Search found 96 matches

Thu Mar 14, 2019 11:54 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagram Order
Replies: 2
Views: 83

Re: Cell Diagram Order

The anode is always oxidation and goes on the left. The cathode is always reduction and goes on the right.
In general the format is:

electrode on the anode side| oxidation half reaction || reduction half reaction| electrode on cathode side
Thu Mar 14, 2019 11:45 am
Forum: First Order Reactions
Topic: Integrated Rate Laws
Replies: 1
Views: 67

Re: Integrated Rate Laws

Yes, it is on the Kinetics outline. In general, I think we have to be able to find the integrated rate law by setting the unique rate expression equal to the overall rate law for a reaction with one reactant.
Thu Mar 14, 2019 11:32 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: H+ in Cell Diagram
Replies: 1
Views: 60

Re: H+ in Cell Diagram

H+ is usually always included in the cell diagram to indicate acidic conditions if H+ if part of the half reaction.
Thu Mar 07, 2019 9:48 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 7th Edition Problem 60.1
Replies: 1
Views: 83

7th Edition Problem 60.1

Why is the sulfate ion half reaction not considered in this problem when determine the oxidation and reduction half reactions?
Thu Mar 07, 2019 9:44 am
Forum: Second Order Reactions
Topic: pseudo-first-order reaction
Replies: 4
Views: 152

Re: pseudo-first-order reaction

Pseudo-first order reaction just means that the reaction is first order with respect to one of the reactants, but the overall reaction order can be different. The overall reaction can be second order and still be pseudo-first order with respect to each reactant.
Thu Feb 28, 2019 5:23 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Potential
Replies: 2
Views: 63

Re: Cell Potential

We will get a table of standard reduction potentials on the test which will have the reduction E values and the half reactions.
Thu Feb 28, 2019 5:21 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 7th edition 6L.5
Replies: 1
Views: 56

Re: 7th edition 6L.5

It helps to look at the table of standard reduction potentials so that you know which half reactions to use. You use the half reactions that involve Au+/Au and Au3+/Au. After balancing the equation, some of the Au cancels out and you are left with the net overall reaction.
Thu Feb 28, 2019 5:18 am
Forum: Van't Hoff Equation
Topic: Constants
Replies: 3
Views: 267

Re: Constants

I think we are just assuming that they are independent of temperature so that we can use those values at two different temperatures in the calculations to solve for K values when temperature changes.
Thu Feb 28, 2019 5:16 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Replies: 6
Views: 490

Adiabatic means there is no heat transfer (q=0) and isothermal means that there is no change in temperature (delta T=0).
Thu Feb 28, 2019 5:14 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Standard cell potential of H
Replies: 2
Views: 85

Re: Standard cell potential of H

This is set by definition in order to measure the standard cell potentials of the other half reactions since we can only measure E as a difference between the two electrodes used.
Fri Feb 22, 2019 3:43 pm
Forum: Balancing Redox Reactions
Topic: Redox Reactions on Test 2
Replies: 1
Views: 47

Redox Reactions on Test 2

For test 2, do we need to be able to balance redox reactions using H+/OH-/H2O in acidic/basic solutions, or will we only need to balance the reactions for batteries?
Thu Feb 21, 2019 5:55 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: voltaic and galvanic cells
Replies: 1
Views: 76

Re: voltaic and galvanic cells

Chemical to electrical energy is a galvanic cell, which has a negative delta G since it is spontaneous.
Electrical to chemical energy is a voltaic cell, which has a positive delta G since it is not spontaneous.
Thu Feb 21, 2019 5:43 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Flow of electrons
Replies: 4
Views: 122

Re: Flow of electrons

Electrons always flow from the anode (where oxidation takes place) to the cathode (where reduction takes place) in both galvanic and voltaic cells.
Thu Feb 21, 2019 5:35 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Salt Bridge
Replies: 3
Views: 87

Re: Salt Bridge

How does a porous disk complete the same function as a salt bridge?
Thu Feb 14, 2019 5:03 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: buffer
Replies: 2
Views: 92

Re: buffer

A buffer can resist pH changes upon the addition of an acid or base. It is often made up of an acid and its conjugate base.
Thu Feb 14, 2019 4:58 pm
Forum: Student Social/Study Group
Topic: week 6 homework
Replies: 2
Views: 313

Re: week 6 homework

What we covered in class about entropy is in sections 4F-4I in the seventh edition.
Thu Feb 14, 2019 4:46 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: isothermal irreversible free expansion
Replies: 2
Views: 222

Re: isothermal irreversible free expansion

Work is equal to zero since it is free expansion and delta U equals zero since it is isothermal. Thus q is also zero, since delta U=q+w. If q is zero and temperature is constant, then the entropy of the surroundings=-q/T, which equals zero.
Sun Feb 10, 2019 8:04 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Delta U for Reversible and Irreversible
Replies: 3
Views: 156

Delta U for Reversible and Irreversible

Is delta U equal to zero for both reversible and irreversible reactions? If not, under what conditions is delta U equal to zero?
Sun Feb 10, 2019 7:59 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Using R
Replies: 10
Views: 272

Re: Using R

I usually check the units of the other terms in the equation to determine which value of R I need to use
Sun Feb 10, 2019 6:34 pm
Forum: Administrative Questions and Class Announcements
Topic: Lyndon's HOTDOG MIDTERM REVIEW SESSION!! FINALLY!
Replies: 49
Views: 3363

Re: Lyndon's HOTDOG MIDTERM REVIEW SESSION!! FINALLY!

The enthalpy of formation of O2 is zero since it is in its standard state.
Tue Feb 05, 2019 3:25 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Microstate
Replies: 7
Views: 236

Re: Microstate

Knowing the number of microstates gives you the W value to use in the equation S=kB*ln(W).
Tue Feb 05, 2019 3:18 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Replies: 1
Views: 78

I'm not sure what section corresponds to the lecture in the sixth edition, but it is section 4G in the seventh edition.
Tue Feb 05, 2019 3:14 pm
Forum: Calculating Work of Expansion
Topic: Difference between L.atm and Joules
Replies: 2
Views: 116

Re: Difference between L.atm and Joules

When using the equation w=-P*delta V, the product of the units of pressure (generally atm) and volume (generally Liters) is L.atm. However, since work is defined as the energy to act against some force, the convention is to express work in units of energy (Joules), which is why we must convert L.atm...
Thu Jan 31, 2019 4:59 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy Symbol
Replies: 5
Views: 148

Re: Enthalpy Symbol

The naught signifies that the given enthalpy value is under standard conditions (1atm, 25 degrees C). When standard conditions are used in the experiment/calculation of enthalpy, then the naught symbol can be included.
Thu Jan 31, 2019 4:57 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 4C.3 7th Edition
Replies: 1
Views: 74

Re: 4C.3 7th Edition

For part a: delta H is 765 J and the final temp is 343 K.
for part b: delta H is 1275 J and the final temp is 373 K.
Thu Jan 31, 2019 4:54 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 7th edition 4C.3
Replies: 1
Views: 91

Re: 7th edition 4C.3

The textbook shows the derivation of Cp,m=Cv,m+R.

For a monatomic gas, Cv,m=delta U/delta T, which gives 3/2*R. (this derivation is also shown in the book on page 265 of the seventh edition in detail).

Using this result for Cv,m and the above formula, Cp,m is 5/2*R.
Tue Jan 29, 2019 9:23 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Signs for Bond Enthalpies
Replies: 4
Views: 102

Signs for Bond Enthalpies

Will the bond enthalpy values always be positive for reactants and negative for products, or are there any exceptions to this?
Tue Jan 29, 2019 9:20 am
Forum: Phase Changes & Related Calculations
Topic: 7th edition 4a.3 part c
Replies: 1
Views: 81

Re: 7th edition 4a.3 part c

Work is equal to the change in internal energy of the system, so ΔU= +28 J as calculated in part a of this question.
Tue Jan 29, 2019 9:15 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Cv and Cp
Replies: 2
Views: 58

Re: Cv and Cp

For an ideal gas, Cp is greater than Cv because the Cp system expands (since pressure is constant and volume is not) so the Cp system does work.
Thu Jan 24, 2019 3:29 pm
Forum: Phase Changes & Related Calculations
Topic: Temperature vs. heat vs. energy
Replies: 4
Views: 121

Re: Temperature vs. heat vs. energy

Heat (q) is a measure of thermal energy transferred. Temperature is a measure of the average kinetic energy of atoms or molecules.
Thu Jan 24, 2019 3:25 pm
Forum: Phase Changes & Related Calculations
Topic: Why steam causes severe burns
Replies: 9
Views: 346

Why steam causes severe burns

When Professor Lavelle was explaining why steam causes severe burns, I think he said that when the steam comes into contact with steam, it takes a longer time for it to become a liquid and releases heat in the process. Can someone explain/clarify this concept?
Thu Jan 24, 2019 3:18 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: using Ka and Kb to predict strengths of acids and bases
Replies: 3
Views: 260

Re: using Ka and Kb to predict strengths of acids and bases

If Ka<10^-3, the acid is considered weak. Similarly, if Kb<10^-3, the base is considered weak.
Thu Jan 17, 2019 8:38 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Autoprotolysis
Replies: 2
Views: 189

Re: Autoprotolysis

I think other molecules can undergo autoprotolysis as long as there is a proton transfer between two identical molecules where one acts as a Bronsted base and the other acts as a Bronsted acid.
Thu Jan 17, 2019 8:35 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: pKa1 solutions manual
Replies: 1
Views: 58

Re: pKa1 solutions manual

For acids that are polyprotic, there is a different pKa value each time the acid loses an H+. pKa1 just denotes the pKa value for the first H+ ion the acid loses and is used to distinguish it from its other subsequent pKa values.
Thu Jan 17, 2019 8:31 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Weak acids
Replies: 2
Views: 77

Re: Weak acids

I think you would just calculate [H3O+] using Ka for the stronger acid because it changes the pH of the solution. "If a really really weak acid is added to water and the change in [H3O+] is very small (like 10-9), then we say that the pH is essentially unchanged. 10-7 + 10-9 is really close to ...
Thu Jan 17, 2019 8:25 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 7th Edition Problem 6B.9 Solution
Replies: 1
Views: 52

7th Edition Problem 6B.9 Solution

Is there an error in the 7th edition solution manual for 6B.9? For (i), when I calculate -log[H3O+], I got -0.176, not +0.176 like the solution manual says. Can someone explain how to get the correct answer?
Sun Jan 13, 2019 2:50 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kc and Kp
Replies: 5
Views: 115

Re: Kc and Kp

Use Kp when even partial pressures and Kc when given concentrations. You can convert using PV=nRT and can also convert between Kp and Kc but that is more complicated, but is necessary when you are given Kp and concentration values (or the other way around).
Sun Jan 13, 2019 2:46 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Changes in Pressure
Replies: 2
Views: 39

Re: Changes in Pressure

Another possible scenario is that if the pressure was changed by decreasing/increasing volume and there are the same number of moles of gas on both the reactants and products sides of the equation, then the system would be unaffected and would not favor a particular side.
Sun Jan 13, 2019 2:42 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: 7th Edition Problem 5.35
Replies: 2
Views: 113

7th Edition Problem 5.35

Does anyone know why all the pressure values are divided by 100 in the K expression in problem 5.35 (7th edition)?
Wed Jan 09, 2019 2:30 pm
Forum: Ideal Gases
Topic: Units
Replies: 5
Views: 107

Re: Units

You can also use the units:

P in atmospheres (atm)
V in liters (L)
n in moles
T in Kelvin (K)
R= 0.08206 L.atm.K-1.mol-1 (constant)
Wed Jan 09, 2019 2:24 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Partial Pressures for Different Temperatures
Replies: 2
Views: 61

Re: Partial Pressures for Different Temperatures

In the second container, since the concentration of O2 is greater the partial pressure is greater. Pressure and concentration are directly proportional as shown by P=(conc.)RT, so if concentration is greater, then pressure is also greater (given that T is the same).
Wed Jan 09, 2019 2:19 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Q
Replies: 6
Views: 103

Re: Q

Q is written the same way as K is. Q=[products]/[reactants] and both solids and liquids are excluded from the expression.
Sat Dec 08, 2018 2:16 pm
Forum: Administrative Questions and Class Announcements
Topic: FINAL PRACTICE - Lyndon's Churro Review Session [ENDORSED]
Replies: 118
Views: 8687

Re: FINAL PRACTICE - Lyndon's Churro Review Session[ENDORSED]

How do we determine the hybridization on the lone pair? For example, if O is bonded to two atoms and has two lone pairs, wouldn't it just be sp3 or is there another specific notation for the lone pair I am missing? In the same way that you do when determining shape, count the regions of electron de...
Wed Dec 05, 2018 3:51 pm
Forum: Amphoteric Compounds
Replies: 1
Views: 66

I think we just need to know that an amphoteric compound can either donate an H+ or accept an H+. To draw these compounds you would just draw the Lewis structure and depending on whether it is acting as an acid/base in the reaction, you would draw the appropriate conjugate pair as having accepted an...
Wed Dec 05, 2018 3:45 pm
Forum: Conjugate Acids & Bases
Topic: Conjugate acid base example from class
Replies: 2
Views: 85

Re: Conjugate acid base example from class

The base is the compound that can accept a proton, so its conjugate acid is the compound that is formed after accepting that proton. It is a conjugate acid because if it is put in water it will act as an acid and donate the proton.
Wed Dec 05, 2018 3:41 pm
Forum: Lewis Acids & Bases
Topic: Homework Problem 6C.13
Replies: 3
Views: 123

Re: Homework Problem 6C.13

A Bronsted acid is defined as a proton donor, while a Lewis acid is an electron pair acceptor.
Wed Dec 05, 2018 3:30 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: 7th Edition Problem 6B.9 Solution
Replies: 1
Views: 78

7th Edition Problem 6B.9 Solution

Is there an error in the solutions manual for 6B.9 (7th edition)? The concentration of H30+ is given as 1.50 M in the problem, and using the information to calculate pH I got -0.176 but the solutions manual writes +0.176, which does not correlate to the hydronium ion concentration provided.
Wed Nov 28, 2018 5:04 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: Energy of Intermolecular Force
Replies: 2
Views: 93

Re: Energy of Intermolecular Force

Intermolecular forces are described as having negative energy values since they are attractive forces.
Wed Nov 28, 2018 5:01 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: 3F.1 (Seventh Edition)
Replies: 2
Views: 96

Re: 3F.1 (Seventh Edition)

In general, all molecules have dispersion forces.

If there is an H bonded to a N, O, or F atom there will be hydrogen bonding.

If the molecule has a net dipole (polar), there will be dipole-dipole interactions.
Wed Nov 28, 2018 4:50 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Equatorial axis
Replies: 1
Views: 51

Re: Equatorial axis

The equatorial bonds are in the same plane while the axial bonds are located above/below the plane. For example, a trigonal bipyramidal molecule has two axial bonds (the ones drawn on the top and bottom) and three equatorial bonds (the ones that are 120 degrees apart).
Sun Nov 25, 2018 11:14 am
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR model formula
Replies: 3
Views: 97

Re: VSEPR model formula

In the case that there are two central atoms, I believe you would write the VSEPR formula for each central atom separately since we identify molecular shape around each central atom separately as well.
Sun Nov 25, 2018 11:11 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Naming
Replies: 4
Views: 116

Re: Naming

I believe Dr. Lavelle said that he will generally ask for molecular shape, not the shape of the electron geometry.
Sun Nov 25, 2018 11:09 am
Forum: Hybridization
Topic: Test 3
Replies: 13
Views: 238

Re: Test 3

I think Dr. Lavelle said we do not need to know how to draw the shapes of the hybridized orbitals, but we do need to be able to identify the ones used.
Sun Nov 25, 2018 11:03 am
Forum: Hybridization
Topic: Octet Expansion
Replies: 6
Views: 152

Re: Octet Expansion

Starting from the third period, elements can expand their octet since there are more orbitals available. d orbitals are first available starting in the n=3 energy level. Once the s and p orbitals are filled in an energy level, the next available orbitals for the electrons are the d orbitals. The low...
Sun Nov 25, 2018 10:59 am
Forum: Hybridization
Topic: Carbon rotation in C2H4
Replies: 2
Views: 66

Re: Carbon rotation in C2H4

Because of the pi bond between the two C atoms, C2H4 cannot rotate. The pi bond essentially locks the molecule in place or makes it stationary. The pi bond must be broken in order for the C atoms to be able to rotate, and the molecule will stop rotating once the pi bond is reformed. I don't think th...
Fri Nov 16, 2018 5:39 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: dash and wedge diagram
Replies: 3
Views: 59

Re: dash and wedge diagram

I think the dash is usually drawn to show that the atom is going away from you and the wedge is usually drawn to show the atom is coming towards you.
Fri Nov 16, 2018 5:36 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: sigma and pi bonds
Replies: 1
Views: 69

Re: sigma and pi bonds

A single bond is always one sigma bond. If you have a double bond, one of the bonds will be a sigma bond and the other one will be a pi bond. If you have a triple bond, one of the bonds will be a sigma bond and the other two bonds will be pi bonds. This is because only one sigma bind can form, so th...
Fri Nov 16, 2018 5:33 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: cis and trans prefix's to molecules
Replies: 2
Views: 72

Re: cis and trans prefix's to molecules

These prefixes are used when naming isomers. Cis means same side and trans means on the other side. I don't think we need to know this nomenclature since we have not covered it yet.
Fri Nov 16, 2018 5:31 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: see saw
Replies: 2
Views: 98

Re: see saw

The see saw shape occurs when there are 5 regions of electron density, specifically 4 bonding pairs and 1 lone pair. Lone pairs are more repulsive, so to reduce the effect of the repulsion the lone pair interacts with only 2 bonds at 90 degrees versus a different arrangement, which would be less sta...
Fri Nov 16, 2018 5:25 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: cis and trans prefix's to molecules
Replies: 2
Views: 35

Re: cis and trans prefix's to molecules

These prefixes are used in naming isomers. Cis- means "this side" and trans- means "the other side of." I don't think we are required to know this nomenclature yet since we have not really gone over it.
Mon Nov 12, 2018 5:21 pm
Forum: Dipole Moments
Topic: Dipole Moments [ENDORSED]
Replies: 10
Views: 305

Re: Dipole Moments[ENDORSED]

The equation given for dipole moments was:
dipole moment= charge x distance between atoms (bond length)
Mon Nov 12, 2018 5:15 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 Forces v Dipole-Induced Dipole
Replies: 2
Views: 72

London Forces v Dipole-Induced Dipole

Both London forces and dipole-induced dipole forces have an energy of -2 kJ/mol. When asked to compare the intermolecular forces between two compounds, which one is stronger: London forces or dipole-induced dipole forces?
Mon Nov 12, 2018 5:05 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 2E.25 7th edition
Replies: 1
Views: 54

2E.25 7th edition

In the solutions manual for the 7th edition, the answer to part a 2E.25 is that CH2Cl2 is a polar molecule. Can someone explain why CH2Cl2 is polar? Wouldn't the dipole moments cancel, making this molecule nonpolar?
Thu Nov 08, 2018 6:16 pm
Forum: Electronegativity
Topic: Electronegativity Calculation
Replies: 5
Views: 145

Re: Electronegativity Calculation

We won't be asked to calculate electronegativity, but it is calculated using measured values of electron affinity and ionization energy.
Thu Nov 08, 2018 6:11 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: Polarizability and Dispersion Forces
Replies: 2
Views: 169

Polarizability and Dispersion Forces

If an atom or molecule is more polarizable, does this mean that its dispersion forces are stronger?
Thu Nov 08, 2018 6:03 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: Wednesay - 11/7 Notes
Replies: 2
Views: 136

Re: Wednesay - 11/7 Notes

I attached pictures of my notes from lecture on Wednesday 11/7. We covered strengths and lengths of bonds and attractive forces. Hope this helps!
Sun Nov 04, 2018 8:48 am
Forum: Ionic & Covalent Bonds
Topic: Chemical Bonds
Replies: 5
Views: 212

Re: Chemical Bonds

Chemical bonds form when the valence electrons of one atom interact with the valence electrons of another, resulting in the sharing of electrons.
Sun Nov 04, 2018 8:37 am
Forum: Octet Exceptions
Topic: Valence Electron
Replies: 2
Views: 136

Re: Valence Electron

The electron configuration for Sb is [Kr]4d 10 5s 2 5p 3 . The valence electrons are the electrons in the outermost shell. In the case, the outermost shell is n=5. Thus, the valence electrons are the five electrons in 5s and 5p. Since 4d is completely filled in Sb they are not valence electrons. 3d ...
Sun Nov 04, 2018 8:29 am
Forum: Lewis Structures
Topic: Textbook 7th edition problem 11 part C
Replies: 1
Views: 43

Re: Textbook 7th edition problem 11 part C

NH2, CH2, and COOH are all groups, so after counting the number of electrons I placed those groups together. Then I drew the bonds between the atoms within the groups and then between the groups to get the final Lewis structure.
Wed Oct 31, 2018 9:28 pm
Forum: Bond Lengths & Energies
Topic: Triple Bonds Shorter than Double Bonds
Replies: 4
Views: 324

Triple Bonds Shorter than Double Bonds

Can someone explain why triple bonds are shorter than double bonds?
Wed Oct 31, 2018 9:10 pm
Forum: Ionic & Covalent Bonds
Topic: p block atoms
Replies: 4
Views: 144

Re: p block atoms

The elements starting from the third period (P, S, Cl) can hybridize the d orbitals and thus have more than an octet.
Wed Oct 31, 2018 8:56 pm
Forum: Coordinate Covalent Bonds
Topic: Tetrafluoroborate anion
Replies: 3
Views: 380

Re: Tetrafluoroborate anion

I think the arrow from the diagram in Dr. Lavelle's powerpoint was just to visually show how the fluoride ion is added to BF3 to form BF4- with a coordinate covalent bond.
Thu Oct 25, 2018 9:06 pm
Forum: Properties of Electrons
Topic: Degeneracy
Replies: 11
Views: 471

Re: Degeneracy

Any element with 1 electron (such as Hydrogen or ions with one electron Li2+) would have degenerate orbitals (meaning that the orbitals in a given shell have the same energy).
Thu Oct 25, 2018 8:50 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Meaning of Z
Replies: 5
Views: 156

Meaning of Z

When we discussed the building up principle, the notes say to "add Z electrons with no more than two electrons per orbital." Does Z refer to the atomic number? I just wanted to make sure that the notation is correct.
Thu Oct 25, 2018 8:43 pm
Forum: Trends in The Periodic Table
Topic: Electron Affinity Trend
Replies: 9
Views: 299

Electron Affinity Trend

Can someone explain why electron affinity is the highest for elements in the top right of the periodic table?
Sun Oct 21, 2018 4:50 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Shielding [ENDORSED]
Replies: 15
Views: 798

Re: Shielding[ENDORSED]

Because of shielding, the outer electrons feel reduced electrostatic attraction, resulting in an effective nuclear charge. Shielding explains why it is easier (in other words, requires less energy) to remove the outer electrons because the outer electrons have less of an electrostatic attraction fro...
Sun Oct 21, 2018 4:42 pm
Forum: Properties of Light
Topic: Intensity vs energy
Replies: 6
Views: 206

Re: Intensity vs energy

Intensity is the amount of energy delivered per unit time per unit area.
Sun Oct 21, 2018 4:35 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Heisenberg Post Module Assessment #16
Replies: 2
Views: 78

Heisenberg Post Module Assessment #16

Which one of the following statements is correct in describing Heisenberg's uncertainty (indeterminacy) equation? A. The less precisely the position is determined, the less precisely the momentum is known in this instant, and vice versa. B. The more precisely the position is determined, the more pre...
Thu Oct 18, 2018 9:11 pm
Forum: Photoelectric Effect
Topic: Energy Levels
Replies: 2
Views: 135

Energy Levels

When Dr. Lavelle drew energy levels during lecture, higher energy levels were closer together. Is there a point when the distance between energy levels is so small that they are no longer distinct levels?
Thu Oct 18, 2018 8:51 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Wave Function v. Orbital
Replies: 3
Views: 74

Wave Function v. Orbital

Are the terms wave function and orbital essentially interchangeable? In other words, do theses two terms refer to the same thing?
Thu Oct 18, 2018 8:46 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Orbitals
Replies: 2
Views: 136

Re: Orbitals

The orbitals are not named alphabetically. The s, p, d, and f stand for sharp, principal, diffuse and fundamental, respectively.
Sun Oct 14, 2018 4:47 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Solving for frequency
Replies: 3
Views: 95

Re: Solving for frequency

Hertz (Hz) and s-1 are equivalent units. You can use either one for frequency.
Sun Oct 14, 2018 4:37 pm
Forum: Properties of Light
Topic: Photons
Replies: 4
Views: 112

Re: Photons

In lecture, Dr. Lavelle also mentioned that one photon interacts with one electron.
Sun Oct 14, 2018 4:31 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Atomic Spectra Post-Module #28
Replies: 1
Views: 85

Atomic Spectra Post-Module #28

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? To what region of the electromagnetic spectrum does this wavelength correspond (i.e. infrared, ultraviolet, x-ray, etc.)? W...
Thu Oct 11, 2018 9:02 pm
Forum: Properties of Light
Replies: 4
Views: 93

In the lecture, Dr. Lavelle mentioned that the description of light as photons explains the intensity profile of black body radiation. Can someone explain what black body radiation is?
Thu Oct 11, 2018 8:56 pm
Forum: Photoelectric Effect
Topic: Photoelectric Effect Equation
Replies: 3
Views: 110

Photoelectric Effect Equation

Can someone explain the condition E(photon) >= E(energy to remove e-) that was covered in lecture on Monday?
Thu Oct 11, 2018 8:52 pm
Forum: Photoelectric Effect
Topic: How do I find the mass of an ejected electron?
Replies: 3
Views: 109

Re: How do I find the mass of an ejected electron?

I think you have to use the mass of an electron, which is 9.10938356 × 10-31 kilograms.
Mon Oct 08, 2018 5:29 pm
Forum: Properties of Light
Topic: Speed of light constant (c)
Replies: 6
Views: 150

Re: Speed of light constant (c)

3.00x108 m/s is a rounded value. Generally in calculations 2.998x108 m/s is used since it has a greater number of sig figs and is not rounded off, so it is slightly more accurate than using a rounded value.
Mon Oct 08, 2018 5:21 pm
Forum: Limiting Reactant Calculations
Topic: Reactants and Reagents
Replies: 4
Views: 130

Re: Reactants and Reagents

Both terms are commonly used interchangeably and we will not get marked down for using one term over another.
Mon Oct 08, 2018 5:15 pm
Forum: Empirical & Molecular Formulas
Topic: when to multiply empirical formula [ENDORSED]
Replies: 9
Views: 989

Re: when to multiply empirical formula[ENDORSED]

In these problems, you always want to make sure you are multiplying by a whole number to ensure you have whole numbers of atoms.
Thu Oct 04, 2018 9:35 pm
Forum: Limiting Reactant Calculations
Topic: Calculating reactant moles [ENDORSED]
Replies: 4
Views: 128

Re: Calculating reactant moles[ENDORSED]

You are calculating the reactant moles in order to compare the amount of reactants available to the ratios in the balanced equation to determine which reactant is limiting. You cannot compare the quantities in grams since your balanced equation gives you molar ratios.
Thu Oct 04, 2018 9:20 pm
Forum: Balancing Chemical Reactions
Topic: States of Matter
Replies: 11
Views: 550

Re: States of Matter

I asked my TA this question in discussion today and he said for this first test we do not need to worry about writing the states of matter in a balanced equation; it is something we will go over later.
Thu Oct 04, 2018 9:12 pm
Forum: SI Units, Unit Conversions
Topic: L35 Tons Conversion Rate
Replies: 4
Views: 128

Re: L35 Tons Conversion Rate

In my discussion section today, my TA mentioned that 1 ton equals 1000 kg.
Sun Sep 30, 2018 7:23 pm
Forum: Balancing Chemical Reactions
Topic: Short cuts/methods for balancing equations
Replies: 15
Views: 252

Re: Short cuts/methods for balancing equations

Something that helps me keep track when I am balancing an equation is to list each atom in the reaction and write how many of it are on the reactant side to its left and how many of it are on the product side to its right. I also generally start with balancing the elements in one compound, and I usu...
Sun Sep 30, 2018 7:17 pm
Forum: Empirical & Molecular Formulas
Topic: Module Pre-Assessment Scoring [ENDORSED]
Replies: 1
Views: 96

Re: Module Pre-Assessment Scoring[ENDORSED]

Hey!

Unfortunately the score for the Pre-Assessment on the modules does not show up.

However, the questions in the Post-Assessment are the same as the ones in the Pre-Assessment and you will be able to see a score once completing the Post-Assessment.

Hope that helps!
Sun Sep 30, 2018 7:10 pm
Forum: SI Units, Unit Conversions
Topic: Fundamental Exercises E3 [ENDORSED]
Replies: 3
Views: 122

Re: Fundamental Exercises E3[ENDORSED]

I am not sure if you are referring to problem E3 in the 6th or 7th edition, but here is an explanation for E3 in the 7th edition. Based on the given molar masses, 1 mole of gallium atoms is 70 grams, and 1 mole of astatine atoms are 210 grams. In order for the two pans to be equal, the masses on eac...