Search found 104 matches
- Sat Mar 14, 2020 9:41 am
- Forum: First Order Reactions
- Topic: Pseudo First-Order Reaction?
- Replies: 2
- Views: 232
Re: Pseudo First-Order Reaction?
Math wise, I do not believe that a pseudo first-order reaction differs from a regular one, but I believe, like with water, having a concentrated solution means that there is a much higher concentration of C12H22O11 in a given solution than H2O, so your rate law only takes into account H2O, since tha...
- Sat Mar 14, 2020 9:37 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Test 2 on Standard Cell Potential
- Replies: 6
- Views: 420
Re: Test 2 on Standard Cell Potential
For standard Gibbs Energy, you just use -nFE. And for knowing which one is the cathode and anode, you have to know the standard E values for both so you can determine which one is lower and thus the anode.
- Sat Mar 14, 2020 9:30 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Concentration Cell
- Replies: 3
- Views: 243
Re: Concentration Cell
Yes, the anode is always the one with the lower concentration.
- Sat Mar 14, 2020 9:27 am
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: intermediates
- Replies: 8
- Views: 541
Re: intermediates
Intermediates are a necessary part of the reaction, as the reactants don't necessarily just form into the products in one step so intermediates are formed and used up within reactions. However, they do not show up in the products.
- Sat Mar 14, 2020 9:21 am
- Forum: Calculating Work of Expansion
- Topic: Increase/Decrease
- Replies: 6
- Views: 449
Re: Increase/Decrease
Expansion usually causes an increase in work, as the volume is increasing against an opposing pressure.
- Sat Mar 07, 2020 7:24 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: 7A.15
- Replies: 3
- Views: 271
Re: 7A.15
Yes, because C is zero order, its concentration doesn't matter. So when comparing experiments 1 & 4, where the only concentration changing is that of C, because the rate does not change you can presume that change in [C] has no effect on the rate so it is not involved in the rate law.
- Sat Mar 07, 2020 7:20 pm
- Forum: First Order Reactions
- Topic: First Order Integrated Rate Laws
- Replies: 1
- Views: 161
Re: First Order Integrated Rate Laws
I believe it may be the way that ln works with negatives, since -ln([A]t/[A]0) would be equivalent to ln([A]0/[A]t). So the equation would go from [A]t=[A]0*(e^(-kt)) to [A]t/[A]0 = e^-kt to ln([A]t/[A]0) = -kt to t = ln([A]0/[A]t)/k.
- Sat Mar 07, 2020 7:15 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: 7C.7
- Replies: 3
- Views: 287
Re: 7C.7
Since the first step is pointed out to be the slowest, the rate law for that reaction determines the rate law for the entire reaction. Thus rate = k[NO][BR2] would be the rate law, not the rate law for the whole reaction.
- Sat Mar 07, 2020 12:08 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: temperature and k
- Replies: 5
- Views: 400
Re: temperature and k
Qualitatively endothermic reactions increase K when temperature increases while exothermic reactions lower K when temperatures increase, and the opposite when temperatures decrease. You can use the Van't Hoff equation to figure out how much exactly K values change when temperatures change.
- Sat Mar 07, 2020 11:52 am
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: How to calculate for n
- Replies: 7
- Views: 575
Re: How to calculate for n
By looking at the redox equations, you can find n by looking at the amount of electrons transferred, like Cu ---> Cu2+ + 2e-. In this case n=2 since 2 electrons are being transferred.
- Sat Mar 07, 2020 11:37 am
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: finding n in G=-nFE
- Replies: 15
- Views: 974
Re: finding n in G=-nFE
For example in a redox eq like Cu2+ + 2e- ---> Cu, n would be 2 since 2 electrons sre being transferred.
- Wed Feb 26, 2020 10:56 pm
- Forum: Balancing Redox Reactions
- Topic: OH- in Basic Solutions
- Replies: 6
- Views: 416
Re: OH- in Basic Solutions
You can add OH- after adding your protons so that the OH- and H+ cancel out in order to form H20.
- Wed Feb 26, 2020 10:55 pm
- Forum: Balancing Redox Reactions
- Topic: Oxidation or Reduction
- Replies: 2
- Views: 209
Re: Oxidation or Reduction
It would probably be oxidation as the half-reaction would look like 3I- --> I3- + 2e-, so electrons are lost. However, I am not completely sure if this is how this reaction would work.
- Wed Feb 26, 2020 10:49 pm
- Forum: Balancing Redox Reactions
- Topic: 6N.5
- Replies: 2
- Views: 247
Re: 6N.5
You can figure that the Cl would have a charge of -1 because it is in the 2nd last row of the periodic table. So Cl2 would have a total charge of -2, meaning that Hg2 would have to have a charge of +2 in order to keep Hg2Cl2 neutral and Hg would have a charge of +1.
- Wed Feb 26, 2020 10:42 pm
- Forum: Balancing Redox Reactions
- Topic: Balancing Hydrogens
- Replies: 2
- Views: 215
Re: Balancing Hydrogens
H+ seems to be more commonly used and doesn't involve oxygen, which may complicate things balancing wise.
- Wed Feb 26, 2020 10:34 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Midterm 6B
- Replies: 3
- Views: 273
Re: Midterm 6B
Essentially, this problem is asking for which equation would cause the least entropy so that G and H are similar. Entropy changes quite significantly when phases change, so the equation with the least entropy change would be the one with the solids on both sides.
- Thu Feb 20, 2020 6:35 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: units for entropy with Boltzmann's constant
- Replies: 2
- Views: 345
Re: units for entropy with Boltzmann's constant
I believe that boltzmann's constant is already in J/K, so I would assume that because the equation involves ln W, the units of W are not involved in calculations, thus leaving the units of boltzmann's constant, J/K, the same for the product.
- Thu Feb 20, 2020 6:29 pm
- Forum: Ideal Gases
- Topic: When to use equation
- Replies: 9
- Views: 693
Re: When to use equation
You would probably need to know either one of the initial or final mole values, and figure out what changes out of pressure, volume and temperature to figure out how your mole amount has changed.
- Thu Feb 20, 2020 6:27 pm
- Forum: Balancing Redox Reactions
- Topic: Oxidation number of Ozone
- Replies: 10
- Views: 690
Re: Oxidation number of Ozone
Yes, O3/ozone has an oxidation number of zero, its formal charge is zero as well.
- Thu Feb 20, 2020 6:17 pm
- Forum: Balancing Redox Reactions
- Topic: oxidizing and reducing agents
- Replies: 3
- Views: 239
Re: oxidizing and reducing agents
I believe so because one of the Cls are involved in the HClO reaction, which increases the oxidation number from 0 to +1, and the other Cl is involved in the Cl- reaction, which decreases the oxidation number from 0 to -1.
- Thu Feb 20, 2020 6:03 pm
- Forum: Balancing Redox Reactions
- Topic: Balancing Redox Reactions
- Replies: 5
- Views: 296
Re: Balancing Redox Reactions
It shouldn't matter where they are placed in the equation, but I suppose that the solutions manual put them at the end simply because they are not as important as the reactants and products in the reducing and oxidizing half-reaction if that makes sense. I would highly doubt that the test graders wo...
- Thu Feb 13, 2020 2:43 am
- Forum: Student Social/Study Group
- Topic: Notes from 2.10.20
- Replies: 3
- Views: 234
Re: Notes from 2.10.20
The lecture that day was simply on past exam questions, going over questions on topics like equilibrium, acids and bases, and thermodynamics/chem.
- Thu Feb 13, 2020 2:40 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Spontaneous
- Replies: 23
- Views: 1130
Re: Spontaneous
A reaction that is spontaneous will have a negative Gibbs free energy, while a reaction that has a Gibbs free energy is in equilibrium.
- Thu Feb 13, 2020 2:38 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: change in Kc
- Replies: 5
- Views: 389
Re: change in Kc
If you reverse the reaction, then Kc becomes 1/Kc. If you multiply the reaction by a constant, Kc equals Kc^x, where x is that constant.
- Thu Feb 13, 2020 2:37 am
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: adiabatic
- Replies: 19
- Views: 982
Re: adiabatic
An adiabatic process transfers no heat, and a diabatic process transfers heat
- Thu Feb 13, 2020 2:34 am
- Forum: Calculating Work of Expansion
- Topic: Positive or negative work
- Replies: 15
- Views: 2116
Re: Positive or negative work
When work is done on the system, it is positive, and when the system does work on its surroundings, it is negative.
- Fri Feb 07, 2020 2:25 pm
- Forum: Phase Changes & Related Calculations
- Topic: 4.1
- Replies: 3
- Views: 64
Re: 4.1
They are most likely given in one of the tables in Chapter 4. However, on tests/midterm those values should be given if needed to solve a problem. So if a phase change is involved in figuring out the enthalpy of fusion and vaporization those values represent the amount of enthalpy required to change...
- Fri Feb 07, 2020 2:22 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: state occupation of phases
- Replies: 7
- Views: 265
Re: state occupation of phases
Solids and liquids have less energy, so they are more tightly packed and thus take up less space than gases, which have more energy and are liable to move around more.
- Fri Feb 07, 2020 2:20 pm
- Forum: Student Social/Study Group
- Topic: Any Worksheets from UA/TA/etc?
- Replies: 14
- Views: 602
Re: Any Worksheets from UA/TA/etc?
Lyndon posted a Chem Community page titled Pizza Rolls, which should have a helpful practice worksheet up sometime in the evening today.
- Fri Feb 07, 2020 2:16 pm
- Forum: Phase Changes & Related Calculations
- Topic: Heating Curve
- Replies: 3
- Views: 271
Re: Heating Curve
The slope of the heating curve is the same as the heat capacity, so if the curve is steep, then the heat capacity is higher, while if the curve is flatter, the heat capacity is lower.
- Fri Feb 07, 2020 2:11 pm
- Forum: Calculating Work of Expansion
- Topic: Difference in Wirr and Wrev
- Replies: 4
- Views: 222
Re: Difference in Wirr and Wrev
Reversible processes can be thought of as the maximum work possible done by the gas, as external pressure constantly changes in order to match the internal pressure. Irreversible processes simply have constant external pressure, so the work done would not be as high.
- Thu Jan 30, 2020 9:59 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Ka and percent ionization problem
- Replies: 2
- Views: 180
Re: Ka and percent ionization problem
I think in this case percent ionization would simply be 2.344 * 10^-3/(0.010), since it is usually concentration of acid ionized/initial acid concentration or in this case [F-]/[HF].
- Thu Jan 30, 2020 9:54 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Midterm Material
- Replies: 13
- Views: 660
Re: Midterm Material
I would assume chemical equilibrium, acids and bases, thermochemistry and possibly some thermodynamics as well, based on how far we get in lecture before the midterm. Based on last quarter in Chem 14A, there are likely to be plenty of review sessions for different topics and a big review session bas...
- Thu Jan 30, 2020 9:50 pm
- Forum: Phase Changes & Related Calculations
- Topic: phase change from liquid to vapor
- Replies: 8
- Views: 304
Re: phase change from liquid to vapor
The steam and water can have the same temperature but the steam would carry more energy in the form of heat since it takes energy to drive a phase change from liquid to gas. Assuming that a burn would be stronger based on the energy it transfers onto skin, the steam would have a stronger burn.
- Thu Jan 30, 2020 9:49 pm
- Forum: Phase Changes & Related Calculations
- Topic: phase change heat supplied
- Replies: 3
- Views: 132
Re: phase change heat supplied
Essentially, when a liquid turns to gas, the bonds between atoms must be broken in order to become gas, which would presumably take a lot more heat than turning solids to liquid, which don't completely break the bonds but make them weaker.
- Thu Jan 30, 2020 9:46 pm
- Forum: Calculating Work of Expansion
- Topic: w=-P∆V
- Replies: 2
- Views: 115
Re: w=-P∆V
In the book, it says that w = -P∆V when the external pressure is constant, so presumably if the irreversible process involves constant external pressure then yes. It wouldn't be used for reversible processes, as those use w = -nRTln(V2/V1).
- Thu Jan 23, 2020 3:09 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: pKa to Kb
- Replies: 12
- Views: 548
Re: pKa to Kb
So the simplest way would be to find Pkb using the equation 14=pka+pkb. Once you find your pkb, you can use it to find kb using 10^-pkb.
- Thu Jan 23, 2020 3:04 pm
- Forum: Phase Changes & Related Calculations
- Topic: Steam?
- Replies: 8
- Views: 291
Re: Steam?
Essentially steam carries more energy as it takes a lot of energy to transition from liquid to vapor. So while they may have the same temperature, steam will very likely have a higher heat content due to the heat of vaporization as you mention.
- Thu Jan 23, 2020 3:02 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Ka correlation to strength of an acid
- Replies: 30
- Views: 2128
Re: Ka correlation to strength of an acid
The Ka is basically the measure of how much something dissociates, so if you have a larger Ka then you know more H3O+ will form, giving you a stronger acid. On the other hand, a lower pKa is a sign of a stronger acid.
- Thu Jan 23, 2020 3:00 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Strong/weak acids & bases
- Replies: 14
- Views: 892
Re: Strong/weak acids & bases
For the most part, in this section, we mostly work with weak acids and such since they are best suited for equilibrium type problems. However, it would probably be good to have a general idea of common strong acids just so you won't get blindsided if they come up on the test. However, it shouldn't b...
- Thu Jan 23, 2020 2:58 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Hydroxide/Hydronium Ions
- Replies: 2
- Views: 62
Re: Hydroxide/Hydronium Ions
So you can solve for hydroxide/hydronium ion concentration using the other concentration by using the fact that 1.0*10^-14 = [H30+][OH-]. Because you know that the equilibrium constant for water, Kw, is 1.0*10^-14, you can thus solve for either concentration by dividing Kw by the ion concentration t...
- Tue Jan 14, 2020 11:52 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Thermodynamically Stable?
- Replies: 3
- Views: 125
Re: Thermodynamically Stable?
A thermodynamically stable thing tends to keep its form well. So when comparing Cl2 and F2, we simply look to see which of the two has a smaller equilibrium constant. Since Cl2 does, it is more thermodynamically stable, since a smaller ratio of Cl2 dissociates into Cl atoms compared to F2 and F atoms.
- Tue Jan 14, 2020 11:49 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: 5.33
- Replies: 6
- Views: 318
Re: 5.33
The breaking of a bond requires energy to do, so increasing the temperature, and as a result increasing the energy, of the reaction would cause more X to form.
- Tue Jan 14, 2020 11:47 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 5.35
- Replies: 1
- Views: 76
Re: 5.35
I got something similar to you as well when doing 5.35, I think its simply due to the fact that in the solutions manual they use 18 Kpa instead of 17.5 Kpa, since your answer is so close to the answer they give.
- Tue Jan 14, 2020 11:43 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: What is K
- Replies: 6
- Views: 208
Re: What is K
K is pretty much a more ambiguous term than either Kc or Kp. Often times when K is used, it should be pretty apparent whether Kc or Kp should be used, like with Kp when you are given partial pressures or Kc when there are no gas-phase reactants or products.
- Tue Jan 14, 2020 11:40 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: ICE Chart
- Replies: 5
- Views: 315
Re: ICE Chart
Most times you can tell what direction a reaction will go based on the initial concentrations you are given. If you are only given that you start off with reactants, then the reaction will surely go to the right. If given only products initially, then the reaction will go to the left. If you start w...
- Wed Jan 08, 2020 1:20 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: No Solvent Concentration in the Calculating Equilibrium Constant
- Replies: 4
- Views: 273
Re: No Solvent Concentration in the Calculating Equilibrium Constant
The activity level for a solvent is equal to or very close to being equal to 1, so it doesn't affect the equilibrium constant.
- Wed Jan 08, 2020 1:06 am
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: How to make ICE box
- Replies: 17
- Views: 1215
Re: How to make ICE box
Since change is often unknown in problems using the ICE box, we usually attribute a variable to the amount of change in products and reactants, oftentimes x. Using stoichiometric analysis, like in an example equation 2 A + 3 B <--> C, the change would be -2x for A, -3x for B, and +x for C. Then use ...
- Wed Jan 08, 2020 1:01 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Example in 5I.3
- Replies: 1
- Views: 69
Re: Example in 5I.3
I think that in this problem it is assumed that we are working with partial pressures as the problem is looking for the partial pressures of the gases in the mixtures. However, in other problems where it doesn't say whether or not you are specifically looking for pressure/concentration, it would be ...
- Tue Jan 07, 2020 12:20 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Textbook question 5G.9
- Replies: 2
- Views: 95
Re: Textbook question 5G.9
C would have different values for PO2/PO3 for the two samples since only the equilibrium constant, which would be PO2^3/PO3^2, would have the same value between the two samples as it is a constant. It's kind of like a trick question to see if you can recognize that PO2/PO3 is not the equilibrium con...
- Tue Jan 07, 2020 12:15 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Hw Problem G2
- Replies: 5
- Views: 354
Re: Hw Problem G2
It would be true as the equilibrium concentrations would be the same regardless of whether the reaction starts with pure reactants/products since the ratio between the two concentrations is equal to the equilibrium constant, which doesn't change.
- Sun Dec 08, 2019 10:44 am
- Forum: Biological Examples
- Topic: Heme complex
- Replies: 5
- Views: 343
Re: Heme complex
What is the biological importance of the heme complex? The importance of the heme complex, which is a complex of Fe and a tetradentate porphyrin ligand, is that it is part of the protein myoglobin and is responsible for binding to O2 through its Fe cation, since it has one available space to after ...
- Sun Dec 08, 2019 2:01 am
- Forum: Conjugate Acids & Bases
- Topic: 6A.3
- Replies: 2
- Views: 284
Re: 6A.3
Pretty much for all of the parts, there is an acid that reacts with water to release its H+ proton and thus form the conjugate base and a hydronium ion H3O+.
- Sun Dec 08, 2019 1:59 am
- Forum: Hybridization
- Topic: Marshmallow Hybridization Problem
- Replies: 3
- Views: 404
Re: Marshmallow Hybridization Problem
Oxygen is not necessarily gonna be sp2 or sp3 both times even though they are in the same molecule. Hybridization pretty much equates to how many zones of lone pairs/bonds are on the atom. So the top oxygen is sp2 since it has 1 bond and 2 lone pairs while the other oxygen is sp3 since it has 2 bond...
- Sun Dec 08, 2019 12:53 am
- Forum: Industrial Examples
- Topic: Cisplatin Vs. Transplatin
- Replies: 7
- Views: 1399
Re: Cisplatin Vs. Transplatin
cisplatin is specifically used for chemotherapy and stopping cell division due to its cis orientation. Essentially, because cisplatin has both of its Cl's on one side, the two Cl's can bond to a close together guanine pair. It is bidentate since the two Cl's are on the same side, so cisplatin can st...
- Wed Dec 04, 2019 1:27 am
- Forum: Lewis Acids & Bases
- Topic: Strong Acids
- Replies: 6
- Views: 372
Re: Strong Acids
A strong acid is one that pretty much completely disassociates into a proton and anion in solution. One example would be HCl, which just becomes H+ and Cl- in solution.
- Wed Dec 04, 2019 1:25 am
- Forum: General Science Questions
- Topic: Practice with pH calculations
- Replies: 1
- Views: 182
Re: Practice with pH calculations
Since you are given the concentration of H+, it is pretty simple to calculate pH. The equation for pH is just -log[H+], so in this case it would be -log[10^-5] which is equal to 5.
- Sun Dec 01, 2019 11:26 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: pOH
- Replies: 3
- Views: 111
Re: pOH
pOH would be like pH, in that its a measure of concentration. So in problems where a pOH or a concentration of OH- molecules is given, it is likely you will have to use the equation to find pOH to solve for that problem. To find pOH, use the equation pOH = -log[OH-], using the concentration of OH- i...
- Sun Dec 01, 2019 11:20 pm
- Forum: Lewis Acids & Bases
- Topic: Difference between Lewis and Bronsted
- Replies: 4
- Views: 274
Re: Difference between Lewis and Bronsted
The Lewis definition states that an acid is an electron acceptor while a base is an electron donor. The Bronsted definition states that an acid is a proton donor, while a base is a proton acceptor.
- Sun Dec 01, 2019 11:07 pm
- Forum: Properties & Structures of Inorganic & Organic Bases
- Topic: Recognizing Bases in Chemical Equations
- Replies: 2
- Views: 157
Re: Recognizing Bases in Chemical Equations
A lot of the strong bases are alkaline earth metal or alkali metal hydroxides, examples including KOH, NaOH, CsOH, (Ca(OH)2)), and so on. This may be why it seems like most bases have OH or O in them, but it is not necessarily a requirement. It does seem to be a trend among strong bases, however.
- Sun Dec 01, 2019 11:03 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: J.11
- Replies: 2
- Views: 198
Re: J.11
Since HCl is a strong acid, the ions that make it up disassociate completely in water, so the image showing individual H+ and Cl- ions would be the most accurate. A weak acid, in contrast, would mostly show the acid in question floating around, with a few disassociated ions floating around, as weak ...
- Sun Dec 01, 2019 11:01 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Amphoteric compounds
- Replies: 4
- Views: 150
Re: Amphoteric compounds
Essentially, amphoteric compounds can act as both an acid or a base. Water is a classic amphoteric compound as it can donate one of its H+ to become OH- or accept H+ to become H3O+.
- Sun Nov 24, 2019 12:59 am
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Coordination compounds
- Replies: 2
- Views: 170
Re: Coordination compounds
"Coordination compounds are molecules that poses one or multiple metal centers that is bound to ligands (atoms, ions, or molecules that donate electrons to the metal). These complexes can be neutral or charged. When the complex is charged, it is stabilized by neighboring counter-ions. A complex...
- Thu Nov 21, 2019 1:17 am
- Forum: Hybridization
- Topic: for test 2
- Replies: 7
- Views: 234
Re: for test 2
The most recent concept in the lecture that we will have to study for test 2 are the sigma and pi bonds.
- Thu Nov 21, 2019 1:16 am
- Forum: Lewis Structures
- Topic: I3- Lewis Structure
- Replies: 2
- Views: 260
Re: I3- Lewis Structure
I believe that the first lewis structure would work best from a formal charge perspective, as I generally only has a single bond to keep its formal charge as zero. The I in the middle would have a formal charge of -1 having two single bonds, which would be appropriate as I3 has a negative charge.
- Thu Nov 21, 2019 1:07 am
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: Carbon Monoxide
- Replies: 3
- Views: 479
Re: Carbon Monoxide
If it were carbon dioxide, the molecule would be nonpolar because the molecule would be linear, thus meaning the dipole moments of the two oxygens would be canceled. However, the carbon monoxide would still be polar since the less electronegative carbon has a more positive charge while the more elec...
- Wed Nov 20, 2019 12:56 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: cis versus trans Lewis structure
- Replies: 1
- Views: 235
Re: cis versus trans Lewis structure
Essentially, a trans molecule will have the same atoms in the bonded molecules on opposite sides, while a cis molecule will have the same atoms in the bonded molecules on the same sides. Thus, a trans molecule will have the dipole moments of the atoms cancelled out, while a cis molecule will not hav...
- Thu Nov 14, 2019 7:07 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Quick Question
- Replies: 4
- Views: 403
Re: Quick Question
No, the l would equal 1 for the 4pz state, since p corresponds to l=1. Generally, s is l=0, p is l=1, d is l=2, and f is l=3.
- Thu Nov 14, 2019 7:04 pm
- Forum: Resonance Structures
- Topic: Explanation of bonds
- Replies: 3
- Views: 177
Re: Explanation of bonds
I would assume that the explanation would probably have to include the effect of the electron to really get at the heart of why the double bond is shorter than a single bond. A good way to explain it would be that since double bonds have more bonding electrons involved than single bonds, there is a ...
- Thu Nov 14, 2019 7:01 pm
- Forum: Dipole Moments
- Topic: Polarity
- Replies: 6
- Views: 295
Re: Polarity
From my understanding, polarity occurs when the electrons of a molecule aren't distributed equally. An easy way to figure out whether a molecule is polar is to see if its shape is non-symmetric, so H20 would be polar since it is a bent molecule, while BeCl2 is nonpolar since it is a linear molecule.
- Thu Nov 14, 2019 6:50 pm
- Forum: Electronegativity
- Topic: Increasing/Decreasing Electronegativity
- Replies: 14
- Views: 2648
Re: Increasing/Decreasing Electronegativity
Electronegativity increases across a period. Electronegativity is a measure of an element's ability to attract electrons, so those to the right of the period are able to attract electrons more easily as they need electrons to fill their valence shells and thus are the most electronegative.
- Wed Nov 13, 2019 9:44 pm
- Forum: Ionic & Covalent Bonds
- Topic: 2D #11
- Replies: 3
- Views: 206
Re: 2D #11
Polarizing power also becomes stronger the smaller an atom is since the effective nuclear charge has a stronger effect, while polarizability becomes higher when an atom is larger since its electrons are more easily affected due to a larger distance from the nucleus.
- Tue Nov 05, 2019 10:19 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Heisenberg Problem
- Replies: 3
- Views: 365
Re: Heisenberg Problem
So Heisenberg's uncertainty equation is basically (uncertainty in position)*(uncertainty in momentum)=h/4pi. Since we have uncertainty in speed, +- 1 m/s, we can find uncertainty in momentum by multiplying it by the mass of an electron, 9.11*10^-31. Then we can divide that value from both sides to g...
- Tue Nov 05, 2019 10:15 pm
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Sr 2+ or Rb 1+
- Replies: 6
- Views: 520
Re: Sr 2+ or Rb 1+
Rb has the larger Atomic Radius, Consequently Sr has a higher polarizing power. Larger radius=more polarizability smaller radius=more Polarizing Power... how does Rb have the larger atomic radius? A good way of looking at the atomic radius is that when going further down a period, elements have mor...
- Tue Nov 05, 2019 10:06 pm
- Forum: Properties of Light
- Topic: Using de Broglie's wavelength to find frequency
- Replies: 1
- Views: 153
Re: Using de Broglie's wavelength to find frequency
I don't believe you can find the frequency directly using de Broglie's, at least not using c=wavelength*frequency. However, it may be an intermediate step in a photoelectric effect problem, where you are given wavelength of an ejected photon, which you use to find the velocity of the photon, and the...
- Tue Nov 05, 2019 10:03 pm
- Forum: Electronegativity
- Topic: Electronegativity Chart
- Replies: 5
- Views: 480
Re: Electronegativity Chart
We may be given electronegativity numbers for some of the elements involved in the problem if any do arise in the midterm, however, it would probably be in your best interest to generally know the trends for electronegativity, and other periodic trends as well. In the case of electronegativity, it g...
- Tue Nov 05, 2019 9:58 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Dino nuggets 11b
- Replies: 3
- Views: 292
Re: Dino nuggets 11b
Essentially, you can tell whether an electron/photon will be emitted or absorbed based on whether n goes up or down. E for an electron is measured negatively, meaning that when n approaches infinity, E approaches 0. When n=1, the lowest quanta it can be, E becomes -hR/n^2, the most negative value E ...
- Wed Oct 30, 2019 10:20 pm
- Forum: Resonance Structures
- Topic: 2B. 3
- Replies: 2
- Views: 130
Re: 2B. 3
In the answer key it doesn't show any resonance structures for c and d so I guess they are not needed for the problem.
- Wed Oct 30, 2019 10:07 pm
- Forum: Resonance Structures
- Topic: Delocalized Electrons
- Replies: 4
- Views: 188
Re: Delocalized Electrons
From what I understand, resonance structures are less how the bonds are really like in real life but more the best representation of the idea of delocalized electrons within a bond/molecule. So instead of having different bond lengths between double and single bonds within the resonance structures, ...
- Wed Oct 30, 2019 10:03 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Nodes
- Replies: 1
- Views: 98
Re: Nodes
For the p orbitals, the nodes exist on the x-plane, y-plane, and z-plane and for the d orbitals, the nodes exist on the xy, xz, yz, x^2-z^2, and z^2 planes, and occur when the wave function goes from positive to negative or vice versa, as that is where the function, the probability of electron densi...
- Wed Oct 30, 2019 9:50 pm
- Forum: Student Social/Study Group
- Topic: Will different midterm review sessions cover the same material?
- Replies: 8
- Views: 376
Re: Will different midterm review sessions cover the same material?
I believe that generally the same topics will be reviewed in the same topic review sections, i.e. atomic spectra, photoelectric effect, etc. in Early Quantum Review sections, but the lecturing styles/examples given by the TAs may be different depending on who is leading the sessions. So if you are e...
- Tue Oct 29, 2019 12:01 pm
- Forum: Ionic & Covalent Bonds
- Topic: Homework Question 2C3
- Replies: 2
- Views: 181
Re: Homework Question 2C3
I believe that at least some of the conventions for nomenclature are contained in Fundamental section D. I would assume that we wouldn't need to know it that well or that it will be given since we weren't assigned this reading, but may still be helpful to know for the future.
- Tue Oct 22, 2019 12:30 pm
- Forum: Properties of Light
- Topic: Memorizing light
- Replies: 4
- Views: 142
Re: Memorizing light
It may be useful to generally know the order of common waves, like the fact that ultraviolet is lower wavelength than visible light for things like Lyman series or infrared is higher wavelength than visible light. It probably won't be super important to remember though.
- Tue Oct 22, 2019 12:26 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Orbitals / Quantum Numbers
- Replies: 3
- Views: 117
Re: Orbitals / Quantum Numbers
p represents the specific subshell l=1, the same way that s is l=0, d is l=2, or f=3. So if you are given 6p, you know that the l is 1 due to the presence of the p.
- Tue Oct 22, 2019 12:24 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: G-subshell
- Replies: 3
- Views: 187
Re: G-subshell
I believe at n=5 is the minimum value of n that has a g-subshell.
- Tue Oct 22, 2019 12:21 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Orbitals
- Replies: 5
- Views: 262
Re: Orbitals
You are correct, the possible values for l should be 0-5, as n=6 shouldn't be an exception. Maybe you were reading the answers for another problem as this one is 1D.14, which shouldn't have an answer in the solutions manual.
- Tue Oct 22, 2019 10:21 am
- Forum: Quantum Numbers and The H-Atom
- Topic: 1D. 23)
- Replies: 5
- Views: 285
Re: 1D. 23)
Also for orbitals in general, n is the energy level, l is the subshell and ml is the orbitals within the subshell. So if you are only given n=2 for example, you would know that l can either be 0 or 1, or s or p, since l is 0, ... , n-1. For l, 0/s has 1 orbital, 1/p has 3 orbitals, 2/d has 5, and 3/...
- Thu Oct 17, 2019 1:47 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Radiation Type
- Replies: 5
- Views: 169
Re: Radiation Type
In our discussion, I believe the TA said that the most important thing to note would be that visible light occurs at 400-700 nm. Personally I think it would be good to know that ultraviolet occurs below 400 nm and infrared occurs above 700nm for random things like Lyman series, and it might be helpf...
- Thu Oct 17, 2019 1:44 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: 1D.25
- Replies: 2
- Views: 89
Re: 1D.25
Just for more info, l=0 is s, l=1 is p, l=2 is d, and l=3 is f. So when you have a certain energy level, let's say n=2, then the corresponding l values are 0 and 1, the values that are less than or equal to n-1. s has 1 corresponding orbital, p has 3, d has 5, and f has 7, and these corresponding or...
- Tue Oct 15, 2019 10:49 pm
- Forum: Properties of Light
- Topic: Homework 1A.15
- Replies: 1
- Views: 111
Re: Homework 1A.15
Based on the information given, the 102.6 nm, we know that emission is ultraviolet and thus initial energy level=1, indicative of the Lyman series. Given that we have a wavelength, we can find the frequency using c=frequency*wavelength and it turns out to be 2.922*10^15 s-1. Frequency = R(1/n1^2 - 1...
- Tue Oct 15, 2019 10:38 pm
- Forum: DeBroglie Equation
- Topic: Wavelength of Radiation
- Replies: 3
- Views: 140
Re: Wavelength of Radiation
Pretty much what you said, to find wavelength, you can simply use the value of frequency and the equation c=(wavelength)(frequency) to find wavelength.
- Tue Oct 15, 2019 10:29 pm
- Forum: SI Units, Unit Conversions
- Topic: Joules
- Replies: 2
- Views: 141
Re: Joules
The units for joules are kg*m^2/s^2. It is the unit for Energy, which is pretty much the force used times meters moved(I think), which would be mass times acceleration(m/s^2) times meters, leading to the units for joules. In chem, it would be used as a unit of energy for an electron or photon, for e...
- Mon Oct 07, 2019 6:30 pm
- Forum: Properties of Light
- Topic: Problem 1A.3c
- Replies: 2
- Views: 83
Re: Problem 1A.3c
I think that the "electric field" would be referring to the electric field waves that are oscillating. So c would be correct because when the frequency lowers, the field/waves would be "changing" more slowly at a given point since the waves simply don't oscillate as much per seco...
- Mon Oct 07, 2019 6:21 pm
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Test 1 [ENDORSED]
- Replies: 107
- Views: 17452
Re: Test 1 [ENDORSED]
I believe my TA told our discussion group that they would be providing like a printed exam and you would be writing directly onto that to answer, so probably no blue book/scantron needed.
- Mon Oct 07, 2019 6:17 pm
- Forum: Photoelectric Effect
- Topic: Potential Difference
- Replies: 3
- Views: 180
Re: Potential Difference
Not 100% sure either but I think it means that even though the kinetic energy is close to zero, the electron would still sort of be drift to the detector as the detector has a positive charge and the electron is negatively charged, thus attracting it towards the detector based on charge. I could be ...
- Mon Oct 07, 2019 6:14 pm
- Forum: Properties of Light
- Topic: Question 1A.3 c
- Replies: 5
- Views: 342
Re: Question 1A.3 c
I also wasn't 100% clear on this question, but I kinda took it to mean that since there aren't as many oscillations, the electrical field wouldn't change as quickly since it takes a longer time for each wave to oscillate. Not the most technical explanation but hopefully it kinda helps clear things up.
- Mon Oct 07, 2019 6:11 pm
- Forum: Properties of Light
- Topic: Photons
- Replies: 7
- Views: 294
Re: Photons
Technically, increasing the intensity would actually increase total energy, as there are simply more electrons being emitted. However, what intensity doesn't change is the amount of energy per photon/electron being emitted, as that depends on frequency only and is based on the equation E = hv.
- Mon Oct 07, 2019 6:08 pm
- Forum: Photoelectric Effect
- Topic: How much energy to remove one electron?
- Replies: 8
- Views: 228
Re: How much energy to remove one electron?
I would assume that the equation you would use in this situation would be 1/2mev^2 = Energy - workfunction. Given that you know both the velocity and the work function already, you can solve for energy needed by adding 1/2mev^2, where me is the mass of one electron, and the work function.
- Thu Oct 03, 2019 4:54 pm
- Forum: Molarity, Solutions, Dilutions
- Topic: Fundamentals #G25
- Replies: 2
- Views: 134
Re: Fundamentals #G25
The number of molecules in the solution after all of the dilutions would be the same, however, the question asks for the number of molecules in 10 ml of soln, which would be now a small percentage of the total volume due to the ninety dilutions. So in order to solve for this, what I did was find the...
- Mon Sep 30, 2019 11:39 pm
- Forum: Empirical & Molecular Formulas
- Topic: Net # of moles of gas produced, module question [ENDORSED]
- Replies: 3
- Views: 3480
Re: Net # of moles of gas produced, module question [ENDORSED]
I think that the word "combustion" in the problem allows you to infer the presence of oxygen gas in the equation. And with carbon monoxide, it is formed during incomplete combustion when there is not enough oxygen to form carbon dioxide, but I would guess that for simpler problems where in...