re: Showing Work for Limiting Reactant Calculations on Tests [ENDORSED]
You definitely receive credit for coming to the correct answer but in order to get the most partial credit possible you should write it out step by step.
- Fri Oct 11, 2019 11:27 am
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Wavelength Plausibility
- Replies: 31
- Views: 2601
Re: Wavelength Plausibility
Anything smaller than 10^-15 is not detectable.
- Fri Oct 11, 2019 11:25 am
- Forum: Ideal Gases
- Topic: Reading the textbook
- Replies: 262
- Views: 147480
Re: Reading the textbook
I would recommend reading the textbook to facilitate what is taught in lecture. If you don't feel confident about a certain topic reading the chapter and reading along with the examples in the chapter is really helpful.
- Tue Oct 08, 2019 3:49 pm
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Test 1 [ENDORSED]
- Replies: 107
- Views: 17654
Re: Test 1 [ENDORSED]
It is a written exam so all questions will be answered in the test booklet you are provided in discussion.
- Sun Oct 06, 2019 11:07 pm
- Forum: Balancing Chemical Reactions
- Topic: Fractions
- Replies: 34
- Views: 1367
Re: Fractions
I would assume changing the fraction to an integer is the only way you would get full credit. The purpose of making a fraction is so that it's easy to convert all of the elements coefficients to whole numbers.
- Sun Oct 06, 2019 11:05 pm
- Forum: Empirical & Molecular Formulas
- Topic: Writing Empirical Formulas
- Replies: 8
- Views: 858
Re: Writing Empirical Formulas
I think for the material we are learning in 14A, the order is not important. I think the ratio's are the important part.
- Sun Oct 06, 2019 11:03 pm
- Forum: Balancing Chemical Reactions
- Topic: Balancing Reactions
- Replies: 25
- Views: 2041
Re: Balancing Reactions
The law of conservation of mass states that mass cannot be created are destroyed and the reactants and products must have the same mass.
- Sun Oct 06, 2019 11:01 pm
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Theoretical vs. Actual Yield
- Replies: 38
- Views: 13916
Re: Theoretical vs. Actual Yield
The theoretical yield is the amount produced when a reaction is completed with 100% efficiency. The actual yield is the amount that is actually produced by the reaction.
- Sun Oct 06, 2019 10:56 pm
- Forum: Limiting Reactant Calculations
- Topic: Showing Work for Limiting Reactant Calculations on Tests [ENDORSED]
- Replies: 68
- Views: 6657
Re: Showing Work for Limiting Reactant Calculations on Tests [ENDORSED]
I would recommend showing all of your work regardless of the method you use. For free response tests its always better to show more work for partial credit purposes. I feel like showing that you know the process will be more important and get you more credit than getting the answer correct.