Search found 30 matches

by Kelly Seto 2J
Thu Mar 15, 2018 11:28 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Reducing agents and standard reduction potential
Replies: 1
Views: 59

Re: Reducing agents and standard reduction potential

A reaction with a very negative standard reduction potential means that that species wants to undergo oxidation, the reverse (hence negative) of reduction, and lose its electrons as much as possible. As it oxidizes, it then causes the other species involved to become reduced as it gains its electron...
by Kelly Seto 2J
Thu Mar 15, 2018 11:22 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: HW 15.63
Replies: 2
Views: 71

Re: HW 15.63

I'm not entirely sure what part of the problem this is in reference to, but -0.59 is the value you can get from
(38 kJ/mol / 8.314 x 10-3kJ/mol K)(1/310 K - 1/298 K)
You don't need ln(A) values at all to solve this problem
by Kelly Seto 2J
Thu Mar 15, 2018 11:15 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: 14.97? Finding Ka?
Replies: 1
Views: 85

Re: 14.97? Finding Ka?

I believe Ka is the acid dissociation constant for HF
by Kelly Seto 2J
Fri Mar 09, 2018 10:57 pm
Forum: *Nucleophiles
Topic: What is a nucleophile? [ENDORSED]
Replies: 6
Views: 271

Re: What is a nucleophile? [ENDORSED]

A nucleophile is a chemical species that is attracted to positively charged particles; it's also in a sense the same as a Lewis base in that it acts as an "electron donor" to form bonds. I'm not sure about the second half of your question though
by Kelly Seto 2J
Fri Mar 09, 2018 12:45 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: Stoichiometric Coefficients
Replies: 2
Views: 196

Re: Stoichiometric Coefficients

Only the given experimental data should be taken into account when determining k and n with initial rates, and the coefficients should not play a role at all
by Kelly Seto 2J
Fri Mar 09, 2018 12:38 am
Forum: First Order Reactions
Topic: Log vs ln
Replies: 9
Views: 367

Re: Log vs ln

I would think it's always preferable to use ln since the first order reaction integrated rate law is based on the exponential decay equation that uses e
by Kelly Seto 2J
Tue Feb 27, 2018 6:58 pm
Forum: First Order Reactions
Topic: 15.23 (c)
Replies: 1
Views: 64

Re: 15.23 (c)

The increase in the concentration of B is directly linked to a decrease in the concentration of A, and this decrease is modeled by (2 mol A/1 mol B)(.034 mol B/L), which is the amount of A that had to be used to produce the 0.34 M of B. Subtracting this amount from the initial concentration allows u...
by Kelly Seto 2J
Tue Feb 27, 2018 6:51 pm
Forum: General Rate Laws
Topic: Finding reaction rate [ENDORSED]
Replies: 5
Views: 147

Re: Finding reaction rate [ENDORSED]

Always moles for concentrations
by Kelly Seto 2J
Tue Feb 27, 2018 6:42 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: 15.3 [ENDORSED]
Replies: 7
Views: 190

Re: 15.3 [ENDORSED]

In regards to the rate of formation of O 2 , first we find the rate of rxn for NO 2 which is the change in concentration over the change in time (130 mmol x L^-1 / 20 sec) giving us 6.5 mmol/sec The we see from the coefficients that the rate of formation of oxygen is 1/2 that of NO 2 , so it should ...
by Kelly Seto 2J
Fri Feb 23, 2018 8:04 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Solving for Q when given molarity and partial pressure
Replies: 3
Views: 141

Re: Solving for Q when given molarity and partial pressure

Both molarity and partial pressures (in atm) can be entered into the reaction quotient, so for this it would be
(0.075M)2 x 1 atm / (1.0 M)2 x 1 atm, and any other value for partial pressure could be entered if stated in the problem as long as its in atm
by Kelly Seto 2J
Fri Feb 23, 2018 2:09 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: 14.33
Replies: 2
Views: 116

Re: 14.33

In this case, it means Tl+ is being both oxidized and reduced to become two different products, Tl3+ and Tl(s)
by Kelly Seto 2J
Fri Feb 23, 2018 2:02 pm
Forum: Balancing Redox Reactions
Topic: Reaction E [ENDORSED]
Replies: 5
Views: 145

Re: Reaction E [ENDORSED]

E values are intensive properties, meaning that their values don't scale with the other components of the reaction
by Kelly Seto 2J
Fri Feb 16, 2018 2:25 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Water in cell diagram
Replies: 3
Views: 92

Re: Water in cell diagram

I believe it's because many of the species are stated as being aqueous in these reactions, so the water is assumed to be present. Also water is neutral so it doesn't really contribute anything to the electron balance
by Kelly Seto 2J
Fri Feb 16, 2018 2:16 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell diagram acidic/basic
Replies: 3
Views: 77

Re: Cell diagram acidic/basic

Yes because they contribute to the electron balance
by Kelly Seto 2J
Fri Feb 16, 2018 2:10 pm
Forum: Balancing Redox Reactions
Topic: Acidic Conditions
Replies: 2
Views: 56

Re: Acidic Conditions

If the conditions are acidic you balance the half equations using H3O+ ions and if they're basic you balance using OH- ions
by Kelly Seto 2J
Fri Feb 09, 2018 4:31 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 9.69? I am in need of guidance please :)))
Replies: 1
Views: 91

Re: 9.69? I am in need of guidance please :)))

You were correct in multiplying the second equation by 3, but you need to also multiply the third equation by three because the 6 e- produced in the 2nd equation are going to be part of the reactants in the 3rd equation, which in its current state only shows 2 e-. These two equations can be combined...
by Kelly Seto 2J
Fri Feb 09, 2018 4:08 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Self test 8.14A
Replies: 2
Views: 106

Re: Self test 8.14A

C6H12O6 + 6O2 -> 6CO2 + 6H2O

Then Products minus Reactants

6(-393.51 kj/mol) + 6(-285.83 kj/mol) - (-1286 kj/mol)

Which gave me -2808 kj/mol

It seems that we did the same method, maybe one of your signs was just mixed up or something
by Kelly Seto 2J
Fri Feb 09, 2018 3:47 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Delta G= Wmax
Replies: 8
Views: 298

Delta G= Wmax

Can someone explain what Wmax means? Also why are delta G and Wmax equal at constant T and P? What is the relationship between the two?
by Kelly Seto 2J
Fri Feb 02, 2018 1:27 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Question about equation?
Replies: 3
Views: 96

Re: Question about equation?

C is the just heat capacity of the system which we need to use in order to understand how much energy is needed to cause the temperature change in question. I don't think that there is a way to go about solving these without knowing the heat capacity for the system, however most of the questions wan...
by Kelly Seto 2J
Fri Feb 02, 2018 1:18 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Free Energy and Pressure
Replies: 4
Views: 103

Re: Free Energy and Pressure

Let's look at our equation dG = dH - TdS We remember that dH = dU + PdV, so any increase in pressure will result in a larger dH value If a larger dH value is entered into the equation at constant temperature, we get dG = dH - dS resulting in a large dG, or free energy, value as a result Therefore, a...
by Kelly Seto 2J
Fri Feb 02, 2018 12:50 am
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Extensive/Intensive Property [ENDORSED]
Replies: 4
Views: 145

Re: Extensive/Intensive Property [ENDORSED]

Extensive properties depend of the amount of substance or matter measured while intensive properties, like boiling point and density, do not
by Kelly Seto 2J
Fri Jan 26, 2018 2:31 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Exercise 8.45
Replies: 1
Views: 92

Re: Exercise 8.45

The standard enthalpy of formation for this reaction basically means that 358.8 kJ are absorbed per mole of S 8 OR 4 moles of C OR 4 moles of CS 2 , so it can't be written as kJ/mol. However, since this reaction only uses one mole of S 8 , then it makes sense that it's (1.25 mol S 8 )(358.8 kJ/ 1 mo...
by Kelly Seto 2J
Fri Jan 26, 2018 2:23 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Question 8.55
Replies: 1
Views: 91

Re: Question 8.55

I think Lavelle said that it was a typo in the book and that the O2 in the second rxn is supposed to be 3/2, not 1, lol
by Kelly Seto 2J
Fri Jan 26, 2018 2:18 am
Forum: Phase Changes & Related Calculations
Topic: Hw #8.49 standard state
Replies: 4
Views: 181

Re: Hw #8.49 standard state

I think that it's just the nature of the textbook that when no explicit information about the conditions is given, it means that the reaction is occurring under standard conditions (298 K for thermodynamics)
by Kelly Seto 2J
Fri Jan 19, 2018 4:07 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Problem 8.65
Replies: 1
Views: 85

Re: Problem 8.65

I'm sure there are multiple ways to do this, but what I did was: 2NO + O 2 -> 2NO 2 H = -114.1 kJ The standard enthalpy of formation for NO is 90.25 kJ and for O 2 , as a pure element, is 0 so 2(NO 2 ) - (2(90.25 kJ)+ 0 kJ) = -114.1 kJ // solving for NO 2 gives you 33.2 kJ Then: 4NO 2 + O 2 -> 2N 2 ...
by Kelly Seto 2J
Fri Jan 19, 2018 3:56 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: C(v) and C(p)
Replies: 3
Views: 110

Re: C(v) and C(p)

Cp is greater than Cv because at constant volume, no work is being done so Cp is just equivalent to dU, but under constant pressure, expansion work takes place so you have to add the energy used for work (PdV) to dU
by Kelly Seto 2J
Fri Jan 19, 2018 3:46 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 8.19b
Replies: 1
Views: 74

Re: 8.19b

1.30 x 10^5 J is the amount of heat needed to raise the temperature of the water to 100.0 C 1.45 x 10^5 J is the total amount of heat needed to raise the temperature of both the water and the copper to 100.0 C, obtained by adding 1.30 x 10^5 J (water) with 1.48 x 10^4 J (copper). Then you can find t...
by Kelly Seto 2J
Fri Jan 12, 2018 3:28 pm
Forum: Phase Changes & Related Calculations
Topic: Heat Enthalpies We Need to Know
Replies: 3
Views: 146

Re: Heat Enthalpies We Need to Know

No, I believe he will provide the necessary heat capacities and enthalpies on the tests
by Kelly Seto 2J
Thu Jan 11, 2018 5:00 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.49
Replies: 5
Views: 181

Re: 8.49

I think if there is no temperature explicitly stated, 298 K is just the standard temperature used in thermodynamics
by Kelly Seto 2J
Thu Jan 11, 2018 4:47 pm
Forum: Phase Changes & Related Calculations
Topic: Compression vs Expansion
Replies: 3
Views: 167

Re: Compression vs Expansion

Yes. Since work (at constant external pressure) is calculated by w= -P*delta V where delta V is (Vf-Vi): Any expansion will give us a positive delta V value as V final > V initial , resulting in a negative value for work. Similarly for compression, the delta V value will be negative as V final < V i...

Go to advanced search