Search found 116 matches
- Thu Mar 12, 2020 3:07 pm
- Forum: First Order Reactions
- Topic: equation derivations
- Replies: 9
- Views: 544
Re: equation derivations
I know that on a previous test they were asked to derive Van't Hoff's equation! But it is always useful to understand derivations so you know how to apply the equation.
- Thu Mar 12, 2020 3:03 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: salt bridge
- Replies: 11
- Views: 580
Re: salt bridge
I remember seeing somewhere that certain salts are not ideal for salt bridges... does anyone have an idea of what salts these include?
- Thu Mar 12, 2020 9:23 am
- Forum: *Enzyme Kinetics
- Topic: How to distinguish the intermediates and catalysts?
- Replies: 9
- Views: 775
Re: How to distinguish the intermediates and catalysts?
A catalyst is always regenerated!
- Wed Mar 11, 2020 2:49 pm
- Forum: Administrative Questions and Class Announcements
- Topic: ENDGAME Review Session
- Replies: 71
- Views: 5399
Re: ENDGAME Review Session
Thank you so much, Lyndon! Thank you for your dedication, patience, compassion, and hard work. I've been going to your workshops every week since 14A and I honestly could not have passed this class without you! Good luck in your future endeavors!
- Wed Mar 11, 2020 2:40 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: intergrated rate law
- Replies: 9
- Views: 601
Re: intergrated rate law
Even though both are given on the equation sheet I think it would be safe to know the derivations just in case anything is asked on the final.
- Wed Mar 11, 2020 2:37 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: kinetics
- Replies: 9
- Views: 604
Re: kinetics
The reaction will only happen if a catalyst is added and therefore the activation energy is lowered so the reaction can proceed
- Wed Mar 11, 2020 2:33 pm
- Forum: Balancing Redox Reactions
- Topic: Ecell values
- Replies: 12
- Views: 767
Re: Ecell values
The higher Ecell value is usually reduced!
- Wed Mar 11, 2020 2:24 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 always regenerated! So if you see it on the reactants and products side then it is a catalyst!
- Wed Mar 11, 2020 2:22 pm
- Forum: Administrative Questions and Class Announcements
- Topic: review session packets
- Replies: 4
- Views: 320
Re: review session packets
Yes! I believe they said answers will still be posted on chemistry community.
- Wed Mar 11, 2020 2:22 pm
- Forum: Zero Order Reactions
- Topic: straight line to fit data
- Replies: 5
- Views: 412
Re: straight line to fit data
Depending on the order of the reaction, the straight line (whether it is a positive or negative slope and the graph axis labels itself) will tell you the order of the reaction.
- Wed Mar 11, 2020 2:21 pm
- Forum: Second Order Reactions
- Topic: units
- Replies: 5
- Views: 607
Re: units
You can always solve for the units by knowing the rate reaction equation (rate=k[A]^2) and solving for k!
- Wed Mar 11, 2020 2:12 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Earthquake FINAL REVIEW SESSION
- Replies: 11
- Views: 1033
Re: Earthquake FINAL REVIEW SESSION
This is such a good idea and thank you for organizing this!
- Wed Mar 11, 2020 2:08 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: same equation?
- Replies: 5
- Views: 306
Re: same equation?
They are the exact same equations just the very last equation has been raised to the e.
- Tue Mar 10, 2020 7:31 pm
- Forum: Zero Order Reactions
- Topic: Graphs
- Replies: 4
- Views: 266
Re: Graphs
In addition, the y-intercept is the initial concentration!
- Sun Feb 23, 2020 10:19 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Nernst Equation
- Replies: 4
- Views: 248
Re: Nernst Equation
You use the Nernst equation to quantitatively determine the direction of the electron transfer under non-standard conditions. We use it when there's a dependence of cell potential on concentration.
- Sun Feb 23, 2020 4:02 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: 5.J.11b)
- Replies: 1
- Views: 241
Re: 5.J.11b)
I believe that because it is a Halogen, it's natural state is in X2 form (Cl2, F2, etc.) and therefore the reaction X2=2X is endothermic because it takes energy to pull the two atoms apart. Therefore we know the reaction will shift right towards the products when the temperature is increased.
- Sun Feb 23, 2020 4:00 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: 3rd law of thermodynamics
- Replies: 3
- Views: 312
Re: 3rd law of thermodynamics
Yes, I believe the substance has to be in a solid state. It must be a perfect crystalline to have zero disorder and therefore have zero entropy.
- Sun Feb 23, 2020 3:58 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: voltage
- Replies: 8
- Views: 364
Re: voltage
Voltage is the amount of energy being produced by the electrodes. It is the potential difference between two electrodes.
- Sun Feb 23, 2020 3:51 pm
- Forum: Balancing Redox Reactions
- Topic: Identifying Half Reactions
- Replies: 4
- Views: 323
Re: Identifying Half Reactions
MnO4- is being reduced because when we calculate the oxidation of state of Mn in this compound it is +7 (do this knowing that O is -2, multiplying it by 4 and knowing that the entire molecule has a charge of -1). But in the products, Mn has a charge of +2. This shows that Mn has gained 5 electrons a...
- Sun Feb 23, 2020 3:47 pm
- Forum: Balancing Redox Reactions
- Topic: spontaneous
- Replies: 15
- Views: 740
Re: spontaneous
When the standard reduction potential is positive that means the reduction is spontaneous!
- Sun Feb 23, 2020 3:45 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
You look at how many electrons are being transferred!
- Sat Feb 22, 2020 5:42 pm
- Forum: Balancing Redox Reactions
- Topic: Redox in Acidic/Basic Solutions
- Replies: 3
- Views: 235
Redox in Acidic/Basic Solutions
What does it mean when a redox reaction takes place in an acidic or basic solution? How do you balance a redox reaction when it takes place in an acidic or basic solution?
- Sat Feb 22, 2020 5:36 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Nernst Equation and Le Chatelier's Principle
- Replies: 3
- Views: 501
Re: Nernst Equation and Le Chatelier's Principle
Using Le Chatelier's principle which takes into account the increase in either products or reactants concentrations, the Ecell will either decrease or increase. If the concentrations of the reactants are increased, then Ecell will be greater than Estandard. If the concentrations of the products are ...
- Wed Feb 19, 2020 9:50 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Test 2 Material
- Replies: 16
- Views: 955
Re: Test 2 Material
As Dr. Lavelle mentioned at the end of the lecture today, the test will cover the second page of the Thermodynamics outline and all of the Electrochemistry Outline. But the test will NOT include Chemical Kinetics.
- Wed Feb 19, 2020 9:47 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Anode and Cathode position
- Replies: 5
- Views: 311
Re: Anode and Cathode position
It is conventional to put the anode on the left and the cathode on the right. That being said it would be smart to double-check that this is true in a problem or on a test (if possible) by seeing which is being reduced and which is being oxidized.
- Wed Feb 19, 2020 9:45 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Gibbs free energy
- Replies: 9
- Views: 665
Re: Gibbs free energy
G* means that all the substances are in their standard states
- Wed Feb 19, 2020 9:15 pm
- Forum: Balancing Redox Reactions
- Topic: Homework 6K.5 Part B
- Replies: 1
- Views: 93
Re: Homework 6K.5 Part B
Br is both the oxidizing and reducing agent.
We balance it assuming using the fact that it is an aqueous solution so H2O.
3Br2 + 6OH- --> 5Br- + BrO3- + 3H2O
We balance it assuming using the fact that it is an aqueous solution so H2O.
3Br2 + 6OH- --> 5Br- + BrO3- + 3H2O
- Wed Feb 19, 2020 9:00 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Dead Battery
- Replies: 6
- Views: 376
Re: Dead Battery
The absence of the flow of electrons or charge between the anode and cathode can also be solved by using a salt bridge!
- Tue Feb 18, 2020 1:31 am
- Forum: Balancing Redox Reactions
- Topic: Reduction vs. oxidation
- Replies: 29
- Views: 1072
Re: Reduction vs. oxidation
One thing my high school teacher taught me to remember oxidation/reduction is L.E.O (loses electrons oxidation) the lion goes G.E.R (gaining electrons reduction)! Hope this helps make memorization easier :)
- Thu Feb 06, 2020 12:43 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Textbook question 4A.13
- Replies: 5
- Views: 125
Re: Textbook question 4A.13
Qreaction=-Qcalorimeter and so that is why the answer is negative 1.19kJ!
- Sun Feb 02, 2020 5:57 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Variables
- Replies: 3
- Views: 112
Re: Variables
As someone else said I think it would be a good thing to familiarize yourself with the Constants and Equations sheet that's on Dr. Lavelle's website and it is likely that you will be able to deduce what each variable is!
- Sun Feb 02, 2020 5:09 pm
- Forum: Phase Changes & Related Calculations
- Topic: Liquid/Steam
- Replies: 3
- Views: 165
Liquid/Steam
Can someone explain to me why steam causes worse burns than boiling water? I know he went over it in great detail during lecture but I want to be sure that I have the concepts solidified.
- Sun Feb 02, 2020 4:59 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Calorimeter
- Replies: 5
- Views: 245
Re: Calorimeter
A bomb calorimeter is completely sealed and insulated, making it an isolated system. It maintains a constant volume.
A constant pressure calorimeter gives enthalpy values.
A constant pressure calorimeter gives enthalpy values.
- Sun Feb 02, 2020 4:55 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Enthalpy units
- Replies: 5
- Views: 272
Re: Enthalpy units
It should be in terms of Joules whether that is J or kJ. It can also be in J/mol or kJ/mol depending on the context.
- Sun Feb 02, 2020 4:54 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: thermochemistry equations
- Replies: 5
- Views: 233
Re: thermochemistry equations
Make sure to familiarize yourself with the Constants and Equations sheet on Dr. Lavelle's website, therefore, you know what you should and shouldn't memorize!
- Sun Jan 26, 2020 8:10 pm
- Forum: Phase Changes & Related Calculations
- Topic: Standard State
- Replies: 1
- Views: 104
Re: Standard State
Typically a substance is in its standard state when a gas is at 1 atm and 1M. For a pure liquid or sold it is most stable at 1 atm and a temperature of interest or about 25C.
- Sun Jan 26, 2020 8:08 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Method 2
- Replies: 4
- Views: 134
Re: Method 2
In Method 2 you use each individual bond enthalpies to calculate delta H. Using the Lewis structures you look at which bonds are broken in the reactants and which bonds are formed in the products. The bonds broken are positive enthalpies and bonds formed are negative. Then you add the enthalpies of ...
- Sun Jan 26, 2020 8:05 pm
- Forum: Phase Changes & Related Calculations
- Topic: Phase Changes
- Replies: 7
- Views: 190
Re: Phase Changes
If the substance is not in the most stable/standard phases then you must use the total of the enthalpy of the phase change and the bond enthalpy when calculating.
- Sun Jan 26, 2020 8:02 pm
- Forum: Phase Changes & Related Calculations
- Topic: Focus 4 Homework Questions
- Replies: 3
- Views: 73
Re: Focus 4 Homework Questions
I would definitely start with 4D because that's what addresses enthalpy!
- Sun Jan 26, 2020 8:00 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: percent ionization
- Replies: 5
- Views: 157
Re: percent ionization
The small percent ionization indicates the change in molar concentration or x is so small that it becomes negligible and this makes the approximation acceptable.
- Sun Jan 19, 2020 7:50 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Stoichiometric coefficients for pH/pOH
- Replies: 3
- Views: 162
Re: Stoichiometric coefficients for pH/pOH
No, you do not need to raise it to the stoichiometric coefficients because when you take the pOH you are taking the -log of the concentration of OH- ions, not the ratio of them.
- Sun Jan 19, 2020 7:43 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Shift Of Reaction
- Replies: 4
- Views: 209
Re: Shift Of Reaction
It means that the reaction has to shift towards the reactants or products in order to achieve the same ratio and the same K value.
- Sun Jan 19, 2020 7:42 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 5%
- Replies: 4
- Views: 155
Re: 5%
The 5% rule applies to when you use the ICE table. If K is less than 10^-3, then you can assume that X is so small that it will not make a difference. For example if you have K=X^2/(0.3-X), then you can change it to X^2/0.3 because the X in the denominator becomes negligible. The 5% rule is if you f...
- Sun Jan 19, 2020 7:00 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Molar concentration of acids & bases
- Replies: 8
- Views: 350
Re: Molar concentration of acids & bases
If it asks for molar concentrations I believe it is asking for mol/L. pH or pOH will be asked for specifically.
- Sun Jan 19, 2020 6:55 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Strong Acids/Bases vs. Weak Acids/Bases
- Replies: 9
- Views: 207
Re: Strong Acids/Bases vs. Weak Acids/Bases
In discussion, my TA mentioned these as strong acids and bases! I think they would be helpful to memorize so that you know which acids or bases completely dissociate.
Strong Acids: HCl, HNO3, H2SO4, HBr, HI, HClO4
Strong Bases: LiOH, NaOH, KOH, Ca(OH)2, Ba(OH)2, Sr(OH)2
Strong Acids: HCl, HNO3, H2SO4, HBr, HI, HClO4
Strong Bases: LiOH, NaOH, KOH, Ca(OH)2, Ba(OH)2, Sr(OH)2
- Sun Jan 19, 2020 6:51 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 5% rule
- Replies: 3
- Views: 119
Re: 5% rule
The 5% percent rule is used to check if our "X is small" approximation is valid or not. We check to see if the X we solve for is less than 5% of the initial concentration. If it IS less than 5% then the approximation is valid.
- Sun Jan 19, 2020 6:48 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: ICE Tables
- Replies: 13
- Views: 407
Re: ICE Tables
H2O is often not included because it is a liquid, or solvent in the solution. Therefore, it is not included in the K expression or in the ICE table.
- Sun Jan 19, 2020 6:45 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Homework problem 5.I.15
- Replies: 4
- Views: 296
Re: Homework problem 5.I.15
I don't think ICE tables are necessary to get full credit on tests as long as you get the right answer. Although I would suggest using one because there's possible partial credit.
- Sun Jan 19, 2020 6:42 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 5.I.23
- Replies: 3
- Views: 125
Re: 5.I.23
You still need to include the H2O in the equilibrium expression. You can only disregard it if it is a solid or liquid!
- Sun Jan 19, 2020 6:40 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: 5I.19
- Replies: 1
- Views: 146
Re: 5I.19
Since we know that 60% of the H2 reacted, then at equilibrium we can use the fact that there will be 40% left when solving for the equilibrium concentrations. Therefore, when we use the ICE table, we can set the change in H2 (0.133-x) equal to the equilibrium value of H2 (0.4 x 0.133) and solve for X!
- Sun Jan 19, 2020 6:37 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: 5I.29
- Replies: 1
- Views: 133
Re: 5I.29
Using the reaction given, set up an ICE table. You should get a Kp equation that looks like x^2/(0.22-2x)^2 and set this equal to the Kp given. Because the equilibrium constant is small, we can assume that X is negligible compared to 0.22, therefore we can ignore it in the denominator. We end up hav...
- Wed Jan 15, 2020 10:28 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: K units
- Replies: 10
- Views: 460
Re: K units
For the purpose of this class, K is unitless. But in higher classes, it refers to the "activity" of the reactants and products.
- Sat Dec 07, 2019 5:21 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Uncertainty in Position
- Replies: 1
- Views: 204
Re: Uncertainty in Position
Yes! The diameter is the uncertainty in position.
- Sat Dec 07, 2019 5:18 pm
- Forum: Biological Examples
- Topic: Polydentate
- Replies: 3
- Views: 115
Re: Polydentate
Polydentate is referring to anything that can bind in two or more places. I would describe EDTA as a hexadentate to be more specific!
- Fri Dec 06, 2019 4:23 pm
- Forum: Bronsted Acids & Bases
- Topic: J.13 B
- Replies: 1
- Views: 167
Re: J.13 B
Yes, CH3COOH is the acid and CH3NH2 is the base!
- Fri Dec 06, 2019 4:19 pm
- Forum: Sigma & Pi Bonds
- Topic: hybridization and sigma and pi bonds
- Replies: 1
- Views: 277
Re: hybridization and sigma and pi bonds
The triple bond between C and N has one sigma bond and two pi bonds.
The sigma bond is written as sigma(Chybridization,Nhybridization)
Then you will have two pi bonds are written as pi(C2p,N2p)
The sigma bond is written as sigma(Chybridization,Nhybridization)
Then you will have two pi bonds are written as pi(C2p,N2p)
- Fri Dec 06, 2019 4:13 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Calculating KA
- Replies: 1
- Views: 79
Re: Calculating KA
For 14A we will not have to calculate the Ka for weak acids. We will learn that in 14B. I would know how to calculate the pKa of a weak acid when given Ka though assuming that it is given to us.
- Sun Dec 01, 2019 7:32 pm
- Forum: Dipole Moments
- Topic: dipole moments
- Replies: 6
- Views: 378
Re: dipole moments
Yes, polar molecules possess a permanent dipole moment.
- Sun Dec 01, 2019 7:30 pm
- Forum: Naming
- Topic: Naming Order
- Replies: 5
- Views: 334
Re: Naming Order
(Greek Prefix) Ligand names in alphabetical order, Transition Metal Cation Name (Roman Numeral). If there are anions, then add it to the end. If there is water then add (Greek Prefix) Hydrate.
- Sun Dec 01, 2019 7:27 pm
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: Diamagnetism and Paramagnetism
- Replies: 2
- Views: 222
Re: Diamagnetism and Paramagnetism
A paramagnetic electron is an unpaired electron. An atom is considered paramagnetic if even one orbital has a net spin. Diamagnetic electrons are whenever two electrons are paired together in an orbital, or their total spin is 0. Also, diamagnetic atoms/compounds (and atoms) have paired electrons an...
- Sun Dec 01, 2019 7:25 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Random Example
- Replies: 1
- Views: 153
Re: Random Example
Since this is a coordination compound the lewis structure would have the transition metal in the middle and the ligands in bonded to it, all in square brackets.
- Sun Dec 01, 2019 7:24 pm
- Forum: *Crystal Field Theory
- Topic: Crystal Field Theory
- Replies: 5
- Views: 959
Re: Crystal Field Theory
Crystal field theory (CFT) is a bonding model that explains many important properties of transition-metal complexes, including their colors, magnetism, structures, stability, and reactivity. It qualitatively describes the strength of the metal-ligand bonds in transition-metal complexes. Based on the...
Re: 9C.1
To figure out the charge of the metal you can look at the ligands and overall charge of the complex. Since there are 6 CN- and the overall charge is 4-, that means the charge of Fe is 2+. To name the compound, you should write out the name for it by beginning with each ligand, in alphabetical order,...
- Sun Nov 24, 2019 6:12 pm
- Forum: Hybridization
- Topic: Strength of sigma vs pi bonds
- Replies: 6
- Views: 149
Re: Strength of sigma vs pi bonds
A sigma bond is stronger. Sigma bonds result from the head-on overlap of the orbitals of the two atoms, which has more area of overlap than pi bonds which result from the parallel overlap of orbitals. That is why sigma bonds are stronger.
- Sun Nov 24, 2019 6:11 pm
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: diamagnetism
- Replies: 5
- Views: 348
Re: diamagnetism
Any time two electrons share the same orbital, their spin quantum numbers have to be different. Whenever two electrons are paired together in an orbital, or their total spin is 0, they are diamagnetic electrons.
- Sun Nov 24, 2019 6:10 pm
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: paramagnetism
- Replies: 8
- Views: 657
Re: paramagnetism
A paramagnetic electron is an unpaired electron. An atom is considered paramagnetic if even one orbital has a net spin.
- Sun Nov 24, 2019 6:06 pm
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: Reactivity of pi bonds
- Replies: 2
- Views: 272
Re: Reactivity of pi bonds
Sigma bonds result from the head-on overlap of the orbitals of the two atoms, which has more area of overlap than pi bonds which result from the parallel overlap of orbitals. That is why sigma bonds are stronger.
- Sun Nov 24, 2019 1:54 pm
- Forum: Biological Examples
- Topic: Heme complex
- Replies: 8
- Views: 603
Re: Heme complex
A heme complex forms when an iron ion binds to the porphyrin ligand. The porphyrin ligand is a tetradentate ring structure, meaning the fact that there are four nitrogens facing inward that can can form coordination complexes with the iron. When this complex binds with another protein they make up m...
- Sun Nov 24, 2019 1:48 pm
- Forum: Hybridization
- Topic: sp3 hybridization
- Replies: 1
- Views: 196
Re: sp3 hybridization
The characteristic tetravalence of carbon is due to the small promotion energy of a carbon atom. This energy is small because a 2s-electron is transferred from an orbital that it shares with another electron to an empty 2p-orbital. Although the promoted electron enters an orbital of higher energy, i...
- Sun Nov 17, 2019 8:08 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Radicals
- Replies: 5
- Views: 286
Re: Radicals
The VESPR theory applies to radicals, and they can be counted as electron densities. For example, in CH3 you have 7 total electrons it's going to be a trigonal planar you're going to have the Carbon as the central atom that is bonded to 3 H's and then you have one electron (unpaired lone pair) on th...
- Sun Nov 17, 2019 8:00 pm
- Forum: Hybridization
- Topic: VSEPR Models
- Replies: 1
- Views: 68
Re: VSEPR Models
The VSEPR model is used to determine the molecular geometry and the electron-group geometry. The Lewis structure helps us identify the bond pairs and the lone pairs.
- Sun Nov 17, 2019 2:55 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: 2E.1
- Replies: 1
- Views: 139
Re: 2E.1
The one with the bond angle as 120 degrees must have lone pairs. The one that is 180 degrees may have lone pairs.
- Sun Nov 17, 2019 1:14 pm
- Forum: Bond Lengths & Energies
- Topic: Polarizability
- Replies: 4
- Views: 327
Re: Polarizability
Typically, cations will have less polarizability because there are less electrons and therefore the effective nuclear charge on the electrons are stronger and pulled in closer to the nucleus. Therefore, it is harder to "distort" the electron cloud making it less polarizable. The opposite i...
- Sun Nov 17, 2019 1:13 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 Bonds
- Replies: 3
- Views: 136
Re: Hydrogen Bonds
Yes, hydrogen bonds are the strongest IMF. The δ+ hydrogen is so strongly attracted to the lone pair on the other atom that it is almost as if you were beginning to form a covalent bond. It doesn't go that far, but the attraction is significantly stronger than an ordinary dipole-dipole interaction.
- Sun Nov 17, 2019 1:09 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Lone Pair location
- Replies: 3
- Views: 131
Re: Lone Pair location
In the see-saw shape the axial and equatorial positions are not chemically equivalent. If the lone pair is in the axial position, we have three LP–BP repulsions at 90°. If the lone pair is in the equatorial position, we have two 90° LP–BP repulsions at 90°. With fewer 90° LP–BP repulsions, we can pr...
- Sun Nov 10, 2019 9:55 pm
- Forum: Electronegativity
- Topic: Electron affinity
- Replies: 6
- Views: 682
Re: Electron affinity
Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons. Electron affinity is defined as the change in energy (in kJ/mole) of a neutral atom (in the gaseous phase) when an electron is added to the atom to form a negative ion.
- Sun Nov 10, 2019 1:52 pm
- Forum: Electronegativity
- Topic: Ionization energy of O vs N
- Replies: 6
- Views: 1691
Re: Ionization energy of O vs N
Since there are two electrons in the first orbital of the O sublevel, there is greater electronic repulsion in the 2p sublevel for O than N. Therefore, it is easier to remove an electron from the O than the N, and the ionization energy of O is lower than N. Also nitrogen has a lower ionization energ...
- Sun Nov 10, 2019 1:50 pm
- Forum: Dipole Moments
- Topic: Dipole moments
- Replies: 3
- Views: 190
Re: Dipole moments
Yes, dipole moments is referring to the fact that one atom is more electronegative. The larger the difference in electronegativity, the larger the dipole moment. It is conventional to draw a dipole moment arrow from positive to negative.
- Sun Nov 10, 2019 1:39 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Formal Charge Equation?
- Replies: 12
- Views: 490
Re: Formal Charge Equation?
305416361 wrote:Victoria Otuya 4F wrote:I learned an easier way to remember the formal charge equation: valence electron -(dots + line).
does this count "dots" as pairs of dots or individual ones?
Count each dot as one electron each.
- Sun Nov 10, 2019 1:25 pm
- Forum: Dipole Moments
- Topic: Boiling Point
- Replies: 11
- Views: 654
Re: Boiling Point
Professor Lavelle uses boiling points to indicate which dipole interactions are stronger because the stronger the interactions between molecules, the more energy/heat required to separate them from each other, which raises the boiling point of the molecule.
- Sun Nov 10, 2019 1:17 pm
- Forum: Bond Lengths & Energies
- Topic: polarizability
- Replies: 9
- Views: 277
Re: polarizability
When polarizability of molecules increases, it takes more energy to break the stronger bonds between molecules resulting higher melting and boiling points.
- Sun Nov 03, 2019 11:19 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: magnetic quantum number
- Replies: 5
- Views: 163
Re: magnetic quantum number
The magnetic quantum number tells you how many orbitals there are in a subshell and it tells you the orientation of the orbital.
- Sun Nov 03, 2019 11:17 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: +- vs Uncertainty
- Replies: 3
- Views: 261
Re: +- vs Uncertainty
Use 0.5 for the uncertainty!
- Sun Nov 03, 2019 12:41 am
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Which equations can be used for what topics
- Replies: 2
- Views: 81
Re: Which equations can be used for what topics
You can use c=(lambda)(nu) for electromagnetic radiation, or light.
You can use lambda=h/p or lambda=h/mv for electrons because they have mass.
You can use lambda=h/p or lambda=h/mv for electrons because they have mass.
- Sun Nov 03, 2019 12:35 am
- Forum: Electronegativity
- Topic: Ionization energy and electronegativity
- Replies: 8
- Views: 733
Re: Ionization energy and electronegativity
Electronegativity is a measurement of a neutral atom's likelihood of gaining an electron.
Ionization energy is the minimum energy required to remove a valence electron.
Both of these have the trend of increasing going towards the right and increasing going up the periodic table.
Ionization energy is the minimum energy required to remove a valence electron.
Both of these have the trend of increasing going towards the right and increasing going up the periodic table.
- Sun Nov 03, 2019 12:32 am
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Electron configurations of ions
- Replies: 4
- Views: 326
Re: Electron configurations of ions
I think it is important to write the ground state first so that we can see which orbital has the highest energy so we can easily see where to remove or add electrons. It may not be totally necessary though, more just useful.
- Sun Nov 03, 2019 12:30 am
- Forum: Properties of Light
- Topic: Equations
- Replies: 4
- Views: 149
Re: Equations
I'm assuming they will be given to us because Dr. Lavelle's Constants and Equations sheet on his site has all three of these equations on it!
- Sun Oct 27, 2019 10:17 pm
- Forum: Ionic & Covalent Bonds
- Topic: Ionization Energy Unit
- Replies: 6
- Views: 147
Re: Ionization Energy Unit
kJ/mol!
- Sun Oct 27, 2019 10:16 pm
- Forum: Trends in The Periodic Table
- Topic: Cations vs Parent atoms
- Replies: 4
- Views: 180
Re: Cations vs Parent atoms
Cations are smaller than their parent ions because cations lose electrons and when an atom loses electrons, the positively charged nucleus pulls the electrons more closely making it smaller.
- Sat Oct 26, 2019 11:39 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Pauli Exclusion Principle
- Replies: 3
- Views: 190
Re: Pauli Exclusion Principle
The spins of two electrons are said to be paired if one is ↑ and the other ↓. Paired spins are denoted ↑↓, and electrons with paired spins have spin magnetic quantum numbers of opposite signs. No two electrons in an atom can have the same set of four quantum numbers.
- Sat Oct 26, 2019 2:16 pm
- Forum: Ionic & Covalent Bonds
- Topic: Atomic Radius
- Replies: 4
- Views: 372
Re: Atomic Radius
Atomic size decreases from left to right across a period of elements. This is because protons are being added to the nucleus making it more positively charged as well as the fact that electrons are added to the same shell. This creates greater nuclear attraction and therefore the electrons are pulle...
- Sat Oct 26, 2019 2:10 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Special elements
- Replies: 2
- Views: 102
Re: Special elements
The two main exceptions are Chromium ([Ar]3d^5 4s^1) and Copper ([Ar] 3d^10 4s^1)
These are exceptions to the general rule because a completely full or half full d sub-level is more stable than a partially filled d sub-level.
These are exceptions to the general rule because a completely full or half full d sub-level is more stable than a partially filled d sub-level.
- Sat Oct 26, 2019 1:43 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Energy Level transition in hydrogen atom
- Replies: 2
- Views: 130
Re: Energy Level transition in hydrogen atom
Frequency = -R [(1/n*2) - (1/N*2)]
in which "n" is the initial energy level, and "N" is the final energy level and we are supposed to solve for "n"
1.14x10^14 = -3.29x10^15 [(1/n^2) - (1/4^2)]
Solving for n, I ended up with n=6!
in which "n" is the initial energy level, and "N" is the final energy level and we are supposed to solve for "n"
1.14x10^14 = -3.29x10^15 [(1/n^2) - (1/4^2)]
Solving for n, I ended up with n=6!
- Sat Oct 26, 2019 1:34 pm
- Forum: Ionic & Covalent Bonds
- Topic: Cation
- Replies: 23
- Views: 1486
Re: Cation
As others have said, a cation loses electrons and anions gain electrons. Therefore, cations have a positive charge and anions have a negative charge.
My high school teacher told us to think that a cat has "paws" so therefore CATions are "pawsitive"
My high school teacher told us to think that a cat has "paws" so therefore CATions are "pawsitive"
- Sun Oct 20, 2019 9:51 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Electron Configuration Rules
- Replies: 3
- Views: 134
Re: Electron Configuration Rules
A completely full or half full d sub-level is more stable than a partially filled d sub-level, so an electron from the 4s orbital is excited and rises to a 3d orbital. It is easier for them to remove a 4s electron and bring it to the 3d subshell, which will give them a half-filled or completely fill...
- Sun Oct 20, 2019 9:50 pm
- Forum: Trends in The Periodic Table
- Topic: Atomic Radius
- Replies: 7
- Views: 422
Re: Atomic Radius
You can calculate it using the distance between two nuclei of touching identical atoms, but as far as trends for atomic radius,
The size of an atom will decrease as you move from left to the right of a period.
The radius of atoms increases as you go down a certain group.
The size of an atom will decrease as you move from left to the right of a period.
The radius of atoms increases as you go down a certain group.
- Sun Oct 20, 2019 9:46 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Ground State
- Replies: 5
- Views: 220
Re: Ground State
In a ground-state atom, all electrons are in the lowest possible energy levels.
- Sun Oct 20, 2019 9:45 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: Balmer and Lyman Series
- Replies: 6
- Views: 620
Re: Balmer and Lyman Series
They both apply to the Hydrogen atom. Emission or absorption processes in hydrogen give rise to series, which are sequences of lines corresponding to atomic transitions, each ending or beginning with the same atomic state in hydrogen. For the Lyman series, which corresponds to UV light, the electron...
- Sun Oct 20, 2019 9:39 pm
- Forum: Photoelectric Effect
- Topic: 1B.3
- Replies: 3
- Views: 101
Re: 1B.3
In the photoelectric experiment, a certain light was used to attempt to eject an electron from a metal. The experiment showed that if the light were a wave, then simply increasing the intensity would increase energy. But, increasing the intensity of the light did not result in ejection. Scientists t...
- Sun Oct 20, 2019 8:43 pm
- Forum: Einstein Equation
- Topic: 1B.9 help
- Replies: 4
- Views: 262
Re: 1B.9 help
You need to convert nm to m then use the equation: E=hc/lambda. E = [(6.626 x 10^-34 Js)(3.0 x 10^8 m/s)]/(420 x 10^-9 m) = 4.7 x 10^-19 J Doing this gives us how much energy in Joules each photon has. Then multiply 32 W by 2, so 64 J are generated in 2.0 seconds. Use the answer we found above to ge...