N represents the number of moles of electrons transferred. You are correct about the n in your first example, but for the second equation if the textbook uses n=2 it must be a typo. It should be 1.
Also, always remember to balance the half reactions before determining n.
Search found 94 matches
- Fri Mar 12, 2021 5:37 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: finding "n"
- Replies: 12
- Views: 712
- Fri Mar 12, 2021 5:30 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: When to use Platinum
- Replies: 14
- Views: 712
Re: When to use Platinum
If there is not already a conducting metal in the redox reaction, platinum is good to use. It is ideal for this because we do not want to add anything that will interfere with the redox reaction. Like gold, platinum is inert so it is resistant to oxidation.
- Fri Mar 12, 2021 5:19 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Units for Activation Energy
- Replies: 28
- Views: 1818
Re: Units for Activation Energy
It is joules per mole.
- Fri Mar 12, 2021 5:16 pm
- Forum: Second Order Reactions
- Topic: Sapling #12 Week9/10
- Replies: 7
- Views: 435
Re: Sapling #12 Week9/10
To find the order of the reaction see how the half life changes as the concentration changes. Then look at the different half life reactions and find which one reflects the relationship between concentration and half life of the data from your reaction.
- Fri Mar 12, 2021 4:49 pm
- Forum: First Order Reactions
- Topic: Sapling Week 9/10 #13
- Replies: 6
- Views: 368
Re: Sapling Week 9/10 #13
In this problem the first elementary reaction is in equilibrium (the half arrows is notation for equilibrium). At equilibrium, the forward rate law is equal to the reverse. Once you set them equal to one another, you can rearrange the terms to get an expression for [HClO] and substitute that into th...
- Sun Mar 07, 2021 2:09 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: cell notation
- Replies: 12
- Views: 671
Re: cell notation
It is standard for the anode to be on the left and cathode to be on the right. But remember that oxidation occurs at the anode and reduction occurs at the cathode.
- Sun Mar 07, 2021 2:04 pm
- Forum: Balancing Redox Reactions
- Topic: Balancing Redox
- Replies: 16
- Views: 779
Re: Balancing Redox
First you balance the half reaction. Then find the net charge on both sides and add the correct amount of e- on one side in order to balance the charge.
- Sun Mar 07, 2021 2:02 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Balancing half-reactions to find overall cell potential
- Replies: 6
- Views: 331
Re: Balancing half-reactions to find overall cell potential
E_cell = -ΔG/nF
Suppose you multiply the half reaction by two. Delta G will double, but so will n. This results in the same cell potential regardless of what coefficient you multiply by.
Suppose you multiply the half reaction by two. Delta G will double, but so will n. This results in the same cell potential regardless of what coefficient you multiply by.
- Sun Mar 07, 2021 1:52 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: What is the purpose of having a salt bridge?
- Replies: 16
- Views: 660
Re: What is the purpose of having a salt bridge?
If you allow the e- transfer in the cell, the reduced species will accumulate in the cathode and the oxidized species will accumulate in the anode. This leads to a buildup of charge which can inhibit e- transfer. If we want to maximize potential, we must neutralize the charge buildup. The salt bridg...
- Sun Mar 07, 2021 1:37 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: E vs E naught
- Replies: 36
- Views: 1437
Re: E vs E naught
E naught is under standard conditions, E does not have to be.
- Sat Feb 27, 2021 2:38 pm
- Forum: Balancing Redox Reactions
- Topic: sapling week 8 #18
- Replies: 4
- Views: 322
Re: sapling week 8 #18
The dot in Fe2O3•3H2O means that the 3H2O is bound to the Fe2O3 by weak chemical bonds. When you balance the equation you must think of Fe2O3•3H2O as one unit, so you must put a coefficient in front of it. Also, do not put parentheses or brackets around it because Sapling will not accept the answer ...
- Sat Feb 27, 2021 2:24 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: initial concentration is the same, but less than 1M
- Replies: 11
- Views: 600
Re: initial concentration is the same, but less than 1M
If they are the same E is zero. Here there is no potential because Q equals 1. The log or natural log of 1 is 0.
- Sat Feb 27, 2021 2:20 pm
- Forum: Balancing Redox Reactions
- Topic: Oxidation vs Reduction
- Replies: 30
- Views: 1212
Re: Oxidation vs Reduction
I remember because for reduction, the charge is being reduced/more negative; therefore, it gains electrons. Then I know oxidation is the opposite.
- Sat Feb 27, 2021 2:13 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Anode/Cathode in Concentration Cells
- Replies: 5
- Views: 472
Re: Anode/Cathode in Concentration Cells
Reduction occurs at the cathode and oxidation occurs at the anode. After you find which elements are losing and gaining e-, the cathode is the one gaining electrons and the anode is the one losing electrons.
- Sat Feb 27, 2021 2:03 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: n in ∆G = -nFE
- Replies: 80
- Views: 3664
Re: n in ∆G = -nFE
n refers to the number of moles of electrons being transferred. When you are presented with a redox reaction, you need to balance the reaction and find how many e- are being gained/lost. n should be the coefficient in front of e-.
- Sun Feb 21, 2021 12:37 pm
- Forum: Calculating Work of Expansion
- Topic: Positive vs. Negative Work
- Replies: 22
- Views: 811
Re: Positive vs. Negative Work
You are correct. When a system is doing work, such as expansion, it requires energy which it loses to its surroundings. When work is done it, the energy goes into the system, so the value for w would be positive.
- Sun Feb 21, 2021 12:35 pm
- Forum: Balancing Redox Reactions
- Topic: redox example from lec 17
- Replies: 5
- Views: 298
Re: redox example from lec 17
It is + 5e- because each of the 5 Fe2+‘s loses an electron and they become Fe3+. Now we have 5Fe3+ and 5e-, they have separated. The + does not mean it gained electrons. Also, the five is there because we have to balance the half reactions so that the redox reaction has the same charge on both sides.
- Sun Feb 21, 2021 12:27 pm
- Forum: Balancing Redox Reactions
- Topic: Cell/battery
- Replies: 26
- Views: 783
Re: Cell/battery
I think he said in lecture that they mean the same thing. So I will assume they are the same unless he says otherwise.
- Sun Feb 21, 2021 12:24 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Is thermal mugs an example of an isolated system?
- Replies: 38
- Views: 1832
Re: Is thermal mugs an example of an isolated system?
It is a good illustration of an isolated system, but it technically would be a closed system that allows minimal heat transfer to its surroundings. If you put a hot beverage in the thermos it will eventually cool, but slowly. However, if there is a thermos that is truly an isolated system, I would d...
- Sun Feb 21, 2021 12:19 pm
- Forum: Phase Changes & Related Calculations
- Topic: State Property
- Replies: 71
- Views: 2812
Re: State Property
Suppose I heat a system that starts at 25 degrees Celsius directly to 100 degrees Celsius. The change in temperature is 75. If I decide to heat the system from 25 to 120 and then I cool it to 100, the change is still 75. Regardless of what path I take to get the system from 25 to 100, the change wil...
- Sun Feb 14, 2021 11:04 am
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Entropy definition
- Replies: 37
- Views: 2058
Re: Entropy definition
Entropy is a measure of disorder. I visualize something that has high entropy as being spread out, like a gas. When there is high entropy there are many states that can be occupied. For low entropy, think of a crystal. All the particles have a definite arrangement in the lattice and do not have othe...
- Sun Feb 14, 2021 10:54 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Sapling #10 WK5/6
- Replies: 3
- Views: 2188
Re: Sapling #10 WK5/6
Once you determine the signs of ΔG and ΔS, look at the equation ΔG = ΔH - TΔS. Since ΔG is negative in this case, you have to determine which sign of ΔH keeps ΔG negative (also given the sign of ΔS).
- Sun Feb 14, 2021 10:43 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Sapling Question #16
- Replies: 8
- Views: 383
Re: Sapling Question #16
Since you are using values of ΔGf (standard) at 298 K (25C), temperature is already incorporated into the problem. All you need to do is take the sum of ΔGproducts and subtract from ΔGreactants.
- Sun Feb 14, 2021 10:32 am
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: week 5 and 6 sampling hw #7
- Replies: 5
- Views: 321
Re: week 5 and 6 sampling hw #7
We use the initial and final masses to find the mass of vapor. Then we use that mass to find the number of moles of vapor. Finally we divide the total energy supplied to the sample by the number of moles to get ΔHvap.
- Sun Feb 14, 2021 10:18 am
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: week 5 and 6 sampling hw #6
- Replies: 4
- Views: 275
Re: week 5 and 6 sampling hw #6
You can think of this problem as being composed of two separate events: the change in entropy from the change in volume and the change in entropy from the change in temperature. Use the entropy change equation nRln(V2/V1) for the volume change event. Then use the equation Cvln(T1/T2) for the change ...
- Sun Feb 07, 2021 11:02 am
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Spontaneous Process
- Replies: 4
- Views: 161
Re: Spontaneous Process
Yes, all spontaneous processes increase entropy.
- Sun Feb 07, 2021 10:57 am
- Forum: Calculating Work of Expansion
- Topic: q=-w
- Replies: 5
- Views: 161
Re: q=-w
One example could be the isothermal reversible expansion of an ideal gas. This is because the system system is doing work by expansion, losing energy. However, the expansion happens slow enough for the heat transfer to counter the energy list from work, so it stay at equilibrium.
- Sun Feb 07, 2021 10:53 am
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Work Definition
- Replies: 33
- Views: 959
Re: Work Definition
Work happens when something achieves distance by overcoming some other force (I think).
- Sun Feb 07, 2021 10:50 am
- Forum: Ideal Gases
- Topic: Sapling week 3/4 #15
- Replies: 7
- Views: 448
Re: Sapling week 3/4 #15
First used the mass of NaN3 and stoichiometry to determine the number of moles of N2 produced. Then find the volume of N2 using the ideal gas law. Finally to solve for work, you use w = -PΔV. Then convert to joules.
- Sun Feb 07, 2021 10:45 am
- Forum: Phase Changes & Related Calculations
- Topic: Boiling water
- Replies: 25
- Views: 2657
Re: Boiling water
During the phase change of a liquid to a vapor heat is supplied and that heat is being used to overcome the hydrogen bonds between the h2o molecules. Because all the heat is being used to break the hydrogen bonds, the temperature stays the same during the phase change.
- Sun Jan 31, 2021 7:44 am
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Kelvin or Celsius?
- Replies: 86
- Views: 5011
Re: Kelvin or Celsius?
It should be Kelvin
- Sun Jan 31, 2021 7:31 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: steam causing burns
- Replies: 40
- Views: 1185
Re: steam causing burns
You are correct. Going from a vapor to a liquid is an exothermic process because, similar to the formation of bonds, attractions between the molecules are being established, which requires the release of energy.
- Sun Jan 31, 2021 7:27 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Textbook question 4E.9
- Replies: 8
- Views: 444
Re: Textbook question 4E.9
For benzene without resonance I calculated the energy of three single c-c bonds and three double c-c bonds. With resonance, I multiplied the bond enthalpy of the double/single c-c (taken from the chart) bond by six. For benzene with resonance we do not use either the single or double c-c bond enthal...
- Sun Jan 31, 2021 7:11 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Standard Enthalpies of Formation using Hess's Law
- Replies: 18
- Views: 948
Re: Standard Enthalpies of Formation using Hess's Law
Yes, your assertion is correct.
- Sun Jan 31, 2021 7:08 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: change in celsius = change in kelvin
- Replies: 22
- Views: 7462
Re: change in celsius = change in kelvin
The conversion for Celsius to kelvin is simply Celsius + 273.15 = K. It’s just C plus the constant 273.15.
- Sun Jan 24, 2021 11:46 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Homework 5G.3
- Replies: 3
- Views: 165
Re: Homework 5G.3
In this case H20 would be included because it is in a gaseous state as the others are. If H20 was acting as a solvent you would ignore it, but that is not the case here.
- Sun Jan 24, 2021 11:44 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Water as a liquid in a reaction
- Replies: 4
- Views: 178
Re: Water as a liquid in a reaction
If water is a solvent, then you would ignore it for the equilibrium expression. If water was in the same state as the others then you would include it in the equilibrium equatIon.
- Sun Jan 24, 2021 11:19 am
- Forum: Ideal Gases
- Topic: Omitting solid/liquid
- Replies: 19
- Views: 636
Re: Omitting solid/liquid
We omit the solids and liquids because they are often present in excess and their concentrations change insignificantly, effectively they stay the same.
- Sun Jan 24, 2021 11:13 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: How to predict relative strengths of acids and bases
- Replies: 5
- Views: 255
Re: How to predict relative strengths of acids and bases
A high Ka indicates a strong acid and a low Kb also indicates. Similarly, a small pKa indicates a strong acid because you are taking the -log of Ka.
- Sun Jan 24, 2021 11:07 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: ICE Tables
- Replies: 36
- Views: 1518
Re: ICE Tables
It is only be determined by stoichiometric coefficients because we are solving for the molarity values.
- Sun Jan 17, 2021 8:22 am
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Kelvin or Celsius?
- Replies: 86
- Views: 5011
Re: Kelvin or Celsius?
It is always kelvin.
- Sun Jan 17, 2021 8:17 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Squared equations
- Replies: 5
- Views: 126
Re: Squared equations
As long as you take the square root of both sides of the equation it should work.
- Sun Jan 17, 2021 8:11 am
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: q vs k
- Replies: 62
- Views: 2320
Re: q vs k
Yes q will eventually reach k if the temperature remains the same. Also I think of q as a ratio that changes as the reaction continues and becomes equal to k when the reaction “finishes”.
- Sun Jan 17, 2021 8:05 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: The Quadratic equation
- Replies: 7
- Views: 449
Re: The Quadratic equation
I would not worry much about other applications of the quadratic formula in this class. Just know that it can be used whenever we get a polynomial with x^2+x. Just think of it as a mathematical tool to solve for x when a polynomial has the form ax^2 + bx + c.
- Sun Jan 17, 2021 8:00 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Kw constant
- Replies: 25
- Views: 670
Re: Kw constant
I think it is because H20 is present in excess and it’s change in concentration would be insignificant.
- Sat Jan 09, 2021 9:15 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: terminology
- Replies: 11
- Views: 425
Re: terminology
If a reaction favors the products, that would mean at equilibrium there is a greater concentration of products than reactants.
- Sat Jan 09, 2021 9:12 am
- Forum: Ideal Gases
- Topic: Gas constant R
- Replies: 26
- Views: 1024
Re: Gas constant R
R is a constant, so it is given to us.
- Sat Jan 09, 2021 9:11 am
- Forum: Ideal Gases
- Topic: R constant
- Replies: 4
- Views: 214
Re: R constant
What do you mean by the other R constant? I think our problems are in bar, so R would be about 8.314*10^-2. I suppose You would use a different value for R if a problem specifies that we are using a different unit.
- Sat Jan 09, 2021 9:05 am
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Calculating Q
- Replies: 7
- Views: 242
Re: Calculating Q
Yes, because your calculation for K would only include the gas.
- Sat Jan 09, 2021 9:03 am
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Q and K
- Replies: 46
- Views: 1516
Re: Q and K
Correct, K is the ratio of products and reactants at equilibrium and Q is the ratio when it is not at the equilibrium. The difference between Q and K tells us which direction the reaction will move.
- Sat Dec 12, 2020 3:23 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Oxoacids
- Replies: 3
- Views: 260
Re: Oxoacids
Yes, I think so. With oxoacids, the electronegativity of the other atom bonded to O determines the relative strength. The more electronegative it is, the weaker/more polar the O-H bond, so it would also be a stronger acid because the H proton is given up more easily.
- Sat Dec 12, 2020 3:17 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Textbook 6C19
- Replies: 4
- Views: 247
Re: Textbook 6C19
That is true for binary acids, but when we have acids like HClO2 and HBrO2, the difference in electro negativity determines the strength of the acid. Cl is more electronegative than Br. The higher electronegativity of Cl makes the O-H bond more polar and a little weaker, making it so the H is donate...
- Sat Dec 12, 2020 3:09 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: wedge and dash
- Replies: 14
- Views: 2462
Re: wedge and dash
A solid wedge represents the bond closest to you. The dashed wedge represents the one furthest away from you.
- Sat Dec 12, 2020 3:06 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Sapling HW 10 Question#5
- Replies: 3
- Views: 195
Re: Sapling HW 10 Question#5
pH is -log([H+]).
pOH is -log([OH-]).
If you have the pH, you can subtract the pH from 14 to get the pOH. If you have pOH, you can subtract the pOH from 14 to get the pH.
If you have the pH and you want [H+], you take 10^(-pH). Or, for [OH-], take 10^(-pOH).
pOH is -log([OH-]).
If you have the pH, you can subtract the pH from 14 to get the pOH. If you have pOH, you can subtract the pOH from 14 to get the pH.
If you have the pH and you want [H+], you take 10^(-pH). Or, for [OH-], take 10^(-pOH).
- Sat Dec 12, 2020 2:55 pm
- Forum: Conjugate Acids & Bases
- Topic: sapling question 14
- Replies: 7
- Views: 447
Re: sapling question 14
If the pKa is equal to the pH, it will be neutral. If the pKa is not equal to the pH, it is charged.
- Sun Dec 06, 2020 3:45 pm
- Forum: Bronsted Acids & Bases
- Topic: bronsted vs. lewis acid
- Replies: 10
- Views: 354
Re: bronsted vs. lewis acid
All acids are both Brønsted and Lewis acids. They are not actually separate things. They are two different ways to define an acid. Brønsted defines acids as proton donors, while Lewis defines acids as lone e- lone pair acceptors.
- Sun Dec 06, 2020 3:38 pm
- Forum: Naming
- Topic: Naming Coordination Compounds
- Replies: 5
- Views: 257
Re: Naming Coordination Compounds
Pertaining to the part inside the brackets. Ligands are named in alphabetical order. Prefixes are added to the ligands. The transition metal is named last and it’s oxidation number (in Roman numerals) comes right after in parentheses. That part is all one word. Now we name the ion (if present) that ...
- Sun Dec 06, 2020 3:29 pm
- Forum: Naming
- Topic: Prefixes for parts outside of Coordination Compound
- Replies: 7
- Views: 326
Re: Prefixes for parts outside of Coordination Compound
I am not 100% confident, but I think we do not need add a prefix to the ion outside of the brackets. Maybe this is because we know the net charge of the part inside the brackets to be +2, so we can infer that there must be a Cl2 on the outside.
- Sun Dec 06, 2020 3:20 pm
- Forum: Lewis Acids & Bases
- Topic: lewis vs bronsted
- Replies: 8
- Views: 538
Re: lewis vs bronsted
I like to think of these definitions with the hydrogen atom in mind because it has only one proton and one electron. A Lewis acid would accept the Hydrogen’s electron because a Lewis acid is a lone pair acceptor. A Brønsted acid would “donate” the Hydrogen’s proton. A Lewis acid and Brønsted acid ar...
- Sun Dec 06, 2020 3:12 pm
- Forum: Naming
- Topic: Order of Ligands/naming
- Replies: 28
- Views: 1073
Re: Order of Ligands/naming
I believe the order is alphabetical.
- Sun Nov 29, 2020 12:09 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Methane vs ammonia
- Replies: 5
- Views: 1165
Re: Methane vs ammonia
I think the geometry of NH3 is tetrahedral if we include the lone electron pair in the geometry. Although the lone pair does determine molecular geometry, we only account for the atoms (not lone pairs) when naming the structure. That is why NH3 is trigonal pyramidal rather than tetrahedral.
- Sun Nov 29, 2020 11:59 am
- Forum: Hybridization
- Topic: sp and sp2
- Replies: 7
- Views: 377
Re: sp and sp2
The sp, sp2, and sp3 hybrid orbitals are all different.
sp corresponds to 2 regions of electron density.
sp2 corresponds to 3 regions of electron density.
sp3 corresponds to 4 regions of electron density.
sp corresponds to 2 regions of electron density.
sp2 corresponds to 3 regions of electron density.
sp3 corresponds to 4 regions of electron density.
- Sun Nov 29, 2020 11:23 am
- Forum: Hybridization
- Topic: hybridization of phosphorus (Sapling Q.11)
- Replies: 21
- Views: 3194
Re: hybridization of phosphorus (Sapling Q.11)
There are four regions of electron density because there are four bonds. The double bond only counts as one region of electron density, so the hybridization orbitals would be sp3.
- Sun Nov 29, 2020 11:12 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bent Shape molecules
- Replies: 7
- Views: 959
Re: Bent Shape molecules
Bent shape molecules have the form AX2E. It has one lone pair on the central atom. This lone pair makes the atom bent rather than linear. I like to imagine the lone pair as a third atom connected to the central atom, giving the molecule trigonal-planar geometry but with only two atoms connected to t...
- Sun Nov 29, 2020 11:04 am
- Forum: Hybridization
- Topic: hybridization orbitals
- Replies: 5
- Views: 217
Re: hybridization orbitals
To find the hybridization orbitals, I count the individual regions of electron density associated with the atom. This includes lone pairs and bonds (keep in mind that a double or triple bond only counts as one region of electron density, not 2 or 3). If you have two regions of electron density, then...
- Sun Nov 22, 2020 4:25 pm
- Forum: Resonance Structures
- Topic: Resonance Structures and Energy
- Replies: 21
- Views: 866
Re: Resonance Structures and Energy
Yes. The resonance structure that contributes the most would
1. have the least number of atoms with a formal charge that is non-zero.
2. prefer lower formal charges over higher (+ or -) ones.
1. have the least number of atoms with a formal charge that is non-zero.
2. prefer lower formal charges over higher (+ or -) ones.
- Sun Nov 22, 2020 11:15 am
- Forum: Resonance Structures
- Topic: Valence Electrons [ENDORSED]
- Replies: 46
- Views: 3593
Re: Valence Electrons [ENDORSED]
To find the number of valence electrons, I look at the number of the column. For the elements of the s and p blocks, the digit in the one’s place is the # of valence e-. For example, O is in the 16th column and has 6 valence e-. F is in the 17th column and has 7 valence e-.
- Sun Nov 22, 2020 10:49 am
- Forum: Formal Charge and Oxidation Numbers
- Topic: Best Formal Charge Equations
- Replies: 24
- Views: 990
Re: Best Formal Charge Equations
I don’t think finding the formal charge gets much simpler than the equation:
(#valence e-) - (#lone e-) - (1/2 #bonding e-)
For the last term in the equation (1/2 of bonding electrons), I find it easier to just count the number of lines connected to the atom in question on the Lewis structure.
(#valence e-) - (#lone e-) - (1/2 #bonding e-)
For the last term in the equation (1/2 of bonding electrons), I find it easier to just count the number of lines connected to the atom in question on the Lewis structure.
- Sun Nov 22, 2020 10:43 am
- Forum: Ionic & Covalent Bonds
- Topic: Polar/ Nonpolar
- Replies: 25
- Views: 1082
Re: Polar/ Nonpolar
Shape is an indicator of polarity, but the molecule must also have dipole moments. It is important to consider both.
- Sun Nov 15, 2020 3:03 pm
- Forum: Trends in The Periodic Table
- Topic: Trends in Periodic Table Tips
- Replies: 12
- Views: 670
Re: Trends in Periodic Table Tips
For the ionization energy and atomic radius trends I just draw a box (representing the periodic table) with a horizontal arrow and a vertical one both pointing in the direction of increasing ionization energy/atomic radius. I find the simple visual easier to understand.
- Sun Nov 15, 2020 2:48 pm
- Forum: Bond Lengths & Energies
- Topic: reactive
- Replies: 10
- Views: 648
Re: reactive
The double bond is stronger, requiring more energy to break that bond; therefore, single bonds are weaker and require less energy to break the bond and so they are more reactive.
- Sun Nov 15, 2020 1:09 pm
- Forum: *Liquid Structure (Viscosity, Surface Tension, Liquid Crystals, Ionic Liquids)
- Topic: Rod vs spherical shaped molecules
- Replies: 10
- Views: 1598
Re: Rod vs spherical shaped molecules
Two adjacent rod shaped molecules will have more surface area in contact with each other than two spherical molecules. This is significant because London dispersion forces will have a greater effect on the rod shaped molecules.
- Sun Nov 15, 2020 1:05 pm
- Forum: Ionic & Covalent Bonds
- Topic: Ionic vs Atomic Radius
- Replies: 7
- Views: 418
Re: Ionic vs Atomic Radius
Hello! Atomic radius is the distance from the nucleus to the outermost electron in an atom. It’s ionic radius is the radius of that element’s ion. An ion with a positive charge will have a smaller radius than the element’s non-ionic form and ions with a negative charge will have a greater radius tha...
- Fri Nov 13, 2020 3:21 pm
- Forum: Lewis Structures
- Topic: Sapling #2
- Replies: 5
- Views: 244
Re: Sapling #2
Both of the single bonded Oxygens have a formal charge of -1. Remember the equation for formal charge is FC = valence - lone - (shared/2). The single bonded O would then be: 6 - 6 - (2/2) = -1
- Sun Nov 08, 2020 12:00 pm
- Forum: Lewis Structures
- Topic: Lone Pairs Question
- Replies: 22
- Views: 1529
Re: Lone Pairs Question
Lone pairs of the electrons are electrons held only by one atom and are not shared with any other atoms. In the Lewis structures they are represented by a dot.
- Sun Nov 08, 2020 11:59 am
- Forum: Quantum Numbers and The H-Atom
- Topic: Principle Quantum #
- Replies: 3
- Views: 181
Re: Principle Quantum #
I think the principle quantum number corresponds to the electron’s distance from the nucleus. The higher the value, the further it is away from the nucleus. The value of the principle quantum number in the valence shell would be the first number in the last part of the written electron configuration...
- Sun Nov 08, 2020 11:48 am
- Forum: Resonance Structures
- Topic: Bond lengths
- Replies: 20
- Views: 639
Re: Bond lengths
No. I do not think Lewis structures are meant to be that precise.
- Sun Nov 08, 2020 10:25 am
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Orbital vs Subshell
- Replies: 7
- Views: 461
Re: Orbital vs Subshell
N is the Energy level. L is the angular momentum, which determines the shape of the orbital (s,p,d,f). Finally ml determines the orientation (x,y,z).
- Sun Nov 08, 2020 10:16 am
- Forum: Ionic & Covalent Bonds
- Topic: atomic radius
- Replies: 7
- Views: 305
Re: atomic radius
The neighboring atoms are atoms that are adjacent to or almost “touching” the atom in question. Half the distance between these two nuclei is about where they touch.
- Sun Nov 01, 2020 3:20 pm
- Forum: Photoelectric Effect
- Topic: Sapling Problem #25
- Replies: 4
- Views: 186
Re: Sapling Problem #25
You can solve for the electron’s velocity by plugging the mass of an electron into the deBroglie wavelength equation. Remember that momentum (p) is mass*velocity. Once you have the velocity, use the equation E = 1/2mass*velocity^2 to solve for the energy.
- Sun Nov 01, 2020 3:05 pm
- Forum: Photoelectric Effect
- Topic: Sapling Problem #6
- Replies: 9
- Views: 4989
Re: Sapling Problem #6
The first part of the problem you just find the number of energy transitions the electron can make from the excited state of n = 6. So we would have 6-5, 6-4, 6-3, and so on. That gives you the number of spectral lines. To find the wavelength range you calculate the energy difference of the first an...
- Sun Nov 01, 2020 1:33 pm
- Forum: Properties of Light
- Topic: Is c always the speed of light?
- Replies: 92
- Views: 4742
Re: Is c always the speed of light?
C is the speed of light in a vacuum. Light traveling through air is a bit slower.
- Sun Nov 01, 2020 1:30 pm
- Forum: Lewis Structures
- Topic: Dot order
- Replies: 11
- Views: 699
Re: Dot order
The Lewis structures have two dot on each side of the element symbol. The electrons shared between atoms should face each other.
- Sun Nov 01, 2020 1:24 pm
- Forum: Student Social/Study Group
- Topic: Tips for Staying Focused
- Replies: 64
- Views: 3490
Re: Tips for Staying Focused
I always try to set aside time to go on walks whenever I am busy. Exercise in general helps me keep my mind clear.
- Sun Oct 25, 2020 4:43 pm
- Forum: DeBroglie Equation
- Topic: Derivation of Equations on Midterm?
- Replies: 17
- Views: 488
Re: Derivation of Equations on Midterm?
I do not think so because, as everyone else has pointed out, the test is multiple choice. However, I recommend understanding how to derive the equations because sometimes it makes problem solving easier, especially when you encounter a question that is a bit different than the ones you've previously...
- Sun Oct 25, 2020 4:35 pm
- Forum: Balancing Chemical Reactions
- Topic: Fundamentals L Exercises
- Replies: 2
- Views: 219
Fundamentals L Exercises
In the textbook, on the Fundamental problem L.35, we are given the following chemical reactions: Fe +Br2 → FeBr2 FeBr2 + Br2 → Fe3Br8 FeBr2 +Na2CO3 → NaBr + CO2 +Fe3O4 I was unable to balance the last one and I realized that the product of the second was not the reactant of the third. Am I correct i...
- Sun Oct 25, 2020 10:16 am
- Forum: Properties of Electrons
- Topic: intensity vs energy
- Replies: 29
- Views: 3114
Re: intensity vs energy
If we are thinking of light in photons, the light is quantized. This means that each photon has a discrete amount of energy. Increasing the intensity means that there is a greater number of photons, but the energy of each photon remains the same. The answer to that question, then, would be false.
- Sun Oct 25, 2020 10:12 am
- Forum: SI Units, Unit Conversions
- Topic: Do I need to do very single textbook question on the syllabus?
- Replies: 34
- Views: 1386
Re: Do I need to do very single textbook question on the syllabus?
It is a good idea to do all the textbook problems. The exams are based off problems from the textbook exercises.
- Fri Oct 23, 2020 11:45 am
- Forum: Quantum Numbers and The H-Atom
- Topic: Rydberg Constant
- Replies: 13
- Views: 508
Re: Rydberg Constant
Both are correct, but that equation takes R in Hz.
- Sun Oct 18, 2020 9:19 am
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Atomic Spectroscopy Assessment question clarification
- Replies: 2
- Views: 80
Re: Atomic Spectroscopy Assessment question clarification
Ok, I know now. The way it was phrased confused me. I just realized its per meter.
- Sun Oct 18, 2020 9:12 am
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Atomic Spectroscopy Assessment question clarification
- Replies: 2
- Views: 80
Atomic Spectroscopy Assessment question clarification
In the atomic spectroscopy assessment on the class website there is this question: "The meter was defined in 1963 as 1,650,763.73 wavelengths of radiation emitted by krypton-86 (it has since been redefined). What is the wavelength of this krypton-86 radiation?" "1,650,763.73 wavelengt...
- Fri Oct 16, 2020 2:13 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Atomic Spectroscopy N?
- Replies: 3
- Views: 182
Re: Atomic Spectroscopy N?
No, the term n is the variable for energy level. Suppose an electron moves from n= 3 to n= 2 and you want to find the change in E. You would then plug the initial n into the Rydberg equation and do the same for the final n. Then you solve E(final)-E(initial) to find (delta)E. The term n^2 is not the...
- Fri Oct 16, 2020 11:23 am
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Destructive Interference
- Replies: 3
- Views: 172
Re: Destructive Interference
Also, here is a fun fact: noise-cancelling headphones utilize destructive interference.
- Fri Oct 16, 2020 11:20 am
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Destructive Interference
- Replies: 3
- Views: 172
Re: Destructive Interference
If I go by the definitions I found online, destructive interference occurs when the peak of one wave aligns with the trough of another wave, which results in a wave with an amplitude of zero. If it is only considered destructive interference when the new amplitude is zero, then I would think that th...