Search found 100 matches
- Sun Mar 15, 2020 7:28 am
- Forum: Experimental Details
- Topic: Psuedo First Order
- Replies: 7
- Views: 1485
Re: Psuedo First Order
So this concept is generally used in the gathering of experimental data?
- Sun Mar 15, 2020 7:26 am
- Forum: Experimental Details
- Topic: Collision Theory
- Replies: 8
- Views: 1309
Re: Collision Theory
What exactly does temperature define on a molecular level?
- Sun Mar 15, 2020 6:39 am
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Slow and Fast Step
- Replies: 7
- Views: 549
Re: Slow and Fast Step
Does it matter if the order of the rates? For example if the first step rate is slow and the second step is fast does the slow step control the rate? What happens if the first step is fast and the second step is slow? The slow step is always the one that controls the rate of the reaction. If there ...
- Sun Mar 15, 2020 6:29 am
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: relationship of K and time
- Replies: 3
- Views: 353
Re: relationship of K and time
Just to make sure I've got this down: for a zero-order reaction the rate doesn't change, for a first-order reaction the rate decreases linearly, and for a second-order reaction it decreases exponentially. Is that correct?
- Sun Mar 15, 2020 6:26 am
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: are there standard rates of formation?
- Replies: 4
- Views: 387
Re: are there standard rates of formation?
How would you apply this kind of standard rate to a test problem? Arrhenius equation is one thing i can think of, but are there others?
- Sun Mar 08, 2020 11:49 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: intermediate species
- Replies: 4
- Views: 376
Re: intermediate species
It depends on what you're given. To get from the reactants to the products, bonds must be broken and formed, so an intermediate might be a state where, say, two reactants have joined together before they break into the product forms. It depends on the reaction mechanism of whatever you're studying.
- Sun Mar 08, 2020 11:45 pm
- Forum: First Order Reactions
- Topic: Half Life
- Replies: 13
- Views: 860
Re: Half Life
The half life of a reaction is a useful concept for relating time passed to amounts of substance in the real world. Not sure exactly what context may show up on the test, but it is frequently referenced in radioactive dating.
- Sun Mar 08, 2020 11:39 pm
- Forum: Zero Order Reactions
- Topic: Graphs
- Replies: 13
- Views: 1400
Re: Graphs
I assume we'd have to be able to correctly interpret general trends in a graph, but I don't really think we'd have to draw accurate graphs on our own; at the most there will likely be a template provided.
- Sun Mar 08, 2020 11:26 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: thermo or kinetics?
- Replies: 9
- Views: 783
Re: thermo or kinetics?
Aren't the thermodynamics and kinetics of a reaction connected though, through the relation between K and both k's? Can a change in one predictably affect the other at all?
- Sun Mar 08, 2020 11:20 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Study Advice
- Replies: 73
- Views: 7295
Re: Study Advice
Is there a way for me to get one-on-one help sometime this week? I'm still shaky on thermodynamics.
- Sun Mar 01, 2020 11:31 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Electromotive force
- Replies: 2
- Views: 201
Re: Electromotive force
Electromotive force refers to the potential difference between the two electrodes in a cell. As the cell goes to equilibrium, the E goes to zero.
- Sun Mar 01, 2020 11:28 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Electrolytes vs electrodes
- Replies: 5
- Views: 369
Re: Electrolytes vs electrodes
An electrolyte is basically a solution of ions, functioning as a medium for current flow. An electrode connects the conducting and nonconducting part of the cell, and directs the flow of electrons.
- Sun Mar 01, 2020 11:23 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell Potential Equation
- Replies: 1
- Views: 164
Re: Cell Potential Equation
Since they mean the same thing, it doesn't really matter which you use, but the log equation is easier to translate into useful values for K and pH.
- Sun Mar 01, 2020 11:21 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Voltage
- Replies: 6
- Views: 442
Re: Voltage
It's not necessarily that it's not the /same/, it's just that since it's a charged value, it's better to make sure you specify that it''s positive. Same deal with oxidation numbers, ion charges, etc.
- Sun Mar 01, 2020 10:52 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: electron flow
- Replies: 4
- Views: 219
Re: electron flow
What is the relationship between current and volts? And what exactly do volts represent contextually?
- Sun Feb 23, 2020 11:55 pm
- Forum: Balancing Redox Reactions
- Topic: Determining direction of flow
- Replies: 15
- Views: 817
Re: Determining direction of flow
If the direction is reversed, does G become positive? And what is this reverse case named, if the normal is a battery?
- Sun Feb 23, 2020 11:53 pm
- Forum: Balancing Redox Reactions
- Topic: Tips for Balancing Reactions
- Replies: 3
- Views: 227
Re: Tips for Balancing Reactions
What solutions might I commonly see in a redox problem, in either case? Asking for identification purposes.
- Sun Feb 23, 2020 11:31 pm
- Forum: Balancing Redox Reactions
- Topic: Half reactions
- Replies: 17
- Views: 938
Re: Half reactions
Are there any cases where two half reactions cannot be balanced using water, ions, and electrons?
- Sun Feb 23, 2020 11:25 pm
- Forum: Balancing Redox Reactions
- Topic: Reduction?
- Replies: 13
- Views: 704
Re: Reduction?
Is reduction generally associated with endergonic or exergonic reactions?
- Sun Feb 23, 2020 11:24 pm
- Forum: Balancing Redox Reactions
- Topic: Oxidation Number
- Replies: 3
- Views: 440
Re: Oxidation Number
The oxidation number is obtained using a few rules for each of the species in a compound. 1. The cation is written first in a formula, followed by the anion. NaCl - Na is +1, Cl is -1. 2. The oxidation number of an element by itself is always 0. O 2 - O has an oxidation # of 0. 3. The oxidation numb...
- Sun Feb 16, 2020 10:13 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: adiabatic
- Replies: 19
- Views: 1091
Re: adiabatic
Can any real process ever be completely adiabatic? Heat exchange seems like it would be inevitable, in the real world.
- Sun Feb 16, 2020 10:10 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Laws of thermodynamics
- Replies: 4
- Views: 517
Re: Laws of thermodynamics
The corollary to law #2 is that since no real process is perfectly reversible, change in entropy of the universe is always positive, correct? But why can no real process be completely reversible?
- Sun Feb 16, 2020 10:07 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Work
- Replies: 14
- Views: 1039
Re: Work
In relation to gases, work is done on the system when compression occurs, and the system does work when expansion occurs. The former is positive and the latter is negative.
- Sun Feb 16, 2020 9:37 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Temperature Dependence of K
- Replies: 3
- Views: 265
Re: Temperature Dependence of K
Considering equilibrium and K, is the delta H the same for the reaction regardless of the equilibrium concentrations, or does it still change?
- Sun Feb 16, 2020 9:09 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gibb's Free Energy
- Replies: 7
- Views: 383
Re: Gibb's Free Energy
Can one actually calculate amounts of G contained in a substance, or only transferred amounts?
- Sun Feb 09, 2020 11:36 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Intensive
- Replies: 8
- Views: 516
Re: Intensive
Can certain extensive properties be manipulated to produce corresponding intensive values? I'm thinking of heat energy versus temperature here, but I'm not sure how the quantities compare.
- Sun Feb 09, 2020 11:16 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gibbs Free Energy calculation
- Replies: 3
- Views: 244
Re: Gibbs Free Energy calculation
It depends on the values/units you are given in the question. If reaction constant is given (which, probably not) then you will most likely use the other equation. However, the G = H-TS equation is definitely the most important one.
- Sun Feb 09, 2020 11:11 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: H and Q
- Replies: 4
- Views: 352
Re: H and Q
What would nonexpansion work entail? Is that essentially just heat transfer?
- Sun Feb 09, 2020 11:05 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Reversible and Irreversible Reactions
- Replies: 3
- Views: 457
Re: Reversible and Irreversible Reactions
Physical changes involving a change in state are all reversible. For chemical reactions, I'm not sure exactly what markers you could look for to deem a reaction reversible, but it is useful to remember that reversibility is usually conditional, and reactions deemed irreversible may actually be rever...
- Sun Feb 09, 2020 10:49 pm
- Forum: Calculating Work of Expansion
- Topic: 4A.7
- Replies: 3
- Views: 149
Re: 4A.7
Chem Mod, does the A in your equation represent a delta? For change of temperature?
- Sun Feb 02, 2020 11:41 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: residual entropy
- Replies: 4
- Views: 193
Re: residual entropy
How is change in entropy calculated? What are its units?
- Sun Feb 02, 2020 11:39 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: kinetics
- Replies: 8
- Views: 244
Re: kinetics
For right now, with energy transfer and stuff, kinetics isn't really relevant, right? I don't believe we've really talked about rates.
- Sun Feb 02, 2020 11:36 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: 4A. 5 Isothermic VS. Reversible
- Replies: 2
- Views: 109
Re: 4A. 5 Isothermic VS. Reversible
How does an isothermic process differ from an adiabatic one?
- Sun Feb 02, 2020 11:34 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: when is w=0 and when is q=0?
- Replies: 6
- Views: 1012
Re: when is w=0 and when is q=0?
In an adiabatic process, heat does not enter or leave the system. Energy transfer happens only through work, so Q=0.
- Sun Feb 02, 2020 11:28 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Changing a Closed System
- Replies: 2
- Views: 155
Re: Changing a Closed System
Could there be any situation where matter-energy transfer occurs in a closed system? As in, converted into each other.
- Sun Jan 26, 2020 11:42 pm
- Forum: Phase Changes & Related Calculations
- Topic: State Function
- Replies: 3
- Views: 106
Re: State Function
A state function means that the pathway doesn't matter, only the start and endpoints do. An analogy can be drawn to displacement; between two points there is only one displacement even though there's a multitude of various distances one could take to get there.
- Sun Jan 26, 2020 11:38 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Signs for enthalpy
- Replies: 8
- Views: 529
Re: Signs for enthalpy
Negative enthalpy would indicate that through a reaction, heat was lost. A reaction with negative enthalpy is the same as an exothermic reaction.
- Sun Jan 26, 2020 11:19 pm
- Forum: Phase Changes & Related Calculations
- Topic: State function
- Replies: 4
- Views: 143
Re: State function
I always conceptualized heat as a Thing that is passed around, while enthalpy is the net change in it. How accurate/inaccurate would that assessment be for the purpose of this class?
- Sun Jan 26, 2020 11:03 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Standard Reaction Enthalpies
- Replies: 2
- Views: 54
Re: Standard Reaction Enthalpies
In general, are there any trends with the bond enthalpies of substances in different states?
- Sun Jan 26, 2020 10:43 pm
- Forum: Phase Changes & Related Calculations
- Topic: Phase changes
- Replies: 8
- Views: 242
Re: Phase changes
On the heating curve, one axis is temperature, but can someone explain what exactly temperature means on a molecular level vs heat?
- Sun Jan 19, 2020 10:30 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Acid Base Equilibria
- Replies: 5
- Views: 199
Re: Acid Base Equilibria
I don't particularly understand the distinction between the K calculated through pressure of a gas and K from concentration. How are they different, and can they be converted into each other in any case?
- Sun Jan 19, 2020 10:17 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Le Chatelier's Priciple
- Replies: 4
- Views: 241
Re: Le Chatelier's Priciple
Liquids and solids are not part of the equilibrium constant expression, so they will not affect the concentration of the reactants or products.
- Sun Jan 19, 2020 9:50 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: ICE Tables
- Replies: 13
- Views: 523
Re: ICE Tables
I understand the logic of the excess analogy, but how does the concept of chemical "activities" factor into this concept?
- Sun Jan 19, 2020 9:47 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 6B.11
- Replies: 2
- Views: 128
Re: 6B.11
Would the product NaOH be counted as a solid or as separate ions in solution in the net ionic equation?
- Sun Jan 19, 2020 9:43 pm
- Forum: Ideal Gases
- Topic: PV=nRT
- Replies: 13
- Views: 719
Re: PV=nRT
As far as I've seen, the ideal gas law is taught in high school chemistry classes more than physics classes, but that's a bit of a moot point. That said, could we possibly use other variants of the law to figure things out as well, such as P(mm) = dRT (where mm = molar mass and d = density)?
- Sun Jan 12, 2020 11:57 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: When does the partial pressure of a gas change?
- Replies: 2
- Views: 82
Re: When does the partial pressure of a gas change?
The partial pressures in such a case are solely regarded if they are relevant to the occurring reaction; the partial pressures of the reactants/products don't change /in relation to/ each other, because the ratio is what is important. According to the ideal gas law, pressure varies directly with con...
- Sun Jan 12, 2020 11:39 pm
- Forum: Ideal Gases
- Topic: When is the Ideal Gas Law Not Applicable?
- Replies: 2
- Views: 107
Re: When is the Ideal Gas Law Not Applicable?
For our purposes at the moment, I think we can apply it to all the situations given to us in classwork. With low temperature and high pressure, the actual results will deviate from the ones given by the law. Doesn't necessary mean it's not applicable, it would just be more complicated to get a more ...
- Sun Jan 12, 2020 11:28 pm
- Forum: Ideal Gases
- Topic: Vapor Pressure
- Replies: 4
- Views: 201
Re: Vapor Pressure
For vapor pressure, what environmental factors can influence how much of a substance will vaporize? Does pressurizing the gas affect that in any way?
- Sun Jan 12, 2020 11:07 pm
- Forum: Ideal Gases
- Topic: Ideal gas law exceptions
- Replies: 3
- Views: 183
Re: Ideal gas law exceptions
The ideal gas law is meant to approximate the behavior of gases excluding potential intermolecular interactions. The more interactions between particles, the more deviation from the law. So, interestingly, noble gases are some of the most ideal gases out there, as far as I know - particularly helium...
- Sun Jan 12, 2020 11:03 pm
- Forum: Ideal Gases
- Topic: K and Units
- Replies: 7
- Views: 349
Re: K and Units
Yes, since K represents a ratio of similar quantities, it is unitless. (concentration divided by concentration)
- Sat Dec 07, 2019 11:12 pm
- Forum: Industrial Examples
- Topic: what examples should we know?
- Replies: 6
- Views: 1300
Re: what examples should we know?
How do hemoglobin complexes create myoglobin; do they bind together, and in what way? I know there are four hemoglobin subunits, but I don't understand how they fit together.
- Sat Dec 07, 2019 10:58 pm
- Forum: Naming
- Topic: naming ligands in alphabetical order
- Replies: 2
- Views: 105
Re: naming ligands in alphabetical order
I believe this is correct. Here I don't think iso- counts as a prefix, it's part of the ligand's original name. Would you happen to know whether this alphabetical system is the same for writing out formulas? Or can we just write the ligands randomly?
- Sat Dec 07, 2019 10:49 pm
- Forum: Conjugate Acids & Bases
- Topic: 6C.17
- Replies: 2
- Views: 226
Re: 6C.17
For this question, they specifically wanted you to look at the provided table, understanding that if pK b is lower then the substance is a stronger base. The given values are pretty close, so I don't think they'll give us a problem like that without giving us the K value. For the questions dealing w...
- Sat Dec 07, 2019 5:33 pm
- Forum: Bronsted Acids & Bases
- Topic: HW 6.21
- Replies: 3
- Views: 391
Re: HW 6.21
The reply is showing hydrogen bonding, not a Bronsted acid-base reaction. That said, I'm wondering the same thing; the solution says only N can accept protons that way, but I'm wondering why the double bonded O's don't do it as well.
- Sat Dec 07, 2019 2:41 am
- Forum: Lewis Acids & Bases
- Topic: About 6A.17
- Replies: 1
- Views: 94
About 6A.17
I'm having trouble figuring out whether different oxides are acidic, basic, or amphoteric. Can someone help me figure out what to look for to decide each case?
- Sun Dec 01, 2019 7:30 pm
- Forum: Calculating the pH of Salt Solutions
- Topic: konstant?
- Replies: 5
- Views: 551
Re: konstant?
Will we have to deal with any questions about Q vs K and le Chatelier's principle on the final?
- Sun Dec 01, 2019 7:28 pm
- Forum: Amphoteric Compounds
- Topic: Amphoteric Compound
- Replies: 2
- Views: 229
Re: Amphoteric Compound
Can a compound act as both a Bronsted and Lewis acid or base, or must it be one or the other? And if you have one, an example would be helpful.... Lewis acids/bases are a tad confusing to me still.
- Sun Dec 01, 2019 7:21 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: equation breakdown
- Replies: 2
- Views: 101
Re: equation breakdown
Wouldn't this work for any solution, essentially? Not just a strong acid? And if not, what different cases might we encounter?
- Sun Dec 01, 2019 7:18 pm
- Forum: Identifying Acidic & Basic Salts
- Topic: Final: Strong/ Weak Acids/Bases
- Replies: 11
- Views: 1541
Re: Final: Strong/ Weak Acids/Bases
The seven strong acids are: HCl, HBr, HI, HNO3, H2SO4, HClO4, and HClO3.
- Sun Dec 01, 2019 6:58 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Relative acidity
- Replies: 7
- Views: 546
Re: Relative acidity
At first I thought HF would be a stronger acid because of the electronegativity of the F atom. Where do you look at the size/polarizability of the anion, and where does electronegativity matter more?
- Sun Nov 24, 2019 11:52 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: lecture notes
- Replies: 2
- Views: 129
Re: lecture notes
The octahedral geometry's etymology is confusing me a bit; why is it "octa" if there's six? Is it because the shape forms two square pyramids attached base to base?
Re: d-metals
The "d" actually stood for the word "diffuse" in the beginning, a word that described the spectral lines of these atoms. The d-block elements are all transition metals.
- Sun Nov 24, 2019 9:46 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Central atom?
- Replies: 5
- Views: 353
Re: Central atom?
Does it have something to do with the electrons used for the bond being from d-orbitals, the fact that it’s only transition metals? I had OP’s question as well.
- Sun Nov 24, 2019 9:43 pm
- Forum: Naming
- Topic: Oxidation Numbers
- Replies: 4
- Views: 435
Re: Oxidation Numbers
Does the oxidation number have any bearing on how electrically positive or negative an atom is in a compound, such as in relation to a dipole?
- Sun Nov 24, 2019 9:38 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Coordination Sphere
- Replies: 5
- Views: 358
Re: Coordination Sphere
Why is six the maximum coordination number? (I vaguely remember this from lecture but I’m not sure whether it’s accurate. Is it some simple rule of geometry that dictates it, or is there something I’m missing here?
- Sun Nov 17, 2019 11:22 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Shapes
- Replies: 5
- Views: 310
Re: Shapes
It would most likely be linear, because the bonded atoms would be as far apart as possible. The lone pairs would be arrayed perpendicularly around the central atom in a triangle. One example of this scenario is XeF 2 , xenon difluoride. The electron pair geometry is actually trigonal bipyramidal, bu...
- Sun Nov 17, 2019 11:15 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Naming the Molecular Shapes
- Replies: 7
- Views: 523
Re: Naming the Molecular Shapes
What name is usually given to molecules like water, with sp4 hybridization but only 2 bonding atoms around the central atom? I used to say "bent" in high school, but the book is calling it "angular." Which name should I use?
- Sun Nov 17, 2019 11:09 pm
- Forum: Hybridization
- Topic: Hybridization
- Replies: 6
- Views: 288
Re: Hybridization
When molecules are created, the way they share electrons messes with the shape of each atom's orbitals, and what ends up happening is that the orbitals "hybridize" to create molecular orbitals, rather than behaving the way they do with unbonded atoms. However, since we haven't really talke...
- Sun Nov 17, 2019 11:05 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Instantaneous Dipole versus Induced Dipole
- Replies: 4
- Views: 360
Re: Instantaneous Dipole versus Induced Dipole
Does that mean that an induced dipole on one atom can be caused by an instantaneous dipole on another? And (just to clarify) the interaction that arises from this would be the dipole moment, a van der Waals interaction?
- Sun Nov 17, 2019 10:59 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: dipole moments
- Replies: 11
- Views: 666
Re: dipole moments
Dipole moments can be figured out based on electronegativity differences, and electronegativity has a strong correlation to the atom's position on the periodic table. So, yes, @ Leslie; but it's worth it to remember that the periodic table was based on periodic trends and not the other way around.
- Sun Nov 10, 2019 11:16 pm
- Forum: Electronegativity
- Topic: Atom size
- Replies: 22
- Views: 3335
Re: Atom size
Since the oxygen atom is actually smaller than the nitrogen, would it be less electronegative than the latter? Meaning, do these two not follow the "general" trend?
- Sun Nov 10, 2019 11:13 pm
- Forum: Dipole Moments
- Topic: Dipole Moment
- Replies: 6
- Views: 347
Re: Dipole Moment
Aren't van der Waals interactions still technically dipoles, just not permanent ones? I've seen them referred to as instantaneous dipoles. Also just to clarify, would the C=O bond be able to produce a dipole moment?
- Sun Nov 10, 2019 11:03 pm
- Forum: Octet Exceptions
- Topic: Antioxidants
- Replies: 9
- Views: 723
Re: Antioxidants
I don't exactly understand radicals; how do they form, and why? I was under the impression atoms usually have electrons in pairs. I do understand why they're so reactive comparatively, and why that would be harmful.
- Sun Nov 10, 2019 10:54 pm
- Forum: Bond Lengths & Energies
- Topic: Dissociation Energy
- Replies: 9
- Views: 415
Re: Dissociation Energy
I think it helps to think of energy as power to do something, rather than something tangible. It takes energy to break a bond, but energy is released when a bond is formed. That's because a bonded state is typically less energetic or "powerful" than an unbonded one, and therefore more stab...
- Sun Nov 10, 2019 10:50 pm
- Forum: Bond Lengths & Energies
- Topic: Bond lengths and strength
- Replies: 4
- Views: 188
Re: Bond lengths and strength
Double bonds are stronger than single bonds because the extra bonding electrons attract the positive nuclei more strongly than if there were only two. This also pulls them in closer together, making the bond shorter.
- Sun Nov 03, 2019 11:39 pm
- Forum: Lewis Structures
- Topic: Valence Electrons on Oxygen
- Replies: 3
- Views: 172
Re: Valence Electrons on Oxygen
I don't quite understand why chlorine has an expanded octet. Doesn't it have seven atoms in its outermost shell only?
- Sun Nov 03, 2019 11:37 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Formal charge
- Replies: 16
- Views: 947
Re: Formal charge
If they can't all be zero, then the next course of action is to find the configuration that allows for the lowest possible charge, whatever that might be.
- Sun Nov 03, 2019 11:18 pm
- Forum: Lewis Structures
- Topic: formal charge
- Replies: 6
- Views: 292
Re: formal charge
How do you guys decide whether or not a value for formal charge is too egregious? Usually I consider +/- 1 or 2 valid, and anything above that is sketch, but it's not really a set rule.
- Sun Nov 03, 2019 11:01 pm
- Forum: Resonance Structures
- Topic: Reasonable resonance structures?
- Replies: 1
- Views: 116
Re: Reasonable resonance structures?
Feel free to correct my understanding if this is wrong, but resonance structures are less of an absolute reality and more of a graphic representation of what happens. The "usual" arrangement of atoms will average out somewhat between the possible resonance structures, but the representatio...
- Sun Nov 03, 2019 10:56 pm
- Forum: Resonance Structures
- Topic: Showing resonance
- Replies: 8
- Views: 393
Re: Showing resonance
Can you elaborate on what that would look like? Maybe with a link. It sounds fine to me, but doesn't hurt to check.
- Sun Oct 27, 2019 11:14 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Memorizing the Equation
- Replies: 4
- Views: 170
Re: Memorizing the Equation
For the formal charge on each atom, I usually count up every lone pair electron and bond, and subtract the sum from the neutral number of electrons. I find understanding this conceptually an easier thing to do, as opposed to consulting the equation. After a while, doing this just became second nature.
- Sun Oct 27, 2019 11:06 pm
- Forum: Ionic & Covalent Bonds
- Topic: Resonance Structures
- Replies: 5
- Views: 148
Re: Resonance Structures
Is there a particular order the dots are written for each atom? Like, if I had an atom with 6 valence electrons, is there a specific way I must draw the electrons around the nucleus?
- Sun Oct 27, 2019 11:04 pm
- Forum: Ionic & Covalent Bonds
- Topic: 2A. 13 Question
- Replies: 5
- Views: 186
Re: 2A. 13 Question
This goes slightly outside the scope of the question, but do all elements follow the same pattern of removal of electrons? Like, would removing an electron from Ag work the same way as one from Cu save for being at one higher energy level?
- Sun Oct 27, 2019 6:02 pm
- Forum: Ionic & Covalent Bonds
- Topic: Ionic v Covalent Bond
- Replies: 3
- Views: 238
Re: Ionic v Covalent Bond
In addition to the above, generally a difference in electronegativity between 0 and 0.5 will be regarded as a nonpolar bond, while a difference between 0.5 and 2.0 will be seen as polar, hence why it is seen more as a sliding scale than a set distinction.
- Sun Oct 27, 2019 5:55 pm
- Forum: Resonance Structures
- Topic: Expanded Octets
- Replies: 4
- Views: 254
Re: Expanded Octets
So just to clarify, alkali metals and alkaline earth metals cannot make use of an expanded octet? Is it because their outermost shells are on a different energy shell than the rest of their electrons, and there's only 2 electrons max in that shell?
- Sun Oct 20, 2019 8:39 pm
- Forum: Photoelectric Effect
- Topic: Threshold Energy
- Replies: 7
- Views: 529
Re: Threshold Energy
Can something still be emitted with zero KE? It seems as though that would cause it to not move at all, and therefore not break free of the metal surface. However, it's possible I'm ascribing expectations of regular matter to the quantum level where they don't really apply.
- Sun Oct 20, 2019 8:37 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Orbitals
- Replies: 8
- Views: 335
Re: Orbitals
The reason why Scandium is written as [Ar] 3d1 4s2 is because after the 20th element in the periodic table (Calcium), the 3d orbitals have a slightly lower energy than the 4s orbitals. Therefore, you would start filling the 3d orbitals until it is full. The 4s orbital is filled first because it is ...
- Sun Oct 20, 2019 8:34 pm
- Forum: Properties of Electrons
- Topic: Spin
- Replies: 5
- Views: 229
Spin
I understand this is a very broad question, but I was wondering if someone could explain the concept of spin to me. Is it an intrinsic value ascribed to one electron, and can it change? How does it practically affect the atom? And, say, if an electron were to be added to an atom's outermost shell, w...
- Sun Oct 20, 2019 8:29 pm
- Forum: Properties of Electrons
- Topic: Subshell Exceptions
- Replies: 6
- Views: 507
Re: Subshell Exceptions
For chromium, the electron configuration would have looked like the following if it followed "normal" conventions: [Ar]4s 2 3d 4 And for copper: [Ar]4s 2 3d 9 However, the atom finds more stability when the d-subshells are half-filled or fully filled: Cr: [Ar]4s 1 3d 5 Cu: [Ar]4s 1 3d 10 T...
- Sun Oct 20, 2019 6:12 pm
- Forum: Einstein Equation
- Topic: Equation use
- Replies: 6
- Views: 372
Re: Equation use
The equation is used when referring to the energy of light/electromagnetic radiation, not with matter. v refers to the frequency of the light; if the problem gives you wavelength, you can use v=c/\lambda to find that frequency. Then you can use Planck's constant to find the energy of the particle. A...
- Sun Oct 13, 2019 4:16 am
- Forum: Photoelectric Effect
- Topic: Representation of electrons
- Replies: 2
- Views: 74
Re: Representation of electrons
Hi, thanks for the reply! Does that mean the electron actually follows that "trajectory," or is it a representation of the highest probability area of finding the particle? And since it's a standing wave, are those oscillations meant to represent oscillations in the electric field? I think...
- Sun Oct 13, 2019 4:09 am
- Forum: Properties of Light
- Topic: wavelike properties
- Replies: 6
- Views: 205
Re: wavelike properties
I think the original poster was asking "why" the wavelike properties exist- which is actually a good question, because a lot of people (myself included) have been parroting the words "wavelike properties" since lecture with no idea what that actually means. The evidence for parti...
- Sun Oct 13, 2019 3:58 am
- Forum: Properties of Light
- Topic: 1A.8
- Replies: 2
- Views: 321
Re: 1A.8
I can see how the dash in the second question might be offputting, but it looks like a misprint. Otherwise, this looks like a standard c = \lambda v problem to me. Was there something specific that was confusing in this question? It seems like the procedure is to find wavelength by isolating lambda ...
- Sun Oct 13, 2019 3:52 am
- Forum: DeBroglie Equation
- Topic: Concept of a wave
- Replies: 7
- Views: 544
Re: Concept of a wave
Also I believe wavelike properties are only demonstrated by objects that are extremely small. While light does exhibit wavelike properties, the equation cannot be applied towards it. So... does this mean objects with wavelike properties move in a wave? or what? That's the part I'm having trouble wi...
- Sun Oct 13, 2019 3:12 am
- Forum: Photoelectric Effect
- Topic: Representation of electrons
- Replies: 2
- Views: 74
Representation of electrons
From the last lecture, I did not exactly understand what Dr. Lavelle meant by electrons existing as a "circular standing wave." I understand that electron clouds are described in terms of "shells" of orbitals that have integral energy levels, but need help understanding the appli...
- Thu Oct 03, 2019 12:34 pm
- Forum: Empirical & Molecular Formulas
- Topic: Rounding [ENDORSED]
- Replies: 12
- Views: 831
Re: Rounding [ENDORSED]
I keep on seeing sig figs throughout this discussion. I am not knowledgeable about that term. Can someone explain to me what it means and how it helps with rounding? "Sig figs" is a shorthand term for "significant figures," a term in chemistry used to help gauge level of accurac...
- Thu Oct 03, 2019 12:11 pm
- Forum: Balancing Chemical Reactions
- Topic: Products of combustion reactions
- Replies: 7
- Views: 308
Re: Products of combustion reactions
If I recall correctly, incomplete combustion occurs in the presence of inadequate oxygen, but I'd appreciate if someone could check me on that. An example equation I found for the process, ft. methane: 4CH_{4} + 5O_{2} \rightarrow 2CO + 8H_{2}O + 2C Would this also possibly count as a side reaction?...
- Thu Oct 03, 2019 12:01 pm
- Forum: Balancing Chemical Reactions
- Topic: States of Matter in a Chemical Equation [ENDORSED]
- Replies: 11
- Views: 942
Re: States of Matter in a Chemical Equation [ENDORSED]
In what instances would a molecule be liquid as opposed to aqueous? What are some examples of molecules besides water that are in the state of pure liquid and not aqueous? An ionic compound will usually react in solution, so those are, for the most part, written as aqueous; NaCl, CuSO4, etc. Off th...
- Thu Oct 03, 2019 11:48 am
- Forum: Balancing Chemical Reactions
- Topic: Naming ionic/ molecular compounds
- Replies: 7
- Views: 519
Re: Naming ionic/ molecular compounds
If anyone is looking for a good list of inorganic naming conventions, I found this one very helpful, as it organizes ions by charge and groups together similar polyatomic ions, including the oxyanions: http://msmcraesscience.weebly.com/uploads/5/1/4/4/5144948/ap_chemistry_ion_sheet_--_chemical_nomen...
- Thu Oct 03, 2019 11:32 am
- Forum: Properties of Light
- Topic: Relationship Between Velocity and Wavelength
- Replies: 6
- Views: 476
Re: Relationship Between Velocity and Wavelength
In terms of the original question you asked - the relationship between velocity and wavelength for light is given by this equation: V = f\lambda Where V is the velocity of the wave in meters per second, \lambda (lambda) is the wavelength in meters, and f is the frequency, or cycles per second. I bel...