## Search found 62 matches

Mon Mar 11, 2019 2:35 pm
Forum: Administrative Questions and Class Announcements
Topic: Saying Thank You to Dr. Lavelle
Replies: 291
Views: 136568

### Re: Saying Thank You to Dr. Lavelle

Thank you Dr. Lavelle for your assistance and patience. It has been a pleasure to be your student for the past two quarters!
Mon Mar 11, 2019 2:27 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Arrhenius Equation Application?
Replies: 1
Views: 68

### Arrhenius Equation Application?

What does the arrhenius equation determine and what would we use this equation for?
Mon Mar 11, 2019 2:25 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: rate determining step
Replies: 2
Views: 144

### Re: rate determining step

Why is the slow elementary step the rate-determining step and not the faster step?
Thu Mar 07, 2019 1:48 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Test 2 #5
Replies: 1
Views: 152

### Test 2 #5

Can someone please explain how you would approach this problem? I was not sure on what to do with the change in enthalpy and Kw.
Thu Mar 07, 2019 10:57 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Nernst
Replies: 6
Views: 214

### Re: Nernst

They are used interchangeably, but log is usually associated with pH!
Thu Mar 07, 2019 12:01 am
Forum: General Rate Laws
Topic: Types of Rate Laws?
Replies: 1
Views: 84

### Types of Rate Laws?

Can someone explain the difference between instantaneous, unique, differential, and average rate laws? How do we know when to use which?
Sat Mar 02, 2019 12:54 pm
Forum: General Rate Laws
Topic: Calculus Review
Replies: 8
Views: 349

### Re: Calculus Review

I believe we just need to know the simple derivative and integral rules.
Sat Mar 02, 2019 12:42 pm
Forum: General Rate Laws
Topic: Rate Law
Replies: 1
Views: 63

### Rate Law

Why do we need to conduct experiments to determine the rate law?
Sat Mar 02, 2019 12:35 pm
Forum: Balancing Redox Reactions
Topic: 14.15 Tips?
Replies: 1
Views: 116

### Re: 14.15 Tips?

First, you would have to write the half reactions and balance them. From there, you can figure out which is the anode and cathode and determine the E potentials from the back of the textbook. You might have to switch the direction of the anode, and therefore flip the sign of the E potential. The for...
Sat Feb 23, 2019 4:18 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Units
Replies: 4
Views: 114

### Re: Units

Joules or kj. I've also seen j/mol or kj/mol depending on the problem
Sat Feb 23, 2019 4:10 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Closed vs Isolated
Replies: 5
Views: 437

### Re: Closed vs Isolated

closed systems - exchange only energy
examples: pressure cooker, thermometer, pot with lid

isolated systems - does not exchange matter and energy
examples: thermos
Sat Feb 23, 2019 4:04 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Order of species in cell diagram
Replies: 1
Views: 91

### Re: Order of species in cell diagram

I believe so. We write it in the order of solids|gases|liquids|aqueous || aqueous|gases|liquid|solids
Sun Feb 17, 2019 3:05 pm
Forum: Van't Hoff Equation
Topic: Concept behind Van't Hoff Equation
Replies: 5
Views: 263

### Concept behind Van't Hoff Equation

Why do we use the Van't Hoff equation? What does it tell us in terms of K and temperature?
Sun Feb 17, 2019 12:14 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs Free Energy Signs
Replies: 4
Views: 179

### Gibbs Free Energy Signs

What are the signs for gibbs free energy for both spontaneous and non-spontaneous reactions?
Sat Feb 16, 2019 11:59 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Replies: 35
Views: 1293

Mon Feb 04, 2019 10:13 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: residual energy
Replies: 3
Views: 247

### Re: residual energy

I think you meant residual entropy (idk if there is a difference between residual energy and residual entropy haha). Residual entropy is the entropy at T=0 K. You can solve for it by using S=Kb*lnw (s=entropy, kb=boltzmann constant, w=degeneracy which is # of orientations^# of molecules). Degeneracy...
Mon Feb 04, 2019 9:53 pm
Forum: Calculating Work of Expansion
Topic: Units for Work
Replies: 2
Views: 145

### Re: Units for Work

Joules is also equal to N*m and (kg*m^2)/s^2. Not sure if we are required to know those. I haven't encountered a problem where we had to do that
Mon Feb 04, 2019 9:51 pm
Forum: Calculating Work of Expansion
Topic: Difference between reversible and irreversible expansion?
Replies: 2
Views: 676

### Difference between reversible and irreversible expansion?

Hi!

Can someone please explain the difference between reversible and irreversible expansion and how we are able to differentiate between the two

Thanks!
Sat Feb 02, 2019 10:49 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Entropy Equation Specific Heat Capacity
Replies: 2
Views: 112

### Re: Entropy Equation Specific Heat Capacity

If you are referring to the (3/2)R constant for the ideal gas, Cv, you would use that when volume is constant.
Sat Feb 02, 2019 10:42 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: constant pressure/volume vs specific/molar heat capacities
Replies: 4
Views: 156

### constant pressure/volume vs specific/molar heat capacities

Any advice to approaching calorimetry problems and differentiating between which constant (constant pressure/volume and specific/molar heat capacities) to use?

Thanks!
Sat Feb 02, 2019 10:32 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Material on Midterm?
Replies: 9
Views: 388

### Re: Material on Midterm?

It will probably go until the end of 2nd&3rd law of thermo (or maybe halfway i just looked at the syllabus and there are a lot of topics haha) because we were just introduced to entropy at the end of Friday's lecture.
Thu Jan 24, 2019 1:27 am
Forum: Administrative Questions and Class Announcements
Topic: Final Exam Papers
Replies: 1
Views: 115

### Re: Final Exam Papers

You can pick them up at a window/office on the third floor of Young Hall. It’ll be easier to find if you use the right side entrance that’s facing the Court of Sciences.
Wed Jan 23, 2019 9:36 pm
Forum: Phase Changes & Related Calculations
Topic: How to tell acids and bases
Replies: 8
Views: 261

### Re: How to tell acids and bases

Acids tend to have an H and bases OH

Also, the Bronsted-Lowry definition:
acid: proton (H+ ion) donor
base: proton acceptor
Wed Jan 23, 2019 9:32 pm
Forum: Phase Changes & Related Calculations
Topic: ∆Hsub=∆Hfus+∆Hvap
Replies: 3
Views: 165

### ∆Hsub=∆Hfus+∆Hvap

How does ∆Hsub=∆Hfus+∆Hvap work?
Thanks!
Mon Jan 14, 2019 7:53 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Changes in pressure
Replies: 2
Views: 158

### Re: Changes in pressure

When there is an increase in pressure, the reaction will occur in the direction w/ fewer moles of gas.
Mon Jan 14, 2019 7:20 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 6th Edition 11.39
Replies: 2
Views: 110

### 6th Edition 11.39

The solutions manual says to add reactions 1 and 2 together. Where does the Cl2 go when you do this step?
Also, why do we multiply the two K values together?
Mon Jan 14, 2019 7:13 pm
Forum: Ideal Gases
Topic: Homework for week 2 [ENDORSED]
Replies: 10
Views: 2410

### Re: Homework for week 2[ENDORSED]

Either one, as long as it's relevant to what we're learning in class and not too far ahead.
Sat Jan 12, 2019 2:30 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibria Changes
Replies: 3
Views: 125

### Equilibria Changes

Why does the value of K not change when we change the concentration of reactants or products?
Sat Jan 12, 2019 2:09 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Calculating K
Replies: 4
Views: 113

### Calculating K

When calculating for K, do we use the initial or equilibrium concentrations?
Tue Jan 08, 2019 11:53 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Difference between brackets and parentheses?
Replies: 4
Views: 692

### Difference between brackets and parentheses?

I noticed that when calculating K/Kc in questions 11.3 and 11.9 (6th edition), the solutions had either brackets or parentheses. Is there a difference between the two? How would I know which one to use?
Tue Dec 04, 2018 2:01 am
Forum: Biological Examples
Topic: Transition metals
Replies: 3
Views: 367

### Transition metals

Are we required to know the transition metals (such as Cr, Fe, Co, Mn, Ni, Cu, and Zn) and their functions for the final?
Tue Dec 04, 2018 1:58 am
Forum: Biological Examples
Topic: CH 17 6TH EDITION HW 17.31d
Replies: 4
Views: 210

### Re: CH 17 6TH EDITION HW 17.31d

the brackets indicate that the contents inside are the coordination compound. I assume that sodium is not part of it.
Tue Dec 04, 2018 1:32 am
Forum: Naming
Topic: Roman Numerals
Replies: 3
Views: 149

### Roman Numerals

How do we know when to include roman numerals when naming?
Mon Dec 03, 2018 8:43 pm
Forum: Bronsted Acids & Bases
Topic: Difference
Replies: 2
Views: 104

### Re: Difference

Bronsted-Lowry definition:
acid: proton (H+ ion) donor
base: proton acceptor

Lewis definition:
acid: electron acceptor
base: electron donor
Tue Nov 27, 2018 8:10 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Exam
Replies: 3
Views: 197

### Re: Exam

According to the chem 14a website, "Test 3 covers: End of Bonding from 3.12 (6 Ed.) and from 2D (7 Ed.); and all of Molecular Shape and Structure (see Syllabus and Outlines for details)."
Tue Nov 27, 2018 8:08 pm
Forum: Ionic & Covalent Bonds
Topic: Polar and Nonpolar
Replies: 3
Views: 123

### Re: Polar and Nonpolar

In polar covalent bonds, electrons are not equally shared. Thus, there is a charge difference in electronegativities and a dipole moment is formed.

In nonpolar covalent bonds, electrons are equally shared and there is no charge difference.
Mon Nov 26, 2018 8:10 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 6th Edition 4.7 Part B
Replies: 2
Views: 120

### 6th Edition 4.7 Part B

The solutions manual doesn't give a clear answer on how many bond angles there are for the molecule, SOCl2. Would there be two bond angles, one for the O-S-CL bonds and the CL-S-CL? Or does the lone pair on the S alter the angle because of repulsion, thus there is only one bond angle in the molecule...
Fri Nov 23, 2018 3:40 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR Models and Resonance Structures
Replies: 4
Views: 209

### VSEPR Models and Resonance Structures

Do we take into account resonance structures when determining the lewis structure and vsepr model of a molecule?
Fri Nov 23, 2018 3:36 pm
Forum: Dipole Moments
Topic: 6th Edition 4.29
Replies: 2
Views: 195

### 6th Edition 4.29

How can you determine whether or not the three different structures are polar or nonpolar?
Also, how can the dipole moment be determined based on the figures?

Fri Nov 23, 2018 3:00 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polarity
Replies: 7
Views: 276

### Re: Polarity

In polar molecules, dipoles do not cancel (e.g. CHCl3). The lewis structure of this molecule has one side that is more electronegative (Cl) than the other (H). An arrow would be drawn towards the more electronegative side -- Cl, indicating a dipole moment.
Mon Nov 12, 2018 1:08 pm
Forum: Dipole Moments
Topic: Interaction Potential Energy
Replies: 1
Views: 120

### Re: Interaction Potential Energy

The negative sign has to do with the potential energy decreasing due to the interactions occurring in London Forces. This decrease in energy is dependent on the distance between the two molecules that are interacting. If you want to read more on it, pages 191-196 (page 195 specifically on London For...
Mon Nov 12, 2018 12:50 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 1
Views: 37

### Bond Angles

What causes a bond angle to be less than their ideal values?
Mon Nov 12, 2018 12:39 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: Dipoles and Electronegativity
Replies: 4
Views: 248

### Re: Dipoles and Electronegativity

Dipole moments occur when there is a difference in charge between the two atoms or ions. The smaller the difference in electronegativity, the smaller the dipole moment is. The larger the difference in electronegativity, the larger the dipole moment.
Tue Nov 06, 2018 9:33 pm
Forum: Ionic & Covalent Bonds
Topic: Bond Lengths, Bond Order, and Bond Strength
Replies: 2
Views: 197

### Bond Lengths, Bond Order, and Bond Strength

Can someone please explain the relationship between bond length and bond order? And bond strength and bond order?

Thank you!
Tue Nov 06, 2018 9:31 pm
Forum: Ionic & Covalent Bonds
Topic: Bond Length
Replies: 8
Views: 309

### Re: Bond Length

SydBenedict3H wrote:So the shorter the bond,the stronger it also is?

Yes. Multiple bonds are shorter than single bonds. Adding bonding electrons attract nuclei more and pulls the atoms closer.
Tue Nov 06, 2018 7:25 pm
Forum: Sigma & Pi Bonds
Topic: Definition and distinguishing
Replies: 3
Views: 189

### Re: Definition and distinguishing

Bonds form between two atoms when: 1. orbital on one atom occupies the same region of space as an orbital on the other atom. When this occurs, the two orbitals overlap. 2. total # of electrons in both orbitals is no more than two sigma bonds: two atomic orbitals overlap head-to-head - These are cyli...
Tue Oct 30, 2018 8:18 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Config for period 5
Replies: 2
Views: 120

### Re: Electron Config for period 5

The TA and UA sessions I've been to just said that the only exceptions we need to know are chromium and copper.
Tue Oct 30, 2018 8:09 pm
Forum: Trends in The Periodic Table
Topic: Diagonal Orbitals
Replies: 1
Views: 150

### Re: Diagonal Orbitals

1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 5p10 This diagram tells you the order of filling out orbitals on the energy level diagram or electron configurations. For example, when you draw out the diagonal arrows, you would get 1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p6, etc. You don't really need th...
Tue Oct 30, 2018 8:00 pm
Forum: Ionic & Covalent Bonds
Topic: 3.19 6th edition
Replies: 1
Views: 144

### Re: 3.19 6th edition

The electron configuration for Tungsten is [Xe] 4f^14 5d^4 6s^2. Because it's W2+, we take away two electrons from the s energy level. The electron configuration is now [Xe] 4f^14 5d^4. If you were to draw out the orbitals, you'll find that d energy levels have five orbitals. The four electrons will...
Tue Oct 30, 2018 7:19 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 2.45 6th Edition
Replies: 1
Views: 106

### 2.45 6th Edition

I am a bit confused with part d of this question:

2.45 Which elements are predicted to have the following ground-state electron configurations:
(d) [Rn]7s2 6d2

The solutions manual says that the element with that electron configuration is thorium, but isn't thorium part of the f-block?
Fri Oct 26, 2018 10:46 pm
Forum: General Science Questions
Topic: Midterm studying
Replies: 10
Views: 749

### Re: Midterm studying

I find completing practice problems extremely helpful! Try to do all the hw problems and other problems in the textbook. Also, reviewing the tests and going over the problems again and your mistakes.
Fri Oct 26, 2018 7:38 pm
Forum: Ionic & Covalent Bonds
Topic: Exceptions
Replies: 4
Views: 286

### Re: Exceptions

Octet rule --> atoms completing their octets (noble-gas configuration) by sharing electron pairs H, He, Li, and Be are exceptions to the rule, meaning that they do not need the complete set of 8 electrons around them. Be and B commonly form compounds in which the central atom has fewer than four pai...
Thu Oct 25, 2018 11:15 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: H spectrum
Replies: 3
Views: 222

### Re: H spectrum

The empirical formula does not work for atoms other than hydrogen and multi-electron atoms. For multi-electron atoms, we would use the other formula (the one with Zeff) because of electron shielding and repulsion caused by multiple electrons.
Wed Oct 17, 2018 5:38 pm
Forum: Quantum Numbers and The H-Atom
Topic: Quantum Number L [ENDORSED]
Replies: 3
Views: 226

### Re: Quantum Number L[ENDORSED]

Quantum number l (angular momentum) distinguishes orbitals of the given n by different shapes. Additionally, it also tells you which suborbital an electron is located in. Here are a few l-values and their corresponding letters: 0=s, 1=p, 2=d, 3=f, 4=g S orbitals have a spherical shape. P orbitals ha...
Wed Oct 17, 2018 12:12 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: subshells & orbitals
Replies: 1
Views: 98

### Re: subshells & orbitals

each n: a shell each l and n: a subshell each n, l, and ml: an atomic orbital principle quantum # n: n = 1, 2, 3, etc. angular momentum l: - distinguishes orbitals of given n by different shapes - l = from 0 to (n-1) --> depends on n value - orbitals of same n and l belong to the same "subshell...
Mon Oct 15, 2018 6:19 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Heisenberg
Replies: 5
Views: 220

### Re: Heisenberg

The location (delta x) and the linear momentum (delta p) of a particle cannot be known simultaneously with arbitrary precision.
The two values are inversely proportional. If one is high, the other value is low.
Wed Oct 10, 2018 9:15 pm
Forum: Empirical & Molecular Formulas
Topic: Empirical & Molecular Formulas
Replies: 11
Views: 972

### Re: Empirical & Molecular Formulas

Yes, they can! Empirical formula tells you the most reduced form of elements in a compound, while the molecular formula gives you the actual number of those elements. Sometimes a molecular formula's compound can no longer be reduced.
Wed Oct 10, 2018 9:12 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: H-Atom and multi-electron atoms
Replies: 3
Views: 127

### H-Atom and multi-electron atoms

Is there a reason why we use two different equations for the hydrogen atom and the multi-electron model?
Wed Oct 10, 2018 9:10 pm
Forum: Einstein Equation
Topic: sig fig numbers
Replies: 4
Views: 146

### Re: sig fig numbers

Hi!
Answers on the hw and exam should always use the least number of sig figs.
Sat Oct 06, 2018 1:59 pm
Forum: Limiting Reactant Calculations
Topic: Calculating the amount of moles
Replies: 3
Views: 242

### Re: Calculating the amount of moles

Hello! I would convert the 1 kg of CaCO3 into grams and then moles (1kg CaCO3) x (1000g/1kg) x (1mol/100.0869g -- molar mass of CaCO3) = 9.99131 which is about 10 mol CaCO3 Based on the molar ratio in the balanced equation, 1 mole of CaCO3 = 1 mole of CO2 Therefore, 10 moles of CO2 will be produced ...
Wed Oct 03, 2018 11:40 pm
Forum: SI Units, Unit Conversions
Topic: Problem E7
Replies: 3
Views: 688

### Re: Problem E7

1 mole of objects means 6.0221 x 10^23 of 'objects', which in this case is carbon atoms. N=total number of objects (2.1 x 10^9) n=number of moles (unknown -- chemical amount of carbon atoms in moles) N_A= Avogadro's constant (6.0221 x 10^23) N=n x N_A --> n=N/N_A --> plug in the known values to solv...
Wed Oct 03, 2018 11:09 pm
Forum: Significant Figures
Topic: Sig Figs?
Replies: 3
Views: 180

### Re: Sig Figs?

Hello, One important rule about significant figures is that the zeroes on the left do not count as sig figs. Terminal zeroes on the right count. For example: 8.23, 0.845, 9.00, 5.60, and 0.000123 all have three significant figures. When multiplying and dividing w/ sig figs, the answers will be in th...