Search found 102 matches
- Sat Mar 14, 2020 8:42 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Arrhenius equation and activation energies
- Replies: 2
- Views: 271
Re: Arrhenius equation and activation energies
Yes, if given all other information, the Arrhenius equation can be used to find the activation energy, Ea. I think exponential could be referring to when both sides are raised to the power of e which cancels the ln on the left and then raises the right side to the power of e.
- Sat Mar 14, 2020 8:37 pm
- Forum: Balancing Redox Reactions
- Topic: Test 2 Return
- Replies: 20
- Views: 1147
Re: Test 2 Return
I think it depends on your individual TA
- Sat Mar 14, 2020 7:55 pm
- Forum: General Rate Laws
- Topic: Kr Units for Different Order Reactions
- Replies: 3
- Views: 544
Kr Units for Different Order Reactions
What units is Kr in a first order, 2nd order, and 0 order reaction?
- Sat Mar 14, 2020 11:11 am
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Arrhenius Equation
- Replies: 3
- Views: 450
Arrhenius Equation
What is ln [A] in the Arrhenius equation, ln kr = ln A - (Ea/RT)
- Fri Mar 13, 2020 4:04 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Why is Q the concentration of anode/cathode?
- Replies: 3
- Views: 10820
Re: Why is Q the concentration of anode/cathode?
Why is the anode considered the product and the cathode considered the reactant?
- Fri Mar 13, 2020 2:36 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Calculating lnQ in Nernst Equation
- Replies: 2
- Views: 275
Calculating lnQ in Nernst Equation
In the Nernst Equation, E = Eo -(RT/nF)ln Q , for Q specifically, do we put the anode concentration at the top or the bottom? And why?
- Wed Mar 11, 2020 9:10 pm
- Forum: General Rate Laws
- Topic: 7A.3A Reaction Concentration
- Replies: 3
- Views: 319
7A.3A Reaction Concentration
I'm confused on the following question and was wondering if someone could provide a mental walkthrough of how they got the answer. (The answer is given by the textbook: (a) Second order in NO, first order in O2 ) "When the NO concentration is doubled, the rate of the reaction 2NO (g) + O2 (g) -...
- Sun Mar 08, 2020 11:59 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: n in NFE
- Replies: 64
- Views: 2940
Re: n in NFE
n is the number of electrons transferred which cannot be determined until your redox half-reactions are balanced. These half-reactions should have the same number of electrons transferred on opposite sides.
- Sun Mar 08, 2020 11:57 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Exothermic vs. Endothermic
- Replies: 14
- Views: 921
Re: Exothermic vs. Endothermic
With reaction profiles to get delta H you have to subtract the end of the graph (products) by the beginning of the graph (reactants). So you have to remember that EXOTHERMIC reactions release energy into their surroundings meaning there is a loss of energy from the system ( meaning delta H = - ). So...
- Sun Mar 08, 2020 11:49 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: galvanic vs electrolytic
- Replies: 12
- Views: 811
Re: galvanic vs electrolytic
When Galvanic cells are brought up it helps me to immediately think of batteries to help me remember that Galvanic cells convert chemical energy into electrical energy.
- Sun Mar 08, 2020 11:47 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Concentration Cell
- Replies: 7
- Views: 471
Re: Concentration Cell
If a concentration cell has the same concentration on the anode and cathode then the reaction is at equilibrium and there is no net transfer of electrons in either direction. If this happens in a battery it means that the battery is dead.
- Sun Mar 08, 2020 11:45 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: G=-nFe
- Replies: 7
- Views: 782
Re: G=-nFe
n is the number of electrons transferred and can be seen in the half reactions when balanced. Since your redox half reactions are balanced, the number of electrons given off should be the same for both half-reactions.
- Sun Mar 08, 2020 11:42 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Calculating ln Q
- Replies: 20
- Views: 1453
Re: Calculating ln Q
Q is the the concentration of the products divided by the concentration of the reactants. It is used in the Nernst equation as a replacement for K when a reaction is not at equilibrium.
- Tue Mar 03, 2020 10:55 pm
- Forum: Balancing Redox Reactions
- Topic: Acidic and Basic Redox Reactions
- Replies: 9
- Views: 526
Acidic and Basic Redox Reactions
Will we usually be told if the redox reaction we're asked to balance is either acidic or basic?
- Sun Mar 01, 2020 11:44 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Going from pKa to pH
- Replies: 10
- Views: 657
Re: Going from pKa to pH
Maybe you meant that when pKa = 10^-7 that the pH = 7, which would be true.
- Sun Mar 01, 2020 11:42 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Difference Between Galvanic and Voltaic Cells
- Replies: 3
- Views: 254
Re: Difference Between Galvanic and Voltaic Cells
They're the same thing just different names
- Sun Mar 01, 2020 11:40 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Kinetics in Test 2?
- Replies: 13
- Views: 786
Re: Kinetics in Test 2?
No, the test will only cover material from page 2 of Outline 4: Thermodynamics and all of Outline 5: Electrochemistry.
- Sun Mar 01, 2020 11:35 pm
- Forum: Balancing Redox Reactions
- Topic: half rxn or ionization
- Replies: 3
- Views: 264
Re: half rxn or ionization
I think half reactions do not give the state of the reactants and products, like (aq), (s), or (g).
- Sun Mar 01, 2020 11:34 pm
- Forum: Balancing Redox Reactions
- Topic: Acidic and Basic Reactions
- Replies: 9
- Views: 478
Re: Acidic and Basic Reactions
H+ is used for balancing hydrogen atoms in acidic solutions and OH- is used to balance hydrogen in basic solutions. H2O is used to balance oxygen for both types of reactions.
- Mon Feb 24, 2020 1:00 am
- Forum: Balancing Redox Reactions
- Topic: Balancing Redox Reactions
- Replies: 7
- Views: 423
Re: Balancing Redox Reactions
What are basic conditions?
- Mon Feb 24, 2020 12:58 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Oxidation versus reduction
- Replies: 9
- Views: 449
Re: Oxidation versus reduction
Conventionally it is shown flowing left from right where the left is the anion (anode) and the right is the cation (cathode).
- Mon Feb 24, 2020 12:56 am
- Forum: Balancing Redox Reactions
- Topic: Determining direction of flow
- Replies: 15
- Views: 754
Re: Determining direction of flow
Eesha Sohail 1D wrote:If the direction is reversed, does G become positive? And what is this reverse case named, if the normal is a battery?
I think batteries are Galvanic cells and happen when G is negative. When G is positive the reaction becomes nonspontaneous and is called an electrolytic cell.
- Mon Feb 24, 2020 12:49 am
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Nernst Equation usage
- Replies: 6
- Views: 360
Re: Nernst Equation usage
The Nernst Equation relates cell potential to the concentration of what is being reduced and oxidized in their aqueous solutions.
- Mon Feb 24, 2020 12:31 am
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: STP
- Replies: 13
- Views: 705
Re: STP
STP means Standard Temperature and Pressure which is 273 K and 1 atm.
- Sun Feb 16, 2020 5:31 pm
- Forum: Calculating Work of Expansion
- Topic: work = 0
- Replies: 14
- Views: 1282
Re: work = 0
Pressure inside a vacuum is zero so when using the equation w = - P ex * delta V, the work done by a system is also equal to zero.
- Tue Feb 11, 2020 11:46 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Calculating Enthalpy with Atoms, Linear Molecules, and Nonlinear Molecules.
- Replies: 2
- Views: 168
Calculating Enthalpy with Atoms, Linear Molecules, and Nonlinear Molecules.
What are some examples of monatomic gases where we will have to calculate enthalpy with Cv,m as 3/2 R? Will most calculations for with Cv,m use the values associated with Linear molecules (5/2 R) and Nonlinear molecules (3 R)?
- Sun Feb 09, 2020 8:44 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Volume decrease
- Replies: 7
- Views: 231
Re: Volume decrease
PranaviKolla2B wrote:Can someone explain what it means when the reaction shifts one way or another?
A reaction shifts left when reactants are being produced at a higher rate than products and a reaction that shifts right means that products are being formed at a higher rate than the reactants.
- Sun Feb 09, 2020 8:41 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Isothermal and Reversible
- Replies: 6
- Views: 130
Re: Isothermal and Reversible
So does irreversible just refer to anything that is not at constant temperature, or is there a more specific definition?
- Sun Feb 09, 2020 8:39 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: ICE BOX
- Replies: 27
- Views: 754
Re: ICE BOX
If you exclude the x and want to double check afterwards to see if the approximation is accurate, then you can calculate the protonation percentage, or deprotonation percentage depending on the question, and if it is below 5% then the approximation is correct.
- Sun Feb 09, 2020 8:17 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Midterm Content
- Replies: 6
- Views: 347
Re: Midterm Content
I think so, Lavelle mentioned that everything on the first page of the Thermodynamics Outline, which I think is also the first two rows of problems.
- Sun Feb 09, 2020 8:14 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Finding concentration of H30 and OH from Kw
- Replies: 2
- Views: 300
Re: Finding concentration of H30 and OH from Kw
I would guess that you take the square root of the Kw value given since we are dealing with water.
- Sun Feb 02, 2020 6:34 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: extensive property
- Replies: 12
- Views: 604
Re: extensive property
An example of an extensive property is Heat Capacity because it tells you the amount of heat required to raise the temperature of an object by 1 degree celsius but it does not tell you how much of that object is present, so the information provided is not useful for other calculations.
- Sun Feb 02, 2020 6:30 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Heat Capacity 4C.3
- Replies: 3
- Views: 92
Re: Heat Capacity 4C.3
For this problem you would not be able to find the heat capacity of Kr gas because the final volume is not given to us, but I am also confused on determining which equation to use for this.
- Sun Feb 02, 2020 6:19 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Ka approximation
- Replies: 6
- Views: 491
Re: Ka approximation
You could probably check by including the -x and then using the Quadratic Formula and then comparing this value to the value you got when you ignored the -x.
- Sun Feb 02, 2020 6:09 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Test 1 Pressure
- Replies: 5
- Views: 274
Re: Test 1 Pressure
If more pressure is exerted, then the reaction will shift to the side with less moles. I like to think of the reaction as being squeezed and to adapt, the reaction overflows onto the side that is less cramped up because there is more space there.
- Sun Feb 02, 2020 5:17 pm
- Forum: Phase Changes & Related Calculations
- Topic: Relevance of Phase Changes
- Replies: 9
- Views: 432
Re: Relevance of Phase Changes
If you are calculating the change in enthalpy of a substance and that substance changes phases then it is important to add the energy required by the phase change in order to get an accurate calculation for ΔH.
- Sun Jan 26, 2020 7:44 pm
- Forum: Phase Changes & Related Calculations
- Topic: Delta H
- Replies: 3
- Views: 159
Re: Delta H
For the methods discussed in lecture on Friday, we will need to be given multiple ΔH's so that we can add or subtract them to find out the value of the ΔH we don't know.
- Sun Jan 26, 2020 7:38 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Standard States
- Replies: 2
- Views: 171
Re: Standard States
The standard state is the substance's phase (solid, liquid,gas) at 25 degrees Celsius and at 1 atm of pressure.
- Sun Jan 26, 2020 7:26 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Pressure vs. Volume
- Replies: 6
- Views: 238
Re: Pressure vs. Volume
A change in volume will also directly affect the pressure of a system. A decrease in volume will lead to a higher pressure and an increase in volume will lead to lower pressure. Thinking of the equation PV=nRT is helpful since it shows how pressure and volume are inversely proportional.
- Sat Jan 25, 2020 6:44 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Excluding H2O from Ka and Kb
- Replies: 5
- Views: 557
Excluding H2O from Ka and Kb
I know we don't include H2O (l) in caluclations for Kb and Ka but why is that?
- Sat Jan 25, 2020 6:18 pm
- Forum: Phase Changes & Related Calculations
- Topic: Endothermic and Exothermic
- Replies: 13
- Views: 515
Re: Endothermic and Exothermic
If you have trouble deciding whether a reaction is endothermic or exothermic based on direction of heat flow, I find it helpful to think of the melting of ice as an example. Ice melting into liquid water is an ENDOTHERMIC reaction. The ice's surrounding has to be warm in order for liquid water to be...
- Sun Jan 19, 2020 7:00 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Titration
- Replies: 3
- Views: 117
Re: Titration
I think he just mentioned how the information we are learning will be helpful if we take Chem 14Bl where we will be doing titrations, but no I don't think we'll be tested on them.
- Sun Jan 19, 2020 6:48 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Buffer
- Replies: 6
- Views: 319
Re: Buffer
When making a buffer, you want to choose weak acids or weak bases since strong acids or bases will make the solution's pH too extreme. The reason for this is that weak acids and bases do not fully dissociate.
- Sun Jan 19, 2020 6:46 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: pH vs. pOH
- Replies: 13
- Views: 382
Re: pH vs. pOH
Sometimes certain problems will make it easier to calculate pH, and if the pOH is being asked then you can take the pH (-log(H3O+)) and subtract that value from 14 (since pH + pOH + 14).
- Sun Jan 19, 2020 6:43 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Approximation
- Replies: 6
- Views: 351
Re: Approximation
Does it have to do with using significant figures? Like when we round our answer to a significant figure, the difference in our answer that a -X would have provided does not even make a difference in our final rounded answer?
- Sun Jan 19, 2020 6:28 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Endo vs. Exothermic
- Replies: 5
- Views: 176
Re: Endo vs. Exothermic
If you're looking at a graph, an endothermic reaction will be drawn so that the ending of the graph is higher than the beginning. This means that the products of the reaction will have greater energy than the reactants. And for an exothermic reaction graph, the ending of the graph will be lower than...
- Sun Jan 12, 2020 11:50 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Homogenous Equilibrium
- Replies: 13
- Views: 344
Re: Homogenous Equilibrium
Is there a different way we should approach a problem where we have to calculate the equilibrium constant if the given chemical reaction is heterogeneous and not homogeneous.
- Sun Jan 12, 2020 11:31 pm
- Forum: Ideal Gases
- Topic: K and Units
- Replies: 7
- Views: 301
Re: K and Units
The units cancel out (concentration/concentration), making K unitless.
- Sun Jan 12, 2020 11:29 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Types of Equilibrium Constants
- Replies: 7
- Views: 245
Re: Types of Equilibrium Constants
005384106 wrote:In what instances would the state of a molecule be important? (gaseous, aqueous, solid, or liquid)
Solids and liquids are excluded from calculating K. But, a gaseous reaction indicated using Kp and an aqueous reaction indicates using Kc.
- Sun Jan 12, 2020 10:37 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Comparing K
- Replies: 9
- Views: 215
Re: Comparing K
I don't think K can equal 0. If K were to equal 0, then that means there would be no product, meaning a reaction isn't taking place.
- Sun Jan 12, 2020 10:29 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Q
- Replies: 10
- Views: 340
Re: Q
You could calculate Q and if it matches K, then the reaction is at equilibrium.
- Sun Dec 08, 2019 1:07 am
- Forum: Identifying Acidic & Basic Salts
- Topic: homework question 6D.11
- Replies: 3
- Views: 208
Re: homework question 6D.11
Why is part d neutral?
d) KBR
And is asking whether an aqueous solution of this will have a pH < 7 , pH > 7, or be neutral
d) KBR
And is asking whether an aqueous solution of this will have a pH < 7 , pH > 7, or be neutral
- Sat Dec 07, 2019 10:45 pm
- Forum: DeBroglie Equation
- Topic: Identifying the need to use DeBroglie Equation
- Replies: 3
- Views: 340
Identifying the need to use DeBroglie Equation
What kind of things in a problem suggest that we use DeBroglie's equation?
- Sat Dec 07, 2019 9:11 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: pH sig figs
- Replies: 11
- Views: 604
Re: pH sig figs
Does this work the other way around too? If we were given a H3O+ concentration of 1.56 x 10^-4 where there are 3 sig figs, would we have to write the pH as 3.807 or as 3.81 ?
- Sat Dec 07, 2019 7:41 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Negative pH
- Replies: 5
- Views: 331
Negative pH
What does it mean for pH to be negative?
- Sat Dec 07, 2019 12:19 pm
- Forum: Naming
- Topic: Abbreviations (oxalato)
- Replies: 2
- Views: 259
Abbreviations (oxalato)
When writing the formula for a coordination compound containing a ligand that can be abbreviated, such as sodium bisoxalato(diaqaua)ferrate(III) containing oxalato, are we able to also write the abbreviation in the formula. For example can this coordination compound be written as: Na[Fe(OH2)2(ox)2] ...
- Sun Dec 01, 2019 5:25 pm
- Forum: Lewis Acids & Bases
- Topic: acid v. base?
- Replies: 16
- Views: 876
Re: acid v. base?
Lewis bases are positively charged. Lewis acids are negatively charged and usually have a lone pair.
- Sun Dec 01, 2019 5:20 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: pH scale
- Replies: 12
- Views: 604
Re: pH scale
Most solutions are in this range. Remember that pH is logarithmic so a pH of 15 would have a concentration of ions 10x greater than a solution with a pH of 14, which is not common.
- Sun Dec 01, 2019 5:13 pm
- Forum: Naming
- Topic: Naming for the final
- Replies: 6
- Views: 447
Re: Naming for the final
Neutral ligands have the same name except for a few. Water turns to "aqua," ammonia turns to "ammine," and CO turns to "carbonyl." Ligands that are anions end with o.
- Sun Dec 01, 2019 4:58 pm
- Forum: Trends in The Periodic Table
- Topic: Exceptions to Electroaffinity
- Replies: 3
- Views: 347
Re: Exceptions to Electroaffinity
I don't think we have been told of any exceptions in lecture so I think it's safe to assume that we wouldn't be asked any questions where knowledge of an exception would be needed to answer the question.
- Sun Dec 01, 2019 4:18 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Coordination Number
- Replies: 6
- Views: 364
Re: Coordination Number
However many ligands are attached to the central atom is what determines the coordination number. You can determine this by looking inside the brackets.
- Sun Dec 01, 2019 4:09 pm
- Forum: Sigma & Pi Bonds
- Topic: Drawing Sigma and Pi bonds
- Replies: 7
- Views: 730
Re: Drawing Sigma and Pi bonds
I think it's safest to label each bond individually with a "σ" on top of one line and a "π" on top of the other line.
- Sun Nov 24, 2019 5:07 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Seesaw
- Replies: 23
- Views: 934
Re: Seesaw
If a lone pair is present in a molecule, then it will affect the bond angles of the surrounding atoms since the repulsion force lone pairs is greater than bonded atoms.
- Sun Nov 24, 2019 4:46 pm
- Forum: Resonance Structures
- Topic: Resonance structures
- Replies: 15
- Views: 753
Re: Resonance structures
Patricia Cardenas wrote:Does anyone have advice on how to start drawing lewis structures/resonance structures?
The first step would be to identify the least electronegative atom because this one will typically be the central atom.
- Sun Nov 24, 2019 4:43 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bent Shape
- Replies: 31
- Views: 2831
Re: Bent Shape
Yea if the formula is AX2E then the angles are similar to a trigonal planar molecule (<120) but if the formula is AX2E2 then the bond angles are similar to a tetrahedral molecule (<109.5)
- Sun Nov 24, 2019 4:39 pm
- Forum: Biological Examples
- Topic: cisplatin
- Replies: 6
- Views: 375
Re: cisplatin
I think Lavelle mentioned in lecture that cisplatin not only stops cell division of cancer cells but stops division for all cells
- Sun Nov 24, 2019 4:31 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: square planar vs tetrahedral
- Replies: 5
- Views: 387
Re: square planar vs tetrahedral
Square planar has 6 electron dense regions but two of those are lone pairs, making the formula AX4E2 whereas tetrahedral only has 4 electron dense regions, all of which are bonds to another atom, making the formula AX4. The two lone pairs in a square planar molecule repulse the 4 bonds to form a squ...
- Sun Nov 17, 2019 11:04 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Lone vs. Bonding Pair
- Replies: 6
- Views: 340
Re: Lone vs. Bonding Pair
Lone pairs take up more space making the rest of the bonds move away in order to lower repulsion.
- Sun Nov 17, 2019 10:49 pm
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: Vsepr Rules
- Replies: 2
- Views: 199
Re: Vsepr Rules
If you're talking about the rules stated in the textbook, Rule 2 is telling us that multiple bonds (double bonds, triple bonds) count as only a single region of high electron density. The same way a single bond is counted as one. And the same way a lone pair counts as one. Adding up all the electron...
- Sun Nov 17, 2019 10:33 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: SF4
- Replies: 3
- Views: 214
Re: SF4
Lone pairs and bonds need to be placed where they will cause the least amount of repulsion. Considering lone-pairs have a stronger amount of repulsion than bonds do, their placement is prioritized in terms of where it will cause the least amount of repulsion. In the see-saw example shown in class th...
- Sun Nov 17, 2019 10:23 pm
- Forum: Lewis Structures
- Topic: Why can Xenon break the octet rule?
- Replies: 8
- Views: 5401
Re: Why can Xenon break the octet rule?
Xenon has d-orbitals, allowing it to store more electrons in its valence shell than atoms without any d-orbitals, like those that are at or come before 4s^2 .
- Sun Nov 17, 2019 10:13 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: bond angles
- Replies: 8
- Views: 423
Re: bond angles
Lone pairs have the strongest repulsion strength because lone pairs are less restrained than a bonding pair would be so it takes up more space making the rest of the atoms move away to lower the repulsion acting upon them.
- Sun Nov 10, 2019 11:35 pm
- Forum: Bond Lengths & Energies
- Topic: Rankings
- Replies: 2
- Views: 107
Re: Rankings
Hydrogen bonds are the strongest intermolecular force
- Sun Nov 10, 2019 11:34 pm
- Forum: Trends in The Periodic Table
- Topic: Atomic Radius
- Replies: 30
- Views: 2945
Re: Atomic Radius
Atomic radius increases going left across and down groups of the periodic table. Having higher atomic numbers means having more protons that pull the electrons closer to the nucleus, decreasing the atomic radius as you move right across the periodic table.
- Sun Nov 10, 2019 11:07 pm
- Forum: Coordinate Covalent Bonds
- Topic: Coordinate Covalent Bond
- Replies: 3
- Views: 250
Re: Coordinate Covalent Bond
A coordinate covalent bond is when one atom is responsible for giving off a lone pair that contributes to making the bond with another atom without the second atom having to sacrifice one of their own electrons to create the bond.
- Sun Nov 10, 2019 10:47 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Writing e- Configurations
- Replies: 15
- Views: 621
Re: Writing e- Configurations
I think the question would specify if you had to use a specific notation.
- Sun Nov 10, 2019 10:45 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 Strength
- Replies: 4
- Views: 256
Re: Interaction Strength
This is why rod-shaped molecules will generally have higher melting points. A lot more dipole interactions have to be broken.
- Sun Nov 03, 2019 10:52 pm
- Forum: Resonance Structures
- Topic: Octet
- Replies: 13
- Views: 783
Re: Octet
Hydrogen and Helium fill up a duplet (2 valence electrons). Other exceptions include atoms in the d-block since they have 5 orbitals allowing them to hold more than 8 outer electrons.
- Sun Nov 03, 2019 10:34 pm
- Forum: Lewis Structures
- Topic: Lone Pairs
- Replies: 12
- Views: 541
Re: Lone Pairs
It's easy to think of it as any valence electrons that aren't touching (being shared by) any other atoms in the lewis structure
- Sun Nov 03, 2019 10:28 pm
- Forum: Electronegativity
- Topic: electronegativity trend
- Replies: 9
- Views: 633
Re: electronegativity trend
Electronegativity decreases down a column because the atom gets larger and the electron gets farther away from the pull of the positively charged nucleus. Ionization is related to this since this weaker pull allows less energy to be needed to remove an electron from an atom.
- Sun Nov 03, 2019 10:09 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Writing e- Configurations
- Replies: 15
- Views: 621
Re: Writing e- Configurations
I think you can assume you're able to write the shorthand notation unless told directly by the question to write the entire configuration out.
- Sun Nov 03, 2019 9:59 pm
- Forum: Bond Lengths & Energies
- Topic: Does bond length have any effects?
- Replies: 5
- Views: 209
Re: Does bond length have any effects?
Bond length does have effects. Shorter bonds (such as triple bonds) will require more energy to break apart because the shared electrons are closer to the positively charged nuclei and thus have a stronger pull on these electrons.
- Sun Oct 27, 2019 8:11 pm
- Forum: Lewis Structures
- Topic: Lone Pairs
- Replies: 12
- Views: 541
Re: Lone Pairs
In a Lewis structure they're the two dots on the sides.
- Sun Oct 27, 2019 8:09 pm
- Forum: Trends in The Periodic Table
- Topic: Central Atom
- Replies: 13
- Views: 478
Re: Central Atom
Atom ionization energy levels generally follow a trend of decreasing as you move left across and down the periodic table.
- Sun Oct 27, 2019 7:58 pm
- Forum: Resonance Structures
- Topic: Octet
- Replies: 13
- Views: 783
Re: Octet
I think in lecture Lavelle mentioned that H, He, Li, and Be are exceptions to the octet rule.
- Sun Oct 27, 2019 7:56 pm
- Forum: Bond Lengths & Energies
- Topic: Single bond vs double bond
- Replies: 14
- Views: 823
Re: Single bond vs double bond
These numbers are the length of each bond. The double bonds are shorter because there is a stronger pull there which makes it tighter.
- Tue Oct 22, 2019 9:02 am
- Forum: Trends in The Periodic Table
- Topic: Periodic Table trends
- Replies: 11
- Views: 861
Re: Periodic Table trends
The biggest difference is their shape and their ability to hold e-. The s-orbital can only hold 2 e-. The p-orbital can only only 6 e-. The d-orbital can only hold 10 e-. The f-block can hold 14 e-. In the ground state of an atom, the electrons must fill up all spots in lower energy levels before m...
- Sun Oct 20, 2019 11:36 pm
- Forum: *Black Body Radiation
- Topic: Black Body Radiation
- Replies: 12
- Views: 694
Re: Black Body Radiation
A black body is a material that absorbs all radiation. No object is a true black body, it is more of an idea in the same way frictionless surfaces are used in physics problems.
- Sun Oct 20, 2019 11:25 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Nodal Planes
- Replies: 3
- Views: 166
Re: Nodal Planes
Orbitals are probability density functions and nodal planes are where there is a 0 percent likelihood of finding an electron.
- Sun Oct 20, 2019 8:29 pm
- Forum: Properties of Light
- Topic: Unit for Wavelength
- Replies: 34
- Views: 2297
Re: Unit for Wavelength
Wavelengths are measured in meters since it is a distance. It is common to see them measured in nanometers which is 1x10^-9 of a meter.
- Sun Oct 20, 2019 8:07 pm
- Forum: Properties of Light
- Topic: What are the units of hertz
- Replies: 41
- Views: 1942
Re: What are the units of hertz
s^-1
refers to cycles per second
refers to cycles per second
- Sun Oct 20, 2019 8:02 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Advice for studying
- Replies: 92
- Views: 6494
Re: Advice for studying
I found it helpful to read the chapters covered in lecture and going through all the example problems given. I also write question marks in my notes during lecture to remind myself what seemed confusing at the time so I can study it later.
- Sun Oct 13, 2019 11:19 pm
- Forum: Properties of Light
- Topic: Energy Equation
- Replies: 3
- Views: 150
Re: Energy Equation
It's Planck's Constant. If you multiply it with frequency (v) you get the energy of the photon.
- Sun Oct 13, 2019 10:39 pm
- Forum: Significant Figures
- Topic: sig figs and periodic tables
- Replies: 11
- Views: 673
Re: sig figs and periodic tables
If we use the rounded version of the atomic mass (let's say to the hundredths) and correctly use significant figures, would our answer be wrong if the answer we get is right according to the rounded calculations we made?
- Sun Oct 13, 2019 10:31 pm
- Forum: Photoelectric Effect
- Topic: Intensity vs. Length of Waves
- Replies: 4
- Views: 214
Re: Intensity vs. Length of Waves
Shorter wavelengths imply higher frequency (v), means more crowded bumps and higher energy for removing electrons
- Sun Oct 13, 2019 9:59 pm
- Forum: Properties of Light
- Topic: Wavelength
- Replies: 4
- Views: 173
Re: Wavelength
I think you can use the Mass of electron given in the constants sheet and plug that into the 1/2mv^2 equation which will give you the kinetic energy of the electron. Then you use c=(lambda)v to get the wavelength.
- Sun Oct 13, 2019 9:32 pm
- Forum: SI Units, Unit Conversions
- Topic: Angstrom
- Replies: 16
- Views: 791
Re: Angstrom
It's also important to remember that the Angstrom is not an SI unit
- Fri Oct 04, 2019 1:29 am
- Forum: SI Units, Unit Conversions
- Topic: scientific notation
- Replies: 7
- Views: 286
Re: scientific notation
I think it'd be a good idea to leave an answer in scientific notation if the answer in normal form would be an ambiguous number of significant figures. For example if you want to show 1000 with 3 significant figures just write 1.00 x 10^3
- Fri Oct 04, 2019 1:21 am
- Forum: SI Units, Unit Conversions
- Topic: Sig Fig Rules
- Replies: 7
- Views: 743
Re: Sig Fig Rules
No the rules are different. For adding and subtracting when dealing with decimals you can only include the decimal value that was closest to the decimal. For example if we had to add 522.7 + 49.44 = 572.14, we would have to round down so that the answer is 572.1 But for multiply or dividing you can ...
- Fri Oct 04, 2019 1:00 am
- Forum: Empirical & Molecular Formulas
- Topic: Homework Question F.9
- Replies: 6
- Views: 241
Re: Homework Question F.9
Yes, you would assume that your sample is 100 g, but to convert to moles, you actually have to divide by the molar mass of each element as found on the periodic table (so 12.01 g/mol for C). You don't need to divide 63.15 by 100 because if you assume the sample is 100 g, then 63.15% of 100 would ju...