## Search found 69 matches

Sat Mar 16, 2019 8:57 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Nernst Equation
Replies: 3
Views: 334

### Re: Nernst Equation

The Nernst equation helps to relate cell potential to the concentrations of the species within it. It therefore also helps relate standard cell potential to the equilibrium constant.
Sat Mar 16, 2019 8:54 pm
Forum: Zero Order Reactions
Topic: third order
Replies: 11
Views: 555

### Re: third order

Because third order reactions are so uncommon, I think Lavelle mentioned that we would not be focusing on them at all for calculations. Especially because the equation is not on the formula sheet, I think it would be really unlikely we would have to calculate anything for them. If anything, I would ...
Sat Mar 16, 2019 8:45 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Cell potentials
Replies: 1
Views: 236

### Re: Cell potentials

Whenever the half reactions have different numbers of electrons that do not cancel out with each other, you have to convert the cell potentials into free energy instead of adding them. In the 7th edition textbook, this is explained on page 558 of topic 6M
Sat Mar 16, 2019 8:38 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Test 2 Q6 Part C
Replies: 1
Views: 87

### Re: Test 2 Q6 Part C

You would have the largest Ecell if both E values are really positive. So, for the cathode, or the half reaction being reduced, you want to choose the reduction reaction with the highest E value. For the anode, or the half reaction being oxidized, you want to choose the half reaction with the lowest...
Sat Mar 09, 2019 11:02 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 6.79 7th edition
Replies: 1
Views: 120

### 6.79 7th edition

The question states: The body functions as a kind of fuel cell that uses oxygen from the air to oxidize glucose: C6H12O6(aq) + 6O6(g) --> CO2(g) + 6H2O(l) During normal activity, a person uses the equivalent of about 10MJ of energy a day. Assume that this value represents \Delta G and estimate the a...
Sat Mar 09, 2019 10:55 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 6.65 7th edition
Replies: 1
Views: 136

### 6.65 7th edition

The question asks what range (in volts) does a voltometer need to have to measure pH from the range of 1 to 14 at 25C if voltage is zero when pH=7. The solutions solve for the standard cell potentials, but I'm confused as to why - wouldn't you have to be solving for the cell potentials? Why are we a...
Sat Mar 09, 2019 10:48 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 6.63 7th edition
Replies: 1
Views: 147

### 6.63 7th edition

This question states that a pH meter is calibrated with a boric acid-borate buffer with a pH of 9.40, and the cell potential is +.060V. Then, the buffer is replaced with a solution of unknown [H+], but the new cell potential is +.22V. You need to calculate the pH of the new solution. The solution ma...
Sat Mar 09, 2019 10:42 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: What to plug in for Q? [ENDORSED]
Replies: 1
Views: 166

### What to plug in for Q?[ENDORSED]

In a bunch of the questions in the homework like 6N.3 of the 7th edition textbook, the solutions don't convert partial pressures into concentrations when they are put into Q, even if there are non-gaseous species included as well. Furthermore, all of the partial pressures have to be converted into a...
Wed Feb 27, 2019 10:20 am
Forum: Balancing Redox Reactions
Topic: salt bridge vs porous disk
Replies: 4
Views: 541

### Re: salt bridge vs porous disk

Also, when drawing the cell diagram, a porous disk would just be a single line rather than a double line between the two half-cells.
Wed Feb 27, 2019 2:21 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: moles of electrons of reaction
Replies: 3
Views: 127

### moles of electrons of reaction

When using the equation $\Delta G=-nFEcell$, does the number of moles of electrons we plug in depend on the moles of ions we start out with? Or do we only look at the moles of electrons transferred within the overall reaction?
Wed Feb 27, 2019 1:51 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Why does a cathode become negatively charged?
Replies: 1
Views: 103

### Why does a cathode become negatively charged?

In class, we went over how we need a salt bridge in order to maintain neutral charges in both half-cells. I understand how the oxidation reaction will lead to a greater amount of positive ions in that cell, so negative ions will balance that charge out. However, why would the cathode side attract po...
Sun Feb 24, 2019 1:21 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 4.41 (7th edition)
Replies: 1
Views: 91

### 4.41 (7th edition)

When comparing whether Fe3O4 or Fe2O3 is more stable based on their free energy, why do we have to find the standard gibb's free energy of the reaction of Fe3O4 and O2 into Fe2O3 in order to determine this, rather than just comparing each of their individual free energies?
Sun Feb 24, 2019 12:39 am
Forum: Van't Hoff Equation
Topic: Memorize equation?
Replies: 1
Views: 113

### Memorize equation?

I was looking over the constants and equations sheet, and I didn't see the Van't Hoff equation on it. Does this mean we will need to memorize it and understand how to derive it?
Sat Feb 23, 2019 11:51 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: 4.49 (7th edition)
Replies: 1
Views: 273

### 4.49 (7th edition)

This question asks what is common about molar entropies with a negative value. The answer is that the ones with negative entropies are all aqueous ions, because when the ions are dissolved surrounded by water molecules are more ordered that if it was the ion and the water molecules separately. Howev...
Sun Feb 17, 2019 2:45 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Meaning of Spontaneity
Replies: 3
Views: 620

### Re: Meaning of Spontaneity

A reaction is spontaneous if the entropy of the universe is increasing (Stot=Ssys+Ssurr). We went over in lecture how this equation can be related to the equation for Gibb's free energy. Therefore, it makes sense that Gibb's free energy should be negative if a reaction is spontaneous, because if the...
Sun Feb 17, 2019 2:33 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs Free Energy vs Internal Energy
Replies: 3
Views: 123

### Re: Gibbs Free Energy vs Internal Energy

I'm not entirely positive about this, but I think internal energy is more of a measure of the total energy of a system (which is why it can be changed by both work and heat). However, Gibbs free energy is a measure of only the energy that is available to be used. So, for example, during a reaction, ...
Wed Feb 13, 2019 2:16 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: When to assume constant pressure or reversible?
Replies: 1
Views: 120

### When to assume constant pressure or reversible?

In 4.1 7th edition, you need to calculate the heat required to convert a block of ice into water vapor. You solve this by using changes in enthalpy, but this means that pressure must be constant in order for change in enthalpy to equal q. However, it never specified it was at constant pressure. When...
Sun Feb 10, 2019 4:59 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 4C.3 part B (7th edition) - relating qv to delta H
Replies: 1
Views: 146

### 4C.3 part B (7th edition) - relating qv to delta H

In this problem we need to calculate the final temperature and change in enthalpy when 765J of heat are transferred to .820 mol Kr(g) at 298K and 1.00atm. In part, b, you are supposed to do both of these things at a constant volume. I understand that you can find qv and relate it to change in intern...
Sun Feb 10, 2019 4:53 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Is change in temp for calorimeter inverted?
Replies: 1
Views: 121

### Is change in temp for calorimeter inverted?

I understand that q=-qCal, implying that C(deltaT) = -Ccal(deltaT). However, for the side for the calorimeter, would we have to switch T1 and T2 because the heat released by the system is opposite the heat gained by the calorimeter? Or is it different because a change in temperature is different tha...
Sun Feb 10, 2019 4:49 pm
Forum: Phase Changes & Related Calculations
Topic: Does reversible also imply constant T?
Replies: 1
Views: 91

### Does reversible also imply constant T?

I understand that a reversible reaction means that volume and pressure are constantly changing infinitesimally in order to maintain the same pressure inside as outside. However, is temperature also still constant during this reaction, because the change in volume balances out the change in pressure?
Sat Feb 02, 2019 4:21 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: are systems always measured at equilibrium?
Replies: 2
Views: 81

### are systems always measured at equilibrium?

In class, we did the example: "an exothermic rxn (change in enthalpy = -50kJ) occurs in an open beaker producing net 8 moles of gast at 25C. What is the change in internal energy?" We assumed that there was no temperature change, because the temperature is taken before and after the reacti...
Sat Feb 02, 2019 4:13 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Why are reaction enthalpies per mol?
Replies: 1
Views: 115

### Why are reaction enthalpies per mol?

In questions like 4E.5 (7th edition), we calculate the reaction enthalpy using bond enthalpies given the reaction. However, the reaction enthalpy always ends up being set to kJ/mol. However, I'm confused why this is, because wouldn't multiplying the bond enthalpies given in kJ/mol by the number of m...
Sat Feb 02, 2019 3:59 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Calorimeter
Replies: 2
Views: 135

### Re: Calorimeter

I don't believe we need to know specifically how it works. I think the most important part is just we should assume that whenever a reaction is described as occurring in a bomb calorimeter, it is considered a completely isolated system. Therefore, no energy or matter can leave or enter, and the inte...
Sun Jan 27, 2019 1:00 pm
Forum: Phase Changes & Related Calculations
Topic: Phase changes
Replies: 14
Views: 669

### Re: Phase changes

I think you are correct. Because enthalpy is additive, if you reverse the reaction so that the product becomes the reactant, then the enthalpy should just be the negative of the forward reaction enthalpy.
Sun Jan 27, 2019 12:57 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: units for standard reaction enthalpy
Replies: 2
Views: 59

### units for standard reaction enthalpy

I know that standard enthalpy of formation is always kJ/mol. However, are the units for reaction enthalpy also kJ/mol, or just kJ? I feel like I see mixed answers within the textbook.
Sun Jan 27, 2019 12:55 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 4C.1- molar heat capacity (7th edition)
Replies: 1
Views: 73

### 4C.1- molar heat capacity (7th edition)

The question asks whether NO or NO2 has a higher heat capacity. The answer says NO2, because capacity increases with molecular complexity. Is this a rule that we have already learned? will molecules with more bonds always absorb more energy?
Sat Jan 19, 2019 4:21 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: units for equilibrium constants
Replies: 1
Views: 96

### units for equilibrium constants

Are there specific units we should be using for our equilibrium constants for gases? I know the partial pressures themselves within the equation technically don't have units, but should we be converting values to anything specific, like bars or atm? If so, will we be given the conversion equations b...
Sat Jan 19, 2019 3:53 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5.35 7th edition
Replies: 1
Views: 37

### 5.35 7th edition

In this question, it gives you a plot of partial pressures of reactants and products. From the graph (attached below), you obtain the balanced equation 2A(g) --> B(g) +2C(g). My first question is why this balanced equation doesn't have an equilibrium symbol, and if it would be considered wrong if we...
Sat Jan 19, 2019 3:40 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Need to always check for Q?
Replies: 2
Views: 149

### Need to always check for Q?

In some problems in the homework (like 5I.25 7th edition), the initial amounts of the mixture include both products and reactants. Therefore, the solution manual did a check for Q first to see if the reaction will move forward or backward. Do we have to do this too each time there are both products ...
Sat Jan 19, 2019 3:33 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5I.13 (b) - 7th edition - sig figs
Replies: 1
Views: 33

### 5I.13 (b) - 7th edition - sig figs

In this question, we are supposed to calculate the equilibrium composition. I got the quadratic equation 0= 4x 2 +1.2*10 -4 x-1.2*10 -7 , which led to x being 1.6*10 -4 . [F2]=1.0*10 -3 -x, so I got the answer 8.4*10 -4 . However, the answer key gives the answer with just two sig figs, making it 8*1...
Fri Jan 11, 2019 12:59 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: HW Problem 5H.1 [ENDORSED]
Replies: 4
Views: 209

### Re: HW Problem 5H.1[ENDORSED]

Here's a helpful table from the book (pg. 410 7th edition) summarizing these rules. It also explains these concepts with more examples on that page if you need more clarification.
Fri Jan 11, 2019 12:44 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: 5G.11 b
Replies: 3
Views: 166

### Re: 5G.11 b

I'm not entirely sure either, but I think aqueous reactants/products may stay in because they are still reacting significantly to reactants/products (aqueous just means in water). This is contrasting to pure water, which you don't include, that the solute is mixed in. There is so much solvent (water...
Fri Jan 11, 2019 12:34 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Gas unit conversions
Replies: 1
Views: 42

### Gas unit conversions

Does anyone know if we will have to know how to convert all of the different gas units to bar? Like if a question gave something in atm and if we would need to know how to convert it to bar for equilibrium constants?
Fri Dec 07, 2018 11:48 am
Forum: Calculating the pH of Salt Solutions
Topic: pH sig figs
Replies: 4
Views: 403

### pH sig figs

In the textbook, it says that the number of sig figs AFTER the decimal in the pH value should equal the sig figs of the molarity. However, many of the solutions don't seem to follow this rule. Should we just base sig figs in our pH normally, or follow this decimal rule?
Fri Dec 07, 2018 11:45 am
Forum: Bronsted Acids & Bases
Topic: 6C.17 (7th edition)
Replies: 2
Views: 170

### 6C.17 (7th edition)

The question asks whether BrO- or C17H19O3N is a stronger base. The solution uses their respective pKb values to determine their strengths as bases. However, is there a reason to logic which is stronger without the values, or would we have to be provided the values in order to know?
Fri Dec 07, 2018 11:40 am
Forum: Lewis Acids & Bases
Topic: 6.5 (7th edition)
Replies: 1
Views: 231

### 6.5 (7th edition)

The question asks you to write the chemical equation, draw the lewis structures, and identify lewis acid and base of the reaction H2O2 reacts with sulfur trioxide to form H2SO5. I really don't understand a lot about this question. I understand that the chemical equation would be H2O2 + SO3 --> H2SO5...
Fri Dec 07, 2018 11:31 am
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: structure of SO2 and SO3
Replies: 2
Views: 138

### structure of SO2 and SO3

For 7th edition 6A.15 and 6.5, the questions ask you to draw the structures of SO2 and SO3 respectively. I thought having all of the oxygens with double bonds would be the most stable structure, providing the lowest formal charges. However, the answers show SO2 with 1 double and 1 single bond, and S...
Sat Dec 01, 2018 6:37 pm
Forum: Naming
Topic: 9C.1 7th edition alphabetical order when naming
Replies: 2
Views: 151

### Re: 9C.1 7th edition alphabetical order when naming

The order within the formula and when writing the actual name may be different. The alphabetical order of the ligands when written out for the naming is independent of the alphabetical order when writing out the formula.
Sat Dec 01, 2018 6:32 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: 9C.5 (7th edition) and polydentates [ENDORSED]
Replies: 1
Views: 96

### 9C.5 (7th edition) and polydentates[ENDORSED]

For polydentates, even if an oxygen has multiple lone pairs, will that oxygen form multiple bonds or just one? Also, in 9C.5, why does oxalate only count as a bidentate whereas CO32- can be both a mono or bidentate?
Sat Dec 01, 2018 6:26 pm
Forum: Naming
Topic: questions about 9C.3 7th edition
Replies: 1
Views: 121

### questions about 9C.3 7th edition

For part c of this question, the formula for tetraamminediaquacobalt(III) is [Co(NH3) 4 (OH2) 2 ]Br3. However, in the solution manual instead of OH2, it is written as H2O. Does anybody know why this is? Also, in part d of this question, the formula for sodium bisoxalato(diaqua)ferrate(III) is writte...
Wed Nov 21, 2018 5:11 pm
Forum: Bond Lengths & Energies
Topic: Dissociation Energy
Replies: 4
Views: 327

### Re: Dissociation Energy

I don't think we have to know the exact values of the dissociation energies. I would just focus on the relative trends of dissociation energy due to changes in atomic radius (greater radius means lower dissociation energy), multiplicity (greater multiplicity means higher dissociation energy), and nu...
Wed Nov 21, 2018 5:06 pm
Forum: Hybridization
Topic: bonds
Replies: 4
Views: 75

### Re: bonds

Ya, a sigma bond doesn't become a pi bond, its just that more types of bonds are added on as you go from single to double to triple bonds. I found this image really helpful in visualizing how a pi bond and sigma bond interact in a double bond. https://ds055uzetaobb.cloudfront.net/image_optimizer/3ab...
Wed Nov 21, 2018 4:55 pm
Forum: Lewis Structures
Topic: 7th Edit 2.11a
Replies: 1
Views: 39

### Re: 7th Edit 2.11a

The model for C6H4O2 given below the question does not include the extra valence electrons that should fill the oxygens' octets. Each one of those oxygens should have 2 extra lone pairs, meaning there are 40 valence electrons for C6H4O2. Therefore, the reduced product should have 42.
Wed Nov 21, 2018 4:37 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond angles for T-shaped, see-saw, and square pyramidal
Replies: 2
Views: 159

### Bond angles for T-shaped, see-saw, and square pyramidal

I understand that lone pairs push down the bonding pairs leading to smaller bond angles than expected given the VSEPR shape. However, for t-shaped, see-saw, and square pyramidal, I am confused if the lone pairs push on the equatorial bonds, the axial bonds, or both. Therefore, I am also confused on ...
Wed Nov 21, 2018 4:11 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: London force strength vs. electronegativity
Replies: 3
Views: 363

### Re: London force strength vs. electronegativity

Oh okay this makes things clearer! But I'm still a little confused, because wouldn't flourine's greater electronegativity lead to stronger dipole-dipole bonds too? Or is this difference less important than the difference in london forces?
Sat Nov 17, 2018 9:56 pm
Forum: Hybridization
Topic: Bond Angles
Replies: 12
Views: 482

### Re: Bond Angles

I'm not completely sure, but I do think you would need to know the VSEPR shape in order to figure out the bond angles, because that takes into account the electron repulsions that create those angles.
Sat Nov 17, 2018 9:49 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: London force strength vs. electronegativity
Replies: 3
Views: 363

### London force strength vs. electronegativity

In the 7th edition book problem 3F.5 part c, between CHI3 and CHF3, CHI3 has a higher melting point because of london forces. I understand iodine is a larger molecule with a lower electronegativity, meaning it is more polarizable and therefore has stronger london forces. However, flourine is a highl...
Sat Nov 17, 2018 9:14 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: No central atom
Replies: 7
Views: 289

### Re: No central atom

I think you would treat it like each central atom is the center of its own shape. So since each nitrogen has 3 bonding pairs and 1 lone pair, the molecule would look like 2 trigonal pyramidal shapes put together. I'm not totally sure about this though, sorry!
Sat Nov 10, 2018 10:01 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Lewis Structures and VSEPR
Replies: 1
Views: 37

### Re: Lewis Structures and VSEPR

In class, I think it was mentioned that it is okay if we just draw normal lewis structures if the question doesn't specify because sometimes the shapes can get really complicated. However, we will have to be able to name the actual VSEPR shape. As for lone pairs, I think it doesn't really matter whi...
Sat Nov 10, 2018 9:57 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Induced Dipole-Induced Dipole names?
Replies: 4
Views: 364

### Re: Induced Dipole-Induced Dipole names?

What is Induced dipole? An induced dipole is formed due to random electron movement. Sometimes, randomly, an electron cloud will form more on one side of a molecule than another, creating a temporary chance "induced dipole". This chance dipole then can induce a dipole in a neighboring mol...
Sat Nov 10, 2018 9:52 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angle
Replies: 2
Views: 47

### Re: Bond Angle

I think you are right that it would, because no matter if it was connecting with a coordinate covalent bond, the electrons will be repelling each other the same as any other tetrahedral molecule, forming the same shape with 109.5 degree angles.
Sat Nov 03, 2018 9:26 pm
Forum: Lewis Structures
Topic: 2C.5 part c (7th edition)
Replies: 2
Views: 78

### Re: 2C.5 part c (7th edition)

Ohhh okay thank you so much!
Sat Nov 03, 2018 9:23 pm
Forum: Lewis Structures
Topic: Brackets around ions
Replies: 2
Views: 84

### Brackets around ions

In 7th edition problem 2B.9, the lewis structures for Cl-, K+, and Na+ don't include brackets around them. Does anyone know why this is? Would we get points off on exams if we did draw brackets?
Sat Nov 03, 2018 9:10 pm
Forum: Lewis Structures
Topic: Expanded Valence Shells
Replies: 2
Views: 122

### Re: Expanded Valence Shells

I'm not totally sure, but I don't think there is necessarily a limit. I think in the end it really just depends on trying to get the formal charges as close to 0 as possible.
Sat Nov 03, 2018 9:02 pm
Forum: Lewis Structures
Topic: 2C.5 part c (7th edition)
Replies: 2
Views: 78

### 2C.5 part c (7th edition)

In the 7th edition textbook, the solution for the lewis structure for ClONO3 (2C.5 part c) assigns the Nitrogen in the molecule single bonds to 2 oxygens, and a double bond to another oxygen. However, wouldn't the most stable state assign the nitrogen 2 double bonds and a single bond, because that m...
Wed Oct 24, 2018 8:19 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: 7th edition 1B.27 [ENDORSED]
Replies: 3
Views: 281

### Re: 7th edition 1B.27[ENDORSED]

You're totally right in that the uncertainty of velocity should be 10m/s. The textbook and solution manual made a mistake. You can see the error addressed in the "Solution Manual Errors in the 6th Edition" link Dr. Lavelle has on his site (it is not listed on the 7th edition errors link, b...
Wed Oct 24, 2018 8:16 pm
Forum: Quantum Numbers and The H-Atom
Topic: Degeneracy
Replies: 7
Views: 1493

### Re: Degeneracy

Degeneracy means the same energy. For example, with hydrogen, every subshell in the same energy level will be degenerate, because there is no electron-electron repulsion countering the pull of the nucleus, as there is only one electron. However, with multi-electron atoms, the subshells within the sa...
Wed Oct 24, 2018 8:02 pm
Forum: Quantum Numbers and The H-Atom
Topic: 2 Exceptions to the Electron Configuration
Replies: 3
Views: 110

### Re: 2 Exceptions to the Electron Configuration

Their p-orbitals of Cr and Cu only need one more electron to reach the much more stable state of all the p orbitals having 1 electron (5 in total), or 2 electrons in each orbital (10 in total). Therefore, in those cases, an electron will jump down from the higher energy s orbital to complete the orb...
Fri Oct 19, 2018 10:05 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Relation of charge to electrostatic potential energy
Replies: 1
Views: 88

### Relation of charge to electrostatic potential energy

I might have heard this wrong, but I think it was explained in class how a larger negative charge increases energy. I'm a little confused why this is, because wouldn't a higher positive value also increase energy according to [(q1)(q2)]/r ? Also, when he says, does he mean the total value of (q1)x(q...
Wed Oct 17, 2018 11:43 pm
Forum: Properties of Electrons
Topic: electrons
Replies: 3
Views: 143

### Re: electrons

I'm not completely sure myself, but I'm thinking it probably has to do with electron-electron repulsion. So, if there are multiple electrons, you have to take into account the differences in their movement due to electrons trying to avoid each other. But, I'm not totally sure how this affects their ...
Wed Oct 17, 2018 11:36 pm
Forum: SI Units, Unit Conversions
Topic: Significant Figures for Adding Numbers in Scientific Notation
Replies: 2
Views: 186

### Re: Significant Figures for Adding Numbers in Scientific Notation

The answer would have 2 sig figs. the x10^ part of scientific notation does not count as a sig fig.
Wed Oct 17, 2018 11:33 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Atomic Spectra
Replies: 1
Views: 58

### Re: Atomic Spectra

Looking at the equation you cited, v=E/h or E=hv, because h is a constant, v, or frequency, is directly proportional to E, and is, in fact, the only factor that changes it. Therefore, it could be said that the energy of a photon is defined by its frequency.
Sat Oct 13, 2018 4:08 pm
Forum: DeBroglie Equation
Topic: De Broglie wavelength - when can it be seen
Replies: 5
Views: 90

### Re: De Broglie wavelength - when can it be seen

I think he was maybe saying that when things have a large enough mass, their wavelengths become so small that they are basically negligible. For example, all things made of matter have wavelike properties, including things like cars. But, you don't see a car squiggling with waves down the road. The ...
Sat Oct 13, 2018 3:48 pm
Forum: Properties of Light
Topic: Measurable wavelengths
Replies: 5
Views: 148

### Re: Measurable wavelengths

I think he said that the minimum detectable wavelength was 10^(-18) m
Sat Oct 13, 2018 3:12 pm
Forum: Properties of Light
Topic: Frequency Equations
Replies: 2
Views: 95

### Re: Frequency Equations

The textbook gives us the Rydberg formula, which is \nu = R \left \{ \frac{1}{n_{1}^{2}}-\frac{1}{n_{2}^{2}} \right \} So I think it has to have something to do with combining the equations E=hv, and E=-hR/n^2 , so you get v=-R/n^2. Then, if you were trying to find v1-v2, you would get \nu = -R \lef...
Sun Oct 07, 2018 10:05 pm
Forum: Properties of Light
Topic: Speed of light constant (c)
Replies: 6
Views: 207

### Speed of light constant (c)

I know during lecture we defined c as 3.00x10^8m/s, but in the solution manual for homework, it is defined as 2.998x10^8m/s. Is there any preference for how many sig figs are preferred for this constant?
Mon Oct 01, 2018 12:12 am
Forum: Empirical & Molecular Formulas
Topic: Percent Composition
Replies: 5
Views: 365

### Re: Percent Composition

I totally agree with your answer, but I think it is also really important to take into account the molar mass along with the number of atoms. For example, H2 would still account for less percent than O in water. I don't think actual calculation was necessary for this question, but maybe it had 4 sig...
Sun Sep 30, 2018 11:46 pm
Forum: Empirical & Molecular Formulas
Topic: Multiple Ratio Possibility?
Replies: 4
Views: 205

### Multiple Ratio Possibility?

Hi! This might be a stupid question, but I was just wondering that if when trying to find a whole number ratio to get the empirical formula, I find the wrong ratio from a non-whole number ratio? For example, what if I multiply my non-whole number ratio by 3 and in the end, every number is extremely ...
Sun Sep 30, 2018 11:32 pm
Forum: Significant Figures
Topic: Rounding vs. Storing answers each step [ENDORSED]
Replies: 2
Views: 143

### Rounding vs. Storing answers each step[ENDORSED]

Hi guys! Does anybody know if we can round off our answers each step to the correct amount of sigfigs? I'm not sure if I should use rounded off steps or if I should store each step's answer on my calculator to use for the actual calculation until the end, only writing down the rounded off sigfigs fo...