## Search found 56 matches

Sat Mar 17, 2018 12:26 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Q7b Lyndon's Review
Replies: 6
Views: 357

### Re: Q7b Lyndon's Review

Adding on, we knew we needed to use the unique rate because it asked for the rate of formation of product E, instead of just the rate of the reaction as a whole.
Mon Mar 12, 2018 2:24 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Reaction Profiles
Replies: 2
Views: 195

### Re: Reaction Profiles

What's the difference between using Gibbs Free Energy and potential energy?
Mon Mar 12, 2018 11:48 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: 15.89 reaction profile
Replies: 1
Views: 148

### 15.89 reaction profile

The intermediate equations for the overall reaction, 2 NO(g) + 2 H2(g) -> N2(g) + 2 H2O(g) are: Step 1: NO + NO -> N2O2 Step 2: N2O2 + H2 -> N2O + H2O Step 3: N2O + H2 -> N2+ H2O We determined that step 2 was the slow step and step 1 was at equilibrium. How do you estimate what the activation energy...
Wed Mar 07, 2018 11:07 am
Forum: First Order Reactions
Topic: Example 15.3
Replies: 2
Views: 208

### Re: Example 15.3

The decomposition is happening at 338K. k changes with temperature, which is why table 15.1 shows different values of k depending on the temperature of the reaction. It would be 3.7x10^-5 if the reaction was happening at 298K.
Wed Mar 07, 2018 9:59 am
Forum: Zero Order Reactions
Topic: zeroth order rate
Replies: 4
Views: 389

### Re: zeroth order rate

Since rate=k[A]^0, it would make sense that the rate for a zeroth order reaction (assuming there are no other reactants) is k.
Wed Mar 07, 2018 9:40 am
Forum: Zero Order Reactions
Topic: zero order rate?
Replies: 14
Views: 817

### Re: zero order rate?

This is true! You can see from the equation [A]=-kt+[A]o that the concentration of A changes only as a result of k and time, not because of its own concentration like in the first order equation (that uses ln[A]) or the second order equation (that uses 1/[A]).
Sun Mar 04, 2018 4:00 pm
Forum: First Order Reactions
Topic: Pseudo-1st-Order
Replies: 6
Views: 411

### Re: Pseudo-1st-Order

Are there textbook problems that correlate to this concept?
Sat Mar 03, 2018 3:54 pm
Forum: General Rate Laws
Topic: 15.3 partb ?
Replies: 3
Views: 186

### Re: 15.3 partb ?

I thought that the general structure for a rate law looked something like this: Rate=k[A]^n [B]^m (if the reaction had reactants A and B with orders n and m). Secondly, you multiply by the mole ratio because 6.2 x -3 itself gives the rate of reaction for NO2, not O2. Since 2 moles of NO2 make 1 mole...
Sat Mar 03, 2018 3:08 pm
Forum: General Rate Laws
Topic: half-life
Replies: 8
Views: 413

### Re: half-life

Half life is the time (represented in equations by t1/2) required for the concentration of a reactant to reduce to half of its initial value
Thu Mar 01, 2018 10:02 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Order of the Reaction [ENDORSED]
Replies: 3
Views: 226

### Re: Order of the Reaction[ENDORSED]

You can determine the order of a reaction by looking at experimental data and how changing concentrations changes initial rates (such as in problem numbers 15.17 and 15.19). Other than this, I think they have to give you the order. I don't think you are able to tell just by looking at a reaction equ...
Tue Feb 20, 2018 10:21 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: When to include electrolyte in cell diagram
Replies: 1
Views: 128

### When to include electrolyte in cell diagram

Do you only include an electrolyte (such as KOH in 14.15c) in a cell diagram if it states that it is a battery? and if so or if not, why?
Mon Feb 19, 2018 10:46 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Acidic vs. Basic
Replies: 2
Views: 170

### Re: Acidic vs. Basic

Also, I found it very helpful to read how the book explains the difference in balancing acidic and basic equations on pages 563-569
Mon Feb 19, 2018 10:40 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagram Order (14.11) [ENDORSED]
Replies: 4
Views: 335

### Re: Cell Diagram Order (14.11)[ENDORSED]

I have a similar question and also on part c why is it written as ||Ce4+,Ce3+| because I thought it was supposed to be written as ||Ce4+|Ce3+ There is a comma because they are both aqueous and | indicates a change in phase. Also, I don't think the order for that matters because they are both mixed ...
Mon Feb 19, 2018 10:35 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 9.15 cell diagrams [ENDORSED]
Replies: 1
Views: 180

### 9.15 cell diagrams[ENDORSED]

I am confused with multiple parts of this problem in regards to how to write out the cell diagram: Write the half-reactions and devise a galvanic cell (write a cell diagram) to study each of the following reactions: (a) AgBr(s) <--> Ag+ (aq) + Br- (aq), a solubility equilibrium (b) H+ (aq) + OH- (aq...
Sat Feb 17, 2018 10:42 am
Forum: Balancing Redox Reactions
Topic: Oxidizing vs. Reducing Agent
Replies: 7
Views: 398

### Re: Oxidizing vs. Reducing Agent

So, by looking at a half reaction, you can tell if its an oxidizing agent if electrons are on the reactants side and you can tell if its a reducing agent if the electrons are on the products side?
Wed Feb 14, 2018 9:36 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 11.111 [ENDORSED]
Replies: 3
Views: 281

### Re: 11.111[ENDORSED]

I thought about it the same way that you did but, because the first reaction is ten times the second reaction, you would actually divide (not multiply) the first K value by ten to find the second K value. Then you can solve for dG and you should get the right answer.
Mon Feb 12, 2018 2:27 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: calculating q and w in isochoric systems
Replies: 3
Views: 228

### Re: calculating q and w in isochoric systems

Ok that makes sense. Thank you!
Mon Feb 12, 2018 1:58 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: calculating q and w in isochoric systems
Replies: 3
Views: 228

### calculating q and w in isochoric systems

What equations do we use to find q and w when there is a change in pressure in an isochoric system (a system where the volume doesn't change)? An example of them asking for this is #4 on the practice midterm.
Sun Feb 11, 2018 8:55 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Practice Midterm #3A
Replies: 2
Views: 224

### Practice Midterm #3A

Lex Luthor is trying to design a gaseous mixture of Krypton gas and Helium gas to make Superman weak and have a high voice at the same time! But first, he wants to quickly review entropy. He finds a sealed box that has two compartments. He puts 9.00 g of Helium gas in the first compartment, and 125g...
Sun Feb 11, 2018 6:54 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.49
Replies: 3
Views: 230

### Re: 8.49

Kyle Sheu 1C wrote:Under conditions of constant pressure, deltaH = q because the work of expansion terms cancel out:

H = U + PV
deltaH = deltaU + PdeltaV
deltaH = q + w +PdeltaV
w = -PexdeltaV
deltaH = q - PdeltaV + PdeltaV

deltaH = q

Is there a situation where deltaH does not equal q that we need to know?
Sat Feb 10, 2018 10:18 pm
Forum: Calculating Work of Expansion
Topic: Expansion work done on the system
Replies: 1
Views: 159

### Expansion work done on the system

8.47 states that 22kJ of expansion work is done on the system (and thus the work is positive). I thought that a system could only be expanded if it is doing the work itself and only compressed if work is being done on it. Am I misunderstanding this concept or the question?
Wed Feb 07, 2018 10:43 pm
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: 9.25 Calculator Error
Replies: 1
Views: 145

### Re: 9.25 Calculator Error

Because it is part of the natural log, you can bring 6.03x10^23 down from the exponent so that you are multiplying it instead outside of the natural log. When I did it this way, my calculator was able to process it!
Wed Feb 07, 2018 10:34 pm
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: Boltzmann
Replies: 3
Views: 184

### Re: Boltzmann

Also, when you multiply it by Avogadro's number, 6.03x10^23, you get the gas constant, R, that is also on our equation sheet
Mon Feb 05, 2018 10:40 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 9.85
Replies: 2
Views: 236

### 9.85

The question states: Potassium nitrate dissolves readily in water, and its enthalpy of solution is 34.9 kJ mol 1. (a) Does the enthalpy of solution favor the dissolving process? (b) Is the entropy change of the system likely to be positive or negative when the salt dissolves? (c) Is the entropy chan...
Sun Feb 04, 2018 6:51 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: conceptual question about change in entropy due to both temp and vol [ENDORSED]
Replies: 3
Views: 214

### Re: conceptual question about change in entropy due to both temp and vol[ENDORSED]

Is there a reason you do it in that order? Or would you get the same answer if you changed the temperature first with a constant volume?
Sun Feb 04, 2018 3:17 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Difference between deltaS(tot), deltaS and deltaS(surr)
Replies: 5
Views: 402

### Re: Difference between deltaS(tot), deltaS and deltaS(surr)

I agree with the comments above. It is also worth noting that conceptually, deltaS(tot) is the change in entropy of the universe, the combination of deltaS and deltaS of the surroundings. DeltaS is the change in entropy of the system and deltaS(surr) is the change in entropy of the surroundings, me...
Sat Feb 03, 2018 3:36 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Difference between deltaS(tot), deltaS and deltaS(surr)
Replies: 5
Views: 402

### Difference between deltaS(tot), deltaS and deltaS(surr)

Some questions in the book (such as #47) ask you to find each of these values individually. What is the conceptual difference between each of these terms? and how what is different about how you calculate them?
Tue Jan 30, 2018 12:08 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 9.11 P is inverse of V
Replies: 2
Views: 168

### 9.11 P is inverse of V

The question states: Calculate the entropy change when the pressure of 1.50 mol Ne(g) is decreased isothermally from 15.0 atm to .500 atm. Assume ideal behavior. The solutions manual says the equation for this is deltaS=nRln(P1/P2) instead of P2/P1 because "P is the inverse of V for ideal gases...
Tue Jan 23, 2018 2:15 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: HW #41
Replies: 1
Views: 96

### Re: HW #41

We use the specific heat capacity of water in its liquid state because, before the water changes temperature, it goes through a phase change from ice to liquid water. That is why there are two parts to the side of the equation dealing with the enthalpy as a result of the ice cube. The first part is ...
Tue Jan 23, 2018 2:08 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 3/2RT
Replies: 4
Views: 312

### Re: 3/2RT

I don't think so because I don't remember going over it in class but I could be wrong I know for a fact that we didn't go over the formula in Dr. Lavelle's 11am lecture, but I'm not sure if it was brought up in the 1pm lecture. He didn't go over it in the 1pm lecture either. I would assume that he ...
Tue Jan 16, 2018 9:26 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Problem 8.75 (b)
Replies: 3
Views: 164

### Re: Problem 8.75 (b)

Drawing the lewis structures of the reactants and product helped me understand this one. When you do this, you can see more clearly that, though there are a lot of bond within each of the reactants, not all of them are broken to create the product. Looking at the lewis structure you can see the bond...
Tue Jan 16, 2018 9:19 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy of formation vs reaction enthalpy
Replies: 2
Views: 107

### Enthalpy of formation vs reaction enthalpy

What is the difference in the definition between enthalpy of formation and reaction enthalpy?
Mon Jan 15, 2018 4:22 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.67b
Replies: 1
Views: 126

### 8.67b

In the solutions manual, it tells us that it takes 717kJ/mol to "atomize 1 mol C(gr)". What does this mean and where does the number come from? I can't find it in the tables in the book that the problem tells us to use.
Fri Jan 12, 2018 10:50 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Type of system for mercury in thermometer
Replies: 5
Views: 583

### Re: Type of system for mercury in thermometer

Yes, it is a closed system because heat is absorbed or released in a thermometer causing the mercury to rise and fall, but the amount of mercury in the thermometer will never change. If it were an open system then there would also have to be a way for the mass of mercury to enter the surroundings.
Thu Jan 11, 2018 6:12 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.57
Replies: 1
Views: 138

### 8.57

This is number 57: Determine the reaction enthalpy for the hydrogenation of ethyne to ethane, C2H2(g) + 2 H2(g) -> C2H6(g), from the following data: Hc (C2H2, g)=-1300. kJ·mol^-1, Hc (C2H6, g)= -1560. kJ·mol^-1, Hc (H2, g)= -286 kJ·mol^-1. Is the c subscript important to answering this problem? What...
Thu Jan 11, 2018 5:46 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Question 8.55
Replies: 1
Views: 139

### Re: Question 8.55

I think the 3/2 was added in the second equation because it wasn't balanced initially. In the equation given in the problem, there are 2 oxygens on the reactant side and 3 on the product side. When you add the 3/2 to just the oxygen on the reactant side, the equation is balanced.
Tue Dec 05, 2017 7:40 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Electron withdrawing power
Replies: 1
Views: 182

### Re: Electron withdrawing power

I believe that, when dealing with a carboxylic acid, the most important part to look at for electron withdrawing power is not the carboxyl group but what is attached to the carbon. For example, CCl3COOH has a large amount of electron withdrawing power because of the three electronegative chlorine at...
Tue Dec 05, 2017 7:34 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: 12.63
Replies: 1
Views: 157

### 12.63

The question states: The percentage deprotonation of benzoic acid in a 0.110 m solution is 2.4%. What is the pH of the solution and the Ka of benzoic acid? In class we learned that if Ka is less than 10^-2 or if deprotonation is less than 5%, then we can assume the change in molarity is negligible a...
Mon Dec 04, 2017 11:08 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: 12.29d
Replies: 2
Views: 276

### 12.29d

Calculate the pH and pOH of each of the following aqueous solutions of strong acid or base: (d) 2.00 mL of 0.175 m KOH(aq) after dilution to 0.500 L I understand the concept of finding pH and pOH but I am stuck on this question because I do understand how they got the molarity for the dilution. In t...
Sat Dec 02, 2017 8:22 pm
Forum: Amphoteric Compounds
Topic: 12.17 [ENDORSED]
Replies: 9
Views: 1097

### Re: 12.17[ENDORSED]

You can always try drawing out lewis structures and seeing if the compound can give, receive, or both give and receive lone pairs. If it can do both then its amphoteric. That's how I'd go about it - I dont really know of any other way. How can you tell by looking at the lewis structure if a compoun...
Tue Nov 21, 2017 6:49 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K and Q
Replies: 2
Views: 198

### K and Q

What is the difference between K and Q conceptually and in how you calculate them?
Tue Nov 21, 2017 6:36 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Homework 17.37
Replies: 1
Views: 183

### Re: Homework 17.37

Bidentate means that the one ligand attaches to the central metal atom in 2 places and hexadentate means that the ligand attaches in 6 places. Each of these places that the ligand attaches to counts toward the coordination number. For part c, that means that each ethylenediamine (en) adds 2 toward t...
Tue Nov 14, 2017 4:16 pm
Forum: Hybridization
Topic: Relative Orientations (4.31)
Replies: 1
Views: 161

### Relative Orientations (4.31)

#31 on the homework asks us to state the relative orientations of the following hybrid orbitals: sp^3, sp, sp^3d^2, and sp^2. What does relative orientation mean and how are we supposed to determine it?
Tue Nov 14, 2017 3:19 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Dipole Moment
Replies: 3
Views: 181

### Dipole Moment

I'm confused on how you can tell which direction the dipole moments of each atom in a molecule go. Can anyone clarify that concept?
Thu Nov 09, 2017 11:15 am
Forum: Lewis Structures
Topic: 3.41
Replies: 2
Views: 178

### Re: 3.41

H2C(NH2)COOH This was my thought process when doing the problem: start with the two carbons in the center because it has the highest ionization energy. Then, from the way the equation is written, you can tell that NH2 will stem off of one of those carbons (with only N connecting to C). From there, I...
Tue Nov 07, 2017 3:10 pm
Forum: Octet Exceptions
Topic: Beryllium exception
Replies: 4
Views: 720

### Beryllium exception

In 3.67, the central Beryllium atom in BeCl2 is allowed to only have 4 electrons. Why is this an exception?
Sun Nov 05, 2017 5:22 pm
Forum: Lewis Structures
Topic: 3.41 part c
Replies: 2
Views: 212

### 3.41 part c

When drawing a Lewis structure for glycine, H2C(NH2)COOH, are there rules I should know to determine which atoms are bonded together in the structure?
Sun Nov 05, 2017 1:52 pm
Forum: Ionic & Covalent Bonds
Topic: #25 on Chapter 3
Replies: 6
Views: 493

### Re: #25 on Chapter 3

Is there a reason I should know for why this rule works?
Thu Oct 26, 2017 10:52 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration Exceptions [ENDORSED]
Replies: 3
Views: 313

### Electron Configuration Exceptions[ENDORSED]

Do the exceptions with copper and chromium that we talked about in class continue with all of the elements in the same groups (five and eleven), like silver and gold for copper and molybdenum for chromium?
Thu Oct 26, 2017 10:42 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electrostatic Coulomb Potential Energy
Replies: 1
Views: 243

### Electrostatic Coulomb Potential Energy

I have written that (q1*q2)/r is the equation for this but I'm not sure what exactly that all means and how we are supposed to calculate it or apply this concept. Could someone explain this a bit more?
Thu Oct 19, 2017 8:51 pm
Forum: *Shrodinger Equation
Topic: Ψ^2
Replies: 2
Views: 211

### Ψ^2

In my notes, I wrote down that Ψ^2=e-*p and that this is the distribution of electrons. Can someone explain this concept? I'm not sure I understand it or wrote it down correctly.
Thu Oct 19, 2017 8:38 pm
Forum: *Shrodinger Equation
Topic: Schrodinger Equation
Replies: 3
Views: 218

### Re: Schrodinger Equation

Lavelle introduced the equation in class to us for conceptual purposes only so that we can know where the orbitals come from. We won't have to calculate the equations in this class.
Thu Oct 12, 2017 11:48 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Replies: 3
Views: 377

In class, Lavelle told us to use a different form of the Rydberg equation (En=-hR/(n^2) than what is in the book. I am trying to use that one to solve this problem but I keep getting an answer that does not make sense. Can anyone walk me through how to use that equation solve it or is it best to use...
Thu Oct 12, 2017 11:36 am
Forum: Properties of Light
Topic: Prefix Conversion
Replies: 12
Views: 735

### Re: Prefix Conversion

I usually make sure to do it before the problem because most of the time throughout the problem you will be doing dimensional analysis with values that are in meters, not nm (such as velocity).
Thu Oct 05, 2017 11:49 am
Forum: Accuracy, Precision, Mole, Other Definitions
Replies: 1
Views: 246