Search found 30 matches
- Thu Mar 15, 2018 2:01 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: k' reverse reaction constant
- Replies: 6
- Views: 1103
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].
- Thu Mar 15, 2018 1:50 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: 14.17?
- Replies: 2
- Views: 423
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.
- Thu Mar 15, 2018 1:47 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Delta Hc
- Replies: 1
- Views: 1719
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...
- 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: 763
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.
- Thu Mar 08, 2018 8:03 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Intermediate [ENDORSED]
- Replies: 7
- Views: 924
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.
- Thu Mar 08, 2018 8:01 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: to find k
- Replies: 4
- Views: 648
Re: to find k
From my knowledge and the homework problems, k seems to be the same throughout experimental data regardless of the concentrations.
- Wed Feb 28, 2018 10:48 am
- Forum: Balancing Redox Reactions
- Topic: Balancing number of electrons
- Replies: 10
- Views: 1106
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.
- Tue Feb 27, 2018 9:06 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell diagram order
- Replies: 4
- Views: 492
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.
- Tue Feb 27, 2018 9:05 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Cell Potential
- Replies: 9
- Views: 3261
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.
- Fri Feb 23, 2018 1:08 am
- Forum: Balancing Redox Reactions
- Topic: Cell Diagram [ENDORSED]
- Replies: 7
- Views: 888
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.
- 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: 726
Re: 14.31
If E(cathode)>E(anode) then K>1 and products are favored.
- Fri Feb 23, 2018 1:02 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell diagram
- Replies: 4
- Views: 579
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.
- Sun Feb 18, 2018 4:01 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: reversible system
- Replies: 9
- Views: 1205
Re: reversible system
For a reversible system, delta S total would equal zero.
- Sat Feb 17, 2018 2:25 pm
- Forum: Balancing Redox Reactions
- Topic: Oxidizing vs. Reducing Agent
- Replies: 7
- Views: 869
Re: Oxidizing vs. Reducing Agent
An oxidizing agent gains electrons which can be seen through a half-reaction. The reducing agent then loses electrons.
- Sat Feb 17, 2018 2:20 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: s vs. delta s
- Replies: 7
- Views: 1733
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.
- Sat Feb 10, 2018 4:12 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: When to use + sign
- Replies: 11
- Views: 1072
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.
- Sat Feb 10, 2018 4:02 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: 8.101 (c) and (f)
- Replies: 3
- Views: 556
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.
- Sat Feb 10, 2018 12:27 pm
- Forum: Van't Hoff Equation
- Topic: Derivation
- Replies: 9
- Views: 1270
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.
- 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: 607
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.
- Sun Feb 04, 2018 1:44 am
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: entropy vs. Degeneracy
- Replies: 4
- Views: 580
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.
- Sun Feb 04, 2018 1:33 am
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Isothermal pressure change
- Replies: 3
- Views: 355
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.
- Sat Jan 27, 2018 11:25 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Question 8.31
- Replies: 7
- Views: 1048
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.
- Sat Jan 27, 2018 11:15 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: CV or CP
- Replies: 5
- Views: 651
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.
- Sat Jan 27, 2018 10:47 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Ideal Behavior
- Replies: 3
- Views: 411
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).
- Sat Jan 20, 2018 4:47 pm
- Forum: Phase Changes & Related Calculations
- Topic: HW #1 PART E
- Replies: 3
- Views: 524
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...
- Thu Jan 18, 2018 12:09 pm
- Forum: Phase Changes & Related Calculations
- Topic: Question about Problem 8.41
- Replies: 5
- Views: 622
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.
- 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: 2211
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...
- 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: 383
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...
- 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: 258
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...
- Tue Jan 09, 2018 9:17 pm
- Forum: Phase Changes & Related Calculations
- Topic: Endothermic Reaction
- Replies: 10
- Views: 9589
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...