As my last post for chemistry community ever:
Never trust an atom...
I've heard they make up everything...
Search found 104 matches
- Thu Mar 12, 2020 2:14 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3005038
- Thu Mar 12, 2020 2:02 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: liquid mercury
- Replies: 3
- Views: 273
liquid mercury
I was studying electrochemistry and saw that for a galvanic cell, liquid mercury can act as an electrode. How is this possible?
- Thu Mar 12, 2020 1:54 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: translational and rotational contribution from molecular motion
- Replies: 3
- Views: 295
Re: translational and rotational contribution from molecular motion
The effect of translational and rotational momentum is covered in the chemistry textbook, however it is not of extreme importance. It is mainly used to derive the equations for the energy of ideal monoatomic gasses.
- Thu Mar 12, 2020 1:09 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: 6L5. B)
- Replies: 2
- Views: 204
Re: 6L5. B)
I believe its because solid iodine cant be a conducting solid. It is a very brittle solid as it is not held together by ionic bonds but rather covalent bonds and intermolecular forces. Metals or Ionic solids can be electrodes, however.
- Thu Mar 12, 2020 1:05 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: Rate of the reverse reaction
- Replies: 3
- Views: 253
Rate of the reverse reaction
Why can we ignore the rate of the reversion reaction when doing kinetics? Do the rate laws, such as rate = K [R1] [R2], give just the initial rate of the reaction or the rate of the reaction as it progresses?
- Sun Mar 08, 2020 2:04 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Adding carbon (gr) to cell diagrams
- Replies: 4
- Views: 332
Re: Adding carbon (gr) to cell diagrams
As far as I understand it, Carbon Graphite is just another alternative to platinum. Whenever you can use platinum you can also use carbon graphite. But as you said, platinum is much more common.
- Sun Mar 08, 2020 2:03 pm
- Forum: General Science Questions
- Topic: Review Packet
- Replies: 14
- Views: 1168
Re: Review Packet
There have been no announcements yet about a review packet. I would imagine though that it would be announced in Monday's lecture if there is one. If not, then there probably isn't.
- Sun Mar 08, 2020 2:01 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Study Advice
- Replies: 73
- Views: 6767
Re: Study Advice
Also, If your schedule does not align with any review sessions, reading the assigned chapters in the book helps a lot. I know it takes quite a long time; you don't have to read everything, just what you need help on. OFten the book explains concepts very clearly and gives step by step problems.
- Sun Mar 08, 2020 1:59 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: concentration cells
- Replies: 5
- Views: 398
Re: concentration cells
To clarify, the reaction is still considered a redox reaction. However, it is also important to note that the standard cell potential of every concentration cell equals 0.
- Sun Mar 08, 2020 1:56 pm
- Forum: General Rate Laws
- Topic: Instantaneous and average reaction rate
- Replies: 4
- Views: 318
Re: Instantaneous and average reaction rate
The rate laws are instantaneous rates. Usually, the average rate won't be asked for unless the give you a chart of data.
- Sun Mar 01, 2020 11:53 pm
- Forum: General Rate Laws
- Topic: class notes
- Replies: 2
- Views: 242
Re: class notes
Often, chemical reactions may be understood as a series of reactions acting in order of steps to take the original reactants to create the final products. This series of steps is called the reaction mechanism. The slowest step of the reaction mechanism often determines the order of the reaction.
- Sun Mar 01, 2020 11:49 pm
- Forum: Zero Order Reactions
- Topic: order of reactions
- Replies: 4
- Views: 288
Re: order of reactions
Normally, the order of the reaction must be determined empirically. Often, empirical data is given in the question which you may manipulate to determine the order of the reaction.
- Sun Mar 01, 2020 11:47 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: observing initial rates
- Replies: 3
- Views: 277
Re: observing initial rates
This is because by definition, initial rates refer to the rate of the forward reaction at the moment it has started. Mathematically, this is when t approaches 0.
- Sun Mar 01, 2020 11:46 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: n in Equation
- Replies: 6
- Views: 436
Re: n in Equation
n represents the moles of electrons transferred in a redox reaction. To know how many electrons are transferred, you have to divide a redox reaction into its reduction and oxidation half-reactions.
- Sun Mar 01, 2020 11:44 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Standard E of concentration cell
- Replies: 1
- Views: 137
Re: Standard E of concentration cell
This is because since technically it is the same product and reactant on both sides. Thus the reduction reaction and oxidation reaction have equal magnitude yet opposite sign values for E. Thus when you add them together, they cancel out to equal 0.
- Sun Feb 23, 2020 10:12 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Platinum
- Replies: 4
- Views: 271
Platinum
Can someone explain why platinum was used in the galvanic cell during dr. lavelle's lecture?
- Sun Feb 23, 2020 10:08 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Cell Potential intensive property
- Replies: 2
- Views: 213
Cell Potential intensive property
If cell potential is an intensive property, why does changing the molarity of reagents in a chemical reaction change the cell potential? In lecture we started using principles similar to le chatelier's principle, however, I thought cell potential does not matter on the amount of reagent present
- Sun Feb 23, 2020 9:59 pm
- Forum: Student Social/Study Group
- Topic: Friday lecture 02/21
- Replies: 3
- Views: 290
Re: Friday lecture 02/21
We discussed how three concepts.
1.) how to balance a redox reaction by splitting it into its composite half-reactions and then adding them together
2.) cell diagram notation
3.) the nernst equation
1.) how to balance a redox reaction by splitting it into its composite half-reactions and then adding them together
2.) cell diagram notation
3.) the nernst equation
- Sun Feb 23, 2020 9:50 pm
- Forum: Van't Hoff Equation
- Topic: Constants in Van’t Hoff Equation [ENDORSED]
- Replies: 4
- Views: 403
Re: Constants in Van’t Hoff Equation [ENDORSED]
Yes, delta S and delta H are assumed to not be temperature-dependent, meaning constant, when using the vant hoff equation
- Sun Feb 23, 2020 9:48 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Nernst
- Replies: 7
- Views: 495
Re: Nernst
The Nernst is E=E^{o}-\frac{RT}{nF}ln(Q) E is the cell potential of a reaction not at equilibrium and not at standard conditions E^{o} is the cell potential at standard conditions R is the gas constant T is the temperature of the reaction n is the moles reacting F is faradays constant Q is t...
- Tue Feb 18, 2020 1:50 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Midterm Nerves
- Replies: 7
- Views: 437
Re: Midterm Nerves
A good way to approach problems are to explicitly write down the variables that are given to you. For example, if a problem mentions 6 moles, 278.15 K temperature, and that it is an ideal gas then you should write down n = 6, T = 278.15, and R. Then write down the symbol for the variable(s) you are ...
- Tue Feb 18, 2020 1:43 pm
- Forum: Van't Hoff Equation
- Topic: Constant delta H
- Replies: 4
- Views: 285
Re: Constant delta H
Yes, the Vant Hoff equation can only be applied effectively under the assumption that the entropy change is independent of the temperature of the reaction. This assumption can be made unless explicitly told otherwise.
- Tue Feb 18, 2020 1:42 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Van't Hoff Equation
- Replies: 4
- Views: 394
Re: Van't Hoff Equation
The Van't Hoff Equation is derived from two expressions for Gibbs Free Energy.
- Tue Feb 18, 2020 1:41 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Midterm: Cp,m and Cv,m
- Replies: 3
- Views: 374
Re: Midterm: Cp,m and Cv,m
An easy way to remember all of the Cp,m values is the equation Cp,m = Cv,m + R. This equation is derived in the chemistry book chapter 4, and it lets you only have to memorize the Cv,m for monoatomic, linear, and nonlinear gasses since the Cp,m is just R plus those values.
- Tue Feb 18, 2020 1:38 pm
- Forum: Balancing Redox Reactions
- Topic: Balancing and Adding together Half-Rxns
- Replies: 6
- Views: 305
Re: Balancing and Adding together Half-Rxns
Moreover, chemical reactions are not known to just spontaneously release electrons. First, it is favorable for electrons to be bound to a nucleus since the positive nucleus attracts the negative electron. Second, the products of a chemical reaction require the same amount of electrons as the reactants
- Sun Feb 09, 2020 1:33 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: set up of equation
- Replies: 1
- Views: 164
Re: set up of equation
It does matter as the reaction is not in equilibrium yet, so you must know which side is the reactants and which side is the products because only the reactants will decrease and only the products will increase. The language of the question should inform you which side of the reaction is reactants o...
- Sun Feb 09, 2020 1:29 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Entropy units
- Replies: 7
- Views: 406
Re: Entropy units
The units for entropy and enthalpy may be joules or kilojoules, it is just whatever is most useful for the number of joules there are. However, when doing calculations that include entropy and enthalpy in an equation, of course, you must match up their units--most of the time to joules.
- Sun Feb 09, 2020 1:27 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Spontaneous vs Favorable
- Replies: 8
- Views: 407
Re: Spontaneous vs Favorable
There is no difference between the terms spontaneous and favorable in terms of chemical reactions. The formal term is actually spontaneous, but modern connotations of that word may make it seem that spontaneous reactions happen very quickly. Rather, the term means that the reaction is favorable and ...
- Sun Feb 09, 2020 1:25 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Gas Expansion
- Replies: 3
- Views: 151
Re: Gas Expansion
Dr. Lavelle's lecture pertained specifically to isothermic reversible expansion. In this type of expansion, the delta U equals 0. This is because isothermal reactions mean that once energy is used in the form of work, the system gains that energy back as heat to maintain the same temperature--thus t...
- Sun Feb 09, 2020 1:22 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: Entropy Changes for Phase Changes
- Replies: 1
- Views: 102
Re: Entropy Changes for Phase Changes
A phase change affects the entropy of a molecule because intermolecular bonds are either being broken or formed, which affect how ordered the system is. In cases where intermolecular bonds are being broken--melting and boiling--the entropy increases as atoms are freer to move and occupy more energy ...
- Tue Feb 04, 2020 2:49 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Microstates
- Replies: 5
- Views: 198
Re: Microstates
If there are two possible options for a microstate, then W = 2^N where N is the number of atoms
- Tue Feb 04, 2020 2:48 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Microstates
- Replies: 5
- Views: 198
Re: Microstates
If there are two possible options for a microstate, then W = 2^N where N is the number of atoms
- Tue Feb 04, 2020 2:44 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Relation between Entropy and Enthalpy
- Replies: 1
- Views: 67
Re: Relation between Entropy and Enthalpy
An easy way to conceptualize it is as follows. When you heat up a substance, you give the atoms of that substance more energy. That means those atoms have more positions to be in as well as more energy states to be in. Thus, when you heat up a substance, you increase the Degeneracy W of the substanc...
- Tue Feb 04, 2020 2:42 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Thermochemistry vs Thermodynamics
- Replies: 2
- Views: 202
Re: Thermochemistry vs Thermodynamics
Thermodynamics is the study of heat exchange, work, and energy in general. Thermochemistry is a branch of thermodynamics that applies those concepts to specific chemical reactions. For example, bond-enthalpy is a thermochemistry concept as it applies the thermodynamic concept of energy to chemical b...
- Tue Feb 04, 2020 2:39 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Reversible Isothermic Reaction
- Replies: 1
- Views: 92
Re: Reversible Isothermic Reaction
Understanding this reaction is difficult because of vague terminology. The set up of this reaction is such that the system does not lose any net energy, meaning there is no net change in temperature. What happens is when the gas expands it does work. This work, of course, requires energy, which is d...
- Tue Feb 04, 2020 2:33 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Equation
- Replies: 2
- Views: 147
Re: Equation
As far as Dr. Lavelle has used it in lecture, he only used it in a theoretical sense--not in actual application. Lavelle used this equation to prove that the internal energy U of an isothermal reversible reaction is 0. This is because the temperature is constant for this reaction, and as the equatio...
- Sun Jan 26, 2020 8:58 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Standard Enthalpies of Formation
- Replies: 4
- Views: 89
Re: Standard Enthalpies of Formation
Standard enthalpies of formation are given for certain molecules in the tables of the textbook. The standard enthalpy of a reaction though should be calculated.
- Sun Jan 26, 2020 8:54 pm
- Forum: Phase Changes & Related Calculations
- Topic: Class Lecture to Textbook
- Replies: 2
- Views: 103
Re: Class Lecture to Textbook
We discussed section 4C i believe
- Sun Jan 26, 2020 8:54 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Bond vs Standard Enthalpies
- Replies: 1
- Views: 85
Re: Bond vs Standard Enthalpies
Bond Enthalpies refer to the energy stored in a certain type of bond--whether it be single, double, or triple--and the specific atoms that are being bonded Standard Enthalpies of Formation refer to the energy stored in a molecule calculated from the reaction of its formation from the most stable for...
- Sun Jan 26, 2020 8:51 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Standard enthalpy of formation of pure elements?
- Replies: 1
- Views: 115
Re: Standard enthalpy of formation of pure elements?
The standard enthalpy of formation by definition refers to the energy of the reaction required to produce a molecule from the most stable states of its constituent atoms. For example, the reaction for the stand enthalpy of formation for Hydrogen Iodide is: H_{2} + I_{2} \rightarrow 2HI The standard ...
- Sun Jan 26, 2020 8:43 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Pressure & temperature in chemical equilibria
- Replies: 3
- Views: 88
Re: Pressure & temperature in chemical equilibria
To understand how temperature affects a reaction, one must know whether the reaction is endothermic or exothermic. For temperature increases: Products are favored in endothermic reactions Reactants are favored in exothermic reactions For temperature decreases: Reactants are favored in endothermic re...
- Mon Jan 20, 2020 12:35 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: 5% Rule
- Replies: 6
- Views: 323
Re: 5% Rule
Yes. Moreover, it is important to understand that chemical equilibria and acid-base equilibria are the same exact process. We just have different terms for the Ks of each as acid-base reactions usually involve just proton disassociation. Thus, almost everything you would do for chemical equilibria a...
- Mon Jan 20, 2020 12:33 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Delta G
- Replies: 2
- Views: 68
Re: Delta G
Dr. Lavelle said that Delta G will not be on this exam. He was referencing future material for those who may remember enthalpy from highschool chemistry.
- Mon Jan 20, 2020 12:32 pm
- Forum: *Making Buffers & Calculating Buffer pH (Henderson-Hasselbalch Equation)
- Topic: buffers
- Replies: 2
- Views: 624
Re: buffers
Yes, this material will be on Test 1
- Mon Jan 20, 2020 12:27 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Halogens
- Replies: 2
- Views: 90
Re: Halogens
Halogen anions in solution do not affect the ph as they are weak conjugate bases of their corresponding strong acids: HCl, HBr, Hi, and so on. The only exception to this would be F- anion, as it is a strong conjugate base since HF is a weak acid.
- Mon Jan 20, 2020 12:25 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 6E Polyprotic Acids and Bases
- Replies: 2
- Views: 79
Re: 6E Polyprotic Acids and Bases
A polyprotic acid is an acid that can disassociate more than once. An example of this is phosphoric acid. However, it requires much less energy for this acid to disassociate the first time in comparison to the energy required to disassociate the second or third time. Thus, regarding the Ka of each d...
- Fri Jan 10, 2020 2:33 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Why Q would be greater than K
- Replies: 5
- Views: 106
Re: Why Q would be greater than K
That is correct. Reactions at equilibrium do not naturally stray from equilibrium. That does not only mean that Q would ever increase to higher than K once at equilibrium, but also that it would never decrease lower than K.
- Fri Jan 10, 2020 11:45 am
- Forum: Ideal Gases
- Topic: Chatelier’s Principle
- Replies: 8
- Views: 195
Chatelier’s Principle
Can someone please explain how Le Chatelier’s Principle works? especially with changes in pressure?
- Fri Jan 10, 2020 11:40 am
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Q and relation of [R] to [P]
- Replies: 5
- Views: 360
Re: Q and relation of [R] to [P]
To understand how a reaction will proceed to reach equilibrium, it is important to understand what K and Q represent symbolically. Both represent the ratio of products to reactants in the reaction. However, K represents that ratio at equilibrium, while Q represents that ratio while not at equilibriu...
- Fri Jan 10, 2020 11:22 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: K for Heterogeneous Equilibria
- Replies: 4
- Views: 229
Re: K for Heterogeneous Equilibria
For heterogeneous equilibrium problems, it may be confusing as to use either concentrations or pressure. But recognize, if there are any reactants which are aqueous, it does not make sense to use their partial pressure. Thus, you’d have to use concentration for all reagents in the equilibrium. If th...
- Fri Jan 10, 2020 11:18 am
- Forum: Administrative Questions and Class Announcements
- Topic: Peer Learning
- Replies: 4
- Views: 217
Re: Peer Learning
Peer Learning Sessions are opportunities Dr. Lavelle Provides for students who are either confused on a subject or just need extra help. There are three types of sessions: drop-in sessions, workshops, and step-up sessions.
- Sat Dec 07, 2019 5:59 pm
- Forum: Lewis Acids & Bases
- Topic: Lewis vs Bronsted
- Replies: 3
- Views: 211
Re: Lewis vs Bronsted
Yes, an example is ammonia NH3
All bronsted acids are also lewis acids, but not all lewis acids are bronsted acids.
All bronsted acids are also lewis acids, but not all lewis acids are bronsted acids.
- Sat Dec 07, 2019 5:58 pm
- Forum: Coordinate Covalent Bonds
- Topic: Just to clear it up
- Replies: 16
- Views: 947
Re: Just to clear it up
Yes, all ligands in coordinate compounds are lewis bases because they donate electrons. The central metal atom then is a lewis acid
- Sat Dec 07, 2019 5:56 pm
- Forum: Amphoteric Compounds
- Topic: Amphoteric vs Amphiprotic
- Replies: 13
- Views: 1434
Re: Amphoteric vs Amphiprotic
The difference between amphoteric and amphiprotic lies in understanding the difference between lewis acids and bronsted acids. Bronsted acids require a proton to be donated or accepted. The lewis acid definition encompasses all bronsted acids, but also acids which do not donate protons but rather ju...
- Sat Dec 07, 2019 5:51 pm
- Forum: Acidity & Basicity Constants and The Conjugate Seesaw
- Topic: Conjugate Seesaw
- Replies: 2
- Views: 168
Re: Conjugate Seesaw
I believe you are misundestanind what the conjugate see saw is. The conjugate seesaw refers to the foloowing four concepts 1.) if an acid is strong, the conjugate base is weak 2.) if an acid is weak, the conjugate base is strong 3.) if an base is strong, the conjugate acid is weak 4.) if an base is ...
- Sat Dec 07, 2019 5:48 pm
- Forum: Biological Examples
- Topic: Final
- Replies: 6
- Views: 482
Re: Final
The hydrogen bonding od DNA Base pairs, heme as a coordination compound, cisplatin for chemotherapy, vitamins as acceptors of dangerous radicals, the role of carbon dioxide in blood ph
These are the examples i can think of
These are the examples i can think of
- Mon Dec 02, 2019 12:43 pm
- Forum: Hybridization
- Topic: Key aspect of hybridization
- Replies: 1
- Views: 187
Re: Key aspect of hybridization
Hybridization is when a central atom's orbitals average in their energy levels, creating hybrid orbitals to free up all of their electrons. I think the simplest example demonstrating this is Carbon. Carbon has an electron ground state of [He] 2s^{2} 2p^{2} This means that carbon only has two unpaire...
- Mon Dec 02, 2019 11:48 am
- Forum: Naming
- Topic: Non-anionic ligands
- Replies: 2
- Views: 110
Re: Non-anionic ligands
It is possible to have positively charged ligands, although they are rare because ligands are lewis bases. The charge of the ligand does not matter in naming, but the charge of the central transition metal does matter. So if the positively charged ligand means that the central transition metal has a...
- Mon Dec 02, 2019 11:38 am
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Ferrocene
- Replies: 1
- Views: 76
Re: Ferrocene
Yes the Iron is bonded to the carbon on each side of the "sandwhich"
- Mon Dec 02, 2019 11:34 am
- Forum: Conjugate Acids & Bases
- Topic: Naming
- Replies: 4
- Views: 254
Re: Naming
There are different naming conventions for different types of molecules. Here are the very basic rules Ions: "Cation Name" "Anion Name + ide" ex.) NaCl : Sodium Cholride Covalently Bonded Molecules: "Central Atom's Name" "Greek Suffix + Peripheral Atom's Name + ide...
- Sun Nov 24, 2019 11:55 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: VSEPR formula
- Replies: 5
- Views: 308
Re: VSEPR formula
You do not need to do any mathematical calculations to determine angles. Rather you have to memorize the angles present in each molecular geometry, and that every time a bonding pair of electrons is replaced by a lone pair, those angles decrease. Linear molecules have an angle of 180 Tetrahedral mol...
- Sun Nov 24, 2019 11:53 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Molecular shape of carbon Dioxide
- Replies: 10
- Views: 579
Re: Molecular shape of carbon Dioxide
The molecular geometry of carbon dioxide is linear. This is because there are only two electron density regions: the two double bonds between carbon and each atom.
- Sun Nov 24, 2019 11:51 pm
- Forum: Hybridization
- Topic: Sigma and Pi bonds
- Replies: 3
- Views: 119
Re: Sigma and Pi bonds
Sigma bonds are stronger than pi bonds because the electron clouds between atoms that have a sigma bond overlap more than those electron clouds would overlap in a pi bond. The more overlap between electron clouds in sigma bonds allows for a stronger electronegative attraction between shared electron...
- Sun Nov 24, 2019 11:48 pm
- Forum: Hybridization
- Topic: Sigma and Pi Bonds
- Replies: 21
- Views: 943
Re: Sigma and Pi Bonds
There are two characteristics of bonds that we need to know: the number of bonds and the type of bonds. The number of bonds refers to whether it is a single, double, or triple bond. The type of bond refers to whether the bond is a sigma or pi bond. A sigma bond is one where the electron clouds overl...
- Sun Nov 24, 2019 11:42 pm
- Forum: Hybridization
- Topic: unused orbitals
- Replies: 4
- Views: 148
Re: unused orbitals
It can stay a p orbital, as there is the hybridization sp2 which is used in molecular geometries with three regions of electron density--such as trigonal planar geometries.
- Sun Nov 24, 2019 11:36 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: t shape and see saw
- Replies: 6
- Views: 417
Re: t shape and see saw
Molecular geometries depend on the number of atoms bonded to the central atom, and the number of lone pairs that central atom has. Molecules which have 5 atoms bonded to the central atom, and 0 lone pairs, are of the geometry trigonal bipyramidal. Molecules which have 4 atoms bonded to the central a...
- Sun Nov 17, 2019 1:42 pm
- Forum: Sigma & Pi Bonds
- Topic: Test 2 Sigma and Pi bonds
- Replies: 5
- Views: 179
Re: Test 2 Sigma and Pi bonds
Yes, sigma and pi bonds will be on the exam. Dr. Lavelle discussed them very shortly at the end of Friday's lecture on 11/15/19. He will discuss them more on the upcoming Monday lecture on 11/18/19. Briefly: single bonds have a sigma bond; double bonds have one sigma bond and one pi bond; triple bon...
- Sun Nov 17, 2019 1:38 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Octahedral??
- Replies: 4
- Views: 648
Re: Octahedral??
This is the same as tetrahedrals. They are not called tetrahedrals because the molecule has four atoms, rather it is the mathematical term for the shape with 4 equal faces. It just happens that 4 atoms arrange themselves into the vertices of the tetrahedral
- Sun Nov 17, 2019 1:36 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Octahedral??
- Replies: 4
- Views: 648
Re: Octahedral??
The name octahedral refers to the shape that a six atom molecule makes. This is because the term is a geometric one, as octahedral refers to the geometric shape hacing 8 faces, thus octa. However, the shape only has 6 vertices, which in a molecule is the 6 atoms.
- Sun Nov 17, 2019 1:33 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: This Week Test
- Replies: 12
- Views: 704
Re: This Week Test
Yes, this exam should also include intermolecular forces as well as the VSEPR model. Moreover, the first slide of Dr. Lavelle's lecture on Monday 11/18/19 will be on the exam. However, Dr. Lavelle noted that hybridization will not be on the exam.
- Sun Nov 17, 2019 1:31 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Strength of Repulsion
- Replies: 4
- Views: 310
Re: Strength of Repulsion
This is because lone pair electrons take up more volume with their electron clouds as they are only being held by one atom's nucleus. Bonding electrons are confined to a smaller volume as they feel the influence of two atoms' nuclei, confining them to a smaller space. Thus, it is not that lone pair ...
- Sun Nov 17, 2019 1:25 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Interactions
- Replies: 3
- Views: 111
Re: Interactions
Yes, that is the correct order of interaction strength, except that it is missing the ion-ion interaction which is the strongest interaction of all. And yes, Van Der Waal Forces also are called London Forces. However, Dr. Lavelle prefers if you call the interaction induced dipole-induced dipole inte...
- Sun Nov 10, 2019 9:08 pm
- Forum: Dipole Moments
- Topic: Dipole-Induced Dipole
- Replies: 2
- Views: 100
Re: Dipole-Induced Dipole
dipole - induced dipole interaction: One molecule has a permanent dipole This permanent dipole molecule is near another molecule that doesn't have a permanent dipole However, the molecule with a permanent dipole polarizes the other molecule, inducing a dipole in it, and forming an intermolecular int...
- Sun Nov 10, 2019 9:00 pm
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: polarizability v. polar power
- Replies: 1
- Views: 149
Re: polarizability v. polar power
It is important to distinguish between polarizing power and polarizability. Polarizing power is the ability of an atom to polarize another. Polarizability is the opposite: the ability of an atom to be polarized. Polarizability is similar to the trend of electronegativity. An atom is more polarizable...
- Sun Nov 10, 2019 8:59 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: Interaction Potential Energy
- Replies: 1
- Views: 80
Re: Interaction Potential Energy
Interaction potential energy is always negative because atoms always lose energy when forming bonds; they never gain energy. In other words, the energy of an atom without a bond is higher than that of the same atom with a bond. So, if you take the final energy of the atom with the bond and subtract ...
- Sun Nov 10, 2019 8:55 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: Hydrocarbons at room temperature
- Replies: 2
- Views: 210
Re: Hydrocarbons at room temperature
The length and shape of a hydrocarbon often affect its state of matter when at room temperature. When hydrocarbons have the same shape--particularly the rod shape--the longer hydrocarbons are those that are more solid while the shorter ones are more liquid and gaseous. When hydrocarbons have the sam...
- Sun Nov 10, 2019 8:45 pm
- Forum: Bond Lengths & Energies
- Topic: Interaction Potential Energy
- Replies: 2
- Views: 106
Re: Interaction Potential Energy
Interaction potential energy is always negative because atoms always lose energy when forming bonds; they never gain energy. In other words, the energy of an atom without a bond is higher than that of the same atom with a bond. So, if you take the final energy of the atom with the bond and subtract ...
- Sun Nov 10, 2019 8:42 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: Polarizability
- Replies: 3
- Views: 105
Re: Polarizability
It is important to distinguish between polarizing power and polarizability. Polarizing power is the ability of an atom to polarize another. Polarizability is the opposite: the ability of an atom to be polarized. Polarizability is similar to the trend of electronegativity. An atom is more polarizable...
- Sun Nov 10, 2019 8:30 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: Fluctuating Dipoles
- Replies: 5
- Views: 220
Re: Fluctuating Dipoles
Fluctuating dipoles becomes important when discussing induced dipole - induced dipole interactions. A simplification of the premise is that electrons in an atom are always moving; they are not static. Thus, in molecules, electrons are still moving around their atoms in, essentially, random motion. T...
- Sun Nov 03, 2019 10:01 pm
- Forum: Lewis Structures
- Topic: Drawing Lewis Structures
- Replies: 3
- Views: 143
Re: Drawing Lewis Structures
Here it is important to understand the difference between formal charge and charge. The charge relates to the entire molecule. For example the charge of H_{2}O is 0; the charge of the sulfate polyatomic ion is 2-. The formal charge then is a calculation tool used for single atoms in particular withi...
- Sun Nov 03, 2019 9:54 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Visualizing orbitals
- Replies: 1
- Views: 91
Re: Visualizing orbitals
The square of the atomic orbital function gives the probability of where the electron will be in that orbital.
So the orbital function describes the shape of the volume the electron can reside; the square of that function tells you how likely it is to be in each location within that volume.
So the orbital function describes the shape of the volume the electron can reside; the square of that function tells you how likely it is to be in each location within that volume.
- Sun Nov 03, 2019 9:51 pm
- Forum: Octet Exceptions
- Topic: Uhhh
- Replies: 3
- Views: 137
Re: Uhhh
There are two kinds of octet exceptions: atoms which exceed the octet and those which fall short of an octet. The atoms which exceed the octet are those in columns 15 through 17 and in rows 3 or below. The most common we will use are Phosphorus, Sulfur, and Chlorine. This is because these atoms can ...
- Sun Nov 03, 2019 9:43 pm
- Forum: Lewis Structures
- Topic: Showing work for valence electrons
- Replies: 3
- Views: 164
Re: Showing work for valence electrons
It may just be helpful to quickly show the addition of valence electrons to show the calculation for the total number of valence electrons. It will help you keep track and also make it easier for the grader.
- Sun Nov 03, 2019 9:41 pm
- Forum: Lewis Structures
- Topic: "Most favorable" Diagram
- Replies: 4
- Views: 380
Re: "Most favorable" Diagram
When the question asks to draw the "most favorable" lewis structure, it generally means just the correct one if it doesn't have resonance. However, in some cases, a molecule can have resonance where one structure is preferred over another. This has to do with the formal charge. With some m...
- Sun Nov 03, 2019 9:37 pm
- Forum: Bond Lengths & Energies
- Topic: Bond Strength and Electronegativity
- Replies: 3
- Views: 239
Re: Bond Strength and Electronegativity
The relationship between bond strength and electronegativity is an indirect one to understand: 1.) Electronegativity refers to the tendency of an atom to attract and accept an electron. 2.) A bond is when two atoms share at least a pair of electrons. Bond strength is affected by two principles: the ...
- Sat Oct 26, 2019 2:45 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: Quantum number m
- Replies: 3
- Views: 181
Re: Quantum number m
There are four quantum numbers: n, l, m_{l} , and m_{s} These four quantum numbers explain the individual properties of every electron possible in an atom. Moreover, in one atom, two electrons cannot have the same values for all four quantum numbers. Pertaining to the quantum number "m", t...
- Sat Oct 26, 2019 2:36 pm
- Forum: Trends in The Periodic Table
- Topic: Electronegativity vs Electron Affinity
- Replies: 6
- Views: 264
Re: Electronegativity vs Electron Affinity
Electron affinity and electronegativity describe similar processes in different ways. Electron affinity is the energy released when an atom--in the gaseous phase--gains an electron This energy can be directly measured Electronegativity is the "ability" of an atom to attract electrons This ...
- Sat Oct 26, 2019 2:15 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Special elements
- Replies: 2
- Views: 102
Re: Special elements
There are two exceptions: Chromium: Which should be [Ar] 3d^{4} 4d^{2} according to the systematic pattern normally used However, it is actually [Ar] 3d^{5} 4d^{1} Copper Which should be [Ar] 3d^{9} 4d^{2} according to the systematic pattern normally used However, it is actually [Ar] 3d^{10} 4d^{1} ...
- Sat Oct 26, 2019 2:10 pm
- Forum: Lewis Structures
- Topic: Shape of bonds?
- Replies: 2
- Views: 99
Re: Shape of bonds?
We will be discussing the shape of molecules (the VSEPR model) in a future lecture. As of week 4, we have not discussed this and thus you should not be worried about the three-dimensional structure of molecules.
- Sat Oct 26, 2019 2:07 pm
- Forum: Photoelectric Effect
- Topic: Rydberg Formula
- Replies: 1
- Views: 168
Re: Rydberg Formula
The Rydberg Formula Dr. Lavelle taught us is E_{n}=-\frac{hR}{n^{2}} This equation gives us the energy of an electron at a particular energy level ( E_{n} ) given that we know the energy level the electron is at (n), the plank constant (h) and the Rydberg constant (R). Thus, the solution of this equ...
- Sat Oct 19, 2019 12:19 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Electron configuration of Tungsten (W) compared to Chromium (Cr) [ENDORSED]
- Replies: 2
- Views: 5222
Re: Electron configuration of Tungsten (W) compared to Chromium (Cr) [ENDORSED]
The reason for Tungsten not following the exception rule that Chromium does is not needed for our course. We only need to know the electron configurations for the first row of the d block, since this is a life science chemistry course.
- Sat Oct 19, 2019 12:11 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: building up principle
- Replies: 5
- Views: 158
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?
- Sat Oct 19, 2019 12:08 pm
- Forum: Properties of Light
- Topic: Quantum equations
- Replies: 5
- Views: 196
Re: Quantum equations
In all of the equations used for the Quantum Mechanics unit, distance must be converted to meters. After a calculation is done, the problem may ask for a unit different than meters, such as Angstrom or nanometers. Only convert to these units after the calculation is complete, never before.
- Sat Oct 19, 2019 12:03 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: HW 1B.27
- Replies: 2
- Views: 136
Re: HW 1B.27
In an uncertainty problem where they give a "variable" ± "a value", the uncertainty is twice that "value". This is easier to understand by example: If a problem describes the velocity of an object as 5.00 m/s ± 1.00, the uncertainty would be double the value of 1.00, eq...
- Sat Oct 19, 2019 11:49 am
- Forum: *Shrodinger Equation
- Topic: Concepts of Schrodinger equation
- Replies: 3
- Views: 147
Re: Concepts of Schrodinger equation
An extra note which is important to keep in mind is that the "Wave Function" is a mathematical equation. That is why it is also called the Schrodinger Equation. Once you think of it in that way, it becomes very easy to contextualize all of the chemistry terms related to it. We will not lea...
- Sat Oct 12, 2019 10:31 am
- Forum: Properties of Electrons
- Topic: De Broglie Problems
- Replies: 4
- Views: 118
Re: De Broglie Problems
Aa Dr. Lavelle discussed in class, traditionally, wavelengths smaller than 10 ^ -15 meters are considered to have unmeasurable wave-like properties. Instead, they would only have particle-like properties.
- Sat Oct 12, 2019 10:29 am
- Forum: Properties of Light
- Topic: Circular Standing Waves and electrons
- Replies: 2
- Views: 175
Re: Circular Standing Waves and electrons
The wave model of electrons properly predicts energy levels if electrons are modeled as circular standing waves around the nucleus. This is because all waves--circular or not--have differing energies. However, for a circular standing wave to exist, it must be continuous and have no discontinuities s...
- Sat Oct 12, 2019 10:23 am
- Forum: Einstein Equation
- Topic: Diffraction patterns
- Replies: 2
- Views: 155
Re: Diffraction patterns
To understand diffraction patterns, one must first recognize that there are two models possible for understanding the motion of an object relevant to chemistry: the particle model and the wave model. The particle model interprets objects as solid objects which have a defined location in space. The w...
- Sat Oct 12, 2019 10:14 am
- Forum: Photoelectric Effect
- Topic: Energy classification
- Replies: 2
- Views: 107
Re: Energy classification
Yes, this energy is called by two names: "threshold energy" and the "work function". The reason for this energy being called the "threshold energy" is because that is the exact energy that marks the boundary for an atom to eject its electron or not. At the threshold ene...
- Thu Oct 03, 2019 8:50 am
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Formula Units
- Replies: 6
- Views: 489
Re: Formula Units
Formula units are different from molecules in that all atoms in an ionic compound have formed atomic bonds with other atoms, to form a lattice. In this way, ionic compounds are not groups of moleculas which are associeated with one another through intermolecular bonds. Rather, they are one coherent ...