Search found 30 matches

by Ashley Macabasco 2K
Thu Mar 15, 2018 2:01 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: k' reverse reaction constant
Replies: 6
Views: 302

Re: k' reverse reaction constant

In K=k/k', K refers to the equilibrium constant which can also be found by [products]/[reactants]. For the reaction A+B-->C+D k = rate/[A][B] and k' = rate/[C][D]. k/k' would then equal (rate/[A][B])([C][D]/rate) where the rates would cancel leaving [C][D]/[A][B] or [products]/[reactants].
by Ashley Macabasco 2K
Thu Mar 15, 2018 1:50 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14.17?
Replies: 2
Views: 158

Re: 14.17?

In an acidic solution potassium permanganate and iron(II) chloride will dissociate into K+ ions and permanganate and Cl- ions and iron respectively. Because these ions dissociate they are not included in the half-reactions.
by Ashley Macabasco 2K
Thu Mar 15, 2018 1:47 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Delta Hc
Replies: 1
Views: 519

Re: Delta Hc

I believe that the first equation q = (Cv)(delta T) stems from the equation q=n(C)(deltaT T). The first equation does not include mole because the C value given is in terms of kj/C and so I believe that you can assume that the moles were already taken into account. I am unsure of where the second eq...
by Ashley Macabasco 2K
Thu Mar 08, 2018 8:09 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: unit of concentration [ENDORSED]
Replies: 4
Views: 305

Re: unit of concentration [ENDORSED]

I believe you must only convert mmol to mol or vice versa if the question explicitly states to do so.
by Ashley Macabasco 2K
Thu Mar 08, 2018 8:03 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Intermediate [ENDORSED]
Replies: 7
Views: 218

Re: Intermediate [ENDORSED]

Intermediates are formed in one step and the consumed in the next, so the intermediate will be the species that is present in the steps but not present in the final equation.
by Ashley Macabasco 2K
Thu Mar 08, 2018 8:01 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: to find k
Replies: 4
Views: 244

Re: to find k

From my knowledge and the homework problems, k seems to be the same throughout experimental data regardless of the concentrations.
by Ashley Macabasco 2K
Wed Feb 28, 2018 10:48 am
Forum: Balancing Redox Reactions
Topic: Balancing number of electrons
Replies: 10
Views: 366

Re: Balancing number of electrons

It does not matter what coefficient you use as long as the electrons cancel out in the end because you can always simplify the equations.
by Ashley Macabasco 2K
Tue Feb 27, 2018 9:06 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell diagram order
Replies: 4
Views: 154

Re: Cell diagram order

Usually the oxidation (anode) is written on the left and the reduction (cathode) is written on the right. This can be remembered by R in reduction also standing for right.
by Ashley Macabasco 2K
Tue Feb 27, 2018 9:05 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Cell Potential
Replies: 9
Views: 2325

Re: Cell Potential

Because R, T and F are constants at standard conditions, the second equation is the same as the first equation with the constants computed into a single constant.
by Ashley Macabasco 2K
Fri Feb 23, 2018 1:08 am
Forum: Balancing Redox Reactions
Topic: Cell Diagram [ENDORSED]
Replies: 7
Views: 254

Re: Cell Diagram [ENDORSED]

Regardless of if the compounds are on the oxidation or reduction side, each compound in a different phase will be separated.
by Ashley Macabasco 2K
Fri Feb 23, 2018 1:04 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 14.31
Replies: 6
Views: 237

Re: 14.31

If E(cathode)>E(anode) then K>1 and products are favored.
by Ashley Macabasco 2K
Fri Feb 23, 2018 1:02 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell diagram
Replies: 4
Views: 178

Re: Cell diagram

From what I have seen the aqueous compounds are written closest to the middle, the closest to the salt bridge and then the solids are farthest compounds from the salt bridge. Liquids and gases are then written in between.
by Ashley Macabasco 2K
Sun Feb 18, 2018 4:01 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: reversible system
Replies: 9
Views: 418

Re: reversible system

For a reversible system, delta S total would equal zero.
by Ashley Macabasco 2K
Sat Feb 17, 2018 2:25 pm
Forum: Balancing Redox Reactions
Topic: Oxidizing vs. Reducing Agent
Replies: 7
Views: 239

Re: Oxidizing vs. Reducing Agent

An oxidizing agent gains electrons which can be seen through a half-reaction. The reducing agent then loses electrons.
by Ashley Macabasco 2K
Sat Feb 17, 2018 2:20 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: s vs. delta s
Replies: 7
Views: 285

Re: s vs. delta s

Justin Folk 3I wrote:I thought we can only measure change in entropy?

Positional entropy does not measure the change in entropy, but the entropy possible through the number of particles and the position of such particles in the formula S = klnW.
by Ashley Macabasco 2K
Sat Feb 10, 2018 4:12 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: When to use + sign
Replies: 11
Views: 374

Re: When to use + sign

You should always use a + or - sign when doing change calculations to determine whether something is being lost or gained through a reaction.
by Ashley Macabasco 2K
Sat Feb 10, 2018 4:02 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 8.101 (c) and (f)
Replies: 3
Views: 197

Re: 8.101 (c) and (f)

From my understanding, internal energy is found by the work and heat of a system so even if temperature is constant, the internal energy can change with the amount of work done.
by Ashley Macabasco 2K
Sat Feb 10, 2018 12:27 pm
Forum: Van't Hoff Equation
Topic: Derivation
Replies: 9
Views: 423

Re: Derivation

I would suggest knowing how to use the equations and how to derive them. Though we may not be asked on an exam how to derive a equation, understanding where an equation comes from will help you know how and when to use it.
by Ashley Macabasco 2K
Sun Feb 04, 2018 1:52 am
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: 4
Views: 179

Re: Residual Entropy

Residual entropy is a specific type of entropy and is the same as positional entropy in which the entropy is based upon the arrangement of molecules or atoms.
by Ashley Macabasco 2K
Sun Feb 04, 2018 1:44 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: entropy vs. Degeneracy
Replies: 4
Views: 197

Re: entropy vs. Degeneracy

Degeneracy (w) is used to calculate statistical entropy and refers to the number of combinations atoms or molecules can be in and create energy. Statistical entropy is therefore dependent on w as it shows the different ways positional entropy can occur.
by Ashley Macabasco 2K
Sun Feb 04, 2018 1:33 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Isothermal pressure change
Replies: 3
Views: 108

Re: Isothermal pressure change

The change in pressure equation is P1/P2 opposed to P2/P1 like for the change in temperature and the change in volume because of Boyle's law in which volume and pressure are inversely proportional.
by Ashley Macabasco 2K
Sat Jan 27, 2018 11:25 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Question 8.31
Replies: 7
Views: 324

Re: Question 8.31

The temperature change could be calculated either way using Kelvin or Celsius because regardless of which unit you use, the difference between the two temperatures will be the same.
by Ashley Macabasco 2K
Sat Jan 27, 2018 11:15 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: CV or CP
Replies: 5
Views: 200

Re: CV or CP

Cv is used when a reaction is occurring at a constant volume and Cp is used when a reaction is occurring at a constant pressure.
by Ashley Macabasco 2K
Sat Jan 27, 2018 10:47 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Ideal Behavior
Replies: 3
Views: 151

Re: Ideal Behavior

The term "ideal behavior" simply means that the gas is acting like an ideal gas and would follow the ideal gas equations (PV=nRT).
by Ashley Macabasco 2K
Sat Jan 20, 2018 4:47 pm
Forum: Phase Changes & Related Calculations
Topic: HW #1 PART E
Replies: 3
Views: 165

Re: HW #1 PART E

Mercury in a thermometer is an example of a closed system because the mercury itself is unable to leave the thermometer, but its energy is able to be exchanged with its surroundings (energy seen as heat). The transfer of heat is what makes the mercury leave in a thermometer rise or drop with heat ca...
by Ashley Macabasco 2K
Thu Jan 18, 2018 12:09 pm
Forum: Phase Changes & Related Calculations
Topic: Question about Problem 8.41
Replies: 5
Views: 221

Re: Question about Problem 8.41

In the solution manual -q(water)=q(ice) illustrates that heat from water is being transferred exothermically to the ice shown with the lose of heat (-q). The ice is then gaining heat endothermically from the water which can also be seen with q being positive for ice.
by Ashley Macabasco 2K
Thu Jan 18, 2018 12:03 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: the sign of q and w [ENDORSED]
Replies: 6
Views: 232

Re: the sign of q and w [ENDORSED]

In the equation ΔU= q+w both q and w are positive to show that the change in internal energy consists of both the transfer of heat and the transfer of work in a closed system. Because the heat transfer may be negative (due to the system losing heat) or positive (due to the system gaining heat), q ca...
by Ashley Macabasco 2K
Fri Jan 12, 2018 7:28 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.73.b
Replies: 3
Views: 140

Re: 8.73.b

I believe that 4 moles are broken in the C-H bond because there are four hydrogens bonded to one carbon in CH4 (lewis structure) so there are four C-H bonds and not one C-H bond. There are 4 moles of the H-Cl bond formed because of the 4 coefficient in "4 HCl" indicating that four H-Cl bon...
by Ashley Macabasco 2K
Thu Jan 11, 2018 5:07 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.59
Replies: 2
Views: 109

8.59

For Hess's law, do you only add the enthalpy changes of the same phase to find the standard reaction enthalpy? For example in question 8.59 to calculate the standard reaction enthalpy of 4HNO3(l) + 5N2H4(l) ---> 7N2(g) + 12H2O(l), nitrogen is not included in finding the standard reaction enthalpy an...
by Ashley Macabasco 2K
Tue Jan 09, 2018 9:17 pm
Forum: Phase Changes & Related Calculations
Topic: Endothermic Reaction
Replies: 10
Views: 985

Re: Endothermic Reaction

An ice cube melting is an endothermic reaction because the ice cube must take in heat in order to begin melting. It is endothermic because heat must go into the ice cube ("en"dothermic - "in"to the ice cube) instead of the ice cube emanate heat which would be an exothermic reacti...

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