## Search found 37 matches

Sat Mar 16, 2019 12:41 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Replies: 3
Views: 65

In the book what they have is: At temp T1: ln(k) = ln (A) - Ea/RT1 and at temp T2: ln (K2) = ln (A) - Ea/RT2 Then all they do subtract the first equation from the second equation: ln(k2) = ln (A) - Ea/RT2 - ln (K) = ln (A) - Ea/RT1 = ln(K2)-ln(K) = -Ea/RT2 -Ea/RT1 = ln(K2/K) = -Ea/R (1/T2 - 1/T1) Th...
Sat Mar 16, 2019 12:34 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 6th edition 15.101
Replies: 1
Views: 41

### 6th edition 15.101

For this question, it asks you for the rate law based on the mechanism of the reactant. I understand why we have to substitute in for the [HClO] because it is an intermediate but the final rate law the solutions has is : rate = (K2)(K1/K1') [ClO-][I-]/[OH-]. Why can we leave OH- in the rate law expr...
Fri Mar 15, 2019 7:37 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Replies: 3
Views: 65

You have to use the natural log of the Arrhenius equation: ln (K) = lnA - Ea/R (1/T). Then if you subtract, you can get the form: ln(K2/K1) = Ea/R (1/T2 - 1/T1). From this, you can now plug in the given values to get 39 kj per mol
Fri Mar 15, 2019 7:11 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Replies: 3
Views: 72

Can anyone explain where the .59 comes from? Additionally, isn't the equation ln (k2/K1) = -Ea/R (1/T2 - 1/T1)? So why would the temperature corresponding to T2 come second in the solutions maual?
Tue Mar 12, 2019 9:37 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: 6th edition 15.49
Replies: 2
Views: 90

### 6th edition 15.49

For this question, why can we say that the rate for step 2 is rate=k[HBr][HOBr] when [HOBr] is an intermediate? I thought that you could not include intermediates in the rate law.
Tue Mar 12, 2019 9:24 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Kinetics and Thermodynamics
Replies: 1
Views: 202

### Re: Kinetics and Thermodynamics

Thermodynamics tells you if a reaction is favorable/ likely to happen. Kinetics tells you how fast a reaction happens. For example, thermodynamics tells us that it is energetically favorable for a diamond to decompose into graphite. However, kinetics shows that while it is a favorable reaction to de...
Tue Mar 12, 2019 9:22 pm
Forum: First Order Reactions
Topic: Order of a Reaction
Replies: 2
Views: 64

### Re: Order of a Reaction

In order to tell the order of a reaction, the problem will either have to state it or they will provide experimental data for you to use the method of initial rates to determine the order of the individual reactants. Then the order of the reaction is the sum of all the individual orders of the react...
Mon Mar 11, 2019 10:41 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Melting of ice
Replies: 9
Views: 253

### Re: Melting of ice

The way I looked at this question was to say that if ice was melting, delta H was positive because you are putting heat into the system. Then you can say that delta s is positive because the molecules are going to have more possible positions in a liquid than in a solid. Then if the snow is melting,...
Wed Mar 06, 2019 6:29 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 6th edition 14.37
Replies: 1
Views: 100

### 6th edition 14.37

For part c, why is the standard potential of the reaction negative when the half reaction potentials were 0 and +1.36 and neither half reaction had to be flipped? Additionally, when both pressures and concentrations are given, do you not have to convert the pressure into a concentration? In this que...
Wed Mar 06, 2019 5:32 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 6th edition 14.35
Replies: 3
Views: 102

### 6th edition 14.35

For this question, why does the half reaction In 3+ + 2e- --> In 2+ when there is only a change of 1 e- between In 3+ and In2+? Even in the back of the book the reduction half reaction only has 1 e- so I'm wondering why they have it this way in the solutions manual.
Wed Mar 06, 2019 4:47 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Disproportionation
Replies: 1
Views: 68

### Disproportionation

Could someone please explain what disproportionation is and how we would go about determining if an ion will disproportionate in a solution?
Wed Feb 27, 2019 7:49 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Phases used in a Galvanic Cell
Replies: 3
Views: 74

### Re: Phases used in a Galvanic Cell

I believe liquids can be listed it is just not seen as often. For example, in 6th edition 14.11 question e, the question has a cell diagram with Hg (l) shown.
Wed Feb 27, 2019 7:32 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6th edition 14.13 d [ENDORSED]
Replies: 5
Views: 160

### Re: 6th edition 14.13 d[ENDORSED]

The cell diagram from the book is Au (s) | Au +3 (aq) || Au+ (aq) | Au (s). So the only reason that this is written this way is because the Au (s) can serve as the conductor? For the half reactions in the appendix there is Au 3+ --> Au (s) and Au + --> Au (s) but no Au+ --> Au 3+. Does this have som...
Wed Feb 27, 2019 7:02 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14.11 6th Edition
Replies: 1
Views: 60

### Re: 14.11 6th Edition

For this question, you have to look at which half reaction is occuring at the anode and which is occuring at the cathode. The right side of the cell diagram will always be the cathode and the left the anode. So, for example for question e, you must write the oxidation half reaction for the Sn 4+/Sn ...
Wed Feb 27, 2019 6:57 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: platinum [ENDORSED]
Replies: 6
Views: 179

### Re: platinum[ENDORSED]

So, the Pt is added if there is not a solid on either one or both sides. But, you add it to both sides even if one side already has a solid conductor.
Wed Feb 27, 2019 6:52 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: platinum [ENDORSED]
Replies: 6
Views: 179

### Re: platinum[ENDORSED]

In the sixth edition, for question 14.13, they added platinum to both sides even though I2 (s) was present on one side?
Wed Feb 27, 2019 1:50 pm
Forum: Balancing Redox Reactions
Topic: 14.5 6th edition
Replies: 2
Views: 69

### 14.5 6th edition

I am wondering why on this question you have to add OH and H2O to balance the O3 --> O2 reaction. Why can you not just write 2O3 --> 3O2?
Mon Feb 25, 2019 10:47 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: salt bridge
Replies: 5
Views: 127

### Re: salt bridge

As a battery runs its course, electrons travel from the anode to the cathode. The electrodes will quickly stop flowing if they build up too much on one side. The purpose of the salt bridge is to allow anions to diffuse through the salt bridge from the more negative solution to the more positive solu...
Mon Feb 25, 2019 10:44 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 9.81 6th edition
Replies: 1
Views: 54

### 9.81 6th edition

This asks if Fe3O4 or Fe2O3 is more stable in air. In this question, I understand that you can set up an equation and determine which is more stable based on the sign of delta G, but why can you not instead look at the delta G of formation for each species and say that the more negative one would be...
Tue Feb 12, 2019 11:38 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 9.13 6th Edition
Replies: 1
Views: 52

### Re: 9.13 6th Edition

I think this will be the case if they do not give you enough info in order to solve for moles with PV=nRT
Tue Feb 12, 2019 11:25 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: delta(S) total
Replies: 2
Views: 76

### Re: delta(S) total

Delta S system + delta S surroundings = 0 at equilibrium
Tue Feb 12, 2019 11:24 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 6th edition Example 9.10
Replies: 1
Views: 52

### Re: 6th edition Example 9.10

If it was delta H of the system instead of the surroundings you would just take the negative of the answer. The body is generating heat: the heat 100 J per s is the heat going into the surroundings. The heat leaving the system is -100 J per s so you would just divide this by 293.15 K to find the del...
Tue Feb 12, 2019 11:20 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Isothermal and reversible
Replies: 2
Views: 92

### Re: Isothermal and reversible

In one of the homework questions, sixth edition question 9.47, part b describes an isothermal, irreversible free expansion so from that I would assume that these reactions are possible.
Tue Feb 12, 2019 11:16 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Isothermal vs. Non-Isothermal
Replies: 1
Views: 93

### Re: Isothermal vs. Non-Isothermal

When the system is not isothermal, the equations like work are w= -PdeltaV. When the isothermal factor is added, when the delta v is a series of infintesimal changes so you can integrate: so the equation becomes w= - integral from V1 to V2 of P dv. P can then be replaced with nRT/V from the ideal ga...
Tue Feb 12, 2019 6:16 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: 6th edition 9.75
Replies: 2
Views: 221

### 6th edition 9.75

On this question, trying to calculate the s results in an overflow error in the scientific calculator. 12^6.02 x 10-23 How would we solve this equation for the s without it resulting in an overflow error?
Tue Feb 12, 2019 6:12 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: 6th edition 9.75
Replies: 1
Views: 50

### 6th edition 9.75

For this question, I was confused on how to find the possible states of the cis and trans molecules? Why are there three orientations of the trans and not two?
Tue Feb 12, 2019 6:06 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: 6th edition 9.75
Replies: 1
Views: 227

### 6th edition 9.75

For this question, I was confused on how to find the possible states of the cis and trans molecules? Why are there three orientations of the trans and not two?
Tue Feb 12, 2019 6:03 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: Residual Entropy
Replies: 5
Views: 145

### Re: Residual Entropy

I was wondering if the only time you use the equation delta S=Kb ln W is if you are calculating positional entropy?
Tue Feb 12, 2019 6:02 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: Residual Entropy
Replies: 5
Views: 145

### Re: Residual Entropy

Yes, more possible positions leads to greater residual entropy. Since the equation is delta S= Kb ln W and W is the number of states raised to the number of molecules in the system, the increase in the number of states increases W and therefore increases entropy.
Tue Feb 12, 2019 5:36 pm
Forum: Calculating Work of Expansion
Topic: moles and entropy
Replies: 3
Views: 96

### moles and entropy

When you are solving equations for change in entropy, many of the solutions in the manual assume 1 mol when calculating. When can you assume one mol versus useing PV=nRT to calculate?
Sun Jan 20, 2019 2:10 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 6th edition 11.73
Replies: 1
Views: 45

### 6th edition 11.73

Why does b. favor the reactants if there are the same number of moles on either side of the equation?
Fri Jan 18, 2019 3:24 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Autoprotolysis
Replies: 2
Views: 67

### Re: Autoprotolysis

When water goes through autoprotolysis, it produces a small amount of H30+ and OH-. H20 (l) goes to form OH - (aq) and H30+ (aq). If you write the K expression, it is K = [OH-][H3O+]. When measuring these values in pure water, [OH-] and [H3O+] both equal 1 x 10^-7 and K equals 1 x 10^-14. We call th...
Fri Jan 18, 2019 3:08 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: conjugates
Replies: 3
Views: 82

### Re: conjugates

yes this is due to the conjugate see saw. When the acid is very strong, then the reaction wants to proceed to the right and produce H30+. The conjugate base is then weak because the reaction favors the forward reaction and the reverse reaction (the base accepting a proton) is not favored. The base d...
Fri Jan 18, 2019 3:00 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kp or Kc
Replies: 3
Views: 81

### Re: Kp or Kc

typically if the question gives you a concentration then you would use Kc and if it gave you pressure then you would use Kp. You only use Kp if there are all gases in the reaction so if there are aqueous solutions involved then you need Kc. I believe you technically can use either if the question do...
Thu Jan 10, 2019 6:38 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: what is lechatliers principle [ENDORSED]
Replies: 4
Views: 482

### Re: what is lechatliers principle[ENDORSED]

Le chatlier's principle is defined as "when a stress is applied to a dynamic equilibrium, the equilibrium tends to adjust to minimize the effect of stress". This means for example that when a reactant is added, more product forms to maintain equilibrium. If reactant is removed, more reacta...
Thu Jan 10, 2019 5:39 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Partial Pressure vs. Brackets
Replies: 2
Views: 42

### Re: Partial Pressure vs. Brackets

In a and c, the substances included in the equation are all gases so you do the partial pressure but for b they are aqueous so it is better to do the concentration
Thu Jan 10, 2019 5:36 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Activity
Replies: 3
Views: 61

### Re: Activity

In the book, it says activity is "the effective concentration or pressure of a species J expressed as the partial pressure or concentration of the species relative to its standard value". So I think it describes a non ideal, real chemical potential for a solution rather than just an ideal ...