Search found 109 matches
- Sat Mar 14, 2020 3:37 pm
- Forum: *Enzyme Kinetics
- Topic: Catalysts and enthalpy
- Replies: 6
- Views: 2416
Re: Catalysts and enthalpy
No, a catalyst doesn't affect the enthalpy of a reaction because enthalpy is a state function - it does not depend on the path taken from reactants to products. It just depends on the compositions of reactants and products. A catalyst provides a new pathway for the reaction with a lower activation e...
- Sat Mar 14, 2020 3:31 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Partial Credit
- Replies: 8
- Views: 528
Re: Partial Credit
Does anyone know how to scan from an at home wireless printer? As some people have said, you shouldn't need a printer after you print out the final (if that's how they have us do it). You can then use an app such as "Scannable" that allows you to scan pictures together as a PDF then upload.
- Sat Mar 14, 2020 3:30 pm
- Forum: Administrative Questions and Class Announcements
- Topic: final tech malfunctions
- Replies: 5
- Views: 417
Re: final tech malfunctions
We'll probably have to download and print the final, do our work by hand, and then scan and upload the completed final. If your computer or wifi crashes, I think you should still be able to do it by phone.
- Sat Mar 14, 2020 3:28 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Final- general questions
- Replies: 12
- Views: 862
Re: Final- general questions
CNourian2H wrote:Do you know what time tomorrow he is going to send the test out?
No, Lavelle never said what time he would update us, but it has to be sometime today (although it's getting late).
- Sat Mar 14, 2020 3:23 pm
- Forum: Student Social/Study Group
- Topic: Review Sessions
- Replies: 4
- Views: 399
Re: Review Sessions
Here's one for the first half of the quarter. viewtopic.php?f=160&t=62044&p=236759&hilit=review+sessions&sid=a8cd0b5608d8cc5fa29e9b0c55df7945#p236759
- Sat Mar 14, 2020 3:08 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Catalysts on Final
- Replies: 7
- Views: 524
Re: Catalysts on Final
Maybe we would have to identify which substance is a catalyst, given steps of a reaction. Or perhaps conceptual questions about the effect of a catalyst?
- Sat Mar 14, 2020 3:06 pm
- Forum: Calculating Work of Expansion
- Topic: Increase/Decrease
- Replies: 6
- Views: 450
Re: Increase/Decrease
Expansion causes an increase in work because more work is required to push against an external pressure, whether it be the atmosphere or another thing exerting the pressure.
- Sat Mar 14, 2020 12:33 pm
- Forum: Administrative Questions and Class Announcements
- Topic: test 2 return
- Replies: 6
- Views: 609
Re: test 2 return
Email your TA. I think they've been scanning the tests for people.
- Fri Mar 13, 2020 6:01 pm
- Forum: Student Social/Study Group
- Topic: thoughtful poetry time + lavelle appreciation
- Replies: 6
- Views: 482
Re: thoughtful poetry time + lavelle appreciation
Lavelle - If you see this, thank you for your efforts in making this smooth for all of us. Sorry you haven't gotten enough sleep :( It's been a fun ride with you!
- Fri Mar 13, 2020 5:51 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Final
- Replies: 11
- Views: 702
Re: Final
I believe the final will be posted at 11:30 am on Sunday, the scheduled time. I think it'll either be posted on Lavelle's website and he'll email the link to us. It should be 3 (maybe 4?) hours long. Lavelle hasn't announced how we will download/turn it in yet.
- Fri Mar 13, 2020 5:42 pm
- Forum: Student Social/Study Group
- Topic: Tips for Staying Focused
- Replies: 64
- Views: 3580
Re: Tips for Staying Focused
I've also been finding it hard to sit down and study, but I know it's important to get into a good habit since next quarter will be like this. I think finding a quiet spot would be super helpful in being able to just sit down and grind for a bit. Definitely setting a routine time to get up and study...
- Mon Mar 09, 2020 10:50 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: In lecture example
- Replies: 1
- Views: 168
Re: In lecture example
Absorption is the process by which a fluid is dissolved by a liquid or a solid, and it involves the entire absorbent. Adsorption is the process by which parts of a substance (it could be gas, liquid or dissolved solid) adhere to a surface of the adsorbent. Lavelle said that adsorption is when reacta...
- Mon Mar 09, 2020 9:10 pm
- Forum: Ideal Gases
- Topic: Partial Pressure
- Replies: 13
- Views: 693
Re: Partial Pressure
Remember that decreasing the volume of a system causes pressure to increase, since the same number of moles in a smaller space will collide more frequently. If you the pressure of the whole system increases due to a decrease in volume, the system will want to negate that change and restore equilibri...
- Fri Mar 06, 2020 10:50 am
- Forum: Administrative Questions and Class Announcements
- Topic: Solutions Manual Errors
- Replies: 6
- Views: 436
Re: Solutions Manual Errors
Are there also errors in the back of the textbook?
- Fri Mar 06, 2020 10:48 am
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: non ideal gases
- Replies: 6
- Views: 615
Re: non ideal gases
Yes, n is the number of moles of electrons transferred in the redox reaction. After writing the two half-reactions, make sure they have an equal number of electrons being transferred, so that they cancel out when you add the half-reactions back together. Multiply the reactants and products in a reac...
- Fri Mar 06, 2020 10:27 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Signs of Enaught
- Replies: 7
- Views: 555
Re: Signs of Enaught
A negative E naught means that the reverse reaction is spontaneous.
- Sat Feb 22, 2020 4:13 pm
- Forum: Phase Changes & Related Calculations
- Topic: Van't Hoff Eq
- Replies: 8
- Views: 645
Re: Van't Hoff Eq
I believe we don't need to know how to derive any equations in this class, just what they mean and how to use them.
- Sat Feb 22, 2020 4:05 pm
- Forum: General Science Questions
- Topic: THE RETURN OF DJ LAVELLE [ENDORSED]
- Replies: 6
- Views: 406
Re: THE RETURN OF DJ LAVELLE [ENDORSED]
Ready for some good vibes - thank you Dr. Lavelle!
- Sat Feb 22, 2020 4:00 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: E cell
- Replies: 3
- Views: 262
Re: E cell
Should it be lnK or lnQ when it reaches equilibrium or the two have the same value. When a reaction reaches equilibrium, the reaction quotient Q (which you solve for the same way as K, but Q is for any stage of the reaction) is equal to the equilibrium constant K. So, lnK and lnQ have the same value.
- Sat Feb 22, 2020 3:57 pm
- Forum: Van't Hoff Equation
- Topic: Van't Hoff Equation
- Replies: 2
- Views: 204
Re: Van't Hoff Equation
The Van't Hoff Equation shows how the equilibrium constant K depends on temperature. It can be used to calculate K at a different temperature if ΔH° is known, assuming ΔS°is constant.
- Sat Feb 22, 2020 3:42 pm
- Forum: Balancing Redox Reactions
- Topic: Finding moles of the reaction
- Replies: 4
- Views: 481
Re: Finding moles of the reaction
n is the number of moles of electrons transferred in the balanced redox reaction. Write the half reactions and balance them by adding electrons.
For example, Pb2+ + Ni → Ni2+ + Pb can be written as two half reactions:
Ni → Ni2+ + 2e-
Pb2+ + 2e- → Pb
2 moles of electrons are transferred.
For example, Pb2+ + Ni → Ni2+ + Pb can be written as two half reactions:
Ni → Ni2+ + 2e-
Pb2+ + 2e- → Pb
2 moles of electrons are transferred.
- Fri Feb 21, 2020 4:55 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell Diagram
- Replies: 2
- Views: 165
Re: Cell Diagram
The single lines separating the two half-reactions separate the oxidation reaction (anode) and reduction reaction (cathode). You will see the same element with written once and then again with a more positive charge as part of the oxidation half-reaction, and another element that is becoming more ne...
- Sun Feb 16, 2020 8:54 pm
- Forum: Van't Hoff Equation
- Topic: Hoff Equation
- Replies: 4
- Views: 172
Re: Hoff Equation
The Van't Hoff Equation shows how the equilibrium constant K depends on temperature. It can be used to calculate K at a different temperature if ΔH° is known, assuming ΔS°is constant.
- Sun Feb 16, 2020 8:49 pm
- Forum: Balancing Redox Reactions
- Topic: Redox Reactions
- Replies: 12
- Views: 532
Re: Redox Reactions
Redox reactions are also known as oxidation-reduction reactions because both oxidation and reduction occur, in two half-reactions. Electrons are transferred between species, changing the species' oxidation numbers.
- Sun Feb 16, 2020 8:47 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: delatG= -RTInK
- Replies: 4
- Views: 554
Re: delatG= -RTInK
To add on, K (equilibrium constant) is easy to measure as opposed to Gibbs Free Energy.
- Sun Feb 16, 2020 8:12 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: endo/exo and temp
- Replies: 12
- Views: 1085
Re: endo/exo and temp
Think of heat as either a reactant being absorbed by the reaction (endothermic) or product being given off the reaction (exothermic). If temperature is increased, the reaction will shift away from the side that the heat is on. If temperature is decreased, heat will shift to that side.
- Sat Feb 15, 2020 3:48 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Negative work
- Replies: 14
- Views: 892
Re: Negative work
When a system pushes against an external force (pressure), it loses energy and thus work is negative. Usually this causes volume to expand.
- Fri Feb 07, 2020 10:52 am
- Forum: Administrative Questions and Class Announcements
- Topic: Grading
- Replies: 7
- Views: 226
Re: Grading
Lavelle outlines the grading scheme in the syllabus: Weekly Homework (5 pts per week): 50 pts Chemistry Community (5 pts per week): 50 pts Test 1: 50 pts Midterm: 120 pts Test 2: 50 pts Final: 180 pts Total: 500 pts 50% or higher is required to pass with a C- or higher. He said that the class doesn'...
- Fri Feb 07, 2020 10:30 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Combustion Reactions
- Replies: 4
- Views: 116
Re: Combustion Reactions
A combustion reaction involves a hydrocarbon (compounds that contains only carbon and hydrogen) burning in (reacting with) diatomic oxygen to produce carbon dioxide and water. You would balance the O 2 last, and you might need to use a fractional coefficient before multiplying all the coefficients b...
- Fri Feb 07, 2020 10:22 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: using ratios for R
- Replies: 3
- Views: 80
Re: using ratios for R
I believe you also use ratios for R to get everything to have the same units. You can use the ratios of R because they would cancel out (like multiplying by a fraction that equals 1).
- Fri Feb 07, 2020 10:20 am
- Forum: Phase Changes & Related Calculations
- Topic: HW problems 4B.3
- Replies: 2
- Views: 225
Re: HW problems 4B.3
I got 490 J as well. The solution manual says that's the answer, so the book must be incorrect.
- Fri Feb 07, 2020 10:14 am
- Forum: Phase Changes & Related Calculations
- Topic: Heating Curve Phase Changes
- Replies: 11
- Views: 583
Re: Heating Curve Phase Changes
Temperature doesn't change during a phase change. Heat added to a substance either raises the temperature or causes a phase change, but not both simultaneously. If a solid is heated at its melting point, its temperature remains the same until it has completely melted because melting requires energy....
- Fri Jan 31, 2020 10:49 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Work of expansion equation
- Replies: 4
- Views: 144
Re: Work of expansion equation
The system must do the work of expansion by pushing against P, the external pressure. The system loses energy due to this work, so the negative sign is put to account for that.
- Fri Jan 31, 2020 10:46 am
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Closed vs isolated systems
- Replies: 24
- Views: 831
Re: Closed vs isolated systems
A closed system is physically closed but not thermodynamically closed, meaning that although matter cannot be exchanged between the system and its surroundings, energy can. An example would be a sealed beaker of water, which doesn't insulate, or a pan with a lid on top of it on the stove. An isolate...
- Fri Jan 31, 2020 10:42 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Bond Enthalpies
- Replies: 5
- Views: 203
Re: Bond Enthalpies
Aside from the fact that bond enthalpies of non-diatomic molecules are averages from the bonds of many different molecules, their values may vary depending on which chart you use. Since there's no universally agreed upon standard for which molecules are used to determine a bond, those making the cha...
- Fri Jan 31, 2020 10:35 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: accuracy of bond enthalpies
- Replies: 8
- Views: 366
Re: accuracy of bond enthalpies
For all molecules that are not diatomic, their bond enthalpies are averages from the bonds in many different molecules. For example many molecules can have a C-H bond, and the bond enthalpies of each one is different.
- Fri Jan 31, 2020 10:30 am
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Isolated vs Closed [ENDORSED]
- Replies: 34
- Views: 4100
Re: Isolated vs Closed [ENDORSED]
A closed system is physically closed but not thermodynamically closed, meaning that although matter cannot be exchanged between the system and its surroundings, energy can. An example would be a sealed beaker of water, which doesn't insulate, or a pan with a lid on top of it on the stove. An isolate...
- Sun Jan 26, 2020 3:49 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: hess's law
- Replies: 5
- Views: 225
Re: hess's law
Hess's Law states that enthalpy is a state function, so its value is determined by its current state, not the path taken to obtain that state. Thus, the total enthalpy change of a multi-step reaction can be calculated by adding the enthalpy change at each step of the reaction.
- Sun Jan 26, 2020 3:46 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Ideal Gas QUestions
- Replies: 8
- Views: 396
Re: Ideal Gas QUestions
If temperature is held constant and there's a decrease in volume, the same amount of molecules will be moving in a smaller space and will collide more often, leading to an increase in pressure. If volume increases, molecules will have more space and collide less frequently, decreasing pressure.
- Sun Jan 26, 2020 2:26 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Standard enthalpy of element in most stable form
- Replies: 5
- Views: 346
Re: Standard enthalpy of element in most stable form
Elements in their standard state have a standard enthalpy of formation of 0 because they are are not formed, they just exist. They don't require any energy to get to their most stable form if they're already in that form.
- Sat Jan 25, 2020 11:15 am
- Forum: Phase Changes & Related Calculations
- Topic: Steam Burn
- Replies: 6
- Views: 206
Re: Steam Burn
Lavelle was explaining how getting burned by steam is more severe than getting burned by boiling water. This is because when steam (water in gas form) hits your skin, it undergoes a phase change to become a liquid. This phase change as the steam hits your skin and becomes liquid releases energy, cau...
- Sat Jan 25, 2020 11:11 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Hess's Law
- Replies: 5
- Views: 142
Re: Hess's Law
Hess's Law states that enthalpy is a state function, so its value is determined by its current state, not the path taken to obtain that state. Thus, the total enthalpy change of a multi-step reaction can be calculated by adding the enthalpy change at each step of the reaction.
- Sat Jan 18, 2020 1:32 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Validating Approximation
- Replies: 2
- Views: 88
Re: Validating Approximation
You would divide what you found to be x by the initial concentration, which is given, then multiple by 100 to get the percentage of the initial concentration that has been deprotonated.
- Fri Jan 17, 2020 5:19 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Tips for Test
- Replies: 23
- Views: 1080
Re: Tips for Test
Yes, we're being tested on chemical equilibrium and acids and bases. I'd review lecture notes and examples and do problems in the textbook.
- Fri Jan 17, 2020 5:12 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Quadratic
- Replies: 10
- Views: 253
Re: Quadratic
Ruby Richter 2L wrote:If you do the quadratic equation and get a positive and negative number would you just discredit the negative number? Why?
Because you can't have a negative concentration
- Fri Jan 17, 2020 3:41 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Kc & Kp
- Replies: 12
- Views: 283
Re: Kc & Kp
gabbymaraziti wrote:Can we just use K and not specify Kc or Kp? Or would we be marked down?
I don't think you'll be marked down for using K.
- Fri Jan 17, 2020 3:37 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 5 percent rule
- Replies: 10
- Views: 497
Re: 5 percent rule
Divide the x value that you find by the initial concentration to check if it is less than 5% of the initial concentration (less than 5% is deprotonated). This checks if it is small enough to disregard if being subtracted from the initial concentration, making your calculations much easier.
- Sat Jan 11, 2020 3:14 pm
- Forum: Ideal Gases
- Topic: K vs Q [ENDORSED]
- Replies: 7
- Views: 572
Re: K vs Q [ENDORSED]
K is the equilibrium constant, while Q is the reaction quotient. Though they are calculated the same way, Q can be calculated at any time during the reaction, while K represents when the reaction is at equilibrium. If Q<K, then [reactants] > [products] and the forward reaction is favored. The opposi...
- Sat Jan 11, 2020 3:01 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Temperature- Endothermic and Exothermic Reactions
- Replies: 3
- Views: 84
Re: Temperature- Endothermic and Exothermic Reactions
There are a couple ways to tell if a reaction is endothermic or exothermic. One way is to see if heat is a reactant of product. If heat is released as a product of the reaction, the reaction is exothermic. If heat is listed on the side of the reactants, it is being absorbed and the reaction is endot...
- Sat Jan 11, 2020 2:50 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Exothermic and endothermic reactions
- Replies: 4
- Views: 122
Re: Exothermic and endothermic reactions
You can think of heat like a reactant or product, depending on whether the reaction is endothermic or exothermic, and apply the same rules by Le Chatelier's Principle as you would do with other reactants and products to figure out which way the reaction will shift.
- Sat Jan 11, 2020 2:19 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: K values
- Replies: 4
- Views: 142
Re: K values
K=1 tells you that there is about the same amount of products as there are reactants, so the energies of products and reactants are equal. An equilibrium reaction is dynamic and the forward and reverse reactions are constantly occurring, so it's rare for the two to have the same amount at the same t...
- Sat Jan 11, 2020 1:50 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Le Chatelier's Principle
- Replies: 19
- Views: 1614
Re: Le Chatelier's Principle
Le Chatelier's Principle can predict the effect of a change in conditions on chemical equilibria. If there is a change in conditions, the equilibrium will shift to counteract the effect of the constraint.
- Sat Jan 11, 2020 1:16 pm
- Forum: Ideal Gases
- Topic: Topics on Test 1
- Replies: 37
- Views: 1255
Re: Topics on Test 1
Definitely the topics on Outline 1, but I don't know if we'll get to Outline 2 by the time of the test.
- Sun Dec 08, 2019 10:39 pm
- Forum: Limiting Reactant Calculations
- Topic: A different way
- Replies: 8
- Views: 827
Re: A different way
I think this is the best way to do it since many problems ask you how much product will be formed anyway, so you're essentially answering that question while you determine the limiting reactant. Just convert moles of each reactant to moles of the product you'll be looking for.
- Sun Dec 08, 2019 10:37 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Uncertainty
- Replies: 5
- Views: 314
Re: Uncertainty
Delta x represents the uncertainty in position. You can use Heisenberg's Uncertainty Principle (uncertainty of position)(uncertainty of momentum) is greater than or equal to (Planck's Constant /4 pi).
- Sun Dec 08, 2019 10:27 pm
- Forum: Calculating the pH of Salt Solutions
- Topic: pH
- Replies: 6
- Views: 324
Re: pH
The pH scale is based on the self-ionization of water, where two water molecules combine to form hydronium and hydroxide ions. pH is a measurement of how acidic a solution is. A higher concentration of the hydronium ion means the solution is acidic and will have a lower pH (below 7), while a higher ...
- Sun Dec 08, 2019 10:14 pm
- Forum: Biological Examples
- Topic: Heme complex & O2
- Replies: 5
- Views: 277
- Sun Dec 08, 2019 10:11 pm
- Forum: Student Social/Study Group
- Topic: Cyanide
- Replies: 5
- Views: 488
Re: Cyanide
After drawing the Lewis structure, you would count the number of valence electrons of one of the atoms, then subtract the number of bonds that atom makes, then subtract the number of lone electrons on that atom. So valence electrons - (# bonds + # lone electrons).
- Sun Dec 08, 2019 10:05 pm
- Forum: Administrative Questions and Class Announcements
- Topic: curve
- Replies: 8
- Views: 617
Re: curve
I'm not sure how he's going to curve or how much, but I think he may curve at the end after final grades are determined.
- Sat Nov 30, 2019 5:24 pm
- Forum: Bronsted Acids & Bases
- Topic: Weak Acid
- Replies: 2
- Views: 132
Re: Weak Acid
Acetic acid only ionizes partly in water (there aren't as many separate acetate and hydrogen ions as whole acetic acid molecules). Acetic acid partially dissociates and releases only some of its hydrogen atoms into the solution and is less capable of losing and donating protons = definition of a wea...
- Sat Nov 30, 2019 4:02 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Final Exam Content
- Replies: 14
- Views: 745
Re: Final Exam Content
Will the final have more questions about the content we learned after the midterm or will it be cover the entire quarter evenly? I don't think Lavelle mentioned this, but it's worth asking your TA. I'm guessing there will probably be a good chunk of questions on content we learned after the midterm...
- Sat Nov 30, 2019 3:16 pm
- Forum: Student Social/Study Group
- Topic: Final Exam
- Replies: 3
- Views: 170
Re: Final Exam
It's on Sunday, December 8, from 11:30 am to 2:30 pm.
- Sat Nov 30, 2019 3:15 pm
- Forum: Student Social/Study Group
- Topic: Final
- Replies: 2
- Views: 209
Re: Final
Lavelle said in an email that Wednesday is the last day we'll learn new material.
- Sat Nov 30, 2019 3:10 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Weak Acids & Bases
- Replies: 6
- Views: 381
Re: Weak Acids & Bases
Weak Acids:
Acetic acid (CH3COOH), carbonic acid (H2CO3), hydrofluoric acid (HF), hydrocyanic acid (HCN), phosphoric acid (H3PO4)
Weak Bases:
Ammonia (NH3), methylamine (CH3NH2), diethylamine ((CH3CH2)2NH)
Acetic acid (CH3COOH), carbonic acid (H2CO3), hydrofluoric acid (HF), hydrocyanic acid (HCN), phosphoric acid (H3PO4)
Weak Bases:
Ammonia (NH3), methylamine (CH3NH2), diethylamine ((CH3CH2)2NH)
- Sat Nov 30, 2019 2:13 pm
- Forum: Hybridization
- Topic: Counting Charge Clouds
- Replies: 2
- Views: 314
Re: Counting Charge Clouds
It doesn't matter what type of bond exists there - it counts as one charge cloud.
- Sat Nov 30, 2019 1:44 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Chemistry Community Posts
- Replies: 10
- Views: 605
Re: Chemistry Community Posts
They should be added weekly but sometimes take a while to be added to your grade
- Sun Nov 24, 2019 8:58 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: T Shape
- Replies: 3
- Views: 175
Re: T Shape
Trigonal bipyramidal is a type of electron arrangement or geometry, while T-shape is a type of molecular geometry. Any time there are 5 electron groups, the molecule has a trigonal bipyramidal electron arrangement. Lone pairs of electrons are taken into account for molecular geometry. Yes, the rest ...
- Sun Nov 24, 2019 8:19 pm
- Forum: Lewis Structures
- Topic: Bent or Angular?
- Replies: 18
- Views: 1052
Re: Bent or Angular?
Both are correct but Lavelle uses "bent".
- Sun Nov 24, 2019 8:16 pm
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: paramagnetism
- Replies: 8
- Views: 668
Re: paramagnetism
Paramagnetic compounds have at least one unpaired (paramagnetic) electron while diamagnetic compounds have all paired electrons. Paramagnetic compounds are attracted to magnetic fields, while diamagnetic compounds are repelled.
- Sun Nov 24, 2019 8:00 pm
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: Bond order
- Replies: 5
- Views: 423
Re: Bond order
Bond order is the number of chemical bonds between atoms. To find bond order, count the number of bonds in a molecule and divide that by the number of bonding regions. For example, NO3- has 4 bonds, comprised of two single bonds and one double bond. You would divide 4 bonds by 3 bonding regions/bond...
- Sun Nov 24, 2019 7:46 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: dipole-dipole vs induced dipole
- Replies: 9
- Views: 548
Re: dipole-dipole vs induced dipole
Why is the molecule OCS is considered polar,shouldn't their dipoles cancel out making the molecule non-polar? Oxygen is more electronegative than sulfur, which means the C-S bond will have a stronger partial negative charge on the sulfur and the C-O bond will have a weaker partial negative charge o...
- Sun Nov 24, 2019 7:22 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Non-polar atoms with lone pairs
- Replies: 4
- Views: 268
Re: Non-polar atoms with lone pairs
I have a follow-up question: How can we tell that dipole moment vectors cancel when they are at angles to one another (e.g. in a molecule with trigonal planar geometry)? Do we have to break up the vectors into their individual components? If all the bonds are between the same 2 atoms, they cancel o...
- Sun Nov 24, 2019 3:12 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bent Shape
- Replies: 31
- Views: 2836
Re: Bent Shape
If a molecular had 2 bonding groups and 1 lone pair, or 2 bonding groups and 2 lone pairs, the molecular shape would be bent.
- Sun Nov 17, 2019 6:13 pm
- Forum: Dipole Moments
- Topic: SCl4 Molecule
- Replies: 5
- Views: 945
Re: SCl4 Molecule
When there's a lone pair, it makes the molecular polar because the molecule isn't symmetrical and electrons won't be uniformly distributed.
- Sun Nov 17, 2019 6:01 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bond Order
- Replies: 3
- Views: 250
Re: Bond Order
You don't need to know bond order in order to find bond angle or bond length. But to find each one, it'd be helpful to draw the Lewis structure.
- Sun Nov 17, 2019 5:53 pm
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: bond order calculations
- Replies: 4
- Views: 812
Re: bond order calculations
To find bond order, count the number of bonds in a molecule and divide that by the number of bonding regions. For example, NO 3 - has 4 bonds, comprised of two single bonds and one double bond. You would divide 4 bonds by 3 bonding regions/bond groups to get a bond order of 1.33. For H 2 , you'd div...
- Sun Nov 17, 2019 5:30 pm
- Forum: Sigma & Pi Bonds
- Topic: Sigma V Pi
- Replies: 5
- Views: 432
Re: Sigma V Pi
Sigma bonds form between two atoms along the x-axis, and pi bonds form from p-orbital overlap and connect atoms along the y-axis. Sigma bonds are single bonds, pi bonds are the bonds that form after that.
- Sun Nov 17, 2019 3:27 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: VSEPR shape question
- Replies: 2
- Views: 99
Re: VSEPR shape question
Linear, and the bond angle would be 180 degrees.
- Sun Nov 17, 2019 3:25 pm
- Forum: Bond Lengths & Energies
- Topic: Quiz for Next week dashes/wedges
- Replies: 11
- Views: 588
Re: Quiz for Next week dashes/wedges
In class he mentioned that we can just draw a normal Lewis Structure as long as we name the shape I think. Do we have to worry about where we arrange the atoms around the central atom (example: drawing a tetrahedral shape vs square planar) or can we just draw it normally and name the shape after? L...
- Sun Nov 10, 2019 3:50 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: How to Draw Dipole Arrows
- Replies: 8
- Views: 2660
Re: How to Draw Dipole Arrows
After drawing a Lewis structure, you'd draw a dipole arrow pointing towards the atom with higher electronegativity. This is because this atom attract electrons and gains a partial positive charge. The other atom involved in the bond, the one with the lower electronegativity, would have a partial pos...
- Sat Nov 09, 2019 11:33 pm
- Forum: Electronegativity
- Topic: Periodic Trend
- Replies: 13
- Views: 736
Re: Periodic Trend
Electronegativity refers to how strongly an atom attracts bonding electrons to itself. Higher electronegativity means an atom is more likely to attract electrons. EN increases from left to right because more protons means there is a stronger attracted between the positively charged nucleus and negat...
- Sat Nov 09, 2019 11:24 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Formal Charge
- Replies: 9
- Views: 1418
Re: Formal Charge
The most stable Lewis structure for an ion is the one that minimizes formal charges (minimize having separate charges). Also, the negative formal charge should be on the most electronegative atom.
- Sat Nov 09, 2019 2:51 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: Intermolecular forces
- Replies: 3
- Views: 147
Re: Intermolecular forces
Yes, hydrogen-bonding is the strongest intermolecular force. It's between the hydrogen atom of one molecule and an atom of another molecule with high electronegativity.
- Sat Nov 09, 2019 2:47 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: 8
- Views: 412
Re: Hydrogen bonding
N, O, and F are the most electronegative elements (upper righthand corner of the periodic table). Hydrogen will only form hydrogen bonds with them because the electronegative atoms attract the electron cloud around hydrogen and leave hydrogen with a positive charge.
- Sat Nov 09, 2019 2:02 pm
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Polar Covalent VS Ionic
- Replies: 11
- Views: 622
Re: Polar Covalent VS Ionic
If you're given an electronegativity table, you can take the absolute value of the difference between the electronegativity values of each atom in the bond. A difference of >1.7 means the bond is ionic, 0.4-1.7 means the bond is polar covalent, and <0.4 means the bond is nonpolar covalent.
- Sun Oct 27, 2019 6:24 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: p-orbitals
- Replies: 11
- Views: 390
Re: p-orbitals
You don't need to write Px, Py, or Pz.
- Sun Oct 27, 2019 6:23 pm
- Forum: Ionic & Covalent Bonds
- Topic: Writing Electron Configurations for an Ion
- Replies: 6
- Views: 270
Re: Writing Electron Configurations for an Ion
Yes, that's all that changes!
- Sun Oct 27, 2019 6:22 pm
- Forum: General Science Questions
- Topic: Extra Credit
- Replies: 19
- Views: 747
Re: Extra Credit
I don't think so.
- Sun Oct 27, 2019 6:21 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Thanksgiving
- Replies: 3
- Views: 117
Re: Thanksgiving
I think we will.
- Sun Oct 27, 2019 6:20 pm
- Forum: Properties of Electrons
- Topic: Electron removal
- Replies: 11
- Views: 383
Re: Electron removal
The positively charged nucleus is further from these negatively charged electrons, so its pull is not as strong.
- Sun Oct 27, 2019 6:03 pm
- Forum: Resonance Structures
- Topic: Determining Resonance Structures
- Replies: 6
- Views: 261
Re: Determining Resonance Structures
There is no ideal resonance structure. The sulfate ion could be drawn with the double bond between the central S atom and any of the various O atoms. The formal charge doesn't change because you're not changing the elements that have that specific bond. The double bond is still between S and O.
- Sun Oct 27, 2019 5:55 pm
- Forum: Trends in The Periodic Table
- Topic: Central Atom
- Replies: 13
- Views: 478
Re: Central Atom
It's usually the atom that creates the most bonds (has fewest valence electrons).
- Sun Oct 20, 2019 5:05 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: Difference in Quantum Numbers?
- Replies: 2
- Views: 88
Re: Difference in Quantum Numbers?
The principle quantum number (n) determines energy level and size of an orbital an electron is in (shell) The angular momentum number (l) describes the shape of the orbital, and it refers to the number of subshells The magnetic quantum number (m l ) labels the different energy levels/orbitals of a s...
- Sun Oct 20, 2019 4:59 pm
- Forum: Properties of Electrons
- Topic: Hund's Rule
- Replies: 5
- Views: 203
Re: Hund's Rule
Hund's Rule says that every orbital in a sublevel must be occupied by one electron before any orbital is occupied by two electrons, and all of these lone electrons have the same spin.
- Sat Oct 19, 2019 12:29 pm
- Forum: SI Units, Unit Conversions
- Topic: How to express answers
- Replies: 13
- Views: 474
Re: How to express answers
I don't believe that sig figs are too important in this class. My TA told us that sig figs are not too big of a deal, as long as you do not round to whole numbers or to only 1 decimal place when the answer should clearly have 2 or 3 decimal places. As for scientific notation, I believe that it is m...
- Sat Oct 19, 2019 12:21 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: building up principle
- Replies: 5
- Views: 163
Re: building up principle
Dr. Lavelle mentioned two exceptions in class to the Aufbau principle: Chromium and Copper. Could someone please explain what those exceptions are and why they are there? These exceptions are that these elements do not follow the normal filling order for typical electron configurations. This occurs...
- Sat Oct 19, 2019 12:12 pm
- Forum: *Shrodinger Equation
- Topic: Electron Distribution Definition
- Replies: 4
- Views: 187
Re: Electron Distribution Definition
It means density, so electron density is the probability of finding an electron in that location. In an area with higher electron density, you're more likely to find an electron there.
- Sun Oct 13, 2019 5:09 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Best Way To Study?
- Replies: 56
- Views: 3364
Re: Best Way To Study?
I read the textbook for sections we cover in class as a way to supplement lectures and clear up anything I don't completely understand during lecture. Aside from watching his audio-visual focus modules, Khan Academy can be a great resource.
- Sun Oct 13, 2019 5:06 pm
- Forum: DeBroglie Equation
- Topic: P
- Replies: 3
- Views: 134
Re: P
Since p, momentum, is the mass of an object times its velocity, the unit for mass (kg) times the unit for velocity (m/s) will yield (kg)(m)/(s)
- Sun Oct 13, 2019 4:58 pm
- Forum: Properties of Light
- Topic: speed of light
- Replies: 10
- Views: 294
Re: speed of light
The speed of light in a vaccuum is 3.00x10^8 m/s. It is slower in mediums like air, water, and glass. I think that for this class we'll just use this value.