## Search found 55 matches

Sun Mar 18, 2018 8:38 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Standard Gibbs Free Energy for Vaporization of Water
Replies: 2
Views: 1010

### Re: Standard Gibbs Free Energy for Vaporization of Water

Can this be explained conceptually?
Sat Mar 17, 2018 11:02 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Standard Gibbs Free Energy for Vaporization of Water
Replies: 2
Views: 1010

### Standard Gibbs Free Energy for Vaporization of Water

Why is the standard Gibbs Free Energy of the vaporization of water at 100C 0?
Tue Mar 13, 2018 10:37 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 15.63
Replies: 6
Views: 283

### 15.63

In question 15.63, why do we need to subtract 0.59 and where does this value come from?
Tue Mar 13, 2018 10:23 pm
Forum: *Enzyme Kinetics
Topic: 15.67
Replies: 2
Views: 558

### 15.67

Would someone be able to explain why 15.67 uses the ratio of activation energies? i.e. How would I have known to substitute Ea(cat) without looking at the solution manual?
Mon Mar 05, 2018 8:42 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Slow Steps
Replies: 1
Views: 133

### Slow Steps

In lecture on Friday (I believe), Lavelle discussed how the reaction between NO2 and CO in a series of steps in order to determine the rate law. The rate law was determined by the slow step of NO2 and NO2 reacting giving the rate law of k[NO2]^2.... if the slow step had been the reaction between NO3...
Mon Mar 05, 2018 8:38 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: Overall reaction order
Replies: 3
Views: 255

### Re: Overall reaction order

The overall reaction order would be a fraction if changing the concentration of one reactant did not change the rate by a factor of 2 or 4. Similarly, the reaction order can be negative if increasing the concentration of a reactant decreases the rate instead of increasing it.
Mon Mar 05, 2018 8:36 am
Forum: General Rate Laws
Topic: Homework Problem 15.19C
Replies: 5
Views: 312

### Re: Homework Problem 15.19C

For part c) you should see that 8.7=(1.25)(1.25)^2(1.25)^2 *k with each concentration being in mol/L if you use experiment 1... thus, k must have the units L^4*mol^-4*s^-1 in order to cancel with (mol/L)*(mol/L)^2*(mol/L)^2
Mon Feb 19, 2018 8:23 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14.17
Replies: 1
Views: 170

### 14.17

For question 14.17, "Write balanced half-reactions for the redox reaction of an acidified solution of potassium permanganate and iron (II) chloride" ... How do you know which half reactions you are supposed to be using?
Mon Feb 19, 2018 8:03 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: OH- ions
Replies: 1
Views: 117

### OH- ions

In question 14.15 part C, why is KOH added to the cell diagram?
Mon Feb 19, 2018 7:40 pm
Forum: Balancing Redox Reactions
Topic: Oxidation Numbers
Replies: 6
Views: 431

### Re: Oxidation Numbers

Even if the overall charge is neutral?
Mon Feb 19, 2018 7:39 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14.15
Replies: 1
Views: 166

### 14.15

In question 14.15, in the final cell diagram answer, why aren't Ag(s) and AgBr(s) separated by a comma even though they are in the same state?
Mon Feb 19, 2018 6:01 pm
Forum: Balancing Redox Reactions
Topic: Oxidation Numbers
Replies: 6
Views: 431

### Oxidation Numbers

Do elements have oxidation numbers when it's just, for example, O2 or O3?
Mon Feb 12, 2018 9:43 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Example Problem 8.6
Replies: 1
Views: 154

### Example Problem 8.6

In example 8.6 in chapter 8, to calculate the internal energy at constant pressure, why do you have to calculate it in two steps - heating to the final temperature at constant volume, followed by isothermal expansion?
Sun Feb 11, 2018 9:53 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Vaporization of Water
Replies: 1
Views: 174

### Vaporization of Water

Why is the Gibbs Free Energy at 100 (degrees C) for the vaporization of water, zero?
Sun Feb 11, 2018 9:52 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Problem 9.75 Clarification
Replies: 1
Views: 145

### Problem 9.75 Clarification

What is residual entropy and what is a trans-isomer?
Sun Feb 11, 2018 9:50 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Units of S and H
Replies: 4
Views: 484

### Units of S and H

When calculating problems that involve DeltaS and DeltaH, if you multiply the standard enthalpies of formation or standard molar entropies by the number of moles in the balanced chemical equation, why are your answers still in kJ/mol and J/(K*mol)?
Mon Feb 05, 2018 10:47 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Intermolecular Forces
Replies: 2
Views: 191

### Intermolecular Forces

How do the strengths of intermolecular forces affect Gibbs Free Energy?
Mon Feb 05, 2018 10:45 am
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Net Increases in Amount of Gas
Replies: 3
Views: 214

### Net Increases in Amount of Gas

Section 9.8 states that a net increase in the amount of gas usually results in a positive entropy change. Is there ever a situation where that is not the case?
Mon Feb 05, 2018 10:43 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Figure 9.9 in Section 9.6
Replies: 1
Views: 141

### Figure 9.9 in Section 9.6

Would someone be able to explain figure 9.9 in section 9.6 that describes a particle in a box?
Tue Jan 30, 2018 12:51 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Homework 9.5 [ENDORSED]
Replies: 11
Views: 628

### Re: Homework 9.5[ENDORSED]

It goes along with the same concept of q(system)=-q(surroundings) where the heat released by one system must be absorbed by something else and vice versa
Tue Jan 30, 2018 12:47 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Entropy and irreversible/reversible reactions
Replies: 1
Views: 150

### Re: Entropy and irreversible/reversible reactions

Reversible: (One that can be reversed by an infinitesimally small change in variable; i.e. the example where the internal and external pressure of a gas inside a container are equal and a slight change in either would force the piston in one direction or another) Irreversible: (Work done against a c...
Tue Jan 30, 2018 12:34 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 9.11 P is inverse of V
Replies: 2
Views: 167

### Re: 9.11 P is inverse of V

The concept of P is the inverse of V comes from Boyle's Law, "For a fixed amount of an ideal gas kept at a fixed temperature, pressure and volume are inversely proportional."

Meaning, P(1)V(1)=P(2)V(2)
Mon Jan 29, 2018 9:53 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Irreversible vs. Reversible Pathways
Replies: 3
Views: 218

### Irreversible vs. Reversible Pathways

Chapter 9 states, "This independence means that, if we want to calculate the entropy difference between a pair of states joined by an irreversible path, we can look for a reversible path between the same two states and then use Eq. 1 for that path." What is meant by a reversible path compa...
Mon Jan 22, 2018 3:00 pm
Forum: Administrative Questions and Class Announcements
Topic: Formula Sheet - Molar Heat Capacities of Ideal Gases
Replies: 1
Views: 172

### Formula Sheet - Molar Heat Capacities of Ideal Gases

On the Formula Sheet, C(p) and C(v) are listed as (5/2)R and (3/2)R respectively, but in the book, those equations are only for atoms. If we are given an ideal gas such as O2(g)...Do we have to know that linear molecules are C(p)=(7/2)R and C(v)=(5/2)? Or for the tests, is it okay if we use the form...
Sun Jan 21, 2018 1:42 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Sulfur, S(s)
Replies: 1
Views: 126

### Sulfur, S(s)

What is the difference between S(s), rhombic and S(s), monoclinic?
Sun Jan 21, 2018 12:34 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.99 Enthalpies of Formation [ENDORSED]
Replies: 3
Views: 230

### 8.99 Enthalpies of Formation[ENDORSED]

In the solution manual for 8.99, the calculated reaction enthalpy is found by the equation Delta H (RXN) = -153.89 +2(-167.16)-2(-167.16)-0 = -153.89 kJ/mol ...but the balanced chemical equation is 2HCl(aq)+Zn(s) --> H2(g)+ZnCl2(aq) Shouldn't the standard enthalpy of formation for H2 gas be 0? And w...
Sat Jan 20, 2018 11:18 am
Forum: Calculating Work of Expansion
Topic: 8.13 - Understanding the Solution
Replies: 2
Views: 215

### 8.13 - Understanding the Solution

For question 8.13, "In a combustion cylinder, the total energy change produced from the burning of a fuel is -2573 kJ. The cooling system that surrounds the cylinder absorbs 947 kJ as heat. How much work can be done by the fuel in the cylinder?" The answer, 1626 kJ...Is that the amount of ...
Thu Jan 18, 2018 9:06 pm
Forum: Calculating Work of Expansion
Topic: Question 8.27 Conversion
Replies: 2
Views: 181

### Question 8.27 Conversion

In question 8.27, I got to the point of 2.23 L*atm for work, but in the solution manual, where does the 101.325 J*L-1*atm-1 come from?
Mon Jan 15, 2018 3:01 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Units
Replies: 2
Views: 170

### Units

How do I know when my units should be in kJ or in kJ*mol^-1?
Mon Jan 15, 2018 2:41 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Calculations with Bond Enthalpies (67b)
Replies: 1
Views: 153

### Calculations with Bond Enthalpies (67b)

In question 67, part b, the bond enthalpies are listed for O2 and H2, but how do I account for the contribution of carbon as graphite when calculating?
Mon Jan 15, 2018 2:34 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Standard Enthalpies of Formation
Replies: 1
Views: 187

### Standard Enthalpies of Formation

When trying to calculate the standard enthalpy of formation for a compound, I understand you use the reactants in their most stable forms, but how do I know whether the product formed is in the right state?
Mon Jan 15, 2018 11:38 am
Forum: Environment, Fossil Fuels, Alternative Fuels
Topic: Energy Density
Replies: 7
Views: 3727

### Energy Density

How does energy density affect the efficiency of a fuel and for example, how far a car can drive?
Mon Jan 15, 2018 11:35 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Difference in Standard Enthalpy of Formation and Standard Reaction Enthalpy
Replies: 1
Views: 109

### Difference in Standard Enthalpy of Formation and Standard Reaction Enthalpy

What is the difference between the standard enthalpy of formation and the standard reaction enthalpy?
Sat Jan 13, 2018 3:20 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Nonexpansion Work vs. Expansion Work
Replies: 1
Views: 157

### Nonexpansion Work vs. Expansion Work

What is the difference between non expansion work and expansion work, and what does it mean when the book says "at constant volume and no non expansion work" where the change in internal energy is equal to q?
Fri Dec 08, 2017 9:42 pm
Forum: Hybridization
Topic: Bond Angles [ENDORSED]
Replies: 4
Views: 7206

### Re: Bond Angles[ENDORSED]

Oh! So 4 regions of electron density or sp^3 for example would still be tetrahedral?
Fri Dec 08, 2017 9:38 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Space for Additional Complexes [ENDORSED]
Replies: 1
Views: 209

If we are given a coordination compound with a coordination number less than 6, do we assume we can add complexes to the central metal until we reach a coordination number of 6?
Tue Dec 05, 2017 10:14 pm
Forum: Lewis Acids & Bases
Topic: Identifying Oxides as Acidic or Basic (12.17)
Replies: 1
Views: 189

### Identifying Oxides as Acidic or Basic (12.17)

What is the key to knowing if an oxide is acidic or basic?
Tue Dec 05, 2017 9:58 pm
Forum: Bronsted Acids & Bases
Topic: Net Ionic Equations
Replies: 2
Views: 376

### Net Ionic Equations

How do I write a net ionic equation?
Wed Nov 29, 2017 4:11 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Textbook pg. 118 Example [ENDORSED]
Replies: 1
Views: 255

### Textbook pg. 118 Example[ENDORSED]

In my textbook on pg. 118, (in Chapter 4), figure 4.7 gives examples of polar vs. non polar molecules based on their VSEPR shapes... BrF3 is listed under AX3 as non polar, but seeing that BrF3 has a total of 28 valence electrons to use for the Lewis Structure, the central Br atom should have two lon...
Tue Nov 28, 2017 10:05 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Units for K and Q [ENDORSED]
Replies: 5
Views: 675

### Re: Units for K and Q[ENDORSED]

What does K(p) have to be in terms of? bar?
Tue Nov 28, 2017 9:42 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Units for K and Q [ENDORSED]
Replies: 5
Views: 675

### Units for K and Q[ENDORSED]

Even though K and Q do not have units, do the values you use to calculate K and Q need to be in specific units, say, (mol*L^-1)?
Tue Nov 28, 2017 8:57 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Mole Ratios in ICE Tables
Replies: 2
Views: 937

### Mole Ratios in ICE Tables

When using ICE tables to calculate concentrations, do we have to factor in the number of moles of each species. If so, when do those coefficients factor into the calculations?
Tue Nov 28, 2017 5:37 pm
Forum: Hybridization
Topic: Ch 4 Question 75
Replies: 3
Views: 276

### Ch 4 Question 75

After deducing that CH4O is sp^3 tetrahedral, how do I know whether or not the compound is polar?
Tue Nov 28, 2017 5:35 pm
Forum: Hybridization
Topic: Ch 4 Question 95
Replies: 1
Views: 180

### Ch 4 Question 95

When looking at the sigma and pi bonds of CH2=CHCHO, how do you know which orbitals are hybridized and which aren't such as in the case of the C-H bond where the sigma bond is (C2sp^2, H1s)?
Tue Nov 28, 2017 5:33 pm
Forum: Hybridization
Topic: Bond Angles [ENDORSED]
Replies: 4
Views: 7206

### Bond Angles[ENDORSED]

How do I measure the bond angles of hybridized orbitals?
Tue Nov 28, 2017 5:28 pm
Forum: Naming
Topic: (EDTA) and (en) Q17.37
Replies: 1
Views: 191

### (EDTA) and (en) Q17.37

On Question 17.37, parts (c) and (d) contain the symbols (edta) and (en) within the chemical formula. What do these mean and how do I know that edta is hexadentate and en is bidentate?
Mon Nov 27, 2017 3:30 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Net Ionic Equations
Replies: 1
Views: 186

### Net Ionic Equations

When writing the equilibrium expressions for fully dissociated ionic compounds, the book says to use the net ionic equation...Would someone be able to write the steps to finding the net ionic equation as a refresher from high school chem?
Mon Nov 27, 2017 3:14 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Section 11.2 Terminology -"Activities"
Replies: 1
Views: 134

### Section 11.2 Terminology -"Activities"

In Section 11.2 of the book, when calculating the equilibrium constant, K, the authors use the terminology "activities" to describe the general expression for the equilibrium constant. Can we ignore this fact because we are assuming our gases are ideal gases and not real gases? Are "a...
Wed Nov 22, 2017 11:45 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordination Number
Replies: 2
Views: 168

### Coordination Number

What information can you deduce from knowing the coordination number? Why is it important?
Wed Nov 22, 2017 10:17 am
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Localization and Delocalization [ENDORSED]
Replies: 1
Views: 347

### Localization and Delocalization[ENDORSED]

What is the difference between talking about localized bonds with regard to Valence-Bond Theory and delocalized bonds in Molecular Orbital Theory?
Fri Nov 17, 2017 12:15 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: General Understanding of Coordination Sphere
Replies: 2
Views: 335

### General Understanding of Coordination Sphere

What is the general definition and significance of the coordination sphere with transition metals?
Tue Nov 14, 2017 3:45 pm
Forum: Determining Molecular Shape (VSEPR)
Replies: 4
Views: 387

When using VSEPR and Lewis structures to describe radicals, is a lone electron treated as its own region of electron density? How does a lone electron affect the shape?
Tue Nov 07, 2017 4:31 pm
Forum: Lewis Structures
Topic: Resonance Structures
Replies: 1
Views: 231

### Resonance Structures

Do structures such as that for ONF have resonance even though the atoms bonded to the central atom (N) are not the same?
Tue Nov 07, 2017 4:01 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration of Ions
Replies: 2
Views: 184

### Electron Configuration of Ions

For group 13, would someone be able to explain the reasoning behind the elements forming 3+ ions in the context of their electron configurations? Thank you!
Thu Oct 05, 2017 11:23 pm
Forum: Limiting Reactant Calculations
Topic: M19
Replies: 3
Views: 319

### M19

Looking for an explanation for the steps in problem M19 as you go from the grams of product to the formula of the reactant. Thank you!