## Search found 59 matches

Fri Mar 15, 2019 10:02 pm
Forum: General Rate Laws
Topic: Rate laws
Replies: 2
Views: 143

### Rate laws

On the lecture slide, it said "rate written as a function of concentration often referred to as rate law". Does that mean that a rate law is the same as a differential rate law?
Fri Mar 15, 2019 9:00 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Activated structure [ENDORSED]
Replies: 2
Views: 89

### Activated structure[ENDORSED]

I know Dr. Lavelle went over these briefly in class, but what are they, and do we need to know how to draw them?
Fri Mar 15, 2019 8:07 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Pre-equilibrium approach
Replies: 2
Views: 133

### Pre-equilibrium approach

When do you leave the equilibrium constants and when do you substitute k/k'? For example, in the one Dr. Lavelle did in lecture, he got rate=2k2*K*[NO]^2*[O2]. He then replaced K with k1/k1' to get rate=2k2*k1/k1'*[NO]^2*[O2]. Do you always replace K or are there times where you have to leave it in?
Sun Mar 10, 2019 4:57 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Microscopic reversibility
Replies: 3
Views: 158

### Microscopic reversibility

Can we always assume that microscopic reversibility is being applied?
Sun Mar 10, 2019 4:52 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Reactions with Multiple Reactants
Replies: 3
Views: 127

### Reactions with Multiple Reactants

In lecture, Dr. Lavelle went over how to find the rate constant for reactions with multiple reactants. At the end, he said that k[A]^N*[B]0^M*[C]0^L=k'[A]. Could you do this with B and C as well? ex. k[A]0^N*[B]^M*[C]0^L=k'[B]
Sun Mar 10, 2019 4:46 pm
Forum: First Order Reactions
Topic: Graphs
Replies: 2
Views: 127

### Graphs

Will we need to be able to set up graphs to find the order of a reaction on the final? If so, how do you do it?
Sun Mar 03, 2019 12:04 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 14.55 6th edition
Replies: 1
Views: 76

### 14.55 6th edition

Given NiSO4(aq), how do you know that the SO4^2- ion will not oxidize?
Sun Mar 03, 2019 10:51 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 14.47 6th Edition
Replies: 1
Views: 109

### 14.47 6th Edition

For part a, I keep getting 2649868 for Q, but the answer in the manual is 10^6. Is the reaction quotient always going to be rounded to a multiple of 10?
Sun Mar 03, 2019 8:24 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 14.37
Replies: 1
Views: 106

### 14.37

In part a, to find Q, the book multiplies the reactant concentration of H+(0.075 M) by the reactant partial pressure of H2 (1 bar) divided by the product of the product concentration of H+ (1 M) multiplied by the product partial pressure of H2 (1 bar). Why are we allowed to multiply concentration by...
Sat Feb 23, 2019 9:34 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Platinum
Replies: 3
Views: 157

### Platinum

When do you include platinum in the cell diagram?
Sat Feb 23, 2019 7:28 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 14.13 6th Edition
Replies: 1
Views: 108

### 14.13 6th Edition

I understand cell diagrams go anode||cathode, but what about the order of the anode ions and cathode ions? I've heard to write it reactants|products and to put it in order depending on the phase with the solids on the outside. However, in 14.13 part b, the cell diagram is Pt(s)|I^-(aq)|I2(s)||Ce^4+(...
Sat Feb 23, 2019 3:26 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: 14.9 6th Edition
Replies: 2
Views: 102

### 14.9 6th Edition

The question asks you to calculate the standard reaction Gibbs free energy for a. 2Ce^4+(aq)+3I^-(aq)—>2Ce^3+(aq)+I3^-(aq). How do you find the moles of electrons transferred? Also, I understand that Ce^4+ is getting reduced, but how is 3I^- getting oxidized? It's oxidation number doesn't change.
Sun Feb 17, 2019 1:35 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: S=qrev/ T
Replies: 3
Views: 377

### Re: S=qrev/ T

I think if it is a constant temperature you can assume that it is a reversible reaction because irreversible reactions have changing temperatures.
Sun Feb 17, 2019 1:25 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: reversible and irreversible processes
Replies: 9
Views: 488

### Re: reversible and irreversible processes

Reversible is expansion/compression against constant pressure, while irreversible is infinitesimal steps of expansion/compression against a changing pressure. Therefore, irreversible does more work, but does not actually happen in real life.
Sun Feb 17, 2019 1:24 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Midterm Question
Replies: 8
Views: 285

### Re: Midterm Question

I think if you used the Cp value 5/2*R you would get a value around 20.785. The value they gave us during the exam was 20.81, so I think if you used either you would get around the same answer.
Sat Feb 09, 2019 9:19 am
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: 9.37 6th Edition
Replies: 1
Views: 101

### 9.37 6th Edition

Why are all the units J.K^-1.mol^-1? For example, in part d, I did [(3 mol)*(151.0 J.K^-1.mol^-1)+(1mol)*(82.59 J.K^-1.mol^-1)]-[(4 mol)*(143.1 J.K^-1.mol^-1)] which equals -36.81 J.K^-1.mol^-1. However, since you're multiplying mol by J.K^-1.mol^-1, shouldn't the units just be J.K^-1?
Fri Feb 08, 2019 9:53 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 9.13 6th Edition
Replies: 1
Views: 90

### 9.13 6th Edition

The answer key uses delta S=nR(ln(T2/T1)). When can you use this instead of delta S=cln(T2/T1)?
Fri Feb 08, 2019 9:38 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Ideal Behavior
Replies: 3
Views: 188

### Ideal Behavior

For 9.13 in the 6th edition, it says "During the test of an internal combustion engine, 3.00 L of nitrogen gas at 18.5 degrees C was compressed suddenly and irreversibly to 0.5 L by driving in a piston. In the process, the temperature of the gas increased to 28.1 degrees C. Assume ideal behavio...
Sun Feb 03, 2019 2:30 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Calibrating the Calorimeter
Replies: 1
Views: 143

### Calibrating the Calorimeter

What does it mean when it says that the calorimeter is calibrated (for example 8.23 and 8.25 in 6th edition)?
Sun Feb 03, 2019 10:11 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: kJ vs J
Replies: 9
Views: 232

### kJ vs J

The textbook switches between giving the answer in kJ and J. Does it matter which one I use?
Tue Jan 29, 2019 6:40 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard Enthalpy of Combustion
Replies: 1
Views: 80

### Standard Enthalpy of Combustion

For 8.57 in the 6th edition, it gives us the standard enthalpies of combustion. In the solution manual, it writes balanced combustion equations for the given reaction and then adds the reactions together to find the final enthalpy. Do we need to do this? I literally added the given enthalpies of com...
Sun Jan 27, 2019 6:01 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard Reaction Enthalpy
Replies: 1
Views: 77

### Re: Standard Reaction Enthalpy

I think it is the enthalpy when all reactants and products are in their standard state at 1 atm. The standard state for a gas is 1 atm, the standard state for a solution is 1 M, and the standard state for a pure liquid or solid is the pure liquid or solid.
Sun Jan 27, 2019 5:57 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Exothermic vs. Endothermic
Replies: 10
Views: 1645

### Re: Exothermic vs. Endothermic

Exothermic reactions favor the formation of products and give off heat. Endothermic reactions favor the formation of reactants and require heat.
Sun Jan 27, 2019 5:55 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Catalysts in Kc
Replies: 6
Views: 280

### Re: Catalysts in Kc

Catalysts don't affect Kc because they only make reactions faster. They don't change the concentrations of the reactants or products.
Sun Jan 20, 2019 6:22 pm
Forum: Ideal Gases
Topic: Ideal Gas as Approximation
Replies: 2
Views: 91

### Ideal Gas as Approximation

On Outline 1, it says we have to be able to identify reactions where the ideal gas law can be used as an approximation. What does this mean?
Sun Jan 20, 2019 5:40 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Biological Examples
Replies: 1
Views: 84

### Biological Examples

On outline 1 it mentions biological examples, such as ATP hydrolysis and osmotic pressure. What should we know about these?
Wed Jan 16, 2019 9:02 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 12.45 6th edition
Replies: 1
Views: 108

### 12.45 6th edition

Can someone explain arylamines, alkylamines, methyl-, and ethyl-? Also, do we have to know these?
Sun Jan 13, 2019 1:36 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 11.49 6th Edition
Replies: 2
Views: 69

### 11.49 6th Edition

Why are solids not included in the ICE table?
Sat Jan 12, 2019 1:27 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 11.45 6th Edition
Replies: 1
Views: 77

### 11.45 6th Edition

What does it mean when it asks if Cl2 or F2 is thermodynamically more stable relative to its atoms? How do you know?
Sat Jan 12, 2019 12:56 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE Table
Replies: 6
Views: 317

### ICE Table

If given the initial concentration/pressure of the reactant(s), are the initial concentrations/pressures of the products always going to be 0 in the ICE table?
Sat Dec 08, 2018 1:25 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Periodic trend of acid strength
Replies: 2
Views: 233

### Re: Periodic trend of acid strength

You can use bond length when referring to an A-H bond like HBr and HCl. However, HBrO2 and HClO2 have the same A-H bond being broken (O-H). Therefore, you have to use electronegativity to determine their strengths instead.
Sat Dec 08, 2018 1:20 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polarity
Replies: 7
Views: 358

### Re: Polarity

It means that there is a difference in electronegativity between the two atoms the bond is connecting.
Sat Dec 08, 2018 1:08 pm
Forum: Naming
Topic: Latin Names
Replies: 2
Views: 115

### Re: Latin Names

My TA's notes have Iron (Ferrate), Copper (Cuprate), Lead (Plumbate), Silver (Argentate), Gold (Aurate), and Tin (Stannate). I would know those, just to be safe.
Sat Dec 01, 2018 10:34 pm
Forum: Lewis Acids & Bases
Topic: Strength of Acids
Replies: 3
Views: 161

### Strength of Acids

Given lewis structures, how can you tell if one acid is stronger than another?
Sat Dec 01, 2018 10:22 pm
Forum: Amphoteric Compounds
Topic: acidic, basic, and amphoteric oxides
Replies: 2
Views: 216

### Re: acidic, basic, and amphoteric oxides

I think amphoteric oxides have both basic and acidic character. For example, H20 can be both an acid and a base, meaning it can donate or accept electrons. They are found diagonally on the periodic table between the metals and the nonmetals near the metalloids.
Sat Dec 01, 2018 5:11 pm
Forum: Naming
Topic: kE in textbook
Replies: 1
Views: 66

### kE in textbook

Hi in the 6th edition of the textbook, toolbox 17.1 says "If there is an ambiguity in which atom is linked to the metal atom, then kE is added to the name in parentheses, where E denotes the connecting atoms (and k is kappa):[Fe(NCS)(OH2)5]2+ thiocyanato(kN)pentaaqua(III) iron [Fe(NCS)(OH2)5]2+...
Sun Nov 25, 2018 10:13 am
Forum: Sigma & Pi Bonds
Topic: HW 4.43
Replies: 1
Views: 48

### HW 4.43

The homework question says: Noting that the bond angle of an sp3 hybridized atom is 109.5 degrees and that of an sp2 hybridized atom is 120 degrees, do you expect the bond angle between two hybrid orbitals to increase or decrease as the s-character of the hybrids is increased? Can someone explain wh...
Sun Nov 25, 2018 10:10 am
Forum: Sigma & Pi Bonds
Topic: Location of Sigma and Pi Bonds
Replies: 5
Views: 149

### Location of Sigma and Pi Bonds

How do you determine where each sigma and pi bond goes?
Sun Nov 18, 2018 8:56 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Dipole-Dipole forces
Replies: 4
Views: 219

### Dipole-Dipole forces

Does everything have dipole-dipole forces unless atoms of the same element are arranged symmetrically around the central atom?
Sun Nov 18, 2018 8:41 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Polar or nonpolar [ENDORSED]
Replies: 1
Views: 285

### Polar or nonpolar[ENDORSED]

For molecules, such as CH2Cl2, that can be drawn in multiple ways, how do you know which one is correct? For example, you could put the two hydrogens and two chlorines next to each other around the central carbon or you could alternate them. This would affect whether the molecule is polar or not, so...
Sun Nov 18, 2018 8:37 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Drawing structures
Replies: 8
Views: 359

### Drawing structures

How do you represent double bonds using the VSEPR method with wedges?
Sat Nov 10, 2018 7:25 pm
Forum: SI Units, Unit Conversions
Topic: Angstrom and SI Units
Replies: 2
Views: 502

### Re: Angstrom and SI Units

No, I believe Dr. Lavelle said this is the only non SI unit we should know.
Sat Nov 10, 2018 6:58 pm
Forum: Bond Lengths & Energies
Topic: Potential Energy Equation
Replies: 1
Views: 111

### Potential Energy Equation

Hi, in class Dr. Lavelle brought up the equation Ep is proportional to alpha1*alpha2/r^6. What does this mean?
Sat Nov 10, 2018 6:39 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: E- configuration
Replies: 3
Views: 234

### Re: E- configuration

When you get to period 3, even though the periodic table makes it look like 4s should go before 3d, it goes afterwards because the 3d orbital has less energy than 4s after 4s is filled. However, when doing the diagram using Aufbau's rule, 4s goes before 3d.
Sun Nov 04, 2018 10:40 am
Forum: Quantum Numbers and The H-Atom
Topic: Drawing orbitals
Replies: 4
Views: 808

### Drawing orbitals

Hi my TA mentioned that we might have to know how to draw the different orbitals like 3px, 3py, and 3pz. Can someone explain how to do this?
Sun Nov 04, 2018 10:38 am
Forum: Quantum Numbers and The H-Atom
Topic: Probability of finding an electron at a certain location
Replies: 1
Views: 133

### Re: Probability of finding an electron at a certain location

Is this the heisenberg uncertainty principle?
Sat Nov 03, 2018 11:04 am
Forum: Trends in The Periodic Table
Topic: Metals, metalloids, and nonmetals
Replies: 3
Views: 194

### Metals, metalloids, and nonmetals

Hi can someone explain how you know if an element is a metal, metalloid, and nonmetals? Also, do we have to know this?
Sat Oct 27, 2018 4:57 pm
Forum: Trends in The Periodic Table
Topic: Homework 2.67b
Replies: 2
Views: 106

### Homework 2.67b

Can anyone explain why carbon has a higher electron affinity than nitrogen?
Sat Oct 27, 2018 4:39 pm
Forum: Trends in The Periodic Table
Topic: Homework 2.59
Replies: 3
Views: 133

### Homework 2.59

The problem asks you to place the ions in order of increasing ionic radius: S^2-, Cl^-, P^3-. I understand that ionic radii decrease from left to right across a period, but I don't get what the exponents do. How do they affect the size of the radius?
Sat Oct 27, 2018 4:14 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Homework 2.45d
Replies: 1
Views: 72

### Homework 2.45d

It asks which element is predicted to have the following ground-state electron configuration: [Rn]7s^2 6d^2. First, why is the 7s before 6d? Also, the answer is Thorium, which I thought was in the f-block? How does that work?
Sat Oct 20, 2018 11:46 am
Forum: Trends in The Periodic Table
Replies: 4
Views: 145

For Chapter 2, are there sections I can skip? For example, Atomic Radius, Ionic Radius, Ionization Energy, Electron Affinity, Inert-Pair Effect, Diagonal Relationships, General Properties of the Elements, etc.
Sat Oct 20, 2018 11:27 am
Forum: *Shrodinger Equation
Topic: Using the Schrodinger Equation
Replies: 3
Views: 447

### Re: Using the Schrodinger Equation

I believe Professor Lavelle said that we just need to understand what it is, and problems where you would have to solve a Schrodinger Equation are too complicated for this course.
Sat Oct 20, 2018 11:06 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 2.43 Electron Configurations
Replies: 1
Views: 42

### 2.43 Electron Configurations

The question asks what is the ground-state electron configuration expected for each of the following elements: (a) silver; (b) beryllium; (c) antimony; (d) gallium; (e) tungsten; (f) iodine? I feel like we didn't go over this in class, and I was wondering if we would have to know this for test two.
Sat Oct 13, 2018 6:55 pm
Forum: Properties of Light
Topic: E=hv
Replies: 13
Views: 528

### E=hv

In the equation E=hv, I know E stands for energy, but specifically what energy? Like threshold energy or energy of the photons?
Sat Oct 13, 2018 6:46 pm
Forum: Properties of Light
Topic: Photoelectric Effect Module #34b
Replies: 1
Views: 32

### Photoelectric Effect Module #34b

How do you solve this? Molybdenum metal must absorb radiation with a minimum frequency of 1.09 x 10^15 s-1 before it can emit an electron from its surface. b. If molybdenum is irradiated with 194 nm light, what is the maximum possible KE of the emitted electrons?
Sat Oct 13, 2018 6:44 pm
Forum: Properties of Light
Topic: Photoelectric Effect Module #28
Replies: 1
Views: 48

### Photoelectric Effect Module #28

How do you solve this? Light hits a sodium metal surface and the velocity of the ejected electron is 6.61x10^5 m.s-1. The work function for sodium is 150.6 KJ.mol-1. a. What is the KE of the ejected electron? b. How much energy is required to remove an electron from one sodium atom? c. What is the f...
Sat Oct 06, 2018 10:52 am
Forum: Empirical & Molecular Formulas
Topic: HW F11
Replies: 4
Views: 235

### HW F11

For part c, I got NH6PO4, which is correct. However, the answer says NH6PO4 or [NH4][H2PO4]. How do you convert NH6PO4 into [NH4][H2PO4] and do we have to know this?
Sat Oct 06, 2018 10:40 am
Forum: Molarity, Solutions, Dilutions
Topic: Changing Units
Replies: 10
Views: 486

### Re: Changing Units

I think in class, he said you could use either. However, sometimes it makes more sense to use one instead of the other. For example, when you're doing an experiment, you would normally measure 16.2 mL rather than 0.0162 L. Both answers would be correct though.
Sat Oct 06, 2018 10:33 am
Forum: SI Units, Unit Conversions
Topic: Chemistry Community Points
Replies: 3
Views: 130

### Re: Chemistry Community Points

I think the TAs said you have until Sunday to complete your posts, so you still have time to get your 3 points. Otherwise, yes, I believe it counts as 0 points for week 1 if you don't do them.