Search found 118 matches
- Tue Mar 10, 2020 11:55 pm
- Forum: Environment, Ozone, CFCs
- Topic: stoichiometric coefficients
- Replies: 19
- Views: 1380
Re: stoichiometric coefficients
Either way works, but the reaction is written with the fraction so that the coefficient of the product is one.
- Tue Mar 10, 2020 11:52 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Difference between catalyst and intermediate
- Replies: 9
- Views: 623
Re: Difference between catalyst and intermediate
A catalyst is present in the beginning, while an intermediate is only present in the steps in the middle of the reaction process.
- Tue Mar 10, 2020 11:41 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Molecularity
- Replies: 12
- Views: 748
Re: Molecularity
Molecularity is the amount of species that interact with each other as reactants.
- Tue Mar 10, 2020 5:17 pm
- Forum: Administrative Questions and Class Announcements
- Topic: ENDGAME Review Session
- Replies: 71
- Views: 5399
Re: ENDGAME Review Session
Will there be a livestream option for the review session with classes being cancelled?
- Mon Mar 09, 2020 3:59 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Catalysts and Equilibrium
- Replies: 2
- Views: 186
Catalysts and Equilibrium
Why doesn't a catalyst affect the equilibrium position of a reaction?
- Sun Mar 08, 2020 6:01 pm
- Forum: General Rate Laws
- Topic: slow step
- Replies: 9
- Views: 597
Re: slow step
For all conditions, the slowest step determines the rate of the reaction, because the reaction can only proceed as fast as the slowest process.
- Sun Mar 08, 2020 5:37 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Rate Laws
- Replies: 3
- Views: 256
Re: Rate Laws
No, since the concentration is so high, it stays almost exactly the same, so it does not need to be included.
- Sun Mar 08, 2020 5:35 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: catalyst
- Replies: 4
- Views: 397
Re: catalyst
A catalyst changes the intermediates of a reaction so that the mechanism has a lower activation energy.
- Sun Mar 08, 2020 5:34 pm
- Forum: General Rate Laws
- Topic: integrated rate laws
- Replies: 7
- Views: 429
Re: integrated rate laws
An integrated rate law shows the concentration of a substance at a certain point in time. The rate law only shows the change in concentration.
- Sun Mar 08, 2020 5:30 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Reduced/Oxidized based on Ecell
- Replies: 6
- Views: 400
Re: Reduced/Oxidized based on Ecell
If the Ecell is the same, the substance that is oxidized/reduced will depend on the concentration. The substance in lower concentration will be oxidized, while the substance present in higher concentration will usually be reduced.
- Sun Mar 08, 2020 5:28 pm
- Forum: Calculating Work of Expansion
- Topic: Irreversible and Reversible Expanision
- Replies: 9
- Views: 624
Re: Irreversible and Reversible Expanision
In addition to what has already been said, for a reversible expansion, there is heat transfer to maintain the temperature. However, for an irreversible expansion, there is no heat transfer because the change occurs too quickly.
- Sun Mar 08, 2020 2:43 pm
- Forum: Zero Order Reactions
- Topic: third order
- Replies: 11
- Views: 1131
Re: third order
No, since third order reactions are very uncommon, they are not covered in our curriculum.
- Sun Mar 08, 2020 2:42 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: activation energy/ energy barrier
- Replies: 6
- Views: 427
Re: activation energy/ energy barrier
The activation energy is the amount of energy that is required initially for a reaction to occur. This value is important because it determines how likely a reaction is to occur, and therefore, how long it will take to occur.
- Mon Mar 02, 2020 11:37 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: 5J.15
- Replies: 1
- Views: 138
Re: 5J.15
Since (delta)G in the Appendix is only for 25 C, we must calculate (delta)G using H and S to find it at 150 C.
- Mon Mar 02, 2020 11:33 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: 6.43
- Replies: 3
- Views: 261
Re: 6.43
It is Ecell because this value depends on the reaction quotient.
- Mon Mar 02, 2020 11:32 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: HW 6.57
- Replies: 6
- Views: 483
Re: HW 6.57
When you add the half reactions together, you get a coefficient of 2 in front of every reactant and product. In the dissociation reaction, the stoichiometric coefficients are 1. Thus, in order for the Ka to correspond to a stoichiometric coefficient of 1, we must square root the K value.
- Sat Feb 29, 2020 10:04 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell Potential vs Standard Cell Potential
- Replies: 1
- Views: 150
Cell Potential vs Standard Cell Potential
What's the difference between cell potential and standard cell potential?
- Sat Feb 29, 2020 8:10 pm
- Forum: Balancing Redox Reactions
- Topic: Acidic and Basic solutions
- Replies: 11
- Views: 647
Re: Acidic and Basic solutions
When there is an acidic solution, you use H+ to balance out the hydrogen atoms. On the other hand, for a basic solution, you use OH- to balance out the hydrogen atoms.
- Sat Feb 29, 2020 5:45 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gibbs Free Energy Relation to Q
- Replies: 1
- Views: 167
Gibbs Free Energy Relation to Q
Could someone explain conceptually why the gibbs free energy depends on the reaction quotient Q?
- Sun Feb 23, 2020 5:40 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Calculating Cell Potentials
- Replies: 2
- Views: 194
Calculating Cell Potentials
When we calculate cell potential, do we always subtract the potential of the right cell by that of the left cell?
- Sun Feb 23, 2020 5:38 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: how to get n in equation
- Replies: 8
- Views: 488
Re: how to get n in equation
Look at the balanced half reactions and determine how many electrons are being transferred in the redox reaction.
- Sun Feb 23, 2020 5:37 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Concentration and cell potential
- Replies: 6
- Views: 380
Re: Concentration and cell potential
Another way to see cell potential is the potential of the cell to do work. If there is a greater difference between the concentrations of the reactants in a spontaneous reaction, it will be able to do more work.
- Sun Feb 23, 2020 5:32 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Platinum Cell Diagram
- Replies: 2
- Views: 172
Re: Platinum Cell Diagram
Although iodine is a solid, it is not a conductor. Thus, we need to put a conducting metal (platinum) in order for the reaction to occur.
- Sun Feb 23, 2020 5:29 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: neg vs pos
- Replies: 9
- Views: 633
Re: neg vs pos
If the voltage of the cell is negative, then the cell does not have a spontaneous reaction in the specified direction.
- Sun Feb 23, 2020 5:27 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: chemistry community posts
- Replies: 12
- Views: 583
Re: chemistry community posts
The posts are usually counted at the end of the quarter. You should do 5/week to stay on track, but as long as you have 50 by the end of the quarter and you didn't do a bunch of them at the same time, you'll be good.
- Sun Feb 23, 2020 5:25 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Salt Bridge
- Replies: 9
- Views: 611
Re: Salt Bridge
The salt bridge ensures that the solution in the anode and the cathode stays neutral. Since electrons are being transferred as the redox reaction occurs, the charges of the anode and the cathode are changing. The salt bridge dispenses ions as they change to ensure that there is no polarization that ...
- Wed Feb 12, 2020 1:45 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Entropy Change over the Course of Thermodynamic Processes
- Replies: 3
- Views: 273
Re: Entropy Change over the Course of Thermodynamic Processes
The change in entropy is zero because the final state of the system is the same as the initial state. Since entropy is a state function and there is no overall change in the conditions, the entropy does not change.
- Wed Feb 12, 2020 1:41 pm
- Forum: Calculating Work of Expansion
- Topic: A system doing no work
- Replies: 4
- Views: 232
Re: A system doing no work
So far in the course, the only form of work we have learned is the system expanding and pushing against the surroundings.
- Wed Feb 12, 2020 1:35 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Buffer Solution
- Replies: 4
- Views: 477
Re: Buffer Solution
I also got pH = 4.545!
- Wed Feb 12, 2020 1:14 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Difference between equations
- Replies: 2
- Views: 262
Re: Difference between equations
nRln(V2/V1) only works when the temperature is constant because it is derived from the equation (delta)S = q/T, which assumes that temperature is constant.
- Wed Feb 12, 2020 1:03 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Temperature Changes Along Irreversible Pathway
- Replies: 3
- Views: 198
Re: Temperature Changes Along Irreversible Pathway
During a reversible expansion, the change in volume is slow enough that the temperature can stay constant. However, in an irreversible change, the process occurs too quickly to keep the temperature constant.
- Wed Feb 12, 2020 12:40 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Acid and [H3O] Midterm Q
- Replies: 3
- Views: 207
Re: Acid and [H3O] Midterm Q
Since HA is a weak acid, it will not completely dissociate into H3O+ ions. This means that the initial concentration of HA will not be the same as the final concentration of H3O+ ions.
- Mon Feb 10, 2020 9:13 pm
- Forum: Calculating Work of Expansion
- Topic: calculating work of a reversible reaction
- Replies: 5
- Views: 354
Re: calculating work of a reversible reaction
Work will be negative if the volume is increasing. You should always keep the negative if you are calculating the work being done on the system.
- Mon Feb 10, 2020 8:47 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Delta S sub m
- Replies: 2
- Views: 198
Delta S sub m
I noticed one of the practice problems wrote entropy as ΔSm. Does anyone know what the "m" stands for in this term?
- Sun Feb 09, 2020 10:55 am
- 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: Residual Entropy
- Replies: 5
- Views: 83
Residual Entropy
What is residual entropy and how does it arise?
- Wed Feb 05, 2020 9:50 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: Microstates
- Replies: 7
- Views: 156
Re: Microstates
A microstate is a possible arrangement of molecules in a given space. If there are more degenerate microstates, meaning that they all have the same energy, then the entropy is higher.
- Wed Feb 05, 2020 9:47 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Heat capacity
- Replies: 4
- Views: 94
Re: Heat capacity
If C is not given in the problem, you can use the equation Cv = (delta)U/(delta)t or Cp = (delta)H/(delta)T.
- Tue Feb 04, 2020 1:39 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Relation between Entropy and Enthalpy
- Replies: 1
- Views: 66
Relation between Entropy and Enthalpy
I understand how the equation (delta)S = (delta)H/T is mathematically derived, but I don't understand conceptually why it makes sense that change in enthalpy, temperature, and change in entropy can be related to each other. Does anyone have an explanation?
- Thu Jan 30, 2020 10:00 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Hess's Law vs. Standard Enthalpies of Formation
- Replies: 5
- Views: 210
Re: Hess's Law vs. Standard Enthalpies of Formation
If multiple reactions are given, the Hess's Law should be applied. If one reaction and the standard enthalpies of formation are given, then you should subtract the standard enthalpies of formation of the products by that of the reactants.
- Thu Jan 30, 2020 9:54 pm
- Forum: Phase Changes & Related Calculations
- Topic: Units
- Replies: 16
- Views: 746
Re: Units
Since this chapter mostly deals with changes in temperatures, it does not matter whether Kelvins or Celsius are used because they are scaled the same.
- Thu Jan 30, 2020 9:51 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Closed vs isolated systems
- Replies: 24
- Views: 781
Re: Closed vs isolated systems
Closed systems can exchange energy with their surroundings. On the other hand, isolated systems cannot exchange energy with its surroundings. This means that closed systems can transfer heat, but isolated systems cannot.
- Thu Jan 30, 2020 9:49 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Reversible Process
- Replies: 1
- Views: 73
Reversible Process
What is the meaning of a reversible process and what are the implications of it having an infinitesimal changes?
- Thu Jan 30, 2020 9:38 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Heat Capacity
- Replies: 2
- Views: 133
Re: Heat Capacity
The standard enthalpy of formation should be multiplied by the amount of moles reacted.
- Sat Jan 25, 2020 6:39 pm
- Forum: Acidity & Basicity Constants and The Conjugate Seesaw
- Topic: Water Properties
- Replies: 5
- Views: 328
Re: Water Properties
In addition to what was already said, an amphiprotic substance is always amphoteric. However, an amphoteric compound is not always amphiprotic.
- Sat Jan 25, 2020 6:33 pm
- Forum: Phase Changes & Related Calculations
- Topic: Steam v. liquid
- Replies: 7
- Views: 244
Re: Steam v. liquid
Yes, because steam must lose energy to convert into a liquid when it condenses on your skin. This is in addition to the heat released by the temperature change in the water when it touches your skin, which would be the only source of heat for a liquid burn.
- Sat Jan 25, 2020 6:31 pm
- Forum: Ideal Gases
- Topic: final exam pickup
- Replies: 10
- Views: 431
Re: final exam pickup
Pickup is at the mailing center in Young Hall. Be sure to bring your BruinCard or some form of ID when you pick it up.
- Sat Jan 25, 2020 6:29 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Standard Enthalpy of formation
- Replies: 4
- Views: 212
Re: Standard Enthalpy of formation
The SI unit is kJ/mol.
- Sat Jan 25, 2020 6:28 pm
- Forum: Phase Changes & Related Calculations
- Topic: Endothermic and Exothermic
- Replies: 13
- Views: 479
Re: Endothermic and Exothermic
In an endothermic reaction, the reaction removes heat from the surroundings. In an exothermic reaction, the reaction adds heat to the surroundings. However, all reactions take some heat to begin (activation energy), so the previous statements are based on net changes.
- Mon Jan 20, 2020 4:48 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: 6D 15
- Replies: 1
- Views: 98
Re: 6D 15
Since Al(3+) is a small, highly charged cation, it can act as an acid when it is a hydrate in the form Al(H2O)63+. The Ka value for this can be found in the text.
- Mon Jan 20, 2020 4:27 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Buffer Practice Problems
- Replies: 1
- Views: 191
Buffer Practice Problems
Has anyone seen homework problems that have to do with buffers? Also, will it be on the test this week?
- Sun Jan 19, 2020 1:00 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Quick way
- Replies: 7
- Views: 328
Re: Quick way
When the pressure increases, the reaction will shift to the side that produces less moles of gas. Conversely, when the pressure decreases, the reaction will shift to the side that produces more moles of gas.
- Sun Jan 19, 2020 12:55 pm
- Forum: Ideal Gases
- Topic: R Constant
- Replies: 7
- Views: 213
Re: R Constant
You should use the R constant that has units that cancel out with the other units in the equation. For example, in PV=nRT, we use 0.08206 (L*atm)/(mol*K) because it cancels with the pressure, volume, moles, and temperature.
- Sun Jan 19, 2020 12:52 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Endothermic vs. exothermic
- Replies: 5
- Views: 191
Re: Endothermic vs. exothermic
The equilibrium will shift towards the right. This is because endothermic reactions take up heat, so forming more products would lessen the effect of the increase in temperature.
- Sun Jan 19, 2020 12:50 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: 5% rule
- Replies: 10
- Views: 423
Re: 5% rule
If the percent deprotonation is less that 5%, then when we calculate equilibrium concentrations, we can ignore the x values relative to the initial concentration because it is not significant.
- Sun Jan 19, 2020 12:48 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Q < K
- Replies: 16
- Views: 763
Re: Q < K
Yes, because in a chemical equation, the products are on the right side. Thus, a shift to the right means more products will form.
- Sat Jan 11, 2020 1:09 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Significant Figures
- Replies: 8
- Views: 357
Re: Significant Figures
Both the K constant and the initial concentrations should be used when calculating sig figs because they are both used in the overall calculation.
- Sat Jan 11, 2020 1:05 pm
- Forum: Ideal Gases
- Topic: The Difference between Q and Kc [ENDORSED]
- Replies: 18
- Views: 8429
Re: The Difference between Q and Kc [ENDORSED]
Kc is calculated when the reaction is at equilibrium. On the other hand, Q is calculated when the reaction is at any other state.
- Fri Jan 10, 2020 9:36 pm
- Forum: Ideal Gases
- Topic: K value
- Replies: 14
- Views: 1029
Re: K value
If the K value is large, the reaction favors the products. On the other hand, if the K value is small, the reaction favors the reactants.
- Fri Jan 10, 2020 9:34 pm
- Forum: Ideal Gases
- Topic: Ideal Gas Law
- Replies: 6
- Views: 166
Re: Ideal Gas Law
The ideal gas law can be used to solve for pressure, volume, temperature, and amount of moles. In class, we also used it to convert from partial pressure to concentration and vice versa.
- Fri Jan 10, 2020 9:31 pm
- Forum: Ideal Gases
- Topic: ICE table
- Replies: 7
- Views: 805
Re: ICE table
Maggie Eberhardt - 2H wrote:Sorry if this is a stupid question, but when/why do we use ICE table?
We use an ICE table when we are given the initial concentration and want to determine the final concentration values after equilibrium is reached.
- Thu Dec 05, 2019 10:22 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: 6B1
- Replies: 2
- Views: 192
Re: 6B1
Since pH uses a log scale, the initial molar concentration does not matter. To answer this problem, you can use any arbitrary value for the initial molarity and get the same answer.
- Mon Dec 02, 2019 8:59 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Carbonate Ion
- Replies: 2
- Views: 110
Carbonate Ion
Question 9C.5 part b asks how many places (CO3)2- can bind to a single metal center. The answer says that it can be mono or bidentate. Why can it be both?
- Sun Dec 01, 2019 12:42 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: pH Scale is broken?
- Replies: 6
- Views: 521
Re: pH Scale is broken?
pH values are not solely confined to the values 0-14. However, most solutions fall within this range.
- Fri Nov 29, 2019 6:43 pm
- Forum: Acidity & Basicity Constants and The Conjugate Seesaw
- Topic: triple equal sign
- Replies: 2
- Views: 556
Re: triple equal sign
This is likely not a typo, because the triple equal sign means "is equivalent to," which is more specific than "is equal to."
- Fri Nov 29, 2019 6:41 pm
- Forum: General Science Questions
- Topic: hydrogen vs hydronium
- Replies: 5
- Views: 235
Re: hydrogen vs hydronium
The hydrogen ion is often used in place of hydronium to simplify things. However, you should know that the hydronium ion better represents what is actually seen.
- Sun Nov 24, 2019 11:24 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Cisplatin and Transplatin
- Replies: 2
- Views: 151
Re: Cisplatin and Transplatin
Cisplatin stops DNA replication by bonding to two exposed guanines. This prevents the enzymes from replicating the DNA. Transplatin does not stop DNA replication because its shape only allows it to bind to one guanine. This bond is not strong enough to prevent replication.
- Sun Nov 24, 2019 11:18 pm
- Forum: Bronsted Acids & Bases
- Topic: Bronsted vs Lewis acids
- Replies: 5
- Views: 358
Re: Bronsted vs Lewis acids
There isn't a clear definition for acids, just different theories. Thus, we have different classifications such as Bronsted and Lewis.
- Sun Nov 24, 2019 11:08 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: EDTA
- Replies: 1
- Views: 170
Re: EDTA
EDTA can remove harmful metals such as lead from the body because it is able to bind to the metals.
- Tue Nov 19, 2019 2:53 pm
- Forum: Dipole Moments
- Topic: Polar or nonpolar
- Replies: 8
- Views: 521
Re: Polar or nonpolar
O2 is nonpolar because there is no difference in electronegativity, and therefore, no dipole moment between the atoms.
- Tue Nov 19, 2019 2:51 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: bent v. angular
- Replies: 27
- Views: 1348
Re: bent v. angular
Bent and angular mean the same thing. There are also several names for other structures, such as seesaw (disphenoidal).
- Tue Nov 19, 2019 2:50 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bond Angles
- Replies: 4
- Views: 211
Re: Bond Angles
The bond angle will be less than expected if there is a lone pair present, because the electron-electron repulsions will push the bonds closer together.
- Tue Nov 19, 2019 2:47 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Linear Shape
- Replies: 6
- Views: 341
Re: Linear Shape
A linear bond can be polar if the dipole moments are unequal, and therefore, do not cancel out.
- Tue Nov 19, 2019 2:41 pm
- Forum: Hybridization
- Topic: test 2
- Replies: 6
- Views: 338
Re: test 2
Hybridization will not be tested on Test 2. Only content from after the midterm to sigma and pi bonds will be tested.
- Mon Nov 18, 2019 1:12 pm
- Forum: Lewis Structures
- Topic: Oxygen
- Replies: 9
- Views: 708
Re: Oxygen
Oxygen can have all types of bonds, but it usually does not have triple bonds because the formal charge of oxygen would be more likely to have a nonzero value. This is because oxygen has 6 valence electrons and a triple bond would cause the formal charge to usually be 1.
- Mon Nov 18, 2019 1:07 pm
- Forum: Octet Exceptions
- Topic: Antioxidants
- Replies: 9
- Views: 648
Re: Antioxidants
Radicals are highly reactive because they have one unpaired electron. Antioxidants prevent them from reacting by donating an electron to make an electron pair.
- Mon Nov 18, 2019 1:03 pm
- Forum: Student Social/Study Group
- Topic: Test 2
- Replies: 5
- Views: 302
Re: Test 2
Only sigma and pi bonds from today's lecture will be covered on Test 2.
- Mon Nov 18, 2019 1:02 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: AXE notation
- Replies: 10
- Views: 615
Re: AXE notation
A is the central atom, X is the amount of bonded atoms, and E is the amount of lone pair electrons.
- Mon Nov 18, 2019 1:00 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Why is SF4 Polar?
- Replies: 6
- Views: 708
Re: Why is SF4 Polar?
Since the S--F bond has a dipole moment and the seesaw shape does not allow the dipole moments to cancel out, the molecule is polar. If all the bonds were arranged symmetrically, in a tetrahedral shape, for example, the molecule would not be polar.
- Mon Nov 18, 2019 12:57 pm
- Forum: Bond Lengths & Energies
- Topic: Curve
- Replies: 4
- Views: 396
Re: Curve
There's no curve for the midterm, but if the average grade is low enough, there will be a curve applied to the final grade.
- Sat Nov 16, 2019 2:36 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Acids and Bases
- Replies: 4
- Views: 189
Re: Acids and Bases
I think since that was covered before the midterm, we will not need to know how to identify acids and bases for test #2.
- Sat Nov 16, 2019 2:33 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Sulfite Ion example in class
- Replies: 6
- Views: 435
Re: Sulfite Ion example in class
The lone pairs in the sulfite ion cause the bond angles to be slightly smaller because the electron-electron repulsion pushes the bonds closer together.
- Sat Nov 16, 2019 2:32 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. Dipole-Induced Dipole
- Replies: 4
- Views: 570
Re: Dipole-Dipole vs. Dipole-Induced Dipole
A permanent dipole is caused by a difference in electronegativity. An induced dipole is caused by a charged atom or dipole that pulls electrons in one side, which causes a temporary dipole.
- Sat Nov 16, 2019 2:29 pm
- Forum: Dipole Moments
- Topic: Hydrogen bonds
- Replies: 17
- Views: 678
Re: Hydrogen bonds
Hydrogen bonds can only form with N, O, and F because they are the only elements that have a high enough electronegativity to create a strong dipole moment.
- Sat Nov 16, 2019 2:28 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: Strength of bonds
- Replies: 3
- Views: 156
Re: Strength of bonds
No, we do not need to calculate the strength of bonds. However, we should be able to recognize trends in bond lengths.
- Sat Nov 16, 2019 2:27 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: All VSEPR structures or just ones from class?
- Replies: 11
- Views: 571
Re: All VSEPR structures or just ones from class?
I think all of them have to be memorized. He just demonstrated how to determine the shapes of a couple molecules in class just as an example.
- Sat Nov 16, 2019 2:25 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: VSPER Formula for Compounds with No Lone Pairs
- Replies: 4
- Views: 256
Re: VSPER Formula for Compounds with No Lone Pairs
The VSPER formula would be AX4, since there is one central atom and four bonded atoms. The E will not be included since there are no lone pair electrons.
- Wed Nov 06, 2019 1:07 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Equation Sheet
- Replies: 2
- Views: 177
Re: Equation Sheet
Yes, on previous midterms there was an equation/constant sheet and periodic table attached to the back.
- Wed Nov 06, 2019 1:01 pm
- Forum: Lewis Structures
- Topic: Expanded Octets
- Replies: 6
- Views: 458
Re: Expanded Octets
Expanded octets would be used if it's clear that there is more than 4 atoms bonded to the central atom (ex: XeF5). Also, the octet can be expanded if the formal charge favors it in the lewis structure.
- Wed Nov 06, 2019 12:51 pm
- Forum: Ionic & Covalent Bonds
- Topic: C, N, O, and F
- Replies: 13
- Views: 576
Re: C, N, O, and F
There are some exceptions to the octet rule for these atoms. For example, CH3 is a radical, so it only has seven electrons around it, which breaks the octet rule.
- Wed Nov 06, 2019 12:48 pm
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: smaller cations
- Replies: 3
- Views: 242
Re: smaller cations
I'm assuming if you're asked to find the smallest cation, it is given that all the cations have the same amount of valence electrons. In this case, the smallest cation would have the highest amount of protons because this would mean the nucleus has a stronger pull on the electrons.
- Wed Nov 06, 2019 12:44 pm
- Forum: Lewis Structures
- Topic: Odd Number of V e-
- Replies: 3
- Views: 209
Re: Odd Number of V e-
You would need to calculate the formal charges of the atoms and add the single electron to the atom that would make all of the formal charges closest to zero.
- Sat Nov 02, 2019 1:54 pm
- Forum: Ionic & Covalent Bonds
- Topic: Ionic/Covalent
- Replies: 6
- Views: 171
Re: Ionic/Covalent
An ionic compound has at least two atoms. Even in the atom that donated an electron, the nucleus still exerts a small attractive force on the electrons of the other atom(s). This causes them to be pulled slightly in one direction, which means they are slightly covalent.
- Sat Nov 02, 2019 1:50 pm
- Forum: Resonance Structures
- Topic: Delocalization
- Replies: 4
- Views: 146
Re: Delocalization
Delocalization also occurs in other molecules, such as metals. However, as far as what we have learned in class, delocalization only applies to resonance structures.
- Wed Oct 30, 2019 6:13 pm
- Forum: Ionic & Covalent Bonds
- Topic: Ionic Bonds
- Replies: 6
- Views: 316
Re: Ionic Bonds
Yes, because if there is a substantial difference in electronegativity, one element is more likely to give up electrons, while the other element is likely to take electrons.
- Wed Oct 30, 2019 6:07 pm
- Forum: Trends in The Periodic Table
- Topic: Electron Affinity
- Replies: 8
- Views: 229
Re: Electron Affinity
Electron affinity is not as periodic as ionization energy. Thus, although electron affinity tends to increase going right and up, there are many exceptions to this.
- Wed Oct 30, 2019 6:05 pm
- Forum: Octet Exceptions
- Topic: Radicals
- Replies: 9
- Views: 302
Re: Radicals
To identify a radical, you usually have to look at the molecule's lewis structure and determine if there is an unpaired electron. If so, the molecule would be a radical.
- Thu Oct 24, 2019 2:46 pm
- Forum: Properties of Electrons
- Topic: Anions and Cations
- Replies: 4
- Views: 168
Re: Anions and Cations
If we are considering the anions and cations of one element, then the anion should be larger than the cation. This is because the anion will have more electrons, which creates more electron repulsion within the atom and increases the size of the electron cloud.
- Thu Oct 24, 2019 2:43 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Energy of spdf orbitals
- Replies: 11
- Views: 344
Re: Energy of spdf orbitals
As "l" (the number corresponding to the orbital) increases, the orbitals become increasingly less likely to penetrate the nucleus. Since the electrons spend more time further from the nucleus as l increases, they also experience more repulsion from other electrons. This means that the ener...
- Tue Oct 22, 2019 1:48 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: Frequency
- Replies: 15
- Views: 684
Re: Frequency
ATingin_3I wrote:Also speaking of frequency, is frequency always measured in terms of Hz?
The SI unit for frequency is Hz (s^-1). However, 1 divided by any unit of time can be used to measure frequency (ex: 1/hr). These are often not seen though because it is impractical for chemistry.
- Tue Oct 22, 2019 1:32 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Spin Magnetic Quantum #
- Replies: 6
- Views: 505
Re: Spin Magnetic Quantum #
There are only two possibilities for the spin direction of an atom: upwards and downwards. Because of this, there are also only two possible spin magnetic quantum numbers. I believe the numbers +1/2 and -1/2 were chosen somewhat arbitrarily.